ASME Conference Presenter Attendance Policy and Archival Proceedings

2013;():V02AT00A001. doi:10.1115/IMECE2013-NS2A.

This online compilation of papers from the ASME 2013 International Mechanical Engineering Congress and Exposition (IMECE2013) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Additive Manufacturing

2013;():V02AT02A001. doi:10.1115/IMECE2013-62142.

Laser Powder Deposition (LPD) is an additive manufacturing process used for solid freeform fabrication, surface modification, and part repair or remanufacture. This technology offers some significant advantages over traditional manufacturing processes, such as reduced post-process machining and reduced material waste. Most importantly, LPD offers increased flexibility in order to meet the demands of diverse markets. However, the connection between deposition parameters, thermal gradients, and final part quality is not sufficiently understood. The research discussed here shows how radiometric temperature measurements provide insight into the connection between process parameters and final part quality. These measurements can be used to augment the research and development process while maintaining process flexibility. Radiometric thermal data was collected during the deposition of ASTM/SAE 1045, 4130, and 4140 steel thin-wall samples. Several thermal zones were identified by radiometric analysis, and compared to post-process metallographic and dimensional inspection.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A002. doi:10.1115/IMECE2013-62847.

Investment casting processes are influenced by a variety of parameters. Many researches considering viscosity as a constant have been conducted up to this point. In particular, however, viscosity with temperature change has not been much accounted for solidification and heat transfer simulation of molten metal in the investment casting process. In addition, analysis of behavior of metal flow as well as air gap problems for complex network structures have not been investigated much. The aim of this study is to build transient metal flow and velocity profile models considering temperature dependent viscosity in investment casting processes of cellular structures. In this study, a Computational Fluid Dynamics (CFD) modeling tool was used for metal flow and velocity profile in investment casting processing using User Defined Function (UDF) for temperature dependent viscosity. The results of the metal flow and velocity profile inside of the simple cylindrical geometry are represented. It is shown that for the validation of the numerical simulation, the velocity profile between analytical and numerical approaches showed very good agreement. Analytical approaches showed that velocity was reduced with the increase in viscosity, which is applied as a function of temperature. In particular, rapid decreasing in velocity was shown from under the melting temperature of the molten metal. There was no movement on metal flow at the room temperature. Numerical approaches showed that the liquid metal began to be solidified from the wall surface inside of the mold. For the same simulation time, it was shown that the metal flow in a cylinder that has 1mm diameter showed better fluidity rather than that of the cylinder that has 2mm diameter due to the increase in adhesion between liquid metal and the surface of the mold and surface tension between molten metal and air. The effective diameter by solidification is decreased with the time change.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A003. doi:10.1115/IMECE2013-62866.

The demand for multifunctional micro parts is an ever increasing need for product miniaturization. Amongst the spectrum of micro manufacturing processes, Electro-Discharge Deposition (EDD) is a newly developing additive process to produce parts in micro scale. In EDD the tool and workpiece electrodes are connected to reverse polarity in order to remove material from anode which deposits on cathode surface. The advantage of EDD is, any conducting tool material can be deposited irrespective of its hardness on the specified conducting substrate. So far, limited work has been carried out to develop micro parts like micro cylinders, micro spiral structures, etc., by EDD. In this work an attempt has been made to study the effect of various process parameters like current, duty cycle, pulse on time, voltage and table feed rate in EDD using central composite rotatable design (CCRD). It is found from the experimental results that, current plays a significant role in deposition of tool material.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A004. doi:10.1115/IMECE2013-63064.

A resistance based conformal, compliant multi-layer tactile sensor was designed and built layer by layer using a hybrid manufacturing process. A highly stretchable, photocurable, piezoresistive sensing material was deposited on a conformal, soft molded structure using a direct printing device. The principle of the sensor is based on detecting the changes in resistance as it is deformed. The fabricated tactile sensor consists of two layers of sensing elements within the 3D skin structure where the sensing elements in the top layer are orthogonally placed atop the bottom layer. Due to the multiple layers of wires, the sensor can potentially detect various external forces/motions in two and/or three dimensions. Piezoresistivity and conductivity was introduced into the nonconductive stretchable prepolymer through dispersion of multi-walled carbon nanotubes (MWNTs). Experiments were performed to characterize the ability of the sensor to detect the location that forces were applied to the surface. Finally, it is expected that the developed conformal tactile sensor using the hybrid manufacturing method and materials could be used for various robotics and electronics applications.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A005. doi:10.1115/IMECE2013-63068.

3D structural electronics is a new paradigm in fabricating electronics with high design complexity. Basically, manufacturing of 3D structural electronics consists of several processes: structure building, wire creation, and pick-and-place of electrical components. In this work, a 3D structure was built in a commercial AM machine, and conductive wires were created on the 3D structure with a predetermined design of an electronic circuit. Generally, 2D wire paths are projected to a 3D surface, and a tool path for the wire is generated in advance. And a direct printing device follows the tool path to draw the conductive wires on the surface, while a direct curing device simultaneously hardens the created wires using thermal/radiation energy. This direct printing/curing device was developed by combining a micro-dispensing device and a light focusing module installed in a motorized xyz stage. Several experiments were accomplished using photocrosslinkable materials filled with carbon nanotubes (CNTs). Finally, a 3D electronics prototype was fabricated to show the compelling evidence that the suggested manufacturing methods and materials would be promising in manufacturing 3D structural electronics.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A006. doi:10.1115/IMECE2013-63152.

Fabrication of plastic parts is an important scope of application for various branches of industry. This does not only concern manufacturing of end products but also production of sample parts in small lot sizes. Currently, most plastic parts are injection-molded. Consequently, it is first necessary to produce appropiate moldings, for example by milling of metal. This is very time-consuming on one hand and uneconomical concerning costs for production in small lot sizes on the other hand. Furthermore, the variety of forms is restricted considerably which is a clear disadvantage concerning the production of prototypes or spare parts. The use of a free-forming droplet generator for producing plastic parts can provide remedy.

The patented principle of the printing process used in this approach is to produce droplets of liquified plastic in a preparation unit. Sequential discharge of these droplets builds a part in the installation space by solidifying of the droplets into balls. Since each 3D printing process needs its own data preprocessing, this article presents its fundamentals. STL data is used as input data and allows almost any kind of geometry. In general, a typical workflow for processing STL data is as follows: slicing volume data in order to gain contours that form 2D boarders, offsetting contours for a true to scale building process, filling of slices dependent on (offset) contours and generation of machine-code (g-code) that can be executed by the 3D printer in order to build an accurate and high-quality part.

The model used in this approach is based on the droplets produced by the machine. A more detailed description of all the process-specific invidual steps from slicing up to g-code generation is presented within the scope of this paper. The continual development of custom-made algorithms based on process-specific models and parameters has resulted in the generation of g-code that could be executed on a 3D plastic polymer printer based on droplet generation for the first time. The resulting sample parts are very appealing.

In conclusion, the results have shown that the whole production process can be a significant benefit especially for rapid prototyping of sample parts or spare parts.

Topics: Drops , Polymers , Printing
Commentary by Dr. Valentin Fuster
2013;():V02AT02A007. doi:10.1115/IMECE2013-63996.

This research explores mega-scale additive manufacturing, using fresh concrete. In traditional concreting, rigid forms mold and protect young concrete, like an exoskeleton. Typically, these forms are not removed until the maturing material has developed considerable load-bearing strength. Conversely, Contour Crafting, an automated construction technology under development at the University of Southern California, proposes to rapidly fabricate civil structures additively — layering continuous ribbons of fresh unconfined concrete. The process, which is akin to 3-D printing, leverages a special polymer-modified concrete which is both highly workable and shape–stable. However, without exoskeleton, the freshly layered concrete must be load-bearing immediately upon placement. This is an unprecedented structural requirement, and little has been done to substantiate uncured concrete as a load-bearing member. This research establishes the build rates and material health monitoring necessary to erect these structures safely, and demonstrates the Contour Crafting process is viable.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A008. doi:10.1115/IMECE2013-64334.

Selective Laser Melting (SLM) is a powder based Additive manufacturing (AM) technology which builds an object layer wise using a laser beam to melt the powder on an elevated platform. Thus far numerous studies have investigated lunar manufacturing methods and construction but little is known about applicability of SLM of lunar regolith. As most lunar construction proposals require transportation of essential materials from Earth, using an in-situ manufacturing method with indigenous material would be considerably more economical. Fabrication of parts with SLM using various metals and ceramics has already been presented. As such, the feasibility of using lunar regolith mixture to create functional parts with SLM process is investigated. Variation of process parameters such as laser power, scan speed, and scan strategies is investigated and multiple 3D objects are successfully created and presented.

Topics: Lasers , Melting
Commentary by Dr. Valentin Fuster
2013;():V02AT02A009. doi:10.1115/IMECE2013-64549.

Today different types of established rapid prototyping (RP) systems are available. In a Selective Laser Sintering (SLS)-process a CAD-model is designed and converted into a STL-file (Standard Tessellation Language). Next the body information is sliced into layers and transferred to the production system. By melting the powder-material using a laser beam, parts can be created layer by layer. Afterwards the parts are cleaned and several finishing treatments can be applied.

The primarily aim in using RP was to reduce the product development time and to create design models. Nowadays whole assemblies and complex parts can be produced altogether in one manufacturing step with RP-systems. To ensure a save part construction due to calculation formulas and basic material constants, predictable design calculations are necessary. Concerning SLS-materials like polyamide PA 2200 components, only specific mechanical values like the tensile and flexural modulus have been identified.

To fill this gap concerning tribological characteristics and to reach the next level of rapid manufacturing the key aspects of this article are the determination of the coefficient of friction μ0 of SLS-parts made of polyamide PA 2200 concerning several influence factors. An anisotropic material behavior, a decrease of the coefficient of friction μ0 with increasing contact pressure, larger contact areas and more intensive finishing treatment could be detected. Due to the knowledge of the identified material properties, now friction loaded components can be configured and used as functional machine parts.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A010. doi:10.1115/IMECE2013-64678.

Additive Manufacturing (AM) based Printed Electronics (PE) is an emerging technique where electronic components and interconnects are printed directly on substrates using a layered technique. The direct printing of the electronic components allows large scale and ultra-thin components to be printed on a wide variety of substrates including glass, silicon and plastic. These attributes make AM based Printed Electronics an invaluable manufacturing technique in the area of electronic sensors and sensor networks where thin, flexible and rugged form factors are very important. However, currently this technology is a labor intensive and manual process with the machine operator using his experience and judgment to slice the CAD file of the part to create 2D layers at different levels. This manual process increases the overall production time as well as the cost of the product and also results in inconsistent quality of parts.

A major challenge faced by existing AM based Printed Electronics users for automating this process is the lack of a standard input file format that can be used by different PE machines for producing the components in layers. To leverage the capabilities of both AM and PE processes, a new file format based on the Constructive Solid Geometry (CSG) technique is proposed in this research paper. This file format data will not only include CAD data in the form of CSG primitives and Boolean representation but will also include manufacturing information related to the AM based PE process. The manufacturing information embedded within this new format will include data about the location of the different electronic components such as interconnects, resistors, capacitors, inductors, transistors, memory and substrate, and the materials required for the different components part. Different circuit board components will be represented as primitives or a combination of primitives obtained using CSG technique. In addition to the new file format, a slicing algorithm will also be developed which can be used to create the layers automatically using user inputs. The proposed file format and the slicing algorithm will be explained with the help of a case study.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A011. doi:10.1115/IMECE2013-64696.

With the evolving of rapid manufacturing methods, new fields of application become feasible. Selective Laser Sintering (SLS), an additive process, allows the production of medical devices made out of PA 2200, a biocompatible plastic powder. Due to the fast production cycle, medical robots or devices can be highly customised. However, those new production methods force the engineer to design robots and mechanisms adapted for this process. In particular the use of compliant structures is necessary if small mechanisms are to be created.

Creating laparoscopic grippers out of flexible hinges revealed that there are properties unknown for the particular material used. Lasersintered PA 2200 parts seem to have a flexural modulus, which varies with their thickness and build orientation during the production process. This paper investigates those phenomenons with three-point loading tests. A dependency could be found and has been characterised for five orientations allowing the engineer to estimate the flexural modulus of lasersintered PA 2200 parts according to their thickness.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A012. doi:10.1115/IMECE2013-65042.

Recently Additive Manufacturing (AM) has been hailed as the “third industrial revolution” by The Economist magazine [April-2012]. Precision of the product manufactured by AM largely depends on the on line process diagnostics and control. AM caters to the quest for a material to suit the service performance, which is almost as old as the human civilization. An enabling technology which can build, repair or reconfigure components layer by layer or even pixel by pixel with appropriate materials to match the performance will enhance the productivity and thus reduce energy consumption. With the globalization, “Economic Space” for an organization is now spreads all across the globe. The promise of AM for Global Platform for precision additive manufacturing largely depends on the speed and accuracy of in-situ optical diagnostics and its capability to integrate with the process control. The two main groups of AM are powder bed (e.g. Laser Sintering) and pneumatically delivered powder (e.g. Direct Metal Deposition [DMD]) to fabricate components. DMD has closed loop capability, which enables better dimension and thermal cycle control. This enables one to deposit different material at different pixels with a given height directly from a CAD drawing. The feed back loop also controls the thermal cycle. New optical Sensors are either developed or being developed to control geometry using imaging, cooling rate by monitoring temperature, microstructure, temperature and composition using optical spectra. Ultimately these sensors will enable one to “Certify as you Build”. Flexibility of the process is enormous and essentially it is an enabling technology to materialize many a design. Several cases will be discussed to demonstrate the additional capabilities possible with the new sensors. Conceptually one can seat in Singapore and fabricate in Shanghai. Such systems will be a natural choice for a Global “Economic Space”.

Topics: Metals
Commentary by Dr. Valentin Fuster
2013;():V02AT02A013. doi:10.1115/IMECE2013-65253.

Build direction in additive manufacturing is mostly determined considering the time, support materials and surface finish of the fabricated part. However, internal architecture of the part cannot be ignored in porous functional object design. Especially, heterogeneous object with internal features can be decomposed into 2D heterogeneous slices with island in which each island represent associated feature’s properties different from the base. Continuous material deposition in such multi-feature/multi-contour slices can be intervened by frequent directional changes intersecting those islands and can affect the build time and part quality. This research aims to minimize such intervention in the decomposed slices of heterogeneous object. A computational algorithm is proposed to quantify the build direction considering the location and alignment of the internal feature which can maximize the homogeneous slices generated from a heterogeneous object. The proposed methodology is illustrated by an example in this work. The algorithm can provide better control over the internal architecture design by selecting the best build direction for the heterogeneous object.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A014. doi:10.1115/IMECE2013-65426.

This paper describes how direct digital manufacturing mechanical properties can be analytically estimated for structural use and the associated analytical and test methods used in the design and fabrication of airframes manufactured using additive manufacturing. Complex shape structures, which are now possible using additive manufacturing, and their associated mechanical properties can be predicted in order to allow operationally safe and highly predictive structures to be fabricated. Direct digital manufacturing allows for much greater flexibility and control over the design of airframes, leading to more structurally efficient and capable airframes. These advantages are revealed by application of direct digital manufacturing methods on a series of fixed wing subsonic transport concept wind tunnel scale models that are carried out as a part of the NASA N+3 program, which is paving the way for next generation aircraft that are highly fuel efficient, low-noise, and low-emission. Verification of these methods through test shows excellent correlation that provides reliability in complex sparse filled additive manufacturing design. The outcome of this is a knowledge base, which can then be applied to a system in operation. The combined potential of a flexible manufacturing system and proven predictive analysis tools shorten development time and expand the opportunities for mass customization. These combined benefits enable industry to fabricate affordable highly optimized custom products while concurrently reducing the cycle times required to field new products.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A015. doi:10.1115/IMECE2013-65688.

Market pressures on manufacturing enterprises incentivize minimum resource consumption while maintaining part quality. Facilities with advanced manufacturing tools often utilize rapid prototyping for production of complicated or specialty parts. Additive manufacturing offers an alternative to traditional production methods which are often time and resource expensive. This study aims to explore part quality and energy usage for additive manufacturing through a focused study of Fused Deposition Modeling and Photopolymer Jetting technologies. A control part is developed for maintaining test consistency across different machines. The control part design consists of various positive and negative features including width varied slots and walls, ramps, and curved features so that the manufacturing of different surfaces may be investigated. Several different machine models are tested to evaluate precision for a variety of applications. Part quality is quantified by measuring the surface roughness in two directions for the control test part printed on each machine. Qualitatively, part quality is assessed by positive and negative feature resolution. High quality machines resolve features closely to design specifications. Lower quality machines do not resolve some features. In addition to exploring the effects of advertised print precision, layup density is varied on two machines. Advertised print resolution does not well represent the achievable feature sizes found in this study. Energy usage is quantified by measuring electricity demands while printing the control part on each of the five different machines. Power consumption in additive manufacturing is found to follow a distinct pattern comprised of standby, warm up, printing and idle phases. Measurement and analysis suggest a relationship between the precision of these machines and their respective energy demand. Part quality is found to generally improve with increased initial and process resource investment. The energy and quality assessment methods developed in this study are applicable to a greater variety of additive manufacturing technologies and will assist designers as additive manufacturing becomes more production friendly. The presented data also provides designers and production planners insight for improvements in the process decision making.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A016. doi:10.1115/IMECE2013-65720.

Additive manufacturing (AM) process is widely used in fabricating three-dimensional (3D) models with complex internal features due to its flexibility and fast building speed. Inspired by the recent development of origami structures, we investigate a super-fast AM process for fabricating prototype models of hollow shapes. By combining the origami design and the additive manufacturing technology, a new fabrication process named Assembled Additive Manufacturing (AAM) is developed. A folding technique is used either during or after the layer-based fabrication process. By turning a 3D structure into a foldable two-dimensional (2D) structure, the fabrication speed is dramatically increased due to the decreased number of layers that is required in the building process. Detailed procedures of the AAM process such as unfolding algorithms of an input model, foldable structure design and folding mechanism are introduced in the paper. Experimental tests are also presented to illustrate the effective and efficiency of the AAM process.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A017. doi:10.1115/IMECE2013-66009.

Powder-based electron beam additive manufacturing (EBAM) is capable of making full-density metallic parts and has been increasingly utilized to produce complex-shaped, custom-designed Ti-6Al-4V alloy parts. EBAM also has the potential using other various powders materials such as intermetallics. Different materials will have different thermal properties that will result in distinct thermal responses during the EBAM process and thus, selecting adequate process parameters can be challenging. Because virtually all thermal properties would change when a different material was selected, testing individual thermal property is insufficient to understand the anticipated thermal response when a different powder material is to be used.

In this study, EBAM process thermal simulations were extended to study the effect of thermal properties in EBAM in a more systematic way using the design of experiments approach. Four factors, two levels, and full factorial experiments were conducted. Three simulation response of melt pool geometry was evaluated using analysis of variance (ANOVA). It is concluded that the thermal conductivity and the melting temperature are the two most significant factors.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A018. doi:10.1115/IMECE2013-66329.

Dimensional quality control is critical for wider adoption of Additive Manufacturing (AM) as a direct manufacturing technology. Due to the process’ complex physics, AM-fabricated parts still require post-processing with machine tools, which significantly negates its time and cost benefits. In this paper, we investigate product shape deviation for Mask Image Projection Stereolithography (MIP-SLA) — one of the earliest commercialized AM techniques. By studying part fabrication mechanisms, we consider (i) over or under exposure, (ii) light blurring and (iii) phase change induced shrinkage or expansion as the most significant sources for shape deviations. Accordingly, the shape deviation modeling is established to quantify the effects of those influential factors and to understand the deviation mechanisms. Cylinders and cubes of various sizes were built to test our approach. Accurate prediction of shape deviation for all parts serves as a further confirmation of our model.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Advanced Forming

2013;():V02AT02A019. doi:10.1115/IMECE2013-62043.

Despite the advantages of advanced high strength steels (AHSS), their stamping into functional lightweight parts demands prolonged die life, which necessitates the use of alternative substrates, coating materials, and/or surface conditioning to minimize and delay the die wear. In order to avoid frequent die replacement and surface quality problems on the stamped parts, the metalworking industry has been investigating various approaches such as reducing/refining the carbide particles, adding alloying elements, and elevating the hardness and toughness values for both substrate materials and coatings.

The objective of this work was to investigate the effects of different coatings on the wear behavior of a some selected tool steel materials (die sample of interest) against two different AHSS sheet blanks through a cylinder-on-flat type reciprocating test method. After wear tests, both die sample and sheet blank surface were microscopically examined. Wear resistance of the slider was quantified from wear scar width measurements. Results showed that TD and CVD coated die samples performed better than the two other PVD coated samples.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A020. doi:10.1115/IMECE2013-62458.

Micro-electrical discharge machining (EDM) milling with a simple-shaped electrode is an effective machining method to fabricate three-dimensional micro parts and micro structures. However, the serious electrode wear occurring in the machining process significantly deteriorates the geometrical accuracy of the products. Fix-length compensation method is a real-time and effective electrode compensation method. During the EDM process with fix-length compensation, the bottom of cylindrical electrode trends to be conical shape. The formation process of conical electrode is illustrated by experiments and analysis. Once the cone angle of the electrode is formed, the angle of conical electrode keeps stable. Further experiments reveal the relationship between the cone angle and the layer thickness. The experiment results are in accordance with theoretical results, which provide theoretical reference for ED-milling compensation. The wear model based on fix-length compensation method with conical electrode is established and the corresponding arithmetic of compensation length is derived. Experiments show that the arithmetic equation about compensation length has high accuracy. A demonstration cavity is machined with this compensation method. The effectiveness of this compensation method is verified.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A021. doi:10.1115/IMECE2013-62582.

Servo press has the ability to improve the formability, quality, and productivity of metal products by working with various forming curves of slide. However, the operations of free-motion function are not very intuitional and efficient for most of servo presses so that it is difficult for operator to construct self-design forming curves. This article proposed a control system design of servo mechanical press which consists of an open-system controller and a real-time operating system to provide a convenient and efficient approach for operating free-motion function. In the proposed control system, operators determine the motion of slide by adjusting several control points of forming curve in a friendly and graphical interface. Then a calculating process based on the B-spline and curve fitting theories is applied in the controller to transform settings of operator into speed commands of servo motor automatically. Through this process, the controller is capable of driving servo motor smoothly and generating an expectant forming curve. In the latter section, some compare and analyses of setting of operator and actual results are demonstrated to verify the performance of proposed control system. By applying the proposed control system design to servo mechanical press, operators are able to create practical and satisfying forming curves more easily.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A022. doi:10.1115/IMECE2013-62892.

This paper aimed to present the methods to improve the forming accuracy for water jet incremental sheet metal forming. The study focuses on the process parameters and the forming accuracy based on the experiments. Firstly, some experiments was carried out to evaluate the deformation effect of sheet metal in water jet incremental sheet metal forming process with respect to some key parameters, such as water jet pressure and feed velocity. Then, the influence of layer on deformation was analyzed, and the theoretical model of forming accuracy and two methods to improve the forming accuracy were presented. Finally, the circular truncated cone parts formed with different methods and the profiles were measured with a coordinate measuring machine. Compared with the designed model geometry, the experimental results showed that an achievable forming accuracy could be obtained by the presented two methods.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A023. doi:10.1115/IMECE2013-63075.

Twist extrusion is a severe plastic deformation in which the rectangular shaped work piece is extruded through a die with a twist channel. In this work the twist extrusion process of AA6082 T6 aluminum samples were carried out to investigate the effects of process parameters like temperature and deformation passes on the microstructure homogeneity. The results indicate that the grain refinement of AA 6082 T6 aluminum alloy leads to inhomogeneous microstructure after one twist extrusion pass. On further extrusion passes the inhomogeneity in the microstructure is found to be disappeared. The homogeneity of the distribution of the deformation was confirmed by micro hardness testing. Finite element modeling has been performed in DEFORM 3D software for determining the homogeneity of the effective strain distribution which agreed well with the experimental values.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A024. doi:10.1115/IMECE2013-63175.

Lightweight design in passenger cars is gaining more and more importance. Independent from conventionally or electrically drive train concepts, weight reduction is one of the most rated defining variables for fuel or energy consumption, thus affecting the range of the vehicle. Overall, the potential for using steel in lightweight bodywork construction has attained a high level of development with the result that the potential for further optimisation is increasingly diminishing. As a consequence, alternative lightweight construction materials are set to become more important in the future.

Compared to the beneficial application potential regarding bending and distortion of steel- and Aluminium compared to Magnesium blanks, this material becomes more and more interesting for automobile applications.

Beside challenges like corrosion and recycling, mainly an appropriate forming technology lies in the focus of investigations. Due to the insufficient forming conditions of Magnesium at room temperature the focus of investigation was related to the characterisation of material properties depending on temperature, the thermo-mechanical forming simulation for process and tool design and the practical realisation of complex, car-related part geometries as well as requirements for forming tools and additional devices.

In the following article we will present the results of studies into the forming of magnesium sheets (AZ31) including tailored blanks, achieved within a growth cell (TeMaK and TeMaK+).

Commentary by Dr. Valentin Fuster
2013;():V02AT02A025. doi:10.1115/IMECE2013-63213.

Zinc-based Electrogalvanized (EG) and Electrogalvanized zinc-iron alloy (EGA) coatings have been widely used in automotive body-in-white components for corrosion protection. The formability of zinc coated sheet steels depends on the properties of the sheet and the interactions at the interface between the sheet and the tooling. The frictional behavior of zinc coated sheet steels is influenced by the interfacial conditions present during the forming operation. Previous studies showed that the EG coated steel tended to have a lower friction coefficient than the EGA coated steel in the laboratory tests. However, the opposite trend is sometimes seen in production. The objective of this study is to evaluate the friction differences of these two coated sheet metals using laboratory simulative tests similar to production conditions. Process variables such as forming speed, lubricant composition, temperature, interface pressure, and die material are evaluated using the Bending Under Tension (BUT) test, the Draw Bead Simulator test (DBS) and the Strip Draw (SD) test. The results revealed that the friction behavior of the EGA coated sheet steel tends to be less sensitive to the lubricant amount supplied in forming. The EG coated sheet steel usually delivers a lower friction coefficient than the EGA coated sheet steel. However, the trend reverses when the sheet metal is tested in the bending and unbending mode at a lower speed under a well lubricated condition.

Topics: Friction , Steel
Commentary by Dr. Valentin Fuster
2013;():V02AT02A026. doi:10.1115/IMECE2013-63294.

Mecano-welding can efficiently produce cylinders used in various industries. The pyramidal three-roll bending process is commonly used to produce a cylinder with non-seamed gap. However, there is a planar zone near the front and rear ends. This planar zone can be seamed with a welding process. In this paper, a numerical model is proposed to simulate the roll bending process and the welding process so that the geometrical quality of the bent cylinders can be improved. Explicit and implicit solvers are applied to the numerical modeling by using ANSYS/LS-DYNA software. The numerical model can provide a useful tool for design and optimization of the Mecano-welding process.

Topics: Cylinders
Commentary by Dr. Valentin Fuster
2013;():V02AT02A027. doi:10.1115/IMECE2013-63307.

Acoustic or electromagnetic shaping in resonators can form thin walled structures from pulverized materials. The technology is applicable to a wide variety of materials, particle shapes, and sizes. While radiation force models adequately capture the transport of particles towards the nodal surfaces where walls form, the actual wall formation process involves complex particle-field and interparticle forces. A finite element computation is used along with pulsed laser particle image velocimetry for air movement, and particle tracking velocimetry for particle movement, to close the gap between predictions and measurements. Non-intrusive force measurement is attempted by deriving the acceleration field of particles, from velocity field data. Results are compared with particle acceleration computed from velocity calculations using the finite element code. The predicted acoustic velocity field from the standing wave pattern in the resonator, is compared with measurements. The difference between the computed particle velocity and the acoustic velocity is used to assess the relative roles of fluid dynamic drag and radiation forces on the acceleration of the particles. The measured particle acceleration does differ substantially and consistently from the computed values, showing the effect of the unmodeled near-field particle-field interaction forces.

Topics: Acoustics
Commentary by Dr. Valentin Fuster
2013;():V02AT02A028. doi:10.1115/IMECE2013-63433.

The sheet metal forming of copper, aluminum alloys using conventional stamping processes posses various problems, because of the lower formability limits, spring back and the tendency to wrinkle compared to steel. The principle of electromagnetism using attractive force is adopted to modify the conventional stamping process, to form thin sheets of 0.05 mm thickness. Further, this process can be used to form many sheet metal components with less expensive tooling and lesser number of operations. This process ultimately leads to light weight, cost effective and better strength-to-weight ratio components required for aerospace applications. In this study, a maximum of 30.77 % reduction in diameter was observed at 2.75A using electromagnetic forming which leads to the absence of spring back.

Topics: Copper
Commentary by Dr. Valentin Fuster
2013;():V02AT02A029. doi:10.1115/IMECE2013-63435.

Rapidly changing product design and specifications to meet highly dynamic customer requirements demands flexibility in manufacturing, in contrast to the rigid, automated manufacturing. Concept of lean manufacturing for small batch production is gaining momentum. Application of CNC machines find wide acceptance. Therefore, the profile forming technique that caters to rapidly changing product specifications with increasing need for productivity, flexibility and quality requirements can be a promising solution. This paper presents the forming process demonstrating the formation of the sheet metal part using computer coordinated hemispherical tool. The statistical method of analysis based on the design of experiments (DOE) and response surface has been used to evaluate the optimum conditions of the formability of an Aluminium sheet. The parameters considered for the experiments are tool size, step size, spindle speed and feed rate. The Process performance indicators are the surface finish, wall angle, and average thickness of profile part. An empirical model has been created for predicting the indicators through response surface methodology (RSM). The influence of the different parameters and their interactions are studied in detail.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A030. doi:10.1115/IMECE2013-64408.

Next-generation patterning processes have been extensively studied recently, with a view to replacing the photo-lithographic process and to reducing production costs. For micron scale patterning, the printing process is one of major candidates. In particular, contact printing is more promising in view of the possibilities for mass production. In this process, the motion of the two printing contact surfaces should be synchronized perfectly to prevent slip and unwanted distortion in the surfaces and to make precise ink transfer between the surfaces. In this article, a force-based direct measurement method of the synchronization error is proposed, and the effect of synchronization error on the printing process is analyzed.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A031. doi:10.1115/IMECE2013-64668.

Micro transfer printing is rapidly emerging as an effective method for heterogeneous materials integration. It transfers prefabricated micro- and nanoscale structures referred to as ‘inks’, from growth or fabrication donor substrates to functional receiver substrates. Laser Micro Transfer Printing (LMTP) is a laser-driven version of the micro transfer printing process, developed at the University of Illinois to enable non-contact release of the microstructure, thus making the transfer printing process independent of the properties or preparation of the receiving substrate. In this paper, an extensive study is conducted to investigate the capability of the LMTP process. Using square shaped silicon inks and polydimethylsiloxane (PDMS) stamps, and varying the lateral dimensions and thickness of the ink, the power absorption by the ink is measured to estimate the total energy stored in the ink-stamp system to initiate and propagate delamination at the interface. The delamination time for each size and thickness is experimentally observed at different laser beam powers using a high speed camera. Further, an axisymmetric thermo-mechanical FEM is developed to estimate the delamination temperatures at the interface utilizing the delamination time and power absorption for different ink sizes and thickness.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A032. doi:10.1115/IMECE2013-65903.

For certain applications, the welding of dissimilar metals is highly desired, e.g. an automotive shaft assembly with both steel and Aluminum components, so that material properties can be tailored to specific locations within the assembly where required. Fusion welding cannot be used in such applications due to the disparity of the material properties involved and the concern of cracking due to intermetallic phases. Electromagnetic welding is a solid-state process where a capacitor bank is charged and then quickly dissipated into a magnetic coil. Eddy currents in the workpiece are created which repel the material from the coil at a high velocity, on the order of 200–300 m/sec. At a critical velocity, the impact energy welds the two components together. In this paper, an analytical model to predict workpiece velocities, which is attractive for its simplicity and cost, is presented and compared to experimental data. The model focuses on a Uniform Pressure Actuator [1], which accelerates sheet metal workpieces. In addition, magnetic effects of workpiece thickness are evaluated.

Topics: Pressure , Actuators
Commentary by Dr. Valentin Fuster
2013;():V02AT02A033. doi:10.1115/IMECE2013-66373.

A technique was successfully developed to measure large tensile, compressive strains, springback and strain reversal effects on sheet metal bent to small radii. Vertical Scanning Interferometry (VSI) was used to measure three dimensional data from surfaces with sides varying from 160 nm to 2 mm. Software algorithms were utilized to determine surface topography maps from three-dimensional curved locations and to represent them in a two dimensional plane. Fine reference marks were engraved on both sides of sample. The sample was bent /unbent to small radii under a pure bending moment. Outer strains were calculated from VSI two-dimensional measurements of the original and final lengths between the reference marks. Strain gages, applied at locations close to the reference marks, gave additional information at the elasto-plastic range. Experimental data collected included bending moment as a function of strain, 3-D curvature profiles, springback and reverse bending effects. The technique was proved useful for the experimental evaluation and theoretical validation of bending and springback properties of sheet metal. Experimental results for aluminum and steel alloys are presented.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A034. doi:10.1115/IMECE2013-66607.

Conventional electronics manufacturing strategies are generally complicated, time, water, material and energy consuming. Besides, building an electronic device on a complex object generally requests a series of different connecting wires which would make the machine in a mess. Here from an alternative approach, we proposed an innovative method of realizing conformable electronic connection by the low melting point metal ink and the related flexible packaging material for quickly manufacturing electronics. The liquid metal ink could easily and directly be written on a series of complex surfaces and then coated with the packaging material which is to offer mechanical strength and prevent it from air oxygenization. For illustrating purpose, an electrical connection of LED circuit on cylindrical surface, concave, inclined structure, planes of right angle and sphere was demonstrated. Such optoelectronic device appears rather compact without any evident connecting wires exposing out. Further, a thermal cycle experiment (−40°C∼120°C) was designed to test the variation of the electrical properties of the working sample. It is disclosed that the conductive line covered by the packaging material has a temperature coefficient of 0.255 mΩ/°C (T0 = −16°C) and finally an increasing rate of only 4.24% in resistance after all thermal aging cycles. This electrical connection method is expected to have a significant impact in surface mount technology. Its applications will not only in industry but also can change the way we interact with each other and our everyday life.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Advanced Materials Design, Synthesis, and Processing

2013;():V02AT02A035. doi:10.1115/IMECE2013-62075.

Effect of heat treatment on the precipitation behavior of secondary phases in a HR3C austenitic heat resistant steel was investigated. The microstructure of the steel in solution-treated state consists of austenitic matrix and coarse Z-phase particles. After aging treatment at 650–950°C for 1h, M23C6-type carbide precipitates along random grain boundaries. Dense and homogeneous nanosized Z-phase precipitates within austenite grains are obtained by an aging treatment at a temperature between 800 and 900°C for 1h. The high density of dislocation walls produced during the water-cooling process after solution treatment facilitate the precipitation of the nanosized Z-phase. With increasing the aging temperature, the hardness initially drops, then increases and reaches a peak when the aging temperature is at 850°C due to the precipitation of the nanosized Z-phase.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A036. doi:10.1115/IMECE2013-62201.

One of the new methods of producing materials that have ultra-fine grains or grains of nanometer size is the method of severe plastic deformation (SPD). In this technique, by applying severe strains to the samples, the size of the grains is reduced to the nano scale, and as a result, the mechanical properties of the metal (including the yield strength and resistance to wear and abrasion) improve considerably. In this research, the effect of the constrained groove pressing process (as one of the SPD methods) on aluminum plates was studied. In this method, two dies (one with asymmetrical grooves, and the other, flat) were used for pressing the aluminum samples. With respect to the die’s geometry, at each pressing run, a shear strain equal to 0.58 is applied to some parts of the sample. By repeating the pressing operation, a large and significant amount of plastic strain is applied throughout the sample. In the present investigation, tensile and microhardness tests were employed to determine the effect of this process on the mechanical properties of the samples,. The results showed that, by increasing the number of pressing steps, hardness and strength of the samples increase, and the elongation ability diminishes. Of course, at higher numbers of pressing steps, a little decrease in strength was observed in the samples. Complete explanations regarding this decrease have been given in the text of the article.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A037. doi:10.1115/IMECE2013-62272.

New and innovative production equipment can be developed by introducing lightweight materials in modern day automotive industry production lines. The properties of these new materials are expected to result in improved ergonomics, energy savings, increased flexibility and more robust equipment, which in the end will result in enhanced productivity. Carbon composite materials are one such alternative that has excellent material properties. These properties are well documented, and the market for carbon composite materials is growing in many areas such as commercial aircrafts, sporting goods and wind turbines. However, when studying the use of carbon composite materials for production equipment in the automotive industry, it was found that there were few, if any, such examples.

This paper focuses on innovative ways of making carbon composite materials available for designing automotive industry production equipment by introducing a design and material concept that combines flexibility, relatively low costs and high functionality. By reducing the weight by 60%, it was obvious that the operators were very positive to the new design. But just as important as the improvement of the ergonomic feature, the combination of low weight and material properties resulted in a more robust design and a more stable process of operation. The two main designs (two versions of the steel-based design were constructed) were developed sequentially, making it difficult to compare development costs since knowledge migrated from one project to the next. In this study, the gripper was manufactured in both carbon composite material and steel. The different designs were compared with reference to design costs, functionality, robustness, product costs and ergonomics. The study clearly shows that the composite material represents a favorable alternative to conventional materials, as the system combines superior properties without significantly increasing the cost of the equipment. This paper describes the approach in detail.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A038. doi:10.1115/IMECE2013-63102.

This study examines the influence of different sub-zero processing routes on microstructure and mechanical properties of a cold work tool steel. Incorporation of controlled sub-zero processing cycle in between hardening and tempering treatment of tool steels increases the amount of ultrafine carbide particles with improved homogeneous distribution in addition to reduction in retained austenite content; these modifications are found to be enhanced with decreasing lowest temperature of the sub-zero processing cycle. It has been demonstrated that with reference to conventional heat treatment, sub-zero processing moderately improves hardness and marginally reduces fracture toughness but substantially enhances wear resistance of the selected steel; the extent of variations, in general, increase in the order of cold treatment, shallow cryogenic treatment and deep cryogenic treatment. The relationships of microstructural modifications with the variations of mechanical properties of tool steels due to different sub-zero processing have been established.

Topics: Steel
Commentary by Dr. Valentin Fuster
2013;():V02AT02A039. doi:10.1115/IMECE2013-63456.

As well known, Kyoto was a capital city of Japan with one thousand years history. The long ancient culture brings out a serious of traditional craft products, such as ‘Kana-ami’ — a kind of metal wire network. ‘Kana-ami’ was all made by hand work, for this reason there was no industrial pollution produced during the manufacturing process. In other words, ‘Kana-ami’ is a kind of green manufacturing product, whose processing motion and working experience make a big effect on final products’ quality. Product’s quality was judged by the standard structure of ‘Kana-ami’, which was established and developed in the long course of history and culture. That aesthetical standard has already been consistently rooted into Japanese peoples’ heart deeply. Dated back to around 50 years before, there were about 30 handmade wire net shops in Kyoto. However, it has decreased dramatic until 7 shops now. Therefore, it is urgent time to pay attention to this severe reality and try to do something to keep this traditional culture wealth and continue green manufacturing technique, skill to the next generation.

In this research, cooperating with ‘Kanaami Tsuji’ workshop, the excellent products of Mr.Tsuji and his son were chosen as the investigation subjects for Kana-ami’s structure comparison. As well known, ‘Kana-ami’ product made by Mr.Tsuji have already been widely accepted and preferred among Japanese people, even his son’s finish also has beautiful looking. Therefore, the main target of this study was to clarify the difference in shape and hexagon structure of ‘Kana-ami’ products made by Mr.Tsuji and his son through mathematical measurement. Based on this structure evaluation system, hexagon angles and length were discussed and analyzed in order to help his son and other beginners to inherit this Japanese traditional craft technology.

Topics: Metals , Wire
Commentary by Dr. Valentin Fuster
2013;():V02AT02A040. doi:10.1115/IMECE2013-63589.

Low pressure steam turbine (LPST) blades are made of martensitic stainless steel and Ti6Al4V alloy for the different ratings of steam turbines due to their high strength and toughness. These blade roots have a fir tree profile and experience severe stress concentrations all along their notched sections during turbine operation. The fatigue life of these blades can be increased by introducing compressive stresses either by shot peening or by laser peening. The present work deals with laser peening of these two materials to understand its effect on their fatigue properties, surface roughness and hardness. It is observed that laser peening has significantly enhanced fatigue life of Ti6Al4V alloy at 550 MPa stress as compared to the shot peened sample. The penetration depth of residual stress due to laser peening in the Ti6Al4V alloy was twice that due to shot peening. However, the fatigue life of steel was found to be similar for both the shot peened as well as laser peened samples. Similar response was observed from testing at lower stresses (400 MPa). Since the depth of penetration of compressive residual stresses for both the laser peened as well as the shot peened samples were similar for steels, it can be concluded that the fatigue life is a strong function of the penetration depth.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A041. doi:10.1115/IMECE2013-63735.

Quenching and Partitioning (Q&P) is a novel heat treatment process that is able to produce steels with a microstructure consisting of controlled amounts of finely divided retained austenite in a martensitic or ferritic-martensitic matrix. Following quenching to a temperature in the Ms-Mf range, the steel is subjected to partitioning treatment that concerns the diffusion of carbon atoms from supersaturated martensite phase to the austenite phase, resulting in the possibility of stabilizing it down to room temperature. Competing reactions such as cementite and/or transition carbide precipitation must be suppressed by suitably alloying with certain elements, conventionally silicon. In this study, aluminum was used as the main precipitation suppressor. Three Nb-microalloyed experimental steels with aluminum at different levels in the range 2–3%, with or without additions of Si, Ni and Cu were subjected to Q&P treatments. The microstructures and phase compositions of the quenched and partitioned steels were characterized with optical and scanning electron microscopy combined with EBSD phase mapping and X-ray diffraction measurements. The mechanical properties of the steels were studied with microhardness and tensile testing. The preliminary experiments suggest that aluminum-bearing steels can retain significant amounts of austenite after partitioning in a ferritic-martensitic microstructure. Promising strength-ductility ratios were also found in tensile testing. Based on the encouraging results, future work will be directed to produce microstructures with higher martensite fractions to impart higher strengths in steels combined with good ductility and formability.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A042. doi:10.1115/IMECE2013-63767.

The influence of specific method of severe hot deformation, forging plus rolling, that ensures true deformation |ε| = 1.39 in single pass was studied on two metastable β-class titanium alloys VT22 (Ti-5.0Al-4.79Mo-4.70V-0.97Fe-0.71Cr) and TIMETAL-LCB (Ti-1.50Al-6.82Mo-4.47Fe), wt%. The results on microstructure, crystallographic texture and tensile properties are presented. It was found that this type of severe deformation forms elongated not-recrystallized β-microstructure with sharp axial (110)β texture, and fine α-precipitates inside the β-grains. In as-deformed condition both alloys are characterized by high tensile strength (above 1500 MPa) and very low ductility. Additional annealing at α + β temperatures does not change β-grain microstructure and crystallographic texture, but gives the structure a balance of strength and ductility. It looks very attractive for practical application of the alloys. Results are discussed in terms of specific mechanism of deformation accommodation.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A043. doi:10.1115/IMECE2013-63828.

By synergistically combining distinct physical and chemical properties of different components, co-continuous polymer blending has become an important route to improve the performance of polymeric materials. Shear thickening fluid is a type of non-Newtonian fluid which has unique shear rate dependence and good damping properties. In this work, the authors combined the shear thickening fluid and a commodity polymer into a single system by forming a co-continuous blend via a melt processing technique. The processing window of such co-continuous blend was determined by referring to the thermal and rheological properties of raw materials and experimentally exploring various blending conditions. An increase of tanδ under dynamic mechanical analyzing testing was observed in the co-continuous blend compared with neat polymer as control, which indicated the enhancement of damping capabilities.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A044. doi:10.1115/IMECE2013-64141.

Centrifugal Cast tubes have been produced with ZA 8, ZA 12 and ZA 27 alloys with different rotational speeds of the mould (Viz. 400, 600 and 800 rpm). From the past research work, it was understood that cast tubes for ZA 8 and ZA 12 alloys with good mechanical properties were produced, with the mould rotation at 600 rpm. This observation was explained without the addition of refiners. In the present work, a uniform cylinder with good mechanical properties was produced with ZA8 alloy at 400 rpm only. This was due to the influence of refiner 1% Al-Ti-B2 along with low aluminium content and lower rotational speed of the mould. With higher rotational speeds of the mould, increase in the composition of aluminium and refiner reduce solidification rate of the melt forming irregular shaped cast tube with ZA12 and ZA 27 alloys.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A045. doi:10.1115/IMECE2013-64144.

Spray up method is one of methods for composite molding and it is traditional and common molding method that can deal with various shapes according to workmen skill. The essence of the composite molding impregnates resin to fiber;, in other words, is to substitute air included in the fiber for resin. Spray up method can spray matrix on mold together while cutting reinforcements continually, and the cutting of the reinforcement, setting up and the impregnation of the matrix are carried out at the same time. That is why working process is made efficiency and can cope with a design change easily. However, the quality of the composites depends on the techniques of workmen and the judgment with Spray up technique is too difficult, because it has not clarified that the difference of that techniques has how influence with manufactured products. In addition, in a spray up method, glass reinforcements is usually used, but carbon reinforcements is not put to practical use. High quality is required with the CFRP composite, and this is because it is thought that techniques of Spray up method does not satisfy this demand. In this study, motion analysis was used to compare the difference between Spray up techniques by expert and non-expert. Expert’s carrier of Spray up was 19 years and non-expert’s carrier was a year. Motion analysis, which is applied to various fields like sports or traditional crafts and so on, can visualize human motion. The Mac 3D System was used as equipment, since it is the most powerful tool for the motion capture and analysis particularly. The sampling rate was 60 Hz. The object of this study was to contribute that technique back to fabrication fields by analyzing and considering what was important factor. Furthermore, this trial is thought that leads to the development of new technology. As the result, the motion of expert’s lower half of body indicated different motion compared with non-expert one. Expert’s centroid moved smoothly and his motion showed constant tendency. On the other hand, non-expert’s motion was awkward in several points and his motion didn’t show the tendency like expert. Furthermore, The CFRP structures that manufactured with Spray up method are cut for the tensile testing. Tensile test were performed by using an Instron universal testing machine under a speed 1mm/min. Spray up technique is discussed based on the motion analysis method and moreover it is shown that Spray up method is useful in CFRP materials production.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A046. doi:10.1115/IMECE2013-64161.

Aluminum based hybrid composites are advanced materials having the properties of high hardness, superior wear resistance, strength, high elevated temperature and low thermal expansion coefficient. These hybrid composites are widely used in industries like automobile and aerospace. In this present paper 6061-T6 Aluminum alloy reinforced with SiC and Gr particles, hybrid composites are fabricated by using Friction stir processing (FSP) technique. It prevents the further development of hybrid composites for machining by nonconventional methods like water jet and laser cutting process. Electrical discharge machining (EDM) is used for machining the complex shapes of the material. This paper presents an overview of EDM studies conducted on the Al-SiC/Gr hybrid composites using a copper electrode in EDM. The EDM experiment machining parameters such as the dielectric fluid, peak current, pulse on, pulse off times are changed to explore their effects on machining performance, material removal rate (MRR), Tool wear rate (TWR), and surface roughness (SR). It is observed that the MRR and SR of the Al-SiC/Gr hybrid composites increase with an increase in the current.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A047. doi:10.1115/IMECE2013-64163.

In recent years, a high quality and accurately manufactured surface is needed for micro channels for micro-TAS (micro-total analysis systems, a kind of MEMS technology) chips in medical fields. We demonstrated that the use of smaller machine tools is an effective method to reduce the environmental impact in the small parts manufacturing field. Then, in this report, we focus on magnetic polishing for micro channels with a ball-nose-shaped tool, integrating the end milling and polishing processes in a desktop-sized machine tool. The magnetic brush was formed by adhering a magnetic polishing paste, which was composed of abrasive grains (alumina, particle size 0.05 um), metallic particles (cast-iron, diameter 1–100 um), and solvating media (vegetal oil), to the tip (radius 2 mm) of the ball-nose-shaped tool, which was a permanent magnet and a prototype micro tool with a ball-nose end mill shape. We attempt to end mill and polish the surface of micro channels with a prototype magnetic tool and a desktop-sized machine tool. The quality of the machined surface is estimated with a high accuracy surface profile meter. As a result, it can be seen that the proposed method is effective to machine and finish the micro channel surface for micro-TAS chips.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A048. doi:10.1115/IMECE2013-64402.

Aluminium alloys are being widely used in naval applications owing to their excellent corrosion resistance and high formability characteristics. One of the most popular naval components is the tarpedo blade which makes use of forged aluminium alloy followed by anodizing surface treatment for corrosion protection. In recent years, there have been few attempts to replace the conventional aluminium alloys by their composites for the tarpedo blade applications. Literature review clearly says that CeO2 (Ceria) coating on aluminium and aluminium composites enhances their corrosion protection in aggressive marine environment. Further, there are reports suggesting that combination of CeO2 and TiO2 do yield better corrosion protection. However, there is no information on the work related to development of hybrid ceramic reinforced aluminium alloy matrices with CeO2 and TiO2 as particulate reinforcements for potential naval applications. In the light of above, the present work focuses on the development of novel Al6061-CeO2-TiO2 hybrid metal matrix composite by stir casting route followed by hot extrusion with an extrusion ratio of 8:1 at a temperature 550 °C and hot forging at 475 °C. The developed forged hybrid composites and the matrix alloy have been evaluated for microstructure, micro hardness and slurry erosion wear tests as per the ASTM Standards.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A049. doi:10.1115/IMECE2013-64416.

The braided fabrics are one of the typical textiles and have been expected to be an excellent performs for the reinforcements of composite materials. Fig.1 shows schematic drawing of a braided fabric. Braided fabrics are composed of Braided Yarns (BY) oriented diagonally and Middle End Yarns (MEY) inserted into the fabric in longitudinal direction. In previous study, it was clarified that the internal structures for the braided fabric were decided with 4 parameters; area and cross-sectional shape of braiding yarns, the braiding angle and distance between braiding yarns. And it have been suggested that internal structural parameters for braided fabric reinforced composites with thermo-setting resin are possible to be predicted. However in the case of braided composites with thermoplastic resin, impregnation mechanism of thermoplastic resin with solid state is completely different from that of thermosetting resin with liquid state. In order to predict internal structures of braided composites with thermoplastic resin, it is necessary to investigate the impregnation process or mechanism of thermoplastic resin in to fiber bundles apply enough heat on thermoplastic resin to be liquid state for good impregnation especially in the case of intermediate material such as comingled yarn, and etc.

The purpose of this study is to predict the relationship between dimensional and internal structural parameters for braided fabric reinforced thermoplastic composite. The braided fabric was fabricated with intermediate material such as commingled yarns. During molding with heat and pressure, effect of molding time on the mechanism of impregnation and internal structural parameters were investigated.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A050. doi:10.1115/IMECE2013-64459.

Silicon nitride (Si3N4) possesses excellent hot hardness, wear resistance coupled with good corrosion resistance. Further, it possesses high anti friction properties making it an ideal reinforcement in developing high quality light weight, metal matrix composites for tribological applications. Silicon nitride has been successfully dispersed in aluminum alloy matrices. Their tribological properties with the beneficial effect of silicon nitride in enhancing the wear resistance of metal matrix composite have been reported by several researchers. Most of the researchers have focused on development of silicon nitride reinforced aluminum composite by powder metallurgy and casting route. However, meager information is available as regards the secondary processing of these composites in particular hot extrusion. Several researchers have reported an improved tribological behaviour in composites after extrusion. Hot extrusion of light weight metal matrix composites is very challenging. In the light of the above, this paper discusses the tribological behaviour of hot extruded Al6061 aluminum composites, which were initially developed by stir casting technique. Nickel coated silicon nitride particles were dispersed in Al6061 alloy using stir casting process. The cast composites were extruded at an extrusion ratio of 1:10 adopting a temperature of 550°C. The hot extruded composite (6Wt% Si3N4) and the matrix alloy were subjected to metallographic studies, microhardness and friction and wear tests using a pin on disc machine. Friction and wear test were carried out at loads ranging from 10 to 60 N at a sliding velocity of 0.314m/s. The worn surfaces and wear debris analysis have been carried out to understand the mechanism of wear in the developed hot extruded composites. The developed hot extruded composites exhibited lower coefficient of friction and wear rates when compared with matrix alloy.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A051. doi:10.1115/IMECE2013-64734.

In this investigation, the influence of tool rotational speed on wear and mechanical properties of Aluminum alloy based surface hybrid composites fabricated via Friction stir processing (FSP) was studied. The fabricated surface hybrid composites have been examined by optical microscope for dispersion of reinforcement particles. Microstructures of all the surface hybrid composites revealed that the reinforcement particles (SiC, Gr and Al2O3) are uniformly dispersed in the nugget zone. It is observed that the microhardness is decreased with increasing the rotational speed and exhibited higher microhardness value in Al-SiC/Al2O3 surface hybrid composite at a rotational speed of 900 rpm, due to presence and pining effect of hard SiC and Al2O3 particles. It is also observed that high wear resistance exhibited in the Al-SiC/Gr surface hybrid composites at a rotational speed of 900 rpm due to presence of SiC and Gr acted as load bearing elements and solid lubricant respectively. The observed wear and mechanical properties have been correlated with microstructures and worn morphology.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A052. doi:10.1115/IMECE2013-64866.

In this work, millimeter-scale tubular combustion channels were fabricated from ceramic precursor materials. Co-extrusion of structured feedrods holds promise for the development of multi-layered, functionally graded and/or textured combustor walls, but requires a polymer binder that is difficult to remove before structures can be sintered to full density. In conventional thermal debinding, cracking is a major issue, where crack formation is attributed to a lack of pore space for outgassing of pyrolysis products. The main focus of this study is to validate a manufacturing process that uses a combination of solvent de-binding and thermal debinding, which is applied to a simple combustor geometry. Alumina powder was batched with a mixture of polyethylene butyl-acrylate (PEBA) and polyethylene glycol (PEG) in a torque rheometer. A 19mm feedrod, consisting of a carbon-black/binder mixture as core, and a surrounding ceramic/binder mixture forming the wall, was extruded through a 5.84 mm die. The binder removal involves two processing steps, where the PEG content was removed by solvent extraction (SE) to initiate pore formation, after which thermal de-binding by pyrolysis removes the remaining binder and carbon-black. Solvent extraction was performed in water at three different temperatures for various times. The 1:1 mixture of PEG:PEBA showed the highest PEG removal of 80wt% for 6 hrs extraction. The thermal de-binding cycle was designed based on thermo-gravimetric analysis (TGA) and successfully performed with a ramping rate of 1.25°C/min to 1000°C without any crack formation. After de-binding, samples were sintered at 1600°C for 1 hr. SEM analysis showed some void spaces in the solvent extracted samples but confirmed that solvent extraction followed by thermal de-binding yielded the best results. The viability of sintered ceramic tubes was tested for conditions typical for thermal cycling in a combustion environment.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A053. doi:10.1115/IMECE2013-64883.

The present work reports on the growth and characterization of titanium nitride (TiN) nanowires on silicon substrate using a pulsed laser deposition (PLD) method. The TiN nanowires were grown on single crystal silicon substrate with (100) and (111) orientations at a range of substrate temperatures and under both nitrogen ambient and vacuum. The different orientation of silicon was chosen to see the effect of the substrate orientation on the growth of TiN nanowires. The laser energy entering the vacuum chamber to impinge the TiN target for nanowire deposition was varied from 70 to 80 mJ. The TiN nanowires samples were characterized using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). The diameter of the nanowires was observed to increase from 25 nm to 40 nm with an increase in laser beam energy entering the chamber. The shape and orientation of the nanowires was observed to be the same for (100) and (111) oriented silicon substrates as observed in SEM images. Corrosion tests were also conducted on the TiN nanowires.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A054. doi:10.1115/IMECE2013-64924.

The main purpose of this paper is to investigate mechanical properties of thin films of strontium carbonate (Sr2CO3) doped with hydroxyapatite (HA) on titanium substrates using nanoindentation techniques. The variation in the weight percentages of strontium carbonate of 0 wt %, 2.5 wt % and 100 wt % of Sr2CO3 in hydroxyapatite on a titanium substrate were used to investigate the effect of strontium carbonate on the surface modification for biological application. The hope is to use these results to improve the surface hardness of dentures and boost cavity prevention, and to improve menopause bone loss and help in its remodeling. The hardness and elastic moduli of different weight percents of variation in the compositions of strontium carbonate in Sr2CO3 - HA thin film layers deposited at 600 °C on titanium substrates using Pulse Laser Deposition (PLD) at high vacuum of 10−6 Torr were measured. The effect of varying Sr2CO3 in HA on the crystallinity, on the microstructure and on film thickness was determined using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and stylus profilometer respectively. The Sr2CO3 - HA with the composition of 2.5 wt. % of Sr2CO3 has average film thicknesses of each composition of the film were also recorded and a hardness performance of 3.89 GPa, good peak broadening was also observed in the 2.5 wt % composition Sr2CO3 using XRD. The variations in the composition of strontium Carbonate in Hydroxyapatite in term of hardness and elastic moduli were reported.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A055. doi:10.1115/IMECE2013-65233.

Humidification membranes are vital to maintaining optimal operation conditions in polymer electrolyte membrane (PEM) fuel cells. Dry inlet air must be humidified to achieve an efficient reaction within the fuel cell. Nafion is currently the material of choice for humidification membranes due to its excellent water transport properties. However, the performance of Nafion comes at a high cost (∼ $1000/m2). There is a need to reduce membrane cost by developing an alternative material. The first step in developing a new membrane material is characterization of membrane performance. A humidification membrane measurement system was developed to determine vapor mass transfer rates through Nafion humidification membranes. The system creates a controlled environment where inlet water flow, air flow, temperature and pressure are regulated in order to measure the permeation rate of water through a membrane.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A056. doi:10.1115/IMECE2013-65724.

Heterogeneous object modeling and fabrication has been studied in the past few decades. Recently the idea of digital materials has been demonstrated by using Additive Manufacturing (AM) processes. Our previous study illustrated that the mask-image-projection based Stereolithography (MIP-SL) process is promising in fabricating such heterogeneous objects. In the paper, we present an integrated framework for modeling and fabricating heterogenous objects based on the MIP-SL process. Our approach can achieve desired grading transmission between different materials in the object by considering the fabrication constraints of the MIP-SL process. The MIP-SL process planning of a heterogeneous model and the hardware setup for its fabrication are also presented. Test cases including physical experiments are performed to demonstrate the possibility of using heterogeneous materials to achieve desired physical properties. Future work on the design and fabrication of objects with heterogeneous materials is also discussed.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A057. doi:10.1115/IMECE2013-66233.

Manufacturing possibility was experimentally investigated for a bulk multilayered Ni-ZrO2 system functionally graded material (FGM) by powder injection molding. Ni-ZrO2 system FGMs with various composition gradients and layer numbers were manufactured from compounds used in powder injection molding methods. Compounds with various chemical compositions were obtained by kneading Ni and ZrO2 powders with a polymeric binder. A compound was filled into a mold and heated to the softening temperature of binder. A compact was obtained by compressing at the softening temperature. Some compacts were stacked in the mold and compressed at the softening temperature again. The multilayered compact was heated to near the melting point of Ni. The FGM with little flaws was obtained for high composition gradient in ZrO2 rich side. However, calculated maximum thermal stress of the FGM was higher than that of the linear composition gradient. The maximum thermal stress was compressive stress and occurred in ZrO2 rich side. The compressive strength of a ceramics is higher than that of the tensile strength. Thus, the thermal compressive stress in ZrO2 rich side would be effective to manufacture a bulk multilayered Ni-ZrO2 system FGM by powder injection molding.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Advancing Sensing, Measurement, and Process Control in Manufacturing

2013;():V02AT02A058. doi:10.1115/IMECE2013-62240.

This work proposes a possible framework for implementing model-based optimization of process parameters in a milling operation. The latter is the first step in the development of an artificial machine tool operator, i.e. a supervising controller that looks at the process status and continuously estimate an optimal set of controls on the basis of a given process model. After a description of the software architecture, the discussion on the process model adopted for the definition of the target function, and the illustration of the optimization algorithm (the Nelder-Mead Method), the paper presents the results obtained from the application of the optimization system to two different case studies, showing how the same part-program can be run with significant improvements in productivity when the feed rate and spindle speed overrides are continuously varied during the machining according to profiles calculated by the proposed process optimization system.

Topics: Optimization , Milling
Commentary by Dr. Valentin Fuster
2013;():V02AT02A059. doi:10.1115/IMECE2013-62366.

Fiber-reinforced ceramic matrix composites (FRCMCs) have potential applications in aerospace and other high-tech fields. Meanwhile, it is significant to evaluate the grinding surface quality of FRCMCs. But according to FRCMCs’ anisotropic and non-homogeneous structure, it is difficult to evaluatethe surface quality with the traditionalmeasuring method used in metal material. The present paper studied the 3D micro-topographical measurement and evaluationfrom a new perspective. The research is based on some new discovery that the material enhanced fiber orientation played key role in micro-topographical of FRCMC grinding surface. Using a non-contact optical measurement instrument, the method was developed on 2.5D SiO2/SiO2 composite. Through a series of measuring experiments, we found that both starting position of measurement and sampling conditions affected on the measurement results. This paper recommendedoptimization measurement parameter valuesof sampling conditions, and also analyzedcharacteristics of the RCMC grinding surface topography on amplitude, wave distribution and surface supportcharacteristics in details. The results show that the optimal range of sampling interval is 40 μm to 70 μm, the range of sampling area is better more than 64mm2 and the range of sampling speed is 8 to 14mm/s. The measurement of surface topography is the bridge framed between the manufacture and parts performance, so theresearchobtained will be an important technical support on improvingthe processing quality of FRCMC.

Topics: Grinding
Commentary by Dr. Valentin Fuster
2013;():V02AT02A060. doi:10.1115/IMECE2013-62543.

The hereby presented research, funded by the restricted grant LIDER, NCBiR, deals, in part, with the identification of the full implementation potential of the proposed optical measurement techniques in determination of surface flatness parameters, and their comparative assessment. The test methods included the photogrammetric measurement technique (TRITOP, GOM) and the structural light scanning approach (scanner ATOS, GOM), while the CMM measurement (DEA Global Image Clima) was the reference method. The accordingly designed and assembled experimental test stand comprised 2 steel plates. The test surfaces of the plates were appropriately ground; subsequently, the entire test stand was blackened to ascertain efficient optical scanning. Furthermore, the plates were connected by means of 8 screws, thus introducing considerable distortion. A measurement area of 140 × 240 mm was defined on the plate test surface, as determined by CMM, denoting 15 measurement paths of 240 mm in length, distributed every 10 mm, and characterized by measurement point densities of 1, 5, and 20 pt/mm. The reference CMM measurements were conducted on 3 consecutive days at different times (22 measurements in total) to exclude any possible surface modifications. Subsequently, optical scanning was applied and the measurement points lying at the cross-sections of the CMM measurement paths were isolated from the obtained polygon mesh. To further apply the photogrammetric method, the test surface was labeled with markers distributed every 10 mm and coinciding with the CMM measurement paths.

Comparative analysis of the flatness parameter for the selected CMM measurement and the measurement values obtained by means of the tested optical methods included:

- the entire measurement area,

- the sections comprising 80, 60, 50, 45, 40, 30, 20, 15, and 10 % of the entire measurement area, decreasing centrically,

- the measurement sub-areas of 30 × 50 mm allotted in the corners and in the center of the test plate.

The photogrammetric error of the tested parameter was established at 1.26–19.82 %, depending on the size of the measurement area. The corresponding error value, as determined by the structural light scanning technique, amounted to 0.03–4.31 %.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A061. doi:10.1115/IMECE2013-62841.

The hereby presented study reports on the results of research funded by the NCBiR improvement grant. The goal of the undertaken experimental effort was to eliminate the laborious process of marking out from the technological procedure of cast machining. Marking out, even in highly automatized machining enterprises, is performed manually. It assesses casting accuracy, as well as denotes surpluses on machining surfaces. The precision of marking out is, therefore, dependent on individual performance of a given worker. Moreover, gauging casts of cylindrical (non-perpendicular) shape is highly problematic. Incorrect marking out generates quantifiable material (cast iron) and machining losses, as well as production interruptions.

Herein, we present an innovative cast machining technology based on cast model scanning. Prior to machining, each body is scanned according to the technology guidelines. The subsequent comparison of the cast model and the model of the machined body affords geometrical accuracy assessment of the cast and the determination of optimal machining surpluses. The surplus verifying criteria include: machining volume minimization, tool working motions minimization, and idle tool motion minimization. Moreover, in special cases, high productive cutting (HPC) or high speed machining (HSM) optimization of cast technology, as well as elimination of superfluous procedures (e.g. milling of machining datum surfaces), are possible. The proposed comparative analysis of the aforementioned 3D models additionally affords acquisition of data for positioning (horizontal alignment) of the machined cast, e.g. the required length of technological supports.

The hereby presented experimental results (obtained in an industrial setting) confirm the proposed elimination of the marking out process, thereby affording time reduction of preparatory procedures, initial assessment, and positioning of the cast for machining, as well as a decrease of machining volume by approx. 10 % (for the investigated casts). Experimental simulation results allowed us to estimate the machining volume minimization reaching up to 25 % (depending on the cast shape and the machining process specifications). Moreover, our investigation indicated a possibility of detection of casting flaws caused by insufficient surface brushing down. As the casts are painted post-brushing, the interfering sand mold remains are easily overlooked and often cause cutting-tool damage leading to costly production interruptions.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A062. doi:10.1115/IMECE2013-62932.

The dimensional and positional information is very important for laser materials processing of components, especially for laser cladding-based additive manufacturing. Therefore, inspection of the component based on its original CAD model is essential to ensure the component meeting the geometrical requirements. In general, the processed component has to be dismounted from the laser fabrication system before it can be inspected, which is time-consuming and may introduce alignment error from datum.

In this paper, a 5-axis in-line measurement system is introduced, in which a non-contact laser measuring method along with CAD/CAM software is integrated to a laser materials processing system. An algorithm has been developed to automatically generate NC programs for measurement and comparison for outside features of components. Therefore, the inspection can be performed just after the component has been fabricated on the same system. Comparing to a 3-axis measuring system we reported before, the developed 5-axis inline measurement system provides much more flexibility, accessibility and accuracy for performing measurement on site. The developed in-line measuring capability can extend the functionality of conventional laser materials processing system and significantly shorten inspection time.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A063. doi:10.1115/IMECE2013-62940.

Geometric dimensioning & tolerancing (GD&T) and process capability indices (PCIs) play critical roles in quality assurance. Conventional PCIs, when used together with GD&T, strongly rely on certain assumptions (e.g. normality and regularity of specification region). GD&T requirements often involve interrelated tolerances, creating irregular tolerance regions. Violation of these assumptions misleads the results (18) and interpretation in applications. A non-conformity (NC) index is developed based on nonparametric distribution model and numerical assessment techniques. Kernel is used for probability density (pdf) estimation and Monte Carlo integration algorithm is adopted for NC analysis, i.e. integration of a pdf over a specification region. The method is validated by case study.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A064. doi:10.1115/IMECE2013-63461.

Recently, a novel manufacturing technology has spread out with a five-axis machining center. It is especially important to keep the surface roughness on an entire machined surface constant. Thus, we proposed a novel method for maintaining a constant feed speed vector at the cutting point between the end-mill tool and the workpiece surface by controlling two linear axes and a rotary axis with a five-axis machining center. In the present report, we focused on machining the combined inner and outer radius curvature and investigating the influence of synchronous control error between the linear axes and rotary axis on the machining accuracy and surface roughness. As a result, we determined that it is possible to suppress sudden change in the synchronous motion error by accurately aligning the motion direction of the linear and rotary axes and the feed speed vector at milling point at the contact point of the inner and outer circles.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A065. doi:10.1115/IMECE2013-63493.

Forging is an essential metal-working process in manufacturing. Forging tonnage signals, which are originally used to monitor the structural deformation of the forging machines for safety purpose, had been increasingly used to monitor the performance of the forging processes. Despite recent advances on forging process monitoring, little attention had been paid to expedite the preparation of the data labeling procedure for different fault classes of the forging tonnage signals. Currently, existing data are mostly classified and labeled by experts, which is extremely time consuming and error prone. In this paper, a new forging tonnage signal clustering method is proposed to label the multiple-operation forging tonnage signals automatically. Due to different workload setups of the forging machines, a Finite State Machine (FSM) modeling approach is developed to utilize the domain knowledge of the multiple-operation forging processes. An adaptive iterative learning scheme is deployed to optimize the clustering results based on minimum classification error of the tree-structure classifier based on FSM. Real-world forging tonnage signals are used in the case study to demonstrate the proposed method.

Topics: Machinery , Forging , Signals
Commentary by Dr. Valentin Fuster
2013;():V02AT02A066. doi:10.1115/IMECE2013-63898.

The poor thermal conductivity and low elongation–to–break ratio of titanium lead to the development of extreme temperatures localized in the tool–chip interface during machining of its alloys and cause accelerated tool wear. The atomization–based cutting fluid (ACF) spray system has recently been demonstrated to improve tool life in titanium machining. In order to understand the cooling and lubrication mechanism of the ACF spray system, it is important to determine the temperature gradient developed inside the entire tool–chip interface. The objective of this work is to measure the cutting temperatures at various locations inside the tool–chip interface during titanium machining with the ACF spray system. The temperature gradient and mean cutting temperature are measured using the inserted and the tool–work thermocouple techniques, respectively. Cutting temperatures for dry machining and machining with flood cooling are also characterized for comparison with the ACF spray system temperature data. Findings reveal that the ACF spray system more effectively reduces cutting temperatures over flood cooling. The tool–chip friction coefficient data indicate that the fluid film created by the ACF spray system also actively penetrates the tool–chip interface to enhance lubrication during titanium machining, especially as the tool wears.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A067. doi:10.1115/IMECE2013-64296.

Draw-bending is one of the typical deformation modes in sheet metal forming. It causes serious thickness reduction to sheet metals and very often leads to fracture. Therefore, it is crucial to establish a fracture criterion for sheet metals subjected to draw-bending. In this study, a fracture criterion for sheet metals subjected to draw-bending is investigated using the concept of the forming limit stress criterion. The test material used is a dual phase steel sheet (DP590Y) with a thickness of 1.2 mm and a tensile strength of 590 MPa. Draw-bending experiments of a wide specimen are performed using three different die profile radii: 4, 6 and 10 mm. The forming limit stress of the test material under draw-bending, σDB, is precisely determined from the experimentally measured drawing force and the cross sectional area of the specimen, determined from the strain distribution in the vicinity of fracture using a 2 mm square grid. In addition, multiaxial tube expansion tests are performed to measure the forming limit stress under plane strain tension, σPT. It is found that σDB almost coincides with σPT. Thus, it is concluded that σPT can be a fracture criterion for a sheet metal under draw-bending, at least for the high strength steel sheet used in this study.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A068. doi:10.1115/IMECE2013-65057.

The production metrology of today is still dominated by tactile probing systems. However some special metrological tasks cannot be fulfilled by this technique, one example is in the high precision manufacturing of surfaces and structures, which become ultra-miniaturized, complex and fragile. The inspection of small boreholes and cavities is also an example with very tight tolerances which demands non-contact miniaturized sensors. Particularly the measurement of the shape of spray holes in modern fuel injection nozzles for diesel engines fits this statement, as its shape represents the key factor for maximal motor efficiency, as well as minimal pollutant emissions. Any deviation from its design shape significantly affects spray breakup and can lead to unequal distribution of flow and pressure changes. These holes can have diameter of 150 microns, with a tendency to even smaller diameters in future systems.

Within this work the integration of a fiber optic sensor for distance measurements in measuring machines, specifically for borehole inspection, is described. The used device is a form-tester (Mahr GmbH, MMQ-400) with 3 degrees of freedom. The motion of the machine axis will be controlled with help of image processing operation which are based on pictures taken from the specimen’s top surface. For this mean a micro camera will be mounted on the form-tester. By applying in-house developed MATLAB codes, the exact position of the boreholes and that of the fiber optic probe is obtained, so that an automated positioning and measurement (e.g. round-out and roundness tests) could be performed. This process enhances both the precision due to an optimized sensor positioning and speed of the measurement rather than manual execution. Different positioning scenarios will be discussed and compared in this paper, to prove the capability of the proposed system as well as its adaptivity.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A069. doi:10.1115/IMECE2013-65190.

One main objective of the technique of reverse engineering is focused on development of new products based on the improvement of existing products. The present work aims to demonstrate a sustainable methodology exploring the capabilities of reverse engineering, applied to produce brand new geometric solutions for safety metallic components incorporated in footwear. The data acquisition is done using different techniques, contact methods (CMM – Measuring Coordinate Machine) and non-contact methods (Laser Scanning). Those measuring techniques for data acquisition are the key entry for the 3D shape recovery, boosting the development of new components based on the improvement of existing products. Despite these techniques being widely explored in multiple engineering sectors, author’s contribute was focused on the proposal and validation of a sustainable methodology based on an algorithm in MATLAB that performs the surface generation under user control. Such methodology has been tested through a real model of a toecap component used in safety footwear.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A070. doi:10.1115/IMECE2013-65226.

The normative behavior of innovative toe cap models for safety footwear with different thickness ranges and materials, including Advanced High Strength Steels (AHSS), was investigated by means of the quasi-static compression test. The main purpose of this work was to confirm the solution potential of a new geometric redesign model, from a reverse engineering approach, that maximizes the potential of energy absorption. The investigation was performed with two dissimilar and evolutionary geometric models, and several properties correlations such as: stiffness, thickness range and material properties. From a Finite Element Analysis and experimental test results of toe cap prototypes, it was found that the geometric factor had significant influence on the balance of the structural stiffness with thickness reduction. The study of the elastic deformation and the springback effect of different models, allows pointing an improved weight saving of a new toe cap component.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A071. doi:10.1115/IMECE2013-65381.

This paper presents a 5-axis machine tool compensation method that uses tool tip measurements recorded throughout the joint space to construct a set of compensation tables. The measurements can be taken using a laser tracker, permitting rapid measurement at most locations in the joint space. To compensate the machine tool, the measurements are used to identify a kinematic model, and then that model is used to construct an optimal set of compensation tables. The kinematic model is composed of the nominal, or ideal, kinematics with additional (unknown) six degree of freedom errors inserted between each of the joints. The error kinematics are identified using the measurement data and a maximum likelihood estimator. The identified model is then projected onto a joint-compensation space that maps to the compensation tables in the machine tool controller. Simulations of the approach are provided using measurement data from a Flow International 5-axis machine tool equipped with a Siemens 840D controller. The simulation results show a mean residual error of .076 mm, which is a 76.8% reduction from the uncalibrated machine tool.

Topics: Machine tools
Commentary by Dr. Valentin Fuster
2013;():V02AT02A072. doi:10.1115/IMECE2013-65423.

A novel computer-aided manufacturing (CAM) software system is proposed for laser ablation machining process. The algorithms and prototype software system is designed to offer efficient optimization of tool path for controlled delivery of laser energy into work-piece. The software simplifies part program creation and maintains constant velocity of the sample stage for each segment of a complex tool trajectory. These features enable efficient deposition of laser energy into the work piece and therefore, reduction in heat-affected zone is expected in laser ablation based micromachining. The reported software provides fast modification of tool path, automatic and efficient sequencing of path elements in a complicated tool trajectory, location of reference point and automatic fixing of geometrical errors in imported drawing exchange files (DXF) or DWG format files.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A073. doi:10.1115/IMECE2013-65607.

The objective of this project is to experimentally investigate the influence of Minimum Quantity Lubrication (MQL) on tool wear and tool life in micro hardmilling. The experiments were performed on stainless steel using uncoated WC micro-mill with the nominal diameter of 508 microns. The tool wear is characterized by the volume of the material loss at the tool tip. In order to reveal the progression of the tool wear, the worn tool was examined periodically under SEM after a fixed amount of workpiece material removal (1.25 mm3 or 5 slots in this study). The tool life was characterized as the amount of material removed, instead of the conventional cutting times. The feedrate and the spindle speed were fixed, and two levels of axial depth of cut (50 and 75 microns) were compared. The higher depth of cut leads to longer tool life. The machining performance under MQL is superior to the dry machining for both process conditions in terms of the tool life. The cutting forces in feed direction and the surface roughness at the bottom of the slots were also examined during the experiments. The magnitude of the machining forces showed cyclic pattern for both MQL and dry machining. The SEM images and the cutting force signals suggested that the dominant mode of the tool wear in micro-milling is edge chipping and abrasive wear at the tool tip. The loss of the micro-grain of WC at the cutting edge leads to edge chipping, which reduces the effective cutting diameter; the abrasive wear enlarge the edge radius, causing the cutting force increase. As the cutting edge radius reaches a certain dimension, the whole edge was stripped off, a new edge formed with a smaller edge radius, and the cycle restarts. Under MQL cutting conditions, three cycles were observed before tool failure, while under dry machining conditions, the tool only experienced two cycles before tool breakage. The surface roughness at the bottom of the slots improved significantly with the application of MQL for all levels of the tool wear. The surface roughness did not increase drastically as the tool wear increased. It reached a plateau after the tool wear went into gradual wear state. Further experiments and theoretical analysis will be pursued in the future to gain a deeper understanding of tool wear mechanism in micro-milling.

Topics: Wear , Milling
Commentary by Dr. Valentin Fuster
2013;():V02AT02A074. doi:10.1115/IMECE2013-65788.

Microfluidic technologies hold a great deal of promise in advancing the medical field, but transitioning them from research to commercial production has proven problematic. We propose precision hot embossing as a process to produce high volumes of devices with low capital cost and a high degree of flexibility. Hot embossing has not been widely applied to precision forming of hard polymers at viable production rates. To this end we have developed experimental equipment capable of maintaining the necessary precision in forming parameters while minimizing cycle time. In addition, since equipment precision alone does not guarantee consistent product quality, our work also focuses on real-time sensing and diagnosis of the process.

This paper covers both the basic details for a novel embossing machine, and the utilization of the force and displacement data acquired during the embossing cycle to diagnose the state of the material and process. The precision necessary in both the forming machine and the instrumentation will be covered in detail. It will be shown that variation in the material properties (e.g. thickness, glass transition temperature) as well as the degree of bulk deformation of the substrate can be detected from these measurements. If these data are correlated with subsequent downstream functional tests, a total measure of quality may be determined and used to apply closed-loop cycle-to-cycle control to the entire process. By incorporating automation and specialized precision equipment into a tabletop “microfactory” setting, we aim to demonstrate a high degree of process control and disturbance rejection for the process of hot embossing as applied at the micron scale.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A075. doi:10.1115/IMECE2013-65984.

Traditional Computer Numerical Control (CNC) machines use ISO6983 (G/M code) for part programming. G/M code has a number of drawbacks and one of them is lack of interoperability. The Standard for the Exchange of Product for NC (STEP-NC) as a potential replacement for G/M code aims to provide a unified and interoperable data model for CNC. In a modern CNC machine tool, more and more motors, actuators and sensors are implemented and connected to the NC system, which leads to large quantity of data being transmitted. The real-time Ethernet field-bus is faster and more deterministic and can fulfill the requirement of data transmission in the high-speed and high-precision machining scenarios. It can provide more determinism on communication, openness, interoperability and reliability than a traditional field-bus. With a traditional CNC system using G/M code, when the machining is interrupted by incidents, restarting the machining process is time-consuming and highly experience-dependent. The proposed CNC controller can generate just-in-time tool paths for feature-based machining from a STEP-NC file. When machining stoppage occurs, the system can recover from stoppage incidents with minimum human intervention. This is done by generating new tool paths for the remaining machining process with or without the availability of the original cutting tool. The system uses a real-time Ethernet field-bus as the connection between the controller and the motors.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A076. doi:10.1115/IMECE2013-66649.

A great amount of research is being conducted to incorporate smart material actuators in aerospace applications such as (1) turbo fan engines (2) servo flap actuators for helicopter rotor control. For example, a piezoelectric stack actuator, coupled with mechanical or hydraulic amplification could provide the actuation required for the variable pitch fan system with a potentially higher level of reliability. In addition, piezoelectric actuation system could do so at a lower overall weight. However, there are limitations with existing piezoelectric stack actuators relative to power requirements. Therefore, a new approach has been investigated to improve these characteristics in order for piezoelectric stacks to be a feasible solution for these types of large scale applications. A new configuration involving dielectric, conductor, piezoelectric material in a particular sequence of stack actuation is examined and experimented. A nonlinear lumped parameter model of a piezoelectric stack has been developed to describe the behavior for the purpose of control actuation analysis.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A077. doi:10.1115/IMECE2013-66767.

Sub-micron accuracy and precision in measuring unconstrained, spatial motion is pivotal in science and engineering. It imposes stringent requirements on the accuracy, reliability, and invasiveness of sensing devices (including lasers, lidar sensors, or optical scales). While the capabilities of these devices have seen dramatic improvements in the last decades, the needs for sub-micron accuracy, low-invasive sensors greatly outpace the available solutions. The root cause of measurement difficulties is a conflict between the very nature of motion (simultaneous translations and rotations relative to a chosen reference base) and the fundamental requirement of measurement accuracy known as the Abbe principle.

Small and accurate Microsystems Technology based inertial sensors (accelerometer and gyroscopes) can alleviate, or at least significantly mitigate, many of the current difficulties. If contained in small Inertial Measurement Units (IMU) and equipped with a wireless signal transmission, they can be placed on or very close to the objects whose motion is to be measured.

Furthermore, as long as the IMU, its fixture, and some region of this object around the fixture can be considered as rigid, coordinate transformation rules facilitate converting signals measured by IMU into translations and rotations of any point in this rigid region. Consequently, a virtual 6-DOF sensor can be created. Its dimensions are infinitesimally small, and it can be “placed” anywhere within the above rigid region. In particular, it can be placed such that it is collinear with the displacements of the cutting tool or robot’s end effector, and satisfies the Abbe principle.

We present a High Accuracy, Low-Invasive Displacement Sensor (HALIDS) for application in manufacturing and in engineering design. The sensor is capable of measuring simultaneously 6-degrees-of-freedom displacements of objects. Its short term resolution is down to 0.1 nanometer and accuracy better than 1 micron. The sensor can be built small, light and wireless. Results from experimental evaluation of two prototype versions are presented.

Topics: Sensors , Displacement
Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Computational Modeling and Simulation for Advanced Manufacturing

2013;():V02AT02A078. doi:10.1115/IMECE2013-62193.

Laser cladding (LC) of tool steel has significant application in rapid tooling, and surface coating for worn-out components in different industries. During the LC process, several phase transformations influence the microstructural and mechanical properties of the deposited layer. In order to successfully implement the LC process, it is essential to understand the relationship between the thermal cycle (heating and cooling), phase transformations, and the output quantities of the deposited layer. In this study a direct diode laser with a power of up to 8 kW was used to deposit AISI H13 tool steel on mild steel grade A36 substrate to enhance its surface properties. Primarily, an experimentally verified three-dimensional (3-D) heat transfer analysis was developed based on the finite element method to compute temperature history during the cladding and cooling process. Next, the computed thermal cycles were coupled with a semi-empirical thermo-kinetic model to estimate the hardness of deposited layers based on different cooling cycles in a time-temperature-transformation (TTT) diagram. Further, the microstructural details obtained from the cross-sections of the clad were correlated with the estimated thermal cycles and hardness. A good correlation between the modeled and experimental results revealed that the developed model can be used to estimate the microstructural characteristics and mechanical properties of the H13 layer produced by the LC process.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A079. doi:10.1115/IMECE2013-62468.

Controlling the temperature in friction stir processing (FSP) of Magnesium alloy AZ31b is crucial given its low melting point and surface deformability. A numerical FEM study is presented in this paper where a thermo-mechanical-based model is used for optimizing the process parameters, including active in-process cooling, in FSP. This model is simulated using a solid mechanics FEM solver capable of analyzing the three dimensional flow and of estimating the state variables associated with materials processing. Such processing (input) parameters of the FSP as spindle rotational speed, travel speed, and cooling rate are optimized to minimize the heat affected zone, while maintaining reasonable travel speeds and producing uniformity of the desired grain size distribution of the microstructure in the stirred zone. The simulation results predict that such optimized parameters will result in submicron grain sized structure in the stirred zone and at the corresponding stirred surface. These simulation predictions were verified using published experimental data.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A080. doi:10.1115/IMECE2013-62484.

Super-long amplitude transformer is an indispensable part of ultrasonic vibration system, often used in high power ultrasound applications. This paper put forward a new method to design and analyze super-long amplitude transformer. Firstly, by using the mechanical four-terminal network method to solve one dimensional longitudinal vibration equation, the frequency and vibration ratio of the ultrasonic transformer are obtained. Thereafter, two types amplitude transformers design scheme can be got by theoretical calculation, i.e. exponential and conical amplitude transformer. Finally, using FEM software ANSYS to analyze the modal, stress distribution and harmonic response of the amplitude transformer. According to the finite element simulation results, each of amplitude transformers has advantages and disadvantages. Compared with theoretical results, it is satisfied with demands of engineering. A new way is carried out for design and optimality of super-long amplitude transformer.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A081. doi:10.1115/IMECE2013-62539.

Sheet metal stamping processes play an important role among the mechanical manufacturing operation, since they are characterized by high productivity and reliability at low cost, low material waste and almost net shapes from design. In this study, based on the Marciniak and Kuczynski (M-K) model and the forming limit diagrams (FLD), the formability prediction for thermal stamping of magnesium alloy sheet has been carried out by means of the commercial finite element analysis software ABAQUS. Moreover, related experiments of thermal stamping were also performed to validate the model. The comparison between the numerical result and experimental observation shows a good agreement. Therefore, it may indicate that the presented approach can be employed in formability prediction of thermal sheet metal forming process.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A082. doi:10.1115/IMECE2013-62588.

Interfacial friction is important for manufacturing processes using ultrasonic vibration since ultrasonic energy is transferred from horn to welding interfaces of work pieces through movement and contact behavior of surfaces. A 3D thermal-mechanical FE model is built to investigate the interfacial friction behavior of ultrasonic vibration by simulating a typical ultrasonic welding (UW) process which uses the technology of ultrasonic vibration to form material joints. The effects of friction coefficient of horn/work piece interface and coefficient of friction work converting to heat on the thermal-mechanical fields of welding interface are investigated.

Topics: Friction , Metals , Vibration
Commentary by Dr. Valentin Fuster
2013;():V02AT02A083. doi:10.1115/IMECE2013-62868.

Titanium alloys are widely used in aerospace industry due to their excellent mechanical properties though they are classified as difficult to machine materials. As the experimental tests are costly and time demanding, metal cutting modeling provides an alternative way for better understanding of machining processes under different cutting conditions. In the present work, a finite element modeling software, DEFORM 3D has been used to simulate the machining of titanium alloy Ti6Al4V to predict the cutting forces. Experiments were conducted on a precision lathe machine using Ti6Al4V as workpiece material and TiAlN coated inserts as cutting tool. L9 orthogonal array based on design of experiments was used to evaluate the effect of process parameters such as cutting speed and feed with a constant depth of cut 0.25 mm and also the tool geometry such as rake angle on cutting force and temperature. These results were then used for estimation of heat transfer coefficient and shear friction factor constant, which are used as boundary conditions in the process of simulation. Upon simulations a relative error of maximum 9.07% was observed when compared with experimental results. A methodology was adopted to standardize these constants for a given process by taking average values of shear friction factor and heat transfer coefficient, which are used for further simulations within the range of parameters used during experimentation. A maximum error of 9.94% was observed when these simulation results are compared with that of experimental results.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A084. doi:10.1115/IMECE2013-62877.

Given a sequence of G01 codes, a linear interpolator outputs a refined sequence of G01 codes obeying the inequality constraints imposed upon the velocity, acceleration, etc., of the machining tool, and the tracking error, geometric error, etc., between the two sequences. While the output G01 sequence is usually obtained from a continuous motion by sampling along the trajectory by a constant interpolation period, a simple strategy of generating the blending curve between two concatenated line segments under the velocity and axis-wise acceleration constraints of the machining tool, is to use parabolas — trajectories of constant-acceleration motions.

This paper considers the estimation and control of the geometric error in such a linear interpolator. Classical model of chord error by approximating parabolas with their contact circles leads to incorrect result on the geometric error, if the latter is taken as the superposition of (i) the error of approximation of the input G01 trajectory by parabolas, and (ii) the chord error caused by sampling along the blended C1-smooth trajectory. By computing the geometric error directly without accumulating the approximation error and the chord error, we realize correct geometric error control by establishing inequality constraints on the accelerations of the motion.

This work is supported partially by 2011CB302404, NSFC 10925105, 60821002/F02.

Topics: Errors
Commentary by Dr. Valentin Fuster
2013;():V02AT02A085. doi:10.1115/IMECE2013-63055.

It is the basis for the new casting-rolling compound forming technology to investigate the rules of rolling deformation and microstructure evolution of casting ring blank. The initial rolling temperature of casting ring blank is one of the key factors influencing deformation and dynamic recrystallization behavior. In this paper, dynamic recrystallization models of as-cast 42CrMo steel were derived from thermo-simulation experimental results. Then, under DEFORM-3D software environment, deformation and dynamic recrystallization of 42CrMo casting ring blank were simulated at different initial rolling temperature by coupled thermo-mechanical finite element method. According to the simulation results, the effects of initial rolling temperature on strain fields distribution and dynamic recrystallization of 42CrMo casting ring blank were discussed. The results show that: (1) increased initial rolling temperature makes plastic deformation expand from ring’s outer and inner-layer to middle and distribute ever more evenly; (2) increased initial rolling temperature can lead to increased dynamic recrystallization fraction, but grain size of ring’s inner and outer-layer becomes smaller and smaller, while that of mid-layer coarser and coarser.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A086. doi:10.1115/IMECE2013-63302.

Roll bending is a continuous forming process where plates, sheets, beams, pipes, and even rolled shapes and extrusions are bent to a desired curvature using forming rolls. Over the years, with the advantages such as reducing setting up time, the cost in tooling investment and equipment, the roll bending process was fundamental for manufacturing cylindrical shapes. However, the process always leaves a flat area along the leading and trailing edges of the workpiece. Therefore, accuracy could be a challenge when the part to be produced is large and made of high strength steel. There are several methods to minimize the flat area. Among them, for the asymmetrical configuration, moving slightly the bottom roll along the rolling direction may have the highest effect. On the other hand local adjustment of the bottom roll location is also important for providing the pressure needed for gripping and carrying the workpiece through the rolls. Then by optimizing the vertical displacement of the bottom roll one can minimize the span of flat areas.

The main objective of this research is to assess 3D dynamic Finite Element (FE) model with Ansys/LS-Dyna for the simulation and analysis of the deformation of the workpiece during the manufacturing of cylindrical parts. Various dynamic simulations based on 3D element are performed to provide better understanding of the whole deformation history and to establish the relationship between the location of the bottom roll and the end shapes of the formed cylinders. The results from FE simulations are then compared with corresponding experimental results from an industrial roll bending machine in order to improve the quality of the final shape.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A087. doi:10.1115/IMECE2013-63441.

The variation propagation in mechanical assembly is an important topic in several research fields, such as computer aided tolerancing (CAT) and product quality control. Mathematical models and analysis methods have been developed to solve this practical problem. Tolerance analysis which is based on the rigid hypothesis can be used to simulate the mass manufacturing and assembly. The state space model and stream of variation theory are mainly applied in flexible part assembly. However, in precision machine tool assembly, both tolerance design and process planning critically impact the accuracy performance, mainly because of the fact that the gravity deformation, including the part deformation and the variation in the joint of two connecting parts, cannot be ignored in variation propagation analysis. In this paper, based on the new generation GPS (Geometrical Product Specification and Verification) standards, the verification and modeling of key characteristics variation due to gravity deformation of single part and adjacent parts are discussed. The accurate evaluation of position and orientation variation taking into account form errors and gravity deformation can be solved from this model by FEM. A mathematical model considering rail error, stiffness of bearings is introduced to simulate the motion error in gravity effect. Based on this work to more accurately calculate the variation propagation considering gravity impact, a state space model describing the assembly process of machine tools is proposed. Then, in any assembly process, the final accuracy can be predicted to find out whether the accuracy is out of design requirement. The validity of this method is verified by a simulation of the assembly of a precision horizontal machining center.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A088. doi:10.1115/IMECE2013-63518.

In this study, in order to investigate the power consumption of feed drive system, a mathematical model to predict for the electric power consumption of feed drive systems is proposed by using the single-axis experimental apparatus. This can be driven by either of ball screw or linear motor and it is possible to change the mechanical properties of the machine such as grease viscosity of the table.

The power consumption is simulated by proposed simulation method based on the mathematical model of feed drive system and the simulated results are compared with the measured results of the experimental apparatus to confirm the validity of the simulated results.

In addition, it is clarified that the energy usages of the feed drive system. The energy losses of the feed drive system are divided into the loss of viscous friction, coulomb’s friction, servo amplifier, and motor. These energy losses are calculated by the proposed model. Then, it is investigated that the influence of the velocity and the friction to the power consumption of feed drive system experimentally.

As the results, it is confirmed that proposed simulation method can accurately predict the power consumption of the ball-screw feed drive system. It is also clarified that the friction energy loss of ball-screw drive is larger than one of linear motor drive, and the friction characteristics of linear guides influences the power consumption of linear motor drive system.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A089. doi:10.1115/IMECE2013-63546.

The advent of improved factory data collection offers a prime opportunity to continuously study and optimize factory operations. Although manufacturing optimization tools can be considered mainstream technology, most U.S. manufacturers do not take full advantage of such technology because of the time-intensive procedures required to manually develop models, deal with factory data acquisition problems, and resolve the incompatibility of factory and optimization data representations. Therefore, automated data acquisition, automated generation of production models, and the automated integration of data into the production models are required for any optimization analysis to be timely and cost effective. In this paper, we develop a system methodology and software framework for the optimization of production systems in a more efficient manner towards the goal of fully automated optimization. The case study of an automotive casting operation shows that a highly integrated approach enables the modeling and simulation of the complex casting operation in a responsive, cost-effective and exacting nature. Technology gaps and interim strategies will be discussed.

Topics: Optimization
Commentary by Dr. Valentin Fuster
2013;():V02AT02A090. doi:10.1115/IMECE2013-63628.

An effective and rigorous approach to determine optimum welding process parameters is implementation of advanced computer aided engineering (CAE) tool that integrates efficient optimization techniques and numerical welding simulation. In this paper, an automated computational methodology to determine optimum arc welding process control parameters is proposed. It is a coupled Genetic Algorithms (GA) and Finite Element (FE) based optimization method where GA directly utilizes output responses of FE based welding simulations for iterative optimization. Effectiveness of the method has been demonstrated by predicting optimum parameters of a lap joint specimen of two thin steel plates for minimum distortion. Three dimensional FE model has been developed to simulate the arc welding process and validated by experimental results. Subsequently, it is used by GA as the evaluation model for optimization. The optimization results show that such a CAE based method can predict optimum parameters successfully with limited effort and cost.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A091. doi:10.1115/IMECE2013-63745.

Numerous mathematical investigations of laser transformation hardening process have been conducted in the past three decades. The commonly used strategy of a sequentially coupled temperature-stress analysis is to first obtain temperature results from the temperature elements in a thermal loading model, followed by the calculations of thermal stresses from the structural elements under structural loading. Temperature is used as a predefined variable (varies with position and time only) as it is assumed to not change by the stress analysis. Fully coupled thermal-stress analysis is needed when the stress analysis is dependent on the temperature distribution and the temperature distribution depends on the stress solution This paper compares these two finite element (FE) based approaches for modeling temperature and thermal stress evolution in laser transformation hardening of hypoeutectoid steels. The dependence of temperature results on stresses and vice versa at higher temperatures involving significant inelastic strains has been demonstrated. Preliminary investigation reveals that under such circumstances thermal and mechanical solutions must be obtained simultaneously rather than sequentially.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A092. doi:10.1115/IMECE2013-63800.

Manufacturing process for complex and heterogeneous systems in sub-millimeter scale requires several discontinuous and expensive steps. Batch manufacturing approach via legacy semiconductor processes often do not provide a viable solution for such type of product development due to either their inherent limitations of monolithic and in-plane design or commercial unsuitability in cases of low to medium production volumes. Therefore, alternative approaches, such as microassembly techniques, are warranted for this type of advanced manufacturing requirements. However, lack of standards for design and unavailability of off-the-shelf robotic assembly systems, augmented with scaling of physics in micro-domain, eventually renders the highly iterative approach toward product development cycle cost-inefficient and time-consuming. In ordered to deal with this compounded problem in micromanufacturing, it becomes imperative that a holistic approach be employed that develops not only the product but also the system that is used to construct the same. In our work, we demonstrate this concurrent engineering approach through a novel, analytical framework, called as “Design for Multiscale Manufacturability (DfM2)”. This framework, built into an interactive software application, enables the user to estimate common manufacturability metrics such as process yield, cycle time, overall cost and device performance, which improves the decision making in production and paves the pathway to commercialization by reducing the time and cost to market. Furthermore, we also demonstrate the implementation of the DfM2 application in evaluating the manufacturing of heterogeneous microsystems by a custom developed modular and reconfigurable manufacturing cell (MRMC). A real case-study has been discussed for the implementation of the DfM2.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A093. doi:10.1115/IMECE2013-63982.

A recent development of cooling and lubrication technology for micromachining processes is the use of spray cooling. Atomization spray cooling systems have been shown to be more effective than traditional methods of cooling and lubrication for micromachining. Typical nozzle systems for atomization spray cooling incorporate the mixing of high speed air and atomized fluid. In a two-phase atomization spray cooling system, the atomized fluid can easily access the tool-workpiece interface, removing heat by water evaporation and lubricating the region by oil droplet spreading. The success of the system is determined in a large part by the nozzle design, which determines the droplet behavior at the cutting zone. In this study, computational fluid dynamics are used to investigate nozzle design and droplet delivery to the tool. An eccentric-angle nozzle design is evaluated through droplet flow modeling. This study focuses on the design parameters of initial droplet velocity, high speed air velocity, and the angle change between the two inlets. The system is modeled as a steady-state multiphase system without phase change. Droplet interaction with the continuous phase is dictated in the model by drag forces and fluid surface tension. The Lagragian method with a one-way coupling approach is used to analyze droplet delivery at the cutting zone. Following a factorial experimental design, deionized water droplets and a semi-synthetic cutting fluid are evaluated through model simulations. Statistical analysis of responses (droplet velocity at tool, tool positioning, and droplet density at tool) show that droplet velocity is crucial for the nozzle design and that modifying the parameters does not change droplet density in the cutting zone. Based on results, suggestions for future nozzle design are presented.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A094. doi:10.1115/IMECE2013-64387.

Friction stir welding is a relatively new advanced joining technique that requires minimal power input, ultimately leading to less inherent residual stresses and distortion. The process involves a spinning tool which first plunges into the surface of the, to be welded assembly and then traverses along the joint. Frictional heat is generated, softening the material at temperatures significantly below the melting temperature of the parent material. As the tool traverses along the joint at a predetermined speed, the assembly is joined by means of a plastic straining process. This advanced welding technology has been validated for various aluminium alloys but it is only recently, due to advances in tool technology, that the possibility of joining mild steel using friction stir welding has become a viable option. This study looks into friction stir welding of mild steel and develops simplified numerical methods for the prediction of thermal gradients, residual stresses and deformation. In principle the process modelling requires a multi-disciplinary approach involving coupled thermo-fluid, microstructural-structural modelling process. Much of the latest thermo-mechanical studies of friction stir welding rely on a number of over simplifications particularly related to the heat flux distribution across the tool shoulder, and also on the backing plate boundary conditions. The objective of this paper is to scrutinise the effects of modelling in more detail and establish the most important factors leading to accurate yet computationally efficient prediction of thermal gradients and inherent residual stresses. The results show that both the heat input and heat loss modelling, due to heat dissipation to the surroundings, are crucial for the determination of the final inherent welding residual stresses. The heat generated is modelled through a predefined linear heat flux variation across the tool shoulder. However if a more precise and localized residual stress information is sought, a full thermo-fluid-structural analysis is required. This is time consuming and probably does not give significant information on manufacturing optimization. On the other hand, simplified global solutions offer the possibility to optimise friction stir welding parameters and boundary conditions during the preliminary stages of the development of the fabrication procedures, at relatively minimal time and processing power. This work is financed under the European Commission in Call FP7-SST-2012-RTD-1 High Integrity Low Distortion Assembly (HILDA) project.

Topics: Friction , Steel , Welding , Modeling
Commentary by Dr. Valentin Fuster
2013;():V02AT02A095. doi:10.1115/IMECE2013-64512.

Every series of manufactured products has geometric variation. Variation can lead to products that are difficult to assemble or products not fulfilling functional or aesthetical requirements. In this paper, we will consider the effects of welding in variation simulation. Earlier work that have been combining variation simulation with welding simulation have either applied distortion based on nominal welding conditions onto the variation simulation result, hence loosing combination effects, or have used transient thermo-elasto-plastic simulation, which can be very time consuming since the number of runs required for statistical accuracy can be high. Here, we will present a new method to include the effects of welding in variation simulation. It is based on a technique that uses a thermo-elastic model, which previously has been shown to give distortion prediction within reasonable accuracy. This technique is suited for variation simulations due to the relative short computation times compared to conventional transient thermo-elasto-plastic simulations of welding phenomena. In a case study, it is shown that the presented method is able to give good predictions of both welding distortion and variation of welding distortions compared to transient thermo-elasto-plastic simulations.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A096. doi:10.1115/IMECE2013-64801.

Numerical analysis for a two dimensional case of two–phase fluid flow has been performed to investigate droplet impact, deformation for a droplet train. The purpose of this investigation is to study the phenomenon of liquid droplet impact on a liquid film created by a flattened droplet and the consequent deformation of the film while merging and advancing of the moving front of the film, during the manufacturing processes with jetting technology such as a direct printing process and inkjet printing. This investigation focuses on the analysis of interface tracking and the change of shape for an impacted droplet of a dispensed material. Investigations have been made on the performance of an adaptive quadtree spatial discretization with geometrical Volume–Of–Fluid (VOF) interface representation, continuum–surface–force surface tension formulation and height-function curvature estimation for interface tracking during droplet impact deformation and coalescence of droplet and liquid film produced by flattened droplets to form a printed line. Gerris flow solver, an open source finite volume code, has been used for the numerical analysis which uses a quadtree based adaptive mesh refinement for 2D. The results have been compared with an experimental result from the literature. The investigation has been performed for Reynolds number, Re of 21.1; Weber number, We of 93.8, and contact angle, θ of 30°. For the experimental result considered, the frequency of jetting is 12 kHz.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A097. doi:10.1115/IMECE2013-64933.

Particulate media are ubiquitous in modern manufacturing processes. These include spray-forming, abrasive finishing, and sintering based processes amongst others. All of these processes involve a flowing stream of discrete, particulate media. For these processes, the aggregate behavior originating from the individual particle or grain dynamics is of critical importance from a process engineering perspective. The discrete nature of the media poses unique challenges in formulating direct continuum theories. This motivates investigating appropriate discrete computational techniques. In this paper, we present a computer simulation framework based on collision driven particle dynamics to investigate the engineering of such manufacturing processes. This is part of an ongoing work on developing a general-purpose computer simulation tool to analyze the dynamics of particulate and granular media in engineering applications. This paper presents the overall framework and the underlying physical models. In particular, our focus is on modeling individual particle-based phenomena (including collisions, heat-exchange, and energy loss) and deriving the aggregate response of the media from individual particle dynamics. The technique is demonstrated using a numerical example for a spray coating deposition process. This example tracks the particulate behavior from the nozzle opening downstream until impact with substrate. Such investigations are useful to understand the effect of process parameters on the engineered output — which in this case entails the properties of the surface coating. The simulation is found to be reasonable in performance time.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A098. doi:10.1115/IMECE2013-64970.

The economical production of high-value, low-volume, machined components is an important subtopic of advanced manufacturing. Bar feeders, a well-established technology for adding a high degree of automation to CNC turning centers by feeding 12′ lengths of stock through the machine spindle, have limitations in this realm. They rely on supporting the entire length of the stock in a continuous fluid bearing in order to suppress potential vibrations. Although this results in excellent vibration suppression, long tooling changeovers make them impractical for small batch sizes. Additionally, the expense of the tooling can render them cost-prohibitive. Thus a bar feeder technology is desired that provides comparable vibration suppression for a wide variety of stock sizes without the need for size-specific tooling changes. In this, a movable point support having tunable viscoelastic properties is studied for controlling the vibration of varying lengths of bar stock in a given speed range. The transverse vibration of mounted bar stock is modeled as a Bernoulli-Euler beam. The effects of the support position, viscoelastic model, and their associated parameters on the resonant frequencies, damping ratios, and vibration response of the bar stock are studied. Such a study will be instrumental in developing passive/active vibration control strategies for future bar feeders.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A099. doi:10.1115/IMECE2013-65483.

The CNC machining has been one of the most recurrent processes used for finishing NNS components. This paper presents a new method for the generation of tool paths for machining 3D NNS models. The proposed approach comprises two machining stages: rough cut and finish cut, and three types of cutting tools: ball-end mill, flat-end mill and fillet-end mill. The proposed tool path generation algorithm is based on: (1) approximation of the model surfaces by points using slice planes and visibility analysis, (2) accessibility analysis of the tool, (3) approximation error and tolerance evaluation, (4) collision analysis of tool and tool holder. The tools paths generated are exported as a CNC program. The implementation was carried out in C++ using the ACIS® geometric modeling kernel to support the required geometric operations. To prove the effectiveness of the system several models with variable geometric complexity were tested. The results have shown that the proposed system is effective and therefore can be used to generate the tool paths required for finishing 3D NNS components.

Topics: Finishing , Shapes
Commentary by Dr. Valentin Fuster
2013;():V02AT02A100. doi:10.1115/IMECE2013-65651.

Molecular dynamics (MD) simulation is an effective numerical approach to study nano-indentation processes on many intriguing issues such as material deformation response, mechanical properties of materials such as hardness, and phase transformation. Lubrication is an important consideration for many types of tool-based manufacturing processes including indentation, scratching, and machining. It adds complexity to the system, affects the friction condition, and changes material behavior. For indentation process, the existence of lubrication liquid may also influence mechanical property measurements. Unfortunately, lubrication effect in tool-material interactions has not been addressed by the existing MD simulation literature. In this study, we construct 3D MD simulation models for nano-indentation of single crystal copper using a cylindrical diamond indenter under wet and dry conditions, respectively. The wet condition is realized by adding water molecules to the simulation system to separate the indenter and copper surface, while the dry condition does not have water molecule in the system. The tribological effects of water are investigated at two different indentation speeds. The results indicate that wet indentation with water eliminates the reverse indentation size effect, which however occurs in the dry nano-indentation process. Also, the existence of water results in higher computed hardness values under low indentation loads. Meanwhile, friction forces along the indenter/work interface are reduced under wet indentation condition. It is found that lubrication is helpful for preserving the size and shape of residual indentation. In addition, the increase of indentation speed increases the indentation force.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A101. doi:10.1115/IMECE2013-65811.

Due to its vast applications and stochastic nature, grinding has been the subject of investigations and modifications for decades. Applying ultrasonic vibration in grinding has been a successful innovation introducing benefits such as reduced forces and temperature, improved surface quality, and making higher removal rates possible. In this work a set-up is developed for utilizing ultrasonic vibrations in cylindrical grinding. This is done by rotating and simultaneously vibrating the workpiece material. The set-up is used for cylindrical grinding of Alumina-zirconia ceramic as a difficult-to-grind and widely used industrial ceramic. Optimized parameters for efficient grinding and surface characteristics of the ground ceramic are investigated and the effects of ultrasonic vibration are declared.

Topics: Ceramics , Grinding
Commentary by Dr. Valentin Fuster
2013;():V02AT02A102. doi:10.1115/IMECE2013-66433.

Advanced Physical Vapor Deposition (PVD) techniques are available that produce thin-film coatings with adaptive nano-structure and nano-chemistry. However, such components are manufactured through trial-and-error methods or in repeated small increments due to a lack of adequate knowledge of the underlying physics. Successful computational modeling of PVD technologies would allow coatings to be designed before fabrication, substantially improving manufacturing potential and efficiency.

Previous PVD modeling efforts have utilized three different physical models depending on the expected manufacturing pressure: continuum mechanics for high pressure flows, Direct Simulation Monte Carlo (DSMC) modeling for intermediate pressure flows or free-molecular (FM) dynamics for low pressure flows. However, preliminary calculations of the evaporation process have shown that a multi-physics fluidic solver that includes all three models may be required to accurately simulate PVD coating processes. This is due to the high vacuum and intermolecular forces present in vapor metals which cause a dense continuum region to form immediately after evaporation and expands to a rarefied region before depositing on the target surface.

This paper seeks to understand the effect flow regime selection has on the predicted deposition profile of PVD processes. The model is based on experiments performed at the Electron-Beam PVD (EB-PVD) laboratory at the Applied Research Lab at Penn State. CFD, DSMC and FM models are separately used to simulate a coating process and the deposition profiles are compared. The mass deposition rates and overall flow fields of each model are compared to determine if the underlying physics significantly alter the predicted coating profile. Conclusions are drawn on the appropriate selection of fluid physics for future PVD simulations.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A103. doi:10.1115/IMECE2013-66761.

In this study, a nozzle has been designed in order to produce metal powder via the method of gas atomization. The design has been performed in two stages. At the first stage of design, the size and geometry of the nozzle have been determined using empirical relations as a pre-design. At the second stage, a parametrical analysis has been done using a CFD code. As a parametrical study, the effects of nozzle exit angle, throat distance and protrusion length on pressure and flow velocity at the nozzle exit are investigated with the numerical model. Appropriate values for the investigated parameters have been determined to get maximum pressure in vacuum condition at the tip of the melt. The nozzle has been designed based on the determined parameters.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A104. doi:10.1115/IMECE2013-66777.

In this study, a gas atomization nozzle for metal powder production has been designed and modeled numerically. The design has been performed in two stages. At the first stage of the design, the size and geometry of the nozzle have been developed to obtain circulated flow through the nozzle as a pre-design. At the second stage, a parametrical analysis has been done using a CFD code. The geometry of the nozzle has been changed and the effect of geometric parameters was determined to find out the more efficient nozzle design parameters. Gas behavior at the nozzle exit and effect of the gas on the melt delivery tube tip has been investigated. Appropriate values for the investigated parameters have been determined to get maximum pressure in vacuum condition at the tip of the melt. The pressure observed at the melt delivery tube was compared with the experimental melt tip pressure data. These results suggest that the CFD solutions can be used in the design of the nozzle. Thus, the lower cost and shorter time would be possible to develop highly efficient nozzle geometry.

Commentary by Dr. Valentin Fuster
2013;():V02AT02A105. doi:10.1115/IMECE2013-66807.

This paper investigates effects of natural and Marangoni convection on the resultant solidification microstructure in the scanning laser epitaxy (SLE) process. SLE is a laser-based additive manufacturing process that is being developed at the Georgia Institute of Technology for the additive manufacturing of nickel-base superalloys components with equiaxed, directionally-solidified or single-crystal microstructures through the laser melting of alloy powders onto superalloy substrates. A combined thermal and fluid flow model of the system simulates a heat source moving over a powder bed and dynamically adjusts the thermophysical property values. The geometrical and thermal parameters of the simulated laser melt pool are used to predict the solidification behavior of the alloy. The effects of natural and Marangoni convection on the resultant microstructure are evaluated through comparison with a pure conduction model. Inclusion of Marangoni effect produces shallower melt pools compared to a pure conduction model. A detailed flow analysis provides insights into the flow characteristics of the powder, the structure of rotational vortices created in the melt pool, and the solidification phenomena in the melt pool. The modeling results are compared with measurements and observation through real-time thermal imaging and video microscopy to understand the flow phenomenon.

In contrast to the single weld-bead approach, the raster scan in SLE allows every position in melt pool to be visited twice by the solid-liquid interface as the scan source progresses. To properly address this situation, time tracking is incorporated into the model to correctly couple the microstructure prediction model. An optimization study is carried out to evaluate the critical values of the transition parameters that govern the columnar-to-equiaxed transition (CET) and the oriented-to-misoriented (OMT) transition. This work is sponsored by the Office of Naval Research through grant N00014-11-1-0670.

Commentary by Dr. Valentin Fuster

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