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Advances in Biomedical Manufacturing

2009;():1-8. doi:10.1115/MSEC2009-84238.

Current biocompatible metals such as steel and titanium alloys have excellent corrosive properties and superior strengths. However, their strengths are often too high and as a result have a negative effect on the body. Therefore, Magnesium (Mg) alloys with relatively low strengths are ideal biocompatible metallic materials. The problem with Mg implants is how to control corrosion rates so that the degradation of Mg implants may match with bone growth. The high compressive residual stress induced by laser shock peening (LSP) has a great potential to slow down the corrosion rate. LSP is a known surface treatment method to impart compressive residual stress in subsurface of a metal. Therefore, LSP was initiated in this study to investigate surface topography and integrity produced by peening a Mg alloy. A 3D semi-infinite simulation has also been developed to predict the topography and residual stress fields produced by sequential peening. The dynamic mechanical behavior was modeled using a user material subroutine of the internal state variable plasticity model. The temporal and spatial peening pressure was modeled using a user load subroutine. The simulated dent agrees with the measured dent topography in terms of profile and depth. Sequential peening was found to increase the tensile pile up region which is critical to tribological applications. The predicted residual stress profiles are also presented.

Commentary by Dr. Valentin Fuster
2009;():9-16. doi:10.1115/MSEC2009-84374.

Manufacturing process-induced damage to cells is of significant importance in biomaterial direct writing. For safe and reproducible cell direct writing, the process-induced cell damage must be understood in addition to biological property research. The objective of this study is to investigate the cell membrane stability under the external normal pressure. It is performed by studying the dipalmitoylphosphatidylcholine (DPPC) bilayer behavior under different normal pressures using molecular dynamics (MD). It is found that as the normal pressure increases, the thickness of DPPC bilayer decreases and the area of per DPPC molecule increases; and as the normal pressure increases, the rupture force to break the bilayer structure decreases, which can also be explained by the change of free energy difference before and after rupture under different normal pressures. This study serves as the first step towards understanding of the cell damage mechanism in cell direct writing.

Commentary by Dr. Valentin Fuster

Bioenergy Manufacturing

2009;():17-23. doi:10.1115/MSEC2009-84090.

Current US transportation sector mainly relies on liquid hydrocarbon derived from petroleum and about 60% of the petroleum consumed is from areas where supply may be disturbed by regional instability. This has led to serious concerns on global warming and energy security. To address these issues, numerous alternative energy carriers have been proposed. Among them, second generation biofuel is one of the most promising technologies. Gasification based thermo-chemical conversion can utilize a wide range of biomass wastes and residues and bring flexibility to both feedstock and production sides of a plan. Thus it presents an attractive technical route. In this paper, a flexible feedstock thermo-chemical ethanol production process is investigated. This research focuses mainly on the evaluation of the feasibility of the process through numerical simulation. An existing thermo-chemical ethanol production model developed by NREL has been updated to handle the cases when different biomass feedstock and feedstock combinations are used. It is found that the ethanol yield is positively linear proportional to the feedstock feeding rate, while the total conversion efficiency is negatively proportional to the feeding rate. To demonstrate a feedstock management strategy, a plant located near a major city with a population of 200,000 and above is considered and MSW, corn stover and wood chips are selected as potential feedstock. Simulation results indicate that with wood chips as the backup feedstock the plant can be operated under extreme conditions when corn stover availability is significantly reduced without major equipment modification.

Commentary by Dr. Valentin Fuster
2009;():25-31. doi:10.1115/MSEC2009-84205.

Biofuels produced from cellulosic biomass (such as the fibrous, woody, and generally inedible portions of plant matter) can significantly reduce the nation’s dependence on foreign oil, create new jobs, improve rural economies, reduce greenhouse gas emissions, and improve national security. However, in the U.S., there are currently no cellulosic biofuel plants in commercial production. Several technical barriers have hindered large-scale cost-effective manufacturing of cellulosic biofuels. One such barrier is related to the low density of cellulosic feedstocks, causing their transportation and storage to be very expensive. Pelleting biomass can increase the overall efficiency by utilizing existing transportation infrastructure and storage systems for mega-ton quantities. If biomass is pelleted, it can be handled and transported with existing grain handling equipment in the field, on the road, and at the central biorefinery. This paper presents experimental study on ultrasonic vibration assisted pelleting of cellulosic feedstocks. The results show that ultrasonic vibration assistance could increase the mechanical strength of pellets by more than six times and the density by 50%.

Topics: Biomass , Vibration
Commentary by Dr. Valentin Fuster
2009;():33-41. doi:10.1115/MSEC2009-84222.

Five methods, namely adsorption, covalent binding, encapsulation, entrapment, and cross-linking, for algae immobilization were briefly reviewed in this article. The immobilization capabilities of four solid carrier materials (polystyrene, polyurethane, polyethylene, and cross-linked polyethylene) with two algal species (Nannochloropsis oculata and Scendesmus dimorphus) were tested. After 14 days of immobilization, polystyrene foam showed the best cell attachment and was covered by algae cells not only on the outer surface but also inside the porous spaces of the carrier. The cross-linked polyethylene also showed good attachment and growth of algae cells. Between the two algae species, N. oculata showed better cell attachment than S. dimorphus on all four materials indicating that cell characteristics played an important role in cell-surface interactions. The Derjaguin & Landau and Verwey & Overbeek (DLVO) theory was applied to understand the interaction mechanism and predicted attachment trends were found qualitatively accurate in matching the experimental results.

Commentary by Dr. Valentin Fuster

Environmentally Sustainable Manufacturing Processes and Systems

2009;():43-48. doi:10.1115/MSEC2009-84026.

This paper investigates the influence of supercritical carbon dioxide (scCO2 ) metalworking fluids on tool wear in two automotive manufacturing processes. scCO2 is a low-cost minimum quantity lubrication (MQL) system with excellent cooling characteristics. In valve seat machining of sintered steel with cubic boron nitride (CBN) inserts, scCO2 reduced tool wear by up to 25% and cutting forces by 10% when compared with the benchmark water-based flood metalworking fluid currently used in production operations. In end milling of compacted graphite iron (CGI) with uncoated carbide inserts, scCO2 reduced tool wear by up to 50% when compared with the currently used metalworking fluid. These results are consistent with those from other applications that show scCO2-based metalworking fluids have the potential to reduce tool wear and cutting forces when compared with commonly used water-based metalworking fluids. At the same time scCO2 is environmentally benign, eliminates metalworking fluid maintenance and disposal, and removes the major health risks associated with today’s metalworking fluids.

Commentary by Dr. Valentin Fuster
2009;():49-55. doi:10.1115/MSEC2009-84065.

Rapid access to or generation of life cycle information is a potentially valuable tool for the design of products to meet the needs of sustainability improvement. A new approach is developed to use the manufacturing unit process, commonly outlined in manufacturing process taxonomy systems, as the basis for life cycle inventory. This will initially involve 50–70 unit processes from the taxonomy and will generate energy and mass profiles for each unit process life cycle (uplci). These uplci can be adjusted for each case to include the major variables affecting such operations as related to any specific product. The sum of the performance of a sequence of uplci thus provides the life cycle of the specific product from a defined set of plant process inputs.

Topics: Manufacturing , Cycles
Commentary by Dr. Valentin Fuster
2009;():57-66. doi:10.1115/MSEC2009-84107.

Microfiltration is an in-process recycling method that shows great potential to extend fluid life and reduce bacterial concentrations in synthetic and semi-synthetic metalworking fluids (MWFs). The primary problem facing this use of microfiltration is membrane fouling, which is the blocking of membrane pores causing reduced flux. In this paper a fluid dynamic model of partial and complete blocking in sintered alumina membranes is developed that includes hydrodynamic, electrostatic, and Brownian forces. Model simulations are employed to study the impact of electrostatic and Brownian motion forces on the progression of partial blocking. The simulations also examine the effects of fluid velocity, particle size, and particle surface potential. The inclusion of electrostatic and Brownian forces is shown to significantly impact the progression of the partial blocking mechanism. The addition of a strong inter-particle electrostatic force is shown to eliminate the partial blocking build-up of small particles due to the presence of the repulsive forces between the particles. As a result, the time to complete blocking of the test pore was lengthened, suggesting that flux decline is reduced in the presence of electrostatic forces. Brownian motion is shown to have a large impact at low fluid velocities. The most effective parameter set is a low fluid velocity, small particle sizes, high microemulsion surface potential, and high membrane surface potential.

Commentary by Dr. Valentin Fuster
2009;():67-75. doi:10.1115/MSEC2009-84140.

Carbon Dioxide is an industrial byproduct that has been proposed as an alternative metalworking fluid (MWF) carrier with lower environmental impacts and better cooling potential than existing MWFs. This paper investigates the heat removal and tool life effects of rapidly expanding supercritical CO2 (scCO2 )-based MWFs relative to MWFs delivered as a flood of semi-synthetic emulsion or as minimum quantity lubrication (MQL) sprays. When cutting both compacted graphite iron (CGI) and titanium, tool wear was most effectively controlled using the scCO2 -based MWF compared with the other MWFs. Analysis in this paper suggests that the performance benefit imparted by rapidly expanding scCO2 appears to be related to both the cooling potential and penetration of the sprays into the cutting zone. High-pressure gas sprays have lower viscosity and higher velocity than conventional MWFs. An experiment in which the spray direction was varied clearly demonstrated the importance of spray penetration in tool wear suppression. The type of gas spray is also a significant factor in tool wear suppression. For instance, a spray of N2 delivered under similar conditions to CO2 effectively reduced tool wear relative to water based fluids, but not as much as CO2 . This result is particularly relevant for MQL sprays which are shown to not cool nearly as effectively as scCO2 MWFs. These results inform development of scCO2 -based MWFs in other machining operations, and provide insight into the optimization of scCO2 MWF delivery.

Commentary by Dr. Valentin Fuster
2009;():77-85. doi:10.1115/MSEC2009-84159.

This paper presents a computational framework for calculating turning energy for parts and assemblies, at two levels — early design stage and manufacturing stage. At the early design stage such energy estimation can be used to redesign the part and assemblies for manufacturing energy efficiency. At the manufacturing stage, allocation of resources based on energy efficient process planning and scheduling aids in reducing the carbon emissions of the product due to manufacturing energy production. For computing the turning energy, at the early design stage, first removal volume for turning operations for a part is identified. Then, material data and the removal volume are used to calculate a range of turning energy for manufacturing the part. If dealing with an assembly, then the above computations are applied to each individual parts and total turning energy is computed for the assembly. Energy hogging parts/features are identified based on percent contribution, which is then used to suggest parts for re-design. Application of statistical analysis and allocation of turning energy for identifying re-design parts is also explored. Re-design at the early design stage is performed at two levels — form (geometry and shape) and material. At the manufacturing stage, turning energy calculations can be utilized for optimizing the process plans. Although the framework presented in this paper is applied only to turned parts and assemblies, it can also be applied to machined parts and assemblies.

Topics: Turning , Design
Commentary by Dr. Valentin Fuster
2009;():87-96. doi:10.1115/MSEC2009-84171.

End-of-life product recovery operations require performance improvement to be viable in an industrial environment. A genetic algorithm (GA) is proposed to optimize end-of-life partial disassembly decisions based on disassembly costs, revenues, and environmental impacts. Facilitating disassembly optimization with costs, revenues, and environmental impacts is necessary to enhance sustainable manufacturing through value recovery. End-of-life products may not warrant disassembly past a unique disassembly stage due to limited recovered component market demand and minimal material recovery value. Remanufacturing is introduced into disassembly sequence optimization in the proposed GA as an alternative to recycling, reuse, and disposal. The proposed GA’s performance is first verified through optimizing partial disassembly sequences considering costs and environmental impacts independently. Extension to a multi-objective case concerning costs, revenues, and impacts is achieved by specifying a new set of multi-objective crossover probabilities from independent crossover probabilities.

Topics: Optimization
Commentary by Dr. Valentin Fuster
2009;():97-105. doi:10.1115/MSEC2009-84206.

Laser assisted manufacturing (LAM) processes, when compared with traditional manufacturing processes, have the potential to reduce cost, increase surface finish, extend part/tool life, and expand the range of manufacturable materials. However, very limited research has been done to evaluate the environmental performance of laser assisted processes and it is generally not clear how LAM processes compare with traditional methods. This paper conducts case studies on two representative laser based processes, i.e. laser shock peening of 7065 T7351 Aluminum and laser assisted turning of compacted graphite iron. Life cycle assessment is used to benchmark the environmental performance of these two processes to conventional processes, i.e. shot peening and dry turning, respectively. The life cycle inventory of both the laser based processes and conventional processes are developed using SimaPro v7.1 and Ecoinvent 2.0 and life cycle impact assessment is performed using US EPA TRACI. It is found that environmental performance of laser based processes varies significantly from process to process due to materials and energy consumption. Laser shock peening of aluminum has much better performance when over all environmental impact categories considered. Contribution analysis indicates that this is mainly due to the fact that laser shock peening does not need shot medium and at the same time significantly extends fatigue life of the workpiece. However, due to high electricity consumption and use of absorptive paint, laser assisted turning of compacted graphite iron has much higher environmental impacts than traditional dry turning, even after extending the tool life significantly.

Commentary by Dr. Valentin Fuster
2009;():107-115. doi:10.1115/MSEC2009-84220.

Current practice of emission estimate for ocean-going vessels largely relies on the conventional propeller law for determining power consumption. This practice tends to underestimate the actual emission when sea states and winds are ignored. This paper presents an evaluation of two approaches on the prediction of power of a container vessel. The first approach estimates vessel power as a function of the vessel speed according to the propeller law. While the propeller law approach is cost-effective and time-saving in computing vessel propulsion power, it generally under-estimates vessel propulsion power due to the omission of many other influencing factors including vessel course, engine model, ocean states and weather conditions. The second approach derives vessel propulsion power as a function of the vessel speed and resistance forces. The propulsion power required for a particular vessel behavior is determined based on vessel towing resistance, added resistance from waves and winds, and a variety of propeller and hull dependent efficiencies. Because of the incorporation of external factors, this approach should be more accurate than the propeller law in reflecting the actual vessel power requirement. Comparative analysis is conducted among the two estimate results and real measurement data on engine power output. The results clearly show that power estimated from the propeller law underestimate the vessel propulsion power and the gap increases much faster for higher vessel speeds. Power estimate from the second approach provides more accurate results as they greatly match the measured power values. The ups and downs of the prediction results precisely reflect real power variation along with speed changes. Improved power prediction leads to more reliable emission inventory calculation. However, the improvement of accuracy should be balanced with the increased requirement on data sources and computing efforts.

Topics: Vessels , Emissions
Commentary by Dr. Valentin Fuster
2009;():117-126. doi:10.1115/MSEC2009-84224.

The stuffed toy market is quite large, with some manufacturers earning nearly half a billion dollars in revenue per year. However, the vast majority of manufacturers do not currently employ sustainable manufacturing techniques. This paper documents the development of a cost-effective stuffed product by placing an emphasis on sustainability within the design process while maintaining the user appeal of a traditional teddy bear. Specifications were determined by analyzing each of the four stages of the product timeline (extraction, manufacture, use, and disposal) to ensure that sustainability was considered throughout the lifecycle of the product. Material choice was a main focus of the extraction stage, and limiting new material usage was an important goal. Considerations for the manufacturing stage included carbon dioxide produced, waste generated, toxicity, and packaging. Specifications regarding the consumer’s use of the product included user appeal, stain resistance, durability, price, and safety concerns. Objectives of the last stage, disposal, included plans to minimize the amount of material sent to landfills by making the product easier to store, improving ease of recycling, and reducing transportation required. These specifications, importance ratings, marginal values, and ideal values are discussed. While investigating more sustainable manufacturing practices, many solutions were found, and the practicality of these solutions was investigated. By incorporating these solutions, the product — Sustain-A-Bear™ — met specifications, embodied sustainability, and also proved cost competitive. Once specification-level analysis was complete, multiple bears were constructed, both to create a baseline for comparison with standard stuffed animal assembly and also to aid in the development of a more sustainable assembly process. Through the use of ultrasonic welding for material bonding to thermally weld materials together and through the use of specialized platens, the bear was assembled from PET fleece (recycled from plastic soda bottles) using significantly less time and energy than that required to sew a bear together. Part reduction and shape simplification also aided bear assembly throughput. Furthermore, tensile testing on an Instron machine yielded results better than those resulting from sewing, owing largely to the reduction of stress concentrations. Finally, overall cost analysis indicates that stuffed animals made in this fashion could, in fact, be affordably made in the United States.

Commentary by Dr. Valentin Fuster
2009;():127-133. doi:10.1115/MSEC2009-84272.

With increasing environmental regulations and waste management costs, environmentally conscious design and manufacturing (ECDM) and surplus asset recovery are becoming a more attractive approach to solve environmental problems. Any company that owns a collection of PCs, printers and other electronic accessories probably needs to manage these assets more effectively, but currently there is a lack of tools for effective management. Therefore, this paper discusses, from the viewpoint of an enterprise dealing with end-of-life electronic products, the recycling processes according to literature, and derives an integrated model on surplus asset management and environmental impact analysis. The primary objective of the model is to develop a certain tool for managing surplus asset within a corporate office and generate a decision making tool for those who are concerned with the environmental issues in the design or recycling phase. Based on this model, a prototype system is introduced in detail in this paper.

Commentary by Dr. Valentin Fuster
2009;():135-144. doi:10.1115/MSEC2009-84292.

The use of Unmanned Aerial Vehicles (UAVs) has become widespread and is ever increasing. There are plans for utilizing the UAVs for the military as well as the humanitarian and law enforcement missions such as flood and hurricane relief, firefighting, drug trafficking control, and so on. The number of UAVs is likely to continue to grow exponentially in the near future and there is a great need for the environmentally conscious design and manufacturing efforts in the UAV market. The authors are developing an integrated approach to bring the high fidelity Computer Aided Design and Engineering (CAD/E) tools to the preliminary design phase for designing new aircraft. In this paper, this approach is extended to include the environmentally conscious material selection when designing a UAV wing for the medium altitude long endurance mission. Finite Element Analysis is used to determine the material needed for the wing and the computed weights are supplied to the spreadsheet for calculating environmental impacts of different materials selected for the wing design. This spreadsheet has been developed based on the data in the Lifecycle Assessment software package SimaPro/Ecoinvent. The study demonstrates how to integrate environmental considerations into the preliminary UAV design using high fidelity models.

Commentary by Dr. Valentin Fuster
2009;():145-153. doi:10.1115/MSEC2009-84308.

Nano- and microtechnologies offer many benefits to society and promise the prospect of paradigm shifts on many technological fronts, including health care, alternative energy production, and efficient chemical processing. Current manufacturing processes for the production of nano- and microscale products, however, are energy and waste-intensive — requiring energy and creating wastes/emissions at orders of magnitude greater than traditional production. Therefore, research is needed to quantify environmental performance improvements in nano- and microproduction technologies, nickel nanoparticle (NiNP) deposition is compared with more traditional nickel phosphorus (NiP) electroplating for facilitating diffusion brazing of arrayed microfluidics. These two technologies are analyzed on a functional basis from an environmental perspective. Potential areas of improvement and future research opportunities are identified and discussed.

Commentary by Dr. Valentin Fuster
2009;():155-160. doi:10.1115/MSEC2009-84309.

People that work on the development of mechatronic products do not have enough data related to the end of the product lifecycle when making decisions related to the product design. Sustainable design tools in Product Lifecycle Management (PLM) systems could enable more sustainable designs with ‘greener’ decision-making. PLM tools, which are supporting designs of mechatronic products, are lacking more consideration about the product’s overall lifecycle ecological footprint. Most decisions that are made during the design phase are based on costs of materials and processes that are involved in development and manufacturing, not to the service, reuse, recycling and disposal of such products. This study will investigate the possibility of including the data related to the end of the product lifecycle. Integrating green design tools into the PLM systems would help mechatronic engineers to develop more sustainable designs. This paper will investigate the current state of the art in the area of Product Lifecycle Management systems that support design and realization of mechatronic projects. It discusses some ideas that can be used for determining a framework for data capturing of electro-mechanical product related data. This would connect decisions in earlier phases with the ones in final stages of a product lifecycle. This data can be used for the environmental footprint determination.

Commentary by Dr. Valentin Fuster
2009;():161-167. doi:10.1115/MSEC2009-84339.

The largest amount of energy consumption in an automotive assembly plant is in paint shop. Optimizing the energy usage in paint shops will result in maximum energy savings. Instead of inventing new chemicals, new painting processes or new control systems in painting booths and ovens, our research focuses on developing an optimal scheduling procedure of vehicle sequence to achieve the goal of energy reduction. Specifically, by selecting appropriate batch and sequence policies, the paint quality can be improved and repaints can be reduced so that less material and energy will be consumed. It is shown that such scheduling and control method can lead to significant energy savings with no extra investment, nor changes to existing painting processes.

Commentary by Dr. Valentin Fuster
2009;():169-177. doi:10.1115/MSEC2009-84356.

The issue of environmental sustainability, which is unprecedented in both magnitude and complexity, presents one of the biggest challenges faced by modern society. Engineers, including mechanical engineers, can make significant contribution to the development of solutions to this problem by designing products and processes that are more environmentally sustainable. It is critical that engineers take a paradigm shift of product design i.e. from cost and performance centered to balance of economic, environmental, and societal consideration. Although there have been quite a few design for environment (DfE, or ecodesign) tools developed, so far these tools have only achieved limited industrial penetration: they are either too qualitative/subjective to be used by designers with limited experiences, or too quantitative, costly and time consuming and thus cannot be used during the design process specially during the early design stage. This paper develops a novel, semi-quantitative ecodesign tool that targets specially on early design process. The new tool is a combination of environmental life cycle assessment, working knowledge model, and visual tools such as QFD, functional-component matrix, and Pugh chart. Redesign of staplers is selected as a case study to demonstrate the use of the proposed tool. Efforts are on going to confirm that the new design generated using this new tool does have improved environmental performance.

Commentary by Dr. Valentin Fuster
2009;():179-186. doi:10.1115/MSEC2009-84365.

Product sustainability assessment and evaluation metrics are mostly concerned with product usage and disposal only towards the end of the product lifecycle. Common examples include the energy efficiency and environmentally friendliness definitions used for consumer products. However, a product has already left a ‘footprint’ during its design, manufacturing, production and distribution stages. The energy efficiency and ecological footprint of products in manufacturing processes, operations and facility usages has been overlooked for many decades. In this study, we aim to establish a preliminary framework for defining metrics that may help capture energy efficiency and ecological footprint of discrete parts and products during manufacturing activities to control and improve the sustainability.

Commentary by Dr. Valentin Fuster
2009;():187-191. doi:10.1115/MSEC2009-84381.

Based on consideration of mechanics of chip formation, it is shown that the application of a controlled modulation fundamentally changes the nature of the extreme deformation underlying chip formation, and the severe contact conditions at the tool-chip interface. Important consequences are significant reduction in the energy of chip formation, and control of chip shape and size for improved chip management. Implementation of modulation-assisted machining for industrial machining processes is discussed.

Topics: Tribology , Machining
Commentary by Dr. Valentin Fuster

Advances in Manufacturing Process Planning and Scheduling

2009;():193-199. doi:10.1115/MSEC2009-84145.

This paper studies the effectiveness of using parallel Ant Colony Optimization for sequence dependent parallel machine scheduling on a Graphics Processing Unit (GPU) hardware platform. Parallel machine scheduling is a traditional NP-hard combinatorial optimization problem. In this research, a hybrid ant colony optimization method that combines the ‘Apparent Tardiness Cost with Setups’ (ATCS) dispatching rule with massive ants is proposed to solve the parallel machine scheduling problem quickly and efficiently. The computational results demonstrate that the proposed method is effective and solve the problems order of magnitude faster with a GPU accelerated implementation.

Commentary by Dr. Valentin Fuster
2009;():201-210. doi:10.1115/MSEC2009-84316.

Closed-Loop Manufacturing (CLM) techniques include machine tool self-checks, automated setups, tool measurement, in-process probing with process adjustment, on-machine final inspection, data collection and data analysis. All of these elements and more are utilized to collect data in a mostly automated fashion to subsequently correct and adjust undesired conditions that can affect part quality. Inspection process planning plays an essential part of CLM. As G&M codes that contains low-level information or vendor-specific bespoke routines is the primary programming language, inspection process planning is mostly isolated from machining process planning. With the development of new data model standards such as STEP and STEP-NC providing high-level product information for the entire manufacturing chain, it is conceivable that both machining and inspection process planning are considered hand-in-hand to generate optimal machining and inspection sequences with real-time measurement feedback for the CLM scenario. This paper introduces an reactive process planning system architecture that incorporates machining, inspection, and feedback. In order to provide real-time inspection feedback, On-Machine Measurement (OMM) is chosen to carry out inspection operations. Implementation of the proposed architecture has been partially carried out with newly developed data model and interpreter. A case study testified the feasibility of the proposed architecture.

Commentary by Dr. Valentin Fuster
2009;():211-220. doi:10.1115/MSEC2009-84341.

Reconfigurable Assembly Systems (RAS) offer the potential to enable rapid exchange of functional modules to facilitate a change in product, system requirements or to provide equipment redundancy. There has however been little investigation into the planning of multiple system reconfigurations. The work proposes a capability-based approach; consisting of a Reconfiguration Methodology, supported by a Capability Model and Taxonomy. The Methodology focuses on multiple system reconfigurations and is based upon operator-oriented definition, thereby utilising existing knowledge and expertise. Furthermore, the Methodology incorporates Production Scenarios, which define the customer’s needs and priorities. The selected scenario is then used to refine the Reconfiguration Methodology with respect to the solution generated. The Capability Model consists of Capability Identification and Comparison processes: by aggregating the results, capability and compatibility sets can be derived. Further, the Model has strong links to the Capability Taxonomy. The work proposed describes the overall approach and key elements and goes on to detail the Capability Taxonomy and Model and the Reconfiguration Methodology. Key conclusions are drawn and future work outlined.

Topics: Manufacturing
Commentary by Dr. Valentin Fuster
2009;():221-229. doi:10.1115/MSEC2009-84355.

This paper presents an overview of an adaptive setup planning system that considers both the availability and capability of machines on a shop floor. It integrates scheduling functions at setup planning stage, and utilizes a two-step decision-making strategy for generating machine-neutral and machine-specific optimal setup plans. The objective is to enable adaptive setup planning for dynamic machining job shop operations. Particularly, this paper documents basic algorithms and architecture of the setup planning system for dynamically assigned machines. It is then validated through a case study.

Topics: Machine shops
Commentary by Dr. Valentin Fuster

Advances and Technical Challenges in RFID Research and Applications

2009;():231-236. doi:10.1115/MSEC2009-84122.

RFID technology can be applied during the different phases of a product realization, material handling, packaging, but also during the disassembly. Recently, environmental issues have posed certain challenges in a way that products are being handled after the end of their lifecycle. Nowadays, the products are being designed for assembly but also for a disassembly. Whatever the selected strategy for products or parts of products is at the end of their life cycle, it is necessary to design an appropriate production system as well as a disassembly system. Reflection about the final stages in a product overall lifecycle early in the process has enabled focus on a sustainable design. In this paper, one such system is going to be described. Managing of product related data and product identification could be more efficient if some new technologies are used. One of them is the use In-mould labeling (IML) technology. The molded plastic items are being labeled before they are formed by different kinds of robots or manipulators. Labels are caught into the mould of plastic injection molding machines (IMM). Our intention is to present an automated system that enables tracking of product throughout the different stages of its lifecycle. Writing and updating information about the states of the IML robot and its basic robot components (e.g. cylinders), on the RFID tag and in database, could be done only by an authorized user. The user can get the information about the momentary status of a particular product or part during different phases during the life cycle. Information placed in the database about a product can describe the components that can be used for spare parts, information about the services (dates and descriptions), number of working cycles, etc. Such information can be used for product or part tracking for preventive maintenance.

Topics: Maintenance
Commentary by Dr. Valentin Fuster
2009;():237-245. doi:10.1115/MSEC2009-84168.

China is one of the world’s largest manufacturers and consumers of Radio Frequency Identification (RFID) applications. Current estimates show that China will need over 3 billion RFID tags to satisfy demand in the year 2009. The applications for RFID patents have spread across a very diverse range of inventions and in the future it is likely that most products manufactured in China will contain an RFID tag. China’s RFID industry has grown along with the demand and researchers are making significant technological advances. In this research, patent data from the State Intellectual Property Office of the People’s Republic of China (SIPO) have been used to explore RFID technology development and its trends. Patent abstracts containing the key word and phrase ‘RFID’ and ‘Radio Frequency Identification’ were collected for analysis, content extraction, and clustering. In total, 1,389 patents from the SIPO database covering the years 1995 to 2008 were retrieved and archived for analysis. Patents provide exclusive rights and legal protection for inventors, play an important role in the development and fair diffusion of technology, and contain detailed specifications necessary to define and protect the boundaries of an invention. Through patent analysis, companies monitor the development of technology and evaluate the position of potential competitors in the market. This research applies patent content analysis to map and interpret the current trends of RFID technology development in China. A patent content clustering method is used to cluster different patent documents into homogenous groups, and then technology forecasting is applied to evaluate possible market opportunities for future inventors and investors. The results suggest that the cluster called RFID wireless communication devices has entered the saturation stage and thus provides limited opportunity for development. Four other clusters; RFID concepts and applications, RFID architecture, RFID tracking implementation, and RFID transmission apparatus, have entered the mature stage. The RFID frequency and waves cluster appears to be in early growth stage with good development potential. Since the technology related to basic RFID concepts and devices has reached a mature stage in China, the research and development seems to be targeting the improvement of the RFID frequencies and waves as a means to develop more reliable RFID systems and applications.

Topics: China , Patents
Commentary by Dr. Valentin Fuster
2009;():247-256. doi:10.1115/MSEC2009-84209.

Recently, with the development of urbanization, the enhancement efficiency of contactless, real-time features and high data transmission rate in supply chain management are widely discussed. The cold chain is one part of the supply chain, and especially the temperature monitoring plays a vital role in cold chain system. In this paper, we apply EWMA control chart and artificial neural network technologies to monitor temperature data. The back-propagation neural network is used to predict temperature shifts and trend. EWMA control chart is adopted to monitor temperature variation. As there’re something wrong happened, the control center of an enterprise can do some actions immediately to prevent further disaster. Finally, we construct a system with back-propagation neural network and statistical process control chart. A simulations and demonstrations environment using LEGO® bricks is also implemented.

Commentary by Dr. Valentin Fuster
2009;():257-265. doi:10.1115/MSEC2009-84305.

With the rapid development of global economy and great improvement on life quality of consumers, the consumer shopping behaviors have been changed significantly. Modern retailers have put intensive effort on merchandise arrangement in order to satisfy the consumer demands on merchandise shopping. However, most retailers do not provide satisfactory shopping services to customers. For instance, without a customized shopping recommendation for each individual customer, consumers have to spend a lot of time for merchandise selection. Furthermore, most large-spaced retailers merely utilize signs in front the aisles of specific merchandise areas to direct consumers, which cannot provide an accurate guidance for merchandise search. Therefore, regarding the shopping services of a modern retailer, this research develops a customized merchandise recommendation algorithm (CMRA) and a shopping route determination and guidance algorithm (SRDGA). Based on the proposed algorithms, a Shopping Service System (3S-System) is established by integrating the RFID technology. Considering the consumer demands, consumer shopping preferences and market promotion plans, this research proposes an integrated, heuristic methodology to provide a customized shopping list, route recommendation and real-time direction guidance for consumer shopping. Moreover, based on the proposed methodology, a Shopping Service System (3S-System) is established, and a simulated market is created in order to verify the feasibility of the proposed model. The verification results show that the system can offer customers appropriate shopping route recommendation in a short time and could achieve real-time guidance. As a whole, this research provides a methodology and system to provide effective shopping services for consumers and as a result the shopping service quality of modern retailers can be enhanced and the sales volume of merchandises can be increased.

Commentary by Dr. Valentin Fuster
2009;():267-275. doi:10.1115/MSEC2009-84323.

Radio frequency identification (RFID) is a promising technology for localization in various industrial applications. In RFID localization, accuracy is the top performance concern, and it is affected by multiple factors. In this paper, we investigate how the facility geometry impacts the expected localization accuracy in the entire region where the target is uniformly distributed. Three groups of geometries, namely, rectangles with various length-to-width ratios, circle, and regular polygons with 3–10 edges, are chosen for this study. A hybrid multilateration approach, which combines linearization and nonlinear optimization, is used to estimate the target location. Since the layout of landmarks significantly affects localization performance, we evaluate the expected accuracy in a facility obtained under the optimal landmark layout for the facility. The optimal landmark layout for each type of facility geometry is obtained, and then the effect of geometry is studied by comparing the expected accuracies of these layouts. It is discovered that (1) the optimal layouts follow several simple empirical deployment principles, (2) for all geometries, the expected accuracy improves and tends to reach the expected Cramer-Rao lower bound as more landmarks are used, and (3) if the same numbers of landmarks are used, the expected accuracies for circular and regular polygonal geometries are close. However, the expected accuracy for a rectangular geometry decreases as the length-to-width ratio increases.

Topics: Geometry
Commentary by Dr. Valentin Fuster

Advances in Modeling, Analysis, and Simulation of Manufacturing Processes

2009;():277-282. doi:10.1115/MSEC2009-84032.

Bayesian methods are a powerful tool when making decisions in the presence of uncertainty. Not only do they provide a mathematical framework of incorporating information from both theoretical and experimental sources, but they also quantify the value that can be gained from additional information, such as further experimentation. Consequently, experimental design can be optimized directly in terms of the value added. Manufacturing decisions can often depend on complex functions. In this work, Bayesian methods for predicting functions are explored. First, Brownian distributions, a relatively simple class of distributions with some useful properties are introduced. To illustrate how Brownian distributions can be used in a manufacturing situation, experimental design for stability limit prediction is treated in a case study. In addition, a method of building general distributions from underlying dynamical models is introduced.

Commentary by Dr. Valentin Fuster
2009;():283-292. doi:10.1115/MSEC2009-84037.

Rotary Ultrasonic Machining (RUM) is a hybrid machining approach that combines two material removal mechanisms, namely diamond grinding and ultrasonic machining. Currently available literature mainly focuses on static parametric relationships. This paper presents preliminary results of an experimental study on some aspects of the RUM process performance, surface integrity, and dynamic process modeling. A stochastic modeling and analysis technique called Data Dependent Systems (DDS) was used to study RUM generated surface profiles and cutting force signals. The DDS wavelength decomposition of the surface profiles suggested that the major characteristic root wavelength had a positive correlation with feed rate, and the wavelength magnitude may be linked to the grain size of the workpiece material. In addition, the difference of the major wavelength between the surface profiles for machined holes and that for machined rods was investigated. The surface variation between the entrance and exit segments of both holes and rods were also studied. Moreover, the DDS modeling approach was applied to cutting force signals collected during RUM and comparisons were made to the surface profiles results.

Commentary by Dr. Valentin Fuster
2009;():293-299. doi:10.1115/MSEC2009-84041.

Since laser assisted milling (LAMill) exhibits complicated characteristics in ceramic machining, this paper applies a distinct-element code, PFC2D (Particle Flow Code in Two-Dimensions), to conduct cutting simulation of laser assisted slab milling and explore its machining mechanism. The microstructure of a β-type silicon nitride ceramic (β-Si3 N4 ) is modeled at grain scale. Clusters are used to simulate the rod-like grains of β-Si3 N4 . Parallel bonds are employed to represent the connection between intergranular glass phase and grains. A temperature-dependent PFC specimen is created for simulation of LAMill. A special milling cutter is designed for improving the computing efficiency. Simulation results show that the cutting force is strongly related to crack formation and propagation. The specific cutting energy decreases as the cutting temperature increases.

Commentary by Dr. Valentin Fuster
2009;():301-309. doi:10.1115/MSEC2009-84054.

A finite element model, coupled with a thermo-kinetic model is developed to simulate the heat transfer and microstructural evolution in laser deposition of a metal-matrix composite powder. The model is used to predict the final hardness and the effect of process parameters on a metal matrix. A defined area is covered by H13-WC powder with three different deposition patterns: one-section, two-section, and three-section. The one-section pattern is the normal deposition pattern in which the deposition area is covered with zigzag patterns and in one step. In the two- and three-section patterns, the deposition area is divided to two and three sections, respectively, and is covered in two and three steps. The finite element model is used to determine the temperature history of the process used in the kinetic model to analyze the tempering effect of the heating and cooling cycles of the deposition process on the composite matrix. The results show that dividing the area under deposition into smaller areas can influence the phase transformation kinetics of the process and, consequently, change the final hardness of the metal matrix. The two-section pattern shows a higher average hardness than the one-section pattern, and the three-section pattern shows a fully hardened surface without significant tempered zones with low hardness. The simulation results are in very good agreement with the experimental ones.

Commentary by Dr. Valentin Fuster
2009;():311-319. doi:10.1115/MSEC2009-84064.

Modern fatigue analysis is providing analytical solutions to problems that could previously be addressed only by methods that were highly empirical and often inaccurate. We can now focus on five crucial steps to successful fatigue analysis. Working from elastic finite element models, the five steps are: 1) the calculation of elastic-plastic stresses and strains for complex loading and biaxial stress states; 2) modification of the endurance limit to allow for the interaction between small and larger cycles; 3) the calculation of the life to crack initiation; 4) critical plane searching to determine the orientation of a potential crack; 5) and an assessment of whether the crack will propagate to failure. The paper describes these steps and the underlying theories, and gives industrial examples of their application to real components.

Commentary by Dr. Valentin Fuster
2009;():321-330. doi:10.1115/MSEC2009-84067.

A consideration of the dynamic interaction between the machine tool structure and the cutting process is required for the prediction and optimization of machining tasks through simulation. This paper outlines a modular, analytical cutting force model applicable to common turning processes. It takes into account the dynamic material behavior and nonlinear friction ratios on the rake face as well as heat transfer phenomena in the deformation zones. In order to overcome simplifying assumptions in analytical cutting force descriptions and to incorporate the chip formation process into the analysis, specific input variables are determined in a metal cutting simulation based on the Finite Element Method (FEM). On the machine tool structure side, the setup of a parametric FEM model is presented. The accuracy of both the machine tool and cutting force models was verified experimentally on a turning center.

Commentary by Dr. Valentin Fuster
2009;():331-340. doi:10.1115/MSEC2009-84100.

In this paper, we have combined experimental and numerical approaches to understand the flank wear and its evolution of the multi-layer (TiCN/Al2 O3 /TiCN) coated carbide insert after continuous turning of AISI 1045 steels. In addition using advanced microscope techniques such as scanning electron microscope, confocal laser scanning microscope, etc., we have captured the three dimensional images of flank wear. Using the wavelet filtering, the roughness profiles and groove sizes on the flank surface were analyzed and compared. Both 2-body and 3-body abrasion models were used as the basis to predict flank wear lands, which are then compared with the experimentally observed wear images. Finite Element (FE) models were developed to simulate the changes on the interfacial conditions as the flank wear progresses during cutting.

Topics: Wear , Abrasion
Commentary by Dr. Valentin Fuster
2009;():341-346. doi:10.1115/MSEC2009-84147.

Grinding is a special machining process with large number of parameters influencing each other. Any grinding process involves six basic microscopic wheel-workpiece interaction modes in terms of grain cutting, plowing, and sliding, as well as bond-workpiece friction, chip-workpiece friction, and chipbond friction. And quantification of all the 6 modes immensely enhances understanding and managing of the grinding processes. In this paper, the kinematics simulation is presented to imitate the grinding wheel surface moving against the workpiece under specified grinding conditions. The grinding wheel surface is imported from the fabrication analysis based grinding wheel model of previous work. During each simulation iteration step, it provides the number of contacting grains, contact cross-section area for each grain, and resultant workpiece surface condition. Through retrieving the specific force value from the single grain cutting simulation, the cutting force and plowing force can be calculated. This model can also be potentially used in the time dependent behavior and thermal analysis of grinding processes.

Commentary by Dr. Valentin Fuster
2009;():347-356. doi:10.1115/MSEC2009-84152.

Laser transformation hardening (LTH) based on rapid heating and cooling cycles produce hard and wear-resistant layers of the metallic component. A high intensity moving laser beam heats up the thin layer of the external surface of the component without damaging the bulk of material. The metallurgical transformations taking place in the material during the thermo-kinetic cycles could effectively improve the mechanical properties of its surface. Nowadays, a high power direct diode laser (HPDDL) has been accepted by industry as a valuable tool to carry out this process. A three-dimensional (3-D) transient thermo-kinetic model has been developed to predict the temperature profile of the hardened layers of the material surface. The temperature-dependence of the thermal properties of the material is taken into account in the model. The laser beam is considered as a moving line heat source with a uniform distribution of laser power. The numerical solution is obtained by using a transient 3-D heat conduction equation with convection boundary conditions at the surfaces of the workpiece. A number of experiments have been carried out to harden components of AISI S7 tool steel by a continuous wave (CW) HPDDL at different power levels (1200 W – 2000 W) and different scanning speeds (5 mm/s – 20 mm/s). The main processing parameters such as laser power and scanning speed are optimized based on the numerical analysis of the heat conduction involved in this process. The numerical simulation results are compared with results produced experimentally by a HPDDL laser operating in CW, showing good agreement.

Commentary by Dr. Valentin Fuster
2009;():357-364. doi:10.1115/MSEC2009-84156.

Predictive control and intermittent setpoints are proposed to overcome the dead time that problem occurs in a new class of high precision position sensor for manufacturing equipment. In place of a rotary encoder or linear glass scale, a combination of a digital camera and a Liquid Crystal Display (LCD) screen is used to actively monitor two dimensional position changes on an XY table. In order to achieve precise spatial resolution, an actively-controlled planar pixel matrix is used as the tracking target for the system. A digital camera senses the location of the moving image displayed on the LCD screen and provides 2 dimensional position feedback. Thus, the timing and the quality of the visual feedback to the controller are the significant factors to determine the accuracy of the system. Due to the long image processing time, the vision feedback of the actual position of the stage is delayed. At the same time, with the slow frame capturing rates of the camera, dead time occurs between consecutive acquisitions of feedback signals from the vision system to the motion controller, which is detrimental to the performance of the system. Hence, studies and detailed analysis on different dead time compensation strategies and path planning algorithms have been performed to select the optimal strategy to address these challenges. Based on simulation results, a proposed method for integrating predictive control with virtual intermittent setpoints algorithm to mitigate dead time problem is presented in the final section of the paper.

Commentary by Dr. Valentin Fuster
2009;():365-371. doi:10.1115/MSEC2009-84160.

In aluminum recycling about 4% on average is lost on oxidation and dross. However, large percent of remelt secondary ingots (RSI) produce much more dross after remelting. It is rather surprising that no dross can be detected in the RSI, but after remelting some parts of apparently ‘healthy’ aluminum can give up to 80% of dross. This raises question how dross gets formed. Recent research proposes that the formation of dross after remelting of the RSI is closely related to the solidification process in the ingot, specifically the formation of shrinkage porosity, hydrogen porosity, and hot tearing. Under these circumstances, dross comes from oxidized surfaces of those defects. In this paper, simulations of the RSI cooling down show susceptibility of ingots towards shrinkage porosity and hot tearing, which are in accordance with experimental findings. Simulations also show that dross is more likely to form with increased temperature of the mold and increased thickness of the ingot. The only efficient solution for the problem of dross formation, however, seems to be a change in geometry of the mold.

Commentary by Dr. Valentin Fuster
2009;():373-380. doi:10.1115/MSEC2009-84162.

ISO Standard is propagating in all aspects of industries worldwide. In order to keep competitiveness, companies are subjected to necessity for their production to be in accordance with ISO. S-type cultivator tines are used in agriculture for the soil preparation. Dimensions and the methods of testing S-tines are proposed by the standards ISO 5678-1993(E) and ISO 8947-1993(E), respectively. The fatigue test defined by ISO-8947(E) proved to be very rigorous. Stresses which develop in the S-type tine during the fatigue test were determined by the finite element method, using MSC Patran/MD Nastran software packages. Results show that tensile stresses during the test are as high as 1100 MPa (around 160 ksi). It is very strict requirement to have the yield strength higher than that value. This requirement is possible to achieve using thermomechanical treatment, a combination of metal working and heat treatment of mainly high-strength low-alloy (HSLA) steels.

Commentary by Dr. Valentin Fuster
2009;():381-393. doi:10.1115/MSEC2009-84175.

In this paper the dynamical behavior of a part and an actuated fixture system is studied. The part is modeled using the finite element method. Subsequently, a reduced model is established using the Craig-Bampton reduction method in order to create a small-sized model, accurately describing the dynamic behavior of the part. The clampers and locators of the fixture are modeled as springs. The fixture frame is considered to be much stiffer than the locators such that it provides zero displacement boundary conditions to the locators. An electromechanical actuator is utilized to provide the adaptive clamping forces. After investigating proportional control, integral control, the three term classical PID controller and a lag filter for dynamic compensation, the analysis shows that position feedback can be used effectively in combination with integral control action to minimize unnecessary displacement of the workpiece and increase the bandwidth of the actuated fixture system.

Commentary by Dr. Valentin Fuster
2009;():395-407. doi:10.1115/MSEC2009-84189.

Metamodeling is investigated as a tool for predictive process control of welding applications. The motivation for predictive process control is to incorporate physics-based models in place of empirical models that are statistically derived from repeated physical tests. Predictive process control promises to be particularly useful for high flexibility applications, such as frequent modifications of material or geometry. One of the primary challenges is that accurate physics-based, thermal models of the welding process usually require computationally expensive software such as FLUENT [1], while faster models, such as the analytical models of Rosenthal [2], are typically less accurate. Metamodeling or surrogate modeling is investigated as an alternative modeling technique for combining the accuracy of the detailed models with the speed of the faster models, thereby enabling real-time control of the welding process. Four of the most promising metamodeling techniques—polynomial regression, multivariate adaptive regression splines, kriging, and support vector regression—are selected based on a set of preliminary criteria. Each technique is used to build surrogate models of a representative welding process, based on FLUENT data obtained with statistically designed experiments. The techniques are compared with respect to accuracy, speed of model construction, and speed of prediction. Implications for predictive process control of a welding process are also discussed.

Commentary by Dr. Valentin Fuster
2009;():409-418. doi:10.1115/MSEC2009-84231.

The importance of mechatronics is evidenced by the myriad smart products that we take for granted in our daily lives, from the wall climbing robots to advanced flight control systems and multifunctional precision machines. The multidisciplinary mechatronic field offers optimum solutions to a multivariable problem. The technological advances in digital engineering, simulation and modeling, electromechanical motion devices, power electronics, computers and informatics, MEMS, microprocessors and DSPs have brought new challenges to industry and academia. Modeling, simulation, analysis, virtual prototyping and visualization are critical aspects of developing advanced mechatronic products. Competing in a global market requires the adaptation of modern technology to yield flexible, multifunctional products that are better, cheaper and intelligent. This presentation will examine recent advances of mechatronics in smart manufacturing and will examine (a) Development and implementation of original and innovative mechatronic systems, (b) Additional modifications and improvements to conventional designs by using a mechatronics approach.

Commentary by Dr. Valentin Fuster
2009;():419-426. doi:10.1115/MSEC2009-84236.

Residual stress prediction in hard turning has been recognized as one of the most important and challenging tasks. A hybrid finite element predictive model has been developed with the concept of plowed depth to predict residual stress profiles in hard turning. With the thermo-mechanical work material properties, residual stress has been predicted by simulating the dynamic turning process followed by a quasi-static stress relaxation process. The residual stress profiles were predicted for a series of plowed depths potentially encountered in machining. The predicted residual stress profiles agree with the experimental one in general. A transition of residual stress profile has been recovered at the critical plowed depth. In addition, the effects of cutting speed, friction coefficient and inelastic heat coefficient on residual stress profiles have also been studied and explained.

Commentary by Dr. Valentin Fuster
2009;():427-436. doi:10.1115/MSEC2009-84239.

In this paper, the authors present a platform for the modeling of mold filling and solidification of binary alloys with properties similar to Mg alloys. A volume-of-fluid (VOF) based method is used to capture the interface between solid and liquid in binary alloys solidification process on a fixed non-uniform grid, developed for implementation in a colocated finite volume framework. Contrary to other works, to update the volume fraction (of fluid) in the field, a link between source-based type of energy equation and VOF reconstruction algorithm is described and implemented. A new approximation to the pressure gradient is presented to remove all ‘Spurious Currents’ [1] resulting from pressure jumps in the vicinity of the interface. Based upon the work presented, it is concluded that the present combination of the equations are not only computationally straightforward to implement and upgrade to a 3D problem, but also provides an excellent platform to capture the interface between constituents in a die-casting process including solidification and mold filling process. The current framework will be used in future works to characterize the local mechanical properties of Mg alloys by using information from simulation at the dendritic level.

Commentary by Dr. Valentin Fuster
2009;():437-444. doi:10.1115/MSEC2009-84280.

The steady state motion of a machine-tool is numerically predicted with interaction of the chip/tool friction boundary. The chip/tool friction boundary is modeled via a discontinuous systems theory in effort to validate the passage of motion through such a boundary. The mechanical analogy of the machine-tool is shown and the continuous systems of such a model are governed by a linear two degree of freedom set of differential equations. The domains describing the span of the continuous systems are defined such that the discontinuous systems theory can be applied to this machine-tool analogy. Specifically, the numerical prediction of eccentricity amplitude and frequency attribute the chip seizure motion to the onset or route to unstable interrupted cutting.

Commentary by Dr. Valentin Fuster
2009;():445-454. doi:10.1115/MSEC2009-84299.

The objective of this research is to identify a dynamic model that describes the temperature distribution in a die using a neural network (NN) approach. By using data sets obtained from a finite element analysis (FEA) of the thermal dynamics of a die and applying NN off-line and on-line learning algorithms, the die model is identified. This identification approach has been conducted assuming fully measurable and partially measurable states. For the latter, a NN based adaptive observer is employed to estimate unmeasurable states. It is shown that the complex behavior of the die system with cooling channels can be accurately identified in both cases of fully and partially measurable states.

Commentary by Dr. Valentin Fuster
2009;():455-465. doi:10.1115/MSEC2009-84324.

Metal cutting as a science remains more art than science. A truly predictive model for use in quantitative modeling has eluded researchers to date, leading the noted mathematician, R. Hill [1] to observe that “it is notorious that the extant theories of the mechanics of machining do not agree well with experiment”. Extensive experiments with a videographic quick stop device (VQSD) by the author indicate an extremely simple reason for these disagreements. A simple correction that is applicable to all of the classic orthogonal models of metal cutting is presented. A detailed application to the classic Merchant Force Diagram is then developed.

Topics: Metal cutting
Commentary by Dr. Valentin Fuster
2009;():467-473. doi:10.1115/MSEC2009-84326.

CAE tools can be used to study the characteristics and reduce the cost of sheet metal parts that are used in products. Using an instrument panel that is used in a car as an example which is made up of sheet metal components the basic process of analyzing the components and assembly to optimize its design is discussed. The paper is mostly educational in the sense that the integrated procedures and analysis presented here can be adapted in a senior level course and at a university that has state-of-the-art CAE tools as discussed in this paper. Several tutorials have been developed that are user-friendly and show how the subsequent analysis can be conducted. To the best of the knowledge of the authors, no such tutorials exist, or are available to students at a university. To start out, solid modeling of the individual sheet metal components using different CAD programs is discussed. Then a discussion on how these solid models can be imported to different CAE programs to be meshed and then subsequently exported to high end solvers like LS-Dyna or MSC Nastran is presented. The integrated analysis that was conducted for this paper was forming analysis of the individual components, followed by modal analysis and gauge optimization of the entire instrument panel assembly. Also, a design of experiments based on Taguchi method is discussed which was done to determine the effects that the input factors have on the results of the forming simulations that were conducted. It is believed that the contents of this paper serve as an educational tool to the students and the instructors involved in understanding and/or teaching sheet metal forming simulation. Sample tutorials will be presented at the conference meeting.

Commentary by Dr. Valentin Fuster
2009;():475-484. doi:10.1115/MSEC2009-84347.

We are interested in developing a general design optimization loop for extruder flow channel inserts based on 3-D finite element analysis (FEA). A key step of the computational procedure is the automated flow uniformity assessment which requires a quantitative characterization of the flow uniformity at the exit opening. To this end, a non-dimensional flow uniformity parameter is proposed, which is independent of flow rate & geometric dimensions and applicable to any shape of the flow channel cross-section. For a rectangular exit opening, two additional flow uniformity parameters are used to characterize the flow distribution in the two principal directions of the exit cross-section. The proposed flow uniformity parameter was successfully used as the objective function in an automated optimization loop for geometric design of flow channel inserts. The automated optimization loop allowed us to explore the design space in a broad range. Simulation results show that flow balance is consistently improved with the expansion of the design search space. It was also found that the automated optimization loop provides a better optimal solution than those obtained from the manual optimization approach under the same pressure-drop constraint.

Commentary by Dr. Valentin Fuster
2009;():485-491. doi:10.1115/MSEC2009-84358.

Chemical vapor deposition (CVD)-grown diamond films have found applications as a hard coating for cutting tools. Even though the use of conventional diamond coatings seems to be accepted in the cutting tool industry, selections of proper coating thickness for different machining operations have not been often studied. Coating thickness affects the characteristics of diamond coated cutting tools in different perspectives that may mutually impact the tool performance in machining in a complex way. In this study, coating thickness effects on the deposition residual stresses, particularly around a cutting edge, and on coating failure modes were numerically investigated. On the other hand, coating thickness effects on tool surface smoothness and cutting edge radii were experimentally investigated. In addition, machining Al matrix composites using diamond coated tools with varied coating thicknesses was conducted to evaluate the effects on cutting forces, part surface finish and tool wear. The results are summarized as follows. (1) Increasing coating thickness will increase the residual stresses at the coating-substrate interface. (2) On the other hand, increasing coating thickness will generally increase the resistance of coating cracking and delamination. (3) Thicker coatings will result in larger edge radii; however, the extent of the effect on cutting forces also depends upon the machining condition. (4) For the thickness range tested, the life of diamond coated tools increases with the coating thickness because of delay of delaminations.

Commentary by Dr. Valentin Fuster
2009;():493-498. doi:10.1115/MSEC2009-84362.

This paper presents investigations on machining of a nickel-based alloy. Orthogonal cutting tests using uncoated carbide inserts with 10 and 25 micron edge radius and 0 and 3 degree tool rake angles are performed. Forces, chip geometry and tool edge conditions are measured. An analytical model is introduced to identify average strain, strain rate, shear stress and temperature for segmented chip formation and friction conditions exerted on the tool during cutting process. Johnson-Cook material model related flow stress data are modified using the experimental data. Finite Element simulations are conducted to investigate the influence of tool geometry on predicted stress, strain and temperature distributions on machined surfaces.

Commentary by Dr. Valentin Fuster

Advances in Materials Forming

2009;():499-505. doi:10.1115/MSEC2009-84018.

Loading path is one of key factors that influence the formability of sheet metal forming processes. In this study, the effect of several kinds of loading paths on the thickness distribution of TRIP steel is investigated in a deep drawing process based on a constitutive model accompanying the strain-induced martensite transformation. A kinetic model of transformation, that describes the relationship between the thickness distribution of a deep drawing process and the martensite transformation, is used to calculate the martensite volume fraction. The influences of loading path on the martensite transformation are also evaluated through the change in the stress-strain state, the forming temperature, the transformation driving force, the nucleation site probability and the shear-band intersection controlled by the stress-strain state and forming temperature at the minimum thickness location in the formed part.

Commentary by Dr. Valentin Fuster
2009;():507-512. doi:10.1115/MSEC2009-84062.

This work considers the influences of various types of die surface treatment, lubricants and temperature on friction for hot forging process of brass. Well-known ring compression test were carried out to evaluate friction coefficient for various conditions. Tool material was hot work tool steel H13 and workpiece material was brass C3771. Tool surface condition selected were normal hardening, treated by hard chrome, plasma nitriding and vacuum nitriding. Tests were conducted with and without lubricants at elevated temperature between 400–600°C. The results of experiments without lubricant show that friction coefficient is reduced when using die with treated surface regardless of working temperature. The influences of surface treated on die are not significant when forming under lubricated condition. In other word, lubricant has minor effect to reduce friction when the treated tools are employed. However, graphite in water was found to be almost compatible lubricant to graphite in oil when forming by tool which is treated by vacuum nitriding. The hardness and roughness of tool surfaces are found no relevance to friction coefficient in this work.

Commentary by Dr. Valentin Fuster
2009;():513-519. doi:10.1115/MSEC2009-84070.

Developing a proper local formability failure criterion is the key to the successful prediction of the local formability of Advanced High Strength Steels (AHSS) in computer simulations. Shear fracture, which refers to the fracture occurred in the die radius when a sheet metal is drawn over a small die radius, often occurs earlier than predicted by the conventional forming limit curve (FLC). As shown in a previous study using a laboratory Stretch-Forming Simulator (SFS), shear fracture depends not only on the radius-to-thickness (R/T) ratio but also on the tension/stretch level applied to the sheet during stretching or drawing. In the SFS test, a flat sheet is first clamped at the both ends then gradually is wrapped around the die radius as the punch moves downward. This process simulates the early stage of stamping when a sheet metal is initially stretched or drawn over a die/punch radius. However, shear fracture may not occur in this stage if the stretch/tension level is not high enough. In this study, the Bending under Tension (BUT) tester is used to evaluate shear fracture occurring in the later stage of stamping, after the sheet metal is totally wrapped around the die radius. It is demonstrated that shear fracture does occur in this deformation mode when a sufficient tension level is applied. Effects of forming conditions, such as forming speeds and lubrication on shear fracture, are also investigated. When compared to the results from the SFS, the data points failing at the die radius tangent point agree very well. It is observed that all data points above the tangent point failure line show shear fracture, while data points below this line show tensile failure (localized necking) regardless of the test methods used. This indicates that the tangent point fracture line can be used as the shear fracture failure limit. This failure criterion can be used in a computer simulation to simulate the shear fracture phenomenon in the entire deformation process involved in a sheet metal stretching or drawing over a die radius.

Commentary by Dr. Valentin Fuster
2009;():521-529. doi:10.1115/MSEC2009-84092.

A strain increment method has been proposed for early formability assessment by predicting strain distribution directly from the part-to-part mapping process. This method consists of mapping the finite element mesh to the geometry of an existing part, solving the part-to-part mapping relation by adding bending energy and strain gradient penalty functions, and extracting strain increment from the part-to-part mapping related displacement field. Case studies show that the strain field obtained using the proposed strain increment method compares well with that from the finite element analysis. Since this method does not require the knowledge on new die surface, such formability assessment can serve as an early manufacturing feasibility analysis on the new part design.

Commentary by Dr. Valentin Fuster
2009;():531-536. doi:10.1115/MSEC2009-84137.

Alternative manufacturing processes such as hot working and Electrical-Assisted Forming (EAF), which involves passing a high density electrical current through the workpiece during deformation, have been shown to increase the potential strain induced in materials and reduce required forces for deformation. While forming at elevated temperatures is common, the EAF process provides more significant improvements in formability without the undesirable affects associated with forming at elevated temperatures. This research investigates the effect of grain size and current density on annealed pure copper during the EAF process. The flow stress reduction effect of the process was shown to decrease with increasing grain sizes. A threshold current density, required to achieve a significant reduction in the flow stresses, becomes more apparent at larger grain sizes and the value increases with increasing grain size. The effects increase with increasing strain due to dislocations being generated during deformation. Therefore the dislocation density, related in part by the grain size, appears to be a factor in the EAF process.

Commentary by Dr. Valentin Fuster
2009;():537-545. doi:10.1115/MSEC2009-84138.

Tearing concerns in sheet metal forming have traditionally been predicted by comparing the strain state imposed on a material to its associated strain based Forming Limit Diagram. A shortcoming of this strain based failure criterion is that the Forming Limit Curves exhibit strain path dependence. Alternatively, a stress based failure criterion was introduced and shown analytically and numerically to exhibit less strain path dependence. In our past research, an analytical model was created to predict the stress based Forming Limit Curve. Inputs into the model include a material constitutive relationship, anisotropic yield criterion and a critical stress concentration factor, defined as the ratio of the effective stress in the base material to the effective stress in the necking region. This stress concentration factor is thought to be a material parameter, which characterizes a material’s ability to work harden and prevent the concentration of stress which produces the necking condition. In this paper, the critical stress concentration factors for steel and aluminum alloys were determined by comparing analytical model predictions and experimental data and found to be significantly different. A setup is then proposed to experimentally measure the critical stress concentration factors and initial results are presented.

Commentary by Dr. Valentin Fuster
2009;():547-551. doi:10.1115/MSEC2009-84149.

The mechanical properties of fiber-reinforced composite materials are highly dependent on proper saturation of the resin within the reinforcement fibers. The research evaluates the effect of ultrasonic treatment during composite curing, in an effort to increase interlaminar bonding strength, lower void content, and improve the matrices ability to transfer stresses to the reinforcement fiber. The testing methods that were performed evaluated the effects or the ultrasonic treatment on the specimen in three point bending, and shear between layers of the matrix. The mechanical properties and the microstructure of the test specimen are discussed.

Commentary by Dr. Valentin Fuster
2009;():553-560. doi:10.1115/MSEC2009-84182.

Though sheet hydroforming has often been considered a good opportunity for industrial applications related to niche and medium-low volume productions, this technology has not yet found a specific application context as it is for tubes hydroforming (1). Thanks to its extensive application to industrial cases, the latter has defined, through appropriate experimental validations, ‘best practice’ rules for process design (2) and for its tryout (3, 4 and 5). Though not as exploited, sheet hydroforming has many advantages that meet industrial needs very well, such as: formability improvement, good surface quality, higher dimensional accuracy, springback reduction (6). In this paper proper metal forming numerical models and experimental analysis have been developed in order to analyze the feasibility of an industrial test case process design using this non conventional technology. Two different initial blank shapes, two different blank holder load paths (that is made up of twelve sectors) and, finally, two different fluid pressure load paths have been tested. There is clearly a good correlation among numerical and experimental results and also a robust response of the designed mechanical equipment which is able to follow, with a good accuracy, the assigned process characteristics (fluid pressure, blank holder force distribution, etc.). Different process conditions have been numerically and experimentally tested, not reaching, at this stage, the feasibility or, it would be better to say, the ‘hydroformability’ of the product.

Commentary by Dr. Valentin Fuster
2009;():561-567. doi:10.1115/MSEC2009-84185.

Sheet metal hydroforming has gained an increasing interest around the world in automotive and aerospace industries. This non conventional metal forming process has many advantages that meet industrial needs in reality very well, such as: formability improvement, good surface quality, higher dimensional accuracy, reduction of springback amount compared with the conventional processes (1). Furthermore, the process chain could be simplified with considerable cost efficiency (2, 3). Through a research program, whose objective is to define specific rules in order to assess a macro-feasibility for a given hydroforming process, the authors have analyzed the influence of the process variables on sheet metal hydroforming by taking into account different types of geometries. The goal of this research, as described in this paperwork, is to implement a methodology that allows one to check the ‘macro’ feasibility of a product through sheet metal hydroforming starting from simple considerations in the early stage of the process design (4). In this specific case, the developed methodology is characterized by the definition of a set of specifically designed ‘shape factors’ and by their application on properly designed study cases. Their application can determine the feasible limits for a considered process set up condition. The definition of the shape factors and of each of their lower bounds has been drawn through an extensive numerical and experimental investigation on three different study cases which have been described in recent publications by the same authors (5, 6 and 7). In this paper the authors aim to describe and to check the developed methodology through ‘Fondello Fanale’, an application on an industrial test case characterized by a complex geometry. Starting from the geometry of the industrial test case, one can say that it is necessary to use more than one of the defined shape factors to analyze the product feasibility. On the considered component, the most critical areas have been chosen and the geometrical gradients of the shape have been taken into account by the authors. In each one of the considered areas, shape factors have been calculated and their value has been compared to their physical limits for the considered material and thickness. Thorough numerical and experimental investigation the shape factors analysis has given the opportunity to check the non-feasibility of the product. Further developments are related to the possibility, starting from the minimum values of the analyzed shape factors, to redesign the geometry of the product in order to reach its feasibility.

Topics: Sheet metal , Shapes
Commentary by Dr. Valentin Fuster
2009;():569-576. doi:10.1115/MSEC2009-84193.

The paper has presented the reduced structure of horizontal centrifugal casting mechanism by high frequency current of bimetallic bushes from steel-bronze, with a chemical stability treatment of borderline alloy layer. This stabilizer borderline layer at interference of inner cylindrical surfaces from steel and external surfaces from bronze, has achieved by adding into filler metal of Cu-Sn a supplier non-ferrous metal added, with great specific weight and low melting point as Cu-Sn alloy, for example Sn with contents of 1% from Cu-Sn alloy. At high temperature and pressure, Sn is forming with Fe from steel mass of bimetallic bearing an inter-metallic compound FeSn2 , which reactions with Cu-Sn alloy due to a stable metallic connection. The experimental tests have realized at Machine Tools ‘Infratirea’ Co from Oradea, achieved bimetallic bearings of steel-bronze, with a good physical and thermal stability and well adhesion between antifriction steel with bronze.

Commentary by Dr. Valentin Fuster
2009;():577-581. doi:10.1115/MSEC2009-84196.

Recent advances in high temperature and high pressure applications have made significant increase in industrial applications of square and rectangular seamless tubes. In this work, a reshaping process is presented with cold rolling of a circular thick tube into a square cross section between four flat rolls in different passes. The influence of the amount of roll gap reduction in each pass on the final rolled product was investigated. In order to verify the simulation results, several experimental tests were performed. Quantities such as separated force energy, wall thickness, and corner radius of the tube were observed and measured. Obtained results of simulation showed good agreements with the experiment results.

Commentary by Dr. Valentin Fuster
2009;():583-591. doi:10.1115/MSEC2009-84253.

Preform design is critical for multi-stage forging processes to ensure the production of defects-free parts. Moreover due to the geometry and material flow complexities in forging processes, finding the optimal preform shapes could be difficult and time consuming. This paper proposes an efficient preform design methodology based on geometrical resemblance which requires a few FEA simulation iterations to obtain a good preform shape. The premise of this methodology is such that the initial and subsequent simulations are carried out by constructing a slightly larger part which geometrically resembles the desired part. Initial FEA simulation of the larger part is performed with reasonably guessed preform shape which may allow the occurrence of forming defects or flash formation. Then a series of intermediate resembling parts between the largest part and the desired part are constructed. The undeformed shape corresponding to the intermediate part could be obtained by backward tracing of material flow from the simulation results of the larger part. This undeformed shape is then taken as the preform shape of the intermediate part. The procedure is repeated until the intermediate part is geometrically close to the desired part, which leads to the preform shape. In order to verify this preform design methodology, several case studies on forging and extrusion processes have been carried out. The methodology has been proven to be computationally efficient since it requires fewer numbers of iterations.

Topics: Forging , Design , Preforms
Commentary by Dr. Valentin Fuster
2009;():593-601. doi:10.1115/MSEC2009-84267.

In the present investigation, tip test based on backward extrusion was utilized to characterize the effect of surface roughness of the billet and forming tools and type of lubricants on friction. For the test, cylindrical specimens made of aluminum alloys of 6061-O and 2024-O with four lubricants such as VG32, VG100, corn oil, and grease were used. Single punch and two die sets with different surface topologies were manufactured in order to investigate the effect of surface conditions on friction and flow behavior. The load levels and tip distances were measured for both materials and compared with each other to determine shear friction factors at the punch and counter punch interfaces separately depending on the variation of surface topologies using the finite element simulations. As a result, a linear relationship among the dimensionless load, tip distance, and shear friction factors at punch and counter punch interfaces was derived for the experimental conditions investigated. The slope change of this linear relationship from negative to positive clearly depends on the variation of the surface conditions at the billet/punch and billet/counter punch interfaces. Also, it was clearly demonstrated that the dimensionless tip distance for the frictionless case can be extrapolated from the experimental data based on the simulation results. The value for the frictionless case can be used for characterizing the relative effect due to surface topologies at punch and counter punch and lubrication qualities of lubricants under various processing conditions.

Topics: Friction , Topology
Commentary by Dr. Valentin Fuster
2009;():603-612. doi:10.1115/MSEC2009-84269.

An efficient One-Step inverse approach (IA) based on nodal tangent plane (NTP) is proposed to predict the optimum blank shapes and sizes and reasonable estimation of forming severity (i.e., thickness, strain distributions) from desired final workpieces. According to the deformation theory of plasticity, Hill’s planar isotropic yield criteria and the principle of virtual work (PVW), the non-linear elasto-plastic finite element equilibrium equations are obtained, in which the simplified boundary force conditions are also implemented to simulate the effects of punch, die, blank-holder and draw-bead. For solving the non-linear problem, Newton-Raphson method is used. However, in traditional One-Step IA, the local element stiffness matrix is assembled in the global coordinate system where bad convergence is always a severe problem, especially when vertical or quasi-vertical walls happen. Fortunately, the NTP method provides a smart solution to enhance the convergence, where the ill-conditioned matrix is avoided by assembling the local element stiffness matrix to the tangent plane and to the normal of node. The developed algorithm is integrated into independently developed KMAS (KingMesh Analysis System) for sheet metal forming. To validate its efficiency and feasibility, it is applied to square cup deep drawing of Numisheet’93 and front fender forming of Numisheet’2002 by comparing with DynaForm based on incremental algorithm and traditional One-Step IA.

Commentary by Dr. Valentin Fuster
2009;():613-618. doi:10.1115/MSEC2009-84275.

This paper presents a new rapid prototyping process of a thin sheet metal, Double Sided Incremental Forming of a cylindrical part without a die or a clamping device around the periphery of the sheet. The effects of process parameters on part shape, such as gap between two tool heads and feed rate, are examined experimentally with a special device mounted on a general lathe and numerically with a commercial finite element software package, Abaqus. Depending on the process parameter, a truncated cone shape part can be successfully fabricated with two tool heads pressing and moving along the radial direction of the sheet, which is held by lathe spindle at its center. A simple mathematic model to predict the cone angle is proposed and compared well with experimental data.

Commentary by Dr. Valentin Fuster
2009;():619-628. doi:10.1115/MSEC2009-84283.

An experimental evaluation of the strains in an oval stamp forming die is presented. The die design included a flexible blank holder and active draw beads. The die was instrumented with local punch force and wrinkle sensors and control systems were developed in order to follow local punch force and wrinkle trajectories. Strains were measured after pan forming for both open and closed-loop tests. The relation between blank holder force, draw bead penetration, and strains were explored in the critical strain region of the formed pan. Closed-loop control of the local punch forces at the die ends was established using blank holder forces. The strains for tests with various lubrication conditions and draw bead penetrations were compared. It was observed that there is a tendency for the strains in critical locations to converge or remain constant for the closed-loop control tests while the strains tended to increase with blank holder force for open-loop tests. It was concluded that by controlling local punch forces, strain is indirectly controlled.

Topics: Force , Force control , Blanks
Commentary by Dr. Valentin Fuster
2009;():629-634. doi:10.1115/MSEC2009-84300.

The present paper deals with the initial blank design of bimetallic parts obtained by deep drawing process. Normally in deep drawing, the initial blank has a simple shape and after drawing, its perimeter shape will become very complex and has considerable influences on the forming results. If the initial blank shape is designed in such a way that is formed into the desired shape after the drawing process, not only it reduces the time of trimming process, but also decreases the drawing force and the raw material needed substantially. The present paper proposes a novel approach to initial blank optimization in multilayer deep drawing. The Finite Element Method (FEM) is employed for simulating multilayer plate deep drawing process to provide training data for Artificial Neural Network (ANN). The aim of the neural network is to predict the initial blank shape for the desired final shape. The FEM results were verified through experiment.

Commentary by Dr. Valentin Fuster
2009;():635-640. doi:10.1115/MSEC2009-84331.

Functionally graded structures offer innovative solutions to various challenges in materials engineering. However, the increasing demanding of FGSs has been hindered by the complex processing methods, high cost and composite control difficulties. By combining the concept of semisolid forming and powder metallurgy, semisolid powder processing provides a novel solution to the fabrication of FGS materials. In this paper, a two-layer FGS with one layer reinforced by SiC particles was fabricated with semisolid powder processing. The results indicate that, when the SiC particles are larger than the matrix powder, dense and strong parts can be formed. Smaller SiC particles can isolate the metal powders and resulting in porous and weak structures. Also, the roughness of the SiC particle surface affects interface bonding between SiC particles and Al-Si-Cu matrix phase. In summary, semisolid powder processing is capable of fabricating graded structures with promising microstructures and mechanical properties.

Topics: Metals , Manufacturing
Commentary by Dr. Valentin Fuster
2009;():641-650. doi:10.1115/MSEC2009-84377.

In today’s industry, the need for lightweight alloys with high strength properties is growing. More specifically, magnesium alloys are in high demand. Unfortunately, magnesium’s limited formability hinders its broad range applicability. Previous research has discovered that the tensile formability of this alloy can be increased using electrical pulsing during the deformation process, referred to as Electrically-Assisted Manufacturing (EAM). Although this method increases a material’s formability (i.e. lowers flow stress, increases elongation, and reduces springback), a detailed analysis is required to further evaluate the effects of electricity on the material’s microstructure. The research herein will examine the microstructure of Magnesium AZ31B-O specimens that were deformed under uniaxial tension while electrically pulsed with various pulsing parameters (i.e. different current density/pulse duration combinations). This microstructural analysis will focus on how EAM affected grain size, grain orientation, and twinning. The microstructure of the following different specimen types will be compared: deformed EAM specimens, deformed non-pulsed baseline specimens, and undeformed non-pulsed “as received” specimens.

Commentary by Dr. Valentin Fuster
2009;():651-659. doi:10.1115/MSEC2009-84383.

Magnesium alloy sheet has received increasing attention in automotive and aerospace industries. It is widely recognized that magnesium sheet has a poor formability at room temperature. While at elevated temperature, its formability can be dramatically improved. Most of work in the field has been working with the magnesium sheet after annealed around 350°C. In this paper, the as-received commercial magnesium sheet (AZ31B-H24) with thickness of 2mm has been experimentally studied without any special heat treatment. Uniaxial tensile tests at room temperature and elevated temperature were first conducted to have a better understanding of the material properties of magnesium sheet (AZ31B-H24). Then, limit dome height (LDH) tests were conducted to capture forming limits of magnesium sheet (AZ31B-H24) at elevated temperatures. An optical method has been introduced to obtain the stress-strain curve at elevated temperatures. Experimental results of the LDH tests were presented.

Commentary by Dr. Valentin Fuster

Advances in Semiconductor Materials Manufacturing

2009;():661-670. doi:10.1115/MSEC2009-84033.

Chemical Mechanical Polishing (CMP) is a major manufacturing step extensively used to planarize semiconductor wafers. In CMP, the polishing pad surface is glazed by residues. A diamond disc conditioner is used to dress the pad to regenerate new pad profile and asperity in order to maintain favorable process conditions. This paper presents a review on process modeling of diamond disc pad conditioning in CMP. Following the introduction, the paper briefly introduces a technical background of the conditioning process and process control. It then summarizes research work on the various analytical process models proposed and ends with conclusions and topics for future research.

Commentary by Dr. Valentin Fuster
2009;():671-676. doi:10.1115/MSEC2009-84055.

Silicon (Si) wafers are the most commonly used substrates for manufacturing semiconductor devices. The design rule is miniaturized, and the chip size is increasing to improve the degree of the device integration. Then Si wafer is required to be manufactured with the higher flatness and larger diameter to meet above demands. The double-sided polishing is widely adopted as the finishing process of the wafer manufacturing, because the wafers with the good surface quality and flatness can be obtained economically. However, the polishing technology has serious problems: It is very difficult to set the appropriate conditions for stably polishing the Si wafer and wearing the pad to the high flatness. In our previous work, the optimization of the polishing conditions with the theoretical calculation was conducted, however, the calculation did not consider the relative motion direction having large influence on polishing behaviours. In this study, the optimizing method considering the relative motion direction was newly developed, and it was revealed that the calculation results corresponded well with the experimental results. Furthermore, it was found that the time-fluctuation of the wafer flatness was larger in the case of the wafer having taper shape, compared to that having convex shape in the calculation.

Commentary by Dr. Valentin Fuster
2009;():677-682. doi:10.1115/MSEC2009-84063.

Recently, the achievement of further high flatness of workpiece edge shape is strongly required in mirror finishing. Especially, the edge roll off of silicon wafers as the substrates of semiconductor devices is demanded to decrease in the polishing process for raising the yield of IC chips. Many theoretical and experimental analyses of the edge roll off generation have been already done and the polishing methods for suppressing the roll off have been proposed to meet the demand. The analyses, however, cannot fully account for the obtained edge shape in actual polishing and the problem about the roll off remains. In this study, the generation mechanism of the edge roll off based on the viscoelasticity of polishing pad was newly proposed. The mechanism considered the horizontal and vertical relative static and dynamic motion between the pad and the workpiece. Moreover, the non-contact viscoelasticity measurement instrument was originally developed to evaluate the viscoelasticity of the polishing pad precisely. A series of polishing experiments for silicon wafers revealed that the edge shape, which was induced from the edge roll off generation mechanism and the measured viscoelasticity of the polishing pad, corresponded well with the obtained edge shape.

Commentary by Dr. Valentin Fuster
2009;():683-689. doi:10.1115/MSEC2009-84068.

Lapping is an important material-removal process for manufacturing of substrate wafers. Objectives of lapping include removing subsurface damage in sliced wafers, thinning wafers to target thickness, and achieving desired flatness of wafer surfaces. A comprehensive literature review has been conducted on experimental investigations on lapping of substrate wafers. The review on material removal rate and surface roughness was published as a journal paper. As a follow-up, this paper reviews the literature on flatness and subsurface damage in lapping of substrate wafers. It presents reported experimental results on effects of process parameters on flatness and subsurface damage.

Commentary by Dr. Valentin Fuster
2009;():691-697. doi:10.1115/MSEC2009-84072.

Chemical mechanical polishing (CMP) is used to remove irregularities on the silicon wafer surface. The importance of CMP is the achievement of both local and global planarity of wafer surface. This paper presents an economic study on CMP of silicon wafers. A cost model is developed to predict the total cost for CMP of silicon wafers. An input-output model is developed to analyze parameters relevant to the fixed cost and variable cost. The labor cost is investigated through a flow chart of the labor operation. Based on the cost model, a hypothetical case study is conducted to show the model’s capability of performing sensitivity analysis and identifying critical factors for the total cost for strategic management purposes.

Commentary by Dr. Valentin Fuster
2009;():699-705. doi:10.1115/MSEC2009-84084.

Single crystal sapphire is of significant interest due to its combination of excellent optical, electrical, and mechanical properties. However, fine grinding of sapphire is quite challenging because of its high hardness and low fracture toughness, making it sensitive to cracking. Wheel loading is a common problem in conventional grinding of hard and brittle materials. ELID grinding shows great promise in achieving a mirror surface finish at a relatively high efficiency. ELID grinding of sapphire was investigated using acoustic emission. The effects of processing parameters on surface finish and acoustic emission signals were evaluated. Correlations were found among the dressing current intensity, surface finish and acoustic emission signals. A smoother surface was obtained using a higher dressing current at the cost of a higher wheel wear rate. The wheel wear mechanism in ELID grinding of sapphire was dominated by bond fracture because the bond strength is reduced by electrolysis. Results indicate that the acoustic emission technique has the potential to be used for monitoring ELID grinding process, detecting the condition of the grinding wheel, and investigating the mechanisms of ELID grinding.

Commentary by Dr. Valentin Fuster
2009;():707-713. doi:10.1115/MSEC2009-84113.

Advanced ceramics, such as Silicon Carbide (SiC) and Quartz, are increasingly being used for industrial applications. These ceramics are hard, strong, inert, and light weight. This combination of properties makes them ideal candidates for tribological, semiconductor, MEMS and optoelectronic applications respectively. Manufacturing these materials without causing surface and subsurface damage is extremely challenging due to their high hardness, brittle characteristics and poor machinability. Often times, severe fracture can result when trying to achieve high material removal rates during machining of SiC or quartz due to their low fracture toughness. This research demonstrates that ductile regime Single Point Diamond Turning (SPDT) is possible on these materials to improve its surface quality without imparting subsurface damage. Machining parameters, such as depth of cut and feed, used to carry out ductile regime machining will be discussed. Subsurface damage analysis was carried out on the machined samples using non-destructive methods such as Optical Microscopy, Raman Spectroscopy and Scanning Acoustic Microscopy to show evidence that the chosen material removal method leaves a damage-free surface and subsurface. Optical microscopy was used to image the improvements in surface finish whereas Raman spectroscopy and scanning acoustic microscopy was used to observe the formation of amorphous layer and subsurface imaging in the machined regions. All three techniques complement the initial hypothesis of being able to remove a nominally brittle material in the ductile regime.

Commentary by Dr. Valentin Fuster
2009;():715-719. doi:10.1115/MSEC2009-84114.

Semiconductor substrate wafers are used to manufacture a variety of semiconductor devices. Lapping is an important process to obtain flat wafer surfaces. Subsurface damage, however, is unavoidably generated during the lapping process and has vital effects on wafer quality. Experiments were conducted to study the effects of several lapping parameters on subsurface damage in semiconductor substrate wafers, such as abrasive grain size, abrasive material, lapping pressure, and slurry concentration. It was found that abrasive grain size and abrasive material have significant effects on subsurface damage. Effects of lapping pressure and slurry concentration on subsurface damage were less significant.

Commentary by Dr. Valentin Fuster
2009;():721-728. doi:10.1115/MSEC2009-84201.

Nanotopograhphy on unpatterned silicon wafers is becoming a serious issue in IC fabrication, especially with the decreasing critical dimension. However, there are no review papers to summarize the literature on nanotopography in silicon wafer manufacturing. This paper reviews the literature on nanotopography in silicon wafer manufacturing. It first describes the significance and definition of nanotopography. It then presents the methods and principles of nanotopography measurement. It also discusses experimental investigations about the effects of simultaneous double side grinding process on nanotopography.

Commentary by Dr. Valentin Fuster
2009;():729-736. doi:10.1115/MSEC2009-84210.

Wafers made of materials such as silicon, III-V and II-VI compounds, and optoelectronic materials, require high-degree of surface quality in order to increase the yield in micro-electronics fabrication to produce IC chips and devices. Measures of properties of surface quality of wafers include: nanotopography, surface morphology, global planarization, total thickness variation (TTV) and warp. Due to the reduction of feature size in micro-electronics fabrication, the requirements of such properties become more and more stringent. To meet such requirements, the wafer manufacturing processes of brittle semiconductor materials, such as slicing, lapping, grinding, and polishing have been continually improved. In this paper, the lapping process of wafer surface treatment is studied with experimental results of surface roughness and material removal rate. In order to improve the performance of lapping process, effects of mixed abrasive grits in the slurry of the free abrasive machining (FAM) processes are studied using a single-sided wafer-lapping machine. Under the same slurry density, experiments employing different mixing ratios of large and small abrasive grits, and various normal loadings on the wafer surface applied through a jig are conducted for parameter study. With various mixing ratios and loadings, observations and measurements such as the total amount of material removed, material removal rate, surface roughness, and relative angular velocity are presented and discussed in this paper. The experiments show that the half-half mixing ratio of abrasives removes more material than other mixing ratios under the same conditions, but with a higher surface roughness. The results of this study can provide a good reference to the FAM processes that practitioners use today by exploiting different mixing ratios and loadings of abrasive slurry in the manufacturing processes.

Topics: Grinding
Commentary by Dr. Valentin Fuster

Laser-Based Manufacturing

2009;():737-745. doi:10.1115/MSEC2009-84010.

The present work studies the heat and mass transfer process in the laser multilayered cladding of H13 tool steel powder by numerical modeling and experimental validation. A solid-liquid-gas unified transient model was developed to investigate the evolution of temperature distribution and flow velocity of the liquid phase in the molten pool. In this model, an enthalpy-porosity approach was applied to deal with the solidification and melting occurring in the clad, and a level-set method was used to track the evolution of the molten pool free surface. Moreover, heat loss due to forced convection and heat radiation and laser heat input occurring on the top surface of deposited layer and substrate have been incorporated into the source term of governing equations. The effects of laser power, scanning speed, and powder feed rate on the dilution and height of the multilayered clad are investigated based on the numerical model and experimental measurement. The results show that increasing the laser power and powder feed rate, or reducing the scanning speed, can increase the clad height and directly influence the remelted depth of each layer of deposition. The numerical results have a qualitative agreement with the experimental measurements.

Commentary by Dr. Valentin Fuster
2009;():747-751. doi:10.1115/MSEC2009-84022.

This work is to predict collapse of the molten layer surrounding the keyhole filled with vapor and droplets during drilling or high power density beam welding process. Investigating collapse of the liquid layer is essentially required for an understanding of pore formation in keyhole welding. The collapse of the keyhole is similar to transition between the slug and annular two-phase flows encountered in fluid flow field. In this study, a steady, averaged one-dimensional model widely used in two-phase flow areas is provided. The mixture in the core is treated as a homogeneous fluid. For the sake of clarification, friction induced by the liquid layer and energy absorbed by the vapor are neglected. It shows that, in contrast to insensitive effects of subsonic Mach number, the keyhole subject to supersonic Mach number at the base is readily enclosed or collapsed. A fundamental understanding of pore formation is revealed.

Commentary by Dr. Valentin Fuster
2009;():753-762. doi:10.1115/MSEC2009-84048.

This paper deals with the spallation induced by shock wave propagation in targets during the laser shock peening process. Physical aspects concerning laser-matter interaction, shock wave propagation, and spallation are considered. A continuous kinetic model for the spallation process is included in a one-dimensional finite difference hydrodynamic code using Lagrangian coordinates in order to calculate the laser-induced spallation phenomena. Shock wave propagation in solids is calculated and validated by experimental data. The spallation zone location is then calculated for various materials with different thickness of foils and various laser shock peening parameters. The numerical simulations are compared with previously reported experimental results, and good agreement is obtained for the spallation threshold and damage zone location.

Commentary by Dr. Valentin Fuster
2009;():763-770. doi:10.1115/MSEC2009-84080.

During the laser welding process of high-strength steels, different defects, such as a partial weld penetration, spatters, and blow-through holes could be present. In order to detect the presence of defects and achieve a quality control, acoustic monitoring based on microphones is applied to the welding process. As an effective sensor to monitor the laser welding process, however, the microphone is greatly limited by intensive noise existing in the complex industrial environment. In this paper, in order to acquire a clean acoustic signal from the laser welding process, two noise reduction methods are proposed: one is the spectral subtraction method based on one microphone and the other one is the beamforming based on a microphone array. By applying these two noise reduction methods, the quality of the acoustic signal is enhanced, and the acoustic signatures are extracted both in the time domain and frequency domain. The analysis results show that the extracted acoustic signatures can well indicate the different weld penetration states and they can also be used to study the internal mechanisms of the laser-material interaction.

Commentary by Dr. Valentin Fuster
2009;():771-778. doi:10.1115/MSEC2009-84087.

Microforming of metals has always been a challenge because of the limited formability of metals at micro-scales. This paper investigates an innovative micro-forming technique: Laser Dynamic Forming (LDF), which induces 3-D superplastic forming in metal thin films. This forming process proceeds in a sequence of laser irradiation of ablative coating, ionization, shockwave generation and propagation in metal thin films, and conformation of metal thin films to the shape of micro/nanoscale molds. Because the deformation proceeds at ultrahigh strain rate, it is found that materials experience superplastic deformation at microscales. In this paper, experiments are carried out to understand the deformation characteristics of LDF. The shapes of the formed samples are characterized by scanning electron microscopy (SEM) and optical profilometer. The thickness variations are characterized by slicing the cross section using focused ion beam (FIB). The magnitude of deformation depth in LDF is determined primarily by three critical factors: thin film thickness, geometry of molds, and laser intensity. The relationships between laser intensity, film thickness, and mold size are explored in process maps to find out suitable processing conditions of LDF. Nanoindentation testings are conducted to show that the mechanical properties (hardness and yield strength) are increased significantly after LDF.

Commentary by Dr. Valentin Fuster
2009;():779-786. doi:10.1115/MSEC2009-84088.

In this paper, numerical simulation of nanoparticle integrated laser shock peening of aluminum alloys was carried out. A “tied constraint” was used to connect the matrix and nanoparticle assembly in ABAQUS package. Different particle size and particle volumes fraction (PVF) were studied. It was found that there is significant stress concentration around the nanoparticles. The existence of nanoparticle will influence the stress wave propagation and thus the final stress and strain state of the material after LSP. In addition, particle size, PVF and particle orientation all influence the strain rate, static residual stress, static plastic strain and energy absorption during the LSP process.

Commentary by Dr. Valentin Fuster
2009;():787-798. doi:10.1115/MSEC2009-84089.

Novel methodology of laser sintering of mixture of mixture of bio-ceramics and metallic nanoparticles on metallic implants is introduced in current work. Feasibility of this method is demonstrated using a multiphysics numerical simulation. Treating laser beam as electromagnetic (EM) wave, EM module is coupled with heat transfer (HT) module. The EMHT scheme analyzes the interaction between laser-nanoparticles which ends up with temperature raise within the sample. As a demonstration, HAp and Ti nanoparticles are employed to be sintered on titanium substrate. Processing parameters such as laser power, beam radius, scan speed, and layer thickness are studied, and correlation between these parameters and final temperature is presented. Effects of mixing ratio and nanoparticle size are also examined. Considering effects of mixing ratios and particle sizes, the following coating scheme is proposed for future experiments: varying HAp concentration from 100% to 0% at 10% intervals from coating surface to coating/substrate interface, and meanwhile, varying particle diameters from 500 nm to 100 nm at 100 nm intervals.

Commentary by Dr. Valentin Fuster
2009;():799-805. doi:10.1115/MSEC2009-84144.

Laser beam welding is a field of growing importance to the industry. As a result of extensive and continuous development of laser beam technology, pulsed Nd:YAG laser beam sources have been introduced. Pulsed laser welding offers the advantage of very low heat input to the workpiece, resulting in low distortion and the ability to join heat sensitive components. Further improvements to the method consider pulse shape modulation in Nd:YAG laser beam sources resulting in improved weld pool dynamics. Nd:YAG laser beam welding with pulse shape modulation is studied both experimentally and theoretically. Observational results on the interaction between time-dependent heat fluxes and flows in the weld pool as well as on solidification of the molten material are presented. In welds produced with modulated laser beam pulse shape, improved material flow and finer microstructure have been observed. Using an axisymmetric 2D model for heat transfer coupled with surface tension driven flow of molten metals undergoing solid-liquid and evaporation phase transitions in the weld pool, it is shown that the time modulation of the pulse power influences the melting front and flow velocity which together with the predicted undercooling may explain the fine-grain structure of the resolidified welds that have no cracks inside.

Commentary by Dr. Valentin Fuster
2009;():807-816. doi:10.1115/MSEC2009-84181.

In this paper a system for the automatic determination of the material removal rate during laser milling process is presented. “Laser milling” can be defined as an engraving process with a strictly controlled penetration depth. In industrial applications, when a new material have to be machined or a change in the system set-up occur the user has to perform a time-consuming experimental campaign in order to determine the correlation between the material removal rate and the process parameters. In these cases the numerical models present some limits due to the elevated calculation time requested to simulate the laser milling of industrial features. In the proposed system, based on a regression model approach, the empirical coefficients, that provide the material removal rate, are automatically generated by a specific software according to the different materials that have to be processed. A description of the automated method and the results obtained in engraving TiAl6V4 and Inconel 718 superalloy with a fiber laser are presented. The system can be adapted to every combination of material/laser source.

Topics: Lasers , Manufacturing
Commentary by Dr. Valentin Fuster
2009;():817-825. doi:10.1115/MSEC2009-84184.

During hybrid laser-arc welding of galvanized dual phase steel 980 in a gap free lap joint configuration, the welding parameters have the significant influences on the weld quality, which is directly related to the temperature distribution of welds. In this paper, a 3D FEM model is used with the application of the double ellipsoidal moving heat source to simulate the transient temperature field and the dimensions of fusion zone and heat affected zone (HAZ) for hybrid laser-arc keyhole welding of galvanized steels in a gap-free lap joint configuration. Temperature-dependent thermophysical properties are used in the simulation. Effects of various welding parameters on the temperature distribution are studied. To validate the numerical results, a high-speed camera with the frame rate of 4000 fps is used to real-time capture the images of the molten pool. The numerical results show a good agreement with the experimental results.

Commentary by Dr. Valentin Fuster
2009;():827-832. doi:10.1115/MSEC2009-84207.

The purpose of applying a laser beam in the micro-laser assisted machining (μ-LAM) process is to preferentially heat and thermally soften the surface layer of the work piece material (4H-SiC) at the interface with a diamond cutting tool. In the μ-LAM process the laser beam (1480 nm and 400 mW) is delivered to the work piece material through a transparent diamond cutting tool. Thus the cutting tool and the laser system are integrated and coupled; in contrast with other LAM processes where the cutting tool and laser are separate and distinct systems. Scratches were made on a 4H-SiC substrate using the μ-LAM process. The characteristics of the scratches, such as depth and width, are principally a function of the cutting tool geometry, applied forces, cutting speed, and laser heating. White light interferometer microscopy and Atomic Force Microscopy (AFM) techniques were used to measure the geometry (depth and width) of the scratches. Force analysis was carried out to evaluate the laser heating effect on the cutting forces and the measured depth of cut. The force analysis included an evaluation of the mechanical work, specific energy, and understanding the effect of laser heating on the cutting process. The scratch tests performed on 4H-SiC with the laser heating showed that there is a greater than 50% reduction in relative calculated hardness values of work piece material, resulting in a significant reduction in cutting forces.

Commentary by Dr. Valentin Fuster
2009;():833-840. doi:10.1115/MSEC2009-84211.

Generally, superalloys have superior strength and toughness compared to conventional engineering material. However, while applications for such materials are growing, the improvement of their machinability has not been improved in parallel. Of particular interest to the aerospace industry, are nickel-based superalloys. Inconel 718, which is one type of nickel-based superalloy, is considered difficult-to-machine at room temperature due to the fact that it retains much of its strength at high temperatures. Conventional machining methods applied to these materials results in excessive tool wear and poor surface finish. One approach, which is becoming increasingly popular with difficult-to-machine materials, is laser assisted machining (LAM). This study assesses the effect of LAM on the machinability of Inconel 718 using a triple-layer coated carbide tool in terms of cutting forces, tool wear and surface finish. A focused Nd:YAG laser beam was used as a localized heat source to thermally soften the workpiece prior to material removal. Finishing operations were assumed throughout the experiments. Cutting tests were performed over a wide range of cutting speeds (ranging from 100 to 500 m/min) and feeds (ranging from 0.125 to 0.500 mm/rev) to determine the optimum cutting speed and feed for each tool material. Results showed a significant drop in all three components of cutting force when thermal softening caused by the laser power was in effect. A two to three fold improvement was observed in terms of surface finish and tool wear under LAM conditions when compared to conventional machining.

Commentary by Dr. Valentin Fuster
2009;():841-844. doi:10.1115/MSEC2009-84235.

Surface micro dents may act as lubricant reservoirs to reduce friction and wear in sliding and rolling contact applications. Surface patterning has become a valuable technique for fabricating micro dents. Alternative methods such as micromachining present obvious limitations in comparison with laser shock peening (LSP). In this paper, the use of LSP along with an automatic X-Y table proves to be an attractive and reliable method for producing micro dent arrays with enhanced surface integrity and free of cracks. Surface topography, residual stress, and microhardness of the fabricated micro dent arrays on polished Ti-6A1-4V have been characterized. It has shown that LSP is capable of efficiently fabricating mass micro dent arrays with controllable size. The center area of the peened dents has highest hardness. In addition, high compressive residual stress can also be created.

Commentary by Dr. Valentin Fuster
2009;():845-852. doi:10.1115/MSEC2009-84261.

On this Phase I SBIR project, Creare’s overall objective was to develop and transition a technology that will increase cutting tool life and reduce overall production costs of machining ceramic matrix composite (CMC) materials. We successfully demonstrated the feasibility of machining CMC materials using the Laser-Assisted Machining (LAM) approach, which utilizes a laser to preheat a thin layer of the CMC material prior to its removal using conventional machine tools. In particular, we demonstrated that the cutting forces were reduced by as much as 40% compared to conventional machining processes. This reduction enables increased processing speeds which decrease cycle times and overall processing costs. Additionally, we developed and validated a comprehensive thermal model for the edge machining of CMCs. When combined with the experimental results, the temperatures near the material removal interface for the optimal LAM condition were predicted.

Commentary by Dr. Valentin Fuster
2009;():853-859. doi:10.1115/MSEC2009-84317.

A unified simple predictive model has been presented for high fluence ultrashort laser ablation of metal, semiconductor and dielectric, which has very low computational cost and is very easy to apply. Unlike many other simplified models, this model does not involve any free adjustable variables. The model predictions agree well with experimental measurements for femtosecond laser ablation, while the model is not very applicable for pulse durations more than ∼10 picosecond.

Commentary by Dr. Valentin Fuster
2009;():861-865. doi:10.1115/MSEC2009-84318.

Laser beam propagation in high aspect ratio channels has been simulated by solving two-dimensional Maxwell wave equation with the finite element method. It has been found that the optical polarization direction has a very important effect on laser beam propagation in the channel, and under certain polarization direction the laser beam profile may keep changing in a very complicated way as the beam propagates through the channel. The above important effects, revealed by the numerical simulation in this paper, need to be considered to realize an accurate modeling or a good process design for laser machining of high aspect ratio microstructures.

Commentary by Dr. Valentin Fuster

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