ASME Conference Presenter Attendance Policy and Archival Proceedings

2018;():V004T00A001. doi:10.1115/MSEC2018-NS4.

This online compilation of papers from the ASME 2018 13th International Manufacturing Science and Engineering Conference (MSEC2018) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Processes: Abrasive Machining Processes: Michael P. Hitchiner Memorial Symposium

2018;():V004T03A001. doi:10.1115/MSEC2018-6592.

WC-Co coatings are extensively used in abrasion, sliding, and erosion resistance applications for its favourable mechanical properties. Nanofinishing of WC-Co coating is required for aircraft landing gear cylinder and diesel engine cylinder. Characterisation of surface topography becomes an important aspect in tribological applications as it has significant effect on the functional performance of the surfaces. In this present study, the motif analysis with 5% wolf pruning is applied to identify the significant hills for pattern reorganization of the surface texture generated by different finishing steps such as grinding, shape adaptive grinding (SAG) and chemical assisted SAG (CA-SAG). Several 3D advanced texture parameters are employed to characterize the coated surface before and after finishing in terms of surface roughness, third and fourth moments (skewness and kurtosis) of the probability density function, bearing area ratio curve and fluid retention properties of the surface. Furthermore, power spectral density (PSD) analysis is performed to analyse the unevenness and periodicity of the texture. It is observed that the fluid retention property and the bearing property of the surface improve with the subsequent finishing stage.

Commentary by Dr. Valentin Fuster
2018;():V004T03A002. doi:10.1115/MSEC2018-6615.

The high quality surface can exhibit the irreplaceable application of single crystal silicon carbide in the fields of optoelectronic devices, integrated circuits and semiconductor. However, high hardness and remarkable chemical inertness lead to great difficulty to the smoothing process of silicon carbide. Therefore, the research presented in this paper attempts to smooth silicon carbide wafer with photocatalysis assisted chemical mechanical polishing (PCMP) by using of the powerful oxidability of UV photo-excited hydroxyl radical on surface of nano-TiO2 particles. Mechanical lapping was using for rough polishing, and a material removal model was proposed for mechanical lapping to optimize the polishing process. Several photocatalysis assisted chemical mechanical polishing slurries were compared to achieve fine surface. The theoretical analysis and experimental results indicate that the material removal rate of lapping process decreases in index form with the decreasing of abrasive size, which corresponds with the model developed. After processed with mechanical lapping for 1.5 hours and subsequent photocatalysis assisted chemical mechanical polishing for 2 hours, the silicon carbide wafer obtains a high quality surface with the surface roughness at Ra 0.528 nm The material removal rate is 0.96 μm/h in fine polishing process, which is significantly influenced by factors such as ultraviolet irradiation, electron capture agent (H2O2) and acidic environment. This combined method can effectively reduce the surface roughness and improve the polishing efficiency on silicon carbide and other hard-inert materials.

Commentary by Dr. Valentin Fuster

Processes: Advances in Assisted / Augmented Manufacturing Processes

2018;():V004T03A003. doi:10.1115/MSEC2018-6359.

Fused silica is difficult to machine through conventional machining, mainly due to its high brittleness and strength, low fracture toughness and poor plastic deformation. This study was attempted to explore the machinability of fused silica with laser-assisted machining by heating workpiece through a pulse CO2 laser beam. During the LAM of fused silica, the bonding and wavelike texture on the machined surface indicated the behavior change of material deformation by the local heating in front of the cutting tool. The semi-continuous chips were obtained as an evidence of material removal mechanism which was a hybrid of quasi plastic deformation and brittle fracture. Moreover, the machinability of fused silica was evaluated. The experimental results demonstrated that considerable improvement in the machinability of fused silica was achieved such as better surface roughness, smaller cutting force as well as lower tool wear.

Topics: Lasers , Machining , Heating
Commentary by Dr. Valentin Fuster
2018;():V004T03A004. doi:10.1115/MSEC2018-6520.

To increase the fuel economy of their fleets, automotive OEMs are turning to lightweighting their vehicles through multi-material bodies. This involves forming and joining of materials with high strength to weight ratios such as aluminum and advanced high strength steels. These metals come with the downside of decreased formability and increased springback compared to conventional automotive steels. Electrical augmentation has been shown to decrease springback and increase formability in sheet forming and represents a potential solution to the use of new lightweight metals. Applied electricity is traditionally measured as a current density, however this measure struggles to represent elevated strain rate manufacturing processes. This paper examines other predictors of electrically assisted process performance such as electrical energy and power through comparison of nominally equivalent waveforms. It is found that energy is a better predictor of process performance than current density, but is dependent on the ability to predict process temperature. The leading predictive electrically assisted temperature model is examined in depth through testing of 13 different parameter sets. It is found that the model is unable to predict the correct temperature at a high current density and that the transient stress drop cannot predicted for any of the electrical cases.

Commentary by Dr. Valentin Fuster
2018;():V004T03A005. doi:10.1115/MSEC2018-6565.

Most of the existing steady state detection approaches are designed for univariate signals. For multivariate signals, the univariate approach is often applied to each process variable and the system is claimed to be steady once all signals are steady, which is computationally inefficient and also not accurate. The article proposes an efficient online method for multivariate steady state detection. It estimates the covariance matrices using two different approaches, namely, the mean-squared-deviation and mean-squared-successive-difference. To avoid the usage of a moving window, the process means and the two covariance matrices are calculated recursively through exponentially weighted moving average. A likelihood ratio test is developed to compare the difference of the two covariance matrices and to detect the steady state. The intensive numerical studies and real case study show that the proposed method can accurately detect the steady state of a multivariate system.

Topics: Steady state
Commentary by Dr. Valentin Fuster
2018;():V004T03A006. doi:10.1115/MSEC2018-6597.

A rotating core magnetorheological finishing process has been developed to finish the external cylindrical surfaces at nano-level as the conventional finishing processes like grinding cannot meet the extreme precise requirement. The quality of finished cylindrical components estimated through its geometrical accuracy, material assets, and mechanical features. The macaroni making machine driving shaft is made up of mild steel where high quality of surface finish is required. In plastic toy industries, the mild steel punches are used where a high level of surface finish is required to increase the appearance of the products and to improve its geometrical accuracy. The MR finishing process can improve the external surface quality of the cylindrical components very precisely. This result in the improvement of prolongs functional performance of the components. In the present work, the optimum process parameters are experimentally investigated for nano-finishing of the mild steel cylindrical external surfaces using the rotating core magnetorheological (MR) finishing process. The rotation of tool core, the rotation of the cylindrical workpiece, the current, and the working gap are the control process parameters which affect the finishing performance i.e. percentage change in surface roughness value. So, the effects of these process parameters on the process response such as percentage change in surface roughness value have been analyzed using signal-to-noise ratios and mean response data. The current and the rotational speed of the tool core have been found as a considerable role for increasing the percentage change in roughness value. Further, the optimum magnitude of the process parameters are predicted as the current 3A, the rotational speed of tool 500 rpm, the rotational speed of the cylindrical workpiece 80 rpm and the working gap of 0.6 mm. With the finishing of these optimum process parameters on the present developed process, the average roughness Ra value of the external surface of the mild steel cylindrical is reduced to 60 nm from the initial Ra value of 600 nm in 90 minutes of finishing. The results of scanning electron microscopy test, mirror images and roughness graphs of the finished surface have confirmed that the present finishing process can fulfil the extreme precise requirement of surface quality which is not possible by the conventional finishing processes. The extreme precise requirement of the surface quality of the external cylindrical workpieces are dealing with mild steel punches in plastic toy industries, dies, and molds, macaroni making driving shafts, armature shaft, and shafts used in gear etc.

Commentary by Dr. Valentin Fuster
2018;():V004T03A007. doi:10.1115/MSEC2018-6625.

The surface normal impingement of a cylindrical liquid jet emanating from a nozzle is of use in numerous technological applications (e.g.., waterjet cutting). If a greater distance between the nozzle and the impingement surface is allowed, then the initially continuous liquid jet may fragment into a train of discrete droplets, whose peak impact force can exceed that of an unbroken continuous liquid jet. The present study experimentally investigates the force imparted by these two distinctly different processes for identical flow conditions (i.e., velocity, jet diameter, etc.). Based on the conservation of momentum, a justification for the significantly higher peak forces observed in the droplet train case is presented.

Topics: Drops , Trains
Commentary by Dr. Valentin Fuster
2018;():V004T03A008. doi:10.1115/MSEC2018-6684.

Dendritic electrolytic copper powder was sintered using a newly developed friction sintering process. Green copper pellets of 14 mm height and 16 mm diameter were prepared at room temperature with 5-ton load and 60 seconds holding time. The pellets were sintered using a newly developed rapid, cost-effective, energy efficient, green friction sintering process that allows for easy and quick removal of sintered products. An aluminum plate of 14 mm thickness and 16.1 mm diameter through hole was used to hold green pellets during sintering. Frictional heat and pressure were applied on a top plate through a rotating 18 mm diameter, flat shoulder, WC tool. Sintering was performed at 12 kN axial load and 800 rpm tool rotational speed. Sintering temperatures were measured using K-type thermocouples. SEM (scanning electron microscope) images of fractured surfaces for sintered pellets show neck formation between copper particles. The neck formation is approximately uniform throughout the depth. This is in-line with hardness results along the thickness of the pellet. The process holds promise particularly for solid-state sintering of metal based powders.

Commentary by Dr. Valentin Fuster

Processes: Advances in Micro and Nano Manufacturing Processes and Systems

2018;():V004T03A009. doi:10.1115/MSEC2018-6311.

Recently, surface nano/micro morphologies have been applied on cutting tools for multiple purposes, such as cutting force reduction and life-span prolonging. In this study, the micro-grooves texture (MGT) and volcano-like texture (VLT) were patterned on cemented carbide (WC-Co, YG6) cutting inserts’ rake faces by YAG and fiber laser systems. The effects of laser pulse width and energy on texture dimensions were investigated, followed by the micro hardness, EDX and metallographic analyses providing detailed information for VLT’s properties and forming process. The subsequent cutting experiment tested the flat, MGT and VLT tools in turning aluminum alloy 6061 with considering the following factors: textured scale and density, coolant, cutting speed and machining type (rough or finish). VLT tools showed lower cutting forces in rough cutting, and poor compatibility to cutting coolant; MGT improves the efficiency of coolant usage. This study not only introduced VLT to cutting tools, but also revealed its comprehensive performances.

Commentary by Dr. Valentin Fuster
2018;():V004T03A010. doi:10.1115/MSEC2018-6378.

Micro structure/parts during their useful life are significantly influenced by surface roughness quality. Machining of curve shapes is a necessity in micro-milling process. However, surface roughness in micro-milling curved surfaces is more complex, and few studies on the influence factors and prediction of the micro-milled curve surface roughness in micro-milling nickel-based superalloy have been done. The purpose of this paper is to study the effects of spindle speed, the radius of ball-end mill, axial cutting depth, and feed per tooth on the curved surface roughness in micro-milling Inconel 718 process based on single factor and orthogonal experiments. Utilizing the least square method, we build a surface roughness prediction model of micro-milled Inconel 718. Finally, experiments are conducted to verify the accuracy of the developed prediction model. The results indicate that the maximum relative error is 10.68%, and the mean relative error is 8.04%, which prove that the prediction model is correct. The work can provide a reference for selection of cutting parameters in micro-milling Inconel 718.

Commentary by Dr. Valentin Fuster
2018;():V004T03A011. doi:10.1115/MSEC2018-6490.

Compared to the conventional single-point incremental forming (SPIF) processes, water jet incremental micro-forming (WJIMF) utilizes a high-speed and high-pressure water jet as a tool instead of a rigid round-tipped tool to fabricate thin shell micro objects. Thin foils were incrementally formed with micro-scale water jets on a specially designed testbed. In this paper, the effects on the water jet incremental micro-forming process with respect to several key process parameters, including water jet pressure, relative water jet diameter, sheet thickness, and feed rate, were experimentally studied using stainless steel foils. Experimental results indicate that feature geometry, especially depth, can be controlled by adjusting the processes parameters. The presented results and conclusions provide a foundation for future modeling work and the selection of process parameters to achieve high quality thin shell micro products.

Topics: Water
Commentary by Dr. Valentin Fuster
2018;():V004T03A012. doi:10.1115/MSEC2018-6494.

Smart materials are new generation materials which possess great properties to mend themselves with a change in environment. Smart materials find applications in a wide range of industries including biomedical, aerospace, defense and energy sector and so on. These materials possess unique properties including high hardness, high strength, high melting point and low creep behavior. Manufacturing of these materials is a huge challenge, particularly at the micron scale. Abrasive waterjet micromachining (AWJMM) is a non-traditional material removal process which has the capability of machining extremely hard and brittle materials such as glasses and ceramics. AWJMM process is usually performed with nozzle and workpiece placed in air. However, machining in the air causes spreading of the waterjet resulting in low machining quality. Performing the AWJMM process with a submerged nozzle and workpiece could eliminate this problem and also reduce noise, splash, and airborne debris particles during the machining process. This research investigates Submerged Abrasive Waterjet Machining (SAWJMM) process for micromachining smart ceramic materials. The research involves experimental study on micromachining of smart materials using an in-house fabricated SAWJMM setup. The effect of critical parameters including stand-off distance, abrasive grain size and material properties on the cavity size, kerf angle and MRR during SAWJMM and AWJMM processes are studied. The study found that SAWJMM process is capable of successfully machining smart materials including shape memory alloys and piezoelectric materials at the micron scale. The machined surfaced are free of thermal stresses and did not show any cracking around the edges. The critical process parameter study revealed that stand-off distance and abrasive grit size significantly affect the machining results.

Commentary by Dr. Valentin Fuster
2018;():V004T03A013. doi:10.1115/MSEC2018-6556.

We propose a manufacturing process for fabrication of long period grating (LPG) with a screw shape by a single-path scanning of femtosecond laser. The optical fiber was rotating in radial direction and traveled along the fiber-axis simultaneously while femtosecond laser irradiation. Several screw-shaped LPGs were fabricated under different parameters, such as laser power, index change length and grating period, and their transmission characteristics were investigated. Moreover, the screw-shaped LPG with complicated pitches of the screw were fabricated by adjusting the rotating speed and travelling speed. The screw-shaped LPG sensor with complex pitches had reverse bending effect that the transmission dip becomes deeper as bending curvature increases. Consequently, it was found that the screw-shaped LPG with multiple pitches of grating has a potential as the sensors for monitoring of the structural characteristics such as bending or curvature under harsh environment.

Commentary by Dr. Valentin Fuster
2018;():V004T03A014. doi:10.1115/MSEC2018-6570.

In the present study, micro-milling of aluminium 6061 alloy and copper was undertaken. TiAlN coated two-flute flat end milling cutters of 0.5 mm diameter were used for conducting micro-channel milling experiments with minimum quantity lubrication (MQL) as the cutting environment. The effect of process parameters namely cutting velocity (vc) and feed per flute (fz) on the cutting forces, surface roughness and burr width are reported. RMS values of longitudinal feed force (FX), transverse cutting force (FY) and vertical thrust force (FZ) were measured and the maximum values for Al 6061 are 0.33 N, 0.16 N and 0.21 N respectively, and the same for copper are measured to be 0.11 N, 0.17 N and 0.22 N respectively. Average surface roughness along the milling direction (Ra) at the bottom surface of the micro-channel was measured. Smoother surfaces were generated at lower feed per flute in both the materials. Ra is found to be varying from 28.2 nm to 86.9 nm for Al 6061, and for copper, the range is from 4.9 nm to 32.7 nm. SEM images of the micro-channels were analysed and top burr width was measured in both up-milling and down-milling directions. Higher feed per flute produced smaller burrs in both up-milling and down-milling directions. Maximum burr width for Al 6061 is measured to be 12.86 μm and 15.28 μm in up-milling and down-milling direction respectively, and for copper, the same are measured to be 12.84 μm and 20.46 μm respectively.

Commentary by Dr. Valentin Fuster
2018;():V004T03A015. doi:10.1115/MSEC2018-6573.

Shape Memory Alloys are smart materials that tend to remember and return to its original shape when subjected to deformation. These materials find numerous applications in robotics, automotive and biomedical industries. Micromachining of SMAs is often a considerable challenge using conventional machining processes. Micro-Electrical Discharge Machining is a combination of thermal and electrical processes, which can machine any electrically conductive material at micron scale independent of its hardness. It employs dielectric medium such as hydrocarbon oils, deionized water, and kerosene. Using liquid dielectrics has adverse effects on the machined surface causing cracking, white layer deposition, and irregular surface finish. These limitations can be minimized by using a dry dielectric medium such as air or nitrogen gas. This research involves the experimental study of micromachining of Shape Memory Alloys using dry Micro-Electrical Discharge Machining process. The study considers the effect of critical process parameters including discharge voltage and discharge current on the material removal rate and the tool wear rate. A comparison study is performed between the Micro-Electrical Discharge Machining process with using the liquid as well as air as the dielectric medium. In this study, microcavities are successfully machined on shape memory alloys using dry Micro-Electrical Discharge Machining process. The study found that the dry Micro-Electrical Discharge Machining produces a comparatively better surface finish, has lower tool wear and lesser material removal rate compared to the process using the liquid as the dielectric medium. The results of this research could extend the industrial applications of Micro Electrical Discharge Machining processes.

Commentary by Dr. Valentin Fuster
2018;():V004T03A016. doi:10.1115/MSEC2018-6665.

Nanoporous metal foams have an increasing importance in applications such as chemical catalysis, energy storage, and nanomedicine. This paper examines a simple strategy for controlling the pore volume fraction and pore size of nanoporous films synthesized by dealloying thin-films. By means of controlling the temperature and concentration of nitric acid in dealloying of AgAu thin-films, partially dealloyed AgAu nanoporous films are produced with a high degree of control over the pore size and pore volume fraction. Such capability enables the design of nanoporous metal catalysts materials with desired morphology.

Topics: Metals , Porosity
Commentary by Dr. Valentin Fuster
2018;():V004T03A017. doi:10.1115/MSEC2018-6687.

Microsphere Photolithography (MPL) uses a self-assembled array of transparent microspheres to focus incident ultraviolet radiation and produce an array of photonic jets in photoresist. Typically, the microspheres are self-assembled directly on the photoresist layer and are removed after exposure during development. Reusing the microsphere array reduces the expense of the process. A mask is formed by transferring the self-assembled microsphere array to a transparent tape. This can be used for multiple exposures when pressed into contact with the photoresist. This paper demonstrates the use of this process to pattern infrared metasurface absorbers and discusses the effects of the mask-based MPL process on the metasurface performance.

Commentary by Dr. Valentin Fuster

Processes: Advances in Modeling, Analysis, and Simulation of Manufacturing Processes

2018;():V004T03A018. doi:10.1115/MSEC2018-6309.

This study is presenting a non-local closed-form solution for interfacial stress/strain and the warpage deformation for thin trilayer plate structures under thermal cycling.

Based on the theory of geometric scale dependency of the material behavior, the material properties of a thin multi-layer inter-bonded structures substantially differ from those determined based on the bulk material samples. Hence the real mechanical properties for such thin layers are often unavailable and difficult to obtain.

This paper puts forward a method to provide a solution for thermomechanical behavior of trilayer constituents with high accuracy at real scale. Present study demonstrates that the constitutive behavior of multilayer plate’s constituents can be inversely determined so long as the plate’s global deformation can be made available by measurement.

To achieve most accurate determination of the material properties, measurements with high accuracy is required. The paper also presents the advanced method of shadow moiré that have applied to obtain warpage deformation of real life trilayer test specimens under thermal cycling.

Using this method, the experimentally determined global deformation (warpage) of a trilayer structure were correlated with the analytical model solved for warpage deformation. The correlation was then progressively optimized to result in material properties of the constituents. The bonding layer properties are called determined, once the correlation reaches over 85%.

There exist a variety of different multilayer bonded structures, which are usually made with advanced manufacturing processes. Regardless of design layout and materials constitutive relations, the application can be implemented in characterizing multiply stacked trilayer structures.

Commentary by Dr. Valentin Fuster
2018;():V004T03A019. doi:10.1115/MSEC2018-6314.

This paper reports the development of an efficient iso-scallop tool path planning strategy for machining of freeform surfaces on a three axis CNC milling center using the point cloud as the input. Boundary of the point cloud is chosen as the Master Cutter Path, using which the scallop points are computed. Adjacent side tool paths are computed using these scallop points and the path planning process is completed till the entire surface is covered. The system generates post-processed NC program in ISO format which was extensively tested for various case studies. The results were compared with the iso-planar tool path strategy from commercial software. Our system was found to generate efficient tool path in terms of part quality, productivity and storage memory.

Commentary by Dr. Valentin Fuster
2018;():V004T03A020. doi:10.1115/MSEC2018-6327.

Face milling commonly generates surface quality of roughness or variation, especially severe for the milling of large-scale components with complex surface geometry such as cylinder block, engine head, and valve body. Thus surface variation serves as an important indicator both for machining parameter selection and components’ service performance. Conversely the optimization of machining process is a vital objective to improve the surface quality and its service life of machined components. Many researchers have dedicated to the prediction of machined surface variation generated by face milling using numerical or experimental methods. However, the numerical methods based on finite element analysis (FEA) are good at predicting local deformation of workpiece under instantaneous milling force, particularly applied for online compensation in face milling. Whereas experimental methods can only be used to estimate whole surface variation through reverse correlation analysis of measured data and processing variables. Therefore, an efficient and comprehensive numerical model is highly desired for the prediction of surface variation of entire surface. This study proposes a coupled numerical simulation method, updating FE model literarily based on the integration of data from ABAQUS and MATLAB, to predict surface variation induced by the face milling of large-scale components with complex surfaces. Using the coupled model, the 3D variation of large-scale surface can be successfully simulated by considering face milling process including dynamic milling force, spiral curve of milling trajectory, and intermittently rotating contact characteristics. Surface variation is finally represented with point cloud from totally iterative FE analysis and verified by face milling experiment. Result shows that the new prediction method can simulate surface variation of complex components. Based on the verified model, a set of numerical analyses are conducted to evaluate the effects of local stiffness non-homogenization and milling force variation on machined surface variation. It demonstrates that surface variation with surface peaks and concaves is strongly correlated with local stiffness non-homogenization especially in feed direction. Thus the coupled prediction method provides a theoretical and efficient way to study surface variation induced by face milling of large-scale complex components.

Topics: Engines , Milling
Commentary by Dr. Valentin Fuster
2018;():V004T03A021. doi:10.1115/MSEC2018-6356.

Ultrasonic welding is a solid-state joining process which uses ultrasonic vibration to join materials at relatively low temperatures. Ultrasonic powder consolidation is a derivative of the ultrasonic additive process which consolidates powder material into a dense solid block without melting. During ultrasonic powder consolidation process, metal powder under a compressive load is subjected to transverse ultrasonic vibrations resulting in a fully-dense consolidated product. While ultrasonic powder consolidation is employed in a wide variety of applications, the effect of critical process parameters on the bonding process of powder particles during consolidation is not clearly understood. This study uses a coupled thermo-mechanical finite element analysis technique to investigate the effect of critical process parameters including vibrational amplitude and base temperature on the stress, strain, and particle temperature distribution during the ultrasonic powder consolidation process. The study finds that during this process, the ultrasonically vibrating tool imparts cyclic vibratory shear stress on the particles. The simulation also revealed that the particle temperature just reaches the recrystallization point. Higher vibration amplitude imparted higher frictional heat on the particles, thereby aiding the consolidation process. The simulation study also showed indications of thermal softening and restricted grain boundary sliding during the ultrasonic powder consolidation process. The outcomes of this study can be used to further the industrial applications of ultrasonic powder consolidation process as well as other ultrasonic welding based processes.

Commentary by Dr. Valentin Fuster
2018;():V004T03A022. doi:10.1115/MSEC2018-6373.

In this paper, a 2D milling stability analysis is reduced to a 1D problem by performing a modal analysis on an oriented transfer function matrix under a given feed direction. The oriented frequency response function (FRF) of the oriented transfer matrix are obtained as explicit functions of the radial immersion and feed direction. At different feed directions in most of the lower immersion range, the process is demonstrated to be the least stable when the modal direction of the directional matrix is oriented at 45° and 225° and in the −45° and 135°, yielding a local minimum critical depth of cut, regardless of up or down cuts. At higher immersion, the worst critical depth of cut is dominated by the lower frequency mode, and becomes a constant, independent of the feed direction at full cut. When the modal direction is oriented along the x or y axes, the process has a local maximum critical depth of cut.

Topics: Chatter , Milling
Commentary by Dr. Valentin Fuster
2018;():V004T03A023. doi:10.1115/MSEC2018-6386.

A new analytical model is proposed to predict the residual stress in the milling process of Inconel 718 based upon the mechanics analysis of microstructural evolutions. The model proposes to quantify the effects of dynamic recrystallization process on the material flow stress under combined thermal-mechanical loadings in machining. Physics-based mechanistic model is applied to predict the percentage of dynamic recrystallization and the grain size as functions of the milling process parameters and materials constative attributes. The variation of grain size is expected to alter the yield stress, and such dependency relationship is applied to predict the flow stress, which is also dependent on strain, strain rate, and temperature. The time-varying trajectory of residual stress is then predicted at each milling rotation angle through the transformation from milling to equivalent orthogonal cutting, the calculation of stress distribution in loading process, and the stress change during relaxation. The results of analytical model are validated through numerical prediction. The residual stress profile predicted by proposed analytical model matches better with results from numerical model comparing with model without consideration of dynamic recrystallization, especially within subsurface area, with improved accuracy of peak compressive residual stress prediction.

Commentary by Dr. Valentin Fuster
2018;():V004T03A024. doi:10.1115/MSEC2018-6416.

The SiC ceramic ductile grinding, which can obtain crack-free ground surface, is a challenge in brittle material machining. To understand the brittle material ductile grinding mechanism in the nanoscale, a molecular dynamics (MD) model is built to study the single diamond grit grinding silicon carbide ceramic. Through analyzing the MD simulation process, the grit forces the SiC to deform and form the chip through the plastic deformation and flow. The ground surface has no crack on the surface and damage layer thickness is less than one atom layer under the nanoscale depth of cut, which indicates the nanogrinding can achieve the pure ductile grinding for the SiC ceramic and obtain a crack-free and high-quality ground surface. Grinding force, stress, temperature, and specific energy increase with the wheel speed and depth of cut due to the higher grinding speed and a smaller depth of cut can generate a higher density of defects (vacancies, interstitial atoms, and dislocations) on the workpiece, which can make the silicon carbide ceramic more ductile. The high wheel speed is favorable for the ductile grinding.

Commentary by Dr. Valentin Fuster
2018;():V004T03A025. doi:10.1115/MSEC2018-6466.

In the present study, a voxel based model for the interaction between cutting teeth of an arbitrary end mill geometry and a workpiece is presented. In this framework, the workpiece geometry is modeled using a voxelized representation that is dynamically updated as material is locally removed by each tooth of the cutting tool. A ray casting approach is used to mimic the process of the rake face of a tool moving through the workpiece material and to calculate the undeformed chip thickness and its variation in time. The resulting voxel based model framework was validated by comparison of predictions with experimentally measured milling forces. The results demonstrate the model’s ability to accurately simulate the interaction of cutting teeth with the bulk material of the workpiece. Implications of this new voxel based model framework are briefly discussed in terms of utility for predicting local surface finish and computational scalability of complex cutting configurations.

Commentary by Dr. Valentin Fuster
2018;():V004T03A026. doi:10.1115/MSEC2018-6469.

An Ultrasonic Powder Consolidation is an additive manufacturing technique that utilizes high-frequency vibrations to consolidate micro/nano powder materials to fully dense and near to net-shaped parts. Unlike traditional powder consolidation techniques such as sintering, shock wave-based and pressure-based processes, the consolidation during Ultrasonic Powder Consolidation process happens at relatively low temperatures and pressures within few seconds or less. Ultrasonic Powder Consolidation process presents several inherent advantages including low power consumption, low cost and zero thermal stresses on the consolidated parts. Experimental studies have shown that Ultrasonic Powder Consolidation process is capable of successfully consolidating powders of metals and metal-matrix composites. While Ultrasonic Powder Consolidation process promises several potential applications, the mechanism of bond formation between the consolidated metal powders is not completely understood. This research uses Molecular Dynamics simulation technique to investigate the underlying bond formation and consolidation mechanisms involved in Ultrasonic Powder Consolidation process. The research also explores the effects of critical process parameters including vibration frequency, amplitude and initial temperature on the quality of the consolidated part. The study found that high-frequency vibrations cause high interfacial stresses resulting in acoustic softening and high plastic deformation of the nanoparticles. The study revealed that the overall atomistic temperature does not exceed the melting point of the material. The study also found that the vibration amplitude and frequency played a significant role in the consolidation process. Finally, the simulation study showed that the high-frequency vibration leads to large plastic deformations at ultra-high shear strain rates causing the interfacial atoms to interlock with each other resulting in high densification and consolidation. The results of this study would augment the ongoing experimental studies on Ultrasonic Powder Consolidation process which would help realize the promised potentials of this low temperature – low-pressure consolidation technique.

Commentary by Dr. Valentin Fuster
2018;():V004T03A027. doi:10.1115/MSEC2018-6473.

In this paper, a coupled Eulerian-Lagrangian (CEL) finite element model is developed based on FEM software package Abaqus to solve the evolution of the dislocation density and grain size simultaneously. This validated CEL FEM model is then utilized to investigate the effects of microgrooved cutting tools on the evolution of dislocation density and grain size in orthogonal cutting of commercially pure titanium (CP Ti). Microgrooved cutting tools are cemented carbide (WC/Co) cutting inserts with microgrooves on the rake face. The effects of microgroove width and microgroove convex width are investigated in terms of cutting force, chip morphology, dislocation density, and grain size. It is concluded that this CEL FEM model can capture the essential features of orthogonal cutting of commercially pure titanium (CP Ti) alloy using microgrooved cutting tools. It is also concluded that microgroove width and convex width have substantial influence on the dislocation density profiles and grain size profiles along the depth from the machined surface and the tool-chip interface, respectively. This conclusion provides insightful guidance for altering the surface integrity of the machined surface based on needs.

Commentary by Dr. Valentin Fuster
2018;():V004T03A028. doi:10.1115/MSEC2018-6474.

In this paper, the commercial FEM software package Abaqus is employed to model a novel nanomachining process, in which an atomic force microscope (AFM) is used as a platform and the nano abrasives injected in slurry between the workpiece and the vibrating AFM probe impact the workpiece and result in nanoscale material removal. Diamond particles are used as loose abrasives. The ductile material model is used to describe the behavior of the silicon workpiece. The effects of impact speed, impact angle, and the frictional coefficient between the workpiece and abrasives on material removal mechanism are investigated. It is found that the impact speed, impact angle, and frictional coefficient between the silicon workpiece and nanoabrasives have big influence on material removal volume in this novel nanomachining process.

Commentary by Dr. Valentin Fuster
2018;():V004T03A029. doi:10.1115/MSEC2018-6486.

Tube forming is one of the main manufacturing techniques for processing of tubular components. This process is subdivided depending on the processing i.e., tube end forming either to expand or reduce the section. One of these tube end forming techniques is a flaring process. Most applications for flaring tube ends, utilizes a conical tool for flaring the tube either till a particular deformation to achieve a desired shape or till failure to characterize the material properties. The relationship between the flaring behavior during the process based on the outer diameter and thickness of the tube was experimentally characterized in this paper for variety of tube sizes. Further flaring limits were analyzed in these considered tube sizes. For this four outer diameter to thickness ratio were experimented and results were analyzed. Further numerical simulations were performed to match the results. A closer look on the required force-displacement curve is presented and unique regions were identified. Based on the data an empirical equation is proposed. This equation provides a concept based on material or process stiffness. It is believed that once an equation is established and variables are linked to the parameter a more better prediction can be carried out for flaring the tubes.

Commentary by Dr. Valentin Fuster
2018;():V004T03A030. doi:10.1115/MSEC2018-6493.

This paper addresses a bi-objective distribution permutation flow shop scheduling problem (FSP) with setup times aiming to minimize the makespan and the total tardiness. It is very difficult to obtain an optimal solution by using traditional approaches in reasonable computational time. This paper presents an appropriate non-dominated sorting Genetic Algorithm III based on the reference point. The NEH strategy is applied into the generation of the initial solution set. To validate the performance of the NEH strategy improved NSGA III (NNSGA III) on solution quality and diversity level, various test problems are carried out. Three algorithms, including NSGA II, NEH strategy improved NSGA II(NNSGA II) and NNSGA III are utilized to solve this FSP. Experimental results suggest that the proposed NNSGA III outperforms the other algorithms on the Inverse Generation Distance metric, and the distribution of Pareto solutions are improved excellently.

Topics: Flow (Dynamics)
Commentary by Dr. Valentin Fuster
2018;():V004T03A031. doi:10.1115/MSEC2018-6498.

In this paper, numerical investigation of the effects of cutting conditions in slot up milling of Ti-6Al-4V is conducted using Finite Element Method (FEM). Experiments are conducted to validate the FEM models. The validated models are then used to predict the cutting force components when different cutting conditions are applied. It is found that cutting speed, feed rate, and depth of cut have strong influence on cutting force components and tool temperature. This research provides insightful guidance for selecting optimal cutting conditions for slot milling of Ti-6Al-4V.

Topics: Milling
Commentary by Dr. Valentin Fuster
2018;():V004T03A032. doi:10.1115/MSEC2018-6504.

Liquid Assisted Laser Beam Micromachining (LA-LBMM) process is advanced machining process which can overcome the limitations of traditional laser beam machining processes. LA-LBMM process uses a layer of a liquid medium such as water above the substrate surface during the application of laser beam. During LA-LBMM process, the liquid medium is used both in static mode in which the water is still or in a dynamic mode in which the water flows over the substrate with a specific velocity. Experimental studies on LA-LBMM process have shown that the cavity machined has a better surface finish due to a reduction in the amount of re-deposition and recast material. While LA-LBMM process promises significant improvement in laser-based micromachining applications, the process mechanisms involved in LA-LBMM process is not well understood. In the past, finite element simulation studies on LA-LBMM process is studied which could only find the temperature distribution on the substrate during machining. A clear understanding of the role of water medium during the LA-LBMM process is lacking. This research involves the use of Molecular Dynamics (MD) simulation technique to investigate the complex and dynamic mechanisms involved in the LA-LBMM process both in static and dynamic mode. The results of the MD simulation are compared with those of Laser Beam Micromachining (LBMM). The study revealed that machining during LA-LBMM process showed higher removal compared with LBMM process. The LA-LBMM process in dynamic mode showed lesser material removal compared with static mode as the flowing water carrying the heat away from the machining zone. Formation of nanoscale bubbles along with shockwave propagation is observed during the simulation of LA-LBMM process. The findings of this study provide further insights to strengthen the knowledge base of LA-LBMM process.

Commentary by Dr. Valentin Fuster
2018;():V004T03A033. doi:10.1115/MSEC2018-6505.

Titanium alloys are widely utilized in aerospace thanks to their excellent combination of high-specific strength, fracture, corrosion resistance characteristics, etc. However, titanium alloys are difficult-to-machine materials. Tool wear is thus of great importance to understand and quantitatively predict tool life. In this study, the wear of coated carbide tool in milling Ti-6Al-4V alloy was assessed by characterization of the worn tool cutting edge. Furthermore, a tool wear model for end milling cutter is established with considering the joint effect of cutting speed and feed rate for characterizing tool wear process and predicting tool wear. Based on the proposed tool wear model equivalent tool life is put forward to evaluate cutting tool life under different cutting conditions. The modelling process of tool wear is given and discussed according to the specific conditions. Experimental work and validation are performed for coated carbide tool milling Ti-6Al-4V alloy.

Commentary by Dr. Valentin Fuster
2018;():V004T03A034. doi:10.1115/MSEC2018-6509.

Roll diameter surface deviations can generate significant strip flatness defects in the cold rolling of thin gauge metal sheet. The resolution of roll profile deviations can vary between 0.001 and 0.01 mm. In such a high-fidelity contact problem, lack of availability of the measured data, and high computational cost in using the data in simulations, make it very difficult to predict the effects of such deviations. Nonetheless, an understanding of how high-fidelity roll profile deviations can lead to rolled sheet flatness defects is very important since such defects may be unrecoverable. This paper evaluates the ability of a simplified mixed finite element roll-stack model to predict contact behavior effects on the rolled sheet created by high-fidelity roll profile deviations. The simplified finite element method combines 3D Timoshenko beam elements with Winkler elastic foundations. The beam elements are used to capture bending and shear deformation, while the Winkler foundations are tested for their ability to accurately and efficiently capture the high-fidelity flattening-type contact behavior. Results for a simple roll and plate contact case study indicate favorable comparison with the results obtained from a large-scale commercial finite element simulation, and yet the methods requires a small fraction of the associated computing time and memory. The work also offers significant insights into the sheet flatness defects that can arise in cold rolling because of low magnitude but high fidelity roll diameter machining errors.

Commentary by Dr. Valentin Fuster
2018;():V004T03A035. doi:10.1115/MSEC2018-6510.

Design for manufacturing (DFM) is an important concept that helps to incorporate manufacturability considerations at early design stage. Development of automated DFM tools has become important especially when design and manufacturing are being done by different teams often distantly located. An automated system for design for manufacturability analysis for die-cast parts has been presented in this paper. The paper discusses: (i) knowledgebase of DFM guidelines (ii) die casting feature extraction from part CAD model, and (iii) automated system for DFM analysis and model updation of the die-cast part CAD model. The capabilities of the system are demonstrated by applying it on die cast part CAD models. The results have been validated with the industrial experts. The present system works with CAD models having features such as boss, rib, hole and draft, created using feature based modeling.

Commentary by Dr. Valentin Fuster
2018;():V004T03A036. doi:10.1115/MSEC2018-6541.

In this paper an inverse method is presented to evaluate the inner workpiece temperature distribution during cryogenic turning of metastable austenitic steel AISI 347 utilizing a FE representation of the process. Temperature data during the experiments is provided by thermocouples and a commercial thermo-graphy system. A constant cutting speed at two varying feeds are investigated. Inverse parameter verification by aligning simulated and experimental data in a least squares sense is achieved. A heat flux from tool to workpiece as well as heat transfer coefficients for forced convection by air and by carbon dioxide as cryogenic coolant are identified for each set of cutting parameters. Rigid body rotation in the model is considered applying convective time derivatives of the temperature field. Unphysical oscillations occurring in regions of high Péclet numbers are suppressed utilizing a streamline-upwind/Petrov-Galerkin scheme.

Commentary by Dr. Valentin Fuster
2018;():V004T03A037. doi:10.1115/MSEC2018-6551.

This paper aims to investigate the effectiveness of super-hard ceramic coatings by evaluating tool wear when drilling carbon fiber reinforced plastics (CFRP) composite. The drilling experiments of CFRP are conducted with diamond-like coating (DLC) coated, AlMgB14 (BAM) coated, AlCrSiN coated, and uncoated tungsten carbide drills. Tool wear evolution is measured qualitatively as well as quantitatively using the scanning electron and confocal laser scanning microscopes. Both DLC and BAM coatings failed when drilling CFRP only within 10 holes while AlCrSiN coating did not fail. Failure mechanisms of each coating when drilling CFRP are discussed.

Commentary by Dr. Valentin Fuster
2018;():V004T03A038. doi:10.1115/MSEC2018-6576.

In micro machining processes, achieving the required accuracy and surface quality in the first attempt is of utmost importance. Because, it is challenging to perform a secondary operation in a microscaled structure due to re-positioning inaccuracies. In the micro grinding process, geometrically deviated structures are common due to the low depth of cuts compared to the size of abrasive grits. Moreover, abrasive grits random distribution on the tool surface is also a factor. In most of the cases, the number of grits participating in the grinding process is countable, unlike macro grinding process. Hence, the position of every grit on the micro tool surface is important. In the micro grinding process, geometrically deviated structures are common due to the low depth of cuts compared to the size of abrasive grits. In this case, the depth of cut values will be less than the size of the abrasive grits. In that case, the abrasive grits located at the tool bottom surface highly influence the quality of the component produced. In the present work, a simulation study has been performed for micro grinding process to understand the influence of tool topography on the micro channel geometrical deviations, especially when the depth of cut is less than the size of the grits. Simulation results showed the importance of the number of grits, their protrusion heights and radial positions on the tool bottom surface at small depths of cuts to minimize the geometrical deviations.

Commentary by Dr. Valentin Fuster
2018;():V004T03A039. doi:10.1115/MSEC2018-6577.

In this paper, a Coupled Eulerian Lagrangian (CEL) finite element model (FEM) was developed to simulate the friction stir spot welding (FSSW) of commercial pure copper. Through simulations results, the paper presents and discusses the effect of FSSW process parameters; namely rotational speed, plunging rate and dwell time, on the developed temperatures and their distribution within the workpiece as well as material flow and deformation. Model validation showed a good agreement between predicted temperature history and the experiment one, with a maximum error of 6%. Furthermore, the predicted formation of flash was also found in good agreement with the experiment with an error of only 7%. Simulation results predicted peak temperature and plastic strain among all studied welding conditions were 920 K and 3.5 respectively at 1200 rpm rotational speed, 20 mm/min plunging rate and 4 seconds dwell time, which is approximately 70% of the melting point of pure copper.

Commentary by Dr. Valentin Fuster
2018;():V004T03A040. doi:10.1115/MSEC2018-6581.

In this paper, a multi-objective hybrid flowshop rescheduling problem (HFRP) is addressed in a dynamic shop environment where two types of real-time events, namely machine breakdown and job cancellation, simultaneously happen. For the addressed problem, two objectives are considered. One objective concerning the production efficiency is minimizing the maximum completion time or makespan, while regarding with the instability, the total number of the jobs assigned to different machines between the revised and the origin schedule is considered. A multi-objective evolutionary algorithm based on decomposition (MOEA/D) is applied to solve this problem. In the algorithm, the weighted sum approach is used as the decomposition strategy. The algorithm is, then, rigorously compared with three state-of-the-art evolutionary multi-objective optimizers, and the computational results demonstrate the effectiveness and efficiency of the algorithm.

Commentary by Dr. Valentin Fuster
2018;():V004T03A041. doi:10.1115/MSEC2018-6599.

This paper evaluates the performances of dry, minimum quantity lubrication (MQL) and MQL with nanofluid in turning the most common titanium (Ti) alloy, Ti-6Al-4V, in a solution treated and aged (STA) microstructure. In particular, the nanofluid evaluated here is vegetable oil (rapeseed) mixed with small concentrations of exfoliated graphite nanoplatelets (xGnP). The focus of this paper is on turning process because it poses a challenging condition to apply oil droplets directly onto the tribological surfaces of a cutting tool due to the continuous engagement of tool and work material. A series of turning experiments was conducted with uncoated carbide inserts while measuring the cutting forces with the dynamometer under various conditions to determine its effectiveness and optimal MQL condition in turning. The worn inserts are retrieved to measure flank and crater wear using confocal microscopy. This preliminary experimental result shows that the use of MQL and nanofluid is effective in improving the machinability of Ti alloys in turning processes.

Commentary by Dr. Valentin Fuster
2018;():V004T03A042. doi:10.1115/MSEC2018-6600.

Low energy and volumetric density of cellulosic biomass has been a challenge hindering its large-scale utilization as a bioenergy resource. Torrefaction is a thermochemical pretreatment process that can significantly enhance the properties of biomass as a fuel by increasing the heating value and thermal stability of biomass materials. Densification of cellulosic biomass by pelleting can greatly increase the volumetric density of biomass to improve its handling efficiency. Currently, torrefaction and pelleting are processed separately, which consumes a great amount of time and energy. In addition, it is more difficult to pellet torrefied biomass than untreated biomass. Synchronized ultrasonic torrefaction and pelleting has been developed to address these challenges. Synchronized ultrasonic torrefaction and pelleting can produce pellets of high energy and volumetric density in a single step, which tremendously reduces the time and energy consumption compared to that by the prevailing multi-step method. This novel fuel upgrading process can increase biomass temperature to 473–573 K within tens of seconds to realize torrefaction. Studying the temperature distribution is a crucial key to understand the fuel upgrading mechanism since pellet energy density, thermal stability, volumetric density, and durability are all highly related to temperature. In this research, a physics-based temperature model is developed to explain torrefaction temperatures measured experimentally and to provide guidelines to optimize process variables to produce high quality pellets that can be used as a sustainable fuel.

Commentary by Dr. Valentin Fuster
2018;():V004T03A043. doi:10.1115/MSEC2018-6607.

In the present work, Stress corrosion cracking (SCC) and its mechanical behavior are presented. SCC represents complex behavior due to electrochemical and mechanical interaction. Damage models are proposed to predict crack initiation time for stainless steel under constant load using the concept of continuum damage mechanics to show incremental damage accumulation which finally leads to failure of the material. Two damage models applicable to prediction of damage in SCC, Lemaitre damage model and damage driving force model proposed by Kamaya are compared. The comparative study of the results obtained by these damage models shows that in Lemaitre damage law cracks initiate randomly while in damage driving force model the stress concentration occurs around the periphery of damaged element results in increased damage force. The study can be used to estimate the crack initiation time in SCC under corrosive atmosphere.

Commentary by Dr. Valentin Fuster
2018;():V004T03A044. doi:10.1115/MSEC2018-6647.

Carbon fiber reinforced plastic (CFRP) are advanced engineering materials which are recognized as the most sought-after composite for several industrial applications including aerospace and automotive sectors. CFRP have superior physical and mechanical properties such as lightweight, high resilience, high-durability and high strength-to-weight ratio. CFRP composites stacked up with titanium to form multi-layered material stacks to enhance its load bearing capability. Traditional methods of stacking up CFRP and titanium involves using either high strength adhesives or rivets and bolts. The laminate structures joined by these methods often tend to fail during high load-bearing applications. Conventional metal welding technologies use high heat causing high thermal stresses and microstructural damages. Ultrasonic welding is a solid-state joining process, which has the capability of welding dissimilar materials at relatively low temperatures using ultrasonic vibration. Ultrasonic additive manufacturing (UAM) process is an ideal method to weld CFRP and Titanium. During the ultrasonic welding process, two dissimilar materials under a continuous static load are subjected to transverse ultrasonic vibrations, which results in high stress and friction between the two surfaces. This research focuses on the study of ultrasonically welding CFRP and Titanium stacks using UAM process. The study involves experimentation performed on an in-house built UAM setup. Finite element analysis is performed to understand the distribution stresses and strains during the UAM process. In this study, CFRP and Titanium layers are successfully welded using UAM process without causing any melting or significant heating. The finite element analysis study revealed that during UAM process, CFRP/Titanium stacks are subject to repeated cyclic shear stress reversals resulting in a strong weld joint. The stress-strain diagram during the process showed a considerable increase in plastic strain during the UAM process. The outcomes of this study can be used to further the industrial applications of the ultrasonic additive process as well as other ultrasonic welding based processes involving dissimilar materials.

Commentary by Dr. Valentin Fuster
2018;():V004T03A045. doi:10.1115/MSEC2018-6696.

Direct metal deposition (DMD) is a major additive manufacturing (AM) process, which employs high energy beams as the heat source to melt and deposit metals in layerwise fashion so that complex structural components can be directly obtained. Similar to other metal AM processes, DMD is a complicated thermo-mechanical process, characterized by fast scan rates, large thermal gradients, rapid material phase transformations, and cyclic non-uniform temperature changes. Accurate and efficient computation of the thermal field during the DMD process is essential for understanding the fundamental microstructure evolution and developing the optimization strategy. In this paper, we aim to develop an open-source and fast computation tool for analyzing the heat transfer during the DMD process, which is based on the finite volume formulation and the quiet element method and allows development of customized functionalities at the source level. A computing tool is developed in MATLAB for fast prediction of the temperature field during metal additive manufacturing, and compared against the regular finite element analysis using a commercial software. The preliminary results show that for a system of 14400 cells, deposition of a single path takes 174 s using the commercial software, and 15.8s to 81s depending on the setting of convergence criterion using the in-house code. This represents a time reduction ranged from 90.9% to 53.4%, and the overall error is around 12.1%.

Topics: Metals , Computation
Commentary by Dr. Valentin Fuster
2018;():V004T03A046. doi:10.1115/MSEC2018-6706.

Laser shock peening (LSP) is an advanced surface treatment technique that can extend fatigue life in metallic components by inducing near-surface compressive residual stresses. In this study, LSP was implemented to induce compressive residual stresses and modify material properties of selective laser melted (SLM) aluminum A357 specimens. An initial hypothesis on the effect of LSP during tension testing was formulated and tested using finite element simulation. The hypothesis was that, due to the LSP-induced tensile residual stress field in the middle of the specimen cross sections, yielding was expected to initiate in this region. True stress-strain curves of two as-built (AB) and two laser shock peened samples were obtained through transverse tensile tests. The single explicit analysis using time dependent damping (SEATD) technique was used to simulate LSP process utilizing Johnson-Cook (J-C) constitutive parameters. J-C parameters for the cast A357 alloy were used for preliminary study. This was followed by the simulation of the transverse tensile test. J-C parameters for SLM A357 alloy were then empirically estimated, and simulations were repeated accordingly. It was found that the specific LSP pattern induced tensile residual stresses along the edges as well as the middle of the test specimen’s cross-section. Axial residual stress and yield strength profiles along three different paths on specimen’s cross-section were compared and yield regions were investigated. This supported the initial hypothesis, but also provided for a more detailed understanding of actual tensile test failure in the specific SLM A357 specimens for the given LSP treatment. In addition, the same LSP treatment on SLM A357 alloy resulted in lower magnitude of compressive residual stress than for cast A357 aluminum alloy.

Commentary by Dr. Valentin Fuster

Processes: Advances in Nontraditional Manufacturing Processes

2018;():V004T03A047. doi:10.1115/MSEC2018-6321.

The electronics industry recognizes the need for high-temperature electronics (HTE) particularly for aerospace and geothermal applications. HTE is generally defined as robust operation in temperatures up to 300°C. A major constraint to HTE is high temperature magnet wire which is pervasive in electronic component windings and signal wire for sensors. The magnet wire constraint is caused by the temperature limits of the thin Polytetrafluoroethylene (PTFE) and Fluorinated Ethylene Propylene (FEP) coatings applied to HT magnet wire that limits the operating temperature to 220°C. [1], [2] There are coatings, particularly parylene-based coatings such as parylene HT®, that would greatly improve HT magnet wire, signal wire, and create the potential for subminiature thermocouple (TC) sensors; however, the slow vapor deposition process required to apply parylene is generally thought impractical for use in pore-free coating of long lengths of small diameter wire. For this research, experiments were first performed coating small diameter, wire product prototypes in standard batch vacuum chambers utilizing static fixtures. Finding this approach impractical we devised a new process utilizing a piezo-crystal electrodynamically actuated fixture of 14” diameter by 18” height that supports a web of one 24,500’ long, continuous small-diameter wire. A prototype dynamic fixture was built and a trial run successfully coated a 1500’ length of 0.005” diameter copper wire with Parylene HT®. This successful demonstration was the basis for a DOL Phase I SBIR to explore the feasibility of electrodynamically actuated devises that would synchronize horizontal and vertical actuation to drive horizontal motion to the wire web to enable a continuous reel-to-reel operation for parylene vapor deposition. This is discussed in future work.

Commentary by Dr. Valentin Fuster
2018;():V004T03A048. doi:10.1115/MSEC2018-6344.

Minimum Quantity Lubrication or MQL is an increasingly used technique for metal cutting operations and it has become an attractive alternative for machining parts at big scale production. However, fully lubricated conditions are still in use for machining special materials so that surface finish, tool wear, and temperature distribution levels remain at optimum levels. On the other hand, dry condition machining is in use as well although with some restraint due to issues with material burr, surface roughness, and tool wear. The main purpose of this work is to analyze the effects of cutting fluid flow rate, its application mechanisms, and cutting speed on surface roughness and establish the lowest possible cutting fluid flow rate that yields to minimum surface roughness (Ra). To achieve the objective, a set of experiments was performed using a Computer Numerical Control (CNC) lathe instrumented with a Kistler 9121 dynamometer and a customized cutting fluid application system to obtain coefficients of friction and cutting forces. Finally, a previously 2D finite element analysis (FEA) simulation from Akbar et al. [1] is applied and compared to experimental results to find out if the cutting force can be predicted. A first regression model that correlates cutting force and surface roughness is posed, so that FEA simulation can be implemented to predict the final surface roughness. AISI 4140 machinery steel in annealed condition is used to carry out the simulated and experimental work.

Commentary by Dr. Valentin Fuster
2018;():V004T03A049. doi:10.1115/MSEC2018-6348.

Electrochemical discharge machining (ECDM), also known as spark assisted chemical engraving (SACE), is an effective micro-machining process for machining of electrically nonconducting materials. It involves melting and etching process under the high electrical discharge on the electrode tip during electrolysis that enables the ECDM process to machine very hard and non-conducting materials such as borosilicate glass, quartz, ceramics etc. efficiently and economically. In the current study micro holes are machined on borosilicate glass with an electrolyte mixed with graphite powder. The conductive graphite powder in electrolyte has shown improvement in machining with more quantity of spark during machining. The main parameters taken in the study are voltage, tool rotation and duty factor along with concentration of powder in electrolyte. The main output responses taken in the study are Material Removal Rate (MRR) and lower Radial Overcut (ROC) along the machined holes. A multi-objective optimization is carried out for higher MRR and lower ROC with Grey Relation Analysis (GRA) in order to obtain the best parameters combination. From the experimental study the optimum values of parameters for MRR and ROC are found to be, voltage of 40 V, Graphite powder concentration 1.25% by weight, duty factor 70% and tool rotation of 500 rpm. From the microscopic images of the machined surface, presence graphite powder in electrolyte has improved the machined features due to its conductive nature.

Topics: Electrolytes
Commentary by Dr. Valentin Fuster
2018;():V004T03A050. doi:10.1115/MSEC2018-6352.

Magnetic field assisted finishing process is a nanofinishing process which uses magnetic field for precise control of finishing forces. Magnetorheological fluid mixed with diamond abrasive particles in base medium of glycerol, hydrofluoric acid, nitric acid, and deionized water is used as the polishing medium. The novel tool is a magnet fixture made of mu-metal which is used to hold the magnet during finishing. In the present experimental study, finishing at a spot on flat titanium alloy is carried out to analyze the forces involved in the finishing. Normal force is the main force responsible for the indentation by the abrasive particle on the workpiece surface. Tangential force helps in removing indented material. The measured normal force and tangential force during the spot finishing are 3.285 N and 0.43 N, respectively. The final surface roughness achieved after spot finishing is 10 nm from initial surface roughness of 200 nm. The percentage improvement in surface roughness is 95%.

Commentary by Dr. Valentin Fuster
2018;():V004T03A051. doi:10.1115/MSEC2018-6362.

Carbon fiber reinforced plastic (CFRP) composites have many excellent properties, which make them be widely used in many applications. After demolding processes, CFRP composites still need additional machining processes to achieve final shape with desired tolerances. Edge trimming is the first machining process performed on composites after their molding processes. Because of carbon fibers’ abrasive properties as well as CFRPs’ properties of inhomogeneity and anisotropy, CFRPs are regarded as the difficult-to-cut materials. Many problems are generated in traditional machining processes. To reduce and solve the problems, edge trimming using rotary ultrasonic machining (RUM) is reported in this manuscript. This paper, for the first time, makes the comparisons on machining performance (cutting forces, torque, and surface roughness) between edge trimming processes with and without ultrasonic vibration assistance. To better understand effects of ultrasonic vibration on such a process, machining mechanisms are also obtained and analyzed. This paper will provide guides for RUM edge trimming of CFRP composites.

Commentary by Dr. Valentin Fuster
2018;():V004T03A052. doi:10.1115/MSEC2018-6382.

Low frequency vibration assisted drilling (LFVAD) is regarded as one of the most promising process in CFRP/Ti stacks drilling. This work carries the investigation of the difference between conventional drilling and LFVAD based on kinematic model. The experiments are conducted under varied vibration amplitude to a specific feed rate, also under varying spindle speeds, feed rates when the ratio of amplitude to feed rate is fixed. Then the hole quality of CFRP is evaluated based on the analysis of drilling force, chip morphology, chip extraction. The results show that there is rarely no difference between conventional drilling and LFVAD in drilling mechanism when the drilling diameter is over 1 mm. Because the impact effect caused by drill vibration is already weak. It is found that the severe mechanical damage of the CFRP holes surface could be significantly reduced due to the fragmented chips obtained in vibration drilling. The maximum instantaneous feed rate combined with feed rate and amplitude plays a significant role in CFRP hole quality. Lower maximum instantaneous feed rate results in better hole wall quality and less entry delamination. Spindle speed has no visible influence on entry delamination, while higher spindle speed improves the hole surface quality due to the resin coating phenomenon.

Commentary by Dr. Valentin Fuster
2018;():V004T03A053. doi:10.1115/MSEC2018-6442.

We describe a method for the manufacturing of metallic lattices with tunable properties through the reversible assembly of building block elements, which we call discrete metal lattice assembly (DMLA). These structures can have sub-millimeter scale features on millimeter scale parts used to assemble structures spanning tens of centimeters, comparable to those currently made with Direct Metal Laser Sintering (DMLS). However, unlike traditional additive manufacturing (AM) methods, the use of discrete assembly affords a number of benefits, such as extensible, incremental construction and being repairable and reconfigurable. We show this method results in large scale (tens of centimeters), ultralight (<10 kg/m3 effective density) lattices which are currently not possible with state of the art additive manufacturing techniques. The lattice geometry used here is a combination of two geometries with quadratic property scaling, resulting in a novel lattice with sub-quadratic scaling.

Topics: Manufacturing
Commentary by Dr. Valentin Fuster
2018;():V004T03A054. doi:10.1115/MSEC2018-6457.

Laser surface hardening of most of the industrial components require depth of surface modification in the range of 100–150 micron. Conventional laser surface hardening uses laser as a heat source to modify a particular area of the surface without melting in an inert gas environment. However, the hardened profile in this case shows peak hardness value at a certain depth from the top surface. Also, hardening the top surface to get relatively much higher hardness near the top surface in case of thin sheets becomes difficult due to accumulation of heat below the surface of the specimen which in turn lowers the cooling rate. Hence, self-quenching becomes inadequate. In the present study, an in-house fabricated laser processing head with coaxial water nozzle has been used to flow a laminar water-jet during the laser surface hardening process to induce forced convection at the top surface. Thus, heat gets carried away by the water-jet from the top surface and by the water from the bottom surface as well. Results show that with judicious selection of process parameters, it is possible to get higher hardness (800 HV) to that of conventional laser surface hardening (500 HV) at the top surface using this process. Present process can be used for those cases where high hardness values are required near the top surface specially for thin sheets and thermally sensitive materials.

Commentary by Dr. Valentin Fuster
2018;():V004T03A055. doi:10.1115/MSEC2018-6515.

Friction stir back extrusion has recently been identified as a method for manufacturing stronger, more ductile seamless tubes. The long term goal of the project described here is to miniaturize the process in order to produce highly ductile microscale tubes for biomedical, microscale heat exchanger, and fuel cell manufacturing applications. The process is similar to friction stir welding and processing in that the end of a non-cutting tool rotates against a metal workpiece, heats the workpiece, and creates an ultrafine grain structure. Conventional microtube manufacturing is done by hot direct extrusion using dies with mandrels. After the workpiece passes the mandrels, the tube segments weld together from residual heat. The work described here considers macroscale tooling design prior to down scaling to the multi and microscale. The immediate objective was to develop tooling that can produce 50mm long tubes with 12.5mm outside diameters and 6.35mm inside diameters. Design considerations such as strength, fatigue, buckling, and vibration were considered. This paper documents the development of the tooling design process that was used in order to overcome the various design issues. Tooling failure and analysis is presented as part of the evolution of the tooling design. While majority of the paper discusses the tooling design process, a final design was developed and preliminary results for friction stir back extrusion tests are presented for tubes that are 25 and 50mm long.

Commentary by Dr. Valentin Fuster
2018;():V004T03A056. doi:10.1115/MSEC2018-6537.

In this experimental work, the effects of line energy at constant scan speed on quality of bead-on-plate laser welding of NiTinol sheets were investigated. Variations of bead geometry, changes in microstructure, variation of micro-hardness value along the weld-bead, generation of new phase during welding, changes in tensile strength of the welded samples, corrosion behavior of welded and parent material, and changes in phase transformation temperatures were measured for characterization of welded samples. Laser weld-bead profile was changed from a wine glass without base to glass shape with the increasing line energy. Quality aspects of weld-bead geometry quality aspects showed an increasing trend with line energy. Microstructure was changed during welding due to competitive grain growth. Microhardness values gradually increased from weld centre line to base metal. Tensile strength of the material was reduced after welding due to the formation of brittle intermetallics compounds. A dual failure mode for the welded sample was observed; whereas a single mode of failure was detected for parent material. The corrosion properties of the welded samples were found to be better than that of parent material. Phase transformation temperatures were also found to be reduced after welding.

Commentary by Dr. Valentin Fuster
2018;():V004T03A057. doi:10.1115/MSEC2018-6540.

Ti-6Al-4V (grade 5 titanium alloy) is one of the most widely used materials in aerospace applications including turbine blades for aerospace engines. Due to the difficulty of machining titanium alloys using conventional machining processes, wire-electro-discharge machining (wire-EDM) is used extensively for cutting titanium parts with complex geometries and profiles. The objective of this study is to investigate the effect of two important non-electrical parameters in wire-EDM, i.e. wire feed rate and wire tension, on the geometric corner and profile accuracies of the Ti-6Al-4V parts machined by wire EDM. A complex profile was designed for machining in two different thicknesses of titanium alloy using each set of experimental parameters. The complex part includes corners with 45°, 90° and 112.5°, as well as thin wall section for measuring the kerf accuracy. It was found that with the increase of wire tension, the corner accuracies at almost all the angles improved. however, too high wire tension caused inaccuracies by providing larger angles than the target values. The effect of wire tension was dependent on the thickness of the machined part. For thinner workpiece the results of the angles generated barely followed a trend, whereas for thicker part, the measured angles followed an excellent trend. The kerf accuracies were found to improve with the increase of wire tension for thin part, whereas for thick part the results of kerf width accuracies were inconsistent. In case of wire feed rate, it was found that comparatively lower settings of wire feed rates were favorable for machining thinner parts with enhanced corner accuracies. On the other hand, slightly higher wire feed rates provided better corner accuracies for thick part. Besides corner inaccuracy, profile undercuts and deviations from the machining paths were observed for lower wire tensions. Finally, it can be concluded that comparatively lower wire feed rate and higher wire tension provides improved corner and profile accuracies. however, for machining thinner sections using wire-EDM, the trends are not obvious.

Commentary by Dr. Valentin Fuster
2018;():V004T03A058. doi:10.1115/MSEC2018-6585.

During the process of micro machining, the existence of tool runout not only aggravates the wear and breakage of the cutter, but also seriously affects the surface quality of the parts. In order to observe the runout of micro-milling cutter, a detection method based on machine vision was proposed in this paper, which can calculate the tool runout by measuring the maximum value of external fluctuation of the cutter assembly near the tool tip. The proposed method can realize the direct measurement of radial runout of a micro-milling cutter. A dedicated prototype measuring system was established, which includes an on-machine measurement unit, a controller and the software. To obtain the images of maximum profile of the cutter at different angles, the cutter should be perpendicular with the optical axis of camera lens in the on-machine measurement unit. The experiments verified that the proposed method is feasible and the developed measurement system can fulfill the needs of industrial applications.

Commentary by Dr. Valentin Fuster
2018;():V004T03A059. doi:10.1115/MSEC2018-6591.

The present study provides detailed investigation on the effect of various laser processing parameters and scan strategy during laser forming of thin open-celled aluminium foam. Previous research on laser bending showed that metal foams can be formed by laser processing, but it is very difficult to form the metal foams mechanically owing to their brittle nature. The 2D Laser forming operation was carried out using 2 kW fiber laser with laser power and scanning speed as input process parameters while bending angle was calculated as an output parameter. The effect of laser power, scan speed, number of scans and scan distance from the edge on bending angle of the foam were analyzed and presented. It was observed that the laser processing showed a decrease in bending angle with an increase in scan speed except for 1750 W power, where after 12500 mm/min the bending angle did not follow the trend. The bending angle decreased with increase in number of scans probably due to strain hardening effect. The effect of scan distance from the edge was different for lower process parameter combinations {600 W, 2500 mm/min} and {1000 W, 4000 mm/min}, where the bending angle was maximum for a distance of 20 mm from edge in 1400 W, 7500 mm/min scan speed. For 1750W, 11000 mm/min bending angle was maximum for 80 mm distance from edge. The SEM analysis showed that the major concern associated with laser forming of open-celled Aluminium foam is foam melting. EDS and XRD analysis showed that formation of different oxides and compounds of Aluminium increases with increases in laser power and scan speed. Micro-Computed Tomography (micro-CT) analysis confirmed the absence of crack during laser forming and the pore density variation during laser forming was clearly visible between laser processed zone and the parent material zone.

Topics: Aluminum , Lasers
Commentary by Dr. Valentin Fuster
2018;():V004T03A060. doi:10.1115/MSEC2018-6631.

Drilling is the most common machining practice conducted on carbon fiber reinforced plastics (CFRP), which is challenging to conventional machining processes, such as twist drilling. Rotary ultrasonic machining (RUM) is a non-traditional machining process that has been successfully used to drill CFRP, many other brittle (e.g. silicon, ceramics), and ductile (e.g. titanium alloy (Ti-6Al-4V), stainless steel) materials. RUM is superior to twist drilling on CFRP hole-making in many aspects: lower cutting force and torque, better surface finish, less potential for delamination, and better tool life. Since RUM is a hybrid process of abrasive grinding and ultrasonic machining, it is important to study the effects of abrasive properties on output variables. This paper for the first time investigates the effects of abrasive properties (abrasive size and abrasive concentration) on output variables (cutting force, torque, and surface roughness) in RUM of CFRP. It is found that cutting force increased as abrasive size increased and as abrasive concentration increased; however, abrasive properties did not have significant effects on surface roughness of the machined holes.

Commentary by Dr. Valentin Fuster
2018;():V004T03A061. doi:10.1115/MSEC2018-6648.

This is a study of material transfer from a consumable tool to a substrate. The major advantage of this technique is material adheres by mechanical bonding at relatively low temperature, with potential benefits of high bonding strength, low temperature and thermal effects, high tolerance to contamination, environmentally benign, and low cost of materials, tooling, and process. There is an increasing need for dissimilar material surfacing and coating applications, leading to the study of the friction surfacing process. Friction surfacing experiments were done for depositing different materials to a steel substrate. Subsequent surface roughness and material analysis was done to characterize the nature of material transfer and adhesion to the substrate. The results suggest that friction stir processing by a consumable tool is capable of producing a smooth coating with good metallurgical properties.

Topics: Friction
Commentary by Dr. Valentin Fuster
2018;():V004T03A062. doi:10.1115/MSEC2018-6663.

The zirconia toughened alumina (ZTA) parts fabricated by laser engineered net shaping (LENS) process demonstrate problems resulted from poor surface quality. To improve surface quality and to reduce related problems, rotary ultrasonic machining (RUM) process, which combines both grinding process and ultrasonic machining process, has been introduced. In this investigation, the effects of ZrO2 content and ultrasonic vibration on flatness, surface roughness, microhardness, and cutting force in feeding direction of LENS-fabricated ZTA parts have been studied. Results showed that with the ZrO2 content increasing, the flatness value increased, the surface roughness value decreased, and the microhardness value firstly increased then decreased. Compared with LENS-fabricated parts, the parts processed by RUM machine exhibited better surface quality with significantly reduced flatness value and surface roughness value. In RUM process, the introduction of ultrasonic vibration was beneficial for reducing cutting force.

Topics: Lasers , Grinding , Vibration
Commentary by Dr. Valentin Fuster
2018;():V004T03A063. doi:10.1115/MSEC2018-6668.

Digital light processing (DLP) three-dimensional (3D) printing is a type of stereolithography (SLA) process that uses a digital projector to selectively cure resin according to a mask image. Each exposure solidifies a planar component of the printed part, allowing full layers to be cured at once. The DLP approach produces better quality parts at a faster rate compared to other 3D printing methods. One of the challenges with DLP printing is the difficulty of incorporating multiple materials within the same part. As the part is cured within a liquid basin, resin switching introduces issues of cross-contamination, layer height variability, and significantly increased print times. In this paper, a novel technique for printing with multiple materials using the DLP method is introduced. The material handling challenges are addressed with the design of a material swapping mechanism, a material tower, and an active part cleaning system. The material tower is a compact design to facilitate the storage and retrieval of different materials during the printing process. A spray mechanism is used for cleaning excess resin from the part between material changes. Challenges encountered within the 3D printing research community are addressed, with a focus on improving the shortcomings of modern multi-material DLP printers.

Topics: Sprays
Commentary by Dr. Valentin Fuster
2018;():V004T03A064. doi:10.1115/MSEC2018-6699.

Laser cladding utilizes a high-powered laser to fuse and solidify the metal powders, which results in a complex change of physical and mechanical properties. Selection of parameters and creative structure design are critical for laser cladding technology. High-speed steel is cladded on the base metal 40Cr by diode laser to investigate the influence of curvature radius, scanning speed, gas flow and laser power. The micro hardness and residue stress are tested while the microstructure is analyzed. According to analysis of the process parameters in orthogonal experiment, the optimal parameters are: curvature radius 100 mm, laser power 1200W, gas flow 1000 L/h, and scanning speed 16 mm/s. Under the optimal parameters, the microstructure and grid is uniform and the grain growth is along the same direction.

Commentary by Dr. Valentin Fuster

Processes: Machining Technologies for Multi-Axis and Multi-Tasking Manufacturing Processes

2018;():V004T03A065. doi:10.1115/MSEC2018-6384.

On-machine scanning measurement of workpiece geometry has a strong advantage in its efficiency, compared to conventional discrete measurement using a touch-trigger probe. When a workpiece is rotated and tilted, position and orientation errors in workpiece setup with respect to the machine’s rotary axes can be a significant contributor to the measurement error. The machine’s geometric errors also influence the measurement error. To establish the traceability of on-machine laser scanning measurement with workpiece rotation, this paper kinematically formulates their contribution to measured profiles. As a practical application example, this paper studies the sensitivity of work-piece setup errors and rotary axis geometric errors on the error in laser scanning measurement of an axis-symmetric part.

Topics: Lasers , Machinery , Errors
Commentary by Dr. Valentin Fuster
2018;():V004T03A066. doi:10.1115/MSEC2018-6517.

S-shaped machining test is proposed for ISO standard to evaluate the motion accuracy of five-axis machining centers. However, it have not been investigated that which factor mainly influences the quality of the finished S-shape workpieces. This study focuses on the influence of the quality of NC program and geometric errors of rotary axes onto the quality of finished surface. Actual cutting tests and simulations are carried out to the investigation. As the results, it is clarified that the tolerance of NC program has a great influence onto the quality. It is also clarified that the geometric errors have great influences onto the quality. However, it is difficult to evaluate the influence of each geometric error because all geometric errors make glitches at the same point on the machined surface. It can be concluded that the proposed S-shape machining test can be used as the total demonstration of the machining techniques.

Topics: Machining , Errors , Shapes
Commentary by Dr. Valentin Fuster
2018;():V004T03A067. doi:10.1115/MSEC2018-6525.

The postprocessor is essential for machining with five-axis machine tools. This paper develops one universal postprocessor for table-tilting type of five-axis machine tools without rotational tool center point (RTCP) function. Firstly, positions of two rotary axes and the workpiece in the machine coordinate system (MCS) are introduced into the kinematic chain of the five-axis machine tools. The uniform product of exponential (POE) formula of the tool relative to the workpiece is established to obtain the universal forward kinematics. On this basis, the postprocessor of table-tilting type of five-axis machine tools is developed. The calculation of rotation angles of rotation axes is proposed in details, including the calculation of double solutions, the determination of rotation angles of C-axis and the selection principle of the shortest path of rotation angles. Movements of linear axes are calculated with rotation angles of rotary axes. The generated movements of all axes are actual positions of all axes relative to their zero positions, which can be used for machining directly. The postprocessor does not rely on RTCP function with positions of rotary axes and the workpiece in MCS. Finally, cutting test in VERICUT and real cutting experiments on SmartCNC500_DRTD five-axis machine tool are carried out to verify the effectiveness of the proposed postprocessor.

Topics: Machine tools
Commentary by Dr. Valentin Fuster
2018;():V004T03A068. doi:10.1115/MSEC2018-6557.

Motion accuracy of NC machine tools is directory copied onto the machined shape. However, it is known that the motion accuracy is deteriorated by several error courses; geometric and dynamic motion errors of feed axes. In this study, in order to enhance the motion accuracy of NC machine tools, a method that modifies the NC program based on the normal direction error at each command point on the designed path is developed. In the method, the error vector between the commanded and estimated machined shape is obtained. The NC program for the motion is modified by adding the obtained error vector with the opposite sign. In order to confirm the effectiveness of the proposed method, 5-axis motion tests for cone-frustum cutting which is widely applied to the accuracy evaluation of 5-axis machining centers are carried out. At the first, it is confirmed that the proposed method can compensate the dynamic synchronous errors based on the feedback positions and angles of the axes. In addition, it is also confirmed that the proposed method can compensate both of dynamic and geometric errors based on the tool center point trajectory measured by a ball-bar system. As the results, it is clarified that the proposed method can effectively enhance the motion accuracy of the 5-axis machining center.

Topics: Cutting
Commentary by Dr. Valentin Fuster
2018;():V004T03A069. doi:10.1115/MSEC2018-6564.

A new method, which accurately predicts cutting force in ball end milling considering cutting edge around center web, has been proposed. The new method accurately calculates the uncut chip thickness, which is required to estimate the cutting force by the instantaneous rigid force model. In the instantaneous rigid force model, the uncut chip thickness is generally calculated on the cutting edge in each minute disk element piled up along the tool axis.

However, the orientation of tool cutting edge of ball end mill is different from that of square end mill. Therefore, for the ball end mill, the uncut chip thickness cannot be calculated accurately in the minute disk element, especially around the center web. Then, this study proposes a method to calculate the uncut chip thickness along the vector connecting the center of the ball and the cutting edge. The proposed method can reduce the estimation error of the uncut chip thickness especially around the center web compared with the previous method. Our study also realizes to calculate the uncut chip thickness discretely by using voxel model and detecting the removal voxels in each minute tool rotation angle, in which the relative relationship between a cutting edge and a workpiece, which changes dynamically during tool rotation.

A cutting experiment with the ball end mill was conducted in order to validate the proposed method. The results showed that the error between the measured and predicted cutting forces can be reduced by the proposed method compared with the previous method.

Topics: Simulation , Cutting , Milling
Commentary by Dr. Valentin Fuster

Processes: Monitoring, Sensing, and Control for Smart Manufacturing

2018;():V004T03A070. doi:10.1115/MSEC2018-6453.

Basing on the laser-triangulation principle, a deep hole inner surface inspection system is developed in this research. Compared with existing inner surface measurement systems, this research takes assembly errors and refraction distortion into consideration and proposes a flexible laser plane calibration technique based on binocular vision that is easy to operate. The measurement system calibrated by proposed method performs well in the field test in which the maximum absolute error of the measured ring gauge diameter is 3μm. Experiment indicates that this system is accurate and suitable for inner surface measurement. Point cloud registration may be applied in the future to extend the system’s applicability.

Commentary by Dr. Valentin Fuster
2018;():V004T03A071. doi:10.1115/MSEC2018-6670.

Charged particles are emitted when a material undergoes plastic deformation and failure. In machining, plastic deformation and shearing of work piece material takes place continuously; hence, emission of charged particles can be expected. In this work, an in-situ sensor has been developed to capture the emitted positively (positive ion) and negatively (electron and negative ion) charged particles in real time in an orthogonal machining process at atmospheric conditions without the use of coolant. The sensor consists of a Faraday plate, mounted on the flank face of the cutting tool, to collect the emitted ions and the intensity of emissions is measured with an electrometer. Positively and negatively charged particles are measured separately by providing suitable bias voltage supply to the Faraday plate. Ion emissions are measured during machining of three different work piece materials (mild steel, copper and stainless steel) using a carbide cutting tool. The experimental results show a strong correlation between the emission intensity and variation in machining parameters and material properties. Increasing material removal rate in machining increases the intensity of charged particle emissions because of increase in volume of material undergoing shear, fracture, and deformation. It is found that emission intensity is directly proportional to the resistivity and strength of workpiece material. Charged particles emission intensity is found to be very sensitive to the machining conditions which enables the use of this sensor as an alternate method of tool condition monitoring.

Commentary by Dr. Valentin Fuster
2018;():V004T03A072. doi:10.1115/MSEC2018-6680.

Machining industry has been evolving towards implementation of automation into the process for higher productivity and efficiency. Although many studies have been conducted in the past to develop intelligent monitoring systems in various application scenarios of machining processes, most of them just focused on cutting tools without considering the influence due to the non-uniform hardness of workpiece material. This study develops a compact, reliable, and cost-effective intelligent Tool Condition Monitoring (TCM) model to detect the cutting tool wear in machining of the workpiece material with hardness variation. The generated audible sound signals during the machining process will be analyzed by state of the art artificial intelligent techniques, Support Vector Machines (SVMs) and Convolutional Neural Networks (CNNs), to predict the tool condition and the hardness variation of the workpiece. A four-level classification model is developed for the system to detect the tool wear condition based on the width of the flank wear land and hardness variation of the workpiece. The study also involves comparative analysis between two employed artificial intelligent techniques to evaluate the performance of models in predicting the tool wear level condition and workpiece hardness variation. The proposed intelligent models have shown a significant prediction accuracy in detecting the tool wear and from the audible sound into the proposed multi-classification wear class in the end-milling process of non-uniform hardened workpiece.

Commentary by Dr. Valentin Fuster

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