bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization on the Production of Variable Thickness Aluminium Tubes
Authors: Bihamta Reza , D’Amours Guillaume , Bui Quang-Hien , Rahem Ahmed , Guillot Michel , Fafard Mario
Published: April 2011

The variable thickness tube drawing is a new modification in the tube drawing methods which enables production of axially variable thickness tubes faster and easier in comparison with other similar methods like radial forging or indentation forging. The production of this type of tubes can be used in optimum design of mechanical parts which do not necessarily need constant thickness along the axis of tube and this method can strikingly reduce the overall weight of parts and mechanical assemblies like cars. In this paper, the variable thickness tube drawing were parameterized in a MATLAB code and optimized with the Ls-Opt software as an optimization engine and Ls-Dyna as a FE solver. The final objective of this optimization study is to determine the minimum thickness which can be produced in one step by this method with various tube dimensions (tube thickness and outer diameter). For verification of results, some experiments were performed in the tube drawing machine which was fabricated by this research group and acceptable correspondence was observed between numerical and experimental results.
Y-Joint THF Simulation Using Asymmetric Feeding Lengths
Authors: Fiorentino Antonio , Marzi Roberto , Ceretti Elisabetta , Giardini Claudio
Published: April 2011

Tube hydroforming (THF) is a technology that guarantees a high final part quality and low manufacturing time and costs with respect to traditional manufacturing processes. In particular it receives much interests in complex shape tubular components forming such as in the automotive industry. The process consists of a tube placed in a die and filled with a pressurized media which expands the tube till it reaches the desired geometry. The material formability is influenced by the high friction acting between the pressurized tube and the die which does not allow enough material flowing during the process. In the present work, a Y-joint hydroforming FEM model was developed on the base of previously conducted experiments to study the effects of asymmetric friction conditions in the tube feeding zones. The model was validated and then used to study the process. In particular, it was used to simulate a Y-Joint hydroforming process using a full shaped die and evaluating the improvement on the process when asymmetric feeding lengths are adopted.
An Experimental Study on Temperature in Ultrasonic Vibration-Assisted Pelleting of Cellulosic Biomass
Authors: Feng Q. , Cong W. L. , Zhang M. , Pei Z. J. , Ren C. Z.
Published: April 2011

As one of the near-to-mid-term alternatives to fossil fuels, cellulosic biofuels can cut greenhouse gas emissions while continuing to meet liquid transportation fuel needs. By processing cellulosic biomass into pellets, density and handling efficiency of cellulosic feedstocks will be improved, resulting in a reduction in transportation and handling costs in biofuel manufacturing. Temperature of biomass during the pelleting process can affect the quality of the pellet. But effects of pelleting variables on biomass temperature during ultrasonic vibration-assisted (UV-A) pelleting are still unknown. This paper reports an experimental investigation on temperature of biomass in UV-A pelleting. It studies the effects of moisture content of the biomass and pelleting variables (ultrasonic power, tool travel distance, and feedrate). The results will be helpful in understanding the effects of ultrasonic vibration on biomass temperature, compaction mechanism, and biofuel conversion.
Simulation of the Heat Treatment of an Automotive Cast Part
Authors: Lasne Patrice , Barbelet Mickael , Jaouen Olivier , Costes Frederic , Ragai Ihab , Tempelman Harry
Published: April 2011

In this paper, simulation of the casting and heat treatment processes of front spindle of a rigid dump truck are presented. The objectives are to present how the different operations can be simulated in order to predict the local phases in the different areas of the part. To reach these objectives, two software packages are used in sequenced. The first one, Thercast, is used to simulate the casting operation. The second one, Forge, is applied to the water-quenching simulation. The general formulations used are shortly presented in this paper. The aim of casting simulation is to compute the metal behavior from the liquid state at the pouring stage to the solid state during cooling into the mold. Filling and cooling phases simulations, taking into account the air gap, ensure that no internal defects like shrinkage, porosity, micro porosity or hot tearing are taking place into the part. Forge software allows the water quenching stage simulation. A model is used to deduct the IT diagram (Isothermal Transformation diagram) from the material composition. The initial grain size influences the transformation kinetics. Another main phenomenon is the efficiency of the cooling bath. The results of the simulation (phase distribution, distortion, residual stresses) strongly depend on these input conditions. Thus, the effect of input data variations on final results must be studied. The modeling approach is validated by comparisons with micrographic observations. Another solution to determine the reliability of the models is to observe the local properties in the quenched part. The prediction of the local micro hardness can be used to evaluate the accuracy of the quenching models.
Micro Pin Extrusion of Metallic Materials Assisted by Ultrasonic Vibration
Authors: Yao Zhehe , Kim Gap-Yong , Faidley LeAnn , Zou Qingze , Mei Deqing , Chen Zichen
Published: April 2011

Micro extrusion is an economically competitive process to fabricate micro metallic parts. However, fabrication of extremely small geometric features leads to challenges in tool wear due to localized high stress and friction increase at the interface. This study focuses on micro pin extrusion of aluminum with assistance of ultrasonic vibration. Experiments were conducted with and without ultrasound using magnetostrictive actuator. Load-displacement curves from the experiments showed a load reduction when ultrasonic vibration was applied. Experiments of ultrasonic micro pin extrusion with two configurations were performed. The load reduction behaviors at off-resonance and in-resonance conditions were compared. The reduction can be explained by stress superposition of ultrasonic vibration.
Practical Methods Used for Determination of Elastic Characteristics of Gypsum Materials
Authors: Pop Petru A. , Ungur Patricia A. , Lazar Liviu , Marcu Florin M.
Published: April 2011

The paper is presented a dynamic installation used for determination the elastic characteristics of gypsum materials, such as elasticity modulus-E, rigidity modulus-G, etc. This dynamic installation is composed from: mechanical device for application of axial force, cylindrical gypsum samples on which are fixed 2 strain gages, 2 bridges circuit type “Switch & Balance Unite SB-10 with digital Strain Indicator-P3500, A/D board and PC. As the samples are used two cylinders with differently gypsum compositions: gypsum of dressing and light orthopedic corsets, and from gypsum with sonic absorbent and thermal isolator properties. The acquisition and the interpretation of data with MATLAB program is realized, by used two original programs: “Daquest-2m” for acquisition data, and “Evaluation-1m” for calculation and plot diagram of shock wave time. By determination of shock propagation time passing through the gypsum sample can be calculated the wave velocity and the elasticity modulus of gypsum tested. For building materials on base of gypsum with special applications in medicine, and panels with sonic absorbent and thermal isolator properties are demand to determine the elastic characteristics to enhance the manufacturing process and usefully.
Joining Technologies for Automotive Lithium-Ion Battery Manufacturing: A Review
Authors: Lee S. Shawn , Kim Tae H. , Hu S. Jack , Cai Wayne W. , Abell Jeffrey A.
Published: April 2011

Automotive battery packs for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (PHEV) typically consist of a large number of battery cells. These cells must be assembled together with robust mechanical and electrical joints. Joining of battery cells presents several challenges such as welding of highly conductive and dissimilar materials, multiple sheets joining, and varying material thickness combinations. In addition, different cell types and pack configurations have implications for battery joining methods. This paper provides a comprehensive review of joining technologies and processes for automotive lithium-ion battery manufacturing. It details the advantages and disadvantages of the joining technologies as related to battery manufacturing, including resistance welding, laser welding, ultrasonic welding and mechanical joining, and discusses corresponding manufacturing issues. Joining processes for electrode-to-tab, tab-to-tab (tab-to-bus bar), and module-to-module assembly are discussed with respect to cell types and pack configuration.
Ultrahigh Speed Micromachining
Authors: Jahanmir Said
Published: April 2011

A new ultrahigh speed micro-spindle has been developed for micromachining that can be used at rotational speeds as high as 500,000 rpm. Since conventional ball bearings or fluid lubricated journal bearings cannot be used at speeds beyond 300,000 rpm for any extended period of time, the new spindle uses a set of journal and thrust foil bearings. The micro-spindle was integrated with a 3-axis micro-milling machine. Cutting experiments were performed on an aluminum alloy at speeds greater than 300,000 rpm using 50 and 300 micron end-mills. The increase in rotational speed to 450,000 rpm in micro-milling of aluminum alloy allowed an increase in feed rate to nearly 800 mm/min (the maximum feed rate available by the positioning stage), thus increasing the material removal rate by more than two orders of magnitude. The dimensional accuracy of several straight cuts made at different feed rates and depths of cut was measured. Theoretical models and research on machining of industrial ceramics have shown that high-speed machining allows for smaller depths of cut by each diamond grit, thus reducing the contact forces and resulting in a reduced possibility of detrimental chipping and subsurface machining damage. Therefore, micro-grinding was performed on dental ceramics to evaluate the feasibility ultrahigh speed machining. In these studies several ceramics used for preparation of dental restorations were cut with diamond tools. The propensity for generation of machining-related damage, such as surface and subsurface microcracks, were greatly reduced by machining at ultrahigh speeds and high feed rates. Micro-machining at such high speeds, and in combination with high feed rates, has never been achieved before.
Processing of Nanodiamond Loaded Poly(Lactic Acid) Co-Continuous Porous Structures
Authors: Zhang Wei , Wyatt Tom , Yao Donggang , Zhang Qingwei , Zhou Jack G.
Published: April 2011

Porous poly(lactic acid) PLA materials are highly demanded as scaffolding templates in tissue engineering applications. In this study, a protocol for creating co-continuous porous PLA structures with nanodiamond (ND) as additive was investigated. First, a ternary blend of PLA/PS/ND was prepared with different mixing ratios under different mixing conditions. Next, a post annealing stage was applied to coarsen the phase structure. Finally, the PS phase was sacrificially extracted, leaving a porous matrix. The experimental results showed that ND can be an effective compatiblizer for increasing the miscibility between PS and PLA and reducing the phase size. It was further found that the post annealing conditions significantly affect the distribution of ND particles in the blend and finally in the porous PLA structure.
Effects of Tool Design on Edge Chipping in Ultrasonic-Vibration-Assisted Grinding
Authors: Qin Na , Pei Z. J. , Cong W. L. , Guo D. M.
Published: April 2011

Edge chipping is an important quality parameter in ultrasonic-vibration-assisted grinding (UVAG) of advanced ceramics. In this paper, the effects of cutting tool design, including three different tool angles at tool end surface and wall thickness of the cutting tool (core drills), and process variables on edge-chipping are investigated using a finite element analysis (FEA) model. Experiments are also conducted to verify the FEA predicted effects of process variables on edge-chipping for the three cutting tools.
Instantaneous Phase Separation at the Contact Surface in Compression Molding of Immiscible Polymer Blend
Authors: Zhang Wei , Li Min , Deodhar Sarang , Yao Donggang , Zhou Jack G.
Published: April 2011

Immiscible polymer blends with a co-continuous phase structure (CPS) can yield synergistic material properties. In this study, a 50/50 wt% PLA/PS blend with CPS was used as a model system to explore the influence of compression molding conditions (including compression rate, compression ratio, and mold surface characteristics) on the final phase structure of the molded part. The microscopic characterization clearly demonstrated the instantaneous formation of a PLA rich layer at the mold contact surface when a high compression ratio and fast compression rate were applied during molding. CFD simulations were performed to numerically study the effects of compression on phase structure evolution in binary blends. If harnessed appropriately, this phase separation process may be utilized for creating innovative material structures.
Cryogenically Treated Round Silicon Carbide Whisker-Reinforced Alumina Inserts for Face Milling Hardened Steel
Authors: Milner Justin L. , Roth John T. , Goldsmith Jason
Published: April 2011

One of the most cost-effective dimensionally accurate processes used in manufacturing today, that is capable of producing a superior surface finish, is machining. As tooling wears, however, the advantages of machining greatly diminish. In addition, the time lost changing out the tooling significantly affects the overall process efficiency. Therefore, methods that decrease the wear rate of tooling and, thereby, increase tool longevity is essential to improving the efficiency of machining. Cryogenically treating tooling is one method that has been demonstrated to significantly increase the wear resistance of traditional tooling materials such as steel and tungsten carbide and is becoming more commonplace in industry. However, the effects of cryogenically treating advanced ceramic tooling are not well established, especially for machining hardened steels and refractory metals. In addition, round geometry inserts were studied due to the rising popularity in industry, since there are an increased number of cutting edges. To help establish these effects, in this work, commercial grade silicon carbide whisker-reinforced alumina cutting inserts, WG-300, were subjected to deep cryogenic temperatures at −170°C. Face milling was conducted on AISI O1 hardened steel of 55 HRC to evaluate the cryogenic treatment’s effects on the wear of the ceramic inserts. More specifically, tool life and surface finish were analyzed to evaluate the performance improvements of the treated tooling. This study found that the flank wear of the deep cryogenically treated ceramic inserts was less than the corresponding wear of the untreated ceramic inserts. In addition, the surface finish produced by the treated ceramic inserts was finer than that of the untreated ceramic inserts.
Transmissibility of 802.15.1 - Compliant Radio in Machining Enclosures in Industrial Environments
Authors: Sowles Richard , Suen Derek , Loker David , Roth John T.
Published: April 2011

Wireless sensors used in plant floor environments have been studied for obstruction and multipath propagation effects on signal quality. The trend towards wireless industrial data networks motivates this study, which explores the use of IEEE 802.15.1 radios in a machine shop at varying levels of operation. Previous studies have investigated the use of a wireless sensor embedded in a rotating tool holder to monitor tool life. In order to obtain information furthering the potential use of low power radio in conjunction with machining enclosures, a Bluegiga WT12 Class 2 Bluetooth 2.1 module is placed within several CNC machining enclosures at varying table positions and heights. An exterior module receives the data from the enclosed unit, and the module’s position is also varied in 3 dimensional space. Bit Error Rate and Received Signal Strength are measured, and the effects of spatial obstruction and multipath propagation are analyzed. An Agilent 8563E spectrum analyzer equipped with an Aaronia HyperLOG 7060 EMC antenna is also used to repeat the measurements at all of the points in order to provide EMI channel characterization and a redundant source of signal power data for comparison. Large-area transmissibility testing indicates that received signal strength is not dependent upon equipment operation. The enclosure tests (perimeter, height, and proximity comparison) suggest that distance, both static and transient path obstructions, multipath propagation, and line-of-sight are factors that influence bit error rate and received signal strength. Spectrum analyzer measurements in our shop show no significant emissions in the 2.4 GHz range that cause interference. At no time during this study did the bit error rate reach 0.2% of the transmitted bits and there were no failures in transmitting text between modules. Overall, the findings indicate that reliable data transmission with low power off-the-shelf Bluetooth modules is feasible.
Process Control Model for Tube Hydroforming
Authors: Kilonzo Obadiah
Published: April 2011

Ongoing research has been done to develop control methods based on the simulated loading paths input to the press machinery. This forms an open loop system where the characteristics of the Press hydraulic unit involved delivering the forming agents, i.e. the axial cylinders and valves, are neglected. This process approach leads to most experiments being done by simplifications which is time consuming and expensive, curbs the ability to have feedback control and restricts development of complex machinery response algorithms. Cylinder force control and controller design models have been researched widely such as PID and H∞ but less is known about their application to Tube Hydroforming (THF) process control which is relatively new. This paper focuses on modeling the THF process and developing a Real time PID controller to operate with a prototype model. The position of the cylinder is tracked and compared with reference provided from a database via a dynamic data exchange link showing that control could be achieved with a prototype. Position control with above approach results in efficient and concerted control merging the loading path design flexibility with machinery dynamic response.
Four Empirical Models for Pelleting of Cellulosic Biomass
Authors: Qin Na , Pei Z. J.
Published: April 2011

Cellulosic biofuels are one of the substitutes for fossil fuels. However, cellulosic biomass materials possess inherently low bulk densities, so it is difficult to efficiently transport and store large quantities of feedstocks. In order to combat the negative handling, storage and transportation aspects of bulk biomass, pelleting is often required. The mechanisms existing in pelleting process play a key role to understand the pelleting of cellulosic biomass. This paper reviews four empirical models for pelleting of cellulosic biomass. The basic pelleting mechanisms of powder and the four models used for pelleting study are provided. Then the comparisons between the four models through experiments are presented.
Digital Manufacturing of Makyoh-Magic-Mirror for Difficult-to-Machine Material to Process
Authors: Sawa Kazuya , Hirogaki Toshiki , Aoyama Eiichi , Okubo Kazuya , Ogawa Keiji
Published: April 2011

The Makyoh, or “magic mirror,” is a bronze mirror originating from ancient Japan. The mirror reflects an image on a distant wall when parallel light such as sunlight shines on it. Craftsmen with a great amount of cumulative experience and intuition have produced the Makyoh, and the skill of these craftsmen has advanced continuously. However, there are very few craftsmen today who can make Makyoh mirrors. The problem of the diminishing number of craftsmen, which is not confined to creating the Makyoh, has drawn considerable attention. There have been attempts to digitize the skills (or inferred knowledge) of these craftsmen. To maintain traditions into the future, it is important to assist producers with traditional craftsmanship who have long supported Japanese industry. Therefore, the digital manufacturing of a Makyoh using numerically controlled machining and polishing was attempted. In our first report, a new method to make the Makyoh using a machining center was demonstrated [1]–[3]. In the present report, the influence of the topography of a Makyoh surface was examined, produced by the line machining method, on the projected image. As a result, (1) with our method it was possible to make the makyoh using all three materials. (2) The difference in contrast between cutting on the outer side and on the inner side was large with a decreasing radius of curvature R in circular cutting. (3) We succeeded in processing complicated shapes by using straight lines and curved lines.
Advantages of Servo Presses in Metal Forming With a Focus on Warm Forming of Sheets
Authors: Kaya Serhat , Altan Taylan
Published: April 2011

Servo presses are recently introduced metal forming machinery and they are in many ways, a hybrid of mechanical and hydraulic presses. They are designed to combine the strengths of conventional mechanical and hydraulic presses, and at the same time to minimize their constraints. The advantages of servo presses in metal forming technology are discussed briefly. Advantages they offer in warm forming are discussed more in detail and demonstrated experimentally. By using the flexibility that the servo press offers, the effect of contact pressure on temperature change and surface roughness of aluminum and magnesium sheet is experimentally investigated. Non-isothermal warm forming is introduced and studied experimentally. Combined advantages of the non-isothermal approach and the servo motor controlled press are demonstrated by introducing a variable forming speed concept. As a result, 60% savings in cup drawing time is achieved experimentally. Measured temperature curves were used in FEA to determine heat transfer coefficients. Effect of the determined heat transfer coefficients on deep drawing was analyzed using FEA and good agreement were obtained between FEA predictions and experimental measurements.
Development of a Small 5-Axis Micro-Milling Center for Parts Up to 100 mm in Diameter
Authors: Honegger A. , Tulsian A. , Creighton E. , Phillip A. , Mukhopadhyay D.
Published: April 2011

In this paper, the development of a small 5-axis machine tool (the Microlution 5100-S) for production-level micro-machining applications is presented. This machine is based on the concept that small parts should be manufactured on specially designed small machines, a.k.a. micro-machine tools (mMTs). The performance goals for this development effort were established as follows: ±1 micron linear positioning accuracy, capability to perform simultaneous 5-axis machining on parts up to 100 mm in diameter, maximum acceleration of 2g and a high-speed spindle with a maximum speed between 50,000 and 70,000 RPM. Additionally, this development is directed at addressing the needs of high-volume micro-machining applications. Hence, the machine required the development of a reliable, high-capacity tool-changer and compatibility with many productivity enhancing equipments viz. palette transfer robots and chip conveyors. Lastly the advantages of using this machine for miniature part production are presented with respect to savings in energy, increase in productivity and lowering of floor-space requirements.
Utilizing Recurrence Quantification Analysis for Chatter Detection in Turning
Authors: Rajesh Vazhayil Govindan , Narayanan Namboothiri V. N.
Published: April 2011

Recurrence quantification analysis (RQA) quantifies the number and duration of recurrences of the nonlinear dynamical system presented by its phase space trajectory. The present work analyzes the dynamics of the cutting process in a lathe by studying the recurrent behavior of the system using RQA. It reports the capability of this analysis to detect the transition from chatter free cutting to chatter cutting which occurs due to instability of the cutting process, during the turning operation. The study reveals that the RQA variable, percent determinism is sensitive to this transition. It is found that the value of this variable increases when chatter occurs.
The Application of Horizontal Rotational Forming Process in Fabrication of Thermoplastic Sliding Bearings
Authors: Pop Petru A. , Lopez Martinez Juan , Bejinaru-Mihoc Gheorghe , Gordan Mircea
Published: April 2011

The paper is presented an application of horizontal rotational-forming in fabrication of thermoplastic sliding bearings for machine tools. In addition, general aspects regarding the flow process of thermoplastics by used rotational-forming of revolution parts are described. The heat of plastic material at melt-temperature point is realized by High Frequency Current Induction (HFCI) on a centrifugal molding installation of bimetallic bushes. From the experiment tests has observed that between melt-temperature point of thermoplastic material, revolution speed and size molding a synchronism is required, which depends of material density and whirl form of melting. The predictable revolution speed of metallic mold has achievement by technological attempts, in function of workpiece size and type of material. The charge weight is experimental determined in dependence of part’s thickness walls. This process leads to obtain the workpieces at high quality level and constant thickness walls. The new bearings have been made from polyamide-PA.6, which changed with success the bronze bearings used at drilling machine tools.
A Study on Ultrasonic Elliptical Vibration Cutting of Hardened Steel Using PCD Tools
Authors: Zhang Xinquan , Nath Chandra , Kumar A. Senthil , Rahman Mustafizur , Liu Kui
Published: April 2011

Ultraprecision machining of hardened steel by the conventional cutting (CC) technique using diamond tools is impossible because of highly chemical affinity between carbon and iron at higher temperature during machining. An intermittently cutting technique, namely, ultrasonic elliptical vibration cutting (UEVC) technique has been being applied for high-quality machining of various difficult-to-cut materials for the last decade. However, study on machining of hardened stainless steel using polycrystalline diamond (PCD) tools applying this cutting technique has not been reported yet. This study presents an experimental study on UEVC of hardened stainless steel (a typical Stavax of 49 HRC) using PCD tools. Face cutting experiments have been carried out to investigate the effects of conventional machining parameters: depth of cut, feed rate, and spindle rotational speed on the performance parameters such as cutting force, tool flank wear, surface roughness and chip formation. A minimum surface roughness Ra value of 10 nm, measured by a stylus profilometer, was achieved. It can be concluded that, while applying UEVC technique, the inexpensive PCD tools compared to the single crystal diamond tools can be effectively applied to obtain optical surface for producing precise dies and molds from hardened steel.
Development of Sound Based Tool Wear Monitoring System in Micro-Milling
Authors: Lee Ming-Hsing , Lu Ming-Chyuan , Tsai Jhy-Cherng
Published: April 2011

A micro tool wear monitoring system based on the audible sound signal was developed and studied in this report. Three modules featuring the signal transformation, feature selection and classification, respectively, were included in this system. A micro milling experiment was conducted on a research platform and the audible sound signals collected by the microphone during the cutting processes were obtained for system development and verification. In the system development, the audible sound was first transformed to the frequency domain and the best features for condition classification was selected based on the class scatter criteria. In classifier design, the Fisher Linear Discriminant (FLD) was used to identify the tool wear condition from the selected features. This study shows that the performance of system was affected by the bandwidth of the feature, as well as the number of features selected for classification. With carefully selecting the parameters, higher than 90% classification rate can be obtained by this system for micro tool condition monitoring.
Synchronous Polygon Turning for Implant Manufacturing
Authors: Chuang Frank S. H. , Lin Ko-Yu , Chen Yuheng
Published: April 2011

A complex machining process is proposed to generate the shank of a dynamic hip lag screw multi-faceted with both planar and cylindrical surface types. By installing a power driven tool on each of two sides of a workpiece, a synchronous polygon turning process is setup to complete the prescribed cutting in a single stroke. The tool on one side is to cut the planar faces using the conventional polygon turning process. Under the constraints of the above polygon turning, the tool on the other side demands special assignments for polygon turning of cylindrical faces. Assigned with a non-integer cutter-disk/spindle speed ratio and a number of blades mounted on a cutter disk, enormous number of line segments can be generated to approximate circular cuttings. The use of non-integer speed ratio enables the generation of enormous number of sides with relatively low speed ratio and few number of blades. This research also simulates the motion paths of blade tips and calculates the error between the approximate curve and true circular arc under the arbitrarily assigned parameters of blade numbers and speed ratios. For implementation, bars of titanium alloy Ti-6Al-4V and stainless steel 316L were used to generate orthopedic implants, dynamic hip lag screws, on a Swiss lathe. This synchronous polygon turning has shown the efficacy and efficiency on the cutting of screw shanks.
Tribological Aspects in Electrically-Assisted Forming
Authors: Bunget Cristina , Salandro Wesley A. , Mears Laine
Published: April 2011

The constantly increasing economical and ecological concerns in the automotive and aerospace industries have resulted in high demand for improved fuel economy and greater vehicle performance. Lightweight construction is critical for reducing inertial and rolling resistance losses to increase the product performance while maintaining safety and functional requirements. This will open a wide variety of opportunities to implement materials with high strength-to-weight ratios, such as aluminum, magnesium, stainless steel and titanium alloys. However, when using conventional forming processes, these light materials bring about processing challenges: low formability, high yield strength and low strain hardening coefficients. Electrically-Assisted Forming (EAF) is a method of overcoming these limitations. Specifically, EAF is a novel forming process where electricity, AC or DC, is applied to the metallic workpiece through the dies during deformation. Previous experimental investigations have shown that EAF can lead to reductions in flow stress and power consumption, increase in formability through larger achievable strains, the ability to reduce/eliminate springback, and improved precision. This study investigates the influence of electricity on the different lubrication mechanisms by evaluating lubricant performance in an EAF process and identifying potential lubricant candidates for EAF. The tribological conditions have a significant influence on the frictional forces occurring at the die/workpiece interface, thus on the forming load, part quality, and achievable form. When electricity is applied, besides the changes due to surface expansion at the interface occurring in conventional processes, the lubricant is exposed to high localized temperatures and current fields. To analyze this, electrically-assisted ring compression tests are conducted and the performance characteristics of several lubricants are studied. By combining the experiments and finite element simulation results, friction coefficients can be estimated, and the effect of electric current flow on friction characteristics quantified. One goal of this study is to identify possible lubricant candidates to be used in EAF processes.
Addressing Uncertainty in the Environmental Analysis of Nickel Nanoparticle Production
Authors: Brown Malcolm O. , Haapala Karl R. , Paul Brian K. , Glover Richard D. , Hutchison James E.
Published: April 2011

In spite of the many potential benefits and applications of nanoparticles, concerns have been raised regarding their production, use, and ultimate fate due to poor process yields and uncertain health and environmental impacts. Production of commercial nanoparticles is growing as they find increasing use in industrial and consumer products. Nickel nanoparticles (NiNPs) have shown promise as a single element braze material, but the energy and material efficiencies of NiNP production remain uncertain. In this study, life cycle assessment (LCA) is employed to compare three different NiNP synthesis methods in terms of environmental impact. The study reveals challenges in using LCA to assess nanomanufacturing processes. Sensitivity analysis is performed across several process parameters to demonstrate an approach for addressing data uncertainties. The relative performance of the NiNP synthesis processes are discussed, and potential environmental implications for other NiNP synthesis processes are introduced. Policy change may be necessary to provide adequate transparency in assessing nanotechnologies for engineering applications.
Multi Functional Behavioural Analysis of Al-SiC Metal Matrix Composite Foam Produced by (TiH2-CaCO3) Dual Foaming Agent
Authors: Ghose Joyjeet , Sharma Vinay , Kumar Surender
Published: April 2011

Aluminium alloy composite foams reinforced by 5% vol. SiC particles were fabricated with melt foaming route using TiH2-CaCO3 dual foaming agent. The compressive modulus and strength of two different relative density aluminium foams were investigated experimentally. An empirical relationship was established between normalized change in density and strain, using experimental data of compression tests up to different strain levels. Sound absorption property of the developed material was found out by impedance tube method. Acoustic test results indicate the potential of the material as sound absorber.
Simulation of Diamond Disc Conditioning in Chemical Mechanical Polishing: Effects of Conditioning Parameters on Pad Surface Shape
Authors: Baisie Emmanuel A. , Li Z. C. , Zhang X. H.
Published: April 2011

Diamond disc conditioning is traditionally employed to restore pad planarity and surface roughness in chemical mechanical polishing (CMP). In this paper, a mathematic model is developed by using a surface element method to simulate and predict the pad surface shape resulted from diamond disc conditioning. The developed model is then validated by published experimental data. Three metrics (total thickness variation (TTV), bow and non-uniformity (NU)) are defined and utilized to evaluate the pad surface shape. Based upon the validated model, effects of conditioning parameters (including sweeping profile, pad rotating speed, conditioner rotating speed, and conditioner diameter) on the pad surface shape are further investigated and discussed.
Femtosecond Laser-Induced Surface Texturing and Crystallization of a-Si:H Thin Film
Authors: Wang Hongliang , Kongsuwan Panjawat , Satoh Gen , Yao Y. Lawrence
Published: April 2011

Hydrogenated amorphous silicon (a-Si:H) thin films have been considered for use in solar cell applications because of their significantly reduced cost, however, the overall efficiency and stability are less than that of their bulk crystalline counterparts. Limited work has been performed on solving the efficiency and stability issues of a-Si:H simultaneously. In this study, both surface texturing and crystallization on a-Si:H thin film are achieved through one-step femtosecond laser processing in water. Light absorption is enhanced by light trapping based on surface geometry changes, and the formation of a mixture of hydrogenated microcrystalline silicon (μc-Si:H) and a-Si:H after crystallization suggests that the overall stability may be increased. Furthermore, the formation mechanism for the surface spikes is discussed. A comparison of absorptance spectra for various surface morphologies and crystallinities shows that the combination of surface texturing and crystallization induced by femtosecond laser processing is very promising for a-Si:H thin film solar cell applications.
On-Line Monitoring of End Milling Forces Using a Thin Film Based Wireless Sensor Module
Authors: Ma Lei , Melkote Shreyes N. , Morehouse John B. , Castle James B. , Fonda James W.
Published: April 2011

A sensor module that integrates a thin film PVDF piezoelectric strain sensor and a wireless data processing/transmitting platform has been designed and implemented for wireless monitoring of the feed force in the slot end milling process. The module, which is mounted on the tool shank, measures the dynamic strain produced in the tool and transmits data wirelessly to the receiver connected to a data acquisition computer. A first principles model based on the Euler-Bernoulli beam theory and constitutive equations of the piezoelectric sensor material is used to transform the wirelessly obtained data into the feed force acting on the tool in a slot milling operation. The wireless PVDF sensor signal is found to compare well with the expected (or theoretical) sensor signal computed from the measured feed force in slot milling experiments.
The Effects of Emissivity and Camera Point Spread Function on the Temperature Measurement of Segmented Chip Formation Using Infrared Thermography
Authors: Heigel Jarred C. , Whitenton Eric P.
Published: April 2011

This paper uses simulation to investigate measurement errors resulting from the camera point spread function (PSF) when measuring the temperature of segmented chip formation using infrared (IR) thermography. The PSF of the IR camera effectively filters the results which can cause significant errors due to the large temperature gradients and abrupt transitions between features and their corresponding emissivity values. The different emissivity values of the tool, workpiece, chip body, and shear band affect the apparent difference in the emitted energy of these different features. This decreases the measured temperature in the regions of most interest: along the tool-chip interface and the periodic shear zone. The method in this study creates an appropriate emissivity map from post-process measurements and applies it to results from the temperature distribution of the cutting zone predicted by commercial finite element analysis (FEA) software. Comparisons between the simulation results and experiment results show that the emissivity values obtained form the post process chip analysis lead to good agreement. The resulting radiant intensity distribution becomes the input for an IR camera simulation module developed by the authors and presented in earlier work [1]. The earlier work used the true temperature distribution predicted by the FEA as the simulation module input, and did not incorporate the IR camera’s PSF. Implementation of the actual IR camera’s PSF allows the simulation module to more accurately represent the measurements of the IR camera and ultimately allow the comparison of the simulation results to the measurement results. Simulation results show that the PSF accounts for 45% of the 42 °C radiance temperature error at the tool-chip contact along the rake face. The PSF accounts for approximately 15% of the 46 °C radiance temperature measurement error at a point in the center of the catastrophic shear band. These errors consider the effects of motion blur (integration time) and magnification (size-of-source), as described in the earlier work [1].
Effect of Severe Prior Deformation on Electrical-Assisted Compression of Copper Specimens
Authors: Siopis Michael S. , Kinsey Brad L. , Kota Nithyanand , Ozdoganlar O. Burak
Published: April 2011

In Electrical-Assisted Forming (EAF), current is passed through the material during the deformation process, which results in a decrease in the required flow stress for the material. While resistive heating occurs, the flow stress reductions are beyond what can be explained by temperature effects alone. Hypotheses for this effect relate to the current affecting dislocation generation and aiding dislocation motion through the lattice structure. If the latter was the case, then materials with higher dislocation densities from severe deformation should have more pronounced benefits from EAF. In this research, Equal Channel Angular Extrusion (ECAE) was used to induce severe plastic deformation into the material. Subsequent EAF compression experiments with the ECAE specimens and as-received material with comparable grain sizes were conducted. As expected, the EAF process reduced the flow stress value substantially more, e.g., 224MPa versus 115MPa at a strain of 0.8 for the ECAE specimens compared to the as-received specimens respectively. These flow stress reductions were from a case with no current applied to a case where an initial current density of 250A/mm2 was applied. EAF may particularly be beneficial at the microscale to address size effects as the current required to achieve an elevated current density is more viable.
Formability of Open-Cell Aluminum Foams by Laser
Authors: Santo Loredana , Guglielmotti Alessandro , Quadrini Fabrizio
Published: April 2011

A new forming method for open-cell aluminum (Al) foams by laser was introduced. Laser forming is generally applied to sheet metals but a good formability was observed also for Al alloy cellular structures. In this study, laser bending tests were performed on rectangular samples made of open-cell Al alloy foams by means of a diode laser. Laser scan velocity and power were changed in the experimentation so as to identify the best process conditions for three different Al foams. A finite element model was implemented to simulate the laser-material interaction during forming in dependence of the foam structure. At fixed values of laser velocity and power, higher bending angles were obtained for foams with smaller pores but, changing the process parameters, a better formability was observed for the foams with bigger pores.
Improving Biocompatibily of Laser Micromachined Silicon Wafer by Surface Coating With Poly(Ethylene Glycol) Diacrylate and Diamond-Like Carbon for Biomedical Devices
Authors: Wongwiwat Plawut , Narayan Roger J. , Lee Yuan-Shin
Published: April 2011

This paper presents a study of laser micromachining and the effect of the micromachined regions on the biocompatibility in the protein adsorption for medical devices applications. From the study, the surface roughness on the micromachined area promoted the protein adsorption so it probably causes the thrombus formation for the application in the cardiovascular or blood related devices. In contrast, this incident can enhance the cell promotion that is helpful for the biomedical implant MEMS devices. To modify the surface property in biocompatibility, both Diamond-like carbon (DLC) coating and Poly ethylene glycol diacrylate (PEGDA), the protein resistant and biocompatible materials, were proposed in this research. The UV lithography for coating PEGDA and Pulse laser deposition for coating DLC on the laser micromachined substrates were applied while the coated substrates were biocompatibility tested with the Bovine Serum Albumin (BSA) to observe the protein adsorption. To image the quantity of adsorption, the fluorescein labeled BSA was used for fluorescent microscope to clearly image the reflective light. This study proposed a good opportunity for major novel techniques such as laser micromachining, PLD and UV lithography in developing and prototyping biocompatible MEMS devices.
In Pursuit of an Integrated Methodology for Accurate Elevated Temperature and Superplastic Tensile Testing
Authors: Abu-Farha Fadi , Sabo Joshua , Herring Craig
Published: April 2011

Hydro and pneumatic sheet metal forming operations are commonly carried out at warm and elevated temperature; hence for modelling the behaviours of the formed materials, testing at such temperatures is necessary. The uniaxial tensile test is the most universally-adopted mechanical testing procedure for material characterisation purposes; yet in spite of its simplicity and standardisation for room temperature testing, the test is problematic at higher than-ambient-temperatures. Perhaps that explains the disagreements between different researchers in the field on some of the most critical aspects of the test. Crucially, any inaccuracies in warm and elevated temperature tensile testing have direct impact on the accuracy of the constitutive models and finite element simulations, which we rely on in running and optimising hydro/pneumatic forming operations. This work presents a comprehensive testing methodology that aims at resolving the most critical of issues encountered in this unique type of testing. The methodology is centred about quick-mount grips that tackle the thermal issues by facilitating mounting the test specimen in a very short time. A testing procedure is devised accordingly, and preliminary testing results are presented to demonstrate the impact of the methodology on the accuracy of the results. In addition, the effect of the specimen geometry on the test outcome is investigated using a wide variety of geometries; an optimised geometry is derived based on the obtained experimental results. The methodology is validated by testing AZ31B-H24 magnesium alloy specimens at different temperatures and strain rates.
Desktop Single Point Incremental Forming System
Authors: Chen Shuping , Wang Yang , Chen Maohua
Published: April 2011

This paper proposes a novel thin shell curved surface forming method by dieless single point forming technology embodying the thought of the parallel running for both design and manufacture. And a sheet metal superplastic forming prototype system with a heterogeneous master-slave manipulator by force-reflecting control has been developed. The system mainly consists of mechanical transmission components, servo system, online optical scaler for the measurement and the path planning of the forming tool. The final ideal forming experiment has physically testified the feasibility of the mutual forming method for the shell sample of a panda model. This paper brings up the tentative idea of real object modification with the use of heptic force-feedback.