bluuebunny/crossref_metadata_2025 huggingface dataset:
Assembly and Performance Modeling of Proton Exchange Membrane Fuel Cells
Authors: Zhou Y. , Lin G. , Shih A. J. , Hu S. J.
Published: September 2010

Proton exchange membrane (PEM) fuel cells are favored in many applications due to their simplicity and relatively high power density. However, there has been a lack of understandings of the fundamental mechanisms of assembly and manufacturing induced phenomena and their influence on performance and durability. This paper presents a comprehensive analysis of assembly pressure induced phenomena in PEM fuel cells using multi-physics based modeling. A finite-element-based structural and mass-transfer model was developed by integrating mechanical deformation, mass transfer resistance, and electrical contact resistance to study the effects of assembly pressure and the fuel cell overall performance. Contact resistance, inhomogeneous deformation of membrane and GDL, electrochemical analysis were simulated. The fuel cell performance was predicted and an optimal assembly pressure was identified through this multi-physics model. Results show that PEM fuel cell performance first increases gradually to a maximum and then decreases with further assembly pressure increase. The influence of temperature and humidity on cell performance was also investigated.
Nanoscale Molding Model for Bulk Metallic Glass Features
Authors: Mros Catherine , Rason Kavic , Kinsey Brad L.
Published: September 2010

Bulk Metallic Glass (BMG) has been molded against silicon dies to fabricate both microstructures and nanostructures. At the microscale, geometrically complex, high aspect ratio microfeatures have been developed into controlled geometries [1–4]. A demand exists to control the nanofeatures in a similar manner. In past research, a thin film model was presented to predict the pressure distribution across the BMG during the molding process when it is in the supercooled liquid state [5]. In this paper, a flow model is presented to predict the achievable nanoscale feature sizes and aspect ratios. This model contains a viscous term to account for the required force to produce flow, and a capillary pressure term to account for the required energy to overcome surface effects. Silicon molds are being produced with various trench sizes over a relatively large area in order to validate these models.
Experimental Investigation of Grain and Specimen Size Effects During Electrical-Assisted Forming
Authors: Siopis Michael S. , Kinsey Brad L.
Published: September 2010

Alternative manufacturing processes such as hot working and Electrical-Assisted Forming (EAF), which involves passing a high density electrical current through the workpiece during deformation, have been shown to increase the potential strain induced in materials and reduce required forces for deformation. While forming at elevated temperatures is common, the EAF process provides more significant improvements in formability without the undesirable affects associated with forming at elevated temperatures. This research investigates the effect of grain size and current density on annealed pure copper during the EAF process. The flow stress reduction effect of the process was shown to decrease with increasing grain sizes. A threshold current density, required to achieve a significant reduction in the flow stresses, becomes more apparent at larger grain sizes and the value increases with increasing grain size. The effects increase with increasing strain due to dislocations being generated during deformation. Therefore the dislocation density, related in part by the grain size, appears to be a factor in the EAF process.
Investigation of Critical Stress Concentration Factor in Analytical Stress Based Forming Limit Criterion
Authors: McLaughlin Kyle R. , Kasikci Tugce , Tsukrov Igor , Kinsey Brad L.
Published: September 2010

Tearing concerns in sheet metal forming have traditionally been predicted by comparing the strain state imposed on a material to its associated strain based Forming Limit Diagram. A shortcoming of this strain based failure criterion is that the Forming Limit Curves exhibit strain path dependence. Alternatively, a stress based failure criterion was introduced and shown analytically and numerically to exhibit less strain path dependence. In our past research, an analytical model was created to predict the stress based Forming Limit Curve. Inputs into the model include a material constitutive relationship, anisotropic yield criterion and a critical stress concentration factor, defined as the ratio of the effective stress in the base material to the effective stress in the necking region. This stress concentration factor is thought to be a material parameter, which characterizes a material’s ability to work harden and prevent the concentration of stress which produces the necking condition. In this paper, the critical stress concentration factors for steel and aluminum alloys were determined by comparing analytical model predictions and experimental data and found to be significantly different. A setup is then proposed to experimentally measure the critical stress concentration factors and initial results are presented.
Kinematics Simulation of Grinding Process Based on Virtual Wheel Model and Micro-Cutting Analysis
Authors: Li Xuekun , Rong Yiming Kevin
Published: September 2010

Grinding is a special machining process with large number of parameters influencing each other. Any grinding process involves six basic microscopic wheel-workpiece interaction modes in terms of grain cutting, plowing, and sliding, as well as bond-workpiece friction, chip-workpiece friction, and chipbond friction. And quantification of all the 6 modes immensely enhances understanding and managing of the grinding processes. In this paper, the kinematics simulation is presented to imitate the grinding wheel surface moving against the workpiece under specified grinding conditions. The grinding wheel surface is imported from the fabrication analysis based grinding wheel model of previous work. During each simulation iteration step, it provides the number of contacting grains, contact cross-section area for each grain, and resultant workpiece surface condition. Through retrieving the specific force value from the single grain cutting simulation, the cutting force and plowing force can be calculated. This model can also be potentially used in the time dependent behavior and thermal analysis of grinding processes.
Feasibility Study on Near-Dry Electrical Discharge Dressing of Metal Bonded Diamond Grinding Wheels
Authors: Jia Y. , Wei C. J. , Kim B. S. , Hu D. J. , Ni J.
Published: September 2010

Diamond grinding wheels are important tools to carry out precise or ultra-precise grinding of difficult-to-machine materials; however, the difficulty of dressing diamond grinding wheels is a bottleneck problem in their wide application. The objective of this study is to identify the feasibility of near-dry electrical discharge dressing (EDD) of metal bonded diamond grinding wheels. Through design of experiment (DoE), sets of tests were carried out to select proper dielectric mist composition and electrode material, to quantify the dielectric mist composition, to choose the electrode shape and rotating speed, and to investigate the influence of electric discharge parameters on dressing performance. By applying optimized experimental parameters to near-dry EDD of metal bonded diamond grinding wheels, more diamond grits protruded out of the grinding wheel surface, and the worn diamond grinding wheel got sharpened.
High-Definition Metrology Based Spatial Variation Pattern Analysis for Machining Process Monitoring and Diagnosis
Authors: Wang Hui , Suriano Saumuy , Zhou Liang , Hu S. Jack
Published: September 2010

Non-contact high-definition measurement technology, such as laser holographic interferometry, makes it feasible to quickly inspect dimensional variation at micron level, providing up to 2 million data points over a surface area of up to 300×300 mm2. Such high-definition metrology (HDM) data contain rich spatial variation information but it is challenging to utilize this information for process monitoring and control. The spatial distribution of the data is in high-dimensional form and may show nonlinear patterns. Conventional statistical process monitoring and diagnostic schemes based on simple test statistics and linear statistical process models are incapable of capturing the complex surface characteristics as reflected by large amounts of spatial data. This paper develops a framework for efficient monitoring of spatial variation in HDM data using principal curves and quality control charts. Since large scale surface variation patterns (caused by fixturing and part bending) may camouflage those in the smaller scale (generally associated with tooling conditions), it is essential to separate the patterns in these scales and monitor them individually. At each scale, process monitoring is implemented in a sequential manner by monitoring the overall spatial features followed by localized variation identification if an out-of-control condition is detected. To examine the overall spatial characteristics, a principal-component-analysis (PCA) filtered principal curve regression is proposed in conjunction with multivariate control charts whereby nonlinear patterns of spatial data are extracted and monitored. When the overall monitoring indicates a problem, the identification of a surface variation change can be achieved through localized monitoring over each surface region based on variogram pattern analysis and control charts. The location of surface region change provides clues for variation source diagnosis. The proposed method is illustrated using simulated HDM data.
Dead Time Compensation for a Novel Positioning System via Predictive Controls and Virtual Intermittent Setpoints
Authors: Wong Chan , Mears Laine , Ziegert John
Published: September 2010

Predictive control and intermittent setpoints are proposed to overcome the dead time that problem occurs in a new class of high precision position sensor for manufacturing equipment. In place of a rotary encoder or linear glass scale, a combination of a digital camera and a Liquid Crystal Display (LCD) screen is used to actively monitor two dimensional position changes on an XY table. In order to achieve precise spatial resolution, an actively-controlled planar pixel matrix is used as the tracking target for the system. A digital camera senses the location of the moving image displayed on the LCD screen and provides 2 dimensional position feedback. Thus, the timing and the quality of the visual feedback to the controller are the significant factors to determine the accuracy of the system. Due to the long image processing time, the vision feedback of the actual position of the stage is delayed. At the same time, with the slow frame capturing rates of the camera, dead time occurs between consecutive acquisitions of feedback signals from the vision system to the motion controller, which is detrimental to the performance of the system. Hence, studies and detailed analysis on different dead time compensation strategies and path planning algorithms have been performed to select the optimal strategy to address these challenges. Based on simulation results, a proposed method for integrating predictive control with virtual intermittent setpoints algorithm to mitigate dead time problem is presented in the final section of the paper.
S-Type Cultivator Tines Which Comply With ISO Standard: FEM Analysis of Stresses and Manufacturing Issues
Authors: Rakita Milan , Kakas Damir , Skoric Branko , Tomovic Mileta , Han Qingyou , Jackson Mark
Published: September 2010

ISO Standard is propagating in all aspects of industries worldwide. In order to keep competitiveness, companies are subjected to necessity for their production to be in accordance with ISO. S-type cultivator tines are used in agriculture for the soil preparation. Dimensions and the methods of testing S-tines are proposed by the standards ISO 5678-1993(E) and ISO 8947-1993(E), respectively. The fatigue test defined by ISO-8947(E) proved to be very rigorous. Stresses which develop in the S-type tine during the fatigue test were determined by the finite element method, using MSC Patran/MD Nastran software packages. Results show that tensile stresses during the test are as high as 1100 MPa (around 160 ksi). It is very strict requirement to have the yield strength higher than that value. This requirement is possible to achieve using thermomechanical treatment, a combination of metal working and heat treatment of mainly high-strength low-alloy (HSLA) steels.
An Optimization Design Method of Helical Drill Through Numerical Modeling and Simulation
Authors: Yan Lan , Zhou Zhixiong , Lin Cheng
Published: September 2010

In order to realize the visualization design of helical drill, a helical drill numerical modeling and simulation CAD system has been developed based on drill mathematical models. Characteristics of helical drill, such as chisel edge shape, cutting lip shape, lip clearance angle distribution along the cutting lip, heel clearance angle distribution around the drill flank, et al., can be predicted through the calculation and simulation of the system. Therefore, drill geometric parameters can be modified reasonably to achieve the optimization of helical drills by analyzing the predicted characteristics of helical drill. Furthermore, according to a specific set of helical drill geometric parameters, a unique set of grinding parameters can be obtained, which can be used to realize the manufacture of helical drills.
Modeling of Degradation Processes to Obtain an Optimal Solution for Maintenance and Performance
Authors: Lee Seungchul , Li Lin , Ni Jun
Published: September 2010

This paper presents an approach to represent equipment degradation and various maintenance decision processes based on Markov processes. Non-exponential holding time distributions are approximated by inserting multiple intermediate states between the two different degradation states based on a phase-type distribution. Overall system availability then is numerically calculated by recursively solving the balance equations of the Markov process. Preliminary simulation results show that the optimal preventive maintenance intervals for two repairable components system can be achieved by means of the proposed method. By having an adequate model representing both deterioration and maintenance processes, it is also possible to obtain different optimal maintenance policies to maximize the availability or productivity for different configurations of components.
China RFID Patent Analysis
Authors: Trappey Charles V. , Wu Hsin-Ying , Taghaboni-Dutta Fataneh , Trappey Amy J. C.
Published: September 2010

China is one of the world’s largest manufacturers and consumers of Radio Frequency Identification (RFID) applications. Current estimates show that China will need over 3 billion RFID tags to satisfy demand in the year 2009. The applications for RFID patents have spread across a very diverse range of inventions and in the future it is likely that most products manufactured in China will contain an RFID tag. China’s RFID industry has grown along with the demand and researchers are making significant technological advances. In this research, patent data from the State Intellectual Property Office of the People’s Republic of China (SIPO) have been used to explore RFID technology development and its trends. Patent abstracts containing the key word and phrase ‘RFID’ and ‘Radio Frequency Identification’ were collected for analysis, content extraction, and clustering. In total, 1,389 patents from the SIPO database covering the years 1995 to 2008 were retrieved and archived for analysis. Patents provide exclusive rights and legal protection for inventors, play an important role in the development and fair diffusion of technology, and contain detailed specifications necessary to define and protect the boundaries of an invention. Through patent analysis, companies monitor the development of technology and evaluate the position of potential competitors in the market. This research applies patent content analysis to map and interpret the current trends of RFID technology development in China. A patent content clustering method is used to cluster different patent documents into homogenous groups, and then technology forecasting is applied to evaluate possible market opportunities for future inventors and investors. The results suggest that the cluster called RFID wireless communication devices has entered the saturation stage and thus provides limited opportunity for development. Four other clusters; RFID concepts and applications, RFID architecture, RFID tracking implementation, and RFID transmission apparatus, have entered the mature stage. The RFID frequency and waves cluster appears to be in early growth stage with good development potential. Since the technology related to basic RFID concepts and devices has reached a mature stage in China, the research and development seems to be targeting the improvement of the RFID frequencies and waves as a means to develop more reliable RFID systems and applications.
Partial Disassembly Sequence Optimization of End-of-Life Products for Value Recovery
Authors: Rickli Jeremy L. , Camelio Jaime A. , Zapata Giovannina
Published: September 2010

End-of-life product recovery operations require performance improvement to be viable in an industrial environment. A genetic algorithm (GA) is proposed to optimize end-of-life partial disassembly decisions based on disassembly costs, revenues, and environmental impacts. Facilitating disassembly optimization with costs, revenues, and environmental impacts is necessary to enhance sustainable manufacturing through value recovery. End-of-life products may not warrant disassembly past a unique disassembly stage due to limited recovered component market demand and minimal material recovery value. Remanufacturing is introduced into disassembly sequence optimization in the proposed GA as an alternative to recycling, reuse, and disposal. The proposed GA’s performance is first verified through optimizing partial disassembly sequences considering costs and environmental impacts independently. Extension to a multi-objective case concerning costs, revenues, and impacts is achieved by specifying a new set of multi-objective crossover probabilities from independent crossover probabilities.
A Part Error Model Considering the Machine Tool Positioning Errors and Process-Induced Errors
Authors: Liao Y. Y. , Chiang H. N. , Wang J. J. , Hsu F. C. , Wu C. F. , Melkote Shreyes N.
Published: September 2010

Parts geometrical and dimensional error for a machining process can be attributed to several factors, including tool wear, thermal deformation, the machine tool positioning error and force-induced process error. Although the latter two factors are often more significant, their effect on the parts accuracy is more elusive and difficult to predict due to their inherent statistical dispersion property. It is therefore the subject of this investigation to quantitatively relate the parts error to machine tool spatial error and process-induced errors. Through root mean square calculation, a part error model is established by combining the machine tool positioning error, work vibration and tool vibration. The part error model considers two ranges of surface error consisting of surface roughness and cutting depth error of a machined plate. Using milling process as an example, the part error is predicted and compared with measurement result. The validity of this model is verified through a series of milling experiments under various cutting conditions.
Automatic Characterization of the Material Removal Rate in Laser Manufacturing of TiAl6V4 and Inconel 718
Authors: Orazi Leonardo , Cuccolini Gabriele , Tani Giovanni
Published: September 2010

In this paper a system for the automatic determination of the material removal rate during laser milling process is presented. “Laser milling” can be defined as an engraving process with a strictly controlled penetration depth. In industrial applications, when a new material have to be machined or a change in the system set-up occur the user has to perform a time-consuming experimental campaign in order to determine the correlation between the material removal rate and the process parameters. In these cases the numerical models present some limits due to the elevated calculation time requested to simulate the laser milling of industrial features. In the proposed system, based on a regression model approach, the empirical coefficients, that provide the material removal rate, are automatically generated by a specific software according to the different materials that have to be processed. A description of the automated method and the results obtained in engraving TiAl6V4 and Inconel 718 superalloy with a fiber laser are presented. The system can be adapted to every combination of material/laser source.
Sheet Metal Hydroforming Tryout Through Numerical and Experimental Validation
Authors: Del Prete A. , Papadia G.
Published: September 2010

Though sheet hydroforming has often been considered a good opportunity for industrial applications related to niche and medium-low volume productions, this technology has not yet found a specific application context as it is for tubes hydroforming (1). Thanks to its extensive application to industrial cases, the latter has defined, through appropriate experimental validations, ‘best practice’ rules for process design (2) and for its tryout (3, 4 and 5). Though not as exploited, sheet hydroforming has many advantages that meet industrial needs very well, such as: formability improvement, good surface quality, higher dimensional accuracy, springback reduction (6). In this paper proper metal forming numerical models and experimental analysis have been developed in order to analyze the feasibility of an industrial test case process design using this non conventional technology. Two different initial blank shapes, two different blank holder load paths (that is made up of twelve sectors) and, finally, two different fluid pressure load paths have been tested. There is clearly a good correlation among numerical and experimental results and also a robust response of the designed mechanical equipment which is able to follow, with a good accuracy, the assigned process characteristics (fluid pressure, blank holder force distribution, etc.). Different process conditions have been numerically and experimentally tested, not reaching, at this stage, the feasibility or, it would be better to say, the ‘hydroformability’ of the product.
Experimental Analysis of the Effect of Cutting Conditions on the Initial Penetration in Drilling: A Comparative Study Between Conventional and Split Chisel Drills
Authors: Park Sungwoo , Abu-Mahfouz Issam , Banerjee Amit
Published: September 2010

To improve the performance and the capability of the drilling process, it is necessary to understand the mechanics of drilling. In particular, drill bit vibrations lead to undesirable effects such as chatter, hole location and roundness errors. In this study, the wandering motion during initial penetration in drilling is experimentally investigated. Four quantities, namely, mean, peak-to-peak value, skewness, and kurtosis are calculated for the time-domain orbital signals. The orbital signals were obtained using proximity probes. The drilling was performed in plates of aluminum, brass, steel, and stainless steel using conventional point and split-chisel symmetrical twist drills. The conventional and split-point drills show different wandering paths during the penetration process. In general, split-point drills produced larger size orbits with more chatter during initial penetration, but showed better centering. On the other hand, conventional drills were found to produce holes that were more offset with smaller size and smoother wandering motion around the actual centers.
Theoretical and Practical Estimations Regarding of Borderline Conditions Imposed for Qualitative Achievement of Sliding Bimetallic Bearings From Steel-Bronze
Authors: Pop Petru A. , Ungur Petru , Lopez Martinez Juan , Bejinaru-Mihoc Gheorghe
Published: September 2010

The paper has presented the reduced structure of horizontal centrifugal casting mechanism by high frequency current of bimetallic bushes from steel-bronze, with a chemical stability treatment of borderline alloy layer. This stabilizer borderline layer at interference of inner cylindrical surfaces from steel and external surfaces from bronze, has achieved by adding into filler metal of Cu-Sn a supplier non-ferrous metal added, with great specific weight and low melting point as Cu-Sn alloy, for example Sn with contents of 1% from Cu-Sn alloy. At high temperature and pressure, Sn is forming with Fe from steel mass of bimetallic bearing an inter-metallic compound FeSn2, which reactions with Cu-Sn alloy due to a stable metallic connection. The experimental tests have realized at Machine Tools ‘Infratirea’ Co from Oradea, achieved bimetallic bearings of steel-bronze, with a good physical and thermal stability and well adhesion between antifriction steel with bronze.
Nanotopography in Silicon Wafer Manufacturing: A Literature Review
Authors: Qin Na , Pei Z. J. , Guo D. M.
Published: September 2010

Nanotopograhphy on unpatterned silicon wafers is becoming a serious issue in IC fabrication, especially with the decreasing critical dimension. However, there are no review papers to summarize the literature on nanotopography in silicon wafer manufacturing. This paper reviews the literature on nanotopography in silicon wafer manufacturing. It first describes the significance and definition of nanotopography. It then presents the methods and principles of nanotopography measurement. It also discusses experimental investigations about the effects of simultaneous double side grinding process on nanotopography.
Applying BPN and EWMA SPC Chart to Cold Chain Temperature Monitoring
Authors: Chen Kai-Ying , Shaw Yi-Cheng , Chen Mu-Chen , Wu Teh-Chang
Published: September 2010

Recently, with the development of urbanization, the enhancement efficiency of contactless, real-time features and high data transmission rate in supply chain management are widely discussed. The cold chain is one part of the supply chain, and especially the temperature monitoring plays a vital role in cold chain system. In this paper, we apply EWMA control chart and artificial neural network technologies to monitor temperature data. The back-propagation neural network is used to predict temperature shifts and trend. EWMA control chart is adopted to monitor temperature variation. As there’re something wrong happened, the control center of an enterprise can do some actions immediately to prevent further disaster. Finally, we construct a system with back-propagation neural network and statistical process control chart. A simulations and demonstrations environment using LEGO® bricks is also implemented.
Smart Monitoring of Cutting Tool Based on Pre-Process Data
Authors: Atluru Sri , Pavel Radu , Huang Samuel H. , Snyder John
Published: September 2010

CNC machine tools have contributed in a very large extent, to the rise in highly ingenious manufacturing processes. The advent of automation into the CNC manufacturing procedures has ensured the tremendous improvements on the efficiency front over the past few decades. But the sine qua non of a successful industry lies in its ability to facilitate continuous technology change and development to maintain its edge in the competitive arena. The manufacturing community across the globe has realized the vast potential, integrated systems provide in terms of compatibility, interoperability, safety, repeatability, quality to withstand the rising competition and cost effective manufacturing. The call for an improved, vastly superior, ‘smart’ manufacturing system is greater than ever before. The Smart Machine Program Initiative (SMPI) at TechSolve, Cincinnati aims at establishing a supervisory control to monitor and regulate distinct process modules that will result in higher productivity and better quality. Additionally, functionality is also added into the CNC system because of enhanced data interactions between the component subsystems. As a first step in this direction, TechSolve has initiated an integration module to bring together Tool Condition Monitoring (TCM) Technologies with data from Intelligent Process Planning (IPP) as the inputs. The paper starts with the detailed overview of the SMPI project, the supervisory system and its importance. It then proceeds to explain how integration was bought about between TCM and IPP modules by using predicted power during the cut as a premise for calibration tool cuts. It also proceeds to explain how the integration added functionality in terms of monitoring tool alarms and adaptive control by using a good tool in place of a bad tool. The paper also proceeds to explain how the incorporation of the health index of tool holder can also enhance the functionality of the integration module. The paper concludes by setting down an agenda for future work and proposing the benefits of the supervisory system to the Smart Machine.
A Hybrid Modeling Technique for Partially-Known Systems Using Linear Regression and Neural Network
Authors: Joslin Andrew J. , Xu Chengying
Published: September 2010

In this paper a hybrid modeling and system identification method, combining linear least squares regression and artificial neural network techniques, is presented to model a type of dynamic systems which have an incomplete analytical model description. This approach in modeling nonlinear, partially-understood systems is particularly useful to the study of manufacturing processes, where the linear regression portion of the hybrid model is established using a known mathematical model for the process and the neural network is constructed using the residuals from the least squares regression, therefore ensuring a more precise process model for the specific machining setup, tooling selection, workpiece properties, etc. In this paper the method is mathematically proven to give regression coefficients close to those which would be found if only a regression had been performed. The modeling method is then simulated for a macro-scale hard turning process, and the result proves the effectiveness of the proposed hybrid modeling method.
Geometrical Adaptive Controller for Tool Deflection Compensation in Helical End Milling Processes
Authors: Tang Yan , Xu Chengying , Jackson Mark
Published: September 2010

Geometrical Adaptive Control (GAC) aims to maintain the stability of the geometrical quality of mechanical parts during production. GAC systems can effectively compensate for the machining error induced by cutter deflection during helical end milling processes. The existing GAC systems only deal with deflection compensation in machining of straight surfaces. Deflection in curved surface machining is more complicated, and the effect of surface curvature on deflection should be considered when designing the GAC compensation system. This paper intends to develop a GAC system for cutter deflection in end milling of curved geometries to account for deflection variation induced by workpiece curvature. In this paper, the influence of curved geometry on cutting forces is firstly analyzed; then, the deflection is calculated based on the cantilever beam model. The error space motion control methodology is utilized in GAC design for deflection compensation. Simulation studies are conducted on a two-axis milling system for circular surface, and the results validate the compensation strategy.
Algal Cell-Surface Interaction: An Overview and Preliminary Test
Authors: Yuan Wenqiao Wayne , Cui Yan , Pei Z. J.
Published: September 2010

Five methods, namely adsorption, covalent binding, encapsulation, entrapment, and cross-linking, for algae immobilization were briefly reviewed in this article. The immobilization capabilities of four solid carrier materials (polystyrene, polyurethane, polyethylene, and cross-linked polyethylene) with two algal species (Nannochloropsis oculata and Scendesmus dimorphus) were tested. After 14 days of immobilization, polystyrene foam showed the best cell attachment and was covered by algae cells not only on the outer surface but also inside the porous spaces of the carrier. The cross-linked polyethylene also showed good attachment and growth of algae cells. Between the two algae species, N. oculata showed better cell attachment than S. dimorphus on all four materials indicating that cell characteristics played an important role in cell-surface interactions. The Derjaguin & Landau and Verwey & Overbeek (DLVO) theory was applied to understand the interaction mechanism and predicted attachment trends were found qualitatively accurate in matching the experimental results.
Fabrication and Characterization of Micro Dent Arrays by Laser Shock Peening on Ti-6Al-4V Surfaces
Authors: Caslaru R. , Guo Y. B. , Sealy M. P.
Published: September 2010

Surface micro dents may act as lubricant reservoirs to reduce friction and wear in sliding and rolling contact applications. Surface patterning has become a valuable technique for fabricating micro dents. Alternative methods such as micromachining present obvious limitations in comparison with laser shock peening (LSP). In this paper, the use of LSP along with an automatic X-Y table proves to be an attractive and reliable method for producing micro dent arrays with enhanced surface integrity and free of cracks. Surface topography, residual stress, and microhardness of the fabricated micro dent arrays on polished Ti-6A1-4V have been characterized. It has shown that LSP is capable of efficiently fabricating mass micro dent arrays with controllable size. The center area of the peened dents has highest hardness. In addition, high compressive residual stress can also be created.
A New Finite Element Approach Without Chip Formation to Predict Residual Stress Profile Patterns in Metal Cutting
Authors: Anurag S. , Guo Y. B. , Liu Z. Q.
Published: September 2010

Residual stress prediction in hard turning has been recognized as one of the most important and challenging tasks. A hybrid finite element predictive model has been developed with the concept of plowed depth to predict residual stress profiles in hard turning. With the thermo-mechanical work material properties, residual stress has been predicted by simulating the dynamic turning process followed by a quasi-static stress relaxation process. The residual stress profiles were predicted for a series of plowed depths potentially encountered in machining. The predicted residual stress profiles agree with the experimental one in general. A transition of residual stress profile has been recovered at the critical plowed depth. In addition, the effects of cutting speed, friction coefficient and inelastic heat coefficient on residual stress profiles have also been studied and explained.
Fabrication and Finite Element Simulation of Sequential Laser Shock Peening of Biodegradable Mg-Ca Implants
Authors: Sealy M. P. , Guo Y. B. , Salahshoor M. , Caslaru R.
Published: September 2010

Current biocompatible metals such as steel and titanium alloys have excellent corrosive properties and superior strengths. However, their strengths are often too high and as a result have a negative effect on the body. Therefore, Magnesium (Mg) alloys with relatively low strengths are ideal biocompatible metallic materials. The problem with Mg implants is how to control corrosion rates so that the degradation of Mg implants may match with bone growth. The high compressive residual stress induced by laser shock peening (LSP) has a great potential to slow down the corrosion rate. LSP is a known surface treatment method to impart compressive residual stress in subsurface of a metal. Therefore, LSP was initiated in this study to investigate surface topography and integrity produced by peening a Mg alloy. A 3D semi-infinite simulation has also been developed to predict the topography and residual stress fields produced by sequential peening. The dynamic mechanical behavior was modeled using a user material subroutine of the internal state variable plasticity model. The temporal and spatial peening pressure was modeled using a user load subroutine. The simulated dent agrees with the measured dent topography in terms of profile and depth. Sequential peening was found to increase the tensile pile up region which is critical to tribological applications. The predicted residual stress profiles are also presented.
Experimental Study of the Effect of Cryogenic Treatment on the Performance of Electro Discharge Machining
Authors: Sundaram Murali Meenakshi , Yildiz Yakup , Rajurkar K. P.
Published: September 2010

Cryogenic treatment is a heat treatment process in which the specimen is subjected to an extremely low temperature of the order of −300° F and below, to cause beneficial changes in the material properties. The advantages of cryogenic treatment include relieved residual stresses, and better electrical properties. Electro discharge machining (EDM) is a well known nontraditional machining process in which electrical energy is converted to thermal energy to remove material by melting and evaporation from electrically conductive materials. The process performance of EDM is affected by several factors including the material properties. In this study, the effect of cryogenic treatment on the performance of EDM is investigated experimentally. Copper tool electrodes were subjected to two different treatment methods, namely cold treatment (around −150° F) and deep cryogenic treatment (around −300° F). Using these electrodes, experiments were conducted to study the effect of various process parameters. Significant improvement in material removal rate was observed for EDM with cryogenically treated tools. However, their effect on tool wear is only marginal.
Preform Design for Forging Processes Based on Geometrical Resemblance
Authors: Yang Chen , Ngaile Gracious
Published: September 2010

Preform design is critical for multi-stage forging processes to ensure the production of defects-free parts. Moreover due to the geometry and material flow complexities in forging processes, finding the optimal preform shapes could be difficult and time consuming. This paper proposes an efficient preform design methodology based on geometrical resemblance which requires a few FEA simulation iterations to obtain a good preform shape. The premise of this methodology is such that the initial and subsequent simulations are carried out by constructing a slightly larger part which geometrically resembles the desired part. Initial FEA simulation of the larger part is performed with reasonably guessed preform shape which may allow the occurrence of forming defects or flash formation. Then a series of intermediate resembling parts between the largest part and the desired part are constructed. The undeformed shape corresponding to the intermediate part could be obtained by backward tracing of material flow from the simulation results of the larger part. This undeformed shape is then taken as the preform shape of the intermediate part. The procedure is repeated until the intermediate part is geometrically close to the desired part, which leads to the preform shape. In order to verify this preform design methodology, several case studies on forging and extrusion processes have been carried out. The methodology has been proven to be computationally efficient since it requires fewer numbers of iterations.
Volumetric Flank Wear Characterization for Titanium Milling Insert Tools
Authors: Burger Uli , Kuttolamadom Matthew , Bryan April , Mears Laine , Kurfess Thomas
Published: September 2010

Machining wear models are useful for the prediction of tool life and the estimation of machining productivity. Existing wear models relate the cutting parameters of feed, speed, and depth of cut to tool wear. The tool wear is often reported as changes in flank width or crater depth. However, these one-dimensional wear measurements do not fully characterize the tool condition when tools wear by other types of wear such as notching, chipping, and adhesion. This is especially true when machining difficult-to-machine materials such as titanium. This paper proposes another approach for characterizing tool wear. It is based on taking measurements of the retained volume of the cutting tool. The new wear characterization approach is used to demonstrate the progression of volumetric wear in titanium milling.
Measurement of the Effect of Surface Topology on Friction by Tip Test
Authors: Im Yong-Taek , Jung Ki-Ho , Lee Hyun-Chul , Ajiboye Joseph S. , Kang Seong-Hoon
Published: September 2010

In the present investigation, tip test based on backward extrusion was utilized to characterize the effect of surface roughness of the billet and forming tools and type of lubricants on friction. For the test, cylindrical specimens made of aluminum alloys of 6061-O and 2024-O with four lubricants such as VG32, VG100, corn oil, and grease were used. Single punch and two die sets with different surface topologies were manufactured in order to investigate the effect of surface conditions on friction and flow behavior. The load levels and tip distances were measured for both materials and compared with each other to determine shear friction factors at the punch and counter punch interfaces separately depending on the variation of surface topologies using the finite element simulations. As a result, a linear relationship among the dimensionless load, tip distance, and shear friction factors at punch and counter punch interfaces was derived for the experimental conditions investigated. The slope change of this linear relationship from negative to positive clearly depends on the variation of the surface conditions at the billet/punch and billet/counter punch interfaces. Also, it was clearly demonstrated that the dimensionless tip distance for the frictionless case can be extrapolated from the experimental data based on the simulation results. The value for the frictionless case can be used for characterizing the relative effect due to surface topologies at punch and counter punch and lubrication qualities of lubricants under various processing conditions.
An Surplus Asset Management Model for Environmental Impact Analysis of EOL Electronic Products
Authors: Qian Xueqing , Zhang Hong-Chao , Li Bingbing
Published: September 2010

With increasing environmental regulations and waste management costs, environmentally conscious design and manufacturing (ECDM) and surplus asset recovery are becoming a more attractive approach to solve environmental problems. Any company that owns a collection of PCs, printers and other electronic accessories probably needs to manage these assets more effectively, but currently there is a lack of tools for effective management. Therefore, this paper discusses, from the viewpoint of an enterprise dealing with end-of-life electronic products, the recycling processes according to literature, and derives an integrated model on surplus asset management and environmental impact analysis. The primary objective of the model is to develop a certain tool for managing surplus asset within a corporate office and generate a decision making tool for those who are concerned with the environmental issues in the design or recycling phase. Based on this model, a prototype system is introduced in detail in this paper.
Experimental and Numerical Analysis of Double Sided Incremental Forming
Authors: Wang Yongjun , Wu Weichao , Huang Ying , Reddy N. Venkata , Cao Jian
Published: September 2010

This paper presents a new rapid prototyping process of a thin sheet metal, Double Sided Incremental Forming of a cylindrical part without a die or a clamping device around the periphery of the sheet. The effects of process parameters on part shape, such as gap between two tool heads and feed rate, are examined experimentally with a special device mounted on a general lathe and numerically with a commercial finite element software package, Abaqus. Depending on the process parameter, a truncated cone shape part can be successfully fabricated with two tool heads pressing and moving along the radial direction of the sheet, which is held by lathe spindle at its center. A simple mathematic model to predict the cone angle is proposed and compared well with experimental data.
Effect of Microstructural Parameters on the Machinability of Aligned Carbon Nanotube Composites
Authors: Samuel Johnson , Kapoor Shiv G. , DeVor Richard E. , Hsia K. Jimmy
Published: September 2010

The objective of this paper is to understand through parametric studies the effect of microstructural parameters, viz., carbon nanotube (CNT) orientation with respect to the cutting direction, CNT loading and level of dispersion within the matrix, on the machinability of aligned CNT composites. To this end, a microstructure-based finite element machining model is used to simulate microstructures containing 1.5% and 6% by weight of CNTs. Microstructures with both uniform and non-uniform dispersion of CNTs are simulated. For each of these cases, CNTs having orientations of 0°, 45°, 90° and 135° to the cutting direction are studied. The machining simulations were conducted using a positive rake tool. Chip morphology, cutting forces, surface roughness, and surface/sub-surface damage are the machinability measures used for comparison. The results of the parametric studies demonstrate that the CNT orientation, loading and level of dispersion all play a critical role in dictating the machining response of aligned composites. The results further indicate that the surface morphology of the machined surface can be harnessed to produce the next generation of micro-fluidic devices.
Strain Control in an Intelligent Die Based Upon Local Force Control and Blank Holder Forces
Authors: Emblom William J. , Weinmann Klaus J. , Beard John E.
Published: September 2010

An experimental evaluation of the strains in an oval stamp forming die is presented. The die design included a flexible blank holder and active draw beads. The die was instrumented with local punch force and wrinkle sensors and control systems were developed in order to follow local punch force and wrinkle trajectories. Strains were measured after pan forming for both open and closed-loop tests. The relation between blank holder force, draw bead penetration, and strains were explored in the critical strain region of the formed pan. Closed-loop control of the local punch forces at the die ends was established using blank holder forces. The strains for tests with various lubrication conditions and draw bead penetrations were compared. It was observed that there is a tendency for the strains in critical locations to converge or remain constant for the closed-loop control tests while the strains tended to increase with blank holder force for open-loop tests. It was concluded that by controlling local punch forces, strain is indirectly controlled.
Optimizing the Manufacturing of Laminated Dies
Authors: Ahari Hossein , Khajepour Amir , Bedi Sanjeev
Published: September 2010

Laminated tooling where parts are manufactured layer by layer is a promising technology. It can help to reduce production costs and make complex tools with conformed cooling channels. Laminated tooling is based on taking sheets of metal and laser cutting profiles on them before stacking them to produce the final product. If the sheets are thin, the surface quality of final product will be good; however the cost of laser cut is increased in this case. Therefore, finding the optimum set of layers thicknesses to have the minimum surface jaggedness and the number of slices at the same is the aim of this research. A modified version of Genetic Algorithm is used for optimization purpose.