bluuebunny/crossref_metadata_2025 huggingface dataset:
Wireless Acquisition of Temperature Data From PCBN Embedded Thin Film Sensors
Authors: Guha Anshuman , Werschmoeller Dirk , Li Xiaochun
Published: April 2011

This paper presents the results of wireless data transmission experiments from micro thin film thermocouples (sensor) embedded into polycrystalline cubic boron nitride (PCBN) cutting inserts. A small wireless data acquisition system (DAQ) is necessary for sufficiently fast acquisition of experimental data from the embedded micro sensors in PCBN inserts, when mounted on a rotating cutting tool. For a wireless transfer of a low amplitude and high frequency thermal e analog signal, a signal conditioning circuit and wireless transmitting module are used. A Bluetooth transmitter module is used to establish communication with the receiver PC over serial port profile (SPP). To characterize the wireless data transfer system, heat signals are generated in stationary PCBN embedded thermocouples through laser pulses and CNC machining tests. During comparative tests, data was simultaneously acquired with a conventional wired DAQ board and the developed wireless DAQ system. The wireless DAQ capabilities and the overall dimensions of the devised wireless module greatly simplify its integration into various manufacturing applications.
Towards Data-Driven Sustainable Machining: Combining MTConnect Production Data and Discrete Event Simulation
Authors: Bengtsson N. , Michaloski J. , Proctor F. , Shao G. , Venkatesh S.
Published: April 2011

Recently there has been an increased focus on the environmental aspects of the manufacturing industry across the world. Boeing and NIST have studied the incorporation of Life Cycle Assessments (LCA) parameters into Discrete Event Simulation (DES) as a means to analyze sustainable performance in the manufacturing area. Accurate analysis of manufacturing processes using Discrete Event Simulation requires detailed CNC production data. Using MTConnect, production LCA data from Boeing shop floor machine tools was acquired and was used to develop Discrete Event Simulation models. We will discuss our implementation, and analyze results of incorporating shop floor LCA data directly in DES models.
Effects of Ultrasonic Treatments on Cellulose in Cellulosic Biofuel Manufacturing: A Literature Review
Authors: Zhang P. F. , Pei Z. J.
Published: April 2011

Cellulosic biofuels are one type of renewable energy, and have been proposed to replace traditional liquid transportation fuels. Cellulosic biomass is the feedstocks in cellulosic biofuel manufacturing. Cellulose accounts for approximately 30% of the total weight in cellulosic biomass. Glucose, one type of monosaccharide convertible to ethanol, can be obtained by hydrolyzing the polymeric structure of cellulose. Currently enzymatic methods are the most common for the hydrolysis of cellulose. However, the low efficiency of enzymatic hydrolysis increases production cost and hinders the large-scale manufacturing of cellulosic biofuels. Ultrasonic treatments applied on cellulosic biomass were found to improve the efficiency of hydrolysis and subsequently increase the sugar yield of hydrolysis. To understand the effects of ultrasonics on cellulose, investigations have been conducted on the effects on cellulose characteristics caused by ultrasonic treatments during hydrolysis. This paper reviews the effects of ultrasonic treatments on cellulose during hydrolysis in terms of sugar yield and some characteristics of cellulose, such as accessibility, crystallinity, degree of polymerization, and morphological structure.
Experimental and Numerical Analysis of Titanium Microtube Elliptical Flaring
Authors: Wu Weichao , Huang Ying , Malhotra Rajiv , Wang Yongjun , Cao Jian
Published: April 2011

Traditional tube flaring processes focuses on expanding one end of the tube without changing its cross-sectional shape. This paper presents a new two-step tube flaring process for expanding one end of a titanium alloy microtube while simultaneously changing its cross-sectional shape from circular to elliptical. Experiments were performed to investigate and verify this process. Furthermore, an analytical model was developed to analyze the forming process and investigate the relationship between punch feed and maximum plastic strain during the flaring process. The analysis shows that the two-step flaring process used is effective in expanding the circular cross section to an elliptical cross section without failure. It is also shown that the developed analytical model can predict the fracture of the tube end during the flaring process approximately. Finally, a FEM simulation was performed to further investigate the two-step flaring process.
Sensitivity of Steady State Intermittent Cutting Motion to Work-Piece Characteristics
Authors: Gegg Brandon C. , Suh Steve S.
Published: April 2011

The tool and work-piece interactions will be modeled via discontinuous systems to study the effects of work-piece characteristics the on sensitivity of steady state motions. The general model will be presented through the domains of continuous dynamical systems for this machine-tool. The periodic motions of intermittent cutting will be developed and implemented to describe the solution structure. The switching components at the chip/tool friction boundary will be discussed in regard to work-piece characteristics.
An Experimental Investigation Into the High Speed Turning of Ti-6Al-4V Titanium Alloy
Authors: Srivastava Anil K. , Iverson Jon
Published: April 2011

Titanium and its alloys have seen increased utilization in military and aerospace applications due to combination of high specific strength, toughness, corrosion resistance, elevated-temperature performance and compatibility with polymer composite materials. Titanium alloys are difficult to machine due to their inherent low thermal conductivity and higher chemical reactivity with other materials at elevated temperatures. In general, temperature related machining difficulties are encountered at production speeds in the range of 60 m/min and high-speed machining of these alloys has created considerable interest to researchers, tool manufacturers and end users. This paper provides recent results obtained during turning operation with the aim of improving machinability of titanium alloys. Several tests have been conducted using (i) micro-edge prep geometry of the inserts, (ii) ultra-hard PVD coated, and (iii) nano-layered coated inserts and the effects of speeds and feeds during turning of Ti-6Al-4V titanium alloy are discussed. The initial tests have been conducted under orthogonal (2-D) cutting conditions with no coolant application. Based on these results, several oblique cutting (3-D) tests have been designed and conducted to study the effect of various types of ultra-hard and nano-layered coatings at higher cutting speeds under flooded coolant conditions. The effects of speed and feed on cutting force and tool wear are presented in this paper.
Metal Foam Filled Hydroformed Tubes: Production and FEM Simulation
Authors: Strano Matteo
Published: April 2011

The marriage of the Tube HydroForming (THF) process with metal foams is interesting for different reasons: a) THF parts are naturally suited as cases to be filled by an internal metallic foam reinforcement and therefore for structural applications; b) the possibility to increase the mechanical strength of hydroformed parts allows to plan the THF process more freely and flexibly. These components, made of an outer hollow thin compact metal skin and a cellular lightweight core may find several applications in different industrial fields. In order to allow for an efficient and effective product/process design with a concurrent engineering approach, the structural performance of these composite parts must be predicted by means of FEM calculation. The optimal combination of tube and metal foam properties must be found. While FEM simulation of bending and hydroforming is state of the art, the accurate FEM simulation of the mechanical behavior of metal foams cannot be considered fully established. In the first part of this paper the foam-filling production cycle of a simple hydroformed aluminum part is shown, in order to discuss some of the design and manufacturing issues that can be faced in FEM based product/process analysis, concerning the thermal effects on the tube materials, the ability of completely filling the tube, the foam/tube interface conditions, the uniformity of cell distribution. A few potential applications of foam-filled hydroformed tubes are also presented. In the second part of the paper, the common methods and formulations for FEM simulation of foam based structures are discussed, and a new and very promising method is proposed.
Ice Crystallization in Ice Cream Manufacturing by Coupled Computational Fluid Dynamics and Population Balance Method
Authors: Miller Mark J. , Xin X. Jack , Pei Z. J. , Schmidt Karen A.
Published: April 2011

Freezing is the single most influential step of ice cream manufacturing. During freezing, multiphase flow, ice crystal nucleation and growth, phase change, and viscous shearing all play roles in ice cream crystallization. In this work, ice crystallization of a sucrose solution is investigated using a coupled computational fluid dynamics and population balance method. The dynamic freezing process that takes place in a scraped surface heat exchanger (SSHE) is simulated using a sucrose solution as a model material. Ice crystal nucleation and growth kinetics are described by population balance equations. Effects of multiphase, phase change, and shearing from scraping in a continuous freezer on ice cream formation are investigated, and the fluid flow, temperature distribution and ice crystal size are predicted. The method predicts trends similar to experimental observations, and provides insight into how processing conditions affect ice cream manufacturing.
Current Status of Peel Grinding Technology
Authors: Hitchiner Michael P.
Published: April 2011

Paper reviews the development of peel grinding from what was once a highly specialized process for finishing small hardened ferrous materials involving CBN grain in an ultra-tough metal bonded wheel requiring ultra-high work and wheel speeds in oil coolant for small batch production to replace plunge grinding. Recent developments are now questioning the need for the bond resilience with its attending difficulties of dressing, oil coolant, hard workpieces, or even high wheel or work speeds. The process has progressed to now challenge not only plunge grinding but other machining processes including rough machining of billets, hard turning and finish turning of steels in the soft state. The use of peel grinding is also considered in combination with other machining processes.
Fracture-Based Formability Prediction in Incremental Forming
Authors: Malhotra Rajiv , Xue Liang , Cao Jian
Published: April 2011

In recent years considerable research has been done in incremental forming due to its greater process flexibility and higher forming limits. In incremental forming the formability depends to a great extent on the toolpath via the incremental depth being used. A lack of fracture models to accurately predict failure in this process has hampered the utilization of incremental forming as an industrial level forming process. This paper deals with the use of a new fracture model in which both the effects of hydrostatic pressure and shear on damage are incorporated to accurately predict fracture in Single Point Incremental Forming.
Fabrication of Nickel/Zirconium Anode for Solid Oxide Fuel Cells by Electrochemical Method
Authors: Pothula Surya V. , Gan Yong X.
Published: April 2011

In this work, preparation of discontinuous nickel films on zirconium by electrochemical deposition of Ni-Cu alloy followed by selective anodic etching of the more noble metal, copper, was performed in an aqueous solution at room temperature. Potential varying electrodeposition produces were applied to obtain Ni-Cu alloys on Zr substrate. It is found that the Ni content increases as the deposition potential becomes more negative. Cyclic voltam-metric data indicate that the anodic dissolution of nickel is retarded by passivation. By taking the advantage of nickel passivation, selective anodic etching of Cu is achieved. Multicyclic electrochemical alloying/dealloying process makes the film rich of nickel and complete dealloying of copper.
Rationalizing the Fabrication Conditions for Nanoporous Gold
Authors: Baharani Shruti M. , Gan Yong X.
Published: April 2011

Electrochemical dealloying has proven to be an efficient way of fabricating nanoporous gold. The morphology of nanoporous gold can be tailored by controlling factors such as the etching time, temperature of the electrolyte used, composition of the alloy, pre and/or post heat treatment and voltage applied to suit applications such as fuel cell electrodes and sensors. This work aims at studying the effect of some of these factors, for example the electrolyte concentration on the dealloying processes, especially on the morphology. A model relating the factors including the processing parameters and the pore size is established by statistical approaches using the Design Expert 7.1 software. An equation that correlates the individual as well as the interaction effects on nanoporous gold is proposed. The validity of the equation is verified by existing research results and also by carrying out a series of tests.
Dimension Error in the Presence of Process and Machine Error in End Milling
Authors: Chiang H. N. , Wang J. J. , Hsu F. C. , Li Y. J.
Published: April 2011

The contribution of process and machine errors to the dimension error of machined part was investigated in this study. End milling was performed in two different types of machine configuration (XFYZ and XYFZ) in order to evaluate the dimension error caused by process and spatial errors of machine tools. The spatial machine errors were obtained by the sequential diagonal method with the Doppler laser displacement meter. For the process error, a simple average force model for a single cutting point and the identified structure stiffness is used to calculate the force induced surface error along the tool axis direction. Surface error due to tool runout effect is also considered as a contributing factor to the process error. Finally, the prediction model of dimension error for end milling was established by analyzing the machine positioning error and process error. The error prediction model was confirmed by different radial depth of cut and cutting fluid supply parameters. The dimension error of machined part was measured by the coordinate measuring machine. The experimental results reveal that the proposed model is useful in predicting the dimension error in an end milling process.
Method for Evaluating Machining Toolholder-Spindle Unbalance Due to Chips at the Toolholder Interface
Authors: Agapiou John
Published: April 2011

Machining process monitoring method is developed for detecting and diagnosis of the presence of chips at the toolholder-spindle interface. Although toolholders can be simply balanced before they are placed in the spindle, there can be some balancing problems remaining when one or more loose machining chips are attached at the toolholder-spindle interface(s) during a tool change. A method is developed by considering the natural and geometric unbalances of the toolholder-spindle system combined with an analysis of the toolholder tilt due to the presence of loose machining chips around the spindle. The method can be integrated on-line as a real-time expert diagnostic system for toolholder tilt due to the presence of loose machining chips at the spindle nose. The expert diagnostic system makes intelligent decisions on toolholder unbalance and concerns with chips at the interface that result in unwanted tilting and vibrations. The tool unbalance algorithm was able to monitor the toolholder tilting according to the results of this study.
Multi-Phase FE Model for Machining Inconel 718
Authors: Long Yu , Guo Changsheng , Ranganath Santosh , Talarico Ronald A.
Published: April 2011

Inconel 718 presents significant challenges in machining attributable to the secondary hard niobium and titanium carbide phases. Machined surfaces typically show a tendency of those brittle carbides to crack, drag and smear under the cutting tool. This paper presents a finite element modeling approach to predict the carbide cracking and distortion phenomenon. The influence of cutting process parameters and cutting edge geometry on carbide damages will be investigated with the model. The model results will be qualitatively compared with SEM observations of the machined surfaces.
Microstructural Changes of AZ31 Magnesium Alloys Induced by Cryogenic Machining and Its Influence on Corrosion Resistance in Simulated Body Fluid for Biomedical Applications
Authors: Pu Z. , Dillon O. W. , Jawahir I. S. , Puleo D. A.
Published: April 2011

Poor corrosion resistance is one of the major disadvantages of magnesium alloys that inhibits their wide application. It was reported frequently that the alloys’ microstructure has a significant influence on their corrosion resistance. In this study, cryogenic machining is used as a severe plastic deformation tool to modify the surface and subsurface microstructures of an AZ31 Mg alloy. Liquid nitrogen is applied to suppress grain growth caused by large heat generation during machining. “White layers”, where grain boundaries were invisible, were shown to form on the surface and subsurface after machining. The hardness of this layer was about 60% larger than the bulk material. The tool edge radius and the cutting speed have profound influence on the microstructures. Preliminary results from immersion tests in simulated body fluid showed that the corrosion resistance of the AZ31 Mg alloy was enhanced due to the formation of white layer.
Development of Multiple Melt Modulation Valves for Enhanced Injection Molding
Authors: Tantrapiwat Akapot , Coulter John P.
Published: April 2011

New melt modulation system with multiple control valves was successfully developed to facilitate melt control in cold runner based injection molding. The entire valve mechanism and port geometry were significantly improved. The new valve gave better control characteristic and can be made inexpensively. Valve driving mechanism was also redesigned to be more compact and easy to be installed in a limited mold space. It allows four control valves to be placed in the same mold in which only two original valves were able to fit. The four valve melt modulation performed on a runner system that the effect of melt flow from each valve was influenced by all other valves. The interaction between four valves caused complicated behavior and also a difficulty to establish valve control parameters. A reciprocal search method was utilized and able to determine valve control variables within a reasonable number of trials. Experimentation was done on a potential case study that included both family molding and weld line positioning problems. As a part of the outcome, a simple gain modification was developed and able to find an optimum solution. The technique was carried out in both traditional fixed angle and new developed Bang-Bang control methods. The results shows that melt modulation system with multiple control valves was able to effectively control melt behavior and enhanced filling process.
Laser Induced Plasma Micro-Machining
Authors: Pallav Kumar , Ehmann Kornel F.
Published: April 2011

A new micro-machining process that is motivated by the need to overcome the various limitations associated with the micro-EDM (μ-EDM) process is introduced. The limitations in μ-EDM are primarily due to the requirement of a conductive electrode and workpiece, tool wear, and complex wear compensation strategies. The new process, termed “laser-induced plasma micro-machining” uses a laser beam to generate plasma in a dielectric near the workpiece surface whose explosive expansion results in material removal by mechanisms similar to those that occur in μ-EDM.
Fabrication of PCD Micro Tools Using Block EDM Method and Their Application to Different Microstructures in Brittle and Hard Materials
Authors: Perveen Asma , Wong Y. S. , Rahman M.
Published: April 2011

Fabrication of microelectrodes with different shape has become so important due to the high demand of industrial products not only with diversified shape but also of reduced dimension. However, to date, fabrication of different shapes in single setup is not possible and also need special indexing attachment. To solve this problem, in this study, a specially designed block containing three V slot of 60° 90° 120° has been designed and fabricated using wire cut machine to facilitate the fabrication of different shape micro-electrode. Then, with the help of block electro discharge machining method using this specially designed block, the feasibility of fabrication of microelectrodes with symmetrical and non-symmetrical section e.g. conical tool of angle 60° 90° 120°, rectangular, triangular, circular and semicircular tool from commercially available polycrystalline diamond rod has been investigated. As the size of electrode is of micron scale, multi-pass machining strategy has been taken to reduce the volumetric material removal, and thus to diminish the possible electrode breakage, which is especially significant. Finally, this strategy of using specially designed block has been found to be feasible for producing microelectrodes of various symmetrical and non-symmetrical sections down to few microns. In addition to this, the capabilities of these fabricated tools have been depicted by recommending few applications on both conductive and nonconductive material.
Investigation on Porosity Formation in AA6082 Hybrid Laser-GMAW Welding
Authors: Ascari Alessandro , Fortunato Alessandro , Orazi Leonardo , Campana Giampaolo , Tani Giovanni
Published: April 2011

This paper refers to the results obtained in the investigation on bubbles formation in hybrid Laser-GMAW welding. Bead on plate weldings were obtained on 8 mm thick AA6082 plates and the process parameters investigated were: GMAW current, arc transfer mode and mutual distance between arc and laser sources. Bubbles were observed by means of X-ray inspection techniques and measured exploiting an image analysis software. Finally a correlation, based on analysis of variance, between process parameters and porosity formation is proposed.
Characterization and Prediction of Texture in Laser Annealed NiTi Shape Memory Thin Films
Authors: Satoh Gen , Yao Y. Lawrence , Huang Xu , Ramirez Ainissa
Published: April 2011

Thin film shape memory alloys are a promising material for use in micro-scale devices for actuation and sensing due to their strong actuating force, substantial displacements, and large surface to volume ratios. NiTi, in particular, has been of great interest due to its biocompatibility and corrosion resistance. Effort has been directed toward adjusting the microstructure of as-deposited films in order to modify their shape memory properties for specific applications. The anisotropy of the shape memory and superelastic effects suggests that inducing preferred orientations could allow for optimization of shape memory properties. Limited work, however, has been performed on adjusting the crystallographic texture of these films. In this study, thin film NiTi samples are processed using excimer laser crystallization and the effect on the overall preferred orientation is analyzed through the use of electron backscatter diffraction and x-ray diffraction. A 3-dimensional Monte Carlo grain growth model is developed to characterize textures formed through surface energy induced abnormal grain growth during solidification. Furthermore, a scaling factor between Monte Carlo steps and real time is determined to aid in the prediction of texture changes during laser crystallization in the partial melting regime.
Transient Analysis of Downtime Event in Manufacturing Systems
Authors: Chang Qing , Liu Jianbo , Biller Stephan , Xiao Guoxian
Published: April 2011

In manufacturing industry, downtimes have been considered as major impact factors of production performance. To improve the system performance in real-time and properly allocate limited resources/efforts to different stations, it is necessary to quantify the impact of each station downtime event on the production throughput of the whole transfer line. Complete characterization of the impact requires a careful investigation of the transients of the line dynamics disturbed by the downtime event. We study in this paper, the impact of single isolated downtime event on the performance of inhomogeneous serial transfer lines. Our mathematical analysis suggests that the impact of any isolated downtime event is only apparent in the relatively long run when the duration exceeds a certain threshold called opportunity window. The size of the opportunity window not only depends on the initial buffer levels but also depends on the location and the processing speed of the slowest station. Analytical solutions of the opportunity window and the loose upper bounds for the recovery time are also provided in the paper as two separate theorems. Despite the fact that the paper focuses on the transient analysis of single isolated downtime event, the results are applicable to opportunistic maintenance scheduling, personnel staffing and downtime cost estimation.
Simulation Model for the Shape Error Estimation During Machining With Flat Lapping Kinematics
Authors: Deja Mariusz
Published: April 2011

The selection of a finishing process for a particular application depends on part shape and size, ease of fixturing, requirements concerning the acceptable shape errors. Lapping is the basic flattening process which allows for achieving a high degree of flatness and parallelism of machined parts. It is still one of the most common processes to flatten the sliced silicon wafers. Grinding or wire-sawing induced waviness can be effectively removed or reduced by lapping. A required high degree of the tool flatness is not maintained permanently. The active surface of the tool used for machining with lapping kinematics has some shape errors of concavity or convexity due to the wear. This in turn influences the shape accuracy of the workpiece and the tool flatness must be checked after machining of some workpiece batches. Depending on the tool shape error either the facing operations are carried out to flatten the active surface of the tool or proper kinematical parameters are applied which allow for obtaining required workpiece flatness. Computer simulations can be useful to make o proper decision about achievable accuracy for actual tool shape error. Simulation model for the shape error estimation based on the kinematics of lapping and local shape errors of the tool is presented in the paper. The movement of the workpiece is analyzed and the average distance from the workpiece surface, represented by discrete points, to the tool surface is calculated. Proposed model can be applied for lapping or grinding with single or double discs lapping kinematics. Geometrical and kinematical relations with some simulations are presented in the work.
Micro Quantity Internal Cooling (MQUIC™) of Cutting Tools for Increased Productivity While Machining Ti-6Al-4V
Authors: Bhatnagar Samved , Endres William J.
Published: April 2011

Machining of space age materials like Ti-6Al-4V is associated with thermally activated wear mechanisms which lead to rapid tool failure and increased machine downtime. The high strength and low thermal conductivity of Ti-6Al-4V can reduce tool-life significantly at high cutting speeds adding drastically to the per-unit cost. A new concept, Micro Quantity Internal Cooling (MQUIC™) has been developed to extend the tool-life and/or enable higher cutting speeds while machining Ti-6Al-4V. The concept involves introducing flow (coolant) in a micro-duct placed inside the tool and close to the cutting edge, thus bringing the cooling source close to the heat source (chip-contact area). In this research, experiments have been conducted to compare the performance (wear rates) of cutting tools using the MQUIC™ concept with those run under dry or flood conditions. Further, two levels of feed and cutting speed are selected for the experiments so as to be able to investigate the combined effect of parameters on tool performance. Physical testing employing coolant consumption of less than 5% of typical flood coolant rates proves the viability of the concept by demonstrating wear rates of 1/3 to 1/2 those of flood cooling. The testing also proves the application of the MQUIC™ concept to enable higher cutting speeds than the current industry standard for machining Ti-6Al-4V. This paper presents the experimental setup, methodology and results obtained while testing the feasibility of the concept.
Soft Biomaterial Study for 3-D Tissue Scaffold Printing
Authors: Geisler Chris G. , Li Ho-Lung , Wootton David M. , Lelkes Peter I. , Zhou Jack G.
Published: April 2011

In 3-D scaffold printing, it is critical to find a material that is suitable for your printing method, printing speed, and ease of use. For a biomaterial to best suit solid freeform fabrication techniques, it must: 1) be a low-viscous solution before being printed, 2) involve easily joined on-substrate mixing to form a homogenous gel, 3) have a short solution to gel transition time, 4) be a mechanically strong gel, and 5) have an irreversible gelation processes. Ionic crosslinkable, photocrosslinkable, and thermo-sensitive hydrogels have all been investigated and found to not fully satisfy our every requirement for SFF printing. Ionic crosslinking hydrogels can gel rapidly but tend to involve additional steps for crosslinking like freeze drying, stirring, and shaking, while some form beads, not homogenous gels. Some photocrosslinkable hydrogels would not work due to the concern for viability of cells in initial gel layers receiving copious amount of UV light. Thermosensitive hydrogels meet most of the requirements except that they are reversible gels. A new type of gel that obtains the qualities of a photocrosslinkable and thermosensitive hydrogel satisfies every requirement. A PEG-PLGA-PEG thermosensitive triblock copolymer additionally crosslinked with photocrosslinkable Irgacure 2959 allows for quick transition from solution to gel with a post-processing step utilizing UV light would add additional crosslinks to the gel structure resulting in an irreversible hydrogel.
Biomimetic Design, Modeling and Manufacturing of Chitosan/Gelatin Scaffolds for 3D Vascularized Liver Tissue Construct
Authors: Gong Haibo , Zhang Qingwei , Lelkes Peter I. , Zhou Jack G. , Li Dichen
Published: April 2011

Despite the significant progress in engineering fairly thin tissues that contain or acquire vascular structures (e.g. skin, cartilage and bladder), it has been markedly difficult to construct metabolically demanding organs with thicker and more complex structures (e.g. heart, lung, kidney, and liver). This research explores a new generation of clinically significant (500cm3) liver tissue constructs made of a new natural polymer composite, imbedded with optimized network of flow channels, and manufactured using innovative structured porogen and lost-wax molding methods to receive a 3D vascularized liver tissue construct. Biomimetic designed liver scaffolds with 3D network of flow channels were optimized based on simulation of fluid flow inside the channel network. Combining structured porogen method, lost-wax molding and freeze-drying technique, both macro (1 cm) and the micro (500μm) scale structures were achieved in chitosan/gelatin liver scaffolds. Liver parenchymal cells were seeded in the 3D scaffolds and cultured for 3 days. Evident cell growth was found both at the bottom and the center of the scaffolds, which indicates the biocompatibility is maintained through the manufacturing process and 3D channels improved cell in-growth.
A New Bending Technique for Very Thin Metal Tubes
Authors: Zhang Shi-Hong , Chen Shi-Qing , Xiao Han , Liu Hai
Published: April 2011

A new bending technique was presented for forming very thin metal tubes, which is characterized by ball filler in the tube as force-transferring media during bending process. Due to the good flow capacity and non-uniform pressure, ball filler is considered as an alternative filler to bend very thin tubes. The experiments of ball filler push bending were carried out for very thin copper tubes. The results indicate that the back pressure and lubrication condition have great effects on the forming quality of the tubes. As the back pressure increases and/or lubrication condition improves, the tube surface quality is improved. The ovality of the bent tube is small, and the intrados and extrados wall thickness are both thickened and changed uniformly, which indicates that the new process applied to form the very thin tubes is feasible.
Stress and Strain Analysis on Incremental Sheet Metal Forming With Multiple-Head Tool
Authors: Wang Yongjun , Xiao Xudong , Yuan Zhenyi , Wu Weichao , Cao Jian
Published: April 2011

A new method of incremental forming was introduced and investigated, which used a tool with multiple heads turning around holding mandrels freely. In order to investigate the advantages of this method, experiment and forming analysis were done. In this process, some truncated components were made from thin Al2024-O Aluminium plate with inward tool path. An analysis model of tool path was created with geometric method. A calculation of strain and stress distribution was developed and compared with experimental results. And an investigation of forming limit was made by experiments with truncated pyramid and strip shape. The results agreed with each other. It has been shown that this method can easily improve the forming efficiency and surface roughness.
Reverse Bulging in Hydro/Pneumatic Sheet Metal Forming Operations: Is it Worth It?
Authors: Abu-Farha Fadi
Published: April 2011

The merits of warm and elevated temperature hydro/pneumatic sheet metal forming operations, most prominently superplastic and quick plastic forming, have been ever counteracted by two major drawbacks: slow forming rates and non-uniform thickness distribution with potentially severe thinning. Trying to resolve one of the two issues has generally led to escalating the other, so a compromise based on the nature of the part being formed is often targeted. To tackle the latter of the two issues, imposing a pre-thinning reverse bulging step has been shown to ease the problem with specific part geometries that involve large plastic strains and intricate details. The aerospace industry, however, is the prime sector that is able to afford the “seemingly” prolonged forming times associated with this approach. Yet with the lack of adequate details on the implications of utilising reverse bulging, this effort explores some of the hidden merits of the approach. A recently-developed simple monitoring technique for providing a direct feedback on the sheet’s advancement during pneumatic forming operations, coupled with an interrupted testing methodology, are utilised to have a closer look at the process. The results reveal significant time-savings that can be achieved with the proper use of reverse bulging, for both simple and complex part geometries.
Machinability Study of SiC Nano-Particles Reinforced Magnesium Nanocomposites During Micro-Milling Processes
Authors: Li Juan , Liu Jian , Xu Chengying
Published: April 2011

This paper experimentally investigates the machinability of Magnesium Metal Matrix Composites (Mg-MMCs) with high volume fractions of SiC nano-particles. Samples of Mg-MMCs with 5 Vol.%, 10 Vol.% and 15 Vol.% reinforcements of SiC nano-particles were studied and compared with pure Magnesium. Different feedrates and spindle speeds were chosen as varied cutting parameters. Cutting forces, surface morphology and roughness were measured to understand the machinability of the four different materials during the micro-milling process. Based on the experimental results, it is observed that the cutting force increases with the increase of the spindle speed, the feedrate and/or the volume fraction. A drastic increasing rate is observed when the nano-particles’ volume fraction is increased from 5 to 10 Vol.%. The effect of the volume fraction is also studied in frequency domain, combined with the effect of the spindle speed and feedrate. More detailed theoretical analysis will be further studied to better understand the effect of the volume fraction on the machined surface quality and machining productivity.
Effect of Multiple Pulses on the Deformation Behavior of Ultrathin Metal Foils in 3D Micro-Scale Laser Dynamic Forming
Authors: Li Ji , Cheng Gary J.
Published: April 2011

Laser dynamic forming (LDF) is a novel high energy rate microfabrication technique, which makes use of the shock pressure induced by laser to generate dynamic high strain rate 3D forming of thin films. In LDF process, a high shock pressure accelerates the workpiece to a high velocity and deforms it into complex 3D shapes. The forming velocity of the workpiece imparted by a single laser pulse with high energy may exceed the critical forming velocity of the material, and thus causing it to fracture. This problem is more severe when 3D structure of large aspect ratio needs to be formed. To overcome this problem, multi-pulse laser dynamic forming is investigated in this study. The total laser energy is evenly distributed in different laser pulses to keep the forming velocity below the critical forming velocity of the material. The effects of the multiple-pulse LDF on the deformation behavior of ultra thin foils are investigated. The deformation depth and thickness variation distribution of the formed 3D features are characterized to reveal these effects. In addition, the effects of vacuum conditions on multiple-pulse LDF process are carried out. It is found that the bounce off of the foil can be effectively reduced by multiple-pulse LDF and the final shape could be controlled much more accurately. By extending single pulse LDF to multi-pulse LDF, the forming capability of LDF is further enhanced, and thus enlarges the applicable range of this technique.
Study of Manufacturing Process Optimization of Rigid Boards of LDPE/Al Composite Recycled
Authors: Hidalgo Miguel A.
Published: April 2011

This study investigates the feasibility of using recycled low density polyethylene (LDPE) and aluminum of Tetra Pak, to manufacture experimental composite rigid board. The rigid board was made through a hot press. The effects of tensile, flexural, and water absorption process on LDPE/Al plastic composites were studied. Based on the findings in this work, it appears that recycled materials can be used to manufacture value-added panels without having any significant adverse influence on board properties. It was also found that the compounds of LDPE/Al are significantly affected by the effect of compaction pressure during processing, especially in the tensile strength and water absorption, were significant. The composite presents low water absorption, and acceptable tensile strength.
Short-Time Fourier Transform Method in AE Signal Analysis for Diamond Coating Failure Monitoring in Machining Applications
Authors: Lu Ping , Chou Y. Kevin , Thompson Raymond G.
Published: April 2011

Coating failures due to delaminations are the primary life-limiting criteria of diamond-coated tools in machining. Process monitoring to capture coating failures is thus desired to prevent from poor part quality and possible production disruption. Following previous studies of AE signal analysis for diamond coating failure monitoring in machining applications, this research applied a short-time Fourier transformation (STFT) method to capture the coating failure transition during cutting. The method uses sub-divided signal segments, in a continuous manner, for the fast Fourier transform (FFT) analysis and computes the amplitude ratio of high vs. low frequencies as a function of cutting time during a cutting pass. The results show that during the coating failure pass, a clear sharp increase of amplitude ratio (value change over one) of high/low frequency occurs along the cutting time. On the other hand, the amplitude ratio only exhibits a certain low range fluctuations in other passes, e.g., initial cutting and prior to failure passes. Thus, it can be suggested that the applied STFT method has a potential for diamond coating failure monitoring. However, for coating failure associated with a smaller tool wear (less than 0.8 mm flank wear-land width), the amplitude ratio plot from the STFT analysis may not clearly show the failure transition.
Case Studies of Diamond-Coated Tool Cutting Simulations: Coating Thickness and Cutting Speed Effects
Authors: Qin Feng , Chou Y. Kevin
Published: April 2011

Due to the interwoven effects in both diamond deposition and subsequent machining processes, the tool geometry and process parameters have compound effects on the thermal and mechanical states in diamond-coated cutting tools during machining. For example, increasing the coating thickness tends to increase deposition-induced residual stresses at the tool edge interface. Further, a thick coating will introduce a greater machining load due to an enlarged edge radius. However, it has not been investigated how the coating thickness affects the thermo-mechanical behaviors of diamond-coated tools during machining. In a previous study, finite-element based simulations were developed to conduct systematic analyses of diamond-coated tool cutting. In this work, the developed 2D cutting simulations that incorporate deposition residual stresses were applied to evaluate the coating thickness and cutting speed effects on the tool stress contours, tool temperatures as well as the interface stresses around a cutting edge. The major findings can be summarized as follows. (1) The coating thickness effect on the first principal stress is minor. A thicker coating can decrease cutting temperature effectively, but increase the thrust force noticeably. Additionally, a thicker coating is also favorable for the reduction of interface radial normal stresses around the cutting edge. (2) For a constant coated tool edge radius, decreasing the substrate edge radius (while increasing the coating thickness) will elevate the maximum first principal stresses but significantly reduce tool temperatures and the interface radial normal stresses. (3) The cutting speed has little effect on the first principal stresses, but strongly affects the cutting tool temperatures. Moreover, the interface radial normal stresses and circumferential stresses decrease with the increase of cutting speed, which is intuitive since higher cutting temperatures associated with a high cutting speed are expected to relieve high deposition stresses.
Machining Characteristics of High Speed Dry Milling of Biodegradable Magnesium-Calcium Alloy
Authors: Salahshoor M. , Guo Y. B.
Published: April 2011

Metallic degradable biomaterials have attracted a huge attention lately for orthopedic fixation applications. Binary magnesium and calcium (Mg-Ca) alloys have emerged as a promising choice in terms of biocompatibility to avoid stress shielding and provide sufficient mechanical strength. In this paper, efficient and ecologic machining of a lab-made Mg-Ca alloy with 0.8 wt% calcium, cutting speeds of up to 47 m/s, and without coolant are investigated. Polycrystalline diamond inserts are applied and the possibilities of flank built-up formation, chip ignition, and tool wear are sought during the cutting experiments with the aid of a developed on-line, optical monitoring system. Chip morphology characteristics produced by different combinations of cutting parameters, i.e. cutting speed, feed, and depth of cut are studied.
Fabrication and Characterization of Bulk Nanocrystalline Layer on Steel Components With Different Microstructures by Air Blast Shot Peening
Authors: Waikar R. , Guo Y. B.
Published: April 2011

The fabrication of nano-crystalline (NC) layers in pearlitic and martensitic carbon steels viz. AISI 1018, 1045 and 1075 alloys using ABSP has been studied. The cross-sectional microstructure of the samples showed that a gradual reduction of the grain size near the surface until a clearly demarcated NC layer was observed. The NC layers were characterized using optical, scanning electron microscopy (SEM), transmission electron microscopy (TEM), microhardness and nanohardness measurements. 2D surface topography of the peened surface was also carried out to measured surface roughness. The roughnesses of the peened surfaces were dependent on the hardness of the sample. Samples with higher hardness had lower surface roughness value. NC layers varying from 5 to 15 μm were observed using the optical and SEM images in the different types of steels. The SEM images clearly showed the dissolution of cementite phase in the NC layers. The nanohardness measurements of the steels showed that the NC layers had much higher hardness than the bulk material. The microhardness measurements also confirmed the mentioned phenomena. A TEM study was carried out on the NC layer and the grain size was confirmed to be 50 to 80 nm.
Drilling of Silicon Based Solar Panels: A Review
Authors: Cong W. L. , Feng Q. , Pei Z. J.
Published: April 2011

Solar panels have been developed to convert the solar energy to electricity. Since most solar panels are silicon based, they inherit the mechanical properties of silicon, such as brittleness and hardness. These properties might lead to cracking in workpieces and low tool lives in traditional machining processes. In solar panel manufacturing, to increase the efficiency of solar cells, electrical contacts on the front side of the panel need to be connected to those on the back side. Therefore, holes of different sizes are required to drill in silicon solar panels for certain designs. This paper reviews the literature on different drilling processes for silicon solar panels and summarizes merits, shortcomings, and special characteristics of each method.
A Statistically Based Determination of the Depth of the Machining Affected Zone in Nickel-Based Superalloys Using MATLAB
Authors: Richardson B. J. , Bunget Cristina , Kurfess Thomas R.
Published: April 2011

The surface integrity of a machined surface is a critical requirement in high performance applications such as gas turbine foils. Multiple aspects are incorporated in surface integrity, such as surface finish, changes in microstructure, and consequently residual stresses. This research focuses on detection of the presence of the subsurface damage and estimation of the depth of the damage, as related to the changes in microstructure. A statistically-based methodology for estimation of the depth of the machining affected zone (MAZ) using scanning electron microscope (SEM) images is developed and incorporated in MATLAB software, with the objective of having an automated and also more exact method than optical evaluation. The method is applied for estimation of the depth of the MAZ for nickel-based superalloys. The results of this work are being extended to correlate the MAZ with cutting parameters and conditions to determine the onset of subsurface damage, predict the extent of the MAZ and, ultimately, control its characteristics. Furthermore, this method can be extended for the analysis of different aspects of the microstructure (i.e., dimensions of grains) and estimating the amount of strain and residual stress in the damaged layer.