bluuebunny/crossref_metadata_2025 huggingface dataset:
Interlayer Strain Monitoring of Hybrid Composites With Carbon Nanofiber Paper Using Fiber Bragg Grating Sensors
Authors: Zhao Xuefeng , Gou Jihua , Song Gangbing
Published: October 2008

Graphite/epoxy prepregs are typically used to manufacture aerospace composite structures through autoclave processing. However, the vacuum-assisted resin transfer molding (VARTM) process has recently received increasing attention as a low-cost method to fabricate quality aerospace structures. In this study, carbon nanofiber paper was integrated into composite laminates using the VARTM process. The carbon nanofiber paper has a porous structure with highly entangled carbon nanofibers. The carbon nanofiber paper can be employed as an inter-layer and surface layer to enhance the damping properties of the nanocomposites. To study the integration performance of nanocomposites with nanofiber paper layer, Fiber Bragg Grating (FBG) sensors were embedded into interlayers of the composite. Two kinds of nanocomposite specimens with FBG sensors were designed and fabricated to study the strain distribution characteristics among different layers. The interlayer strains in under static loads were measured simultaneously to test whether nanofiber paper can be successfully integrated into glass fiber composite. The test results show the two different layers of nanofiber paper and glassfiber are fully integrated to the composite. In addition, a novel tensile test of carbon nanofiber paper-enabled nanocomposites using FBG sensors was conducted to demonstrate the bonding strength between the nanofiber paper layer and the glassfiber layer. The scanning electron microscopy (SEM) technique was conducted to investigate the impregnation of carbon nanofiber paper and FBG sensors by the resin during the VARTM process. The study shows that a complete penetration of the resin through carbon nanofiber paper and FBG sensors was achieved.
Nanotailored Thermoplastic/Carbon Nanotube Composite Strain Sensor
Authors: Pham Giang T. , Colombo Alessio , Park Young-Bin , Zhang Chuck , Wang Ben
Published: October 2008

This paper presents the development of polymer-nanofiller systems as strain sensor materials and the development of novel sensor fabrication and characterization techniques. The developed sensor has shown to overcome the limitations of conventional strain sensors — having the capability to measure macroscale strains in any desired direction over a finite surface area, which may be subjected to combined loading modes, including tension, compression, flexure, and shear. They have sufficient flexibility and toughness to accommodate most curved surfaces and corners in components and structures. The methodologies use high aspect ratio multi-walled carbon nanotubes (MWNTs) in order to take advantage of their capability to form efficient conductive network. The results will lead to tailoring of sensor performance, particularly sensitivity factor, by controlling conductive network and optimizing sensor design and fabrication. To date, sensitivity factor of almost 20 at 1 wt.% of MWNTs in poly(methyl methacrylate) (PMMA) has been achieved. The developed sensor can be used in various military and commercial applications, including macroscale strain sensing over a wide surface area (e.g. aircraft skin), high sensitivity strain sensing on stiff components, and crack detection at critical stress concentrated regions for health monitoring.
Cure Kinetics of Nanocomposites Prepared From Aqueous Dispersion of Nanoclay
Authors: Aktas Levent , Altan M. Cengiz
Published: October 2008

The effect of nanoclay on the cure kinetics of glass/waterborne epoxy nanocomposites is investigated. First step in sample preparation involves dispersing Cloisite® Na+, a natural montmorillonite, in distilled water at 70°C with the aid of a sonicator. Then, desired amounts of dicyandiamide and 2-methyl imidazole, serving as cross-linkers, are mixed to the aqueous nanoclay solution. As the mixing continues, Epi-Rez 3522-W-60 waterborne epoxy resin is introduced to the solution and the compound is mixed for an additional 30 minutes. The nanoclay content of this batch is adjusted to be at 2wt%. An identical second batch, which does not comprise nanoclay, is also prepared to serve as the baseline data. Glass/waterborne epoxy prepregs containing 30% glass fibers are prepared from these batches and used to characterize the effects of nanoclay. The evolution of viscoelastic properties during curing are characterized by the APA2000 rheometer. Using the storage and loss moduli profiles during curing, gel time and maximum storage modulus are characterized. Effect of nanoclay on the glass transition temperature is determined by applying an additional temperature cycle following the cure cycle. In addition, mechanical performances of the samples are characterized by three point bending tests. Nanoclay is observed to yield 2-fold higher storage modulus during curing. Rate of curing is measured to be substantially slower for the samples comprising nanoclay. In addition, glass transition temperature improved by 5% to 99°C with the addition of nanoclay compared to 94.5°C for the samples without nanoclay. Flexural stiffness of the samples containing nanoclay is measured to be 20% higher than the samples without nanoclay while the strength remained virtually unaffected.
Factors Influencing the Morphology Development of Epoxy Nanocomposites
Authors: Chen Chenggang
Published: October 2008

Polymer nanocomposites draw great interest due to their unique nanostructures and improved properties [1–2]. Epoxy is a widely-used thermosetting material. The research on the epoxy layered-silicate epoxy nanocomposite has exploded in the last decade [3–9]. The morphology of nanocomposites is the key to making high-performance nanocomposites. In this presentation, the factors influencing the morphology development behavior of epoxy nanocomposites will be discussed. The factors to be investigated include organoclay, epoxide, and curing agent. In this study, the aliphatic diamine (Jeffamines) with different molecular weights and aromatic diamine were selected as the curing agents, S30B (quaternary onium-montmorillonite) and SC18 (primary oniummont-morillonite) as the organoclays, and Epon 862 and Epon 828 as epoxides. In situ small-angle x-ray scattering (SAXS) was utilized to study the morphology development of the epoxy nanocomposite.
Study of Internal Finishing of Austenitic Stainless Steel Capillary Tubes by Magnetic Abrasive Finishing
Authors: Yamaguchi Hitomi , Shinmura Takeo , Ikeda Ryota
Published: October 2008

This paper studies the internal finishing of capillary tubes using a Magnetic abrasive finishing process. Such tubes are used with nano-scale technologies and meet the demands of the present age in medical and chemical equipment. The finishing characteristics are influenced by the magnetic abrasive behavior against the inner surface of the capillary, which is controlled by the supplied amount of magnetic abrasive and the magnetic force acting on it. The development of the finishing unit identifies the characteristics of the magnetic field, which controls the magnetic force, required for the necessary magnetic abrasive behavior. Finishing experiments using SUS304 austenitic stainless steel capillary tube with 800 μm inner diameter demonstrate the effects of the supplied amount of the magnetic abrasive on the finishing characteristics, and the results suggest a standard method to determine the amount to achieve sufficient finishing. The run-out of the capillary while rotating at high speed under the cantilever tube support method causes instability of the magnetic abrasive behavior. The effects on the finishing characteristics are discussed, and a method to diminish the run-out is applied. Accordingly, this paper presents the conditions required for the internal finishing of capillary tubes and proposes methods to realize them. The internal finishing of 400 μm inner diameter capillary tubes conveys an understanding of the mechanisms involved and demonstrates the usefulness of the proposed methods.
A New Approach in Surface Roughness and Roundness Improvement in Wire Electrical Discharge Turning Based on Statistical Analyses
Authors: Mohammadi Aminollah , Fadaei Tehrani Alireza , Karimi Davoud , Emanian Ehsan
Published: October 2008

In this paper, the effects and optimization of machining parameters on surface roughness and roundness in turning by wire EDM process are investigated. Surface roughness and roundness, were chosen, as the machining parameters to verify the process. In addition, power, time-off, voltage, servo, wire speed, wire tension and rotational speed were adopted for evaluation by Taguchi method. A L18 (21 × 37) Taguchi standard orthogonal array is chosen for the design of experiments. The level of importance of the machining parameters on the surface roughness and roundness is determined by using analysis of variance (ANOVA). The optimum machining parameters combination was obtained by using the analysis of signal-to-noise (S/N) ratio. The variation of surface roughness and roundness with machining parameters is mathematically modeled by using regression analysis method. Finally, experimentation was carried out to identify the effectiveness of the proposed method. A good improvement was obtained.
Numerical Investigation of Opposing Dual Sided Micro Scale Laser Shock Peening
Authors: Fan Yajun , Wang Youneng , Vukelic Sinisa , Yao Y. Lawrence
Published: October 2008

Laser shock peening (LSP) is an innovative process which imparts compressive residual stresses in the processed surface of metallic parts to significantly improve fatigue life and fatigue strength of this part. In opposing dual sided LSP, the workpiece can be simultaneously irradiated or irradiated with different time lags to create different surface residual stress patterns by virtue of the interaction between the opposing shock waves. In this work, a finite element model, in which the hydrodynamic behavior of the material and the deviatoric behavior including work hardening and strain rate effects were considered was applied to predict residual stress distributions in the processed surface induced under various conditions of the opposing dual sided micro scale laser shock peening. Thus the shock waves from each surface will interact in different ways through the thickness resulting in more complex residual stress profiles. Additionally, when treating a thin section, opposing dual sided peening is expected to avoid harmful effects such as spalling and fracture because the pressures on the opposite surfaces of the target balance one another and prohibit excessive deformation of the target. In order to better understand the wave-wave interactions under different conditions, the residual stress profiles corresponding to various workpiece thicknesses and various irradiation times were evaluated.
A Metric for Defining the Energy Efficiency of Thermally-Assisted Machining
Authors: Pfefferkorn Frank , Lei Shuting
Published: October 2008

A significant amount of work has been conducted on thermally-assisted machining with a great deal being focused on laser-assisted machining. The body of work has shown that preheating of the workpiece (usually localized heating) makes it possible to machine certain structural ceramics with a conventional cutting tool, improves the machinability of superalloys, and improves the micro-end milling of metals. A variety of metrics have been used to ascertain the impact of thermal assistance on the machining of these materials including: specific cutting energy, tool wear rate, surface roughness, residual stress, material removal rate, material removal mechanism, cost, and surface integrity. Combined, these quantities provide a good but incomplete description of the process and efficacy of thermal assistance. This manuscript looks at the flow of energy in thermally-assisted machining in an attempt to determine how beneficial preheating is. Some efficiency metrics are suggested and used to study the data that has been collected to date. The total thermal energy deposited in the workpiece is compared to the theoretical minimum required to heat the removed material in order to determine what percentage of the deposited (i.e. absorbed) energy is actually used in assisting the cutting process. This enables a comparison between cutting processes (e.g. end milling and turning) and operating conditions to determine how efficiently the added thermal energy is being used. Compared with other machinability metrics the thermal energy efficiency is used to evaluate how beneficial preheating is to the machining processes studied. Two sets of data are studied: laser-assisted turning of silicon nitride and partially-stabilized zirconia. The specific energy for LAM of silicon nitride is compared to that for grinding of silicon nitride. It is hoped that this presentation will spark debate in the manufacturing community and provide more insight into thermally-assisted manufacturing.
Effects of Pulsed Magnetic Treatment on Mechanical Characteristics of Manufactured Parts
Authors: Klamecki Barney E.
Published: October 2008

The use of magnetic fields to treat manufactured parts is attractive since easy-to-produce, easy-to-control fields can be used at room temperature, in contrast to more complex treatments such as heat treatment. Little research has been done to apply magnetic treatment to the modification and control of mechanical properties, behavior and performance of manufactured parts. This paper contains descriptions of experimental studies of the effects of pulsed magnetic treatment on the residual stress in machined surfaces and in welded thin-wall tubes, and includes a qualitative explanation of some of the results in terms of dislocation density. The machined part results indicated only possibly small effects, and so further experiments were done with thin-wall tubes that were expected to be more susceptible to magnetic treatment, and a more sensitive measurement technique was used. The difference in damping of vibration of untreated and pulsed magnetically treated welded tubes was used as a measure of treatment effects. Two significant results are reported. One is that pulsed magnetic treatment increased damping by up to 20%, with smaller effects in most tests. The other result is that damping increased, decreased, increased, and so on, as the length of magnetic treatment was increased.
Laser-Assisted Imprinting of Self-Assembled Nanostructures
Authors: Wang H. , Lu Y. F. , Yang Z. Y.
Published: October 2008

Nanoscale structuring is a promising area in which the various processing methods are being developed. Based on the advantages of laser processing, associated with improved self-assembly technique, it is very effective to fabricate nanoscale structures, such as 3-D photonic bandgap structures, especially on the materials with high hardness and high melting point. This new approach to fabricating 3-D photonic bandgap structures on silicon will be presented. Self-assembly technique was used to deposit multi-layer of silica microparticles with a size of 0.81 μm. A pulsed KrF excimer laser (23 ns, 248 nm) was applied as the imprinting energy source.
Springback Prediction and Control in Multi-Stage Sheet Metal Forming
Authors: Chen Wei , Kim Gapyong , Zhang Jiahua
Published: October 2008

Several forming operations are required to form a complex part, which is known as the multi-stage forming process. Inherently, the final geometry of the stamped part is affected by springbacks from every forming operation. First, the theory on springback after unloading in bending and the technologies of numerical simulation are investigated. The latter includes the numerical solution procedure of springback in multi-stage forming, the time steps of numerical calculation, and the transmission of blank information from the previous stage to the next. Then a sample automotive structural piece, the upper inner panel, has been simulated and validated. Entire forming procedure is simulated with an explicit-implicit coupled FEA program, which is based on the simulation of “loading-unloading of springback-reloading”. Finally, by means of forming process modification, effects of various diefaces including the drawbeads and stiffening beads are investigated to enhance the final part shape. The validation of simulation procedure and the forming process modification method are presented through the comparison of the simulation results with experimental results.
A Tensile Characterization Study of Metal Sheet in Large-Strain
Authors: Dan W. J. , Zhang W. G. , Li S. H. , Lin Z. Q.
Published: October 2008

A method for determining the strain-stress curve of larger-strain is proposed when plastic instability occurs in standard tension tests. Thin tested steel sheet is subjected to tension loading until fracture occurs. The deformation process is captured with a digital camera. Displacement and strain field of material deformation can be calculated by a mesh-free PIM method. A tensile experiment is simulated to verify that local measuring stress-strain curve by PIM method near the center of the specimen can describe a full stress-strain curve clearly. Numerical simulation results, at different location along the specimen axial, present that different parts of specimen have different deformation distribution in tensile and the center fracture part of tensile specimen is the only region which can experience full strain. The true stress- true strain curves, based on the estimated parameters, are validated in all strain regions by comparison with curves from standard tension tests. The measured curves by PIM method are very stabilization. Compared with several material constitutive equations, The Swift’s equation is very close to experiment curve at plastic deformation.
Prediction of the Volume Fraction of Retained Austenite in Sheet Metal Forming for Trip Steels
Authors: Shan Tikun , Zhang Weigang , Lin Zhongqin , Li Shuhui
Published: October 2008

The dependence of the transformation rate on the multiaxial stress state corresponding to different loading paths is investigated. To achieve different loading paths, single shear uniaxial tension, plane strain and equi-biaxial stretching tests have been carried out for BTR380 steel. On Based of the experimental results, the influence of the stress state on stability of retained austenite is analyzed and an equation of transformation kinetics is developed to predict stress triaxiality-dependence strain-induced transformation. In sheet metal forming, the material undergoes complicated deformation. The prediction of the volume fraction of retained austenite during forming process is essential to estimate the contribution of the TRIP effect to improving formability. To this aim, the volume fraction of retained austenite in the part’s different regions has been calculated using the proposed transformation kinetics equation introduced into finite element method. The calculated results were successfully compared with the experimental data measured in deep drawing experiments.
Evaluation of Friction Behavior of Automotive Steels With Different Test Methods
Authors: Shih Hua-Chu , Shi Ming F.
Published: October 2008

Friction and lubrication play important roles in sheet metal forming operations. They affect the working force required to produce a particular deformation, strain distribution, product surface quality, tool life, etc. These, in turn, control the incident of cracking or tearing failures and dimensional variability due to tooling deflection and workpiece springback. Consequently, careful control of friction and lubrication is essential for a successful metal forming operation. Friction behavior has been found deviate from test method to test method. To understand the true friction behavior of automotive steels in different forming modes, the Stretch forming Simulator (SFS) has been developed and evaluated on seven different zinc coated sheet steels. The results were compared to the test data obtained from a bending under tension (BUT) test and a draw bead simulator (DBS) test. The dome height test and deep draw cup test were also used to verify the test results.
A Computational Response Surface Study of Curved-Surface-Curved-Edge Aluminum Hemming Using Solid-to-Shell Mapping
Authors: Lin Guosong , Hu S. Jack , Koc¸ Muammer , Cai Wayne , Wenner Michael L.
Published: October 2008

Hemming is a manufacturing process of folding a panel onto itself or another sheet. Quality of hemming is characterized by geometry and formability. This paper presents a response surface study of 3D curved-surface-curved-edge hemming of an aluminum alloy, AA6111-T4, using finite element analysis. Solid elements and explicit FE solver are used for simulations of flanging, pre- and final hemming, and shell elements with implicit solver are deployed for springback prediction. A novel procedure called “solid to shell mapping” is developed to bridge the solid elements with the shell elements. Verified to be accurate and efficient, the model is utilized in a Central Composite Design to quantitatively explore the relationships between certain key process variables and the hem dimensional quality and formability. The most significant variables are identified as (i) pre-hemming angle on roll-in/roll-out; (ii) nominal surface curvature on sheet springback; (iii) initial sheet strain and flanging die radius on the maximum hemline surface strain of the produced hem. These results provide insights for process parameter selections in designing and optimizing 3D hems under material formability constraints.
Development of a Novel Process for Manufacturing of Fuel Cell Bipolar Plates: Internal Pressure Assisted Embossing of Micro-Channels With In-Die Mechanical Joining
Authors: Mahabunphachai Sasawat , Koc¸ Muammer , Ni Jun
Published: October 2008

A novel process for manufacturing of fuel cell bipolar plates was developed and described in this paper. This process combines the hydroforming of double thin sheet metal blanks with in-die mechanical joining to enable integrated forming of micro-channels on both surfaces (as anode and cathode) and at the middle (as cooling channels) in a single operation, thus, reducing post process operations, variation in dimensional tolerances, and cost while promises to increase the producibility, product quality, and performance of the fuel cell by ensuring consistent contact resistance characteristics. This paper discussed two experimental investigations that were performed to characterize and evaluate the feasibility of the proposed manufacturing process. The first investigation involved hydroforming of micro-channels with the channels geometry of 0.5 mm in both width and height on thin sheets of stainless steel 304 with a thickness of 0.051 mm. The second investigation focused mainly on the mechanical joining process of thin sheet metal blanks. The effects of different process variables on the bond quality and the mechanisms of the bond formation were studied. The experimental results presented in this paper demonstrated that the proposed manufacturing technique is feasible for making of the fuel cell bipolar plates.
Weld-Bead Movement of Multi-Gauge Tailor-Welded Blank During Drawing Square Cup With Reverse-Convex
Authors: Chen Wei , Du Ruxu , Guo Weigang
Published: October 2008

To decrease the weight of auto panels and reinforce the safety of vehicles, the tailor-welded blank (TWB) has been used widely in the auto panels manufacturing. Basic principles and advantages of TWB are described at first. Then the technologies of numerical simulation modeling for TWB are researched. By means of numerical simulation, the weld-bead movement and formability of TWB with the same mechanical property and multi-gauges are investigated. After analyzing the weld-bead movement in three different drawing depth combinations with same total deformed depth, some conclusions of weld-bead movement are drawn finally. It reveals the relationships between the weld-bead movement and formability of multi-gauge TWB.
Optimizing the Purification of Biofunctionalized Carbon Nanotubes
Authors: Arnold M. S. , Stupp S. I. , Hersam M. C.
Published: October 2008

The utilization of single-walled carbon nanotubes (SWNTs) in large quantities for molecular electronics, optoelectronics, biosensors, and medical applications will require SWNTs of the same physical structure, electronic type, and band gap. Since current methods of synthesis produce mixtures of nanotubes with different physical structures and electrical properties, the development of strategies for the postproduction separation of these one-dimensional materials is highly desirable. In this work, we demonstrate a scalable method for separating SWNTs by diameter using density gradient centrifugation. Of particular interest for biosensing applications is the bulk purification of SWNTs through centrifugation of DNA wrapped SWNTs in aqueous density gradients. The dependence of this process on DNA sequence and length has been determined. In addition, strategies for decreasing the purification time are outlined. Overall, this nondestructive and scalable separation strategy is expected to impact a variety of applications for SWNTs where monodisperse structure and properties are essential.
Effect of Substrate Temperature on Properties of Nano-Scale Functionally Graded Calcium Phosphate Coatings
Authors: Blalock Travis , Bai Xiao , Rabiei Afsaneh
Published: October 2008

The effect of substrate temperature and processing parameters on microstructure and crystallinity of calcium phosphate coatings deposited on heated substrates in an Ion Beam Assisted Deposition (IBAD) system are being studied. The experimental procedures include mechanical testing and film thickness measurements using bonding strength and profilometery. Cross-sectional scanning transmission electron microscopy (STEM) with energy dispersive X-ray spectroscopy (EDX) through the thickness of the film as well as scanning electron microscopy (SEM) with EDX at the top surface of the film was performed to evaluate the microstructure of the film. The coating crystallinity was studied through X-ray diffraction (XRD). The information gained from current analysis on the set temperature coatings will be used to refine the processing techniques of the Functionally Graded Hydroxyapatite (FGHA) coating.
Fabrication of Porous Hydroxyapatite Scaffolds
Authors: Deville S. , Miranda P. , Saiz E. , Tomsia A. P.
Published: October 2008

This work describes two novel techniques for the fabrication of porous hydroxyapatite scaffolds for calcified tissue engineering; robocasting and freeze casting. These techniques allow the fabrication of materials with complex porosity. Both are based on the preparation of concentrated ceramic suspensions with suitable properties for the process. In robocasting, the computer-guided deposition of the suspensions is used to build porous materials with designed three dimensional (3-D) geometries and microstructures. Freeze casting uses ice crystals as a template to form porous lamellar ceramic materials. Preliminary results on the compressive strengths of the materials are also reported.
Powder Injection Molding of Implantable Grade Materials
Authors: Heaney Donald F.
Published: October 2008

In this paper the attributes of powder injection molding that influence the ability to implant a material are evaluated. Specific emphasis is given to technology readiness of stainless steel, titanium and cobalt chromium alloys since these are the most common alloys that are both implantable and metal injection moldable. Issues such as ductility and strengthening are discussed. Also, component size capability of the technology is discussed since prosthetic replacement pushes the upper size limit of the technology and implantable micro devices that require MEMS (MicroElectroMechanical Systems) scale features push the lower limit.
Impact of Helix and Taper on Structural Characteristics of a Nickel-Titanium Endodontic Instrument Through Finite Element Analysis
Authors: He Rui , Goodis Charles J. , Ni Jun
Published: October 2008

The mechanical behavior of a rotary nickel-titanium endodontic instrument was evaluated through finite element models. Essential geometric features of blank taper and variable pitch were modeled and their impact on the mechanical performance of instruments was investigated. Simulation results showed that better bending flexibility and higher torsional stiffness can both be obtained on an instrument with a large helix configuration. The results also illustrated that the finite element method can be used to compute the critical load or deformation for the instrument which prompts the sustainable use of the instrument in clinical practices.
Study on Mechanical Properties of Multi-Scale and Multi-Phase Nanocomposite Ceramic Tool Materials
Authors: Huang C. Z. , Liu H. L. , Wang J. , Liu Z. W.
Published: October 2008

The single nano-scale and multi-phase nanocomposite ceramic materials including Al2O3/Al2O3n/SiCn and Al2O3/Ti(C0.7N0.3)n/SiCn are successfully fabricated. Their mechanical properties are better than those of the single-phase alumina material and conventional alumina matrix materials. The multi-scale and single-phase nanocomposite ceramic tool material Al2O3/SiCμ/SiCn is also successfully fabricated. Its flexural strength and fracture toughness is higher than those of single-scale materials Al2O3/SiCμ and Al2O3/SiCn. The multi-scale and multi-phase nanocomposite ceramic tool material Al2O3/TiCμ/TiNn is finally developed by incorporation and dispersion of micro-scale TiC particle and nano-scale TiN particle in alumina matrix, which can get higher flexural strength and fracture toughness than those of Al2O3/TiC ceramic tool material without nano-scale TiN particle. The coexistent function of nano-scale Al2O3 or Ti(C0.7N0.3), nano-scale SiC and TiN can reduce the sintering temperature and sintering duration time as well as the grain size, and improve the material densification and mechanical properties. The nano-scale SiC grains locating along the grain boundary and inside the micro-scale alumina can form the hybria intergranular-intragranular microstructure which can result in hybria intergranular-transgranular fracture and improve the mechanical properties of the ceramic material. Crack deflection, forking and bridging effects are the main cause for improving the fracture toughness of the materials including Al2O3/Ti(C0.7N0.3)n/SiCn and Al2O3/TiCμ/TiNn.
Three-Dimensional Finite Element Modeling of Drilling Processes
Authors: Marusich T. D. , Usui S. , Aphale R. , Saini N. , Li R. , Shih A. J.
Published: October 2008

The three dimensional (3D) finite element modeling (FEM) and experimental validation of drilling are presented. The Third Wave AdvantEdge machining simulation software is applied for the FEM. It includes fully adaptive unstructured mesh generation, thermo-mechanically coupling, deformable tool-chip-workpiece contact, interfacial heat transfer across the tool-chip boundary, and constitutive models appropriate for process conditions and finite deformation analyses. The workpiece is modeled with a predrilled cone-shape blind hole to enable the early full-engagement of the whole drill point region to reduce the simulation time. Drilling experiments are conducted on the Ti-6Al-4V using a twist drill geometry. The calculated cutting force and torque are compared with the results of experiments with good agreement. Effects of process parameters on the stress and temperature distributions of the drill and workpiece are investigated in detail using the FEM.
A Micromechanical Approach to Determine Flow Stress of Work Materials Experiencing Complex Deformation Histories in Manufacturing Processes
Authors: Anurag S. , Guo Y. B.
Published: October 2008

Work materials experience a broad range of strains, strain rates, and temperatures in many manufacturing processes such as machining, forming, etc. Strain rate has an important effect on the yield and flow stress of work materials, especially metals, since at higher strain rates there is less time for thermally-activated events; consequently, it is equivalent to a lowering of the temperature of the materials. On the other hand, it is also true that, for high strain rate deformations such as metal cutting, adiabatic plastic flow may produce significant temperature changes in the materials. Flow stress is significantly affected by the strain rate history; hence, mechanical behavior may not be fully described in terms of a mechanical equation of state relating the instantaneous stress, strain, strain rate, and temperature. Based on the concept of dislocation mechanics, a micromechanical approach has been explored to determine flow stress at high strain rates by combining athermal stress (the long-range barriers to dislocation motion) and thermal stress (the short-range temperature and strain rate-dependent barriers to dislocation motion). The SHPB (split Hopkinson pressure bar) compression test data of Aluminum 6061-T6 and titanium Ti6Al-4V in literature over a temperature range of 77K–1000K was used for this purpose. Based on the baseline test data, the constitutive model describing the flow stress was developed. The constitutive model was further modified and extended to predict flow stress above the critical temperature. The corresponding model predictions were compared with the experimental data, attaining good agreement.
Evidence of Ductile Tearing Ahead of the Cutting Tool and Modeling the Energy Consumed in Material Separation in Micro-Cutting
Authors: Subbiah Sathyan , Melkote Shreyes , Dabade Udaykumar A. , Banait Nitin , Joshi Suhas S.
Published: October 2008

Orthogonal micro-cutting experiments using quick-stop device are performed on Al2024-T3 and OFHC Copper to study the chip-workpiece interface in a SEM. Evidence of ductile tearing ahead of the tool at cutting speeds of 150 m/min has been found. A numerical finite element model is then developed to study the energy consumed in material separation in micro-cutting. The ductile fracture of Al2024-T3 in a complex stress state ahead of the tool is captured using a damage model. Chip formation is simulated via use of a sacrificial layer and sequential elemental deletion in this layer. Element deletion is enforced when the accumulated damage exceeds a predetermined value. A Johnson-Cook damage model that is load history dependent and with strain-to-fracture dependent on stress, strain-rate, and temperature is used to model the damage. The finite element model is validated using the cutting forces obtained from orthogonal micro-cutting experiments. Simulations are performed over a range of uncut chip thickness values. It is found that at lower uncut chip thickness values, the percentage of energy expended in material separation is higher than at higher uncut chip thicknesses. This work highlights the importance of the energy associated with material separation in the non-linear scaling effect of specific cutting energy in micro-cutting.
Overview of a Distributed Process Planning Approach Targeting Manufacturing Uncertainty
Authors: Wang Lihui , Cai Ningxu , Feng Hsin-Yung
Published: October 2008

This paper presents an overview of our DPP (distributed process planning) approach, covering DPP concept, generic machining process sequencing using enriched machining features, process plan encapsulation in function blocks, and process monitoring enabled by the function blocks. A two-layer structure of Supervisory Planning and Operation Planning is proposed in DPP to separate generic data from machine-specific ones. The supervisory planning is only performed once, in advance, at shop level, whereas the operation planning is carried out at runtime at machine level. This dynamic decision-making is facilitated by a set of resource-driven algorithms embedded in the function blocks. The internal structures of typical function blocks are also introduced in the paper. The DPP approach and algorithms are further verified through a case study before drawing conclusions. It is expected that the new approach can largely enhance the dynamism of fluctuating job shop operations.
A Complexity Code for Manufacturing Systems
Authors: ElMaraghy Hoda A.
Published: October 2008

A new coding system is introduced to classify manufacturing systems and capture the characteristics of the various pieces of equipment and the relationships among them within a manufacturing system, which contribute to their structural, time-independent inherent complexity. The manufacturing Systems Complexity Code (SCC) consists of fields representing equipment, such as machines, buffers and transporters, as well as their layout. Each field contains a string of digits, the value of which depends on the degree of structural, control, programming and operation complexity of theses entities. The developed coding system has many applications including manufacturing systems design, comparison and planning, assessment of their complexity and evaluation of redesign alternatives and trade-offs. The new coding system is described along with its applications and demonstration examples.
Product Oriented Sensitivity Analysis for Multi-Station Compliant Assemblies
Authors: Yue Jianpeng , Camelio Jaime A. , Chin Melida
Published: October 2008

Dimensional variation in assembled products directly affects product performance. To reduce dimensional variation it is necessary that an assembly be robust. A robust assembly is less sensitive to input variation from the product and process components such as incoming parts, subassemblies, fixtures and welding guns. In order to effectively understand the sensitivity of an assembly to input variation, an appropriate set of metrics must be defined. In this paper, three product oriented indices including pattern sensitivity index, component sensitivity index and station sensitivity index are defined. These indices can be utilized to measure the variation influence of a pattern, an individual part and/or component, and components at a particular station to the dimensional quality of a final assembly. Additionally, the relationships among these sensitivity indices are established. Based on these relationships, the ranges of the sensitivity indices are derived. Finally, a case study of a sheet metal assembly is presented and discussed to illustrate the applicability of these metrics.
Stream-of-Variation Modeling I: A Generic 3D Variation Model for Rigid Body Assembly in Single Station Assembly Processes
Authors: Huang Wenzhen , Lin Jijun , Bezdecny Michelle , Kong Zhenyu , Ceglarek Dariusz
Published: October 2008

A stream-of variation analysis (SOVA) model for 3D rigid body assemblies in single station is developed. Both product and process information such as part and fixture locating errors are integrated in the model. The model represents a linear relationship of the variations between Key Product Characteristics (KPCs) and Key Control Characteristics (KCCs). The generic modeling procedure and framework are provided, which involves: (1) an assembly graph (AG) to represent the kinematical constraints among parts and fixtures; (2) a unified method to transform all constraints (mating interface and fixture locators etc.) into a 3-2-1 locating scheme; and (3) a 3D rigid model for variation flow in a single station. The generality of the model is achieved by formulating all these constraints with a unified generalized fixture model. Thus, the new model accommodates various types of assemblies. This model provides a building block for complex multi station assembly model, in which the inter-station interactions are taken into account. The model has been verified by using Monte Carlo (MC) simulation and a standardized industrial software. It provides the basis for variation control through tolerance design analysis, synthesis and diagnosis in manufacturing systems.
Robust Fixture Layout Design for a Product Family Assembled in a Multistage Reconfigurable Line
Authors: Izquierdo Luis E. , Du Hao , Hu S. Jack , Jin Ran , Shi Jianjun , Jee Haeseong
Published: October 2008

Reconfigurable assembly systems enable a family of products to be assembled in a single multistage system by adjusting and reconfigurabling fixtures according to each product. The sharing of fixtures among different products impacts their robustness to fixture variation and process disturbances due to frequent reconfiguration. This paper proposes a methodology to achieve robustness of the fixture layout design through an optimal distribution of the locators for a product family. This objective is accomplished by: (1) the use of a multistage assembly process model for the product family, and (2) minimizing the combined sensitivity of the products to fixture variation. The optimization considers the feasibility of the locator layout by taking into account the constraints imposed by the different products and the processes (assembly sequence, datum scheme and reconfigurable tools workspace). The high dimension design space makes the problem challenging from the optimization point of view. A case study where three products are assembled in four stages is presented. The sensitivity of the optimal layout was benchmarked against the ones obtained using dedicated assembly lines for each product. This comparison proves that the proposed approach does not significantly sacrifice robustness while allowing the assembly of three products in a single reconfigurable line.
Fault Failure Diagnosis for Compliant Assembly Structures Using Statistical Modal Analysis
Authors: Prakash  , Ceglarek D. , Tiwari M. K.
Published: October 2008

This paper develops a new diagnostics methodology for N-2-1 fixtures used in assembly processes with compliant parts. The developed methodology includes: (i) the predetermined CAD-based dimensional variation fault patterns model; (ii) data-based dimensional variation fault model; and (iii) the fault mapping procedure isolating the unknown fault. The CAD-based variation fault pattern model is based on the piece-wise linear bi-partitioning of compliant part into deformed (faulty) and un-deformed regions. Data-based dimensional variation fault models are based on the statistical modal analysis (SMA) which allow to model part deformation with varying number of deformation modes. It is proved in the paper that these independent deformation modes are equivalent to the CAD-based faults models obtained in (i). The fault mapping procedure allows to diagnose the unknown fault by comparing the unknown fault variation pattern obtained from the SMA model with one of the predetermined CAD-based fault patterns. One industrial case study from an automotive roof framing assembly illustrates the proposed method.
Design of a Silicon Micromachined Artifact for Hybrid Dimensional Measurement
Authors: Oliver Andrew D. , Tran Hy D. , Claudet Andre A.
Published: October 2008

We are developing calibration artifacts for mesoscale metrology (especially vision probing) by using silicon bulk micromachining. We evaluate these artifacts on both high accuracy coordinate measuring machines (CMMs) and on typical production vision-based measurement systems. This will improve the accuracy of vision-based measurement equipment used in production. Successful realization of these mesoscale artifacts will enhance both production metrology capabilities and reduce manufacturing costs.
Mesoscale Edge Measurement Using a Confocal Laser Scanning Microscope
Authors: Shilling Meghan , Sung Lipiin , Kurfess Thomas R.
Published: October 2008

In many mesoscale parts (> 100μm) with microscale features (100nm to 100μm), the edge can constitute a large percentage of the total feature size. These edges need to be measured and characterized. Unfortunately, very few tools exist that are able to measure a range of angles with a resolution appropriate to these parts. The measurement methods commonly used to characterize mesoscale parts are designed for nominally planar surfaces and fail when used on a surface with moderate slope. Other tools exist which can adequately capture a sloping surface, however they have characteristics which make them less desirable for edge measurement (contact, destructive, image-output). The confocal laser scanning microscope (CLSM) is a non-contact method which has special properties that allow it to measure sloping surfaces of various materials and finishes. This paper will discuss the CLSM and its ability to measure edges of mesoscale parts.
A Retrofit Open Architecture Parallel Drive CMM System
Authors: Chang David W. , Spence Allan D.
Published: October 2008

Many previously installed Coordinate Measuring Machines (CMMs) are equipped with only a touch trigger probe. Data collection rates are slower than one point per second, and geometric error correction was applied only after the data point was recorded. Most commonly, the CMM structure was a bridge style, supported by air bearings above a granite table, and with the corresponding axis driven from only one side. It is assumed that the low speeds and accelerations do not introduce an uncorrected dynamic error. With the introduction of continues analog (scanning) touch probes and non-contact laser digitizers, CMM system improvements are required to support the new sensors, provide higher data point collection rates, and to manage dynamic error. This paper describes a retrofit open architecture system that provides these improvements. The control computer is based on an Intel Pentium processor, uses the Phar Lap ETS real-time operating system, and is implemented as an embedded system. Setup, including PID tuning, is accomplished remotely using ethernet and an external graphical user interface. Geometric error compensation is applied continuously along the entire motion trajectory. Uncorrected dynamic yaw error was significantly reduced by adding a parallel drive to the opposite side of the CMM bridge, together with a cross-coupling control algorithm that adjusts the reference position signals that are sent to the two parallel motion control loops. The effect is to speed up the lagging side, and slow down the leading side so as to minimize the differential error. Experimental results illustrate the improved dynamic performance of the system.
A Dynamic Sensing-and-Modeling Approach to 3D Point- and Area-Sensor Integration
Authors: Huang Yunbao , Qian Xiaoping
Published: October 2008

The recent advancement of 3D non-contact laser scanners enables fast measurement of parts by generating huge amount of coordinate data for a large surface area in a short time. In contrast, traditional tactile probes in the coordinate measurement machines (CMM) can generate more accurate coordinate data points in a much slower pace. Therefore the combination of laser scanners and touch probes can potentially lead to more accurate, faster and denser measurement. In this paper, we develop a dynamic sensing-and-modeling approach for integrating a tactile point sensor and an area laser scanner to improve the measurement speed and quality. The part is first laser scanned to capture the overall shape of the object. It is then probed via a tactile sensor at positions are dynamically determined to reduce the measurement uncertainty based on a novel next-best-point formulation. Technically, we use the Kalman filter to fuse laser scanned point cloud and tactile points and to incrementally update the surface model based on the dynamically probed points. We solve the next-best-point problem by transforming the B-spline surface’s uncertainty distribution into a higher dimensional uncertainty surface so that the convex hull property of the B-spline surface can be utilized to dramatically reduce the search speed and to guarantee the optimality of the resulting point. Three examples in this paper demonstrate that the dynamic sensing-and-modeling effectively integrates the area laser scanner and the point touch probe and leads to significant amount of measurement time saving (at least several times in all three cases). This dynamic approach’s further benefits include reduced surface uncertainty due to the maximum uncertainty control through the next-best-point sensing and improved surface accuracy in surface reconstruction through the use of Kalman filter to account various sensor noise.