bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionic Liquids as Lubricants in Steel-Steel Contacts
Authors: Doerr N. , Schneider A.
Published: March 2009

A new generation of lubricants based on pure ionic liquids of varying chemical structures has been evaluated in this work. Friction and wear behaviour of these ionic liquids have been investigated by an oscillating friction and wear tester with ball-on-disk geometry. Tribological experiments have been performed at 30, 100 and 170 °C and results have been compared with three reference lubricants. Ionic liquids were found to be partly superior to the reference lubricants. The chosen ionic liquids were assessed being acceptable to excellent regarding long-term thermal stability at 100 °C. At 150 °C a few ionic liquids still fulfilled requirements of negligible degradation characterized by low evaporation rates and constant physico-chemical properties. Furthermore results clearly showed that the choice of anion and cation is decisive for physico-chemical, tribological and long-term behaviour of ionic liquids.
Elastohydrodynamic Lubrication Analysis of a Compliant Journal Bearing Considering Static and Dynamic Deformations of the Surface Coating
Authors: Lahmar M. , Ellagoune S. , Bou-Sai¨d B.
Published: March 2009

In this paper, the effect of both static and dynamic deformations of the bearing-liner on the dynamic performance characteristics, stability and unbalance response of a water-lubricated rubber-lined journal bearing operating under small harmonic vibrations is theoretically investigated. To take into account the dynamic deformations of the bearing-liner, the first order perturbation technique is used to determine the eight dynamic coefficients for a given excitation frequency value. The static and dynamic deformation of the fluid/bearing-liner interface is assumed to be proportional to the steady-state and dynamic fluid-film pressures. It was found that the dynamic properties, stability and unbalance response of the compliant journal bearing are affected by surface coatings from soft materials. It was also shown that when dynamic deformations are considered in the calculations, the dynamic coefficients depend on the excitation frequency, especially for higher values of this parameter. Moreover, the two cross damping coefficients differ from each other, while the classical elastohydrodynamic (EHD) theory predicts them equal, i. e., when the dynamic deformations are ignored.
Triboplasma Generated Under Perfluoropolyether Oil Lubrication
Authors: Nakayama Keiji
Published: March 2009

In order to prove the triboplasma generation in the vicinity of the sliding contact under oil lubrication, two-dimensional images and energy spectra of the photons emitted from the sliding contact has been investigated under perfluoropolyether (PFPE) oil lubrication in a tribosystem of a diamond pin sliding on a sapphire disk in the atmospheric ambient air pressure and in vacuum. Two-dimensional image of the tribophoton clearly showed the plasma generation under PFPE oil lubrication. The UV photon energy spectrum and disappearance of the UV photon image in vacuum showed that the plasma is generated by air discharge even under oil lubrication.
An Elastic Problem Associated With Articular Biocontacts
Authors: Diaconescu E. N. , Glovnea M. L. , Horatau M. G.
Published: March 2009

The cartilage has a complex mechanical behavior. One of possible cartilage models is that viscoelastic. Usually, articular pressure is found by FEM. This paper advances a simple general analytical-numerical model for the contact between a rigid punch and a finite thickness elastic layer bonded to a rigid substrate. This is applied for paraboloidal punches which generate a combined pressure, paraboloidal and elliptical. The elastic solution is the starting element in viscoelastic analysis.
Effect of Loading Path on Sliding Contact Status for Elastic and Plastic Media
Authors: Zhang Chao , Fu Yuansong , Tao Mongzhang , Bao Chenyui
Published: March 2009

Catastrophic surface failures encountered in many engineering components are usually associated with contact status. For plastic medium contact status depends on the history of plastic deformation, loading path. Although many papers have contributed to contact analyses [1, 2, 3], but in most papers, effects of loading path on contact status for plastic medium have not been included yet. The aim of this study is to illustrate how loading path influences contact status.
Diametral Clearance Effect on Friction and Wear Characteristics of a Metal-on-Metal Total Hip Arthroplasty
Authors: Shen Ming , Grundmann Birgit , Liebentritt Gernot
Published: March 2009

Tribological performance of a metal-on-metal total hip arthroplasty was evaluated as a function of the diametral clearance between the femoral head and acetabular cup. Frictional torque results, measured by a pendulum apparatus, suggested that a threshold clearance existed. Below the threshold clearance, frictional torque increased nearly linearly as the clearance decreased. Beyond the threshold, the clearance effect was minimal. The wear results, measured using a hip simulator, showed that a running-in wear was present in the first million cycles. The subsequent steady-state wear rate was very low in all tested clearances. The highest running-in wear was associated with the largest clearance. These results demonstrated the usefulness of combining a pendulum test and a simulator wear test to fully characterize the clearance effect.
Behaviour of Boundary Lubricating Additives on DLC Coatings
Authors: Topolovec-Miklozic Ksenija , Forbus T. Reg , Lockwood Frances , Spikes Hugh
Published: March 2009

The friction properties of a range of boundary lubricating additives in DLC-DLC sliding-rolling, lubricated contact have been investigated. Two types of DLC have been studied, one hydrogenated diamond-like and the other a non-hydrogenated graphitic type. The graphitic-type DLC coating gave initially very low boundary friction with additive-free base oil but after a few minutes of rubbing in thin film conditions this rose to the higher value produced immediately by the diamond-like DLC. With the graphitic-type DLC, ZDDP formed a thin patchy film while MoDTC produced a marked reduction of friction. Lateral force microscopy showed that the latter resulted from the formation of low friction material on the asperity peaks. Some organic friction modifiers preserved the low friction of g-DLC during prolonged rubbing. MoDTC and ZDDP were also effective in reducing friction on diamond-like DLC.
Using a Lattice-Based Cellular Automata Approach to Model the Load Carrying Capacity of Granular Flows
Authors: Jasti Venkata K. , Higgs C. Fred
Published: March 2009

Flows of solid granular particles are proposed as an alternate lubrication mechanism to conventional liquid lubrication in sliding contacts, because of their ability to carry loads and to accommodate surface velocities. Alternate lubrication is becoming necessary in extreme temperature environments where liquid lubricants fail and in micro/nanoscale environments were they promote stiction. However understanding granular behavior has been a challenge because of their ability to behave as solids, liquids and gases with varying circumstances. Cellular automata (CA), a deterministic rule based mathematics approach, has been successful in modeling some complex aspects of granular behavior. Our previous work successfully modeled granular shear with CA model. This work introduces a more versatile and novel cellular automata framework which combines the computational efficiency of CA with the power of particle dynamics to capture collision events. In the past, the load carrying capacity of granular flows was demonstrated in the experiments conducted by Yu and Tichy [2] and later, local flow properties were modeled using the granular kinetic lubrication continuum modeling approach. These results were used as a benchmark for determining the effectiveness of the current CA model.
An Asperity-Based Fractional Coverage Model for Solid Lubricant Film Transfer on a 3D Surface
Authors: Wornyoh E. Y. A. , Higgs C. F.
Published: March 2009

Topography data was obtained from an aluminum thin film deposited unto a substrate. Using this 20 μm × 20 μm specimen, an asperity-based fractional coverage model was used to predict (1) the friction coefficient at a pad/disk interface (2) the thickness of deposited lubricant film and (3) the wear factor for a compacted lubricant pellet in sliding contact. The fractional coverage varies with time and is a useful modeling parameter for quantifying the amount of third body film covering the disk asperities. The model was based on a previous 1-D control volume fractional coverage model which was used to glean tribological parameters including friction coefficient and wear factor. In this model, the wear rate of the pellet, pad friction coefficient, and lubricant thickness can be determined as a function of the pellet load, slider pad load, disk speed, and material properties. Steady-state results from the model adequately predict the self-repairing and self-replenishing nature of powder lubrication as a function of topography.
Simulating the Air Bearing Flying Height in a Humid Environment
Authors: Zhang Shuyu , Strom Brian , Lee Sungchang , Tyndall George
Published: March 2009

For a hard disk drive operating in a humid environment, the water vapor in the slider’s air bearing is typically compressed beyond its saturation vapor pressure, causing the vapor to condense. Consequently, the air bearing pressure decreases and the slider’s flying attitude adjusts to balance the forces from the suspension. A method for calculating this air bearing response to humid air is presented. Using one particular air bearing design as an example, several test cases are analyzed to illustrate the air bearing response for various temperatures and humidity levels. The calculated flying heights agree with those measured in commercial hard disk drives.
Effects of Molecularly Thin Liquid Lubricant Film Materials on Slider Hysteresis Instability in Hard Disk Drives
Authors: Tagawa Norio , Tanaka Daisuke , Mori Atsunobu
Published: March 2009

In this study, the difference in the touchdown and takeoff pressures was monitored by using three types of lubricant materials, namely, Zdol2000, Ztetraol2000 and A20H2000 by using the pump down pressure test. The results indicated that the touchdown pressures depended on the lubricant materials; it was greatest for Ztetraol2000 and smallest for A20H2000. The takeoff pressure was greater for a lubricant with lower mobility. Considering these experimental results, it was suggested that the variation in the touchdown pressure is due to a variation in the intermolecular forces, taking into account the lubricant pickup by a slider. Further, it was suggested that the variation in the takeoff pressure is caused by a variation in the friction forces between the slider and disk surface.
Experimental Visualization of Air Bearing Mode Shapes
Authors: Himes Adam , Roy Mallika
Published: March 2009

Air bearing vibrations at nanometer clearance levels are a limiting factor for reduction of head-media spacing. This paper presents a method for measuring both natural frequency and mode shape of the entire head gimbal assembly at frequencies typically associated with air bearing vibration. An acoustic emission sensor is used to provide a reference signal to a scanning laser Doppler vibrometer system. The good correlation between the acoustic signal and structural motion enables mode shapes to be constructed and animated. The motion of the gimbal and load beam during contact-induced air bearing vibration is found to be significant. We use this experimental method to show differences in system response depending on the air bearing design for thermally actuated heads.
Deformation Characteristics of the Ultrathin Liquid Film Surface Considering the Effects of Polar Endgroups
Authors: Fukui Shigehisa , Shimizu Soichi , Yamane Kiyomi , Matsuoka Hiroshige
Published: March 2009

To examine deformations of ultra-thin but continuum liquid film, the long wave theory was employed. The long wave theory uses the time-evolution equation for the shape and deformation of the thin liquid film and includes the surface tensions and surface forces such as the van der Waals (vdW) force. By numerically solving the time-dependent long wave equation, deformations of the ultra-thin lubricant film considering the vdW pressure with initial/boundary configurations of the liquid surfaces were obtained.
Elastic Contact Model Accounting for Both Asperity and Substrate Compliance With Application to Patterned Media
Authors: Yeo Chang-Dong , Polycarpou Andreas A.
Published: March 2009

An improved elastic contact stiffness model for a single asperity system is proposed to account for the effects of both bulk substrate and asperity deformations between two contacting surfaces. Depending upon the applied load, as well as the geometrical and physical properties of the asperity and bulk material, the bulk substrate can have a considerable contribution to the overall contact stiffness. Finite element analysis is performed to verify the proposed analytical model. The single asperity model is extended to rough surfaces in contact. The contact stiffness values from the proposed model are compared to those from the GW model. The proposed contact model can be directly relevant to analyze the contact behavior of modern patterned media.
Fabrication of Biomimetic Scaffolds With Well-Defined Pore Geometry by Fused Deposition Modeling
Authors: Jabbari Esmaiel , Rocheleau David N. , Xu Weijie , He Xuezhong
Published: March 2009

It is well established that the pore size and distribution affect the rate of cell migration and the extent of extracellular matrix formation. The objective of this work was to develop a process for fabrication of biodegradable and shape-specific polymeric scaffolds with well-defined pore geometry, functionalized with covalently attached bioactive peptides, for applications in tissue regeneration. We have used the Fused Deposition Modeling (FDM) RP technology to fabricate degradable and functional scaffolds with well-defined pore geometry. Computer aided design (CAD) using SolidWorks was used to create models of the cubic orthogonal geometry. The models were used to create the machine codes necessary to build the scaffolds with FDM with wax as the build material. A novel biodegradable in-situ crosslinkable macromer, poly(lactide-co-glycolide fumarate) or PLGF, mixed with reactive functional peptides was infused in the scaffold and allowed to crosslink. The scaffold was then immersed in a hydrocarbon solvent to remove the wax, leaving just the PLGF behind as the support material dissolved. The pore morphology of the PLGF scaffold was imaged with micro-computed tomography and scanning electron microscopy. Cellular function in the PLFG scaffolds with well-defined pore geometry was studied with bone marrow stromal cells isolated from rats. Results demonstrate that the scaffolds support homogeneous formation of mineralized tissue.
The State-of-the-Art in Nano-Turning
Authors: Schmittdiel Michael C. , Haber Guerra Rodolfo E. , Escribano A´ngel , Escribano Javier
Published: March 2009

The state-of-the-art in nano-turning is evolving rapidly due to the economic and application benefits that nano-scale engineering creates. This paper describes the state of the art in nano-turning with a focus on single point diamond tools (SPDT) and integrated sensory systems. Research in this area has thus far lagged behind other nano-scale research efforts in the chemical and biological sciences. Discussion of the fundamentals of nano-scale turning is presented along with the state-of-the-art in sensor systems. Surface finish is a critical performance characteristic for nano-turned parts, which is detailed in terms of the impact of machining parameters, tool geometry, and material anisotropy. Ongoing research into computer modeling of the cutting mechanics at the nano-scale is presented. Sensors and automation systems for nano-turning are discussed with a focus on active control and in-process adjustments. Finally, recommendations are given for the future of nano-turning and nano-scale machining in general.
Laser Heating and Thermally Enhanced Deformation of Silicon
Authors: Dong Lei , Patten John A.
Published: March 2009

A novel hybrid system, using a fiber coupled infrared (IR) laser and through the tool delivery of the beam energy, has been developed for micro laser assisted machining (μ-LAM) of semiconductors and ceramics. This system uses diamond tooling and the laser energy is delivered to the work piece though the cutting tool. The diamond cutting tool and IR fiber laser are directly coupled and integrated into a single package. Of particular significance is that the combination of parameters, i.e. laser wavelength selected for specific materials (such as silicon and silicon carbide), permits heating and thermally softening the chip formation zone, while leaving the balance of the work piece unaffected (thermally). The system is being developed for nano-micro level machining processes, such as practiced with ductile regime machining of semiconductors and ceramics in the field of precision engineering.
Development of a Highly Miniaturized PQT-Sensor for Monitoring and Diagnosing of Pneumatic Systems
Authors: Sosna Christoph , Buchner Rainer , Lang Walter , Benecke Wolfgang , Boehm Christian , Binder Josef
Published: March 2009

In this paper a feasibility study of a micromachined PQT-sensor for measurement of pressure (P), flow rate (Q), and temperature (T) for diagnostic applications in pneumatic systems is presented. As a low cost device this innovative PQT-sensor has to fulfill different kinds of criteria such as wide measuring range, fast response time, high resolution and high accuracy for diagnosing the health status of a pneumatic system. By using micro electro mechanical systems (MEMS) technologies small high-performance sensors were fabricated which fulfill all these criteria. At first, principles will be described that have been chosen for measurement of pressure, flow and temperature that will be used for the PQT-sensor. A design proposal for the sensor will be presented and verified with analytical calculations to show its applicability.
Manufacture of Production Quality Injection Mold Tools Using SLS and HSM
Authors: Taylor C. M. , Ilyas I. P. , Dalgarno K. W. , Gosden J.
Published: March 2009

The use of a rapid manufacturing method to create injection mould tools offers the opportunity to create conformal cooling channels in the core/cavity inserts. Conformal cooling channels allow for better thermal management of the injection mold tool through the cycle, with the potential to reduce cycle times and/or improve product quality. However, currently available rapid manufacturing methods do not deliver the levels of accuracy and surface finish required to meet typical injection mould tool specifications. This paper reports on a hybrid approach to developing the mold inserts, which uses the rapid manufacturing process of indirect selective laser sintering (SLS), using the 3D Systems LaserForm process, to create a near net shape insert with conformal cooling channels, and then produces the net shape inserts by using high speed machining (HSM) as a finishing process. This approach to injection mold tool development has been tested through three industrial case studies. In each study existing injection mold inserts have been redesigned to give a conformally cooled tool. These have then been manufactured to near net shape in a steel/bronze metal composite through indirect SLS, and finished to production specification using HSM, EDM and polishing. Within the case studies the main aim has been to improve productivity, and the inserts have been evaluated in industrial trials in order to assess their performance in terms of cycle time, energy usage, durability and quality. The results show that significant productivity improvements and energy use reductions in injection molding are possible through the implementation of conformal cooling. Consistency of part quality and material durability have been assessed through extended molding trials, and in some cases there is a clear economic benefit to using the inserts. However, the importance of up front modelling to understand the impact of conformal cooling channels, the need for careful planning in manufacture to ensure that the required internal geometry is created, and the need for multiple representations of the required geometry to inform the different stages of the manufacture process are highlighted.
Surface Replication and Structural Development in Micromolding for Micro/Nanocomposites
Authors: Ito H. , Kazama K. , Kikutani T.
Published: March 2009

Micromolding with micro-scale surface features of hexagonal boron nitride (h-BN) / polypropylene (PP) composites with different h-BN component was performed to improve molded parts’ heat diffusivity and processability. Effects of h-BN content and process parameters on processability, higher-order structure, and microscale surface patterns of molded parts were analyzed using SEM, WAXD, SPM, and confocal laser scanning microscopy. The replication ratio of the microscale surface pattern and flow length of composite molded parts was improved by compounding the h-BN filler. The replication ratio of the microscale surface pattern near the flow end became greater than 1.0 because of deformation of surface patterns during de-molding. The replication ratio and shape of surface patterns of molded parts were improved with the increase of the h-BN component. The h-BN platelet oriented inside surface micro-features; skin-shear-core structures were well observed in the molded parts.
Rapid Reconfiguration and Part Repositioning With an Intelligent Fixturing System
Authors: Papastathis Thomas , Ryll Marco , Ratchev Svetan M.
Published: March 2009

This paper presents two methodologies for rapid self-reconfiguration and precise part location for an intelligent fixturing system. After introducing the proposed fixture design consisting of movable actuators and integrated sensors, the methodology for the automated reconfiguration of the system is presented. This is an object-oriented approach ensuring that the fixture can work with various setups without the need of altering the control software. Finally, a part repositioning methodology is described that takes part geometrical errors into consideration.
Robust Direct-Write Dispensing Tool and Solutions for Micro/Meso-Scale Manufacturing and Packaging
Authors: Li B. , Clark P. A. , Church K. H.
Published: March 2009

The development of functional and reliable miniaturized devices including Micro Electro Mechanical Systems (MEMS) has stressed the manufacturing and packaging processes. The traditional micro fabrication techniques, such as lithography, physical vapor deposition (PVD), chemical vapor deposition (CVD) and etching, are layer-by-layer processes and mostly suitable for thin-filmed devices. LIGA (an acronym from German words for lithography, electroplating, and molding) is a newly developed process for thick metallic devices; however, it involves electroplating process and high quality molds, which are hard to move after electroforming. In all the processes mentioned above, masks and photoresist processing are inevitable, which complicates the whole process and increases the processing time and the total cost. It is also well known that packaging is another barrier for the advancement of MEMS. MEMS packaging, which is required to provide mechanical support, environmental protection and electrical connection to other system components, is much more complicated as compared to electronic components due to the moving structures, fluids or chemicals involved. It is the most expensive process in micromachining. Therefore, enabling tools and technologies are greatly needed for the fabrication and packaging of complicated devices and highly integrated micro assemblies. In this paper, we will present novel direct-print dispensing techniques and robust tools for 21st century manufacturing and packaging. Comparing to other dispensing technologies such as time-pressure needle dispensing, screen printing, pin transfer and jetting, nScrypt’s pumping techniques can dispense materials with precise volume control for 10’s of Pico liter resolution, accurate placement or alignment within a few microns, conformably print on exaggerated surfaces of 10’s of centimeters, and are extremely flexible with materials and patterns. The dispensing tip (nozzle) is optimized to reduce the pressure drop as compared to the traditional tubing needles. Comparing to traditional micro fabrication technologies, our direct-print dispensing technology is maskless and thus a cost effective process. While micro-dispensing is a solution based approach, it has the advantage of not being a wet process such as wet etching or electroplating. Direct-print dispensing of micro lines, micro dots, and three-dimensional structures will be presented. The technology has a wide range of applications in the manufacturing and packaging of micro/meso-scale devices and bio structures.
Research on Peeling Properties of Galvannealed Coatings
Authors: Xu Chun , Li Shuhui
Published: March 2009

Galvannealed coatings are so quite hard and brittle that they are difficult to peel off from their substrates by conventional peeling tests. A special test to tear galvannealed coatings, based on asymmetry 90°peel test, is experimentally investigated. Rectangle shapes of specimens are asked in the test. Specimens have 100mm in length and 25mm in width. They were pulled apart in Zwick instron testing machine at 5mm/min. peeling stress of galvannealed coatings was measured in this test. Morphology of cross-section sample was observed by SEM. The difference of microstructure phases on sample’s surface before and after peel test was analyzed by XRD. Galvannealed coatings are consisted of δ-, Γ- and Γ1 -phases. Gamma (Γ + Γ1) phases are located in interface of coating and substrate. Delta phase is next to gamma phase. After the coatings are peeled off, there are only gamma phase on the fractured surfaces of substrate side. The results show the coatings’ fracture occurs along interface layer of coating and substrate.
Full Field Displacement Measurements of AFM Cantilevers During Loading
Authors: Kumanchik Lee , Schmitz Tony , Pratt Jon , Ziegert John
Published: March 2009

Research collaboration between the University of Florida and National Institute of Standards and Technology is focused on the development of a reference standard for atomic force microscope (AFM) cantilever stiffness calibration. The end goal is production of flexure-based artifacts that exhibit low fabrication expense, stiffness adjustability by design, insensitivity to load application point, mechanical robustness, and good reproducibility. Experimental determination of AFM cantilever spring constants is important because the measured forces are inferred from the cantilever displacement and a linear relationship between force and displacement. As a first step in this study, we have constructed a test setup that enables us to: 1) monitor AFM cantilever behavior during loading; and 2) record the shape of the cantilever under test during contact to better understand boundary conditions. The fundamental metrology tool employed by the test setup is a three-dimensional optical profiler, or scanning white light interferometer. By locating the cantilever (and test surface) within the measurement area of the profiler, we are able to record “snapshots” of the cantilever shape under various loading conditions. Given the deflected shape, we can make comparisons between the actual shape and the profile that would be obtained by ideal (fixed-free) boundary conditions. Results for cantilevers with various stiffness values (spanning four orders of magnitude) are presented and comparisons with ideal deflected shapes are provided.
Cutting Edge Radius Effects on Diamond Coated Cutting Tools: From Deposition to Machining
Authors: Hu Jianwen , Chou Y. Kevin , Thompson Raymond G.
Published: March 2009

Diamond coatings have been increasingly extended to cutting tool applications for machining advanced materials such high-silicon aluminum alloys. Diamond coating tool behaviors are interrelatedly influenced by both the coating and subsequent machining, and yet the tool edge geometry strongly impacts the stress fields around the cutting edge during each process. To effectively use diamond coating tools, it is necessary to understand the stress modifications around the tool edge due to the deposition and during machining. In this study, finite element modeling was applied to simulate deposition stresses from coating and stress modifications due to subsequent machining affected by the edge radius. The results are summarized as follows. For deposition stresses, edge sharpness causes significant stress concentrations around the edge radius area. In machining, the thrust forces increase drastically with the increased edge radius, while the cutting forces increase only marginally. During machining, the thermal load, which causes stress reversal conditions, is more dominant to stress evolutions than the mechanical load. For all cutting conditions tested, increasing the edge radius results in increased stress reversal. The edge radius effects on stress reversal are more prominent at small uncut chip thickness and high speed, which is due to more pronounced size effects and high cutting temperatures. Though large edge radii reduce the deposition stresses, the reduction seems insufficient to compensate the added machining loads within the range of edge radii studied.
Nonlinear Feed Effect in Machining Chatter Analysis
Authors: Landers Robert G. , Ulsoy A. Galip
Published: March 2009

Regenerative chatter is a major limitation to the productivity and quality of machining operations due to the excessive rate of tool wear and scrap parts which are produced. Machining chatter analysis techniques examine the stability of the closed-loop model (force process and machine tool-part structure) of the machining operation to determine the stable process parameter space. Almost all chatter analysis techniques assume a linear force process and develop stability lobe diagrams (i.e., plots of the stable and unstable regions in the process parameter space) for a specific feed. It is well known that machining force processes inherently contain a nonlinear relationship between the force and the feed, which is typically described by a power law. In this paper, the linear chatter analysis technique developed by Budak and Altintas is extended to account for the force-feed nonlinearity. The analysis provides insight into the effect feed has on chatter in machining operations. Also, by directly including the force-feed nonlinearity in the chatter analysis, the need to calibrate the force process model at different feeds is alleviated. The analysis is developed for turning and face milling operations and is validated via time domain simulations for both operations and by experiments for a face milling operation. The analyses show excellent agreement with both the time domain simulations and the experiments. Further, several end milling experiments were conducted that illustrate the nonlinear effect feed has on chatter in machining operations.
Production of Micro-Molding Tooling by Hot Embossing
Authors: Dirckx Matthew , Mazzeo Aaron D. , Hardt David E.
Published: March 2009

Tooling is especially critical for micro-molding of polymers because the tool defines the geometry of the finished part. Various tool materials and processes have been demonstrated, including etched silicon, machined or electroformed metal, and molded polymers. Adhesion of the part to the tool and differential thermal contraction are frequently cited problems related to micro-molding tooling. Brittle silicon tools are particularly vulnerable to failure during demolding because of adhesion and thermal stress. The current work demonstrates the production of micro-molding tools by hot embossing of thermoplastics. Polymer materials for working tools are selected on the basis of high heat deflection temperature and high interfacial tension with the polymer being embossed. The high thermal resistance of the working tool material enables its use in hot embossing of materials with lower glass transition temperature such as polymethyl-methacrylate and cyclo-olefin-polymer, as well as other micro-molding processes. The high interfacial tension reduces adhesion between the master mold and the final part, reducing loads on the tools and facilitating demolding. Embossing parameters for a variety of working tool materials, as well as replication fidelity of the working tools and parts and tool-part adhesion are explored. Polymer working tools produced by hot embossing show great promise for manufacturing polymer micro-devices.
Empirical Dynamic Modeling of Friction Stir Welding Processes
Authors: Zhao Xin , Kalya Prabhanjana , Landers Robert G. , Krishnamurthy K.
Published: March 2009

Current Friction Stir Welding (FSW) process modeling research is concerned with the detailed analysis of local effects such as material flow, heat generation, etc. These detailed thermo-mechanical models are typically solved using finite element or finite difference schemes and require substantial computational effort to determine temperature, forces, etc. at a single point in time. Dynamic models describing the total forces acting on the tool throughout the entire welding process are required for the design of feedback control strategies and improved process planning and analysis. In this paper, empirical models relating the process parameters (i.e., plunge depth, traverse rate, and rotation speed) to the process variables (i.e., axial, traverse, and lateral forces) are developed to understand their dynamic relationship. First, the steady-state relationship between the process parameters and variables is constructed, and the relative importance of each process parameter on each process variable is determined. Next, the dynamic process response characteristics are determined using Recursive Least-Squares. The results indicate that the steady-state relationship between the process parameters and variables is well characterized by a nonlinear power relationship, and the dynamic responses are well characterized by low-order linear equations. Experiments are conducted that validate the developed FSW dynamic models.
Estimation of Fatigue Strength of Fabricated Component
Authors: Ounpanich Duangporn , Mutoh Yoshiharu , Yoshii Kenji
Published: March 2009

This paper deals with the fatigue performance of fabricated component. The plain fatigue and fatigue crack growth tests were performed. The rectangular bar specimens sectioned from the fabricated components after rolling, forming and cold spinning processes were prepared. Four-point bend fatigue tests of the specimens with as-fabricated surfaces were carried out at a stress ratio of 0.1 and a frequency of 20 Hz with a sinusoidal waveform. The crack growth behavior of specimens at various stages of fabricating process was also investigated. The fatigue test results indicated that surface morphology and surface defect induced by each stage of fabricating process strongly degraded the fatigue strength. The limited influence of fabricating process on crack growth behavior was noticed only in the threshold region. Fatigue strength and fatigue life were estimated based on fracture mechanics approach using the fatigue crack growth curve obtained and the surface defect depth observed on the fabricated surface. The estimated fatigue strength and the experimental results were in good agreement.
Close-Die Embossing of Multichannel Waveguides
Authors: Nagarajan Pratapkumar , Yao Donggang , Ellis Thomas S. , Azadegan Reza
Published: March 2009

A combined punching and embossing process was developed for fabrication of 3-D multichannel waveguides. The close-die setup overcomes the lateral flow problem experienced by the standard hot embossing process, thereby allowing buildup of embossing pressure and replication of 3-D features. The embossing tool for this purpose includes a punching head and the to-be-replicated features in the socket behind the punching head. During the process, the embossing tool first punches out a billet from a large blank and then embosses this billet in the socket. The combined operation allows for accurate blanking and provides a close-die process for embossing pressure buildup. ABS and PMMA were chosen as two polymers for waveguide embossing. In both cases, cycle times around 7 minutes resulted. While ejection problems were experienced by PMMA, a relatively brittle polymer, 4-channel waveguides with crispy edges and accurate dimensions were successfully fabricated using ABS, the tougher polymer.
A RSS Method for Estimating Hole Dimension Error in a Batch Micro-EDM Process
Authors: Wang J. J. , Hou J. L. , Hsu F. C. , Liao Y. Y. , Liang Steven
Published: March 2009

In an attempt to estimate the spread of errors in an EDM hole making process, a new Root-Sum-Square (RSS) method is proposed to combine the dimensional spread of a batch of electrodes with the over-cut variation in the micro-EDM process. Two sources of errors are commonly associated with an EDM process and contribute to the dimensional accuracy of the EDMed hole: the dimensional variation of the electrodes and the process over-cut error and its variation. Especially in a micro-EDM process, it is often difficult and time-consuming to measure the geometric dimension and tolerance of either a batch of electrodes or holes of small dimensions. By quantitatively establishing the relationship among the spreads in geometric errors of the electrodes and holes and the process capability, this new method provides an analytical tool in predicting hole error and allows allocating the tolerance budget when selecting the appropriate electrode making process, the EDM machine and process parameters. A series of experiments are carried out to establish and verify the RSS method. Given a set of EDM parameters and a batch of electrodes, the process error in the average over-cut and its spread is first obtained by the RSS method. The process error is then verified by separate experiments with electrodes of fixed dimension under the same EDM conditions. The validity of RSS method is further confirmed by experiments under different electrode dimensions. The RSS method is shown to well represent the contribution of both electrode and process errors to the statistical characteristics of the hole dimension. The establishment of this statistical error model should facilitate the design and control of hole quality by balancing the requirements for the dimensional accuracy of the electrodes and the process accuracy in a batch production environment.
Fabrication of 3D Cell Supporting Structures With Multi-Materials Using the Bio-Printer
Authors: Nishiyama Yuichi , Nakamura Makoto , Henmi Chizuka , Yamaguchi Kumiko , Mochizuki Shuichi , Nakagawa Hidemoto , Takiura Koki
Published: March 2009

We produced three-dimensional (3-D) cell supporting structures for use in engineering regenerative living tissue. The structures were formed by alginate gel, a type of hydro-gel, and our originally developed printer, termed a 3-D bio-printer. A droplet ejected from an inkjet printer nozzle has the same size as several cells. Thus, we considered that such a printer nozzle would be able to eject cultured living cells, along with growth factor, protein, and other materials. If a 3-D gel structure could be formed with such cells, and the materials and cells self-assembled, a variety of living tissues could be obtained. In this report, our 3-D bio-printer and the method of fabrication of multiple material gel structures is presented. Our 3-D bio-printer has a printing mechanism that operates in 3 directions with a positioning resolution of 0.5 micrometers, which is adequate for precise positioning of the ejected cells. Further, a piezoelectric inkjet nozzle head that does not became heated during operation is used and cells can be ejected without heating. The head has 4 nozzles and is able to eject 4 different kinds of materials simultaneously. We used a sodium alginate solution and ejected it from the inkjet nozzle into a calcium chloride solution as a substrate, thus alginate gel beads were obtained. Several types of gel structures could be constructed by distributing the beads precisely and the resolution of the gel structures was as small as the size of an individual bead, about 10–60 μm in diameter. By continuous operation of the inkjet nozzle, gel lines were able to be formed. The substrate was a 10% calcium chloride solution on a slide glass and the ejected-droplets contained a 0.8% sodium alginate solution. In addition, gel sheets were formed by parallel gel lines. In that case, a 10% calcium chloride solution was also used as the substrate. It is possible that such 3-D gel sheet structures could be constructed by lamination in a high viscosity substrate. We also formed gel rings, which were stacked and allowed to sink into the substrate, thus obtaining gel tubes. By utilizing gel tubes with inner and outer walls formed using different types of gels with vascular endothelial cells and smooth muscle cells, blood vessel structures could be fabricated with the present system.
Laser Micro-Machining of Spherical and Elliptical 3-D Objects Using Hole Area Modulation Method
Authors: Lee Wen-Hui , O¨zel Tug˘rul
Published: March 2009

Laser micromachining has the capability to fabricate very small and basic 2.5-D geometric features on a range of materials in the form of laser ablation or irradiation. Short pulsed lasers that can achieve wide range of wavelengths in the form of harmonics of infrared laser beam at 1064 nm wavelength have been a very effective micro-machining tool used for hole drilling, cutting, scribing, trimming and marking. A review of laser processing of materials is given in this paper. Direct laser ablation can be performed by controlling laser beam properties such as laser energy, intensity, pulse duration and wavelength in micro-machining 3-D geometric features. However, this method requires additional capabilities for a typical laser beam generating and delivery system. When the laser beam properties cannot be altered, Hole Area Modulation (HAM) method becomes alternative solution by controlling the density of the holes and the step size in a mask to improve the accuracy of the 3-D geometric feature. In this paper, we perform modeling, planning and simulation of laser micromachining with hole area modulation method to produce spherical and elliptical objects 3-D geometrical features that are typical for aspheric and or refractive micro-lenses. A computational methodology is developed to design a mask with varying density and diameter of the holes. The masks are created using micro-drilling and utilized in laser micromachining of 3-D objects on polycarbonate polymer substrates.
Adaptive Digital Control Based on Reduced-Order Parameter Identification and Disturbance Observer for Linear Motor
Authors: Chen Chin Sheng , Lin Shih Chieh , Wang Shih Ming , Hong Yong Ming
Published: March 2009

This paper proposes a high-efficiency digital servo driver that realizes an auto-tuning feedback and feedforward controller design using on-line parameters identification. Firstly, the variant inertia constant, damping constant and the disturbed load torque of the linear motor are estimated by a reduced-order recursive least square (RLS) estimator, which is composed of a reduced-order RLS estimator and a disturbance torque compensator (DOC). Because one plant parameter is almost constant in high sampling rate digital control for linear motors, the reduced-order RLS estimator will only calculate one plant parameter for efficiency purposes. Furthermore, the auto-tuning algorithm for the feedback and feedforward controller is realized according to the estimated parameters to match the tracking specification. The proposed auto-tuning digital servo controller is evaluated and compared experimentally with a traditional controller on a microcomputer-controlled linear motor positioning system. The experimental results show that this auto-tuning digital servo system remarkably reduces the tracking error of a controlled machine.
Metallurgical Phases Distribution Detection Through Image Analysis for Simulation of Laser Hardening of Carbon Steels
Authors: Tani Giovanni , Ascari Alessandro , Orazi Leonardo
Published: March 2009

This paper deals with an original method for detecting the topological distribution of the ferrite and pearlite phases concerning a medium carbon hypo-eutectoid steel. Starting from a digital metallographic image a computation algorithm is applied to the pixel grid and a text array is generated reproducing the actual position of every phase into the bulk of the material. This result could be very useful to technological processes FEM simulators, where a good knowledge of the starting material is a required condition in order to obtain reliable and accurate results.
3-D Transient Simulation Model for Laser Micromilling Processes
Authors: Tani Giovanni , Orazi Leonardo , Fortunato Alessandro , Cuccolini Gabriele
Published: March 2009

In this paper a laser milling simulator package is shown and discussed. The software system has been developed to simulate the micromanufacturing process using solid state lasers with pulse width in the range of 10–100 ns, but it can simulate every spatial and temporal distribution of the laser beam, so it is well suited to simulate both continuous and pulsed emission and every kind of laser spot distribution and trajectory. The system can simulate the effect of the laser beam on the workpiece, keeping into account the surface conditions, the evolution of the work-piece temperature field, the phase changes in the material and, at the end, the ablation rate. Particular attention has been focused in considering the influence of the plasma plume. Modeling and simulating the plasma plume creation and expansion is a very hard task, in the proposed package a simplified model is developed avoiding the fluid dynamic effects. In this work two empirical tuning parameters are considered: the first one is a global dispersion factor that keep in account the fraction of energy lost in the environment by the plume; the second one is a spreading factor that permits to model the irradiated energy of the laser beam hitting the workpiece and due to the plasma plume. The direct and coupled effects of these two parameters are evaluated and discussed.