bluuebunny/crossref_metadata_2025 huggingface dataset:
The Magnetohydrodynamic (MHD) Effects on the Performance of a Hydrostatic Thrust Bearing With Hybrid Raleigh Step
Authors: Horvat Frank E. , Braun Minel J.
Published: April 2011

This paper studies the numerical development of flow patterns and pressure profiles inside a hybrid Rayleigh step thrust bearing (HRSB) where the working magnetohydrodynamic (MHD) fluid is subject to an imposed magnetic field. This hybrid type bearing stems from integrating two classical component: the modified Rayleigh step (variable depth) and the hydrostatic feed entering at the center of the circular thrust bearing. The parameters used in this study consist of one geometric parameter, the Rayleigh step aspect ratio (depth to length ratio) and two dimensionless operational parameters, (i) the Reynolds number based on the hydrostatic fluid jet velocity entering the restrictor (Rejet) and the Reynolds number based on the smooth upper plate angular speed (Replate). The numerical results are obtained using the commercially available package ANSYS (CFX) [4], which utilizes the full three-dimensional Navier-Stokes equations for the steady-state incompressible MHD fluid with constant properties. Results to be presented will will contain both vector and pressure fields within the Rayleigh step profile and on the smooth lands.
Elasto-Plastic Layers of Non-Uniform Thickness in Contact Mechanics
Authors: Fulleringer B. , Ne´lias D.
Published: April 2011

A fast method to solve contact problems when one of the mating bodies contains multiple cubical heterogeneities is proposed in order to deal with non-uniform elastic-plastic coatings. Numerical results are presented for soft or hard coatings, and various cases are considered. Elementary solutions are still fully analytical, using the Eshelby’s equivalent inclusion method so the computing time and allocated memory are kept small, compared to the finite element method. An iterative process is implemented to determine the displacements and stress fields caused by the eigenstrains of all heterogeneities. The proposed method can be seen as an enrichment technique for which the effect of heterogeneities is superimposed to the homogeneous solution in the contact algorithm. 3D and 2D FFT are utilized to improve the computation efficiency. Uniform as well as non-uniform coating thickness can be treated by this method.
Design of a Composite Microtribology Experiment System for Silicon Sidewalls
Authors: Zhang Wei , Shen Sihan , Meng Yonggang
Published: April 2011

This paper designs a composite microtribology experiment system (CMES) to observe the sidewall friction of silicon micro-component pairs. The CMES is composed of a microtribological chip, an out-chip driving system, a video acquiring system, a laser triangulation displacement measure system (LTDMS), and a data processing system. Each microtribological chip has four cantilever friction pairs arranged anti-symmetrically. The size of the cantilever is 200um×50um×5um. The out-chip driving system loads the normal press force on the microtribological chip and produces reciprocating vibration meanwhile to achieve the friction. The video acquisition system is made up of a zoom microscope, a CCD, and a monitor. The LTDMS includes a diode laser, two optical focusing system, and a PSD (Position Sensitive Detectors). Both the video acquiring system and the LTDMS measures the friction characteristics from static to dynamic. The preliminary experiments shows: 1) The CMES has sufficient robustness and reliability. 2) The phenomenon of stick-slip is observed at static state by the LTDMS; 3) and the friction coefficient decreases with the increasing of the reciprocating frequency.
Pattern Formation During Frictional Mechanical Contact
Authors: Nosonovsky Michael , Mortazavi Vahid
Published: April 2011

Friction and wear are usually viewed as irreversible processes, which lead to energy dissipation (friction) and material deterioration (wear). On the other hand, it is known that under certain circumstances frictional sliding can provide mechanisms for the spatial and temporal pattern-formation (self-organization). We discuss the contact mechanics aspects of the pattern-formation and suggest quantitative metrics and criteria for this effect including the stability criteria for the transition from the steady-state sliding to pattern-formation.
Tribological Properties of Polycrystalline Silicon Microdevices Sliding in High Vacuum
Authors: Xiang H. , Komvopoulos K.
Published: April 2011

Contact-mode polycrystalline silicon microdevices were tested in reciprocating sliding in high vacuum. Changes in the adhesion and friction properties of the microdevice sidewall surfaces were evaluated by tracking the development of the adhesion force and static friction coefficient with the accumulation of sliding cycles. After a run-in period of no discernible changes, the adhesion force increased monotonically with the number of sliding cycles, while the static coefficient of friction decreased continuously. Scanning electron microscopy revealed the existence of two sliding regimes where asperity deformation and adhesion were the dominant wear processes. The evolution of adhesion and static friction at sidewall contact interfaces is interpreted in the context of physicochemical phenomena intrinsic of poly-crystalline silicon microdevices.
Nanomechanical and Friction Properties of Ultrathin Amorphous Carbon Films Studied by Molecular Dynamics Analysis
Authors: Wang N. , Komvopoulos K.
Published: April 2011

An ultrathin (<4 nm) film of amorphous carbon (a-C) is used in contemporary disk drives to protect the magnetic medium of the hard disk from corrosion and mechanical wear due to intermittent impact of the low-flying magnetic head. Because of increasing demands for much higher magnetic storage densities (i.e., >10 Tbits/in2), the a-C film thickness must be decreased to <2 nm. However, the tribological and mechanical properties of such thin a-C films are not well understood and, moreover, are extremely difficult to determine experimentally. The objective of this study was to obtain insight into the tribological behavior of ultrathin a-C films by performing molecular dynamics (MD) simulations. MD results of the hardness and friction properties of nanometer-thick a-C films are interpreted in terms of the ratio of tetrahedral-to-trigonal carbon atom hybridization. A critical thickness for the effective protection of the magnetic medium by the a-C film is estimated from MD results. The results of this study elucidate the nanomechanical and nanotribological properties of ultrathin a-C films used as protective overcoats in extremely-high-density magnetic recording.
Coupling of Two EHL-Lubricated Contacts in Gear Dynamics
Authors: Barbieri Marco , Pellicano Francesco
Published: April 2011

In this paper, the effect of vibrations on the elastohydrodynamical lubrication in spur gear pairs will be described. The relevance of inertial effects on film fluid lubrication is clarified by means of comparisons with static formulations. The multilevel technique is used to solve the transient EHL problem for elliptical contacts. Coupling with load balance equation and with different equations of motion is studied. A new model describing the dynamic behavior of two coupled transient EHL elliptical contacts is developed and applied to characterize the dynamics of a spur gear pair.
Nonlinear Mechanics of Rolling Contacts With Surface Defects
Authors: Nakhaeinejad Mohsen , Choi Jaewon , Bryant Michael D.
Published: April 2011

Nonlinear behavior of force and displacements in rolling contacts with the presence of surface defects are studied. Model-based fault assessments in rolling element bearings and gears require detailed modeling and dynamics of faults. A detailed model of rolling element bearings with direct correspondence between parameters of the model and physical components is developed. The model incorporates dynamics of faults, nonlinear contacts, slips and surface separations. Mechanics of contacts with inner race faults (IRF), ball faults (BF), and outer race faults (ORF) are studied using the developed model. Contacts force, displacement and impulse signals are studied for different size and types of surface defects. It is shown that impulse signals contain useful information about the severity of surface defects in rolling element bearing. Results provide model-based diagnostics a deep knowledge of rolling contact mechanics with surface defects to be used for fault assessments.
On the Influence of Friction on Velocity at a Powder-Lubricated Slider-Disk Interface: Experimentation
Authors: Wornyoh E. Y. A. , Higgs C. F. , Pudjoprawoto R.
Published: April 2011

Experiments were conducted to examine the effects of friction coefficient on sliding velocity at a slider pad/disk interface lubricated by MoS2 powder film. The powder film was obtained by shearing compacted pellets of MoS2 against a tungsten carbide (WC) disk and was responsible for supporting the slider pad load. The results from the experiments showed that an adverse interfacial friction coefficient leads to a decrement in the sliding velocity. Contrarily, an increased sliding velocity accompanies a favorable (i.e., smaller) friction coefficient at the WC slider pad/disk interface lubricated by the MoS2 powder lubricant film.
Influence of Friction and Rake Angle on the Formation of Discontinuous Rock Fragments During Rock Cutting
Authors: Menezes Pradeep L. , Lovell Michael R. , Higgs C. Fred
Published: April 2011

Tribological properties during rock cutting under extremely high pressure and high temperature (HPHT) conditions are important in deep mining and drilling operations. In the present investigation, a rock fragmentation process is simulated during mechanical cutting of rock using an explicit finite element code, LS-DYNA. In the simulations, a rigid steel cutting tool of different rake angles was moved at different velocities against a stationary rock material. Rock material properties have been incorporated using an advanced damage constitute material model. In addition, the friction factors at the cutting tool–rock interface were varied in the contact model. The variation of cutting forces, stresses and rock fragment morphology have been investigated. Overall, the results indicate that the explicit finite element model is a powerful tool for simulating rock cutting and the fragmentation process. More specifically, the separation of rock fragments from the rock slab was accurately predicted using the numerical model. The rake angle was found to have significant influence on the fragment morphology during rock cutting. Moreover, the cutting forces and the discontinuous fragmentation process were strongly influenced by the friction and cutting velocity.
A Brief Overview on High Temperature Friction and Wear
Authors: Coskun Mustafa Bulut , Aksit Mahmut Faruk
Published: April 2011

With the race for higher power and efficiency new gas turbines operate at ever increasing pressures and temperatures. Increased compression ratios and firing temperatures require many engine parts to survive extended service hours under large pressure loads and thermal distortions while sustaining relative vibratory motion. On the other hand, wear at elevated temperatures limits part life. Combined with rapid oxidation for most materials wear resistance reduces rapidly with increasing temperature. In order to achieve improved wear performance at elevated temperatures better understanding of combined wear and oxidation behavior of high temperature super alloys and coatings needed. In an attempt to aid designers for high temperature applications, this work provides a quick reference for the high temperature friction and wear research available in open literature. High temperature friction and wear data have been collected, grouped and summarized in tables.
An Interferometric Technique for Measuring Micron Level Clearances Filled With a Lubricant
Authors: Yıldırım Murat , Dursunkaya Zafer , Okutucu Tuba
Published: April 2011

The aim of this study is to develop an interferometric technique to measure micron level clearances occurring in small piston-cylinder arrangements; such as hermetically sealed compressors. A Cartesian model of the piston cylinder arrangement is manufactured and lateral and vertical motions are generated via a step motor, and micrometers, respectively, to simulate the piston motion and the change of clearance during the motion. Experiments are conducted in air and a lubricant. Measurements show the important effect of surface waviness of the mirror and the effect of the motion of the carriage at micron level measurements.
An Investigation of Wear Mechanisms for Transfer Films in an In Situ Self-Replenishing Tribosystem
Authors: Dougherty Patrick S. M. , Pudjoprawoto Randyka , Higgs C. Fred
Published: April 2011

While continuum-based approximations have had success modeling tribosystems with thick film powder flows, they do not predict the behavior of thin powder transfer films which can be worn away from the asperity region during mixed lubrication. This is especially the case for in situ self-replenishing transfer films in the form of compacted solids which are set up to undergo deposition and depletion simultaneously. Although control volume models have been developed to describe this type of tribosystem, very little is known about the wear mechanisms that govern the transfer film in sliding contact. The problem is highlighted through the sudden breakdown of the lubricant film which inevitably leads to interfacial starvation. This study examines evidence that will lead to a fundamental description of the deposition and depletion of powder transfer films by leveraging abrasive wear theory. Justification for this theory is provided by examining the relationship between the coefficient of friction (COF), wear rate, and atomic force microscope (AFM) images of wear interfaces; so that a more accurate model of an in situ self-replenishing solid lubrication process may be constructed.
Development of Fuzzy Inference System With Learning Algorithm for Determining Press-Forming Conditions
Authors: Yoshihara S. , Takahashi A. , Saito M. , MacDonald B. J. , Manabe K.
Published: April 2011

A fuzzy inference system with an associated database was developed in order to determine the forming conditions required to obtain the objective height of a drawn cup using magnesium alloy sheet. The results from both experimental and finite element analyses (FEA) have been used for constructing the database which contains information on the forming conditions used and the resultant height of the drawn cup. A case study utilizing circular-cup deep-drawing was used to test the inference system, whereby experimental results for the height of the drawn cup using specific forming conditions (temperature, blank size and blank holding force) agreed with those predicted using the inference system. This confirms the validity of the inference system. Furthermore, a learning method was developed in order to improve the system using further experimental results, the FEA results and a fuzzy algorithm. The experimental analysis showed good agreement between the required objective height and the experimentally measured height of the drawn cup.
A Statistic Review of Computer-Aided Process Planning Research
Authors: Mao Jin , Xu Xun , Wang Lihui , Newman Stephen
Published: April 2011

Since the late 1970’s, computer-aided process planning (CAPP) has attracted a large amount of research interest, which has led to a huge volume of literature published on this subject. The literature encompasses both reviews and research articles. The review articles are mostly technologically oriented. This paper takes a different angle to look back the CAPP research, that is, a statistic approach. The paper analyses the journals that have been publishing CAPP research works. The concept of “Subject Strength” of a journal is introduced and used to gauge the level of focus of a journal on a particular research subject/domain, i.e. CAPP. Discussions about the recent CAPP research works are presented in different categories as they fall in. The term “Technology Impact Factor (TIF)” is introduced to assess the level of impact of a particular technology, in terms of citation counts. All discussions and analyses are carried out based on the data gathered from the Elsevier’s Scopus abstract and citation database. Finally, a discussion on the future development is presented. The literature suggests that this is the only review article of the similar nature in the first decade of the century.
A Novel Sensor Using Tool Coating and Its Substrate as Thermocouple to Measure Cutting Temperatures
Authors: Zhang Shijun , Liu Zhanqiang
Published: April 2011

The ability to monitor in real time, the thermal impact of sensors on cutting tools has been very appealing to the manufacturing industries. Several methods have been used to obtain tool-chip/workpiece contact temperature. However, special sensors to monitor coated tool temperatures are far and few-in-between. In this paper, the sequence of fabricating a novel coating-substrate thermocouple and calibration setups to measure cutting temperature was proposed. The cutting experiments were carried out under different cutting conditions for 1045 steel. The experimental results showed that this novel technology for measuring cutting temperature is valid in manufacturing processes with coated cutting tools.
Self-Consistent Model of Laminated Composites
Authors: Zhu Yiguo , Zhao Dan , Hu Ping
Published: April 2011

A self-consistent model of laminated composites was constructed. In the model, macroscopic and microscopic stress and strain were divided into two parts, one was In-plane part and the other was Out-of-plane part, then the stiffness and compliance matrices could be partitioned. By using the definitions of macroscopic stress and strain and perfect interface condition, one could get the analytical expressions of macroscopic stiffness and compliance of two-layer composites. Macroscopic stiffness and compliance of multilayer composites could be gotten based on the analytical expressions. The reciprocal property of the stiffness and compliance matrices could be proved by numerical tests and theoretical analysis.
Deformation Size Effects Due to Specimen and Grain Size in Microbending
Authors: Parasız Sunal Ahmet , VanBenthysen Reid , Kinsey Brad L.
Published: April 2011

Sheet metal forming often consists of bending processes in which gradients of deformation exists through the thickness of the workpiece in a localized deformation area. In microscale bending, these deformation gradients become much steeper, as the changes in the deformation occur over short distances (on the order of microns). In addition, with miniaturization the number of grains that are present through the thickness decreases significantly. In this research, the effect of grain size and specimen size on the deformation distribution through the thickness of microbent sheet specimens was investigated via microhardness evaluations. It was found that the deformation distribution, i.e., hardness profile, is not affected significantly by the grain size when the sheet thickness is large (for 1.625 mm specimens) or by miniaturization of the specimen size when the grain size is fine. However, the deformation distribution of the coarse grained specimens deviates from the fine grained ones and from the 1.625 mm thick sheet specimens when the specimen size is miniaturized.
Modeling and Quantification of the Electroplastic Effect When Bending Stainless Steel Sheet Metal
Authors: Salandro Wesley A. , Bunget Cristina , Mears Laine
Published: April 2011

Automotive manufacturers are continuously striving to meet economic demands by designing and manufacturing more efficient and better performing vehicles. To aid this effort, many manufacturers are using different design strategies such to reduce the overall size/weight of certain automotive components without compromising strength or durability. Stainless steel is a popular material for such uses (i.e. bumpers and fuel tanks) since it possesses both high strength and ductility, and it is relatively light for its strength. However, with current forming processes (e.g., hot working, incremental forming, and superplastic forming), extremely complex components cannot always be easily produced, thus, limiting the potential weight-saving and performance benefits that could be achieved otherwise. Electrically-Assisted Manufacturing (EAM) is an emerging manufacturing technique that has been proven capable of significantly increasing the formability of many automotive alloys, hence the “electroplastic effect”. In this technique, electricity can be applied in many ways (e.g., pulsed, cycled, or continuous) to metals undergoing different types of deformation (e.g., compression, tension, bending). When applied, the electricity lowers the required deformation forces, increases part displacement or elongation, and can reduce or eliminate springback in formed parts. Within this study, the effects of EAM on the bending of 304 Stainless Steel sheet metal will be characterized and modeled for different die widths and electrical flux densities. In previous works, EAM has proven to be highly successful on this particular material. Comparison of 3-point bending force profiles for non-electrical baseline tests and various EAM tests will help to illustrate electricity’s effectiveness. An electroplastic bending coefficient will be introduced and used for modeling an electrically-assisted bending process. Additionally, the springback reductions attained from EAM will be quantified and compared. From this work, a better overall understanding of the effects and benefits of EAM on bending processes will be explained.
A Straightening Method Investigation Based on Rolling Caused Stress Redistribution for Distorted Monolithic Components
Authors: Sun Jie , Li Jian Feng , Wang Zhong Qiu
Published: April 2011

Aiming at the difficulty of straightening the distorted monolithic components, residual stress redistribution and deformation compensation method based on rolling process is put forward. Finite element Model is established to investigate the rolling process. Based on the FEM analysis, the relationship curve among rolling position, component wall thickness and deformation after rolling is established. The curve is used as a guideline for rolling parameters selection in actual manufacturing process. Straightening experiment for a scaled frame part is design. The validation of rolling parameters selection based on the straightening curve is verified.
Manufacture of Aerospace Components With Pressure Welding
Authors: Lee Ho-Sung , Yoon Jong-Hoon , Yi Young-Moo
Published: April 2011

Pressure welding technology is a solid state bonding process and generally involves heating the metal surfaces and then applying a suitable amount of axial pressure. In this state the metal components being joined undergo only microscopic deformation and the joining region is homogeneous and complete metallurgical bonding is possible without secondary materials or liquid phases. In the present work, pressure welding of titanium alloys has been investigated to fabricate several aerospace components with various complex configure. The result shows that the pressure welding method has been successfully applied with blow forming for near net shape forming of aerospace components, including high pressure tank for attitude control of spacecraft, and other lightweight structural panels.
The Effects of AHSS Shear Edge Conditions on Edge Fracture
Authors: Shih Hua-Chu , Chiriac Constantin , Shi Ming F.
Published: April 2011

Edge cracking is one of the major issues for stamping Advanced High Strength Steel (AHSS). This type of cracking is influenced by three major factors: the material property, the die condition and the shearing/blanking process. The current shearing/blanking process has been applied to traditional mild steels for years and has not been modified for shearing AHSS. Other than the high energy laser cutting process, the traditional die cutting process would generate a rough edge (burr) with micro cracks in shearing/blanking edges for AHSS, which could serve as the crack initiation during forming. This study is to investigate the effects of shear edge conditions on edge cracking for AHSS. A special hole shearing process has been developed on a laboratory hydraulic press. Different shearing parameters, including die clearance, cutting angle and material orientations, were investigated in terms of shear edge conditions. The hole expansion test was conducted to evaluate the effects of shear edge conditions on the material edge stretchability. Results showed that an optimal selection of die clearance and shearing angle can greatly increase the edge stretchability for AHSS.
Effects of Mechanical Comminution on Enzymatic Conversion of Cellulosic Biomass in Biofuel Manufacturing: A Review
Authors: Zhang Meng , Song Xiaoxu , Pei Z. J. , Wang D. H.
Published: April 2011

It is imperative to develop alternative fuels to replace current petroleum-based liquid transportation fuels. Biofuels produced from cellulosic biomass (forest products and residues, agricultural residues, and dedicated energy crops) is one such alternative. Manufacturing biofuels from cellulosic biomass requires reduction of the material size using mechanical comminution methods. This paper reviews these mechanical comminution methods. It presents their effects on biomass particle size, cellulose crystallinity, and sugar yield. It also discusses the characteristics of each method and future research directions.
Autonomous Distributed AGV System Based on Taxi Transportation Strategy: Effect of Multiple-Load AGVs on Conveyance Efficiency
Authors: Kono Takahiro , Ogawa Keiji , Hirogaki Toshiki , Aoyama Eiichi
Published: April 2011

Manufacturing systems have recently been shifted from high-volume/low-mix manufacturing to high-mix/low-volume manufacturing and renamed “flexible manufacturing systems” (FMSs). However, problems have occurred, primarily the fact that such systems might not be able to cope with quick environment changes. It is not easy to change the layout and facilities of a factory once we build a big system because it controls the whole manufacturing system in FMS hierarchically. Therefore, new systems for variety-variable manufacturing with flexibility are proposed. A general idea of an autonomous and distributed manufacturing system has been suggested, and it seems feasible because each component part has original information-treatment and decision-making functions. The system gives the constituent elements of its manufacturing system an autonomous decision-making function. The role of an automated guided vehicle (AGV) conveyance system, which controls the flow of parts in a factory, is becoming more important, but research in the conveyance system has been uneven. Examples include studies on AGV action decision-making theory, scheduling, and so on, whereas meanwhile, the use of autonomous decision-making controls in places where transportation is received and transported has hardly been researched. On the other hand, applications of knowledge from one field to a different field have recently drawing much attention. Such activity is known as a mimetic solution. We propose an application of knowledge hidden in traffic engineering to manufacture a trial mimetic solution. Manufacturing systems must withstand such uncertain factors as a sudden change of the manufacturing process, and we therefore propose applying the characteristics of taxi transportation with flexibility to an AGV conveyance system. A taxi is a transport unit in a traffic system with higher flexibility in traveling routes and arrival/departure points compared with railways and buses. Our proposed system’s performance is shown based on conveyance efficiency and energy consumption. Additionally, the multiple-load taxis, which are based on taxi characteristics such different body types (small or medium), are applied and evaluated in terms of their conveyance efficiency. Results indicate that a combination of such multiple-load AGVs shows a good performance in terms of higher conveyance efficiency and lower environmental impact.
Effects of Container Geometry on Energy Consumption During Hardening in Ice Cream Manufacturing
Authors: Cromer W. C. , Miller Mark J. , Xin X. J. , Pei Z. J. , Schmidt Karen A.
Published: April 2011

Energy consumption by the dairy food industry in the United States constitutes 10% of all energy consumed by the U.S. food industry. Reducing energy consumption in cooling and refrigeration of foods plays an important role in meeting the challenge of the energy crisis. Hardening is an important and energy-intensive step in ice cream manufacturing. This work presents Finite Element Method (FEM) investigation of the ice cream hardening process, aiming to provide insight and guidance for energy savings in ice cream manufacturing. Effects of container shape and dimensions, container layers, and heat transfer boundary conditions on energy consumption for hardening of ice cream were investigated.
Spatial Blending Functions for Improved Estimation of Contact Pressure Distribution at the Tool-Workpiece Interface
Authors: Sah Sripati , Gao Robert X. , Kurp Timothy
Published: April 2011

On-line measurement of contact pressure distribution (CPD) at the tool-workpiece interface during sheet metal stamping processes plays a critical role in tool wear and product quality monitoring and control. Realizing such measurement poses a significant challenge, due to the severe operating conditions at the contact interface. Since the number of sensors that can be integrated into a tooling structure is limited by concerns of structural integrity, a mathematical framework is needed for estimating the contact pressure distribution measured by sparse sensors. This paper investigates a new technique termed the Spatial Blending Functions (SBF), which provides an improved estimate of the contact pressure distribution by merging measurements from tooling-embedded sensors with simulation results from Finite Element modeling. The effectiveness of the SBF-based merging technique is demonstrated for the case of a panel stamping operation through Finite Element simulations and experiments performed on a stamping press with a tooling-integrated sensing system. Analysis of the results demonstrates that the SBF-based CPD estimation is more accurate than classic numeric surface interpolation methods, thus enhances contact pressure distribution estimation for stamping process monitoring.
Laser Beam Propagation Through Three-Dimensional High-Aspect-Ratio Microholes
Authors: Tao Sha , Wu Benxin , Lei Shuting
Published: April 2011

The drilling of high-aspect-ratio microholes has very important applications in automotive, aerospace, electronics and other areas. However, this is difficult to realize with conventional mechanical machining or electrical discharge machining approaches. Laser ablation can potentially provide a good solution to this, but it also involves many technical difficulties. One of these is that the hole structure may act like a wave guide and affect the laser beam propagation. However, previous investigations on this important issue are very limited. In this paper, laser beam propagation through high-aspect-ratio microholes has been studied by solving the three-dimensional transient Maxwell’s wave equation, and the important discoveries from the calculations are discussed.
AFM-Based Nanomachining for Nano-Fabrication Processes: MD Simulation and AFM Experimental Verification
Authors: Promyoo Rapeepan , El-Mounayri Hazim , Martini Ashlie
Published: April 2011

Recent developments in science and engineering have advanced the fabrication techniques for micro/nanodevices. Among them, the atomic force microscope (AFM) has already been used for nanomachining and nanofabrication such as nanolithography, nanowriting and nanopatterning. This paper describes the development and validation of computational models for AFM-based nanomachining (nanoindentation and nanoscratching). The Molecular Dynamics (MD) technique is used to model and simulate mechanical indentation and scratching at the nanoscale for the case of gold. The simulation allows for the prediction of indentation forces and the friction force at the interface between an indenter and a substrate. The effect of scratching speeds on indentation force and friction coefficient is investigated. The material deformation and indentation geometry are extracted based on the final locations of the atoms, which have been displaced by the rigid tool. In addition to the modeling, an AFM was used to conduct actual indentation at the nanoscale, and provide measurements to which the MD simulation predictions can be compared. The AFM provides resolution on the nanometer (lateral) and angstrom (vertical) scales. A three-sided pyramid indenter (with a radius of curvature ∼ 25 nm) is raster scanned on top of the surface and in contact with it. It can be observed from the MD simulation results that the indentation force increases as the depth of indentation increases, but decreases as the scratching speed increases. Moreover, the friction coefficient is found to be independent of scratching speed.
Investigation of Contact Characteristics of Long-Fiber Reinforced Plastic Gears Based on Observation With a High-Speed Camera
Authors: Otawa Tomoki , Hirogaki Toshiski , Aoyama Eiichi
Published: April 2011

We also observed the dynamic contact state of gear meshing in operating conditions with a high-speed camera. The temperature distribution when driving was measured by thermography. Contact ratio is often used to show contact state, but there are currently no reports that describe the dynamic contact ratio of FRP gears although there are some reports on plastic gears. We therefore considered a contact ratio formula based on a new contact model that the dynamic real deflections of the gear tooth. The temperature distribution measurement was done from the side and the upper surface of the gear. The characteristics of heat generation on the surface of each gear tooth were analyzed, and the temperature distribution was analyzed according to the time and each point of the tooth. (1) FRP gears over heated as a result of driving by the metal gear for a long time. The rise in temperature was rapid and was compounded by heat dissipated from the metal gear. (2) The pitch point of the FRP gear tooth had the highest temperature. The reason for this is that the hysteresis heating is large. It is not easy for the gear to dissipate heat. (3) The temperature rose as a result of hysteresis heating. At high torque, the back surface contact and deflection of the teeth also increased because the gear became viscoelastic.
Study of Double-Layered Microcapsule Formation in Compound Nozzle Jetting
Authors: Wang Wei , Herran C. Leigh , Coutris Nicole , Huang Yong , Mironov Vladimir , Markwald Roger
Published: April 2011

Double-layered microcapsules, which usually consist of a core (polymeric) matrix surrounded by a (polymeric) shell, have been used in many industrial and scientific applications such as microencapsulation of drugs and living cells. Compound concentric nozzle-based jetting has been favored due to its efficiency and precise control of the core-shell compound structure. Thus far, little is known about the underlying formation mechanism of double-layered microcapsules in compound nozzle jetting. This study aims to understand the formability of double-layered microcapsules in compound nozzle jetting by coupling a theoretical analysis with numerical simulations. A linear temporal instability analysis is used to define the perturbation growth rate and its ratio as a function of the wavenumber; and a computational fluid dynamics (CFD) method is implemented to model the microcapsule formation process in order to determine the good microcapsule forming range based on the growth ratio curve. Using a pseudo-bisection method, the lower and upper bounds of the good formability range have been determined for a given materials-nozzle system. The proposed formability prediction methodology has been implemented and validated in modeling a water-poly (lactide-co-glycolide) (PLGA) – air compound jetting system with satisfactory prediction results.
Effects of Operating Conditions on Thin Film Deposition Performance in Air Atomizing Spray Pyrolysis
Authors: Xu Changxue , Huang Yong , Lin Yafu
Published: April 2011

Thin films have been finding more and more applications in electronics, optical devices, and energy conversion and storage devices, to name a few. As one of the most promising thin film deposition techniques, air atomizing spray pyrolysis, which uses compressed air to disrupt the liquid stream into droplets, has been favored in scientific and engineering communities. However, the effects of operating conditions such as liquid flow rate, atomizing air pressure, fan air pressure, and air gap on the geometric properties of deposited thin film are still not systematically studied. The objective of this study is to experimentally investigate the effects of air spraying operating conditions on the surface roughness and thickness of deposited zinc oxide (ZnO) thin film. It is found 1) The surface roughness increases with the liquid flow rate, but decreases with the atomizing air pressure, fan air pressure, and air gap; 2) The surface roughness decreases along both the X and Y directions under any given operating condition; 3) The thickness increases with the liquid flow rate and the atomizing air pressure, but decreases with the fan air pressure and the air gap; and 4) The thickness generally changes differently along the X and Y directions. Along the X direction, it decreases monotonically; however, along the Y direction, it increases first then decreases as in a saddle shape. While ZnO film deposition is studied, it is expected that the above conclusions may be applicable in air spraying other materials.
Comparison of Superabrasive Tools in Rotary Ultrasonic Machining of Stainless Steel
Authors: Cong Weilong , Feng Qiang , Pei Z. J. , Treadwell Clyde
Published: April 2011

Many experiments on rotary ultrasonic machining (RUM) have been conducted to study how input variables (including tool rotation speed, ultrasonic power, feedrate, and abrasive size) affect output variables (such as cutting force, torque, surface roughness, and edge chipping) by using diamond tools. However, a literature review has revealed that there is no reported study on CBN tools in RUM. This paper, for the first time in literature, presents an investigation of RUM of stainless steel using CBN tools. Firstly, an introduction of superabrasive materials and RUM principle was provided. After presenting the experiment procedures and workpiece properties, it reports the results on tool wear, cutting force, torque, surface roughness in RUM of stainless. Finally, it discusses and compares the performances of diamond and CBN tools in RUM of stainless steel under certain conditions.
Layer-by-Layer Nanoassembly of CIS Nanoparticles
Authors: Agarwal Mangilal , Shrestha Sudhir , Ghane Parvin , Varahramyan Kody
Published: April 2011

Copper Indium Selenium (CIS), due to its tunable wide band gap, has been widely studied for photovoltaic applications. In this work, CIS nanoparticles have been fabricated and functionalized with poly(sodium-4-styrene sulfonate) (PSS) and/or poly-allylamine hydrochloride (PAH), which allow them to disperse in aqueous solution. The resulting aqueous dispersion of CIS nanoparticles have subsequently been used to construct thin multilayer CIS films on flexible substrates using Layer-by-Layer (LbL) nanoassembly process. LbL nanoassembly is a cost-effective process that allows construction of composite nanoscale multilayer coatings of oppositely charged polyelectrolytes, nanoparticles and/or other nanomaterials. The results from Quartz Crystal Microbalance (QCM) show that the CIS nanoparticles with other polyelectrolytes, such as PSS and PAH, can be used to deposit thin films of controlled nanometer range thickness using LbL process. The utilization of the developed LbL based CIS films in solar cell fabrication is currently in progress.
Finite Element Analysis of the Effect of Overlapping Impacts of Laser Shock Peening Within Annealed AISI 1053 Steel
Authors: Voothaluru Rohit , Liu C. Richard
Published: April 2011

Laser shock peening is a surface treatment technique similar to conventional shot peening. The laser induced plasma causes plastic deformations and compressive residual stresses in materials which are useful for developing improved properties in the fields of fatigue, wear or stress corrosion cracking. Finite element method is an efficient tool to predict the mechanical effects and the deformations caused due to laser shock peening, which otherwise are difficult to calculate due to the severe pressure imparted in a very short period of time. This paper presents the calculations performed using ABAQUS, for the simulation of multiple laser shock processing in order to evaluate the residual stress and the deformation of the material. A study of the effect of multiple laser shocks and their extent of overlap on the affected depths and the tensile and compressive residual stresses has been discussed. FEM calculations of residual stress fields and extent of surface deformation in annealed AISI 1053 steel has been investigated along with a study of the distribution of tensile and compressive residual stresses due to the difference in the extent of overlap of the multiple shocks.
Application of Electric Current in Friction Stir Welding
Authors: Pitschman Matthew , Dolecki Jacob W. , Johns Garret W. , Zhou Jun , Roth John T.
Published: April 2011

Friction Stir Welding (FSW) is a relatively new joining technique and has many applications. In FSW, heat generated due to friction between FSW tool and work-piece material softens the material and allows the materials in work-pieces to be stirred and joined together. FSW allows the work-pieces to be joined without reaching the melting point of the material, thus resulting in better welds. However, a large amount of mechanical energy has to be consumed for FSW of high-strength, difficult-to-weld metals such as titanium alloys. Hence, new FSW methods should be investigated to reduce the required energy. In this study, an innovative electrically-enhanced friction stir welding (EEFSW) has been developed. Electric current is passed in welding coupons of Aluminum 6061 plates and its effect on welding process and welds are examined. The results indicate that, with the aid of electric current, improvement in welding speed and reduction in energy consumption is obtainable, which enhances the productivity and widens the range of applications of FSW. Weld properties are found to be affected by the introduced current as well.
Adaptive Anomaly Detection Using a Hidden Markov Model
Authors: Lee Seungchul , Li Lin , Ni Jun
Published: April 2011

Online condition monitoring and diagnosis systems are very important in the modern manufacturing industry. We present a new method to assess the degradation processes of multiple failure modes using the Hidden Markov Model (HMM). The HMM is combined with statistical process control (SPC) to detect the occurrence of unknown faults. This method allows an HMM to adjust and update the state space with the identification of new states. Hence, the online degradation assessment and adaptive fault diagnosis can be simultaneously obtained. The turning process are used to illustrate that previously unknown tool wear processes can be successfully detected at the early stages using the HMM.
Ultrasonic-Vibration-Assisted Pelleting of Cellulosic Biomass: Effects of Moisture Content
Authors: Song Xiaoxu , Zhang Meng , Pei Z. J. , Deines Timothy
Published: April 2011

Cellulosic biomass is an important source for making biofuels. However, there are several barriers to cost-effective manufacturing of biofuels using cellulosic biomass. One such barrier is related to the high transportation cost due to the low density of cellulosic biomass. Pelleting of cellulosic biomass is one way to increase its density. This paper reports an experimental study on ultrasonic vibration-assisted pelleting of cellulosic biomass. The study was focused on the effects of moisture content (MC) on pellet density of three kinds of cellulosic biomass (wheat straw, switchgrass, and sorghum). The experimental results show that sorghum has the highest density with three levels of MC among these biomass materials. The highest density was found with sorghum of 20% MC.
Ultrasonic Vibration-Assisted Pelleting of Sorghum Stalks: Effects of Pressure and Ultrasonic Power
Authors: Zhang Qi , Zhang P. F. , Deines Timothy , Pei Z. J. , Wang Donghai , Wu Xiaorong , Pritchett Graham
Published: April 2011

Cellulosic biofuels can be used to replace traditional liquid transportation fuels. Cellulosic biomass is feedstock in manufacturing of cellulosic biofuels. However, the low density of cellulosic biomass feedstock hinders large-scale and cost-effective manufacturing of cellulosic biofuels. Another bottleneck factor in manufacturing of cellulosic biofuels is the low efficiency of the enzymatic hydrolysis of cellulosic biomass materials resulting in a low sugar yield. Ultrasonic vibration-assisted (UV-A) pelleting can increase the density of cellulosic biomass feedstocks via combined effects of mechanical compression and ultrasonic vibration of the tool on the cellulosic biomass. Meanwhile ultrasonic vibration may act as a beneficial pretreatment for enzymatic hydrolysis, which can possibly increase the efficiency of hydrolysis and obtain a higher sugar yield. The pressure and the ultrasonic power are important parameters in UV-A pelleting. Their effects on pellet quality (density, durability, and stability) and sugar yield (after hydrolysis) are experimentally investigated.
Measurement of Tool Internal Temperatures in the Tool-Chip Contact Region by Embedded Thin Film Micro Thermocouples
Authors: Werschmoeller Dirk , Li Xiaochun
Published: April 2011

Monitoring and controlling thermomechanical parameters in tooling materials are imperative for improving the fundamental understanding, reliability and workpiece quality of material removal processes. Polycrystalline boron nitride (PCBN) tools are being used heavily in hard machining/turning. These processes are very sensitive to variation in local machining conditions at tool-workpiece interface and lack a thorough understanding of fundamental thermo-mechanical phenomena, both often leading to abrupt tool failures. Existing sensors to monitor the machining conditions are not suitable for robust process control as they are either destructively embedded and/or don’t possess the necessary spatial and temporal resolution to monitor temperature during machining at the cutting tip/edge effectively. This paper presents an emerging approach for assessing dynamic temperatures in the close vicinity of the tool cutting edge. An array of 10 micro thin film micro thermocouples, fabricated using adapted semiconductor microfabrication methods, has been embedded into PCBN using a modified diffusion bonding technique. Scanning electron microscopy was performed to examine material interactions at the bonding interface and determine optimal bonding parameters. The sensors’ performance is statically and dynamically characterized. They show good linearity, sensitivity and very fast response time.