bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Micro Vapor Bubble Growing Process in Open Capillary Microgrooves
Authors: Guo Chaohong , Hu Xuegong , Wu Liyuan , Tang Dawei , Wang Tao
Published: September 2010

Growing process of an individual micro bubble in open rectangular capillary microgrooves was theoretically analyzed in this study. Several common correlations of bubble growing radius for pool boiling, such as correlations of Zuber et al [1], Cooper et al [2], Labuntsov et al [3], and Zhao et al [4], were proved not precise. An improved method based on the dynamic microlayer model was presented in the paper. The method divided growing process of a micro vapor bubble into three stages: initial growing stage, normal and axial confined ellipsoidal growing stage, and axial subcylindrical growing stage. Heat transfer equations were established based on each stage’s characteristics. Growth period and volume increment of the micro vapor bubble were calculated in each stage. The calculation results show that growth of the micro vapor bubble is distinctly confined by geometric structure of microgrooves. The comparison of the results between calculation and experiment shows that the calculated bubble equivalent radius is consistent with the experimental results.
Flow Past Confined Nano Cylinder in Microscale Channels
Authors: Darbandi Masoud , Setayeshgar Alireza
Published: September 2010

Simulations of flow through microchannels over nano particles are widely encountered in solid particle transportation. In these simulations, the rarefaction phenomenon will affect the microflow behavior and subsequently the aerodynamics coefficients such as the drag coefficient derived for the suspended particles in the flow stream. This is why we use the Lattice Boltzmann method LBM to study the flow past a confined cylinder placed in a microchannel. The LBM is a mesoscopic method capable of solving flow in macro and micro scales. Applying the Maxwellian scattering kernel, the slip velocity is modeled on the channel and cylinder walls appropriately. To validate our formulations, we firstly obtain the results for solving flow in a pressure driven microchannel and the macroflow past a square cylinder and compare our results with the other available numerical and analytical solutions. Next, we study the microflow over nano cylinder model describing nano suspended particles. The results show that the drag coefficient of the nano particle reduces in all ranges of blockage ratio due to the rarefaction domination. To appraise the effect of blockage ratio on the rarefaction effect, we define an effective parameter. The study indicates that the drag coefficient reduction due to rarefaction effect is higher for lower blockage ratios.
Simulation of Heat Transfer in Bridge-Based Micro Calorimeters
Authors: Yu Jun , Tang Zhen’an , Huang Zhengxing , Feng Chong
Published: September 2010

Previous studies of bridge-based micro calorimeters have shown that these devices can measure heat capacity and melting point of ultra thin films with pulse scan calorimetry. The bridge-based micro calorimeters consist of a sample region and several beams that connecting the sample region with silicon substrate. Both the sample region and the beams are suspending on the silicon substrate for thermal isolation. The temperature distribution of the micro calorimeter during a heating pulse depends on the joule-heating of the heating resistor, the heat absorption and heat conduct of the bridge. The heat transfer through the beams during a pulse scan measurement is complex because there is heat generation on some beams and the temperature distribution along the beams is not uniform. Using three dimensional finite element analyses (FEA), the thermal-electrical simulations of the heat transfer in the bridge-based micro calorimeters have been performed. The heat consumption and temperature distribution at steady state analyses, the temperature response of the bridge and the heat generation of the heater at transient analyses have been calculated for the bridge-based micro calorimeter with different sample thermal conductivities and heat capacities. The simulation results indicate that for the bridge-based microcalorimeter using pulse calorimetry, when the heat capacity of the sample film is close to or larger than the heat capacity of an empty calorimeter, the differential method of getting the sample heat capacity from the difference between a micro calorimeter with and without the sample is no longer suitable because the heat transfer and temperature distributions of the two calorimeters are no longer comparable to each other.
Pressure Effect on Flow Boiling Heat Transfer of Water in Minichannels
Authors: Bang Kwang-Hyun , Kim Kyung-Kyu , Choi Ok-Keun , Jeong Hui-Seong
Published: September 2010

The effect of pressure on the flow boiling of water in minichannels has been experimentally studied. The range of pressure was 2 to 16 bars in the experiment. The experimental apparatus consisted mainly of the 1.73 mm inner-diameter round tube test section, gear pump, pre-heater, pressurizer, pre-evaporator, and condenser. The pre-evaporator was used for varying the vapor quality entering the test section. The pressurizer controls the desired system pressure. The test tube is made of 316 stainless steel and the test tube and the pre-evaporator tube were heated by DC electric current through the tubes. The measured flow boiling heat transfer coefficients were in the range of 10000∼40000 W/m2K and showed the general convection dominant trend in terms of vapor quality. The data also indicates that the pressure does not alter the heat transfer coefficient significantly. Comparisons of the experimental data to the existing correlations showed large discrepancy, implying that these correlations are not correctly accounted for pressure.
Measurement of Heat Transfer in the Entrance Region of Small Diameter Tubes
Authors: Lin Ting-Yu , Yang Chien-Yuh , Kandlikar Satish G.
Published: September 2010

Heat transfer coefficient in the entrance region of water flowing through micro-tubes with diameters of 962 μm and 123 μm was investigated in this study. Two temperature measurement methods, thermocouple and liquid crystal thermography (LCT), were used to measure the tube surface temperature. The experimental data showed that the Nu in the entrance region can be predicted well by conventional correlation while using the LCT to measure the temperature. Using the temperature measurements from the thermocouples attached to the surface, the Nu is found to be significantly higher than the prediction. This was believed to be due to the error in measurement of temperature. Simulation results also revealed that the measured temperature for a small diameter tube can be significantly decreased with a thermocouple attached to it. In transition flow, the wall temperature was also found to have a significantly fluctuation, as large as 2 °C, due to the unsteady flow conditions, while for fully established laminar as well as turbulent flow conditions, the fluctuation was measured to be less than 0.2 °C. The effect of viscous heating was negligible in the range of parameters investigated in this study.
Analysis of Non-Newtonian Fluids in Microchannels With Different Wall Materials
Authors: Darbandi Masoud , Shafii Mohammad Behshad , SafariMohsenabad Salman
Published: September 2010

The behavior of non-Newtonian fluids is considered as an important subject in micro scale and microfluidic flow researches. Because of the complexity and cost in the numerical works and the experimental set-ups in some instances, the analytical approach can be taken into account as a robust alternative tool to solve the non-Newtonian microfluidic flows in some special cases benefiting from a few simplified assumptions. In this work, we analyze the flow of two non-Newtonian fluids including the power-law and grade-fluid models in microchannels. For the grade-fluid, the stress tensors are defined considering the Rivlin-Ericksen tensor definitions. To avoid the complexities in the entrance region, the flow is assumed to be hydrodynamically developed. The flow is steady and laminar and the fluid has constant properties independent of its temperature. We treat three different relations between slip velocity and wall shear stress as the slip boundary condition in our analysis. The Homotopy perturbation method is applied to solve the Navier-Stokes equations in case of grade fluid. To achieve the best slip coefficient, our power-law model solution is compared with available experimental data. Moreover, we compare the results of our Homotopy perturbation method with the numerical solutions. The current results show that the best slip relation is the one with a square of wall shear stress dependency.
Digital Microfluidic Device Using Ionic Liquids for Electronic Hotspot Cooling
Authors: Moon Hyejin , Bindiganavale Shreyas , Nanayakkara Yasith , Armstrong Daniel W.
Published: September 2010

Thermal management in electronics become more challenging as the size of electronics decreases, yet, the heat generated from electronics still increases. To enhance cooling efficiency of conventional cooling schemes such as heat pipes, we experimentally present a use of electrowetting on dielectric (EWOD) digital microfluidic technique to force the cooling liquid medium to move to hot spot area. In this paper, firstly, two different EWOD devices were compared in their cooling performance. One is a system using one plane device and sessile droplet of cooling medium and the other is a system using two parallel planes and liquid is sandwiched in between. Secondly, two types of liquids were used and compared as the cooling medium. De-ionized (DI) water and room temperature ionic liquid (RTIL) have been investigated. RTILs are thermally stable thanks to their low vapor pressure. In addition to thermal stability, RTIL can be tailored task specifically by altering cations and anions. Different experiments were conducted to study the capacity of IL’s to change the surface temperature of the hotspot generated and this was compared with that of DI water. The latter showed higher capacity to remove heat, while evaporation problem was predominant in the sandwiched setup. Three different ionic liquids, 1-butyl-3-methylimidazolium chloride or [BMIM]Cl, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide or [BMIM]Ntf2, and [CMIM]FeCl4 showed less effect on changing the surface temperature compared to water. It is due to generally lower heat conductivity and higher viscosity of ILs than water. However, RTILs showed high thermal stability by resulting in no evaporation during cooling process while water had vigorous evaporation. Nanofluid of RTIL and multiwall carbon nanotubes (MWCNT) mixture has been tested as the first step toward enhancing thermal conductivity of RTIL.
Opening Ratio Effect on Electrowetting Droplet Actuation on Perforated Membranes
Authors: Zhao Yuejun , Cho Sung Kwon
Published: September 2010

We have previously developed a microparticle sampling method in which electrowetting-actuated droplets sweep and pick up microparticles trapped on a perforated membrane. In this configuration, a critical issue is to increase the opening ratio (ratio of opening hole area to the total membrane area) in the perforated membrane as much as possible since the higher the opening ratio the lower power consumption in the process of air suction. In contrast, increasing the opening ratio hampers successful electrowetting operations of droplets and thus sampling of microparticles. In this study, we analytically investigate effects of the opening ratio on electrowetting operations. In particular, we are looking at the reversibility of electrowetting operation. Then, we fabricate testing devices to verify the analytical results in the range of the opening ratio up to about 90%. We will also discuss detailed challenging issues in microfabrication to reach such a high opening ratio.
Liquid Metal Flow in the Annular Passage of an Electromagnetic Pump
Authors: Kwon Jeong-Tae , Nahm Taek-Hoon , Kim Seo-Hyun , Lim Hyo-Jae , Kim Chang-Eob
Published: September 2010

An electromagnetic pump using tubular induction motor (TLIM) has been proposed to pump liquid metal fluids. TLIM has been designed for the liquid metal flow system with motor thrust force of about 40∼77 N. The flow characteristics have been investigated by solving Navier-Stokes equation. The Lorentz force effect was included simply by considering it as a constant source term in the Navier-Stokes equation. A wood-metal was chosen for the simulation of liquid metal. The effect of Lorentz force on the flow rate was investigated. Also, in order to verify the analysis results, an experiment was conducted and the experimental results were compared with those of the simulation. The simulation results showed over-estimation of about 10% compared with the experimental ones.
Evaluation of a Tapered Header Configuration to Reduce Flow Maldistribution in Minichannels and Microchannels
Authors: Dharaiya V. V. , Radhakrishnan A. , Kandlikar S. G.
Published: September 2010

In designing a heat exchanger, it is generally assumed that the fluid is uniformly distributed through the heat exchanger core. In reality, the flow distribution is rarely uniform due to inlet and outlet header designs and flow velocity changes in the headers. The flow distribution through a plate-fin heat exchanger (straight Z-type flow) with parallel microchannels and minichannels is studied by using a Computational Fluid Dynamics (CFD) code FLUENT. It was found that the flow maldistribution is quite severe with constant cross-sectional area headers. A modified header design with tapered cross-section was employed and the flow and pressure distributions were investigated using the CFD model. Further, a mathematical model was used to study the effect of the tapered headers on the pressure difference available for each channel across its inlet and outlet ends. The pressure difference across each channel is responsible for the actual flow rate through the channel. Results from the CFD were compared with the model predictions.
Oxygen-Sensing Microfluidic Scaffolds
Authors: Choi Nak Won , Verbridge Scott S. , Williams Rebecca M. , Park Kang-Yeol , Zipfel Warren R. , Fischbach Claudia , Stroock Abraham D.
Published: September 2010

Oxygen in living tissues is a key soluble factor in normal as well as pathological processes. In relation to cancer, the development of oxygen-depleted tumor niches is thought to play an important role in tumor growth and metastasis. An outstanding challenge remains to develop an in vitro system where one can control and monitor oxygen concentration in a spatiotemporal manner within a three-dimensional (3-D) cell-seeded tissue scaffold. We propose the development of oxygen-sensing microfluidic scaffolds, which meet this challenge. Our strategies include 1) the synthesis of oxygen-sensing microbeads, 2) characterization of the beads via both direct imaging of phosphorescence and measurement of phosphorescence lifetime, and 3) visualization and measurement of oxygen-depletion lengths in a simple microfluidic tumor model.
Inward Flow of Micro-Particles in an Evaporating Di-Dispersed Colloid Droplet on Hydrophilic Surface
Authors: Jung Jung-Yeul , Kim Young Won , Yoo Jung Yul
Published: September 2010

It is well known that the liquid and the nanoparticles in an evaporating colloid droplet on the hydrophilic surface move radially outward for the contact line to maintain its position. However, the motion of micro-/nano-particles in an evaporating di-dispersed colloid droplet has not been reported to date. In this study, an experiment on an evaporating di-dispersed colloid droplet on the hydrophilic surface is carried out. It is found that nano-particles move radially outward and remain at the contact line while micro-particles move inward toward the center of the droplet. Further the mechanism of the micro-particles moving toward the center of the droplet is found to be due to the surface tension force of the liquid.
Doppler Optical Coherence Tomography: Real-Time Optical Sectioning for Microfluidics
Authors: Ahn Yeh-Chan , Brenner Matthew , Chen Zhongping
Published: September 2010

Doppler optical coherence tomography (DOCT) is an emerging imaging modality demonstrated in 1991 for the first time and is a functional extension of optical coherence tomography (OCT) to including flow measurement. DOCT allows not only high-resolution, non-invasive, cross-sectional imaging but also simultaneous real-time visualization of sample structure and flow. DOCT is often compared to clinical Doppler ultrasound. However, the spatial resolution of clinical Doppler ultrasound is limited to approximately 100 μm due to the relatively long wavelength of acoustic waves. DOCT takes advantage of the short coherence length of broadband light sources in order to achieve cross-sectional images with micrometer (2–10 μm) scale resolution. DOCT is also superior to ultrasound in that DOCT is operated in non-contact-mode. The last four years have witnessed an era of technology revolution in DOCT, introduced by the Fourier-domain technology that shows tremendous advantage over time-domain DOCT. Fourier-domain Doppler optical coherence tomography (FDDOCT) instruments have higher imaging speed and higher system sensitivity which are able to overcome motion artifacts and enhance minimum measurable velocity, respectively. Because of the aforementioned merits, FDDOCT has a broad range of clinical applications including ophthalmology, cardiology, urology, etc with information of tissue microstructure and blood flow. However, FDDOCT has seldom been applied to diagnose microfluidic devices. In this keynote paper, system configuration, principle behind, and applications of FDDOCT for microfluidics will be covered.
Numerical and Experimental Study on the Thermally Induced Residual Stresses Behavior in the Hybrid Laser/Arc Welding of Lap Joint
Authors: Kong Fanrong , Kovacevic Radovan
Published: September 2010

In this study, a three-dimensional (3D) finite element model is developed to investigate a thermally induced stress field during the laser welding and hybrid laser-gas tungsten arc welding (GTAW) process. In hybrid laser/arc welding, the focus on of this study is on the GTAW process sharing a common molten pool with a laser beam and playing an augmented role in the hybrid welding system. An experimentally-based thermal analysis is performed to obtain the temperature history, which then is applied to the mechanical (stress) analysis. The goal is to determine the optimal welding parameter set that yields the minimum stress concentration. A modified material model is used to consider the influence of face-to-face contact between the top and bottom metal sheets in the thermo-mechanical analysis. Results show that the normal stress components prevail in the weld, and maximum thermal-stress exceeding the yield point of the material exists at the heat affected zone (HAZ). However, the stress concentration in the weld is obviously reduced with laser welding augmented by a GTAW arc. In addition, a series of experiments are performed to validate the numerical results, and a qualitative agreement is achieved.
Laser-Assisted Machining of a Fiber Reinforced Metal Matrix Composite
Authors: Dandekar Chinmaya R. , Shin Yung C.
Published: September 2010

Metal matrix composites due to their excellent properties of high specific strength, fracture resistance and corrosion resistance are highly sought after over their non-ferrous alloys, but these materials also present difficulty in machining. Excessive tool wear and high tooling costs of diamond tools makes the cost associated with machining of these composites very high. This paper is concerned with machining of high volume fraction long-fiber MMC’s, which has seldom been studied. The composite material considered for this study is an Al-2%Cu aluminum matrix composite reinforced with 62% by volume fraction alumina fibers (Al-2%Cu/Al2O3). Laser-machining is utilized to improve the tool life and the material removal rate while minimizing the sub-surface damage. The effectiveness of the laser-assisted machining process is studied by measuring the cutting forces, specific cutting energy, surface roughness, sub-surface damage and tool wear under various material removal temperatures. A multi-phase finite element model is developed in ABAQUS/Standard to identify and assist in selection of cutting parameters such as; tool rake angle, cutting speed and material removal temperature. The multi-phase model is also successful in predicting the damage depth on machining. The optimum material removal temperature is established as 300°C at a cutting speed of 30 m/min. LAM provides a 65% reduction in the surface roughness, specific cutting energy, the tool wear rate and minimum sub-surface damage over conventional machining using the same cutting conditions.
Side-Wall Surface Quality Assessment for Micro-End Milling
Authors: Ko Jeong Hoon , Shaw Kah Chuan , Girsang Irving P. , Ravi Vinay , Dhupia Jaspreet S.
Published: September 2010

Mechanical micro-end milling helps in creating complex three dimensional structures without a restriction on work-piece material. So far, the surface quality assessment achieved in mechanical micro-end milling has mainly focused on the bottom milled surface of the machined part. In this paper, surface quality of the side-wall created by mechanical micro-end milling on stainless steel (SUS 304) and aluminum alloy (Al 6061) is studied. The surface quality thus achieved is assessed by considering three surface assessment factors namely average surface roughness, form error and burr height under various cutting conditions. The cutting parameters varied for machining were spindle speed, feed/tooth, radial depth of cut, and axial depth of cut. The optimal cutting conditions were evaluated for the three surface evaluation factors according to the material and cutting conditions. The surface roughness values were found to have a turning point at a particular spindle speed for both the materials and were affected by spindle speed, feed/tooth and axial depth of cut. The form error was observed to be lesser for higher axial depth of cut due to an increase in the relative tool stiffness. The burr formation was influenced mainly by feed/tooth with an increase in burr height due to the plowing effect at lowest feed rate and pushed uncut chip at highest feed rate.
The Effects of Mach Number on Keyhole Shape in High Intensity Beam Welding or Drilling
Authors: Kuo Shih C. , Wei Peng S. , DebRoy Tarasankar
Published: September 2010

This work is to predict collapse of the molten layer surrounding the keyhole filled with vapor and droplets during drilling or high power density beam welding process. Investigating collapse of the liquid layer is essentially required for an understanding of pore formation in keyhole welding. The collapse of the keyhole is similar to transition between the slug and annular two-phase flows encountered in fluid flow field. In this study, a steady, averaged one-dimensional model widely used in two-phase flow areas is provided. The mixture in the core is treated as a homogeneous fluid. For the sake of clarification, friction induced by the liquid layer and energy absorbed by the vapor are neglected. It shows that, in contrast to insensitive effects of subsonic Mach number, the keyhole subject to supersonic Mach number at the base is readily enclosed or collapsed. A fundamental understanding of pore formation is revealed.
Impact of Supercritical Carbon Dioxide Metalworking Fluids on Tool Life in Turning of Sintered Steel and Milling of Compacted Graphite Iron
Authors: MacLean Douglas J. , Hayes Kim F. , Barnard Thomas , Hull Timothy , Park Ye Eun , Skerlos Steven J.
Published: September 2010

This paper investigates the influence of supercritical carbon dioxide (scCO2) metalworking fluids on tool wear in two automotive manufacturing processes. scCO2 is a low-cost minimum quantity lubrication (MQL) system with excellent cooling characteristics. In valve seat machining of sintered steel with cubic boron nitride (CBN) inserts, scCO2 reduced tool wear by up to 25% and cutting forces by 10% when compared with the benchmark water-based flood metalworking fluid currently used in production operations. In end milling of compacted graphite iron (CGI) with uncoated carbide inserts, scCO2 reduced tool wear by up to 50% when compared with the currently used metalworking fluid. These results are consistent with those from other applications that show scCO2-based metalworking fluids have the potential to reduce tool wear and cutting forces when compared with commonly used water-based metalworking fluids. At the same time scCO2 is environmentally benign, eliminates metalworking fluid maintenance and disposal, and removes the major health risks associated with today’s metalworking fluids.
Optimal Experimentation for Selecting Stable Milling Parameters: A Bayesian Approach
Authors: Traverso Michael G. , Zapata Rau´l , Schmitz Tony L. , Abbas Ali E.
Published: September 2010

Bayesian methods are a powerful tool when making decisions in the presence of uncertainty. Not only do they provide a mathematical framework of incorporating information from both theoretical and experimental sources, but they also quantify the value that can be gained from additional information, such as further experimentation. Consequently, experimental design can be optimized directly in terms of the value added. Manufacturing decisions can often depend on complex functions. In this work, Bayesian methods for predicting functions are explored. First, Brownian distributions, a relatively simple class of distributions with some useful properties are introduced. To illustrate how Brownian distributions can be used in a manufacturing situation, experimental design for stability limit prediction is treated in a case study. In addition, a method of building general distributions from underlying dynamical models is introduced.
Investigation of Micro Scratching and Machining of Glass
Authors: Sajjadi Mozhdeh , Malekian Mohammad , Park Simon S. , Jun Martin B. G.
Published: September 2010

Micro mechanical machining, which is mechanical removal of material using miniature tools, is one of the fabrication methods in the micro realm that has recently attracted a great deal of attention. Micro machining has the advantage of being able to machine complex shapes from brittle materials. The most challenging problem in the micro mechanical machining of brittle materials is the fabrication of fracture-free surfaces. To avoid brittle fractures, a thorough investigation is required to find the machining parameters in the ductile cutting regime, which is characterized by plastic deformation of material when the chip thickness is smaller than a critical value. In this study, the cutting forces and surface characteristics of soda-lime glass are examined. Conical scratch tests are performed to identify the critical chip thickness, and the cutting forces in the ductile regime are modeled. In addition, torus end milling of glass is performed to examine the effects of feed rates, and spindle speeds, and to investigate tool wear.
Modeling of the Off-Axis High Power Diode Laser (HPDL) Cladding Process
Authors: Wen Shaoyi , Shin Yung C.
Published: September 2010

Off-axis high power diode laser (HPDL) cladding is commonly used for surface quality enhancement such as coating, part repairing, etc. Although some laser cladding models are available in the literature, little has been reported on modeling of powder flow and molten pool for a rectangular beam with side powder injection. In this article, a custom-designed flat nozzle delivers the powder material into a distinct molten pool formed by a high power diode laser (HPDL) with a rectangular beam. A powder model is first presented to reveal the powder flow behavior below the flat nozzle. Key parameters such as the nozzle inclination angle, the rectangular beam profile, shielding gas flow rates and powder feed rate are incorporated so that spatial powder density, powder velocity and temperature distribution are distinctly investigated. Then in order to describe thermal and fluidic behavior around the molten pool formed by the rectangular beam, a three dimensional self-consistent cladding model is developed with the incorporation of the distributed powder properties as input. The level set method is adopted to track the complex free surface evolution. Temperature fields and fluid motion in the molten pool area resulting from the profile of rectangular beam are distinctly revealed. The effect of continuous mass addition is also embedded into the governing equations, making the model more accurate. A HPDL cladding with little dilution is formed and the simulated result agrees well with the experiment.
Experimental Investigations on Flatness and Subsurface Damage in Lapping of Substrate Wafers: A Literature Review
Authors: Cong Weilong , Pei Z. J. , Zhang Pengfei
Published: September 2010

Lapping is an important material-removal process for manufacturing of substrate wafers. Objectives of lapping include removing subsurface damage in sliced wafers, thinning wafers to target thickness, and achieving desired flatness of wafer surfaces. A comprehensive literature review has been conducted on experimental investigations on lapping of substrate wafers. The review on material removal rate and surface roughness was published as a journal paper. As a follow-up, this paper reviews the literature on flatness and subsurface damage in lapping of substrate wafers. It presents reported experimental results on effects of process parameters on flatness and subsurface damage.
A Study on Electrolytic In-Process Dressing (ELID) Grinding of Sapphire With Acoustic Emission
Authors: Han Peidong , Marinescu Ioan D. , Srivastava Anil
Published: September 2010

Single crystal sapphire is of significant interest due to its combination of excellent optical, electrical, and mechanical properties. However, fine grinding of sapphire is quite challenging because of its high hardness and low fracture toughness, making it sensitive to cracking. Wheel loading is a common problem in conventional grinding of hard and brittle materials. ELID grinding shows great promise in achieving a mirror surface finish at a relatively high efficiency. ELID grinding of sapphire was investigated using acoustic emission. The effects of processing parameters on surface finish and acoustic emission signals were evaluated. Correlations were found among the dressing current intensity, surface finish and acoustic emission signals. A smoother surface was obtained using a higher dressing current at the cost of a higher wheel wear rate. The wheel wear mechanism in ELID grinding of sapphire was dominated by bond fracture because the bond strength is reduced by electrolysis. Results indicate that the acoustic emission technique has the potential to be used for monitoring ELID grinding process, detecting the condition of the grinding wheel, and investigating the mechanisms of ELID grinding.
Numerical Simulation on Nanoparticles Integrated Laser Shock Peening of Aluminum Alloy
Authors: Ye Chang , Cheng Gary J.
Published: September 2010

In this paper, numerical simulation of nanoparticle integrated laser shock peening of aluminum alloys was carried out. A “tied constraint” was used to connect the matrix and nanoparticle assembly in ABAQUS package. Different particle size and particle volumes fraction (PVF) were studied. It was found that there is significant stress concentration around the nanoparticles. The existence of nanoparticle will influence the stress wave propagation and thus the final stress and strain state of the material after LSP. In addition, particle size, PVF and particle orientation all influence the strain rate, static residual stress, static plastic strain and energy absorption during the LSP process.
Aspen Plus Process Simulation of Flexible Feedstock Thermo-Chemical Ethanol Production
Authors: Kou Nannan , Zhao Fu , Zhang Li
Published: September 2010

Current US transportation sector mainly relies on liquid hydrocarbon derived from petroleum and about 60% of the petroleum consumed is from areas where supply may be disturbed by regional instability. This has led to serious concerns on global warming and energy security. To address these issues, numerous alternative energy carriers have been proposed. Among them, second generation biofuel is one of the most promising technologies. Gasification based thermo-chemical conversion can utilize a wide range of biomass wastes and residues and bring flexibility to both feedstock and production sides of a plan. Thus it presents an attractive technical route. In this paper, a flexible feedstock thermo-chemical ethanol production process is investigated. This research focuses mainly on the evaluation of the feasibility of the process through numerical simulation. An existing thermo-chemical ethanol production model developed by NREL has been updated to handle the cases when different biomass feedstock and feedstock combinations are used. It is found that the ethanol yield is positively linear proportional to the feedstock feeding rate, while the total conversion efficiency is negatively proportional to the feeding rate. To demonstrate a feedstock management strategy, a plant located near a major city with a population of 200,000 and above is considered and MSW, corn stover and wood chips are selected as potential feedstock. Simulation results indicate that with wood chips as the backup feedstock the plant can be operated under extreme conditions when corn stover availability is significantly reduced without major equipment modification.
Flank Wear of Multi-Layer Coated Tool and Wear Prediction Using Abrasion Wear Model
Authors: Park Kyung-Hee , Kwon Patrick Y.
Published: September 2010

In this paper, we have combined experimental and numerical approaches to understand the flank wear and its evolution of the multi-layer (TiCN/Al2O3/TiCN) coated carbide insert after continuous turning of AISI 1045 steels. In addition using advanced microscope techniques such as scanning electron microscope, confocal laser scanning microscope, etc., we have captured the three dimensional images of flank wear. Using the wavelet filtering, the roughness profiles and groove sizes on the flank surface were analyzed and compared. Both 2-body and 3-body abrasion models were used as the basis to predict flank wear lands, which are then compared with the experimentally observed wear images. Finite Element (FE) models were developed to simulate the changes on the interfacial conditions as the flank wear progresses during cutting.
Effect on the Forgeability of Magnesium AZ31B-O When Continuous DC Electricity is Applied
Authors: Jones Joshua J. , Roth John T.
Published: September 2010

Currently, the automotive and aircraft industries are considering increasing the use of magnesium within their products due to its favorable strength-to-weight characteristics. However, the implementation of this material is problematic as a result of its limited formability. Partially addressing this issue, previous research has shown that Electrically-Assisted Manufacturing (EAM) improves the tensile formability of magnesium sheet metal. While these results are highly beneficial towards fabricating the skin of the vehicle, a technique for improving the production of the structural/mechanical components is also desirable. Given the influence that EAM has already exhibited on tensile deformation, the research herein focuses on incorporating this technique within forging operations. The potential benefit of using EAM on compressive processes has been demonstrated in related research where other materials, such as titanium and aluminum, have shown improved compressive behavior. Therefore, this research endeavors to amalgamate these findings to Mg AZ31B-O, which is traditionally hard to forge. As such, to demonstrate the effects of EAM on this alloy, two series of tests were performed. First, the sensitivity of the alloy to the EAM process was determined by varying the current density and platen speed during an upsetting process (flat dies). Then, the ability to utilize impression (shaped) dies was examined. Through this study, it was shown that the EAM process increases the forgeability of this magnesium alloy through improvements such as decreased machine force and increased achievable deformation. Additionally, the ability to form the desired final specimen geometry was achieved.
Determining the Optimal Interval for the Technical Diagnostics of Bearings
Authors: Savic Branko M. , Jovanovic Vukica
Published: September 2010

Bearings are important part of many machines and technical systems. Thus, their preventive maintenance has to be carefully planned. It is important to predict accurate period in which a bearing will work in its nominal performance. Therefore, inspection requirements and intervals have to be determined for appropriate bearing maintenance. Diagnostics’ schedule has to take into account an importance of the specific system or machine. There are various methods for that. Even with their application, every now and then, the improper selection, unexpected variations in machine performance, bearing handling, used materials, and various working conditions can cause the bearing to wear off faster or last longer than predicted. Hence, it is desirable to focus on systematic optimization of bearing testing schedule. In addition, one of the main reasons for this is because diagnostics procedures themselves are costly and lengthy. The intention of study presented in this paper is to make a model that will be complex in the sense of relating maintenance expenses, condition parameters, and reliability elements of the system, but simple enough for use in more general applications. Developed model should take into account several factors, so that it can be usable in practice. This mathematical model could be used in technical systems for bearings inspection. The model has been developed based on normal distribution regime until its failure. The normal distribution was used because of its simplicity during initial phase of this study. The Weibull distribution could be used to address other problems that are out of scope of normal distribution. The exact results have been obtained in the implementation of the diagnostics technique according to this sort of distribution regime. In this paper, an example of its implementation on one specific problem will be shown.
Evaluation of Cooling Potential and Tool Life in Turning Using Metalworking Fluids Delivered in Supercritical Carbon Dioxide
Authors: Clarens Andres F. , Park Ye-Eun , Temme Jacob , Hayes Kim , Zhao Fu , Skerlos Steve
Published: September 2010

Carbon Dioxide is an industrial byproduct that has been proposed as an alternative metalworking fluid (MWF) carrier with lower environmental impacts and better cooling potential than existing MWFs. This paper investigates the heat removal and tool life effects of rapidly expanding supercritical CO2 (scCO2)-based MWFs relative to MWFs delivered as a flood of semi-synthetic emulsion or as minimum quantity lubrication (MQL) sprays. When cutting both compacted graphite iron (CGI) and titanium, tool wear was most effectively controlled using the scCO2-based MWF compared with the other MWFs. Analysis in this paper suggests that the performance benefit imparted by rapidly expanding scCO2 appears to be related to both the cooling potential and penetration of the sprays into the cutting zone. High-pressure gas sprays have lower viscosity and higher velocity than conventional MWFs. An experiment in which the spray direction was varied clearly demonstrated the importance of spray penetration in tool wear suppression. The type of gas spray is also a significant factor in tool wear suppression. For instance, a spray of N2 delivered under similar conditions to CO2 effectively reduced tool wear relative to water based fluids, but not as much as CO2. This result is particularly relevant for MQL sprays which are shown to not cool nearly as effectively as scCO2 MWFs. These results inform development of scCO2-based MWFs in other machining operations, and provide insight into the optimization of scCO2 MWF delivery.
Effects of Pulse Shape Modulation in Nd:YAG Laser Beam Welding on the Weld Pool Flow and Solidification
Authors: Wilden J. , Jahn S. , Kotali´k P. , Neumann T. P. , Holtz R.
Published: September 2010

Laser beam welding is a field of growing importance to the industry. As a result of extensive and continuous development of laser beam technology, pulsed Nd:YAG laser beam sources have been introduced. Pulsed laser welding offers the advantage of very low heat input to the workpiece, resulting in low distortion and the ability to join heat sensitive components. Further improvements to the method consider pulse shape modulation in Nd:YAG laser beam sources resulting in improved weld pool dynamics. Nd:YAG laser beam welding with pulse shape modulation is studied both experimentally and theoretically. Observational results on the interaction between time-dependent heat fluxes and flows in the weld pool as well as on solidification of the molten material are presented. In welds produced with modulated laser beam pulse shape, improved material flow and finer microstructure have been observed. Using an axisymmetric 2D model for heat transfer coupled with surface tension driven flow of molten metals undergoing solid-liquid and evaporation phase transitions in the weld pool, it is shown that the time modulation of the pulse power influences the melting front and flow velocity which together with the predicted undercooling may explain the fine-grain structure of the resolidified welds that have no cracks inside.
Sequence Dependent Parallel Machine Scheduling Using Parallel Ant Colony Optimization With Graphics Hardware Acceleration
Authors: Zhu Weihang , Curry James , Mishra Anjali , Zaloom Victor
Published: September 2010

This paper studies the effectiveness of using parallel Ant Colony Optimization for sequence dependent parallel machine scheduling on a Graphics Processing Unit (GPU) hardware platform. Parallel machine scheduling is a traditional NP-hard combinatorial optimization problem. In this research, a hybrid ant colony optimization method that combines the ‘Apparent Tardiness Cost with Setups’ (ATCS) dispatching rule with massive ants is proposed to solve the parallel machine scheduling problem quickly and efficiently. The computational results demonstrate that the proposed method is effective and solve the problems order of magnitude faster with a GPU accelerated implementation.
The Effects of Ultrasonic Treatment on Fiber-Reinforced Composite Materials
Authors: Braver Chad , Tumey Matthew , Harlow Adam , Han Qingyou
Published: September 2010

The mechanical properties of fiber-reinforced composite materials are highly dependent on proper saturation of the resin within the reinforcement fibers. The research evaluates the effect of ultrasonic treatment during composite curing, in an effort to increase interlaminar bonding strength, lower void content, and improve the matrices ability to transfer stresses to the reinforcement fiber. The testing methods that were performed evaluated the effects or the ultrasonic treatment on the specimen in three point bending, and shear between layers of the matrix. The mechanical properties and the microstructure of the test specimen are discussed.
Assessment of Tool Wear Based on Surface Texture Parameters
Authors: Liao Yi , Stephenson David A. , Ni Jun
Published: September 2010

This research presents a new way to determine the condition of a cutting tool based on high definition surface texture parameters. Recently, a laser holographic interferometer has been developed to rapidly measure the whole workpiece surface (e.g. 300mm×300mm) and generate a 3D surface height map with micron level accuracy. This technique enables on-line surface measurement for machined parts. By measuring the surface texture of workpieces, the interaction between the tool’s cutting edges and the surface can be extracted as a spatial signature. It can then be used as a warning sign for tool change because the workpiece produced by a heavily worn tool exhibits more irregularities than those produced by a normal tool. Three surface texture parameters: image intensity histogram, surface peak-to-valley height and surface waviness are employed to detect the onset of severe tool wear. Furthermore, surface waviness can also be used to classify the different phases of tool wear. In this work, nine surface samples under different tool wear phases are created and analyzed using surface texture parameters combined with Statistical Process Control (SPC) charts to assess tool conditions. The results verify that these surface texture parameters can be used for on-line tool wear monitoring.
Robotic Manufacturing of Near-Net Shaped Short-Fiber Reinforced Composites With Functional Properties
Authors: Paul Antony , Gallagher Jeffery M. , Cipra Raymond J. , Siegmund Thomas
Published: September 2010

Fiber reinforced composite materials are now frequently being used over conventional materials for their ability to achieve tailored properties and performance characteristics. With the recent advancements in manufacturing techniques, short-fiber composites are coming into prominence in this sector, with their cost advantage and their capability for large throughput. Randomness of fiber orientation is inherent to short fiber composite manufacturing processes. In order to effectively manipulate the mechanical properties of a short-fiber reinforced composite, it is imperative to adequately control the orientation of the fibers during the deposition stage. A process is currently developed to acquire geometrical data of the target object and to utilize it to create a short-fiber reinforced component with controlled fiber orientation. The topological data acquisition of the object is made possible using non-contact 3D imaging techniques. The geometric data is then transferred to a commercial CAD package for the added capability to manipulate the geometry as may be required for specific applications. Subsequently, geometric data constitutes the basis of path planning for the tooling processes. In our process, a novel rapidly re-configurable tooling and molding technology is employed by which a 6-axis robotic arm is used to sculpt a pin-device vacuum surface. After the tooling is completed, the robotic arm will use a deposition nozzle to orient a steady stream of initially random short-fiber from a feeder into a unidirectional output, onto the tool surface. By controlling the position and orientation of the deposition nozzle, it is possible to control the orientation and density of fiber in each section of the near-net shaped composite pre-form. The fiber pre-form is then impregnated with a suitable matrix medium and cured to create the required component. The outlined process is thus capable of manufacturing a near-net shaped short-fiber reinforced component with highly specific mechanical properties. One of the many applications envisaged using this process is the manufacture of custom form-fitting braces, masks and guards for use in healthcare products. A patient intervention can have his or her features acquired using stereo-imaging and have corrective measures incorporated into the device prior to manufacturing. By controlling the orientation and density of the fiber at different portions of the device, it is possible to provide adequate support at specific areas or to restrict movement in specific directions while providing compliance to movement in the others.