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2008

Iowa State University

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Articles 1 - 30 of 87

Full-Text Articles in Mechanical Engineering

Obtaining A Relationship Between Process Parameters And Fracture Characteristics For Hybrid Co2 Laser∕Waterjet Machining Of Ceramics, Dinesh Kalyanasundaram, Pranav Shrotriya, Palaniappa A. Molian Dec 2008

Obtaining A Relationship Between Process Parameters And Fracture Characteristics For Hybrid Co2 Laser∕Waterjet Machining Of Ceramics, Dinesh Kalyanasundaram, Pranav Shrotriya, Palaniappa A. Molian

Mechanical Engineering Publications

A combined experimental and analytical approach is undertaken to identify the relationship between process parameters and fracture behavior in the cutting of a 1mm thick alumina samples by a hybrid CO2 laser∕waterjet (LWJ) manufacturing process. In LWJ machining, a 200W power laser was used for local heating followed by waterjet quenching of the sample surface leading to thermal shock fracture in the heated zone. Experimental results indicate three characteristic fracture responses: scribing, controlled separation, and uncontrolled fracture. A Green’s function based approach is used to develop an analytical solution for temperatures and stress fields generated in the workpiece ...


Simultaneous Three-Dimensional Geometry And Color Texture Acquisition Using Single Color Camera, Song Zhang, Shing-Tung Yau Dec 2008

Simultaneous Three-Dimensional Geometry And Color Texture Acquisition Using Single Color Camera, Song Zhang, Shing-Tung Yau

Mechanical Engineering Publications

A novel technique that uses a single color camera to capture high-resolution three-dimensional (3-D) geometry and the perfectly aligned color texture simultaneously is discussed. A projector projects three phase-shifted black-and-white fringe patterns onto the object, and a color camera captures the fringe images reflected by the object. From these three fringe images, both 3-D shape and the color texture are obtained. Moreover, since only three fringe images are required, this proposed technique permits real-time 3-D shape measurement. Experiments are presented to demonstrate the success of this technique.


Development Of A Dual-Handed Haptic Assembly System: Sharp, Abhishek Seth, Hai-Jun Su, Judy M. Vance Nov 2008

Development Of A Dual-Handed Haptic Assembly System: Sharp, Abhishek Seth, Hai-Jun Su, Judy M. Vance

Mechanical Engineering Publications

Virtual reality (VR) technology holds promise as a virtual prototyping (VP) tool for mechanical assembly; however, several developmental challenges still need to be addressed before VP applications can successfully be integrated into the product realization process. This paper describes the development of System for Haptic Assembly and Realistic Prototyping (SHARP), a portable virtual assembly system. SHARP uses physics-based modeling for simulating realistic part-to-part and hand-to-part interactions in virtual environments. A dual-handed haptic interface for a realistic part interaction using the PHANToM® haptic devices is presented. The capability of creating subassemblies enhances the application’s ability to handle a wide variety ...


Enhancing Co−Water Mass Transfer By Functionalized Mcm41 Nanoparticles, Haiyang Zhu, Brent H. Shanks, Theodore J. Heindel Oct 2008

Enhancing Co−Water Mass Transfer By Functionalized Mcm41 Nanoparticles, Haiyang Zhu, Brent H. Shanks, Theodore J. Heindel

Mechanical Engineering Publications

Organic groups are grafted to 250-nm-diameter MCM41 nanoparticles with a spherical morphology to enhance the CO−water volumetric mass-transfer coefficient (kLa) for synthesis gas fermentation. The results indicate that (i) 250-nm MCM41 nanoparticles show a higherkLa value than large silica particles (1.4 and 7 μm), (ii) surface hydroxyl groups on MCM41 nanoparticles play an important role in mass-transfer enhancement, (iii) organic groups grafted to MCM41 modify the mass-transfer enhancement, and (iv) mercaptan groups grafted to MCM41 show the most mass-transfer enhancement of 1.9 times that of no nanoparticle addition. The CO−water mass-transfer ...


Differential Surface Stress Sensor For Detection Of Chemical And Biological Species, K. Kang, Marit Nilsen-Hamilton, Pranav Shrotriya Oct 2008

Differential Surface Stress Sensor For Detection Of Chemical And Biological Species, K. Kang, Marit Nilsen-Hamilton, Pranav Shrotriya

Mechanical Engineering Publications

We report a sensor consisting of two micromachined cantilevers (a sensing/reference pair) that is suitable for detection of chemical and biological species. The sensing strategy involves coating the sensing cantilever with receptors that have high affinities for the analyte. The presence of analyte is detected by determining the differential surface stress associated with its adsorption/absorption to the sensing cantilever. An interferometric technique is utilized to measure the differential bending of the sensing cantilever with respect to reference. Surface stress associated with hybridization of single stranded DNA is measured to demonstrate the unique advantages of the sensor.


Sublimation Inside An Elastoplastic Material, Valery I. Levitas, Nataliya Altukhova Oct 2008

Sublimation Inside An Elastoplastic Material, Valery I. Levitas, Nataliya Altukhova

Aerospace Engineering Publications

Thermodynamic and kinetic approaches for sublimation inside elastoplastic material under tensile stress are developed for large strains. Various conceptual problems related to irreversible plastic deformation are addressed for a spherical bubble. They include definitions of the thermodynamic driving forces and activation energies, nontraditional concepts of a critical nucleus, path dependence of its appearance, modes of its growth (sublimation or expansion due to loss of mechanical stability), and the possibility of reverse transformation. The kinetic relationships between sublimation pressure and temperature are obtained.


Approximating A Three-Dimensional Fluidized Bed With Two-Dimensional Simulations, Mirka Deza, Francine Battaglia, Theodore J. Heindel Oct 2008

Approximating A Three-Dimensional Fluidized Bed With Two-Dimensional Simulations, Mirka Deza, Francine Battaglia, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Fluidized beds can be used to gasify biomass in the production of producer gas, a flammable gas that can replace natural gas in process heating. Modeling these reactors with computational fluid dynamics (CFD) simulations is advantageous when performing parametric studies for design and scale-up. From a computational resource point of view, two-dimensional simulations are easier to perform than three-dimensional simulations, but they may not capture the proper physics. This paper will compare two- and three-dimensional simulations in a 10.2 cm diameter fluidized bed with side air injection to determine when two-dimensional simulations are adequate to capture the bed hydrodynamics ...


Simulating Gas-Liquid Flows In An External Loop Airlift Reactor, Deify Law, Francine Battaglia, Theodore J. Heindel Oct 2008

Simulating Gas-Liquid Flows In An External Loop Airlift Reactor, Deify Law, Francine Battaglia, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

The external loop airlift reactor (ELALR) is a modified bubble column reactor that is composed of two vertical columns that are connected with two horizontal connectors. Airlift reactors are utilized in fermentation processes and are preferred over traditional bubble column reactors because they can operate over a wider range of conditions. Computational fluid dynamics (CFD) simulations can be used to enhance our understanding of the hydrodynamics within these reactors. In the present work, the gas-liquid flow dynamics in an external loop airlift reactor are simulated using CFDLib with an Eulerian-Eulerian ensemble-averaging method in two-dimensional (2D) and three-dimensional (3D) coordinate systems ...


Parametric Instability Of A Traveling Plate Partially Supported By A Laterally Moving Elastic Foundation, V. Kartik, Jonathan A. Wickert Oct 2008

Parametric Instability Of A Traveling Plate Partially Supported By A Laterally Moving Elastic Foundation, V. Kartik, Jonathan A. Wickert

Mechanical Engineering Publications

The parametric excitation of an axially moving plate is examined in an application where a partial foundation moves in the plane of the plate and in a direction orthogonal to the plate's transport. The stability of the plate's out-of-plane vibration is of interest in a magnetic tape data storage application where the read/write head is substantially narrower than the tape's width and is repositioned during track-following maneuvers. In this case, the model's equation of motion has time-dependent coefficients, and vibration is excited both parametrically and by direct forcing. The parametric instability of out-of-plane vibration is ...


Broadband Measurement Of Rate-Dependent Viscoelasticity At Nanoscale Using Scanning Probe Microscope: Poly(Dimethylsiloxane) Example, Zhonghua Xu, Kyongsoo Kim, Qingze Zou, Pranav Shrotriya Sep 2008

Broadband Measurement Of Rate-Dependent Viscoelasticity At Nanoscale Using Scanning Probe Microscope: Poly(Dimethylsiloxane) Example, Zhonghua Xu, Kyongsoo Kim, Qingze Zou, Pranav Shrotriya

Mechanical Engineering Publications

A control approach to achieve nanoscale broadband viscoelasticmeasurement using scanning probe microscope(SPM) is reported. Current SPM-based force measurement is too slow to measure rate-dependent phenomena, and large (temporal) measurement errors can be generated when the sample itself changes rapidly. The recently developed model-less inversion-based iterative control technique is used to eliminate the dynamics and hysteresis effects of the SPM hardware on the measurements, enabling rapid excitation and measurement of rate-dependent material properties. The approach is illustrated by the mechanical characterization of poly(dimethylsiloxane) over a broad frequency range of three orders of magnitude (∼1 Hz to 4.5 KHz).


Unsteady Nanoscale Thermal Transport Across A Solid-Fluid Interface, Ganesh Balasubramanian, Soumik Banerjee, Ishwar K. Puri Sep 2008

Unsteady Nanoscale Thermal Transport Across A Solid-Fluid Interface, Ganesh Balasubramanian, Soumik Banerjee, Ishwar K. Puri

Ganesh Balasubramanian

We simulate unsteady nanoscale thermal transport at a solid-fluidinterface by placing cooler liquid-vapor Ar mixtures adjacent to warmer Fe walls. The equilibration of the system towards a uniform overall temperature is investigated using nonequilibrium molecular dynamics simulations from which the heat flux is also determined explicitly. The Ar–Fe intermolecular interactions induce the migration of fluid atoms into quasicrystallineinterfacial layers adjacent to the walls, creating vacancies at the migration sites. This induces temperature discontinuities between the solidlikeinterfaces and their neighboring fluid molecules. The interfacial temperature difference and thus the heat flux decrease as the system equilibrates over time. The averaged ...


Proper Orthogonal Decomposition-Based Reduced Order Model Of A Hydraulic Mixing Nozzle, Sunil Suram, Douglas S. Mccorkle, Kenneth M. Bryden Sep 2008

Proper Orthogonal Decomposition-Based Reduced Order Model Of A Hydraulic Mixing Nozzle, Sunil Suram, Douglas S. Mccorkle, Kenneth M. Bryden

Mechanical Engineering Conference Presentations, Papers, and Proceedings

In this work, a reduced order model is constructed for a hydraulic mixing nozzle using proper orthogonal decomposition. Data from several CFD computations are collected to provide the data for input to the reduced order model and flow is projected onto the most dominant principal axes to study the flow structures. Flow structures are compared for the original and optimized shape nozzles to study the effect of changing the nozzle’s shape on the flow characteristics. This study also addresses issues regarding the time required for collecting CFD data and how it has been reduced by using a modified convergence ...


Inner-Loop Control For Electromechanical „Ema… Flight Surface Actuation Systems, Saeid Habibi, Jeff Roach, Greg R. Luecke Sep 2008

Inner-Loop Control For Electromechanical „Ema… Flight Surface Actuation Systems, Saeid Habibi, Jeff Roach, Greg R. Luecke

Mechanical Engineering Publications

This manuscript pertains to the application of an inner-loop control strategy to electromechanical flight surface actuation systems. Modular electromechanical actuators (EMAs) are increasingly used in lieu of centralized hydraulics for the control of flight surfaces in the aerospace sector. The presence of what is termed as a dead zone in these actuators significantly affects the maneuverability, stability, and the flight profiles of aircrafts that use this actuation concept. The hypothesis of our research is that flight surface actuation systems may be desensitized to the effects of dead zone by using a control strategy with multiple inner loops. The proposed strategy ...


Minimum Fluidization Velocity And Gas Holdup In Fluidized Beds With Side Port Air Injection, Nathan P. Franka, Joshua B. Drake, Theodore J. Heindel Aug 2008

Minimum Fluidization Velocity And Gas Holdup In Fluidized Beds With Side Port Air Injection, Nathan P. Franka, Joshua B. Drake, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Fluidized beds can be used to gasify biomass in the production of producer gas, a flammable gas that can replace natural gas in process heating. Knowing how the fluidized bed hydrodynamics vary as reactor dimensions are scaled up is vital for improving reactor efficiency. This study utilizes 10.2 cm and 15.2 cm diameter fluidized beds with added side port air injection to investigate column diameter effects on fluidized bed hydrodynamics. Both inert (glass beads) and biomass (ground walnut shell and ground corncob) bed materials are used and the hydrodynamic differences with side port air injection are recorded. Minimum ...


Interactive Deformation Through Mesh-Free Stress Analysis In Virtual Reality, Daniela Faas, Judy M. Vance Aug 2008

Interactive Deformation Through Mesh-Free Stress Analysis In Virtual Reality, Daniela Faas, Judy M. Vance

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Virtual reality (VR) techniques are used to create an environment that allows an engineer to modify the shape of a part and see the changes in the stress state immediately. A virtual reality application, Interactive Virtual Design Application (IVDA), that allows fast mesh-free analysis of multiple element types, including two-dimensional (2D) elements, is described in detail. Taylor series approximations and Pre-conditioned Conjugate Gradient (PCG) methods are used with mesh-free analysis to perform quick reanalysis during interactive shape modification. Prior to this work, only 3D elements were incorporated into the method. The addition of 2D elements greatly expands the potential application ...


A General Architecture For Distributed Vr Interfaces, Thomas Batkiewicz, Abhishek Seth, Bryan Walter, Jared Knutzon, James H. Oliver Aug 2008

A General Architecture For Distributed Vr Interfaces, Thomas Batkiewicz, Abhishek Seth, Bryan Walter, Jared Knutzon, James H. Oliver

Mechanical Engineering Conference Presentations, Papers, and Proceedings

This paper describes a software architecture useful in creating new virtual reality interfaces across a clustered network of computers. The architecture takes advantage of a concept common to desktop application development, the event loop, and provides a method by which it can be shared effectively between nodes in a cluster. This method improves upon the common replication approach to cluster synchronization by creating a single, simple object to share, as well as by supporting node specialization in a generic cluster. The method is designed to be easily added to existing applications as well as speed the development of virtual reality ...


A Validation Study For The Hydrodynamics Of Biomass In A Fluidized Bed, Mirka Deza, Francine Battaglia, Theodore J. Heindel Aug 2008

A Validation Study For The Hydrodynamics Of Biomass In A Fluidized Bed, Mirka Deza, Francine Battaglia, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Computational modeling of fluidized beds can be used to predict operation of biomass gasifiers after extensive validation with experimental data. The present work focused on computational simulations of a fluidized bed using a multifluid Eulerian-Eulerian model to represent the gas and solid phases as interpenetrating continua. Hydrodynamic results from the simulations were quantitatively compared with X-ray flow visualization studies of a similar bed. It was found that the Gidaspow model can accurately predict the hydrodynamics of the biomass in a fluidized bed. The coefficient of restitution of biomass was fairly high and did not affect the hydrodynamics of the bed ...


Sum Frequency Generation Vibrational Spectroscopy Of Pyridine Hydrogenation On Platinum Nanoparticles, Kaitlin M. Bratlie, Kyriakos Komvopoulos, Gabor A. Somorjai Aug 2008

Sum Frequency Generation Vibrational Spectroscopy Of Pyridine Hydrogenation On Platinum Nanoparticles, Kaitlin M. Bratlie, Kyriakos Komvopoulos, Gabor A. Somorjai

Kaitlin M. Bratlie

Pyridine hydrogenation in the presence of a surface monolayer consisting of cubic Pt nanoparticles stabilized by tetradecyltrimethylammonium bromide (TTAB) was investigated by sum frequency generation (SFG) vibrational spectroscopy using total internal reflection (TIR) geometry. TIR-SFG spectra analysis revealed that a pyridinium cation (C5H5NH+) forms during pyridine hydrogenation on the Pt nanoparticle surface, and the NH group in the C5H5NH+ cation becomes more hydrogen bound with the increase of the temperature. In addition, the surface coverage of the cation decreases with the increase of the temperature. An important contribution of this study is the in situ identification of reaction intermediates adsorbed ...


High Dynamic Range Scanning Technique, Song Zhang, Shing-Tung Yau Aug 2008

High Dynamic Range Scanning Technique, Song Zhang, Shing-Tung Yau

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Measuring objects with high surface reflectivity variations (i.e., high dynamic range) is challenging for any optical method. This paper addresses a high dynamic range scanning (HDRS) technique that can measure this type of objects. It takes advantage of one merit of a phase-shifting algorithm: pixel-by-pixel phase retrieval. For each measurement, multiple shots of fringe images with different exposures are taken. And a sequence of fringe images with different overall brightness are captured: the brightest fringe images have good fringe quality for darker areas although the brighter areas may be saturated; while the darkest fringe images have good fringe quality ...


Virtual Reality Based Multi-Modal Teleoperation Using Mixed Autonomy, Muthukkumar S. Kadavasal, Abhishek Seth, James H. Oliver Aug 2008

Virtual Reality Based Multi-Modal Teleoperation Using Mixed Autonomy, Muthukkumar S. Kadavasal, Abhishek Seth, James H. Oliver

Mechanical Engineering Conference Presentations, Papers, and Proceedings

A multi modal teleoperation interface is introduced featuring an integrated virtual reality based simulation augmented by sensors and image processing capabilities on-board the remotely operated vehicle. The proposed virtual reality interface fuses an existing VR model with live video feed and prediction states, thereby creating a multi modal control interface. Virtual reality addresses the typical limitations of video-based teleoperation caused by signal lag and limited field of view thereby allowing the operator to navigate in a continuous fashion. The vehicle incorporates an on-board computer and a stereo vision system to facilitate obstacle detection. A vehicle adaptation system with a priori ...


Simultaneous Geometry And Color Texture Acquisition Using A Single-Chip Color Camera, Song Zhang, Shing-Tung Yau Aug 2008

Simultaneous Geometry And Color Texture Acquisition Using A Single-Chip Color Camera, Song Zhang, Shing-Tung Yau

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Capturing 3-D geometry and the perfectly aligned color texture simultaneously is crucial for diverse fields including entertainment, target recognition, and computer graphics. However, it is very challenging for a conventional technique because of a number of problems related to color. Previous researchers rely heavily on using two cameras: a black-and-white(B/W) camera to measure the geometry, and a color camera to capture the color texture. However, aligning the color image with the 3-D geometry point by point remains difficult. In this research, we propose a novel technique that uses a single-chip color camera to capture both geometry and color ...


Structure And Properties Of (1-X)Pb(Mg1/2w1/2)O3–Xpb(Zr0.5ti0.5)O3 Solid Solution Ceramics, D. White, X. Zhao, Matthew F. Besser, Xiaoli Tan Aug 2008

Structure And Properties Of (1-X)Pb(Mg1/2w1/2)O3–Xpb(Zr0.5ti0.5)O3 Solid Solution Ceramics, D. White, X. Zhao, Matthew F. Besser, Xiaoli Tan

Materials Science and Engineering Publications

The widely used piezoelectric Pb(Zr1−x Ti x )O3 ceramics have been known to have Zr4+ and Ti4+ randomly distributed on the B-site lattice in the ABO3 perovskite structure. In this study, we attempted to develop long range 1:1 B-site cation order by forming the solid solution of (1 − x)Pb(Mg1/2W1/2)O3xPb(Zr0.5Ti0.5)O3 (x ≥ 0.60). High temperature X-ray diffraction tests indicate that the cation order is embedded in the structural order. The solid solution ceramics appear ...


Experimental And Numerical Investigations On Microcoining Of Stainless Steel 304, Gap-Yong Kim, Muammer Koç, Jun Ni Jul 2008

Experimental And Numerical Investigations On Microcoining Of Stainless Steel 304, Gap-Yong Kim, Muammer Koç, Jun Ni

Mechanical Engineering Publications

Increasing demands for miniature metallic parts have driven the application of microforming in various industries. Only a limited amount of research is, however, available on the forming of miniature features in high strength materials. This study investigated the forming of microfeatures in Type 304 stainless steel by using the coining process. Experimental work was performed to study the effects of workpiece thickness, preform shape, grain size, and feature size on the formation of features ranging from 320μmto800μm. It was found that certain preform shapes enhance feature formation by allowing a favorable flow of the bulk material. In addition, a flow ...


Abstracts, Review Of Progress In Quantitative Nondestructive Evaluation (Chicago, Il, July 20–25, 2008), Center For Nondestructive Evaluation, Iowa State University Jul 2008

Abstracts, Review Of Progress In Quantitative Nondestructive Evaluation (Chicago, Il, July 20–25, 2008), Center For Nondestructive Evaluation, Iowa State University

Review of Progress in Quantitative Nondestructive Evaluation

Abstracts of papers presented at the 2008 Review of Progress in Quantitative Nondestructive Evaluation (QNDE) conference held in Chicago, Illinois from July 20–25, 2008.


Inverse Dynamic Equilibrium Analysis Of Mechanical Systems Undergoing Prescribed Rotational Motions, Dong Hwan Choi, Jonathan A. Wickert Jul 2008

Inverse Dynamic Equilibrium Analysis Of Mechanical Systems Undergoing Prescribed Rotational Motions, Dong Hwan Choi, Jonathan A. Wickert

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Mechanical systems that undergo prescribed rotational motions arise in such engineered systems as robots, spacecraft, propulsion and power generation systems, and certain sensors and actuators. In order to avoid the resonance or the critical speed of the system and to keep the desired dynamic equilibrium state in the mechanical system undergoing rotational motions, the system’s design parameter values or driving angular speed should be tuned. In this work, a general formulation for the inverse dynamic equilibrium analysis is developed to directly calculate the driving angular speed or design parameter values which satisfy the condition of the desired dynamic equilibrium ...


Zr-Modified Pb(Mg1/3nb2/3)O3 With A Long-Range Cation Order, Xiaohui Zhao, Weiguo Qu, Xiaoli Tan Jul 2008

Zr-Modified Pb(Mg1/3nb2/3)O3 With A Long-Range Cation Order, Xiaohui Zhao, Weiguo Qu, Xiaoli Tan

Materials Science and Engineering Publications

The 1:1 structural order and B-site cation order in Pb(Mg1/3Nb2/3)O3 ceramics was significantly enhanced by Zr4+ substituting Nb5+ according to the chemical formula Pb(Mg1/3Zr2x/3Nb2(1−x)/3)O3−x/3. The enhanced structural and cation order was revealed by both X-ray diffraction and transmission electron microscopy. The increased charge difference and the introduced oxygen vacancies were suggested to account for the observed long-range cation order. Typical relaxor ferroelectric behavior was retained even in the ceramics with a high degree ...


On Brownian Dynamics Simulation Of Nanoparticle Aggregation, Sergiy Markutsya, Shankar Subramaniam, R. Dennis Vigil, Rodney O. Fox May 2008

On Brownian Dynamics Simulation Of Nanoparticle Aggregation, Sergiy Markutsya, Shankar Subramaniam, R. Dennis Vigil, Rodney O. Fox

Mechanical Engineering Publications

Accurate simulation and control of nanoparticle aggregation in chemical reactors requires that population balance equations be solved by using realistic expressions for aggregation and breakage rate kernels. Obtaining such expressions requires that atomistic simulation approaches that can account for microscopic details of particle collisions be used. In principle, molecular dynamics simulations can provide the needed microscopic information, but because of the separation in length scales between the aggregates and solvent molecules, such simulations are too costly. Brownian dynamics simulations provide an alternative to the molecular dynamics approach for simulation of particle aggregation, but there has been no systematic attempt to ...


Improved Method Of Co2 Laser Cutting Of Aluminum Nitride, Raathai Molian, Pranav Shrotriya, Pal Molian May 2008

Improved Method Of Co2 Laser Cutting Of Aluminum Nitride, Raathai Molian, Pranav Shrotriya, Pal Molian

Mechanical Engineering Publications

The traditional “evaporation∕melt and blow” mechanism of CO2 laser cutting of aluminum nitride (AlN) chip carriers and heat sinks suffers from energy losses due to its high thermal conductivity, formation of dross, decomposition to aluminum, and uncontrolled thermal cracking. In order to overcome these limitations, a thermochemical method that uses a defocused laser beam to melt a thin layer of AlN surface in oxygen environment was utilized. Subsequent solidification of the melt layer generated shrinkage and thermal gradient stresses that, in turn, created a crack along the middle path of laser beam and caused material separation through unstable crack ...


Fabrication Of High Aspect Ratio Porous Microfeatures Using Hot Compaction Technique, Peng Chen, Gap-Yong Kim, Jun Ni May 2008

Fabrication Of High Aspect Ratio Porous Microfeatures Using Hot Compaction Technique, Peng Chen, Gap-Yong Kim, Jun Ni

Mechanical Engineering Publications

High aspect ratio porous microfeatures are becoming more important in the modern industry. However, the fabrication of such features under a mass production environment remains a challenge when robustness, cost effectiveness, and high productivity requirements are required. In this study, the forming of such porous microfeatures using hot compaction was investigated. A hot compaction experimental setup was designed and fabricated that is capable of performing high temperature operation (700°C), quick heatup, and avoiding oxidation. 3D thermal simulation of the experimental setup was conducted to investigate the heat transfer performance and internal temperature distribution, which was then used as a ...


Three-Dimensional Data Merging Using Holoimage, Song Zhang, Shing-Tung Yau Mar 2008

Three-Dimensional Data Merging Using Holoimage, Song Zhang, Shing-Tung Yau

Song Zhang

Three-dimensional data merging is vital for full-field three-dimensional (3D) shape measurement. All 3D range data patches, acquired from either different sensors or the same sensor in different viewing angles, have to be merged into a single piece to facilitate future data analysis. A novel method for 3D data merging using Holoimage is proposed. Similar to the 3D shape measurement system using a phase-shifting method, Holoimage is a phase-shifting–based computer synthesized fringe image. The 3D information is retrieved from Holoimage using a phase-shifting method. If two patches of 3D data with overlapping areas are rendered by OpenGL, the overlapping areas ...