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2008

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Full-Text Articles in Mechanical Engineering

Dynamic Properties Of Railway Track And Its Components : A State-Of-The-Art Review, Sakdirat Kaewunruen, Alexander Remennikov Dec 2008

Dynamic Properties Of Railway Track And Its Components : A State-Of-The-Art Review, Sakdirat Kaewunruen, Alexander Remennikov

Faculty of Engineering - Papers (Archive)

Recent findings indicate one of major causes of damages, which is attributed to the resonant behaviours, in a railway track and its components. Basically, when a railway track is excited to generalised dynamic loading, the railway track deforms and then vibrates for certain duration. Dynamic responses of the railway track and its components are the key to evaluate the structural capacity of railway track and its components. If a dynamic loading resonates the railway track’s dynamic responses, its components tend to have the significant damage from excessive dynamic stresses. For example, a rail vibration could lead to defects in ...


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.


Hydraulic Actuated Automotive Cooling Systems - Nonlinear Control And Test, John Wagner, M H. Salah, P M. Frick, D M. Dawson Dec 2008

Hydraulic Actuated Automotive Cooling Systems - Nonlinear Control And Test, John Wagner, M H. Salah, P M. Frick, D M. Dawson

Publications

The replacement of traditional automotive mechanical cooling system components with computer controlled servo-motor driven actuators can improve temperature tracking and reduce parasitic losses. The integration of hydraulic actuators in the engine cooling circuit offers greater power density in a smaller package space when compared with electric actuators. In this paper, a comprehensive nonlinear backstepping robust control technique is developed to regulate the engine coolant temperature by controlling a hydraulic coolant pump and radiator fan. An experimental test bench has been assembled to investigate the hydraulic automotive thermal system performance. Representative numerical and experimental results are presented and discussed. Overall, the ...


Edge-Stress Induced Warping Of Graphene Sheets And Nanoribbons, Ashwin Ramasubramaniam, Y. Zhang, C. Reddy, V. Shenoy Dec 2008

Edge-Stress Induced Warping Of Graphene Sheets And Nanoribbons, Ashwin Ramasubramaniam, Y. Zhang, C. Reddy, V. Shenoy

Mechanical and Industrial Engineering Faculty Publication Series

We show that edge stresses introduce intrinsic ripples in freestanding graphene sheets even in the absence of any thermal effects. Compressive edge stresses along zigzag and armchair edges of the sheet cause out-of-plane warping to attain several degenerate mode shapes. Based on elastic plate theory, we identify scaling laws for the amplitude and penetration depth of edge ripples as a function of wavelength. We also demonstrate that edge stresses can lead to twisting and scrolling of nanoribbons as seen in experiments. Our results underscore the importance of accounting for edge stresses in thermal theories and electronic structure calculations for freestanding ...


An Object-Oriented Approach For Modeling And Simulation Of Crack Growth In Cyclically Loaded Structures, D. Cojocaru, Anette M. Karlsson Dec 2008

An Object-Oriented Approach For Modeling And Simulation Of Crack Growth In Cyclically Loaded Structures, D. Cojocaru, Anette M. Karlsson

Mechanical Engineering Faculty Publications

We present an object-oriented modeling frame for simulating crack propagation due to cyclic loadings. Central to the approach is that the crack propagates when a user-defined propagation criterion is fulfilled, i.e., the crack propagation rate is not prescribed but predicted. The approach utilizes the commercial finite element software package ABAQUS and its associated Python based scripting interface. The crack propagation is simulated by a generalized node release technique. If the propagation criteria are satisfied in the end of a cycle, the crack is allowed to propagate. The incremental crack growth is inferred from an iterative investigation of the propagation ...


Experiments And Models For The Thermal Response Of Railroad Tapered-Roller Bearings, Constantine M. Tarawneh, Kevin D. Cole, Brent M. Wilson, Fadi Alnaimat Dec 2008

Experiments And Models For The Thermal Response Of Railroad Tapered-Roller Bearings, Constantine M. Tarawneh, Kevin D. Cole, Brent M. Wilson, Fadi Alnaimat

Mechanical & Materials Engineering Faculty Publications

The need to understand and quantify the heat transfer paths within tapered-roller bearings is of great importance in the railroad industry since bearing cup temperature measurement is the primary tool utilized in the removal of distressed bearings from service. Experiments were performed to acquire temperature histories at several locations on a stationary bearing subjected to heat sources imbedded in two rollers. The experimental results were compared to zero- and first-order thermal models to estimate overall heat transfer coefficients from the bearing. The results presented here can be used to explain some of the mechanisms that lead to overheating of tapered-roller ...


Predicting Young’S Modulus Of Nanowires From First-Principles Calculations On Their Surface And Bulk Materials, Guofeng Wang, Xiaodong Li Dec 2008

Predicting Young’S Modulus Of Nanowires From First-Principles Calculations On Their Surface And Bulk Materials, Guofeng Wang, Xiaodong Li

Faculty Publications

Using the concept of surface stress, we developed a model that is able to predict Young’s modulus of nanowires as a function of nanowire diameters from the calculated properties of their surface and bulk materials. We took both equilibrium strain effect and surface stress effect into consideration to account for the geometric size influence on the elastic properties of nanowires. In this work, we combined first-principles density functional theory calculations of material properties with linear elasticity theory of clamped-end three-point bending. Furthermore, we applied this computational approach to Ag, Au, and ZnOnanowires. For both Ag and Aunanowires, our theoretical ...


Detection Of Voids In Prestressed Concrete Bridges Using Thermal Imaging And Ground-Penetrating Radar, David G. Pollock, Kenneth J. Dupuis, Benjamin Lacour, Karl R. Olsen Dec 2008

Detection Of Voids In Prestressed Concrete Bridges Using Thermal Imaging And Ground-Penetrating Radar, David G. Pollock, Kenneth J. Dupuis, Benjamin Lacour, Karl R. Olsen

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Thermal imaging and ground-penetrating radar was conducted on concrete specimens with simulated air voids. For the thermal imaging inspections, six concrete specimens were constructed during the month of June 2007 to simulate the walls of post-tensioned box girder bridges. The objective was to detect simulated air voids within grouted post-tensioning ducts, thus locating areas where the post-tensioning steel strands are vulnerable to corrosion. The most important deduction taken from these inspections was that PT-ducts and simulated voids were more detectable in the 20 cm (8 in.) thick specimens than in the 30 cm (12 in.) thick specimens. While inspections of ...


Dynamic Responses Of Marine Risers/Pipes Transporting Fluid Subject To Top End Excitations, J. Leklong, S. Chucheepsakul, S. Kaewunruen Nov 2008

Dynamic Responses Of Marine Risers/Pipes Transporting Fluid Subject To Top End Excitations, J. Leklong, S. Chucheepsakul, S. Kaewunruen

Faculty of Engineering - Papers (Archive)

This paper deals with the dynamic responses to top end excitation of marine risers/pipes conveying internal fluid. The marine riser is often used as a flexible link between undersea bore head and subsurface offshore platform. The tidal waves and the changes of sea level consistently excite its top end connected to a floating vessel. In order to carry out the performance-based design of the marine risers, the evaluation of their dynamic responses to top end excitations is imperative. In this study, the marine riser is simulated using twodimensional beam elements. Energy functional of the marine risers conveying fluids is ...


Micromechanics Model Based On The Nanostructure Of Pfsa Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson, William B. Johnson, Simon Cleghorn Nov 2008

Micromechanics Model Based On The Nanostructure Of Pfsa Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson, William B. Johnson, Simon Cleghorn

Mechanical Engineering Faculty Publications

A micromechanics model is developed to predict Young’s modulus of perfluorosulfonic acid (PFSA) membranes at various temperatures and water contents. The morphology of PFSA membranes is characterized by a two-phase structure, where hydrophilic clusters expand to hold water molecules during swelling, whereas the hydrophobic polymer network maintains the structural stability. A representative volume element (RVE) is proposed based on the descriptions for the nanostructure of PFSA membranes available in the literature. On the basis of mechanics model, we estimate Young’s modulus in tension of PFSA membranes as a function of water volume fraction for various temperatures. The results ...


Modified Predator-Prey (Mpp) Algorithm For Single-And Multi-Objective Optimization Problems, Souma Chowdhury Nov 2008

Modified Predator-Prey (Mpp) Algorithm For Single-And Multi-Objective Optimization Problems, Souma Chowdhury

FIU Electronic Theses and Dissertations

The aim of this work is to develop an algorithm that can solve multidisciplinary design optimization problems. In predator-prey algorithm, a relatively small number of predators and a much larger number of prey are randomly placed on a two dimensional lattice with connected ends. The predators are partially or completely biased towards one or more objectives, based on which each predator kills the weakest prey in its neighborhood. A stronger prey created through evolution replaces this prey. In case of constrained problems, the sum o f constraint violations serves as an additional objective.

Modifications of the basic predator-prey algorithm have ...


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 ...


Drop Impact Dynamic Response Study Of Jedec Jesd22-B111 Test Board, Michael Krist, Jianbiao Pan, Andrew Farris, Nicolas Vickers Nov 2008

Drop Impact Dynamic Response Study Of Jedec Jesd22-B111 Test Board, Michael Krist, Jianbiao Pan, Andrew Farris, Nicolas Vickers

Industrial and Manufacturing Engineering

Mobile and handheld electronic devices are prone to being dropped. This drop event may result in failure of solder joints inside these devices. The need for RoHS compliant boards coupled with the demand for reliable electronics has resulted in the development of the JEDEC Standard JESD22-B111 to standardize the method of drop testing surface mount electronic components. However, there has been little study on the effects of additional mass on the board and rigidity of the board on drop test reliability. This paper examines the drop impact dynamic responses of the JEDEC JESD22-B111 board. Of interest are the effects of ...


The Effect Of Ultrasonic Frequency On Gold Wire Bondability And Reliability, Jianbiao Pan, Minh-Nhat Le, Cuong Van Pham Nov 2008

The Effect Of Ultrasonic Frequency On Gold Wire Bondability And Reliability, Jianbiao Pan, Minh-Nhat Le, Cuong Van Pham

Industrial and Manufacturing Engineering

This paper presents a systematic study on the effect of 120KHz ultrasonic frequency on the bondability and reliability of fine pitch gold wire bonding. The study was carried out on a thermosonic ball bonder that is allowed to easily switch between ultrasonic frequency of 60KHz and 120 KHz by changing the ultrasonic transducer and the ultrasonic generator. Bonding parameters were optimized through design of experiment methodology for four different cases: 25.4 μm wire at 60 kHz, 25.4 μm wire at 120 kHz, 17.8 μm wire at 60 kHz, and 17.8 μm wire at 120 kHz. The ...


Board Level Failure Analysis Of Chip Scale Package Drop Test Assemblies, Nicholas Vickers, Kyle Rauen, Andrew Farris, Jianbiao Pan Nov 2008

Board Level Failure Analysis Of Chip Scale Package Drop Test Assemblies, Nicholas Vickers, Kyle Rauen, Andrew Farris, Jianbiao Pan

Industrial and Manufacturing Engineering

This paper presents the failure analysis results of board level drop tests. In this study, the test vehicle was designed according to the requirements of the Joint Electron Device Engineering Council (JEDEC) drop test board. The test vehicle was assembled with 15 chip scale packages (CSPs) each having 228 daisy-chained 0.5 mm pitch solder joints using Sn-3.0 wt% Ag-0.5 wt% Cu (SAC305) lead free solder. Assemblies were drop tested using three different peak accelerations of 900 G, 1500 G, 2900 G, with 0.7 ms, 0.5 ms, and 0.3 ms pulse durations, respectively. Scanning electron ...


Image Analyses Of Two Crustacean Exoskeletons And Implications Of The Exoskeletal Microstructure On The Mechanical Behavior, Liang Cheng, Liyun Wang, Anette M. Karlsson Nov 2008

Image Analyses Of Two Crustacean Exoskeletons And Implications Of The Exoskeletal Microstructure On The Mechanical Behavior, Liang Cheng, Liyun Wang, Anette M. Karlsson

Mechanical Engineering Faculty Publications

The microstructures of exoskeletons from Homarus americanus (American lobster) and Callinectes sapidus (Atlantic blue crab) were investigated to elucidate the mechanical behavior of such biological composites. Image analyses of the cross-sectioned exoskeletons showed that the two species each have three well-defined regions across the cuticle thickness where the two innermost regions (exocuticle and endocuticle) are load bearing. These regions consist of mineralized chitin fibers aligned in layers, where a gradual rotation of the fiber orientation of the layers results in repeating stacks. The exocuticle and endocuticle of the two species have similar morphology, but different thicknesses, number of layers, and ...


A Plasma Model Combined With An Improved Two-Temperature Equation For Ultrafast Laser Ablation Of Dielectrics, Lan Jiang, Hai-Lung Tsai Nov 2008

A Plasma Model Combined With An Improved Two-Temperature Equation For Ultrafast Laser Ablation Of Dielectrics, Lan Jiang, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

It remains a big challenge to theoretically predict the material removal mechanism in femtosecond laser ablation. To bypass this unresolved problem, many calculations of femtosecond laser ablation of nonmetals have been based on the free electron density distribution without the actual consideration of the phase change mechanism. However, this widely used key assumption needs further theoretical and experimental confirmation. by combining the plasma model and improved two-temperature model developed by the authors, this study focuses on investigating ablation threshold fluence, depth, and shape during femtosecond laser ablation of dielectrics through nonthermal processes (the Coulomb explosion and electrostatic ablation). The predicted ...


Real-Time Vertical Track Deflection Measurement System, Sheng Lu Nov 2008

Real-Time Vertical Track Deflection Measurement System, Sheng Lu

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

Track quality is a major factor in railroad safety, and one accepted indicator of track quality is the vertical track deflection. Measuring track deflection from a moving railcar is difficult because there is no stable reference for the measurements. A system developed by researchers at the University of Nebraska to measure track deflection from a moving railcar in real-time is described in detail. The system consists of a loaded hopper with a camera/laser sensor system to detect the vertical deflection of the rail relative to the wheel/rail contact point. Modeling and simulation of the system is also presented ...


Flush-Mounted Steady-Periodic Heated Film With Application To Shear-Stress Measurement, Kevin D. Cole Nov 2008

Flush-Mounted Steady-Periodic Heated Film With Application To Shear-Stress Measurement, Kevin D. Cole

Mechanical & Materials Engineering Faculty Publications

Surface-mounted heated films have been used for fluid-flow measurement for many years. Recently unsteady heating of such surface films has been explored experimentally. In this paper steady-periodic heating of a surface-mounted film is studied analytically. Wall effects and axial heat conduction in the fluid are included. The temperature is found as an exact integral expression constructed from separate Green’s function formulations in the fluid flow and in the solid wall that are matched at the fluid-solid interface. Results for temperature, obtained by quadrature, are reported for several flow speeds and several steady-periodic frequencies. The results show that steady-periodic heating ...


Three-Dimensional Modeling Of The Plasma Arc In Arc Welding, Gu Xu, J. Hu, Hai-Lung Tsai Nov 2008

Three-Dimensional Modeling Of The Plasma Arc In Arc Welding, Gu Xu, J. Hu, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell's equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such ...


Progress Toward Meeting The Challenges Of Our Coastal Urban Future, Juile Pullen, Jason Ching, David J. Sailor, William Thompson, Bob Bornstein, Darko Koracin Nov 2008

Progress Toward Meeting The Challenges Of Our Coastal Urban Future, Juile Pullen, Jason Ching, David J. Sailor, William Thompson, Bob Bornstein, Darko Koracin

Mechanical and Materials Engineering Faculty Publications and Presentations

The article provides information on the Seventh Conference on Coastal Atmospheric and Oceanic Prediction and Processes, and the Seventh Symposium on the Urban Environment in San Diego, California on September 9-13, 2008. Topics include the heterogeneity of urban areas, coastal vulnerabilities, urban planning, and emergency response modeling. The conference featured several speakers including Walter Dabberdt and James Voogt.


Localised Galvanic Corrosion Processes In Thermal Spray Coated/Cast Aluminium Alloy Systems, David Culliton, Tony Betts, David Kennedy Nov 2008

Localised Galvanic Corrosion Processes In Thermal Spray Coated/Cast Aluminium Alloy Systems, David Culliton, Tony Betts, David Kennedy

Conference Papers

Cast Aluminium Alloys, because of the propensity of aluminium to react with impurities and alloying elements, are prone to developing IM impurities during the solidification process. These IM phases can act, in some fluids, as initiation sites for localised corrosion processes, resulting in degradation phenomena, such as pitting. Whilst Thermal Spray coatings can improve the wear resistance of Cast Aluminium Alloys, their corrosion performance may be hampered by the presence of through porosity within the coating.

The present work details some preliminary studies of the localised corrosion processes occurring at the interface area between a Thermal Spray coating and a ...


Work In Progress - Enhancing Student-Learning Through State-Of-The-Art Systems Level Design And Implementation, Albert A. Liddicoat, Jianbiao Pan, James G. Harris, Dominic J. Dal Bello, Lynne A. Slivovsky Oct 2008

Work In Progress - Enhancing Student-Learning Through State-Of-The-Art Systems Level Design And Implementation, Albert A. Liddicoat, Jianbiao Pan, James G. Harris, Dominic J. Dal Bello, Lynne A. Slivovsky

Industrial and Manufacturing Engineering

The curriculum for undergraduate engineering programs is often partitioned into several courses that are taught in isolation followed by a single culminating senior design or capstone project experience. In the senior design class students being to synthesize the knowledge and skills that they acquired through the engineering curriculum. This paper presents lower and upper division course and curricular changes made to accommodate learning objectives that better prepare students for project-based learning. These learning experiences and skills include: systems level design, experience with state-of-the-art Computer Aided Design (CAD) tools, printed circuit board (PBC) design, design for manufacturability, electronics assembly, project management ...


Contact-Resonance Atomic Force Microscopy For Viscoelasticity, P. A. Yuya, D. C. Hurley, Joseph A. Turner Oct 2008

Contact-Resonance Atomic Force Microscopy For Viscoelasticity, P. A. Yuya, D. C. Hurley, Joseph A. Turner

Faculty Publications from the Department of Engineering Mechanics

We present a quantitative method for determining the viscoelastic properties of materials with nanometer spatial resolution. The approach is based on the atomic force acoustic microscopy technique that involves the resonant frequencies of the atomic force microscopy cantilever when its tip is in contact with a sample surface. We derive expressions for the viscoelastic properties of the sample in terms of the cantilever frequency response and damping loss. We demonstrate the approach by obtaining experimental values for the storage and loss moduli of a poly(methyl methacrylate) film using a polystyrene sample as a reference material. Experimental techniques and system ...


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 ...


A Variational Shape Optimization Approach For Image Segmentation With A Mumford-Shah Functional, Günay Doğam, Pedro Morin, Ricardo H. Nochetto Oct 2008

A Variational Shape Optimization Approach For Image Segmentation With A Mumford-Shah Functional, Günay Doğam, Pedro Morin, Ricardo H. Nochetto

Departmental Papers (MEAM)

We introduce a novel computational method for a Mumford–Shah functional, which decomposes a given image into smooth regions separated by closed curves. Casting this as a shape optimization problem, we develop a gradient descent approach at the continuous level that yields nonlinear PDE flows. We propose time discretizations that linearize the problem and space discretization by continuous piecewise linear finite elements. The method incorporates topological changes, such as splitting and merging for detection of multiple objects, space–time adaptivity, and a coarse-to-fine approach to process large images efficiently. We present several simulations that illustrate the performance of the method ...


Alternative Binder Carbide Tools For Machining Superalloys, Daniel J. Waldorf, Michael Stender, Scott Liu, Daniel Norgan Oct 2008

Alternative Binder Carbide Tools For Machining Superalloys, Daniel J. Waldorf, Michael Stender, Scott Liu, Daniel Norgan

Industrial and Manufacturing Engineering

This study examines the performance of a new class of wear-resistant but economical cutting tools produced by varying the binder composition of standard cemented carbide composites. By replacing some or all of the cobalt binder with rhenium and nickel-based superalloy, a stronger composite tool results, potentially capable of machining heat-resistant superalloys at significantly higher cutting speeds. Sample tools with alternative binder were produced and compared to standard tools bound with cobalt only. Turning experiments on Inconel 718 were run to evaluate wear resistance and tool life for several grades. The experimentation also examined the effects of varying the relative proportions ...


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.