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Mechanical Engineering Faculty Research

2013

Articles 1 - 13 of 13

Full-Text Articles in Mechanical Engineering

Measurement Of Adhesion Energy Of Electrospun Polymer Membranes Using A Shaft-Loaded Blister Test, Shing Chung Josh Wong, Haining Na, Pei Chen Jun 2013

Measurement Of Adhesion Energy Of Electrospun Polymer Membranes Using A Shaft-Loaded Blister Test, Shing Chung Josh Wong, Haining Na, Pei Chen

Mechanical Engineering Faculty Research

This study aims to examine the adhesion work of electrospun polymer nano- and micro-fibers. The adhesion energy at the interface of electrospun membrane and a rigid substrate is characterized by a shaft-loaded blister test (SLBT). By controlling the processing parameters, polyvinylidene fluoride (PVDF) fibrous membranes are prepared with fiber diameters ranging from 201 ± 86 nm to 2,724 ± 587 nm. The adhesion energy between electrospun membrane and rigid substrate increases from 8.1 ± 0.7 mJ/m2 to 258.8 ± 43.5 mJ/m2 by use of smaller fiber diameters. Adhesion energies between electrospun PVDF membranes and SiC substrates made of different grain …

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Polymer Fiber Arrays For Adhesion, Shing Chung Josh Wong, Johnny F. Najem, Guang Ji, Shuwen Chen Jun 2013

Polymer Fiber Arrays For Adhesion, Shing Chung Josh Wong, Johnny F. Najem, Guang Ji, Shuwen Chen

Mechanical Engineering Faculty Research

The ability of geckos to adhere to vertical solid surfaces comes from their remarkable feet with millions of projections terminating in nanometer spatulae. In this paper, we present a simple yet robust method for fabricating directionally sensitive dry adhesives. By using electrospun nylon 6 nanofiber arrays, we create gecko-inspired dry adhesives, that are electrically insulating, and that show shear adhesion strength of 27 N/cm2 on a glass slide. This measured value is 270% that reported of gecko feet and 97-fold above normal adhesion strength of the same arrays. The data indicate a strong shear binding-on and easy normal lifting-off. Size …

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A Mechanism-Based Approach For Predicting Ductile Fracture Of Metallic Alloys, Xiaosheng Gao Jun 2013

A Mechanism-Based Approach For Predicting Ductile Fracture Of Metallic Alloys, Xiaosheng Gao

Mechanical Engineering Faculty Research

Ductile fracture in metallic alloys often follows a multi-step failure process involving void nucleation, growth and coalescence. Because of the difference in orders of magnitude between the size of the finite element needed to resolve the microscopic details and the size of the engineering structures, homogenized material models, which exhibits strain softening, are often used to simulate the crack propagation process. Various forms of porous plasticity models have been developed for this purpose. Calibration of these models requires the predicted macroscopic stress-strain response and void growth behavior of the representative material volume to match the results obtained from detailed finite …

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A Preliminary Discourse On Adhesion Of Nanofibers Derived From Electrospun Polymers, Pei Chen May 2013

A Preliminary Discourse On Adhesion Of Nanofibers Derived From Electrospun Polymers, Pei Chen

Mechanical Engineering Faculty Research

To bio-mimic gecko’s foot hair, which possess high adhesion strength and can be re- usable for lifetime, fibrous membranes are fabricated by electrospinning to provide sufficient adhesion energy. Shaft-loaded blister test (SLBT) is firstly used to measure the work of adhesion between electrospun membrane and rigid substrate. Poly(vinylidene fluoride) (PVDF) were electrospun with an average fiber diameter of 333±59 nm. Commercial cardboard with inorganic coating was used to provide a model substrate for adhesion tests. In SLBT, the elastic response PVDF was analyzed and its adhesion energy measured. FEA model with cohesive layer is developed to evaluate the experiment results. …

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Adaptive Human Control Gains During Precision Grip, Erik D. Engeberg Mar 2013

Adaptive Human Control Gains During Precision Grip, Erik D. Engeberg

Mechanical Engineering Faculty Research

Eight human test subjects attempted to track a desired position trajectory with an instrumented manipulandum (MN). The test subjects used the MN with three different levels of stiffness. A transfer function was developed to represent the human application of a precision grip from the data when the test subjects initially displaced the MN so as to learn the position mapping from the MN onto the display. Another transfer function was formed from the data of the remainder of the experiments, after significant displacement of the MN occurred. Both of these transfer functions accurately modelled the system dynamics for a portion …

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Mechanical Behavior Of A Magnesium Alloy Nanocomposite Under Conditions Of Static Tension And Dynamic Fatigue, T. S. Srivatsan, C. Godbole, T. Quick, M. Paramsothy, M. Gupta Feb 2013

Mechanical Behavior Of A Magnesium Alloy Nanocomposite Under Conditions Of Static Tension And Dynamic Fatigue, T. S. Srivatsan, C. Godbole, T. Quick, M. Paramsothy, M. Gupta

Mechanical Engineering Faculty Research

In this paper, the intrinsic influence of nano-alumina particulate (Al2O3p) reinforcements on microstructure, microhardness, tensile properties, tensile fracture, cyclic stress-controlled fatigue, and final fracture behavior of a magnesium alloy is presented and discussed. The unreinforced magnesium alloy (AZ31) and the reinforced composite counterpart (AZ31/1.5 vol.% Al2O3) were manufactured by solidification processing followed by hot extrusion. The elastic modulus, yield strength, and tensile strength of the nanoparticle-reinforced magnesium alloy were noticeably higher than the unreinforced counterpart. The ductility, quantified by elongation-to-failure, of the composite was observably lower than the unreinforced monolithic counterpart (AZ31). …

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Electrospun Polymeric Membranes For Adhesion, Johnny F. Najem, Shing Chung Josh Wong, Guang Ji Feb 2013

Electrospun Polymeric Membranes For Adhesion, Johnny F. Najem, Shing Chung Josh Wong, Guang Ji

Mechanical Engineering Faculty Research

With growing interest in detachable adhesives, new materials are explored such as the types that employ elastomers, thermoplastics, and pressuresensitive polymers [1]. Generally, these adhesives produce substantial shear adhesion strengths but are considerably difficult to detach from surfaces. Commercial high strength adhesives make use of chemical interactions such as glues and permanently attach two surfaces. Subsequently, fabrication of dry adhesives with anisotropic force distributions has the potential in several applications such as tapes, fasteners, treads of wall-climbing robots, spiderman's suits, microelectronics, medical and space applications. High aspect ratio (AR) structures exhibit significant shear adhesion strength compared to ones with low …

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Magnetohydrodynamic Simulations Of Hypersonic Flow Over A Cylinder Using Axial- And Transverse-Oriented Magnetic Dipoles, Andrew N. Guarendi, Abhilash J. Chandy Jan 2013

Magnetohydrodynamic Simulations Of Hypersonic Flow Over A Cylinder Using Axial- And Transverse-Oriented Magnetic Dipoles, Andrew N. Guarendi, Abhilash J. Chandy

Mechanical Engineering Faculty Research

Numerical simulations of magnetohydrodynamic (MHD) hypersonic flow over a cylinder are presented for axial- and transverse-oriented dipoles with different strengths. ANSYS CFX is used to carry out calculations for steady, laminar flows at a Mach number of 6.1, with a model for electrical conductivity as a function of temperature and pressure. The low magnetic Reynolds number (≪1) calculated based on the velocity and length scales in this problem justifies the quasistatic approximation, which assumes negligible effect of velocity on magnetic fields. Therefore, the governing equations employed in the simulations are the compressible Navier-Stokes and the energy equations with MHD-related source …

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Nonoscillatory Central Schemes For Hyperbolic Systems Of Conservation Laws In Three-Space Dimensions, Andrew N. Guarendi, Abhilash J. Chandy Jan 2013

Nonoscillatory Central Schemes For Hyperbolic Systems Of Conservation Laws In Three-Space Dimensions, Andrew N. Guarendi, Abhilash J. Chandy

Mechanical Engineering Faculty Research

We extend a family of high-resolution, semidiscrete central schemes for hyperbolic systems of conservation laws to three-space dimensions. Details of the schemes, their implementation, and properties are presented together with results from several prototypical applications of hyperbolic conservation laws including a nonlinear scalar equation, the Euler equations of gas dynamics, and the ideal magnetohydrodynamic equations. Parallel scaling analysis and grid-independent results including contours and isosurfaces of density and velocity and magnetic field vectors are shown in this study, confirming the ability of these types of solvers to approximate the solutions of hyperbolic equations efficiently and accurately.

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Coupled Continuum And Molecular Model Of Flow Through Fibrous Filter, Shunliu Zhao, Alex Povitsky Jan 2013

Coupled Continuum And Molecular Model Of Flow Through Fibrous Filter, Shunliu Zhao, Alex Povitsky

Mechanical Engineering Faculty Research

A coupled approach combining the continuum boundary singularity method (BSM) and the molecular direct simulation Monte Carlo (DSMC) is developed and validated using Taylor-Couette flow and the flow about a single fiber confined between two parallel walls. In the proposed approach, the DSMC is applied to an annular region enclosing the fiber and the BSM is employed in the entire flow domain. The parameters used in the DSMC and the coupling procedure, such as the number of simulated particles, the cell size, and the size of the coupling zone are determined by inspecting the accuracy of pressure drop obtained for …

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Physically Representative Atomistic Modeling Of Atomic-Scale Friction, Yalin Dong Jan 2013

Physically Representative Atomistic Modeling Of Atomic-Scale Friction, Yalin Dong

Mechanical Engineering Faculty Research

Nanotribology is a research field to study friction, adhesion, wear and lubrication occurred between two sliding interfaces at nano scale. This study is motivated by the demanding need of miniaturization mechanical components in Micro Electro Mechanical Systems (MEMS), improvement of durability in magnetic storage system, and other industrial applications. Overcoming tribological failure and finding ways to control friction at small scale have become keys to commercialize MEMS with sliding components as well as to stimulate the technological innovation associated with the development of MEMS. In addition to the industrial applications, such research is also scientifically fascinating because it opens a …

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Lanthanum Halide Nanoparticle Scintillators For Nuclear Radiation Detection, Paul Guss, Ronald Guise, Ding Yuan, Sanjoy Mukhopadhyay, Robert O’Brien, Daniel Robert Lowe, Zhitao Kang, Hisham Menkara, Vivek V. Nagarkar Jan 2013

Lanthanum Halide Nanoparticle Scintillators For Nuclear Radiation Detection, Paul Guss, Ronald Guise, Ding Yuan, Sanjoy Mukhopadhyay, Robert O’Brien, Daniel Robert Lowe, Zhitao Kang, Hisham Menkara, Vivek V. Nagarkar

Mechanical Engineering Faculty Research

Nanoparticles with sizesscintillators, in order to determine the viability of using scintillators employing nanostructured lanthanum trifluoride. Preliminary results of this investigation are consistent with the idea that these materials have an intrinsic response to nuclear radiation that may be correlated to the energy of the incident radiation.

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Transparent Actuator Made With Few Layer Graphene Electrode And Dielectric Elastomer, For Variable Focus Lens, Taeseon Hwang, Hyeok-Yong Kwon, Joon-Suk Oh, Jung-Pyo Hong, Seung-Chul Hong, Youngkwan Lee, Hyouk Ryeo Choi, Kwang J. Kim, Mainul Hossain Bhuiya, Jae Do Nam Jan 2013

Transparent Actuator Made With Few Layer Graphene Electrode And Dielectric Elastomer, For Variable Focus Lens, Taeseon Hwang, Hyeok-Yong Kwon, Joon-Suk Oh, Jung-Pyo Hong, Seung-Chul Hong, Youngkwan Lee, Hyouk Ryeo Choi, Kwang J. Kim, Mainul Hossain Bhuiya, Jae Do Nam

Mechanical Engineering Faculty Research

A transparent dielectric elastomer actuator driven by few-layer-graphene (FLG) electrode was experimentally investigated. The electrodes were made of graphene, which was dispersed inN-methyl-pyrrolidone. The transparent actuator was fabricated from developed FLG electrodes.The FLG electrode with its sheet resistance of 0.45 kΩ/sq (80 nm thick) was implemented to mask silicone elastomer. The developed FLG-driven actuator exhibited an optical transparency of over 57% at a wavenumber of 600 nm and produced bending displacement performance ranging from 29 to 946 μm as functions of frequency and voltage. The focus variation was clearly demonstrated under actuation to study its application-feasibility in …

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