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Articles 1 - 30 of 80
Full-Text Articles in Engineering
Tuning Of The Size And The Lattice Parameter Of Ion-Beam Synthesized Pb Nanoparticles Embedded In Si, Huan Wang, J. Cuppens, E. Biermans, S. Bals, Lucia Fernandez-Ballester, K. O. Kvashnina, W. Bras, M. J. Van Bael, K. Temst, A. Vantomme
Tuning Of The Size And The Lattice Parameter Of Ion-Beam Synthesized Pb Nanoparticles Embedded In Si, Huan Wang, J. Cuppens, E. Biermans, S. Bals, Lucia Fernandez-Ballester, K. O. Kvashnina, W. Bras, M. J. Van Bael, K. Temst, A. Vantomme
Department of Engineering Mechanics: Faculty Publications
The size and lattice constant evolution of Pb nanoparticles (NPs) synthesized by high fluence implantation in crystalline Si have been studied with a variety of experimental techniques. Results obtained from small-angle x-ray scattering showed that the Pb NPs grow with increasing implantation fluence and annealing duration. The theory of NP growth kinetics can be applied to qualitatively explain the size evolution of the Pb NPs during the implantation and annealing processes. Moreover, the lattice constant of the Pb NPs was evaluated by conventional x-ray diffraction. The lattice dilatation was observed to decrease with increasing size of the Pb NPs. Such …
Experimental Testing And Finite-Element Modeling To Evaluate The Effects Of Aggregate Angularity On Bituminous Mixture Performance, Leonardo T. Souza, Yong-Rak Kim, Flavio V. Souza, Leandro S. Castro
Experimental Testing And Finite-Element Modeling To Evaluate The Effects Of Aggregate Angularity On Bituminous Mixture Performance, Leonardo T. Souza, Yong-Rak Kim, Flavio V. Souza, Leandro S. Castro
Department of Engineering Mechanics: Faculty Publications
This study evaluates the effects of aggregate angularity in bituminous mixtures. Previous studies have predominantly focused on the effects of aggregate angularity on the resistance to permanent deformation, while little work has investigated the role of aggregate angularity related to mixture volumetrics and fatigue fracture performance. To investigate the effect of aggregate angularity on mixture performance and characteristics, five mixes with different combinations of coarse and fine aggregate angularity are evaluated by performing the uniaxial static creep test and the indirect tensile fracture energy test. The asphalt pavement analyzer test is also performed with five-year field project mixtures. Fracture energy …
Supramolecular Nanolayer Reconfiguration After Molecular Intercalation, Alexandre Dhôtel, Hui Li, Lucia Fernandez-Ballester, Laurent Delbreilh, Boulos Youssef, Xiao Cheng Zeng, Li Tan
Supramolecular Nanolayer Reconfiguration After Molecular Intercalation, Alexandre Dhôtel, Hui Li, Lucia Fernandez-Ballester, Laurent Delbreilh, Boulos Youssef, Xiao Cheng Zeng, Li Tan
Department of Engineering Mechanics: Faculty Publications
We examined the structural reconfiguration after intercalating foreign additives, that is, tetramethoxysilane (TMOS), within already formed supramolecular nanolayers of hexadecyltrimethoxysilane (HDTMS). Our experiments indicated that the newly formed interdigitated structure is a thermodynamically more stable configuration. Even after the HDTMS formed initial bilayer-by-bilayer structures, mixing of these aggregates with foreign additives at room temperature can change the original structure to a more compact configuration (i.e., interdigitated). Our MD simulations further revealed that the most favorable organization for this interdigitated stacking appears to be a formation of relatively small domains of HDTMS and TMOS molecules, supporting our proposal of a heterogeneous …
Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.
Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.
Department of Engineering Mechanics: Faculty Publications
In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as well …
Evaluation Of Biological Cell Properties Using Dynamic Indentation Measurement, Guoxin Cao, Namas Chandra
Evaluation Of Biological Cell Properties Using Dynamic Indentation Measurement, Guoxin Cao, Namas Chandra
Department of Engineering Mechanics: Faculty Publications
Viscoelastic mechanical properties of biological cells are commonly measured using atomic force microscope (AFM) dynamic indentation with spherical tips. A semiempirical analysis based on numerical simulation is built to determine the cell mechanical properties. It is shown that the existing analysis cannot reflect the accurate values of cell elastic/dynamic modulus due to the effects of substrate, indenter tip size, and cell size. Among these factors, substrate not only increases the true contact radius but also interferes the indentation stress field, which can cause the overestimation of cell moduli. Typically, the substrate effect is much stronger than the other two influences …
Dynamics Of Fibrillar Precursors Of Shishes As A Function Of Stress, Luigi Balzano, Dario Cavallo, Tim B. Van Erp, Zhe Ma, Jan-Willem Housmans, Lucia Fernandez-Ballester, Gerrit W. M. Peters
Dynamics Of Fibrillar Precursors Of Shishes As A Function Of Stress, Luigi Balzano, Dario Cavallo, Tim B. Van Erp, Zhe Ma, Jan-Willem Housmans, Lucia Fernandez-Ballester, Gerrit W. M. Peters
Department of Engineering Mechanics: Faculty Publications
Shishes are fibrillar crystallites that can be created by deforming a polymer melt. The formation of shishes takes place when flow is strong enough to stretch molecules. In the early stages, bundles of stretched molecules with pre-crystalline order form metastable precursors whose stability depends on their size and, hence, on the stress level. We find that for a specific isotactic polypropylene, close to the nominal melting point, a stress larger than 0.10 MPa leads to stable fibrillar precursors that are partially crystalline immediately after flow. On the other hand, below 0.10 MPa, the aspect ratio of precursors tends to unity …
Crack Nucleation In A Peridynamic Solid, S. A. Silling, O. Weckner, E. Askari, Florin Bobaru Ph.D.
Crack Nucleation In A Peridynamic Solid, S. A. Silling, O. Weckner, E. Askari, Florin Bobaru Ph.D.
Department of Engineering Mechanics: Faculty Publications
A condition for the emergence of a discontinuity in an elastic peridynamic body is proposed, resulting in a material stability condition for crack nucleation. The condition is derived by determining whether a small discontinuity in displacement, superposed on a possibly large deformation, grows over time. Stability is shown to be determined by the sign of the eigenvalues of a tensor field that depends only on the linearized material properties. This condition for nucleation of a discontinuity in displacement can be interpreted in terms of the dynamic stability of plane waves with very short wavelength. A numerical example illustrates that cracks …
Editorial: Advances In The Dynamics Of Granular Materials, Florin Bobaru, J. S. Chen, Joseph A. Turner
Editorial: Advances In The Dynamics Of Granular Materials, Florin Bobaru, J. S. Chen, Joseph A. Turner
Department of Engineering Mechanics: Faculty Publications
Granular materials exhibit a complex array of phenomena which makes the prediction of their behavior extremely difficult. Granular materials are strongly dissipative and show collective (heap formation, jamming) and size segregation phenomena, and can propagate surface waves. They display fluidization and convective motion, and under certain vibration regimes, they tend to mix when they would otherwise segregate, and segregate when they might otherwise mix. The wide range of behaviors that granular materials can display has been one of the main factors for which the development of predictive models has continued to remain an open problem.
The papers in this Special …
Force Chains And Resonant Behavior In Bending Of A Granular Layer On An Elastic Support, Kitti Rattanadit, Florin Bobaru, Konlayut Promratana, Joseph A. Turner
Force Chains And Resonant Behavior In Bending Of A Granular Layer On An Elastic Support, Kitti Rattanadit, Florin Bobaru, Konlayut Promratana, Joseph A. Turner
Department of Engineering Mechanics: Faculty Publications
In this paper we investigate the interaction between a granular layer and an elastic foundation using a coupled Discrete Element Method-Finite Element Method (DEM–FEM) computational model. We use this dynamics code to simulate quasi-static bending of the granular layer and we observe the changes taking place in the structure of the force chains for two cases: with and without rolling resistance. A reversal of the arches formed in the force chains leads to a bending resistance similar to that observed in dynamic experiments on resonant behavior under bending of a layer of sand in a container with an elastic bottom. …
A Model For Predicting The Multiscale Crack Growth Due To An Impact In Heterogeneous Viscoelastic Solids, Flavio V. Souza, David H. Allen
A Model For Predicting The Multiscale Crack Growth Due To An Impact In Heterogeneous Viscoelastic Solids, Flavio V. Souza, David H. Allen
Department of Engineering Mechanics: Faculty Publications
A two-scale model for predicting the multiple crack growth in viscoelastic solids due to an impact is presented. The cracks are considered only at the local scale through the use of a micromechanical viscoelastic cohesive zone model. The multiscale model has been implemented in a finite-element code. In order to minimize the computation time, the local finite-element meshes are solved in parallel by multiple processors. An example problem is given in order to demonstrate the capabilities of the model.
The Magnetoelectric Effects In Multiferroic Composite Nanofibers, C. L. Zhang, W. Q. Chen, S. H. Xie, J. S. Yang, Jiangyu Li
The Magnetoelectric Effects In Multiferroic Composite Nanofibers, C. L. Zhang, W. Q. Chen, S. H. Xie, J. S. Yang, Jiangyu Li
Department of Engineering Mechanics: Faculty Publications
In this letter, we analyze the quasistatic and dynamic magnetoelectric responses of multiferroic composite nanofibers consisting of both ferroelectric and ferromagnetic phases and demonstrate that the nanofibers exhibit magnetoelectric responses orders of magnitude higher than multiferroic composite thin films of similar compositions. The analysis suggests that the multiferroic nanofibers are promising for magnetoelectric applications.
Reduction Of Surface Acoustic Wave Resonator Normal Acceleration Sensitivity Using Piezoelectric Actuators, X. Y. Shan, Y. T. Hu, J. S. Yang
Reduction Of Surface Acoustic Wave Resonator Normal Acceleration Sensitivity Using Piezoelectric Actuators, X. Y. Shan, Y. T. Hu, J. S. Yang
Department of Engineering Mechanics: Faculty Publications
We attach a piezoelectric actuator to a surface acoustic wave resonator under normal acceleration to reduce its acceleration sensitivity. It is shown theoretically that under a given acceleration, the acceleration induced frequency shift in the resonator can be reduced or even completely eliminated when a proper electric field is applied to the piezoelectric actuator.
Harvesting Magnetic Energy Using Extensional Vibration Of Laminated Magnetoelectric Plates, C. L. Zhang, J. S Yang, W. Q. Chen
Harvesting Magnetic Energy Using Extensional Vibration Of Laminated Magnetoelectric Plates, C. L. Zhang, J. S Yang, W. Q. Chen
Department of Engineering Mechanics: Faculty Publications
Magnetically forced extensional vibrations of laminated plates with piezoelectric and piezomagnetic layers are analyzed theoretically. It is shown that such a structure can be used to harvest magnetic energy and convert it to electric energy. The output power and the energy conversion efficiency are calculated. The load dependence of the magnetoelectric coupling coefficient is also obtained.
Convergence, Adaptive Refinement, And Scaling In 1d Peridynamics, Florin Bobaru Ph.D., Mijia Yabg Ph.D., Leonardo F. Alves M.S., Stewart A. Silling Ph.D., Ebrahim Askari Ph.D., Jifeng Xu Ph.D.
Convergence, Adaptive Refinement, And Scaling In 1d Peridynamics, Florin Bobaru Ph.D., Mijia Yabg Ph.D., Leonardo F. Alves M.S., Stewart A. Silling Ph.D., Ebrahim Askari Ph.D., Jifeng Xu Ph.D.
Department of Engineering Mechanics: Faculty Publications
We introduce here adaptive refinement algorithms for the non-local method peridynamics, which was proposed (in J. Mech. Phys. Solids 2000; 48:175–209) as a reformulation of classical elasticity for discontinuities and long-range forces. We use scaling of the micromodulus and horizon and discuss the particular features of adaptivity in peridynamics for which multiscale modeling and grid refinement are closely connected. We discuss three types of numerical convergence for peridynamics and obtain uniform convergence to the classical solutions of static and dynamic elasticity problems in 1D in the limit of the horizon going to zero. Continuous micromoduli lead to optimal rates of …
Evaporation Induced Two-Dimensional Buckling Within Liquid Droplet, Ziguang Chen, Maozi Liu, Gang-Yu Liu, Li Tan
Evaporation Induced Two-Dimensional Buckling Within Liquid Droplet, Ziguang Chen, Maozi Liu, Gang-Yu Liu, Li Tan
Department of Engineering Mechanics: Faculty Publications
Evaporation of a liquid droplet containing a thin layer of surfactants atop could generate two-dimensional buckling on surfaces. Herringbone features were produced via embedded nanoparticle beds. We assign transient surface tension as the driving force for such a phenomenon. Considering the surfactant layer as a thin elastic film, a continuum model is employed to calculate the mechanical properties of the layer. Particularly, we estimated an elastic modulus of 4 GPa for the surfactant layer, indicating rather strong mechanical properties of these small molecules when they are close packed to form supramolecules via noncovalent binding.
Optimal Electrode Shape And Size For Shear Mode Thin Film Acoustic Wave Resonators, L. M. Xu, B. B. Tang, Y. T. Hu, H. Fan, J. S. Yang
Optimal Electrode Shape And Size For Shear Mode Thin Film Acoustic Wave Resonators, L. M. Xu, B. B. Tang, Y. T. Hu, H. Fan, J. S. Yang
Department of Engineering Mechanics: Faculty Publications
We study electrode shape and size for plates of hexagonal crystals or polarized ceramics with the sixfold axis or the poling direction parallel to the plate surfaces so that they can be excited into thickness-shear vibration by an electric field in the plate thickness direction. Electrode size and shape optimal in the sense that they satisfy the criterion of Bechmann’s number in every direction are determined.
Connected Vibrating Piezoelectric Bimorph Beams As A Wide-Band Piezoelectric Power Harvester, Zengtao Yang, Jiashi Yang
Connected Vibrating Piezoelectric Bimorph Beams As A Wide-Band Piezoelectric Power Harvester, Zengtao Yang, Jiashi Yang
Department of Engineering Mechanics: Faculty Publications
We analyze coupled flexural vibration of two elastically and electrically connected piezoelectric beams near resonance for converting mechanical vibration energy to electrical energy. Each beam is a so-called piezoelectric bimorph with two layers of piezoelectrics. The 1D equations for bending of piezoelectric beams are used for a theoretical analysis. An exact analytical solution to the beam equations is obtained. Numerical results based on the solution show that the two resonances of individual beams can be tuned as close as desired by design when they are connected to yield a wide-band electrical output. Therefore, the structure can be used as a …
Tem Study Of Lizardite-1t Particles In Toluene Solvent, J. Yan, Xingzhong Li, J. Y. Jiang, L. Tan
Tem Study Of Lizardite-1t Particles In Toluene Solvent, J. Yan, Xingzhong Li, J. Y. Jiang, L. Tan
Department of Engineering Mechanics: Faculty Publications
To investigate the self-assembled growth of organosilane molecules carrying Si, C and H to form multiple layers, samples were prepared in toluene and then transferred to TEM Cu grids coated with thin C films for TEM observation. It is surprising that micrometer sized flakes with a main composition of Mg and Si (or Al and Si) were occasionally observed in the TEM specimens, later were identified as lizardite-1T phase. To trace down the source of the inorganic particles, all procedures in the sample preparation were carefully checked. The particles of the lizardite-1T phase were confirmed from the organic solvent of …
Real-Time Depth Sectioning: Isolating The Effect Of Stress On Structure Development In Pressure-Driven Flow, Lucia Fernandez-Ballester, Derek W. Thurman, Julia A Kornfield
Real-Time Depth Sectioning: Isolating The Effect Of Stress On Structure Development In Pressure-Driven Flow, Lucia Fernandez-Ballester, Derek W. Thurman, Julia A Kornfield
Department of Engineering Mechanics: Faculty Publications
Transient structure development at a specific distance from the channel wall in a pressure-driven flow is obtained from a set of real-time measurements that integrate contributions throughout the thickness of a rectangular channel. This “depth sectioning method” retains the advantages of pressure-driven flow while revealing flow-induced structures as a function of stress. The method is illustrated by applying it to isothermal shear-induced crystallization of an isotactic polypropylene using both synchrotron x-ray scattering and optical retardance. Real-time, depth-resolved information about the development of oriented precursors reveals features that cannot be extracted from ex-situ observation of the final morphology and that are …
Contact-Resonance Atomic Force Microscopy For Viscoelasticity, P. A. Yuya, D. C. Hurley, Joseph A. Turner
Contact-Resonance Atomic Force Microscopy For Viscoelasticity, P. A. Yuya, D. C. Hurley, Joseph A. Turner
Department of Engineering Mechanics: Faculty Publications
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 calibration …
Impact Mechanics And High-Energy Absorbing Materials: Review, Pizhong Qiao, Mijia Yang, Florin Bobaru
Impact Mechanics And High-Energy Absorbing Materials: Review, Pizhong Qiao, Mijia Yang, Florin Bobaru
Department of Engineering Mechanics: Faculty Publications
In this paper a review of impact mechanics and high-energy absorbing materials is presented. We review different theoretical models (rigid-body dynamics, elastic, shock, and plastic wave propagation, and nonclassical or nonlocal models. and computational methods (finite-element, finite-difference, and mesh-free methods. used in impact mechanics. Some recent developments in numerical simulation of impact (e.g., peridynamics) and new design concepts proposed as high energy absorbing materials (lattice and truss structures, hybrid sandwich composites, metal foams, magnetorheological fluids, porous shape memory alloys. are discussed. Recent studies on experimental evaluation and constitutive modeling of strain rate-dependent polymer matrix composites are also presented. Impact damage …
Phase-Field Modeling Of The Formation Of Lamellar Nanostructures In Diblock Copolymer Thin Films Under Inplanar Electric Fields, Xiang-Fa Wu, Yuris A. Dzenis
Phase-Field Modeling Of The Formation Of Lamellar Nanostructures In Diblock Copolymer Thin Films Under Inplanar Electric Fields, Xiang-Fa Wu, Yuris A. Dzenis
Department of Engineering Mechanics: Faculty Publications
Recent experiments show that external inplanar electric field can be employed to guide the molecular self-assembly in diblock copolymer (BCP) thin films to form lamellar nanostructures with potential applications in nanotechnology. We study this self-assembly process through a detailed coarse-grained phase separation modeling. During the process, the free energy of the BCP films is modeled as the Ginzburg-Landau free energy with nonlocal interaction and electrostatic coupling. The resulting Cahn-Hilliard (CH) equation is solved using an efficient semi-implicit Fourier-spectral algorithm. Numerical results show that the morphology of order parameter formed in either symmetric or asymmetric BCP thin films is strongly influenced …
Free-Edge Stresses And Progressive Cracking In Surface Coatings Of Circular Torsion Bars, Xiang-Fa Wu, Yuris A. Dzenis, Kyle W. Strabala
Free-Edge Stresses And Progressive Cracking In Surface Coatings Of Circular Torsion Bars, Xiang-Fa Wu, Yuris A. Dzenis, Kyle W. Strabala
Department of Engineering Mechanics: Faculty Publications
This paper considers the explicit solutions of free-edge stresses near circumferential cracks in surface coatings of circular torsion bars and their application in determining the progressive cracking density in the coating layers. The problem was formulated within the framework of linear elastic fracture mechanics (LEFM). The free-edge stresses near crack tip and the shear stresses in the cross-section of the torsion bar were approached in explicit forms based on the variational principle of complementary strain energy. Criterion for progressive cracking in the coating layer was established in sense of strain energy conservation, and the crack density is thereby estimated. Effects …
Influence Of Spatial Correlation Function On Attenuation Of Ultrasonic Waves In Two-Phase Materials, Dalie Liu, Joseph A. Turner
Influence Of Spatial Correlation Function On Attenuation Of Ultrasonic Waves In Two-Phase Materials, Dalie Liu, Joseph A. Turner
Department of Engineering Mechanics: Faculty Publications
Successful processing of materials by powder sintering relies on the creation of strong interparticle bonds. During certain critical stages of the sintering process, the medium may be modeled as two phases consisting of the particles and a surrounding matrix. Ultrasonic methods have been proposed as a potential tool for monitoring such sintering processes. Thus, an understanding of the propagation and scattering of elastic waves in two-phase solids is of fundamental importance to these monitoring techniques. In this article, expressions for the ultrasonic attenuations are developed based on the spatial statistics of the density and Lamé parameters of the material constituents …
Rippling Of Polymer Nanofibers, Xiang-Fa Wu, Yulia Kostogorova-Beller, Alexander Goponenko, Haoqing Hou, Yuris A. Dzenis
Rippling Of Polymer Nanofibers, Xiang-Fa Wu, Yulia Kostogorova-Beller, Alexander Goponenko, Haoqing Hou, Yuris A. Dzenis
Department of Engineering Mechanics: Faculty Publications
This paper studies the evolution mechanism of surface rippling in polymer nanofibers under axial stretching. This rippling phenomenon has been detected in as-electrospun polyacrylonitrile in recent single-fiber tension tests, and in electrospun polyimide nanofibers after imidization. We herein propose a one-dimensional nonlinear elastic model that takes into account the combined effect of surface tension and nonlinear elasticity during the rippling initiation and its evolution in compliant polymer nanofibers. The polymer nanofiber is modeled as an incompressible, isotropically hyperelastic Mooney-Rivlin solid. The fiber geometry prior to rippling is considered as a long circular cylinder. The governing equation of surface rippling is …
Analysis Of The Effects Of The Residual Charge And Gap Size On Electrospun Nanofiber Alignment In A Gap Method, Lihua Liu, Yuris A. Dzenis
Analysis Of The Effects Of The Residual Charge And Gap Size On Electrospun Nanofiber Alignment In A Gap Method, Lihua Liu, Yuris A. Dzenis
Department of Engineering Mechanics: Faculty Publications
In this paper, the effects of residual charges on nanofiber alignment in a gap method are studied and presented. The gap method was presented by Li and Xia (2003 Nano Lett. 3 1167); in it, a gap is introduced into a traditional collector. Due to the non-perfect conductivity of electrospun nanofibers, they carry residual charges after deposition across the gap. These residual charges will interact with the charges carried by the upcoming jet/fiber, that will also deposit across the gap. The effects of these charge interactions on nanofiber alignment were studied numerically at various gap sizes. Results showed that alignments …
On Constitutive Models For Limited Elastic, Molecular Based Materials, Millard F. Beatty
On Constitutive Models For Limited Elastic, Molecular Based Materials, Millard F. Beatty
Department of Engineering Mechanics: Faculty Publications
The response function for a general class of elastic molecular based materials characterized by their limiting molecular chain extensibility and depending on only the first principal invariant of the Cauchy–Green deformation tensor together with a certain molecular based limiting extensibility parameter is introduced. The constitutive response function for the Gent material is then derived inversely as the [0/1] Padé approximant of this class, a result that leads naturally to an infinite geometric series representation of its response function. Truncation of this series function characterizes a familiar class of quadratic materials now having physically relevant material constants. It is shown that …
Simultaneous Birefringence, Small- And Wide-Angle X-Ray Scattering To Detect Precursors And Characterize Morphology Development During Flow-Induced Crystallization Of Polymers, Lucia Fernandez-Ballester, Tim Gough, Florian Meneau, Wim Bras, Fernando Ania, Francisco Jose Balta-Calleja, Julia A. Kornfield
Simultaneous Birefringence, Small- And Wide-Angle X-Ray Scattering To Detect Precursors And Characterize Morphology Development During Flow-Induced Crystallization Of Polymers, Lucia Fernandez-Ballester, Tim Gough, Florian Meneau, Wim Bras, Fernando Ania, Francisco Jose Balta-Calleja, Julia A. Kornfield
Department of Engineering Mechanics: Faculty Publications
An experimental configuration that combines the powerful capabilities of a short-term shearing apparatus with simultaneous optical and X-ray scattering techniques is demonstrated, connecting the earliest events that occur during shear-induced crystallization of a polymer melt with the subsequent kinetics and morphology development. Oriented precursors are at the heart of the great effects that flow can produce on polymer crystallization (strongly enhanced kinetics and formation of highly oriented crystallites), and their creation is highly dependent on material properties and the level of stress applied. The sensitivity of rheo-optics enables the detection of these dilute shear-induced precursors as they form during flow, …
Computer Simulation Of Radio Frequency Heating Of Model Fruit Immersed In Water, Sohan Birla, Shaojin Wang, Juming Tang
Computer Simulation Of Radio Frequency Heating Of Model Fruit Immersed In Water, Sohan Birla, Shaojin Wang, Juming Tang
Department of Engineering Mechanics: Faculty Publications
The present study investigated the effect of different factors on temperature distribution within a spherical object in a parallel plate radio frequency (RF) heating system. A finite element-computer simulation program - FEMLAB was used to solve the electromagnetic and Navier-Stoke equations for developing a model to study the effect of dielectric properties of a model fruit and its surrounding medium. The model fruit was prepared from 1% gellan gel for experimental validation of the simulation results. The results showed that spherically-shaped samples surrounded with air between RF electrodes and placed in the proximity of electrodes would not heat uniformly. Immersing …
Wigner Distribution Of A Transducer Beam Pattern Within A Multiple Scattering Formalism For Heterogeneous Solids, Goutam Ghoshal, Joseph A. Turner, Richard Weaver
Wigner Distribution Of A Transducer Beam Pattern Within A Multiple Scattering Formalism For Heterogeneous Solids, Goutam Ghoshal, Joseph A. Turner, Richard Weaver
Department of Engineering Mechanics: Faculty Publications
Diffuse ultrasonic backscatter measurements have been especially useful for extracting microstructural information and for detecting flaws in materials. Accurate interpretation of experimental data requires robust scattering models. Quantitative ultrasonic scattering models include components of transducer beam patterns as well as microstructural scattering information. Here, the Wigner distribution is used in conjunction with the stochastic wave equation to model this scattering problem. The Wigner distribution represents a distribution in space and time of spectral energy density as a function of wave vector and frequency. The scattered response is derived within the context of the Wigner distribution of the beam pattern of …