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Full-Text Articles in Mechanical Engineering
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 …
Electroelastic Effect Of Thickness Mode Langasite Resonators, Haifeng Zhang, Joseph A. Turner, J. S. Yang, J. A. Kosinski
Electroelastic Effect Of Thickness Mode Langasite Resonators, Haifeng Zhang, Joseph A. Turner, J. S. Yang, J. A. Kosinski
Department of Engineering Mechanics: Faculty Publications
Langasite is a very promising material for resonators due to its good temperature behavior and high piezoelectric coupling, low acoustic loss, and high Q factor. The biasing effect for langasite resonators is crucial for resonator design. In this article, the resonant frequency shift of a thickness-mode langasite resonator is analyzed with respect to a direct current (DC) electric field applied in the thickness direction. The vibration modes of a thin langasite plate fully coated with an electrode are analyzed. The analysis is based on the theory for small fields superposed on a bias in electroelastic bodies and the first-order perturbation …
Adhesive Contact In Filaments, Xiang-Fa Wu, Yuris A. Dzenis
Adhesive Contact In Filaments, Xiang-Fa Wu, Yuris A. Dzenis
Department of Engineering Mechanics: Faculty Publications
This paper studies the elastic contact in filaments induced by surface adhesion, which plays an important role in the mechanical response of fibrous materials (e.g., fiber friction, sliding, compression hysteresis, etc.). During the process, a simple 3D elastic contact model was proposed. The filaments were assumed to be uniform, smooth elastic cylinders, and the adhesive force between filaments in contact was estimated according to Bradley’s approach (Bradley 1932 Phil. Mag. 13 853) that relies on the filament configurations before deformation. Under the action of fiber surface adhesion, the elastic deformation and the size of the contact zone were determined in …
Collapse Analysis Of Nanofibers, Xiang-Fa Wu, Yuris A. Dzenis
Collapse Analysis Of Nanofibers, Xiang-Fa Wu, Yuris A. Dzenis
Department of Engineering Mechanics: Faculty Publications
Continuous nanofibers fabricated by the electrospinning technique have found increasing applications (e.g., nanofiber composites, nanofiber devices, bioengineering tissue scaffolding, etc.). For a nanofiber network subjected to a small external perturbation, the fiber segments within the network may deflect and stick to each other under the condition that their surface adhesion energy overcomes the elastic strain energy induced by fiber bending. Therefore, this paper aims to study adhesion-induced nanofiber collapse and relevant criteria. A simple fiber collapse model was proposed, which is based on the contact of two deflected elastic filaments under surface adhesion. Four fundamental fiber collapse modes (i.e., fiber-flat …
Calibration Of Atomic Force Microscope Cantilevers Using Piezolevers, Saltuk B. Aksu, Joseph A. Turner
Calibration Of Atomic Force Microscope Cantilevers Using Piezolevers, Saltuk B. Aksu, Joseph A. Turner
Department of Engineering Mechanics: Faculty Publications
The atomic force microscope (AFM) can provide qualitative information by numerous imaging modes, but it can also provide quantitative information when calibrated cantilevers are used. In this article a new technique is demonstrated to calibrate AFM cantilevers using a reference piezolever. Experiments are performed on 13 different commercially available cantilevers. The stiff cantilevers, whose stiffness is more than 0.4 N/m, are compared to the stiffness values measured using nanoindentation. The experimental data collected by the piezolever method is in good agreement with the nanoindentation data. Calibration with a piezolever is fast, easy, and nondestructive and a commercially available AFM is …
Computational Constitutive Model For Predicting Nonlinear Viscoelastic Damage And Fracture Failure Of Asphalt Concrete Mixtures, Yong-Rak Kim, D. H. Allen, D. N. Little
Computational Constitutive Model For Predicting Nonlinear Viscoelastic Damage And Fracture Failure Of Asphalt Concrete Mixtures, Yong-Rak Kim, D. H. Allen, D. N. Little
Department of Engineering Mechanics: Faculty Publications
A computational constitutive model was developed to predict damage and fracture failure of asphalt concrete mixtures. Complex heterogeneity and inelastic mechanical behavior are addressed by the model by using finite-element methods and elastic– viscoelastic constitutive relations. Damage evolution due to progressive cracking is represented by randomly oriented interface fracture, which is governed by a newly developed nonlinear viscoelastic cohesive zone model. Computational simulations demonstrate that damage evolution and failure of asphalt concrete mixtures is dependent on the mechanical properties of the mixture. This approach is suitable for the relative evaluation of asphalt concrete mixtures by simply employing material properties and …
Wrinkling Of A Charged Elastic Film On A Viscous Layer, Xiang-Fa Wu, Yuris A. Dzenis, Kyle W. Strabala
Wrinkling Of A Charged Elastic Film On A Viscous Layer, Xiang-Fa Wu, Yuris A. Dzenis, Kyle W. Strabala
Department of Engineering Mechanics: Faculty Publications
A thin metallic film deposited on a compliant polymeric substrate begins to wrinkle under compression induced in curing process and afterwards cooling of the system. The wrinkle mode depends upon the thin film elasticity, thickness, compressive strain, as well as mechanical properties of the compliant substrate. This paper presents a simple model to study the modulation of the wrinkle mode of thin metallic films bonded on viscous layers in external electric field. During the procedure, linear perturbation analysis was performed for determining the characteristic relation that governs the evolution of the plane-strain wrinkle of the thin films under varying conditions, …
A New Mass Sensor Based On Thickness-Twist Edge Modes In A Piezoelectric Plate, J.S. Yang, A. K. Soh
A New Mass Sensor Based On Thickness-Twist Edge Modes In A Piezoelectric Plate, J.S. Yang, A. K. Soh
Department of Engineering Mechanics: Faculty Publications
We propose a new mass sensor based on thickness-twist edge modes in a piezoelectric plate of 6mm crystals. By performing a theoretical analysis, a simple expression of sensitivity is obtained. The proposed sensor has an important advantage in the sense that it can be mounted away from the edge of the plate where the motion is insignificant and, thus, the operation of the device is unaffected.
Effect Of Interface Modification On The Mechanical Behavior Of Carbon Nanotube Reinforced Composites Using Parallelmolecular Dynamics Simulations, S. Namilae, U. Chandra, A. Srinivasan, Namas Chandra
Effect Of Interface Modification On The Mechanical Behavior Of Carbon Nanotube Reinforced Composites Using Parallelmolecular Dynamics Simulations, S. Namilae, U. Chandra, A. Srinivasan, Namas Chandra
Department of Engineering Mechanics: Faculty Publications
Molecular dynamics (MD) simulations play an important predictive role in understanding the behavior of nanoscale systems. In this paper, parallel MD simulations are used to understand the mechanical behavior of interfaces in CNT based composites. We present an algorithm for parallel implementation of MD simulations of carbon nanotube (CNT) based systems using reactive bond order potentials. We then use that algorithm to model the CNT-polymer interfaces with various levels of interaction as (a) described only by long range Van Der Waals interactions (b) chemically bonded with fixed matrix and (c) chemically bonded with matrix explicitly modeled. It is shown that …
Influence Of Van Der Waals Forces On Increasing The Strength And Toughness In Dynamic Fracture Of Nanofibre Networks: A Peridynamic Approach, Florin Bobaru Ph.D.
Influence Of Van Der Waals Forces On Increasing The Strength And Toughness In Dynamic Fracture Of Nanofibre Networks: A Peridynamic Approach, Florin Bobaru Ph.D.
Department of Engineering Mechanics: Faculty Publications
The peridynamic method is used here to analyse the effect of van der Waals forces on the mechanical behaviour and strength and toughness properties of three-dimensional nanofibre networks under imposed stretch deformation. The peridynamic formulation allows for a natural inclusion of long-range forces (such as van der Waals forces) by considering all interactions as ‘long-range’. We use van der Waals interactions only between different fibres and do not need to model individual atoms. Fracture is introduced at the microstructural (peridynamic bond) level for the microelastic type bonds, while van der Waals bonds can reform at any time. We conduct statistical …