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Full-Text Articles in Applied Mechanics

Development Of Material Model Subroutines For Linear And Nonlinear Response Of Elastomers, Asim Gillani Oct 2018

Development Of Material Model Subroutines For Linear And Nonlinear Response Of Elastomers, Asim Gillani

Electronic Thesis and Dissertation Repository

The nature of elastomers has been extensively studied ever since the vulcanization of rubber in the 19th century. Elastomers have been heavily employed in various fields, such as automobile, aerospace, robotics, biomimetics, dynamics and energy harvesting. Due to their molecular nature, these materials display hyperelastic and viscous response when deformed. Their response has been studied in a number of works, which tend to explain their nature through the theory of polymer dynamics or using rheological models. As elastomers are designed as actuators, generators or artificial tissues with complex geometries, the need for finite element analysis to study their response is ...


Effect Of Material Viscoelasticity On Frequency Tuning Of Dielectric Elastomer Membrane Resonators, Liyang Tian Jun 2018

Effect Of Material Viscoelasticity On Frequency Tuning Of Dielectric Elastomer Membrane Resonators, Liyang Tian

Electronic Thesis and Dissertation Repository

Dielectric elastomers (DEs) capable of large voltage-induced deformation show promise for applications such as resonators and oscillators. However, the dynamic performance of such vibrational devices is not only strongly affected by the nonlinear electromechanical coupling and material hyperelasticity, but also significantly by the material viscoelasticity. The material viscoelasticity of DEs originates from the highly mobile polymer chains that constitute the polymer networks of the DE. Moreover, due to the multiple viscous polymer subnetworks, DEs possess multiple relaxation processes. Therefore, in order to predict the dynamic performance of DE-based devices, a theoretical model that accounts for the multiple relaxation processes is ...


Full-Scale And Wind Tunnel Investigation Of The Flow Field Over A Coastal Escarpment, Julien Lotufo May 2017

Full-Scale And Wind Tunnel Investigation Of The Flow Field Over A Coastal Escarpment, Julien Lotufo

Electronic Thesis and Dissertation Repository

A multiscale experimental approach, consisting of full-scale measurements and physical modeling in a laboratory environment, was conducted to investigate the flow field over a coastal escarpment on the Wind Energy Institute of Canada’s research and development wind park. The influence of sea breeze inflow conditions, thermal stability and local topographic features on the flow field were examined.

The results of the full-scale study show that the near surface flow field is significantly influenced by the sea breeze circulatory coastal flow regime, creating larger shear layers with a smaller recirculation regions compared to cases of typical boundary layer flow typical ...


Convection In Corrugated Slots, Seyed Arman Abtahi Feb 2017

Convection In Corrugated Slots, Seyed Arman Abtahi

Electronic Thesis and Dissertation Repository

This thesis consists of two parts. The first part deals with the development of proper methodology, i.e. a spectrally accurate algorithm suitable for analysis of convection problems in corrugated slots. The second part is devoted to the study of natural convection in corrugated slots.

The algorithm uses the immersed boundary conditions (IBC) concept to deal with the irregular form of the solution domain associated with the presence of corrugated plates. The field equations are discretized on a regular domain surrounding the flow domain using Fourier expansions in the horizontal direction and Chebyshev expansions in the vertical direction. The boundary ...


Numerical Studies For Improving Fracture Toughness Resistance Curve Testing Using Single-Edge (Notched) Tension Specimens, Yifan Huang Sep 2016

Numerical Studies For Improving Fracture Toughness Resistance Curve Testing Using Single-Edge (Notched) Tension Specimens, Yifan Huang

Electronic Thesis and Dissertation Repository

The fracture toughness resistance curve, i.e. the J-integral resistance curve (J-R curve) or the crack tip opening displacement resistance (CTOD-R) curves, is widely used in the integrity assessment and strain-based design of energy pipelines with respect to planar defects (i.e. cracks). This thesis deals with issues related to the experimental determination of the J(CTOD)-R curves using the newly-developed single-edge (notched) tension (SE(T)) specimens. In the first study, the plastic geometry factor, i.e. the ηpl factor, used to evaluate J in a J-R curve test based on the SE(T ...


Simulation Of Magnetic Field Induced Current And Neuron Spiking For Magnetic Seizure Therapy, Abhijeet R. Wadkar Nov 2015

Simulation Of Magnetic Field Induced Current And Neuron Spiking For Magnetic Seizure Therapy, Abhijeet R. Wadkar

Electronic Thesis and Dissertation Repository

Magnetic seizure therapy (MST) is currently on trial to treat severe cases of depression. This thesis is concerned with getting a deeper understanding of the mechanics behind MST by employing FEA of brain. The simulations performed via COMSOL helped identify the dimensions and coil types of the MST device as well as the angular probing orientations. Largest induced current due to the externally imposed magnetic field was found in the cerebrospinal fluid which was found to act as a barrier to induce current in the gray matter. In an attempt to relate the induced current to the neuron spiking, a ...


Electromechanical Coupling Behavior Of Dielectric Elastomer Transducers, Jianyou Zhou Sep 2015

Electromechanical Coupling Behavior Of Dielectric Elastomer Transducers, Jianyou Zhou

Electronic Thesis and Dissertation Repository

Dielectric elastomer transducers with large deformation, high energy output, light weight and low cost have been drawing great interest from both the research and industry communities, and shown potential for versatile applications in biomimetics, dynamics, robotics and energy harvesting. However, in addition to multiple failure modes such as electrical breakdown, electromechanical instability, loss-of-tension and fatigue, the performance of dielectric elastomer transducers are also strongly influenced by the hyperelastic and viscoelastic properties of the material. Also, the interplay among these material properties and the failure modes is rather difficult to predict. Therefore, in order to provide guidelines for the optimal design ...


Structural Response Analyses Of Piezoelectric Composites Using Nurbs, Vijairaj Raj Sep 2014

Structural Response Analyses Of Piezoelectric Composites Using Nurbs, Vijairaj Raj

Electronic Thesis and Dissertation Repository

Variational method deduced on the basis of the minimum potential energy is an efficient method to find solutions for complex engineering problems. In structural mechanics, the potential energy comprises strain energy, kinetic energy and the work done by external actions. To obtain these, the displacement are required as a priori. This research is concerned with the development of a numerical method based on variational principles to analyze piezoelectric composite plates and solids. A Non-Uniform Rational B-Spline (NURBS) function is used for describing both the geometry and electromechanical displacement fields. Two dimensional plate models are formulated according to the first order ...


Influence Of Approach Flow Conditions On Urban Street Canyon Flow, Karin Blackman Jul 2014

Influence Of Approach Flow Conditions On Urban Street Canyon Flow, Karin Blackman

Electronic Thesis and Dissertation Repository

The turbulent flow within a street canyon and the approaching boundary layer has been studied using idealized wind tunnel models and a semi-idealized field experiment conducted in Nantes, France. The effect of upstream roughness on street canyon flow (lateral length/height, L/h = 30) using either 3D (cube) or 2D (rectangular block) upstream roughness, of the same height as the canyon, has been studied for two streamwise canyon width to height aspect ratios (AR) of 1 and 3 using Particle Image Velocimetry. A further wind tunnel model of equivalent geometry to the field experiment was used to compare with flow ...


Mechanistic Failure Criterion For Unidirectional And Random Fibre Polymer Composites, Jamaloddin Jamali Jun 2014

Mechanistic Failure Criterion For Unidirectional And Random Fibre Polymer Composites, Jamaloddin Jamali

Electronic Thesis and Dissertation Repository

Polymer composite design in energy absorbing components requires a failure criterion that can predict the energy involved in its fracture under different modes of loading. Present mixed mode criteria are mainly empirical or semi-empirical, and are only suitable for a small range of composite types.

The purpose of this study was to develop a mechanistic failure criterion that is applicable to a wide range of polymer composites. An energy based mechanistic failure criterion is proposed to characterize the toughness of unidirectional (UD) and randomly oriented short fibre composites (random fibre composites).

In UD and random composites, the criterion predicts the ...


Finite Element Analyses Of Single-Edge Bend Specimens For J-R Curve Development, Yifan Huang Sep 2013

Finite Element Analyses Of Single-Edge Bend Specimens For J-R Curve Development, Yifan Huang

Electronic Thesis and Dissertation Repository

The fracture toughness resistance curve such as the J-integral resistance curve (J-R curve) is widely used in the integrity assessment and strain-based design of energy pipelines with respect to planar defects (i.e. cracks). Two studies about the development of the J-R curve are carried out and reported in this thesis. In the first study, the plastic geometry factor, i.e. the ηpl factor, used to evaluate J in a J-R curve test based on the single-edge bend (SE(B)) specimen is developed based on the three-dimensional (3D) finite element analysis (FEA). The main finding ...


Numerical Modeling Of Solidification Process And Prediction Of Mechanical Properties In Magnesium Alloys, Mehdi Farrokhnejad Aug 2013

Numerical Modeling Of Solidification Process And Prediction Of Mechanical Properties In Magnesium Alloys, Mehdi Farrokhnejad

Electronic Thesis and Dissertation Repository

A formulation used to simulate the solidification process of magnesium alloys is developed based upon the volume averaged finite volume method on unstructured collocated grids. To derive equations, a non-zero volume fraction gradient has been considered and resulting additional terms are well reasoned. For discretization the most modern approximations for gradient and hessians are used and novelties outlined. Structure-properties correlations are incorporated into the in-house code and the proposed formulation is tested for a wedge-shaped magnesium alloy casting. While the results of this study show a good agreement with the experimental data, it was concluded that a better understanding of ...


Numerical Simulation Of An Open Channel Ultraviolet Waste-Water Disinfection Reactor, Rajib Kumar Saha Aug 2013

Numerical Simulation Of An Open Channel Ultraviolet Waste-Water Disinfection Reactor, Rajib Kumar Saha

Electronic Thesis and Dissertation Repository

The disinfection characteristics of an open channel ultra-violet (UV) wastewater disinfection reactor are investigated using a computational fluid dynamics (CFD) model. The model is based on the volume of fluid method to capture the water-air interface, the Lagrangian particle tracking method to determine the microbial particle trajectory and the discrete ordinate model to calculate the UV intensity field. The numerical predictions are compared with the available experimental data to validate the CFD model. A parametric study is performed to understand the effects of different parameters on the disinfection performance of the reactor. The hydraulic behaviour and the additive nature of ...


Continuum Modeling On Size-Dependent Properties Of Piezoelectric Nanostructures, Zhi Yan Jun 2013

Continuum Modeling On Size-Dependent Properties Of Piezoelectric Nanostructures, Zhi Yan

Electronic Thesis and Dissertation Repository

Piezoelectric beam- and plate-based nanostructures hold a promise for device applications in the nanoelectromechanical systems (NEMS) due to their superior mechanical and electromechanical coupling properties. “Small is different”, nanostructured piezoelectric materials exhibit size-dependent properties, which are different from their bulk counterparts. For predicting the unique physical and mechanical properties of these novel nanostructures, continuum mechanics modeling has been regarded as an efficient tool. However, the conventional continuum models fail to capture the size effects of nanostructures and thus are not directly applicable at the nanoscale. Therefore, it is necessary to develop modified continuum models for piezoelectric nanostructures by incorporating the ...


Vibration And Buckling Of Carbon Nanotube, Graphene, And Nanowire, Mohammad Hadi Mahdavi Jan 2013

Vibration And Buckling Of Carbon Nanotube, Graphene, And Nanowire, Mohammad Hadi Mahdavi

Electronic Thesis and Dissertation Repository

Nanostructured materials with superior physical properties hold promise for the development of novel nanodevices. Full potential applications of such advanced materials require accurate characterization of their physical properties, which in turn necessitates the development of computer-based simulations along with novel experimental techniques. Since controlled experiments are difficult for nanoscale materials and atomic studies are computationally expensive, continuum mechanics-based simulations of nanomaterials and nanostructures have become the focal points of computational nano-science and materials modelling.

In this study, emphasis is given to predicting the mechanical behaviour of carbon nanotube (CNT), graphene, nanowire (NW), and nanowire encapsulated in carbon nanotube (NW@CNT ...


Characterization Of Solar Roadways Via Computational And Experimental Investigations, Rajesh Kanna Selvaraju Oct 2012

Characterization Of Solar Roadways Via Computational And Experimental Investigations, Rajesh Kanna Selvaraju

Electronic Thesis and Dissertation Repository

Efficiency of traditional solar panels is known to be very low and hence necessitates the use of extensive open spaces for producing solar-based electric power. In solar roadways concept, open spaces such as roads, parking lots, bicycle lanes, footpaths are proposed to be utilized. An in-depth quantitative feasibility study for implementing solar roadways in Canada is carried out considering the total available surfaces, solar panel efficiency and effects of fast moving shades. The load carrying capability of commercially available materials for the solar panel top cover is studied in an effort to examine the current as well as near-future implementation ...


Numerical Modelling Of Transport In Complex Porous Media: Metal Foams To The Human Lung, Christopher T. Degroot Jul 2012

Numerical Modelling Of Transport In Complex Porous Media: Metal Foams To The Human Lung, Christopher T. Degroot

Electronic Thesis and Dissertation Repository

Transport in porous media has many practical applications in science and engineering. This work focuses on the development of numerical methods for analyzing porous media flows and uses two major applications, metal foams and the human lung, to demonstrate the capabilities of the methods. Both of these systems involve complex pore geometries and typically involve porous domains of complex shape. Such geometric complexities make the characterization of the relevant effective properties of the porous medium as well as the solution of the governing equations in conjugate fluid-porous domains challenging. In porous domains, there are typically too many individual pores to ...


Mechanical Instability Of Thin Solid Film Structures, Masoud Noroozi May 2012

Mechanical Instability Of Thin Solid Film Structures, Masoud Noroozi

Electronic Thesis and Dissertation Repository

Instability of thin film structures as buckling and wrinkling are important issues in various fields such as skin aging, mechanics of scars, metrology of the material properties of thin layers, coating of the surfaces and etc. Similar to the buckling, highly ordered patterns of wrinkles may be developed on the film‒substrate due to compressive stresses. They may cause a failure of the system as structural damage or inappropriate operation, however once they are well understood, it is possible to control and even use them properly in various systems such as the gossamer structures in the space, stretchable electronics, eyelike ...


Atomic Force Microscopy For Better Probing Surface Properties At Nanoscale: Calibration, Design And Application, Yu Liu Oct 2010

Atomic Force Microscopy For Better Probing Surface Properties At Nanoscale: Calibration, Design And Application, Yu Liu

Electronic Thesis and Dissertation Repository

To measure force by AFM with high resolution requires accurate calibration of optic – lever detection sensitivity and spring constant. On biological AFM force mode, the coupling effects of the liquid environment, spot size of laser beam and laser spot location on AFM cantilever backside, must be considered to correlate the static sensitivities from force curves in air and in liquid for calibration. An effective model has been developed first and experimentally elucidated to calibrate the static sensitivity in liquid. The proposed model eliminates inconvenience of static sensitivity calibration in liquid with possible contamination sources.

The static sensitivity based on force ...