Computational Engineering Commons^™

Incipient Deformation Of Small Volumes Of Fcc Metals, Mahdi Bagheripoor

Electronic Thesis and Dissertation Repository

In the area of mechanics of materials, the classic theories cannot describe the material behaviour as the volume of deformation or sample size is small enough to be compared with the size scales of the imperfections of the crystal. So, there has been a great deal of interest in investigating the plasticity of micron and nano-sized materials, in the last 20 years. As a Ph.D. research project, the deformation mechanism at small scales of fcc metals is studied based on dislocations behaviour. The effect of main parameters that haven’t been studied in detail, including, crystal orientation, pre-existing faults, grain boundaries, …

Advances In Design Methodology In Swelling Shale Rock In Southern Ontario, Thomas R.A. Lardner

Electronic Thesis and Dissertation Repository

As infrastructure requirements increase in southern Ontario, excavations within swelling rock formations will become more frequent and larger. The objective of this study is to advance design capability for structures in swelling rock through three aspects: i) developing a practical swelling model for design engineers, ii) investigate two crushable/compressible materials for the mitigation of swelling rock effects, and iii) observe and analyze the behaviour of swelling rock to current excavation techniques.

A swelling rock constitutive model has been developed. The swelling parameters include the horizontal and vertical free swell potential, threshold stress, and critical stress as well as a “pseudo-Poisson’s …

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 …