Dynamic finite element analysis of micropolar elastic materials Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/sf268911g

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  • In granular or fibrous materials, in which the dimensions of the internal structure can be of the same order of magnitude as major flaws or holes, classical elasticity theory does not consistently provide accurate models of the large stress gradients that may develop. With the incorporation of additional rotational degrees of freedom, the development of micropolar elasticity theory offers promise for the modeling of these phenomena. The principal objective of this investigation was to develop a plane-strain, dynamic, finite element method for the dynamic response of micropolar elastic media. For purposes of analysis, an eight-node isoparametric, quadrilateral element was used, and the dynamic finite element model was verified by comparing its output, including both displacement and microrotational solutions, with analytic solutions for micropolar plate material subject to shear loads. In addition, plates with circular holes under dynamic loads were analyzed. The results obtained for a special case of a classically elastic material were in good agreement with previously obtained analytical solutions. Materials with significant micropolar behavior were found to cause significant reductions in the dynamic stress concentrations caused by the diffraction of plane dilatational waves adjacent to circular holes. Similar trends were observed from the analysis of plates with elliptical holes subject to suddenly applied loads. Finally, two cases were considered: 1) A stationary crack subject to dynamic loads, and 2) a crack propagating at a constant velocity while under constant load. The method for the calculation of dynamic energy release rates, and node releasing techniques for the simulation of crack propagation, were developed for micropolar elastic materials. In both cases, materials with strong micropolar properties were found to have significantly lower dynamic energy release rates than classically elastic material counterparts.
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2009-12-14T21:53:44Z (GMT) No. of bitstreams: 1 KimJongBum1992.pdf: 1139799 bytes, checksum: 68b85d4db78af8fa1409247a404ef3ec (MD5)

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