Physical and numerical analysis of fracture in flat plates arising from translating loads

Howell, Jonathan (2018) Physical and numerical analysis of fracture in flat plates arising from translating loads. Masters thesis, Memorial University of Newfoundland.

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Abstract

Previous work with moving loads showed a significant decrease in structural capacity of samples subjected to moving loads that caused plastic damages, however did not investigate loads which incited fracture. The state of the art in material science for ductile metals indicates that fracture can be predicted by a locus of triaxiality, Lode Angle Parameter and effective plastic strain. However, in the case of stationary loads, effective fracture strain has been used to accurately predict fracture. Collision analysis for loads which incite fracture is more frequently being completed using non-linear finite element analysis, commonly using the effective plastic strain to fracture method. However, real collisions are often oblique, and as such, it can be assumed that some horizontal translation is realistic and should be modelled as a moving load. This thesis explores the effects of moving loads which incite fracture in plate samples using experiments and corresponding numerical models. The results of this thesis found a significant loss in ability to resist fracture during the horizontal translation of a load along a plate sample as well as a clear inability to accurately characterize a moving load numerically using the effective plastic strain to fracture method. In particular, this thesis presents: the results of laboratory experiments using the Moving Load Apparatus involving two distinct indenters (cutting and rolling wheel) designed to induce different stress states; a discussion of calibrated numerical models as well as triaxiality and Lode Angle Parameter for the point of fracture of these models.

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