Theses and Dissertations at Montana State University (MSU)
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Item On the transport mechanism of rockfalls and avalanches(Montana State University - Bozeman, College of Engineering, 1989) Lacy, Jeffrey MichaelIn this thesis, a numerical model of a granular shear flow is developed. This model is two-dimensional and assumes the shearing granules to be identical, smooth, semi-elastic circular disks. The field containing these disks is bounded on the top and bottom by solid blocks of disks with the same properties. The field is bounded on the right and left by periodic boundaries. The top boundary block has an assigned horizontal velocity and overburden mass, and is unconstrained in the vertical direction. The base boundary block is immobile and does not permit scour. The numerical model is then used to test the hypothesis that, for large overburden pressures, collisions in the shearing region occur involving more than two particles, and that these multi-particle collisions act to reduce the shear strength of the dilatant granular flow. Flows were modeled for a variety of shear speeds and overburden pressures. Results of these simulations show that, although multi-particle collisions do occur with increasing frequency as overburden is increased, they do not have any significant effect on the shear strength of the granular flow. Therefore, this hypothesis is rendered invalid.Item Aircraft wing skin contouring as a result of residual stress distributions induced by shot peening(Montana State University - Bozeman, College of Engineering, 1989) Homer, Scot EdwardShot peening is a viable method for the forming of aircraft wing skins to aerodynamic contours. Presently, geometric methods used to calculate peening intensity patterns are approximate. These methods are based on simplifying assumptions which are not valid for complex contours. The scope of the work presented in this thesis is to develop a more accurate method of predicting peening intensity patterns. The finite element is used to model the effects of shot peening. Inversion of the equations to determine an exact solution for the peening intensity pattern is impossible. An approximate solution is found through numerical methods taking into account contour accuracy and peening intensity magnitudes. The resulting procedure produces accurate and reasonable results for the test cases presented, (computer simulations). Verification of the procedure will be completed when the system is field tested on an actual wing skin.