Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Mono-cable logging system with intermediate tension control : computer simulation(Montana State University - Bozeman, College of Engineering, 1988) Turk, Albert VincentA cooperative research project with the USDA-Forest Service has shown the need for a mono-cable logging system with intermediate tension control as an alternative to road construction in the logging area. Intermediate control sheaves will be required to maintain optimum tension throughout long distances and large elevation changes. Preliminary designs have shown the need to model the system to demonstrate the system's feasability. A series of FORTRAN programs were written to simulate this system, building first upon single span solutions, with the eventual program including the capability of simulating the changes in tension of a system of up to 100 connected spans with as many as 200 loads traversing the system. The individual sheaves along the system path can be modeled as either control or idler sheaves. The solution of the necessary equations required the use of iterative solutions. Comparison was made of the Newton-Raphson method and Brown's method for the solution of a set of two non-linear equations with two unknowns. The model satisfies the simulation needs of the system. It allows the monitoring of tension, differential tension across sheaves, and changes in cable length required within each span. The program showed the feasibility of the system and gives direction for future modifications of the model to more closely simulate the actual situation. The program will provide a solid foundation for current and future work in this area and shows a valid procedure for future modeling.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 Determining the change in snow microstructure during large deformation processes by the method of quantitative stereology(Montana State University - Bozeman, College of Engineering, 1989) Edens, Michael QuastModern constitutive theories for snow are now using microstructural parameters in their formulation. In order to improve the theories, more advanced methods of describing the microstructural behavior are needed. This is particularly important since simplifying assumptions must be made in order that the resulting theory is manageable. To confirm understanding of microstructural behavior it is necessary to obtain experimental data pertinent to the density range, deformation range, and deformation rate being modeled. This data is also needed for the evaluation of empirical parameters. The microstructural variables selected to characterize the behavior of snow must be able to represent dominant mechanisms such as pore collapse, bond fracture, and neck and bond growth due to pressure sintering as well as effects of pore pressure, a mechanism to account for a reduction in grain mobility, coupling of deviatoric and volumetric responses, work hardening, and local inertial effects. In this thesis a set microstructural variables that meet these criteria and corresponding mathematical relations from quantitative stereology are reviewed along with relations and techniques required for numerical evaluation. An experimental investigation is carried out to understand the effect changes in these variables have on the behavior of snow subjected to large deformations. Measurements at several stages of deformation are used to understand microstructure changes, dominant mechanisms, and effects on bulk behavior. Microstructure measurements of six snow samples subjected to confined compression tests are presented for precompressed and compressed states corresponding to final loads of 11.2 KN, 22.4 KN, or 44.8 KN. Order of magnitude changes in microstructural parameters are compared with corresponding magnitude changes in stress level for densities ranging from 0.5 g/cc to 0.64 g/cc. Generally, microstructural variables underwent order of 2 changes compared with 16 for the stress level. This experimental investigation presents changes in microstructural variables that result from large deformations and high deformation rate. These results go a long-way toward filling in a gap in the presently available data. Microstructural variables which, to the present, have not been adequately measured and mathematically described are evaluated.Item A continuum mixture theory applied to stress waves in snow(Montana State University - Bozeman, College of Engineering, 1991) Austiguy, George EdwardIn avalanche control work the types of explosives and delivery methods used are primarily determined by trial and error. Understanding the propagation of stress waves in snow is a step towards eliminating some of this guesswork. A continuum theory of mixtures is applied to model snow as a mixture of an elastic solid and an elastic fluid. Three wave types, two dilational and one rotational wave are shown to exist. Theoretical expressions are developed for the wave attenuation and propagation velocity of each of the wave types. Numerical evaluation shows velocity and attenuation increasing with frequency for all three waves. Wave velocity increases with increasing density while attenuation decreases with increasing density for all three waves. The first dilational wave has a slow wave speed and is highly attenuated. This wave exhibits diffusive behavior at low frequencies and nondispersive behavior at high frequencies. The second dilation wave is the fastest of the three wave types and does not appreciably attenuate. Nondispersive wave behavior characterizes this wave at low and high frequencies. The rotational wave is the least attenuated of all three waves and propagates at velocities greater than that of the first dilational . wave but less than that of the second dilational wave. The rotational wave exhibits nondispersive behavior at low and high frequencies. Wave velocities and attenuation show behavior that is in agreement with existing experimental data.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.