Efficient transient analysis of mechanical systems with local nonlinearities /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1990.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | A computationally efficient convolution method, based on discretized impulse response and transition matrix integral formulations, is developed for the transient analysis of complex linear structures interacting through strong local nonlinearities. In the formulation, the coupling forces due to the nonlinearities are treated as external forces acting on the coupled subsystems. Iteration is utilized to determine their magnitudes at each time increment. The method is applied to a generic rotor-housing model representing a turbopump of a space shuttle main engine (SSME). As compared to the fourth-order Runge Kutta numerical integration method, the convolution approach proved more efficient and robust for the same accuracy requirement. This is due to the closed form formulation of the convolution approach which allows for the use of relatively larger time increments and for a reduction in the round-off errors. Three kinds of nonlinear coupling are studied in this research. They involve a gap, dry friction and impact. The nonlinearity in the SSME is due to bearing deadband clearances. The study involving dry friction is made on a 5-block mechanical system. The result of the dry friction study shows that the convolution method can also be effective in the analysis of nonlinear phenomena such as the occurrence of non-periodic and chaotic responses. A simplified rotor-housing system is used for the study of intermittent motion due to impacts. The instant changes of velocity based on the momentum principle are included in the convolution analysis. Estimated impact force and impact time-duration are utilized in the method. Two iterative techniques are used with the convolution method. They are the Jacobi and the Gauss-Seidel iterative methods. Results show that using Gauss-Seidel method results in better CPU time efficiency. However, using the Jacobi method is thought to be more convenient and flexible in its application. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Mechanical engineering." |
| Physical Description: | xviii, 210 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |