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Loading Stress on Lifecycle Test Fixtures
Kevin Stewart
California Polytechnic State University
This project analyzed a lifecycle test fixture for stress under generic test loading. The maximum stress is expected to occur near the shrink fit pin on the lever arm. The model was constructed using 3D solid quadratic elements without reduced integration. Interaction properties and boundary conditions were defined between the pin, lever, and drive shaft. The resolved loads were then applied to the lever arm. The model was partitioned and then meshed using structured meshes. The program could not correctly run using the press-fit definitions. Only one of the press-fits would be active at a time, leading to model modifications. These modifications included removing the pin, adding tie constraints between the drive shaft and lever arm, and adding more boundary conditions at the pin location. Results obtained from this model were within magnitude of the hand calculations. The von Mises stress of the lever arm was approximately 1062 psi, while the hand calculations yielded a value of 1685 psi. The overall vertical deflection of the system was .0027 inches, which is realistic for the scale of the project.
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