Abstract

Aerospace structures such as rockets can experience various shock events during flight, such as stage separation or impacts. These shock events can expose components inside the rocket to large accelerations and stresses which in turn can damage the parts. Shocks are often simulated in the lab using a resonant shock plate test. Resonant shock plate testing is often used to qualify aerospace parts, as it can mimic the shocks experienced during launch and stage separations. However, during the course of development, both the definition of the shock environment and the design of the subcomponent tend to change, so that multiple shock tests are required. The design and qualification process could therefore be sped up considerably if some of these tests could be replaced with simulations. Substructuring provides a possible solution. This thesis first explores modeling of a 1kHz resonant shock plate. Modal transient simulations are used to investigate how many modes are needed to accurately reproduce the response of the plate and part, and the shock response spectrum (SRS) experienced. Then a component, modeled as a single degree-of-freedom system is attached to the center of the plate. The component's mass and fixed-base natural frequency are varied to understand how its SRS is affected. Finally, we investigate the use of modal substructuring to predict the response of devices under test (DUT) during resonant shock plate tests. Substructuring is simulated using a finite element model (FEM) to generate the modes that would be measured in a test. The resonant shock plate, mounting frame, and the DUT are all modeled separately, and their modes computed in Abaqus. Then, these modal properties are provided to a modal substructuring routine to predict system-level modes and responses. These responses are compared to a structure truth model simulated entirely in FEA. The accuracy of substructuring is compared with the FEM truth models for two representative assemblies. The effects of noise on FEM substructuring results is explored. Then, a physical assembly is also created and modes determined experimentally. FEM derived and experimentally measured modes are compared. This data is then used to explore mass normalization. Substructuring using experimental data is addressed as the next step.

Degree

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

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