Free-suspension residual flexibility testing of Space Station Pathfinder - Comparison to fixed-base results

摘要

Application of the free-suspension residual flexibility modal test method to the International Space Station's Pathfinder structure is described. ^The Pathfinder, a large structure of the general size and weight of Space Station module elements, was also tested in a large fixed-base fixture to simulate Shuttle Orbiter payload constraints. ^After correlation of the Pathfinder FEM model to residual flexibility test data, the model was coupled to a fixture model, and constrained modes and frequencies were compared to fixed-base test modes. ^The residual flexibility model compared very favorably to results of the fixed-base test. ^This is the first known direct comparison of free-suspension residual flexibility and fixed-base test results for a large structure. ^The model correlation approach used by the author for residual flexibility data is presented. ^Frequency response functions (FRF) for the regions of the structure that interface with the environment (a test fixture or another structure) are shown to be the primary tools for model correlation that distinguish or characterize the residual flexibility approach. ^It is shown that good comparison of analytical-to-experimental FRF is the key to obtaining good agreement of the residual flexibility values. ^(Author)