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Finite Element Model
A finite element model (FEM) was done in IDEAS to test the natural frequency of the structure. The resulting first frequency from the FEM was 71.1 Hz, which is comfortably higher than the required lower limit of 35 Hz. The finite element model included the eight faces, three interior shelves, one end shelf, and the baseplate. A discussion of the FEM can be found in the list of FEM links below.
Validity checks were done to ensure that the model did in fact closely approximate MidSTAR. These checks validate that 71.1 Hz is a good approximation of the actual natural frequency. These checks included free edge checks. Free edge checks find misalignments in the elements and helps the user to align the elements, which increases the quality of the FEM. A coincident node check was done to find duplicate nodes and eliminate extras, which also increases the quality. Mass properties of the FEM were compared to the mass properties of a similar assembly in IDEAS. The mass properties of the mesh matched that of the structure.
The FEM Boundary Conditions were set so that the mesh was clamped at the end of the structure, where it interfaces with the lightband. Other surfaces were rigidly attached to each other to simulate the bolts that will actually be used.
A power point slideshow of the first ten bending mode results (pictures and frequencies) from IDEAS is also included below.
FEM Results
Mode: 1 Frequency: 71.1 Hz
Finite Element Model Links
FEM Coupled Load Analysis Submission
Acknowledgements: Special thank you to Alexia Lyons and Craig Stevens of Goddard Space Flight Center for invaluable assistance and guidance with analysis for MidSTAR.