Electronic modules for a guidance system are mounted in a rack with spring clips resisting motion normal to the printed wiring board (PWB) and an aluminum bar with an elastomer pad keeping the module connected to a backplane. The elastomer pad also resists motion normal to the board. The proper boundary conditions for the spring clips, retention bar, and connector are needed in a finite element model in order to evaluate the shock and vibration transmitted to the module’s electrical components. The finite element model of the module was assembled, and an actual module was tested under random vibration and a 1g sine sweep. The printed wiring board elastic modulus was artificially set higher in the FEM than a measured value to account for the stiffening effect of board components which were omitted from the model. By also choosing the proper boundary conditions to represent the spring clips, retention bars, and backplane connection, the finite element model was able to match the first and second mode frequencies from the hardware test results.

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