Machine Design

Determining harmonic response, part II

The Finite-Element Update column in the November 8 issue of MACHINE DESIGN outlined a method for finding stresses and deflections induced by a vibration load. The accompanying flowchart further details the process.

For those readers who would like to try the analysis of the beam, David Dearth, president of Applied Analysis & Technology has provided detailed hand calculations. Readers can request them from [email protected]

In addition, a Word document titled Run Notes & Keystroke Summary and a MSC.Nastran model, also provided, show how to perform the analysis in MSC.Nastran. The model is small enough to process using the limited node or apprentice version of MSC.Nastran V4.6. This software is available from MSC. Software at (714) 444-5188 or from

The simply supported 36-in. beam has a constant cross section and carries the loads listed.

The flowchart shows how to get from an FEA model to accurate deflections and stress caused by input vibrations. A detailed discussion appeared in last month's Finite-Element Update.

The illustration shows peak deflections and stresses for Case A (neglect beam weight) after being processed using Dynamic Response Analyses to Harmonic Excitation software in MSC.Nastran.


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