Date

2020-10

Author

Türker, Caner

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Random vibration tests are performed by attaching a product on an electro dynamic shaker as a part of standardized environmental vibration tests which require specified random vibration profiles applied to products within certain tolerance bands. An ideal test fixture, which will be used to attach a product to a shaker, should be as rigid as possible with no local resonances in the frequency range of the random vibration test profile. However, such a fixture design is rarely possible due to concerns such as fabrication costs, testing time, etc. A rigid fixture usually leads to a design comprised of massive components which may not be economical to fabricate or may not be feasible because of the available payload carrying capacity of the shaker planned to be used for the test. In cases where multiple test items are sought to be tested simultaneously to reduce overall testing time, increased total payload necessitates the fixture designers to reduce the fixture weight. All these practical issues oftentimes force test engineers to design relatively low-weight test fixtures with local resonant behavior in the frequency range of interest. The existence of these local resonances of the fixture would cause resonant vibration behavior which sometimes may prevent the shaker control system from producing the desired random vibration profile. In this study, a random vibration testing scenario is investigated to identify the described issues with producing a desired random vibration profile. The problem is studied both experimentally and through finite element simulations. A remedy, which involves increasing damping in the problematic local modes of the test fixture by adding tuned vibration absorbers, is proposed and shown to be effective through finite element based simulations and experiments.

Subject Keywords

Random Vibrations, Vibration Test Fixture, Resonance Vibration Problems, Vibration Control, Tuned Vibration Absorbers

URI

https://hdl.handle.net/11511/69229

Collections

Graduate School of Natural and Applied Sciences, Thesis