Vibration Testing: Operational Deflection Shapes from Sine Analysis

Vibration testing to international and laboratory standards is important for product verification and approval. Additional information of the system under test are often neglected, despite being easily identifiable from the measurements at hand. Operational deflection shapes, for example, can be acquired from sine sweep data. The results provide engineers with additional insight into the vibration characteristics of the specimen. They enable engineers to further identify the source of vibration-induced failures, optimize test fixtures, and compare with real-world deflection shapes using FEA.

Head expander with sensors and measuring grid
Undeformed and deformed operational deflection shape extracted at 1,954 Hz

The trend goes towards more and more measurement channels and sensors attached to the specimen. For ODS analysis, the deflection shapes of the fixed specimen are encountered during the real vibration test. The m+p VibControl vibration controller generates a spectrum for each measurement point, which is phase-referenced to the control channel. The results are loaded into the modal analysis software of the m+p Analyzer. In the software, a geometry is created and each measurement is mapped to a single geometry node. The test engineer may now review and analyze the operational deflection shapes for individual frequencies.

Read more in the article “Gain a Deeper Insight”, Automotive Testing International, March 2018.


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