11. Pushing 3D Scanning Laser Doppler Vibrometry to Capture Time Varying Dynamic Characteristics

3D scanning laser Doppler vibrometry (LDV) systems are well known for modal testing of articles whose excited dynamic properties are time-invariant over the duration of all scans. However, several potential test situations can arise in which the modal parameters of a given article will change over the course of a typical LDV scan. One such instance is considered in this work, in which the internal state of a thermal battery changes at different rates over its activation lifetime. These changes substantially alter its dynamic properties as a function of time. Due to the extreme external temperatures of the battery, non-contact LDV was the preferred method of response measurement. However, scanning such an object is not optimal due to the non-simultaneous nature of the scanning LDV when capturing a full set of data. Nonetheless, by carefully considering the test configuration, hardware and software setup, as well as data acquisition and processing methods it was possible to utilize a scanning LDV system to collect sufficient information to provide a measure of the time varying dynamic characteristics of the test article. This work will demonstrate the techniques used, the acquired results and discuss the technical issues encountered.