11. A Systematic Evaluation of Test Specification Derivation Methods for Multi-axis Vibration Testing

In the past decade, multi-axis vibration testing has progressed from its early research stages towards becoming a viable technology which can be used to simulate more realistic environmental conditions. The benefits of multi-axis vibration simulation over traditional uniaxial testing methods have been demonstrated by numerous authors. However, many challenges still exist to best utilize this new technology. Specifically, methods to obtain accurate and reliable multi-axis vibration specifications based on data acquired from field tests is of great interest. Traditional single axis derivation approaches may be inadequate for multi-axis vibration as they may not constrain profiles to adhere to proper cross-axis relationships—they may introduce behavior that is neither controllable nor representative of the field environment. A variety of numerical procedures have been developed and studied by previous authors. The intent of this research is to benchmark the performance of these different methods in a well-controlled lab setting to provide guidance for their usage in a general context. Through a combination of experimental and analytical work, the primary questions investigated are as follows: (1) In the absence of part-to-part variability and changes to the boundary condition, which specification derivation method performs the best? (2) Is it possible to optimize the sensor selection from field data to maximize the quality/accuracy of derived multi-axis vibration specifications? (3) Does the presence of response energy in field data which did not originate due to rigid body motion degrade the accuracy of multi-axis vibration specifications obtained via these derivation methods?