37. Next-Generation Random Vibration Tests

This paper describes a radically new approach to the vibration testing of structures in order to demonstrate their endurance under simulated service conditions. The excitation mechanisms of structures in-service typically fall into one of three configurations; (i) excitation from a parent structure through mechanical connections (e.g. during transportation), (ii) excitation from aerodynamic forces distributed over the outer surface of the structure (e.g. aircraft and rockets in flight), or (iii) A combination of (i) and (ii). In nearly all cases, the in-service excitation is multi-directional, yet it is standard practice to replicate these environments with three orthogonal single-axis vibration tests. In addition, a considerable mismatch of the boundary conditions between the in-service and laboratory configurations is common, especially when replicating aerodynamic environments. This paper presents quantitative evidence of limitations with the status quo and demonstrates a superior method; Impedance Matched Multi-Axis Testing (IMMAT). Three noteworthy improvements of the new method are; (i) enhanced replication of the in-service environment, (ii) much shorter test durations, and (iii) a significant reduction in costs associated with random vibration tests.