The fatigue damage squeezing method: A signal compression strategy for accelerated life testing

Fatigue testing using full-length, in-service signals has historically been both time- and cost-prohibitive because the field environments of the test article typically reflect its multiyear service life. Current methods for accelerating fatigue tests do exist, but they often rely on heuristics, do not apply to multiaxial or dynamic loading situations, and/or use truncation methods that remove important load interaction effects, which may ultimately lead to uncharacteristic failure modes during testing. This paper presents the fatigue damage squeezing (FDS) method, a novel approach for systematically compressing fatigue test signals using the continuous wavelet transform. The FDS method uses an integrated fatigue model and predictions from finite element analysis to produce compressed signals that not only exhibit spectral and temporal characteristics that are similar to the original signals but also produce representative failure modes in a fraction of the test time. The method was validated using uniaxial and biaxial experimental tests with proportional loading conditions.