Optimization of Fatigue Test Signal Compression Using The Wavelet Transform

ATA Engineering has developed a wavelet-based damage squeezing methodology for generating optimally compressed fatigue test signals that produce an equivalent amount of fatigue damage in a predictably reduced amount of time compared to the baseline (uncompressed) signals. Fatigue-critical signal characteristics (e.g., magnitude, phase, frequency, and sequencing relationships) are identified in the time-scale domain and preserved during signal compression such that the resulting signals produce characteristic responses and failure modes during test. The damage squeezing algorithm uses a constrained optimization formulation governed by physical constraints to minimize error in localized damage equivalence, thereby removing the heuristics associated with traditional signal editing approaches. The damage squeezing methodology is extensible to the compression of rotorcraft-characteristic signals, including proportional, non-proportional, variable amplitude, and/or mixed-environment (e.g., sine-on-random) loading and can be used to accelerate system-level fatigue test programs requiring multiple input (excitation) sources by accounting for dynamic amplification between each of the input and output (response) locations. The Research Institution for the proposed STTR effort, Arizona State University, will utilize state-of-the-art test facilities at the Adaptive Intelligent Materials and Systems Center to conduct experimental validation of the damage squeezing methodology.