Fatigue-A Test Integrated Damage Modeling Approach

Abstract

Empirical damage models were developed using the method of least squares and flight simulation test results. The experimental data were obtained from notched coupon specimens subjected to a number of simulated transport flight-by-flight test sequences of alternate loading intensities. Clipping of maximum load levels was performed during test to isolate the influence of load induced microplasticity from the combined influence of micro and macroplasticity on test life. The resulting test data were indicative of load sequence effects resulting from microplasticity at material and fabrication defects contained within a local volume of material adjacent to a notch. Since the specimen was the damage integrator, the resulting models were considered to statistically account for load sequence effects in the development and coalescing of crack nuclei in forming a predominant propagating crack. Results indicate that the models present a viable alternative to the PalmgrenMiner approach.