Hysteresis Studies of 7075 Material Test Performed by Schijve and Jacobs
AIR FORCE FLIGHT DYNAMICS LAB WRIGHT-PATTERSON AFB OH
Pagination or Media Count:
The Hysteresis fatigue Analysis HFA method uses a cyclic stress-strain curve in conjunction with a Neuber analyses to describe a notch stress-strain history. The notch stresses are then used in a damage theory which employs an equivalent stress. The HFA does not incorporate a model of cyclic stress relaxation. The purpose of the current effort is to ascertain if, without such a model, the HFA is capable of predicting a series of test results for 7075-T6 aluminum performed by J. Schijve and F. P. Jacobs. This is accomplished by comparing the predictions from the HFA to test results. The HFA predictions are then compared to predictions of the same test lives using the Sequence Accountable Fatigue Program SAF developed by Potter. Potters program employs a decay function which relaxes residual stresses as a function of cycles. To ascertain if the differences in the two fatigue life prediction methods could possibly be attributed to relaxation, a parametric study was made. This paper describes the results of that study.