Fatigue and stress analysis of a novel test coupon geometry developed for hydraulic pressure impulse testing

Pressure impulse fatigue testing of a novel test coupon geometry was conduc ted to simulate hydraulic flight control manifolds under multiaxial stress conditions. The configuration of the coupon was particularly useful for eva luating complex multiaxial stress states and for comparing the impulse fati gue performance of different types of alloys under conditions of high stres s concentration. In this article, three-dimensional linear elastic finite e lement analyses are presented to quantify the von Mises equivalent and maxi mum principal stress distributions at the stress-critical regions. Fatigue life results using the present coupon geometry are provided for two high-st rength aluminum alloy variants, including Types 7075 and 6013. Post-test ma croscopic and scanning electron microscopy examinations are presented to ch aracterize the fatigue fractures and to show that fatigue crack initiation takes place at the maximum stress locations as predicted by finite element analysis.