Effect of Shot-Peening Variables and Residual Stresses on the Fatigue Life of Leaf-Spring Specimens

Abstract

<div class="section abstract"><div class="htmlview paragraph">RESULTS of an investigation into the effect of shot-peening variables and the resulting residual stresses on fatigue life are reported in this paper. Leaf springs were the simple specimens heat-treated, cold worked, and tested in this study.</div><div class="htmlview paragraph">Some of the conclusions reached are: <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1.</span> <div class="htmlview paragraph">There is a minimum shot velocity for each shot size to obtain best fatigue life, and this value is much lower than that normally used.</div></li> <li class="list-item"> <span class="li-label">2.</span> <div class="htmlview paragraph">Exposure time for this type of shot-peened specimen beyond some minimum value is wasteful and costly.</div></li> <li class="list-item"> <span class="li-label">3.</span> <div class="htmlview paragraph">Shot size has little influence on fatigue life for these specimens.</div></li> <li class="list-item"> <span class="li-label">4.</span> <div class="htmlview paragraph">Shot peening specimens while under tensile strain greatly increases fatigue life at 200,000 psi nominal stress over that of nonpeened or strain-free-peened specimens.</div></li> <li class="list-item"> <span class="li-label">5.</span> <div class="htmlview paragraph">Shot peening these specimens gave residual compressive stresses 50% of yield strength, and these stresses can be increased to more than 50% by strain peening.</div></li> <li class="list-item"> <span class="li-label">6.</span> <div class="htmlview paragraph">There is a direct correlation between surface residual compressive stress and fatigue life of these specimens.</div></li></ol></div></div>