Ratcheting Effect of 304 Stainless Steel Manufactured by Laser Metal Deposition Under Uniaxial Cyclic Stress

Abstract

Laser metal deposition (LMD) is an advanced manufacturing technology which has become increasingly popular in recent years. The cyclic tests of 304 austenitic stainless steel (SS304) manufactured by LMD are conducted under symmetrical and asymmetrical cyclic stress. In the results, it is shown that SS304 manufactured by LMD exhibits cyclic softening/hardening and ratcheting effect under symmetrical cyclic stress. The ratcheting strain and ratcheting strain rate of the smooth specimen both increase as the cyclic stress amplitude under the asymmetric cyclic stress. The ratcheting strain and ratcheting strain rate of the smooth specimen change non‐monotonously as the mean stress increases. As the stress amplitude increases, the area of fatigue fracture becomes smaller until no fatigue crack initiation zone can be observed. In this case, only the characteristic of plastic fracture is significant. Park et al.'s model has the worst predicted accuracy. Modified Goodman equation and Smith–Watson–Topper model have the similar predicted accuracy.