Prediction methods of fatigue critical point for notched components under multiaxial fatigue loading

Two methods based on local stress responses are proposed to locate fatigue critical point of metallic notched components under non-proportional loading. The points on the notch edge maintain a state of uniaxial stress even when the far-field fatigue loading is multi-axial. The point bearing the maximum stress amplitude is recognized as fatigue critical point under the condition of non-mean stress, otherwise the Goodman’s empirical formula is adopted to amend mean stress effect prior to the determination of fatigue critical point. Furthermore, the uniaxial stress state can be treated as a special multi-axial stress state. The Susmel’s fatigue damage parameter is employed to evaluate the fatigue damage of these points on the notch edge. Multi-axial fatigue tests on thin-walled round tube notched specimens made of GH4169 nickel-base alloy and 2297 aluminum-lithium alloy are carried out to verify the two methods. The prediction results show that both the stress amplitude method and the Susmel’s parameter method can accurately locate the fatigue critical point of metallic notched components under multi-axial fatigue loading.