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

Abstract

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 multiaxial. 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 multiaxial stress state. The Susmel's fatigue damage parameter is employed to evaluate the fatigue damage of these points on the notch edge. Multiaxial fatigue tests on thin‐walled round tube notched specimens made of GH4169 nickel‐base alloy and 2297 aluminium‐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 multiaxial fatigue loading.

Assessing variable amplitude multiaxial fatigue lifetime of notched components based on the notch critical plane approach

“…Furthermore, fatigue cracks often initiate from notches, that is, from those regions experiencing localized stress/strain concentration phenomena. In this context, not only stress gradients, but also multiaxial stress states exist at the notch root even under uniaxial fatigue loading [6][7][8][9]. The effect of stress gradients, loading non-proportionality, stress multiaxiality, and profiles of the load spectra at the notch root should be taken into account to evaluate the fatigue lifetime of notched components under in-service VA load histories.…”

“…In this paper, the notch critical plane approach (NCP) [9,16] presented by the authors for the constant amplitude (CA) multiaxial fatigue case is initially extended from 2D-to 3D-situations and then applied to predict fatigue lifetime of notched components under complex VA fatigue loading. In this setting, the NCP is the plane experiencing the MVRSS and is taken coincident with that material plane passing through the assumed fatigue critical point (FCP) [7] i.e.…”

Requirements for stress gradient‐based fatigue assessment of notched structures according to theory of critical distance

“…Because of increased computational power, such methods are more easily applicable nowadays. The point (PM) and line (LM) methods—based on the gradient of the stress acting perpendicular to the expected crack path—have gained especial interest, judging by the variety of investigated applications 8–29 …”

Multiaxial notch fatigue life prediction based on the dominated loading control mode under variable amplitude loading

“…Faruq and Susmel 25 formulated a novel multiaxial notch fatigue life estimation technique based on the combined use of the modified Manson–Coffin curve method (MMCCM), the γ‐maximum variance method (MVM) and the elasto‐plastic point method (PM), the proposed multiaxial fatigue assessment methodology is successful in estimating the lifetime of notched metallic materials subjected to both constant amplitude and variable amplitude load histories. Based on local stress responses, Luo et al 26 proposed the stress amplitude method, and the Susmel's parameter method to locate fatigue critical point of metallic notched components under nonproportional loading, 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 multiaxial fatigue loading.…”