The effect of the environmental conditions on the threshold against fatigue crack propagation

The threshold against fatigue crack propagation (Delta Kth) is a crucial parameter for the damage tolerance assessment of engineering components subjected to cyclic loading and it is composed by two distinct components, one intrinsic, dependent on the elastic material properties and the lattice type, and one extrinsic, related to the occurrence of crack closure effects. An important issue is that several factors can influence Delta Kth and, in general, the fatigue crack propagation behavior. In this work, the influence of the experimental procedure, air humidity, stress ratio and test frequency on da/dN-Delta K data has been investigated. Results are discussed with their potential causes and consequences on the calculations of the residual lifetime. (C) 2021 The Authors. Published by Elsevier B.V.