Investigation of constraint and warm prestressing effects by means of a local approach to fracture

Brittle cleavage fracture, constraint effects as well as warm prestressing (WPS) effects play important roles in structural integrity analysis. A local approach to fracture, i.e. the σ∗ − A∗ model is used to study the constraint and WPS effects on material toughness. The crack depth and loading determine the in-plane constraint while the thickness at the crack tip has an important impact on the out-of-plane constraint. Residual stress contributes to the WPS effect, whereas the increase of fracture toughness is not completely attributed to the residual stress. The magnitudes of preloading and unloading and the reloading temperature determine the increased fracture toughness.