Similitude of residual stresses and the warm pre stress effect

A material's apparent fracture toughness, at a specific temperature and loading rate, is affected by two factors: residual stresses and the so called Warm Pre Stress (WPS) effect. Residual stresses are global stresses, independent of a pre-existing flaw. They are generally due either to welding or thermal loads, but can also be introduced by plastic deformation. The WPS is due to a local plastic deformation of the material in front of a crack. The residual stresses can be either detrimental or beneficial, whereas WPS is always beneficial. Despite their different nature and origin, they do show a similitude on the apparent fracture toughness response. This similitude is highlighted here.