Effect of residual stresses on the crack-tip constraint in a modified boundary layer model

Abstract

a b s t r a c tResidual stresses play a crucial role in structural integrity assessment. In this study, a large cracked cylinder with a weld in the center is applied to investigate the effect of residual stresses on the cracktip constraint. A modified boundary layer model with a remote displacement-controlled elastic K-field and T-stress under small scale yielding has been used to simulate the problem. A two-dimensional tensile residual stress field due to the weld is introduced into the model by the so-called eigenstrain method. It has been shown that the residual stresses can significantly elevate the crack-tip constraint and thus increase the probability for cleavage fracture. The constraint parameter R introduced by the authors can be used to rank the crack-tip constraint induced by the bi-axial residual stresses. The R value decreases with the increase in the applied J-integral. The residual stress-induced constraint is also coupled with the T-stress. The R value becomes smaller with larger T-stress.

Effect of residual stress on cleavage fracture toughness by using cohesive zone model

“…Cleavage fracture toughness exhibits a strong sensitivity to the local stress and deformation fields due to its highly localized character. Residual stresses affect both the crack driving forces and crack tip constraint, 1,3,4,6 which may further influence the cleavage fracture toughness. Therefore, the effect of residual stresses on cleavage fracture toughness was investigated in this study.…”

“…Residual stresses associated with welding are unavoidable and play an important role in structural integrity of engineering components. It has been shown that the residual stresses influence both the crack driving force 1 and crack‐tip constraint 2–4 . Crack‐tip constraint arises from differences in the level of opening stress near the crack tip and affects the transferability of material toughness, which is a key issue in application of fracture mechanics to assess the integrity of structural components 5 .…”

Two-parameter characterization of constraint effect induced by specimen size on creep crack growth

“…11. A negative Q means that the hydrostatic stress is reduced in comparison with the HRR field and the constraint level is low while a positive Q represents that the hydrostatic stress is higher and the constraint level is high [36,39]. It can be observed that the tendency of the Q with the C * is similar as the different r values are employed.…”

Fractographic Analysis of Weld Metal and HAZ Regions of API X-80 Steel Subjected to Simulation of the Reel-Lay Method

“…In all fracture surfaces, mainly on actual reel-lay condition and more severe than actual conditions, the results indicate a ductile behavior of WM and HAZ regions. Some works in the literature studied the influence of external loading combined with residual stresses originated from welding procedures on the crack tip stress field (Ref [24][25][26]. They show that the effect of residual stresses becomes negligible at high external loads due to the resulting decrease of the crack tip constraint induced by the residual stresses.…”