Effect of residual stress on cleavage fracture toughness by using cohesive zone model
Fatigue & Fracture of Engineering Materials & Structures (Impact Factor: 1.56). 03/2011; 34(8):592 - 603. DOI: 10.1111/j.1460-2695.2011.01550.x
This study presents the effect of residual stresses on cleavage fracture toughness by using the cohesive zone model under mode I, plane stain conditions. Modified boundary layer simulations were performed with the remote boundary conditions governed by the elastic K-field and T-stress. The eigenstrain method was used to introduce residual stresses into the finite element model. A layer of cohesive elements was deployed ahead of the crack tip to simulate the fracture process zone. A bilinear traction–separation-law was used to characterize the behaviour of the cohesive elements. It was assumed that the initiation of the crack occurs when the opening stress drops to zero at the first integration point of the first cohesive element ahead of the crack tip. Results show that tensile residual stresses can decrease the cleavage fracture toughness significantly. The effect of the weld zone size on cleavage fracture toughness was also investigated, and it has been found that the initiation toughness is the linear function of the size of the geometrically similar weld. Results also show that the effect of the residual stress is stronger for negative T-stress while its effect is relatively smaller for positive T-stress. The influence of damage parameters and material hardening was also studied.
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ABSTRACT: An overview of past research on T-stress is presented in this paper. Beginning with the origin of T-stress, the authors discuss different phenomena associated with T-stress: crack path stability, isochromatic fringes pattern, plastic zone influence and constraint parameter. Different methodologies - experimental, analytical and finite element methods – used to evlauate T-stress are discussed and studies are categorized under these methods also. Thereafter, the authors provide a critical review for the role of T-stress in predicting crack paths stability because it conflicts with the origin of T-stress. Finally, it concludes with a concise summary of the research on T-stress.
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