# Numerical Evaluation of Residual Stress Influence on SIF in CT Specimen
###### Abstract  
Residual stresses are usually associated with stresses induced by heterogeneous deformations as a cause of phase transition and thermal stress. The residual stresses can appear during the manufacturing process, repair process, or in some cases due to operational loads. These stresses should be taken into account in the structural integrity evaluation of low-toughness materials or in the case of fatigue and/or stress corrosion cracking (SCC) situations. Indeed, it is known that residual stresses affect crack growth rates. For a better understanding of how these stresses can interact with crack propagation in pre-strained stainless-steel specimens, numerical modeling has been performed. The tension of the compact tension (CT) specimen was simulated and as a result, the stress intensity factor (SIF) was calculated. The main goal of this paper is to numerically calculate the stress intensity factors along the crack front of the CT specimen with residual stresses and compare them with the results of tension of the same specimen just without residual stresses. For this task finite element analysis (FEA), code CAST3M was used. Simulation results showed that the higher SIF values were calculated at the sides and the lower in the middle part of the CT specimen machined from a highly pre-strained plate which is opposite to what could be expected in a specimen without residual stresses. residual stresses; fracture mechanics; stress intensity factor; finite element method; FEM; SIF +
Footnote †: journal: Medical  
-veld seam failure. Therefore, it is important to know how the residual stress affects crack initiation and growth in the structural integrity analysis of weld seams. In this research, thermal loading was applied to the finite element (FE) model for the introduction of residual stress and evaluation of their influence on SIF values. Despite the significance of residual stresses, there has not been much research on the effects of combining crack closure mechanisms with residual stress distributions during crack propagation. Since both tension and compression stress values are present across the thickness, the crack closure can be described using the polynomial equation [7]. The main reasons for the rare investigation of the residual stress effect could be the difficult and long-lasting experimental stress measurements. Furthermore, it is difficult to predict the residual stresses accurately that arise from manufacturing procedures. Typically, in such cases, a nonlinear FE analysis is used. Due to the lack of accurate residual stress data in the components and structures, the integrity analysis based on fracture mechanic analysis is usually limited or too conservative. As a result, residual stress-bearing structures' structural integrity is evaluated cautiously, frequently, and very conservatively which frequently forces safe equipment out of service earlier than necessary and at a large expense [12]. According to this, it is important to estimate the influence of the residual stress on the behavior of defects in welded structures. [PERSON] and [PERSON] [13] using FEA analyzed how the defects in welds affect the cylindrical steel members structurally. As a result, non-axisymmetric buckling was determined close to regions with defects caused by an asymmetric distribution of residual stress. [PERSON] and [PERSON] [14] evaluated the weld residual stresses for cracked T-joints welded with a laser beam and calculated the stress intensity factor (SIF) using FEA with different crack shapes. The damage tolerance methodology was used for the determination of the weld joint's remaining lifetime. [PERSON] and [PERSON] [15] conducted a numerical non-linear 3D analysis to determine the residual stresses on welds of similar as well as dissimilar metals. It was concluded that the difference between the longitudinal residual stresses increases together with the yield strength of the parent materials in dissimilar steel welds.