Proposal Method To Calculate T-stress By Modified Stress Difference Method (msdm) For Specimens With U-notches

The importance of the two-parameter approach in linear elastic fracture mechanics analysis is increasingly being recognized for fracture assessments in engineering applications. The consideration of the second parameter, namely, the elastic T-stress, allows estimating the level of constraint at a crack or notch tip. It is important to provide T-stress solutions for practical geometries to employ the constraint-based fracture mechanics methodology. In the present research, T-stress solutions are provided for a V-shaped notch in the case of surface defects in a pressurised pipeline. The V-shaped notch is analyzed using the finite element method by the commercial Castem2000 software to determine the stress distribution ahead of the notch tip. The notch aspect ratio was varied in the following range a/t = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 and 0.7. The notch-tip radius was fixed for all geometries and equal 0.25 mm. In contrast to a crack, it was found that the T-stress is not constant and depends on distance from the notch tip. To estimate the T-stress in the case of a notch, a novel method, inspired from the volumetric method approach proposed by Pluvinage, has been developed. The method is based on averaging the T-stress over the effective distance ahead of the notch tip. The effective distance corresponds to the point with a minimum of the stress gradient in the fracture process zone. This approach was successfully used to quantify the constraints of notch-tip fields for various geometries and loading conditions. Moreover, the proposed T-stress estimation creates a basis to analyse the crack path under mixed mode loading from viewpoint of the two-parameter fracture mechanics.