Effect of Poisson’s ratio on KI, T11 and T33 for SENB and CT specimen – A FE study

Abstract

The level of constraint at a crack-tip/crack-front plays an important role in the fracture of the cracked component, and can be revealed by examining the details of the crack-tip/crack-front stress fields. Significant research on 2D crack-tip stress fields are available, however the real life cracks are 3D than 2D. There exists a gap in understanding constraint effects in different state of stress and 3D cracks. The Tij stress terms, together with the stress intensity factor (KI), can provide a set of practical parameters for the characterization of near crack-front fields, nominally K-Tij. A limited amount of investigation is done on understanding the effect Poisson’s ratio on these constraint parameters on standard specimens suggested by ASTM. The main objective of the current research work is to understand the effect of Poisson’s ratio on Stress Intensity Factor (KI) and corresponding Tij-Stresses for SENB and CT specimens. Using FE analyses for a/W ratio of 0.50 and specimen thicknesses were studied for different Poisson’s ratio for SENB and CT Specimen. It is observed from the current work that, in both, SENB and CT specimens, for same applied stress, the maximum magnitudes of KI is observed at the center of the specimen. KI and corresponding T11 are increasing with the increase in Poisson’s ratio of the specimen. However, the magnitude of T33 is reducing with the increase in Poisson’s ratio in both CT and SENB specimens. An effort has been put to generate polynomial formulations which approximately estimate the magnitudes of KI, T11 and T33. The values of KI and Tij obtained through these formulations are validated with the available experimental and FE results and a maximum error of 12% is observed.