Stress Intensity Factor Calculations For Semi-Elliptical Cracked Joints Using Finite Element AnalysisIn 3D

Abstract

Safety assessment tools are essential for components like pressure vessels and common pipes to minimize the risks during the service of components. All the real or practical materials contain defects or certain uncertainties and understanding the influence of these defects on strength or degradation in properties is necessary to predict the safe life of the components. In this work, material joining defects are considered as a crack according to their shapes and analyse how the crack initiated for the cyclic load conditions and how long the crack will propagate under fatigue loading conditions before final fracture (crack growth rate) was determined using Finite Element Analysis (FEA) which helps to determine the safe service life of the cracked surface components. StressIntensity Factor (SIF) at the crack tips are most important parameter for estimating fatigue life of components. Stress intensity factors values arepredicted from the parameters like CTOD, G, J-integral, and K. In this paper, J-integral approach is used to predict the Stress Intensity Factor values experimentally and the same values are compared with numerically obtained values for semi elliptical cracked surface componentsunder uniaxial tensile loading for constant R-ratio with different a/c (crack aspect) ratio. Crack front is assumed to have an elliptical arc shape during propagation of crack. In this work, conformal mapping technique is used for modeling the crack in 3D; because this model provides an idealmethod to use with relatively small number of degree of freedom without need explicitly mesh cracks. Numerical and experimental results, shows that the results are comparable and obtained values are within the acceptable deviations. From this research it is inferred that, this numerical method will be better tool to find the crack growth rates and predict the fatigue life of structural components and also for establishing inspection intervals for welded pipe joints.