Fracture Assessment of Axial Crack in Steel Pipe under Internal Pressure

Abstract

Fracture assessment of axial crack in steel pipe subjected to internal pressure is reviewed. Assessment results were obtained using different methods FC, GS and FAD in order to compare between their results and facilitate their use in any maintenance program. Material type and crack geometry are considered as the main two parameters controlling the failure of the pipe. The constitutive equation of the material is represented by the Ramberg – Osgood model. Six different half crack lengths (40, 60, 80, 100, 120,and 140mm) and four values of the ratio between the crack depth and the pipe thickness are considered (0.2, 0.4, 0.6 and 0.8). The relationship between the fracture parameters (i.e., stress intensity factor K and the J-integral) and the crack length for each assessment method is used. The material properties, plane strain fracture toughness KIc as well as the critical value of J-integral Jcr, are used to determine the critical crack size under specified internal pressure. The assessment method that gives smaller critical crack size is the one which is more conservative than the others. The results obtained by using GS and FAD assessment methods show this type of conservation.