Calculation of stress intensity factors for cracks in thick-walled cylinders using weight functions

摘要

Recently published sales for construction of high pressure vessels (ASME Code, Sect. VIII, Div. 3,1998) allow one to perform fracture mechanics analyses using the weight function method for all types of cracks. When the weight function for a particular crack and body geometry is known, stress intensity factors for the crack subjected to arbitrary elastic stress distributions can be calculated. The method is usually faster than detailed finite element or other numerical stress analysis approaches and particularly suitable for fatigue crack growth analysis when considering steep stress gradients, pressure in the crack, and/or residual stresses. The paper outlines two weight function techniques that have been used to estimate the opening mode stress intensity factors, K{sub}I, for cracks in thick-walled cylinders: the O-integral by Oore and Burns (1980a,b), and the weight function method by Shen and Glinka (1991a). An overview of solutions obtained with these weight functions for cracks at internal and external surfaces of a cylinder, as well as thread roots and cross-bores, is presented; in some cases K{sub}I values obtained with weight functions are compared with K{sub}I values obtained using other techniques. The paper also mentions recent developments in each of these methods. Also, new Shen and Glinka weight functions for external radial-longitudinal surface semi-elliptical cracks in cylinders with diameter ratios of D{sub}0/D{sub}i=1.25 and 1.5 are briefly discussed. These new weight functions are discussed in detail in a companion paper at this conference (Kiciak et al., 1999). They complement the solutions published previously for D{sub}0/D{sub}i=2.0 (Kiciak et al., 1997).