Practical Applications of Numerical Procedures for Structural Integrity Assessment

Abstract

The paper presents two practical applications in which the weight function method is used to determine the stress intensity factor as the main structural integrity assessment parameter in linear elastic fracture mechanics. In this method, one may obtain the solution for the stress intensity factor for a given crack configuration and a certain loading, provided a complete solution (the Mode I stress intensity factor KIr(a) and the displacements of the crack faces uIr(x,a)) for the same crack problem is known in another loading case called the reference case. Three different cases can be encountered when the weight function method is used: i. The stress intensity factor KIr(a) and the displacement field uIr(x,a) are known; ii. Only the stress intensity factor KIr(a) is known and iii. Both KIr(a) and uIr(x,a) are unknown. In the first case, the method can be applied directly. This paper presents two practical applications for the second and the third case: Stress intensity factors for a strip with a cracked hole subjected to point loads (case 2) and stress intensity factors for an axially cracked thick walled cylinder subjected to internal pressure (case 3). For case 2, the reference stress intensity factors were first calculated using the compounding technique in a reference case (uniform remote traction). Then, an approximate expression of the displacements field found in the literature was used to calculate the weight function. In case 3, the authors propose a solution based on curve fitting of the crack face displacements obtained through finite element analysis. The obtained results were compared with the ones from the literature (where available). In all cases the agreement was very good, showing the reliability of the proposed solutions.