Engineering guide to assessment of creep crack initiation on components by Two-Criteria-Diagram

To assess creep crack initiation on components, it is necessary to consider the stresses at the crack tip as well as in the remaining ligament or farfield region. For that aim the Two-Criteria-Diagram was established. The method was proven by a large number of creep crack initiation results from small and large scale specimens as well as components. In this paper some practical aspects for using the Two-Criteria-Diagram are described. A code of practice for the use of Two-Criteria-Diagram for creep and creep fatigue loading is given. The extension to the latter and the limits of applicability are discussed. The determination of crack initiation in a cast steel containing defects is described as an example showing the advantages of the method for engineering applications.