Application of fracture mechanics methods on cracked components at high temperatures

Even if components are manufactured with care and designed in compliance with regulations it is still possible for defects to occur (e.g. in the form of cracks). In addition to showing up manufacturing defects, in particular in welds, in service inspections on creep-loaded power plant components (T=5000C) reveal defects which arise in the course of operation and which are caused by creep damage and creep fatigue. In many cases it is possible to evaluate continued operation of a power plant component by applying methods related to fracture mechanics. The procedure for determining stable crack growth and critical defect sizes, are discussed. On the basis of a practical example the procedure adopted with fracture mechanics analysis together with the information which can be obtained are elaborated. (orig.)