| Abstract: | Requirements by Fracture Mechanics on Nondestructive Testing Methods Fracture mechanics is a tool in evaluating the magnitude of critical flaws in structures. By means of Material properties such as fracture toughness, subcritical flaw growth, and existing primary and secondary stress it becomes possible to evaluate critical values for given flaw configurations. In Section XI, Appendix A of the ASME-Nuclear Pressure Vessel Code allowable flaw dephts are usually determined as a function of flaw configuration and localisation and wall thickness. Thus one wants to enable a fracture mechanical assessment of detected defects and of the safety of a component against brittle and tough fracture. Besides, it shall be possible to get an idea about the subcritical flaw growth. Therefore Practical application of fracture mechanics is based on progress in nondestructive surveillance methods. In the presented work the guidelines for integrity assessment of flawed structures based on Appendix A are described and the problems relating with fracture mechanical approaches are outlined. Up to this day it is not possible to get quantitative statements about the configuration, localisation and magnitude of flaws in structures by means of non destructive testing. Therefore factors of safety are introduced with the goal of assuring the integrity of flawed structures. |
