Early detection of creep damage by ultrasonic and electromagnetic techniques

Residual lifetime analysis of components of power plants requires information on the degree of damage in the material. In the case of creep damage in components such as pipe bends, it is necessary to detect damage at the stage of micropore formation in order to ensure safe operation. Bases on the influence of porosity on physical material properties (density, elastic moduli, electrical resistivity, coercivity), the potential of several NDT techniques for the detection of creep cavities is discussed,. Chages in density and elastic moduli can be traced by ultrasonic velocity measurements. Experimental results obtained so far under laboratory conditions show rather good agreement with theoretical estimations. The practical applicability of the techniques used has still to be demonstrated, which is the objective of further work.