Linear and Nonlinear Ultrasonic Properties of Fatigued 410Cb Stainless Steel

摘要

The assessment of pre-crack fatigue conditions is a problem of some importance in the nondestructive evaluation of turbine blades. Of particular concern to the electric power industry is the state of fatigue of steam driven stainless steel blades during the latter stages of service life prior to the nucleation of fatigue cracks. We report here measurements of acoustic attenuation, longitudinal velocity, and nonlinearity parameters on 410Cb stainless steel specimens provided by Virginia Power Company. Both virgin specimens and specimens from retired turbine blades were studied. From the virgin material a series of samples were prepared according to ASTM standards and cyclically fatigued from 0 to 10 million cycles at a tensile stress level of 85% of the yield strength of the material with an R value of zero. The results of the measurements are compared to that obtained from the retired turbine blade material.