On assessing damage in austenitic steel based on combination of the acoustic and eddy current monitoring

We suggest a methodology of assessing cyclic loading–induced damage in austenitic steel by combining the ultrasonic and magnetic monitoring. Cyclic loading increases the martensitic phase volume, thus enhancing the plastic deformation–and resulting damage–in the austenitic phase having lower strength and stiffness. The damage in the austenitic phase can be detected through wavespeeds changes. The latter, however, are small thus requiring high accuracy of wavespeeds measurements. These requirements are satisfied by focusing on ratios of the longitudinal and shear wavespeeds (that do not depend on imprecisely known parameters such as sheet thickness). In order to separate changes due to damage from the ones due to growth of the martensitic phase, we combine the acoustics- and magnetic data. Preliminary results on comparison with available experimental data are encouraging.