Quantifying creep damage in a metallic alloy using acousto-ultrasonics

Due to elevated temperatures and excessive stresses, turbine components may experience creep behavior. As a result, it is desirable to monitor and assess the current condition of such components. This study used the acousto-ultrasonics (AU) method in an effort to monitor the state of the material at various percentages of expended (i.e., used-up creep life) creep life in the nickel base alloy, Udimet 520. A stepped specimen (i.e., varying cross-sectional area) was used, which allowed for a post mortem nondestructive evaluation (NDE) analysis of the various levels of expended life. The overall objectives in this study were two-fold: First, a user-friendly, graphical interface AU system was developed, and second, the new AU system was applied as a NDE tool to assess distributed damage resulting from creep. The experimental results demonstrated that the AU method was able to detect material changes as a function of expended creep life.