Creep Damage Detection

Creep is an important factor in designing metal structures used at elevated temperatures. Dislocations again play a key role in deformation at elevated temperatures; they multiply, slip, form voids and subgrain boundaries, and annihilate. This chapter shows that the shear wave attenuation is highly sensitive to the dislocation activity in crept metals and the measurement of attenuation behavior with EMAR can predict the remaining life, especially the time when tertiary creep begins. This is true for many high-temperature materials. Acoustic nonlinearity is also demonstrated to be sensitive to the creep process, which is the subject of Chap. 10.