The Acousto-elastic Effect and its Use in NDE

The acousto-elastic effect describes the influence of an elastic strain state on the elastic properties of a metallic material and hence on the velocities of elastic waves propagating in the strained component. The effect is used to evaluate stress states by ultrasonic methods. This chapter summarizes the fundamental concepts, measuring techniques, and evaluation procedures of nondestructive ultrasonic methods to evaluate one, two, and three axial stress states of components. The state of the art is detailed by discussing results of applications in, e.g., bolts, sheets, gear parts, and turbine rotors. The applicability and limitations of such techniques will be discussed in detail.