Acousto-elastic measurement of the fatigue damage in waspaloy

It has long been speculated that second-order effects should prove an effective measure of a material's fatigue and damage state. One such second-order effect is the acousto-elastic effect. In a series of experiments on the nickel-based superalloy waspaloy, the change in the acousto-elastic coefficient of Rayleigh waves was monitored as the material was fatigued. Our results demonstrate the possibility of using this variation as a mean of measuring fatigue in waspaloy. They also show that waspaloy demonstrates a significantly different acousto-elastic behavior than that expected from a metal. This fact enhances the sensitivity of the technique in this material. It is interpreted as being due to load transfer between the two major phases found in waspaloy, the matrix phase (γ) and the strengthening phase (γ′).