Nonlinear Ultrasonic Detection of Thermal Damage of P91 Steel

A nonlinear ultrasonic testing is implemented on P91 steel specimens thermal treated at different temperatures based on the theory of nonlinear ultrasound. The nonlinear parameter is calculated by analyzing spectrum of fundamental and second-harmonic at the same excitation conditions. The result shows that the nonlinear parameter increases with heat treatment temperature. The square of the fundamental amplitude and the second-harmonic amplitude have a good linear relationship. It is shown that the experimentally measured properties of the ultrasonic nonlinear only concerns with the nature of the sample itself. The test results showthat the nonlinear parameter can be used for material nondestructive evaluation.