System Optimization of Metal Material Mechanical Performance Degradation Testing Using Nonlinear Ultrasonic

Material degradation is usually preceded by some kind of nonlinear mechanical behavior.When a single sinusoidal ultrasonic wave is launched to a nonlinear medium,the wave will be distorted as it propagates,so higher harmonics will be generated.But the ultrasonic nonlinearity parameter is very small and to be confused easily from measurement system nonlinearity.The project researched the measurement method of nonlinearlity parameters,developed a robust experimental procedure.Experimental system was optimized by the selection of instruments and design of test fixture.There is linear relationship between amplitudes of the second-harmonic waves and the squared fundamental waves as a function of increasing input voltage amplitude,the system is reliable.Using this method,ultrasonic nonlinearity parameters of a group of LY12 aluminum samples monotonic loaded were measured.The experimental results show that there is a significant increase in ultrasonic nonlinearity parameter linked to applied stress level;ultrasonic nonlinearity parameter can characterize the mechanical performance degradation degree of LY12 aluminum.