Design and Application of Nonlinear Ultrasonic Programmable Power Attenuator

The nonlinear ultrasonic finite amplitude method can quantitatively measure the nonlinear coefficients of materials, thereby determining their mechanical properties. In the field application of non-destructive testing, it’s difficult to distinguish the system nonlinearity from the material nonlinearity in the results, which affects the resolution of nonlinear ultrasonic inspection. This article calculates the parameters required for a power attenuator and designs a programmable power attenuator. In automatic inspection, the amplitude of the excitation burst pulse can be adjusted step by step through a programmable power attenuator, and the amplitude of the fundamental frequency signal and second harmonic in the received signal can be measured. The amplitude of the second harmonic generated by material nonlinearity has a square proportional relationship with the fundamental frequency signal, the amplitude of the second harmonic generated by system nonlinearity has a linear relationship with the fundamental frequency signal. The quadratic term is used to fit the amplitude of the fundamental frequency and the amplitude of the second harmonic received under different excitation voltages. The experimental results show that in automatic detection, the attenuation rate of the programmable power attenuator can be adjusted step by step by PC program, and the fundamental frequency amplitude and second harmonic amplitude generated under different excitation amplitudes can be automatically measured multiple times. By using binomial fitting, material nonlinearity, system nonlinearity, and system white noise can be distinguished. At the same time, the error introduced by the programmable power attenuator itself can be ignored.