考虑声源非线性影响下材料非线性系数测量研究

采用有限幅值法测量材料非线性系数,提出减少声源非线性影响以提高检测结果精度的方法。利用多元高斯声束模型,将准线性条件下探头产生的基波、二次谐波及声源非线性声场表示为纯平面波解、衰减修正项和衍射修正项组合的形式;通过设备输出的监测信号分析声源非线性值的大小;进一步修正了采用平面波理论计算非线性系数计算公式,得到消除声场衍射、声能衰减及声源非线性波影响下更加准确的计算方法。对6061铝试块进行非线性系数的测量试验,结果显示在消除声源非线性影响下,不同检测电压下的测量结果间误差在10%以内,相比于未考虑声源非线性时的结果,其精度得到了极大的提高。研究将为减少声源非线性影响以提高材料非线性系数的测量精度提供理论帮助。

Study on the Measurement of Material Nonlinearity Coefficient Taking into Account Nonlinear Effects of Sound Source

An approach to reduce the effect from source nonlinearity and improve the measurement accuracy is proposed when determine the nonlinear parameter of material using finite amplitude method. Based on quasilinear theory, the fundamental wave, second harmonic wave and source nonlinear wave sound fields are described as the combination of pure plane solutions, diffraction correction terms and attenuation correction terms using multi-Gaussian beam model. The amplitude of source nonlinearity is determined through the output monitoring signal of the equipment. The expression of determining nonlinear parameter based on plane wave is corrected, in order to reduce the effects from sound diffraction, attenuation and source nonlinearity. The nonlinear parameter of Al-6061 specimen is measured experimentally, and the results show that the errors of measured nonlinear parameter taking consideration of source nonlinearity in different input voltages are controlled in 10%. The precise has been of great improved compared with that without considering the source nonlinearity. This research will provide a theoretical method to reduce the effect from source nonlinear and improve the precise of nonlinear parameter of material in experiment.