振动声调制技术下微裂纹的非线性响应分析

采用非线性弹簧模型对振动声调制技术下微裂纹产生的非线性调制效应进行解释。从理论上分析了振动声调制技术下微裂纹产生非线性调制现象的原理,将微裂纹的开合状态等效为非线性弹簧。利用有限元软件构建并仿真微裂纹非线性弹簧模型,分别观察不同激励下裂纹界面的开合状态及混合声波的传播特性。结果表明,微裂纹界面随低频声波呈周期性开合,使得通过裂纹界面的高频声波与低频声波相互调制而产生非线性现象。在以上研究基础上,开展振动声调制实验研究。对比仿真结果,非线性调制系数R在实验条件下和仿真随低频激励幅值的变化趋势相同,证明了该模型的正确性。该模型为振动声调制技术应用于微裂纹的超声非线性检测提供了理论依据。

Nonlinear response analysis of micro-crack under vibro-acoustic modulation

A nonlinear spring model is used to explain the nonlinear modulation effect of micro-crack in Vibro-Acoustic Modulation (VAM).Firstly,the opening and closing states of micro-crack are equivalent to the nonlinear spring,and the nonlinear modulation phenomenon of micro-crack under VAM is analyzed theoretically.Secondly,the nonlinear spring model of micro-crack is built by finite element software,and the VAM simulation is carried out to observe the crack interface opening and closing states and the propagation characteristics of mixed excitation sound waves.Finally,the experimental study of VAM is carried out,and the nonlinear spring model is verified by using the nonlinear modulation coefficient R.The results show that the micro-crack interface opening and closing periodically with low frequency acoustic wave,makes nonlinear phenomena will be generated according to the interaction between the high frequency sound wave from crack interface and low frequency sound wave.The nonlinear modulation coefficient has the same trend with the amplitude of low frequency excitation under simulation and experiment conditions,which proves the correctness of the model.The model provides a theoretical basis for the application of VAM to ultrasonic nonlinear detection of micro-crack.