声波在锥棒中非经典非线性传播及实验验证

弹性体材料在早期退化阶段会出现一些长度不同,且分布不均匀的介观尺度微裂纹,声波在这些裂纹聚集区(或裂纹群)传播会激发较强的非经典非线性。文中以缓变截面的锥棒为研究对象,在Preisach-Mayergoyz (PM)空间模型下研究了声波通过微裂纹聚集区激发的非经典非线性谐波传播特性,实验验证了三次谐波位移幅度与缺陷位置、宽度的反演关系。理论计算和实验结果表明:微裂纹群激发了较强的奇次谐波,引起非经典非线性传播;其谐波幅度与微裂纹聚集区域位置、宽度及非经典非线性参数紧密相关,利用三次或五次谐波位移幅度能够准确定位缺陷的区域。

Theoretical and experimental investigations of non-classical nonlinear acoustic propagation in a conical bar

There exist kinds of micro-cracks at mesoscopic size non-uniformly distributed in elastomer materials during early stage of degradation,which could induce strongly Non-classical Nonlinear Acoustic Wave(NNAW) propagation.The propagation of NNAW in a conical bar embedded with micro-cracks is investigated based on Preisach-Mayergoyz(PM) space model,and the exact equations for quasi-analytic harmonic excited by micro-cracked region are derived.The theoretical calculation and the experimental results show that the strong odd harmonics due to NNAW are obviously observed,whose displacement amplitudes are closely related to the position and width of the micro-cracked region as well as the strength parameter of the non-classical nonlinearity.Based on these characteristics of NNAW,the amplitude coefficients of the third(or fifth) harmonics are employed to discern and locate the micro-cracked region.