声波在有裂纹的固体中的非经典非线性传播

固体材料的无损检测是一个非常重要的课题,带裂纹的固体材料显示非经典非线性声学现象,本文对此现象进行了实验和理论研究。从实验上一维观察到此现象,发现奇次谐波振幅与基波振幅呈平方关系,与理论预计基本吻合;理论上从二维的角度数值模拟了声波在有损耗的带裂纹的固体中的声传播,并讨论了经典非线性和非经典非线性对声传播的影响,发现裂纹的贡献主要体现在非经典非线性上。分析了样品中裂纹的宽度和位置与非线性声参数的关系,在靠近样品中心的两个对称区域以及距离声源较近点,非线性声参数对样品的破损较为敏感,而在中央和距声源最远端敏感性较低;随着裂纹宽度的扩大,非线性声参数也开始变大,但在破损区域蔓延到棒边缘之前,有下降的趋势。 

Nonclassical nonlinear sound transmission in solid with cracks

Non-destructive Testing(NDT) for solid is a top subject.Nonclassical nonlinear acoustic phenomena are shown in solid with cracks.In this paper,the propagation of sound wave and the nonclassical nonlinear acoustic properties in solid were studied theoretically and experimentally.The nonclassical nonlinear phenomena were observed experimentally in one dimension,the quadric relationships between the amplitude of odd harmonics and that of fundamental frequency were found,which were in agreement with the theoretical prediction.The sound transmissions through solid with dissipation and crack were simulated in two dimensions,the influence of classical nonlinearity and nonclassical nonlinearity on the sound propagation was discussed.And the crack was mainly contributed to the nonclassical nonlinearity.The relationship between the nonlinear parameter and the position and width of the crack was analyzed. The nonlinearity parameter was sensitive when the crack was at the symmetrical position near the center of the bar or near the source.However,there was no sensitivity to crack at the center of the bar or far away from the source.With the increase of width of the crack,the nonlinearity parameter also increased,however,it decreased before the crack was extended to the edge of the bar.