受载结构中SH_(0)波与裂纹作用的非线性散射场的数值研究

Numerical Study of Nonlinear Scattering Characteristics of SH_(0) Waves Encountering Cracks in Prestressed Plates

超声导波因具有传播距离远、能量衰减小等优点在结构健康监测领域中被广泛关注.厘清结构中导波与损伤作用后的散射规律,对于传感器阵列的设计和信号分析均具有重要意义.通过发展的数值方法,研究了受载结构中零阶水平剪切波(SH 0波)与微裂纹作用的接触声非线性作用规律.在双势谱方法的基础上,进一步通过mortar方法将谱单元和有限单元进行了耦合,以充分利用谱元法计算导波传播效率高的优点和有限元在离散复杂结构中的优势.利用该方法计算了板壳结构在自由状态和受载状态下SH 0波与不同角度微裂纹作用的非线性散射场.结果表明,SH 0波与裂纹作用后的二次谐波散射场关于裂纹面近似对称分布,并且单轴预应力不会改变二次谐波散射场的对称性,仍可以通过散射场的分布来确定微裂纹的取向.

Ultrasonic guided waves are widely used in structural health monitoring(SHM)for their long propagation distances and small energy attenuation.Understanding the scattering characteristics of guided waves encountering defects is essential for the design of transducer arrays and wave signal interpretation in SHM.The contact nonlinear scattering characteristics of the SH 0 wave(zero-order shear horizontal wave)encountering cracks in prestressed plates were investigated.Based on the previously developed bi-potential spectral method,the spectral finite elements(SFEs)and the finite elements(FEs)were further coupled with the mortar method to make full use of the high efficiency of the spectral element method in calculating guided wave propagation and the strong ability of the finite element method in discretizing complex structures.The nonlinear scattering fields of SH 0 waves interacting with microcracks at different angles in plates under free and loaded conditions were calculated with the developed numerical method.The results show that,the induced 2nd harmonic scattering field is approximately symmetrical with respect to the crack direction.Moreover,the existence of uniaxial prestress will not change the symmetry of the 2nd harmonic scattering field,so the orientation of the microcrack can still be determined by the distribution of the scattering field.