两列同向共线纵波混叠的数值研究

A numerical study of co-linear mixing of two longitudinal waves

针对大型复杂装备的早期微弱疲劳损伤进行识别和评估这一亟待解决的问题,基于高阶弹性模量分析的非线性超声无损检测方法由于对疲劳导致的微观结构改变具有敏感性而在近年引起关注。针对两列同向共线纵波混叠的情形,运用高分辨率的半离散中心差分方法,对波束混叠法这一新型非线性超声无损检测方法在评价材料早期疲劳损伤的应用开展了数值研究。通过对谐振波成分的传播特性的分析可见,差频与和频谐振波成分可以同时在两个相互垂直的方向上产生和扩展,而其中剪切方向产生的差频谐振波成分能够随材料非线性系数而单调递增,从而可以对材料非线性进行准确测量,进一步为波束混叠法在材料早期微弱疲劳损伤损伤检测中的应用提供有效的方法和依据。

It is an urgent problem to identify and evaluate early weak fatigue damage of large complex equipment,and nonlinear ultrasonic nondestructive testing techniques based on the higher-order elastic modulus have aroused much attention in recent years because of their sensitivities to micro structural changes.Using a high-resolution semi-discrete central scheme,the ultrasonic wave mixing,a novel nonlinear ultrasonic nondestructive testing technique,was numerically investigated in the case of collinear wave mixing of two longitudinal waves in the same direction.The results of the generated components of resonant waves show that,both components of sum and different frequencies can be produced and propagate in two mutually perpendicular directions,and the component of different frequency brought about in the shear direction increases monotonically with material nonlinearity,which potentially offers an accurate measurement of material nonlinearity,and further provides effective methods and evidence for early weak damage of materials using the ultrasonic wave mixing technique.