基于MUSIC及波束成形算法的非线性Lamb波微裂纹成像与评估

Nonlinear Lamb wave micro crack damage imaging and evaluation based on the MUSIC and beamforming algorithm

针对板状结构的微裂纹成像和评估问题,使用有限元分析方法在三维铝板中建立了埋藏型微裂纹,并采用对称激励的方式,在板中激励出S模态的Lamb波。利用多信号输入分类(multiple signal classification, MUSIC)算法,对传感器阵列捕捉到的信号进行处理,测算板中位于远场的微裂纹方向角。而后通过设置多组传感器阵列进行交叉定位,从而实现对板状结构中可能存在的微裂纹的大范围、高精度定位成像。以此为基础,对阵列信号进行波束成形算法处理,实现对信号的空间滤波,以减少其他方向的杂波对阵列信号的干扰;通过对处理后的阵列信号进行分析,计算其非线性参数,实现对裂纹损伤几何信息的评估。研究结果表明,该研究所构建的微裂纹定位成像算法在较高的环境噪声干扰下仍具备较好的损伤成像能力,且计算出的非线性参数与微裂纹厚度和宽度密切相关,可以有效评估微裂纹程度。

Aiming at the micro crack imaging and evaluation of plate structures, a buried micro crack damage was formed in a three-dimensional aluminum plate by using the finite element method, and the Smode Lamb wave was produced in the plate by means of symmetrical excitation. The multiple signal classification algorithm(MUSIC) was used to process the signals captured by the sensor array and to calculate the damage direction angle of far field micro crack. Then, multiple groups of sensor arrays were set to achieve large-scale, high-precision locating and imaging of micro crack damage in the plate by using cross positioning. On this basis, the array signal was processed by the beamforming algorithm to realize the spatial filtering in order, to reduce the interference of clutter signals from other directions. By analyzing the processed array signals and calculating its nonlinear parameters, the geometric information of the crack damage was evaluated. The results show that the constructed location imaging algorithm of micro crack damage proposed in the paper has excellent damage imaging ability in high noise environment, and the calculated nonlinear parameters are closely related to the thickness and height of micro crack, which can effectively evaluate the damage degree of micro cracks.