吸波边界对Lamb波在复合材料中传播的影响研究

STUDY ON THE INFLUENCE OF ABSORBING BOUNDARY TO THE PROPAGATION OF LAMB WAVE IN COMPOSITE MATERIALS

运用Lamb波对复杂结构进行结构健康监测时,经常需要对Lamb波传播过程进行有限元仿真,但由于建模大小、复合材料各向异性等原因,会产生较多的边界反射波,从而掩盖损伤波形,因此建立吸收边界抑制反射波的影响就显得尤为重要。使用加入弹簧阻尼器Combin14单元的吸波边界,研究了吸波边界长度、频率、Combin14单元方向等对该吸收边界吸波效果的影响,并通过与传统的阻尼递增吸收边界进行对比,发现频率和吸波边界长度对弹簧阻尼器吸波边界吸波效果均无过大影响,但其吸波边界长度必须大于λ(波长)才会达到最优效果;当Combin14单元设置在沿传播方向时的吸波效果最好;相较于阻尼递增吸波边界,弹簧阻尼器吸波边界的仿真耗时明显减少且在低频段的吸波效果更好。

When carrying out structural health monitoring on complex structures using Lamb wave,the finite element simulation of Lamb wave propagation process is usually performed.However,because of the size of the model,composite anisotropy and other reasons,much boundary reflected wave will produce and cover the damage waveform.Therefore,it is very important to establish the absorbing boundary to inhibit the influence of the reflected wave.This paper applies an absorbing boundary that incorporates Combin14 spring damper elements.The influence of several parameters to the absorption are studied.The parameters include the length of the absorbing boundary,the frequency,the direction of Combin14 element.And the results are compared with the traditional damping increasing absorbing boundary.The study indicates that both of the frequency and the length of the absorbing boundary have no effect on the absorbing effect of the absorbing boundary,but the wave-absorbing boundary length must be larger than that of wavelength to achieve the best absorbing effect.When the Combin14 elements are set in the direction of wave propagation,the absorbing effect will be best.Compared with the increasing damp absorbing boundary,the simulation time-consuming of the spring damper absorbing boundary obviously cut back and the absorbing effect is better in the low frequency band.