超声Lamb波检测三维平板孔状缺陷的有限元模拟

Finite Element Method Simulation of Ultrasonic Lamb Waves Detecting the Hole Shape Defects in Three-dimensional Plate

通过数值计算求解Lamb波的频散特性方程,绘制钢板中Lamb波的频散特性曲线,分析不同模态Lamb波在钢板内的传播特性。基于ANSYS瞬态动力学分析方法,建立S0模态超声Lamb波检测钢板内孔状缺陷的有限元分析模型,通过群速度计算校核分析S0模态和SH0模态水平剪切波,得出其传播过程中振幅呈指数变化趋势。在孔状缺陷周围建立环形信号接收点,得到Lamb波作用缺陷后的散射特性和模态转化规律,散射波能量关于X轴对称分布,且随缺陷尺寸增加有增大趋势,透射波能量随缺陷尺寸增加而减小。

Byworkingout the Lamb waves dispersion characteristic equation by numerical calculation, the dispersion curves insteel plate were drawn, and the propagation of different modal Lamb waves in the steel platewas analyzed. Then the transient dynam-ics simulation based on ANSYS is used to analyze S0 modal Lamb waves to detect the three dimensional plate shape with inner holedefects, explorethe displacement nephograms in plate. By checking S0 modal and SH0 modal horizontal shear waves with group ve-locity calculation, the exponential trend of amplitude change was found in the spread process of these waves. Following the establish-ment of circular accept points around hole-shape defects, the Lamb waves scattering characteristics and modal transformation afterinteracting the defect were achieved. The scattering wave energy is distributed on X axial symmetry and increases with the enlarge-ment of defect size, while the transmission wave energy decreases with that.