变厚度板中Lamb波传播的模态转换特性

Characteristic of Mode Conversion of Lamb Wave in a Plate with Variable Thickness

针对常见的阶梯型、斜面型和圆弧型厚度变化形式,定义倾斜角/弦切角为基本变量,采用有限元软件ANSYS分析了激励A0模态传播特性,研究了模态转换后产生的A0和S0模态反射系数和透射系数随角度变化的规律。分析结果表明,随着倾斜角/弦切角的增大,A0透射系数逐渐减小,A0模态转换产生的反射和透射的S0幅值随之增大,不同激励频率下A0模态的模态转换特性存在差别,并且圆弧型和斜面型变厚度结构的反射系数和透射系数存在一定的差值。为变厚度板结构缺陷检测的Lamb波散射信号分析提供了理论依据,有利于提高变厚度板缺陷识别的准确度。

Three typical thickness variations of plate-like structures are analyzed in this paper,the stepped,linear,and circular thickness variation.The angle is defined as basic variable,and the effects on the mode conversion behavior are investigated by using ANSYS software.The relationship between the reflection and transmission coefficients of turning modes A0 and S0 and the angle of linear slope and osculation is obtained.The results show that the transmission coefficient of A0 mode is decreased with the increasing of the angle,but the reflection and transmission coefficients of the turning modes A0 and S0 are increased.The excitation frequency has influence on the mode conversion behavior of the plate with variable thickness.There is certain difference of the reflection and transmission coefficients of the turning modes A0 and S0 between the linear and circular thickness variation.These results are significant to analyze the scattered signals of Lamb wave,thus can improve the accuracy of flaw detection of plate-like structures.