中文摘要：

利用MARC有限元软件，按不同模式波结构分布在有限元模型上进行位移加载，得到了单一的A0，SO模式。同时，模拟了A0，SO模式在2mm薄板中的传播过程，绘制了缺陷回波反射系数与缺陷尺寸的关系图，并对模拟结果进行了试验验证。试验结果表明：采用波结构位移加载方式能够激励出单一模式Lamb波，结合有限元方法识别缺陷尺寸具有可行性，且不同振型模式波对缺陷尺寸敏感程度不同，其A0模式对缺陷尺寸敏感，而S0模式难以识别缺陷尺寸。

英文摘要：

MARC finite element software was used to obtain the single mode A0 and S0, which was achieved by loading displacement based on the distribution of different mode wave structures in finite element model. In addition, the propagation process of A0 and SO mode wave in 2mm sheet was simulated, and the diagram between the reflection coefficient of defect echo and defect size was also drawn. And then, the simulation results were verified by the practical experiment. The results showed that the excitation of single mode Lamb wave could be achieved by the displacement loading of wave structure. It was feasible to estimate the defect size combined with finite element method. The sensitive degree of different vibration modal on defect size was different. The A0 mode was sensitive on defect size, whereas the defect size was unable to be identified by SO mode.