双层管结构中扭转模态传播特性的理论分析与实验研究

THEORETICAL AND EXPERIMENTAL RESEARCH ON PROPAGATION CHARACTERISTICS OF TORSIONAL MODES IN TWO-LAYER PIPES

通过分析不同的应力和位移边界条件得到了三种不同双层管结构中扭转模态的频散方程。不同结构中频散方程的阶次也不相同。并进行数值求解,得到相应的频散曲线。对不同双层管结构中扭转模态尤其是T(0,1)模态的主要传播特性进行了分析。然后,利用厚度剪切压电陶瓷片分别在这三种不同的管结构中进行了激励接收扭转模态的实验。实验结果与理论分析较为吻合。结果表明,利用全局矩阵法可以得到不同双层管结构的扭转模态频散方程,并且其频散曲线可用作模态选取的理论指导,用于这些管结构的缺陷检测。

Dispersion equations of torsional modes in three different two-layer pipes are obtained by means of analyzing different stress and displacement boundary conditions of these structures. It is found that the orders of dispersion equations vary with these pipe structures. All these equations are solved numerically. As a result, torsional mode dispersion curves of these three structures are shown respectively. Main propagation characteristics of torsional modes, especially T（0,1） mode are analyzed. Torsional modes in these different structures are excited and received using thickness shear mode piezoelectric transducers in the experiment. Experimental results are in good agreement with theoretical results. The results show that torsional dispersion equations of different two-layer pipes can be developed using the global matrix method, and their dispersion curves provide some theoretical guidance of mode choice for defect detection in these pipe structures.