研究了兰姆波在油气管道与B型套筒的搭接角焊缝位置的散射问题，建立了一个基于模式展开法的分析模型来计算特定频率范围内的散射系数，并由时域有限元模拟结合二维傅里叶变换方法验证了理论计算的准确性。结果表明，随着套筒尺寸或者角焊缝形状的变化，在频厚积为2 200~2 600 kHz ·mm时，a0模式总是能找到合适的频厚积以大于80%的能量通量进入套筒下方管道；s0模式在频厚积小于1 600 kHz ·mm时入射，能在套筒下方母材内获得最多37%~89%的能量通量。

Lamb wave scattering near a lap fillet weld was studied in a prospect to inspect the pipeline section under a B-type sleeve. An analytical model based on mode matching technique was developed and used for scattering-coefficients evaluation in a given frequency range. The results were verified by those obtained from time-domain finite element simulation and frequency and wave number analysis using two-dimensional Fourier transform. It showed that through the fillet weld, about 80% energy flux of a0 mode, or at most about 37%-89% of s0 mode might get into the sleeve-covered pipeline without mode conversion at 2 200-2 600 kHz ·mm or somewhere smaller than 1 600 kHz ·mm corresponding to the weld shape or sleeve thickness. The research may provide an entry for the sleeve-covered girth weld investigation.