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理论分析和实验研究了超声导波纵向模态在带粘弹性包覆层充液管道中的传播特性。得到了纵向模态的频散曲线。以此确定了适合带粘弹性包覆层充液管道缺陷检测的一定频带的纵向模态。经分析认为,频散小,衰减低的频带0～50 kHz的L(0,1)模态和未受干扰的L(0,2)模态分支部分,如频带170～210 kHz的L(0,4)模态,适合检测外直径25 mm,壁厚1．2 mm,外壁涂覆0．35 mm厚环氧树脂的充水钢管中的缺陷。而频散和衰减大,能量主要在水或环氧树脂粘弹性层中传播的纵向模态则不适合检测该类管道中的缺陷。
Theoretical analysis and experimental study of the propagation characteristics of ultrasonic guided wave longitudinal modes in viscoelastic cladding liquid-filled pipes. The dispersion curve of longitudinal mode is obtained. In this way, the longitudinal mode of a certain frequency band suitable for the detection of flaw detection in viscoelastic coating liquid-filled pipes was determined. The analysis shows that L (0,1) modal with 0 ~ 50 kHz frequency band and L (0,2) modal branch without interference such as low frequency band L 0,4) modalities suitable for detecting defects in water filled steel pipes with an outer diameter of 25 mm, a wall thickness of 1.2 mm and an outer wall coated with 0.35 mm thick epoxy resin. Longitudinal modes with large dispersion and attenuation and energy mainly propagating in water or epoxy viscoelastic layers are not suitable for detecting defects in such pipes.