充粘性液体管材中超声导波的应力分析

对超声纵向导波在充粘液管材中的应力分布进行了分析,并讨论了用各模式检测充粘液管材的最佳频厚积范围和检测位置。分析表明,随频厚积的增加,L(0,1)和L(0,3)模式的平面内应力在管外壁上的值由负向变为正向,而L(0,2)和L(0,4)模式面内应力的值则相反,变换方向的点恰好在各模式的下一高阶模式群速度最大时的频厚积点附近;而在管内壁上,法向应力分布曲线达到零点的位置恰好在各模式群速度最大时的频厚积点附近。在各模式群速度较大的频厚积区域内,该模式在管内外表面上的平面内应力较大,而法向应力较小,因此能量泄漏较小。故在各模式群速度较大的频厚积区域内,用该模式来检测充粘液管材较合适。

Stress analysis of ultrasonic guided waves in viscous liquid-filled pipes

The stress amplitude distributions of ultrasonic longitudinal guided waves in viscous liq-uidfilled elastic pipes system are investigated.The optimal location,optimal mode and its frequ-encythickness product(fd) for the test of pipes filled with viscous liquid are chosen according to the stress distributions.The results showed that the values of the in-plane stresses of L(0,1) and L(0,3) modes changed from negative to positive and that of L(0,2) and L(0,4) modes changed from positive to negative at the outer wall of pipe with increases of frequency.The fd value of change stress vibration direction of the mode is that where group velocity maximum of next higher mode has.At the inner wall of pipe,however,the position of the mode stress vibration approach to zero is at fd where group velocity maximum of this mode has.In a particular mode,within ranges of fd with larger group velocity,this mode has a large in-plane stress and small normal stress at inner and outer wall of the pipe,so the guided wave has little "leak" energy.Therefore,for a certain range of fd values,a mode with a larger group velocity should be used for the test of pipes filled with viscous liquid.