管道超声纵向导波裂纹检测数值模拟

Numerical Simulation of Crack Detection in Pipes Using Ultrasonic Longitudinal Guided-Wave

简述了近年来超声导波技术的发展现状及其检测原理 ,并用有限元程序ANSYS对管道超声纵向导波裂纹检测进行了数值模拟。管道模型中 ,删除单元模拟管道周向裂纹 ,通过对管道一端端部周向各节点施加轴向瞬时位移载荷模拟纵向入射应力波 ,同端接收反射应力波 ,根据裂纹纵波回波信号到达时间和反射系数能较为精确地判断裂纹位置、周向开口裂纹长度、管壁减薄程度及裂纹截面积 ,但反射系数对管道轴向裂纹宽度不十分敏感。数值模拟结果与前人实验结果及理论计算结果吻合较好。

Brief review and the basic principle on researches of ultrasonic guided-wave in pipe were made. A simple formula was given and a finite element model with circumferentially oriented through-thickness crack of various length, as well as axial width, and part-through-thickness crack of various depth was used to simulate crack detection in pipes using ultrasonic longitudinal guided-wave. The crack was defined by the method of removing elements and wave-input simulated by prescribing axial displacements at one end of pipe, which was also the position of receiving echo wave from the crack location. The position, circumferential length, wall thickness reduction extent and sectional area of crack could be approximately determined by the reverse time of the reflection and reflection coefficient that was defined as the amplitude of the reflected signal divided by the amplitude of the incident signal multiplying the coefficient of correction. The results showed excellent agreement among numerical simulation, theory and experiments conducted by the former investigators.