Damage Identification Of Pipe Based Onprestack Reverse-time Migration Technique

Pipe structures are widely used in modern industrial transportation. The damage of pipe structures would lead to serious accident and economic losses. As a consequence, it is necessary to detect and monitor the health status of pipes. The nondestructive testing methods based on ultrasonic guided wave have attracted a large attention since it is rapid, economical and suited to large range detection.In this study, the crack on an isotropic pipe is detected with a surface-mounted piezoelectric wafers array. The prestack reverse-time migration method is employed for imaging damage.Firstly, the dispersion equations and propagation of axial guided wave in isotropic hollow pipe are reviewed. With the normal mode expansion method, under the asymmetric loading, the amplitude coefficients for the harmonic modes are obtained. The displacement distribution is also discussed.Secondly, the basic principle of prestack reverse-time migration technique is introduced. And the propagation of torsional wave in isotropic aluminum pipe is modeled.Finally, d31 and d36 type piezoelectric wafer array are used to detect the damage on the pipe respectively. Migration technique is performed in ANSYS to back-propagate the reflecting wave to the crack. The location and dimensions of the damage is obtained by excitation-time imaging condition. The image of damage validates the feasibility and effectiveness of this method on the pipe structure.