title: Detection of fatigue-induced micro-cracks in a pipe by using time-reversed nonlinear guided waves: a three-dimensional model study.
abstract: Localization of fatigue-related micro-cracks in pipelines is of increasing importance in industrial applications. A three-dimensional (3D) fatigue-crack imaging technique combining nonlinear guided waves with time reversal is proposed in this paper for potential applications in pipeline inspections. By using this method, the non-classical nonlinear guided waves generated from micro-cracks with hysteretic behavior are recorded, and the third harmonic waves are used to reconstruct the fatigue-crack images in a pipe by using a time reversal (TR) process. The feasibility of this method is examined by the imaging simulations for a steel pipe with varied defect areas. A finite-difference time-domain (FDTD) code is programmed to solve the wave equations under cylindrical coordinates, and simulate the experimental process of wave propagation. The results show that: (1) the proposed technique has excellent spatial retrofocusing capability; (2) the accuracy of defect localization and sizing depends on the crack orientation and the adopted guided wave mode; and (3) different displacement/stress components have varied sensitivities to the crack orientation.
authors.affiliation: Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Xiasheng
authors.initials: X
authors.lastname: Guo
authors.forename: Dong
authors.initials: D
authors.lastname: Zhang
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang