A Modified LTI ray tracing algorithm in Lamb wave tomography

Based on the analysis and comparison among existing ray tracing methods, a new modified linear traveltime interpolation (LTI) method is proposed in this paper. The developed method remains the virtue of LTI but is more precise than the original LTI. By analyzing the forward modeling and inversion process of the LTI algorithm, the backward ray tracing LTI algorithm is adopted. It can keep ray tracing from local minimum by computing the velocity of grid nodes in advance. Compared with original LTI, the new algorithm is able to compute the shortest ray path. Tomography based on the improved LTI traveltime data can reflect the size and property of the defect with high resolving power. The developed ray tracing technique for Lamb wave quantitative nondestructive evaluation is of great significance in both theory and practice.