Abstract：In order to identify the local damage of L-shaped pipeline, the local modal strain energy change rate index of the pipeline is obtained according to the vibration mode, stiffness matrix and natural frequency of the local structure, and the finite element software ABAQUS is used to simulate different parameter models, and the low-order modal data and the modal strain energy change rate of each element of the pipeline are obtained. The simulation results show that the damage location of L-shaped pipeline can be well determined by using this damage index, and the straight pipe element is more sensitive to this index than the bending element, and the comparison of different damage degrees of the same element can reflect the degree of damage. For different bending angles of L-shaped pipes, this index is universal for damage identification of L-shaped pipes with different bending angles. The different defect lengths of L-shaped pipes are simulated, and the modal strain energy change rate index reaches the limit when the defect circumferential length is 1/32.
