Damage identification method for functionally graded Timoshenko beams

To acquire high precision damage identification method for functionally graded materials, based on the state space variable replacement, the transfer matrix of the functionally graded Timoshenko beam along the axial exponential distribution is obtained. By analyzing the influence of crack on the local flexibility of structure, the contribution of the crack to the local stiffness of the structure is simulated by the torsion spring. The surface crack transfer matrix of functionally graded Timoshenko beams is established. And the theoretical model of multi-span beam under complex boundary conditions is derived. In this paper, the nonlinear equations are transformed into a single objective function optimization problem. The generalized Lagrange algorithm and differential evolution algorithm are combined to identify the damage of the structure. Computational examples show that the proposed algorithm has the characteristics of high precision and fast convergence and is suitable for damage identification of multi-damage model under complex boundary conditions.