FEM simulations and optimization about residual stresses in coating structures with functionally graded materials layer

An elasto-plastic finite element method is developed to predict the residual stresses of thermal spraying coatings with functionally graded material layer. In numerical simulations, temperature sensitivity of various material constants is included and mixture law is used to depict the constitutive behaviors of FGM layer. The optimized distribution form of the volume fractions of constituents in FGM is obtained by the first order optimization method in the AL₂O₃-Ni system. At the same time, Effects of geometry and materials behaviors on the optimization result are also investigated numerically. When the length of specimen, the width of FGM layer and thermal expanding coefficient of the substrate material increase, the optimized distribution parameter p decreases obviously. It is found that the optimization of the constituent contents in FGM reduces the magnitude of residual stresses to a large degree and makes the maximum residual stresses to shun the weakest part of the coating structure.