적층제조된 경사기능재료의 잔류응력 예측을 위한 다중 스케일 모델링

Abstract

In the present study, a multiscale modeling based on the inherent strain method was proposed for fast prediction of residual stress distribution in functionally graded material (FGM). The inherent strains of individual composition were defined by thermo-mechanical analysis with actual process parameters in a meso-scale model. Then the corresponding inherent strains in each composition was mapped continuously to a macro-scale model in the static mechanical analysis to obtain the residual stress distribution. Four types of specimens with different gradient paths and scanning strategies were prepared by directed energy deposition. The contour method, neutron diffraction and deep hole drilling were performed to measure the residual stress. The inherent strains of the composition composed of 50% 316L and 50% P21 powders were found that has smallest magnitude among the calculated compositions instead of exhibiting a gradual variation with the change of chemical composition. It was proved to be responsible for the fluctuation in the e sine-wave-like stress profiles in FGM structure. The effect of different lumping layer method for mapping the inherent strain to each composition layer on residual stress was also investigated and the results with selected layer lumping final showed an excellent agreement with the experimental results. For the computational efficiency, the total calculation time for each FGM structure with different gradient path is significantly reduced.