Efficient reduced-order model for multiaxial creep–fatigue analysis based on a unified viscoplastic constitutive model

Abstract

This paper devises an efficient reduced-order model based on a unified viscoplastic constitutive model for predicting creep–fatigue behavior under multiaxial loading. In the preprocessing stage, the first cycle is numerically simulated using the unified viscoplastic constitutive model, and all element damage variables are recorded as representative variable snapshots. The orthogonal basis of damage is extracted by proper orthogonal decomposition and used as the interpolation function. The reduction elements are selected by minimizing the interpolation functions and damage variable samples. When predicting the subsequent cycles, the unified viscoplastic constitutive model is only applied to the selected reduction elements to evaluate the local damage, and the damage of the remaining elements is directly reconstructed using interpolation functions. In this manner, the computational cost of the constitutive equation is significantly decreased. Two reduction element selection strategies based on the damage rate and the damage are compared, which reveals that the extrapolation ability of the damage rate is more reasonable than that of damage. The feasibility of the devised model is validated through a comparison with the results of multiaxial loading tests. This demonstrates that the model accurately describes the creep–fatigue damage evolution while enhancing the computational efficiency.