Numerical simulation of square tube progressive folding process using enhanced continuum damage mechanics model

To evaluate the crashworthiness performance of automotive dual-phase steel sheet (DP1000), a comprehensive numerical investigation of square tube progressive folding is conducted using the Continuum Damage Mechanics (CDM) framework. A fully coupled damage model, accounting for the influences of stress state, temperature, and strain rate, is developed to capture both the plastic deformation and damage evolution. The proposed constitutive model is implemented into Abaqus/Explicit via user defined subroutine (VUMAT). Calibration of the plasticity and damage parameters is performed through an inverse method based on tensile and shear tests. Model validation is achieved by comparing finite element simulations of fracture predictions under various stress states with corresponding lab-level experimental measurements. During axial crushing of the thin-walled square tube, the stress state varies significantly at folding corners, where cracks readily form. Notably, the proposed model accurately reproduces the final crack path observed in the progressive folding process.