Finite Element Simulation of Hydrogen Induced Fracture of 30CrMo High-Strength Steel Based on Fully Coupled Continuous Damage Model

The hydrogen diffusion-coupled elastoplastic deformation model combined with the trapezoidal traction separation law was adopted, and hydrogen embrittlement mechanism caused by hydrogen-induced bond weakening was introduced into the cohesive force element; a fully coupled continuous damage model considering the relationship between hydrogen diffusion-mechanical deformation and cohesive force was established. The brittle fracture behavior of 30CrMo high-strength steel compact tensile (CT) specimens in the hydrogen-containing state was simulated and was compared with the test data. The results show that the load-displacement curves of the CT specimens obtained by simulation were roughly consistent with the test results, and the relative error of the maximum fracture load was about 5%, indicating that the established model could simulate the hydrogen induced fracture behavior of 30CrMo high-strength steel. The simulation results show that the hydrostatic stress gradient was the main driving force for lattice hydrogen diffusion, and the plastic strain was the main factor affecting trap hydrogen diffusion. When the inital hudrogen molecular concentration was relatively low (2.084×10¹² mm⁻³),trap hydrogen was the main hydrogen source for embrittlement of 30CrMo steel. When the initial hydrogen molecular concentration was relatively high (4.739×10¹⁵ mm⁻³), the lattice hydrogen was the main hydrogen source for embrittlement at the crack tip. With the increase of the initial hydrogen molecular concentration, the enrichment degree of lattice hydrogen at the crack tip increased, the cohesive strength reduction factor decreased, and cohesion unit strength decreased, resulting in the failure of cohesion units under lower stresses and the initiation and propagation of cracks.