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    基于全耦合连续损伤模型的30CrMo高强钢氢致断裂有限元模拟

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

    • 摘要: 采用氢扩散耦合弹塑性变形模型结合梯形张力位移法则,将氢致弱键氢脆机制引入内聚力单元中,建立了考虑氢扩散-机械变形与内聚力关系的全耦合连续损伤模型,模拟了30CrMo高强钢紧凑拉伸(CT)试样在含氢状态下的脆性断裂行为,并与试验结果进行了对比。结果表明:模拟得到CT试样的载荷-位移曲线和试验结果基本吻合,最大断裂载荷的相对误差在5%左右,说明建立的模型可以模拟30CrMo高强钢的氢致断裂行为。模拟得到静水应力梯度是晶格氢扩散主要驱动力,塑性应变是陷阱氢扩散的主要因素;当初始氢分子浓度较低(2.084×1012 mm−3)时,陷阱氢是30CrMo钢脆化的主要氢源;当初始氢分子浓度较高(4.739×1015 mm−3)时,晶格氢是裂纹尖端脆化的主要氢源;随着初始氢分子浓度的增加,晶格氢在裂纹尖端的富集程度增大,内聚力强度降低因子降低,内聚力单元强度降低,使得内聚力单元在较低应力状态下发生失效,裂纹萌生并扩展。

       

      Abstract: 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.

       

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