耦合损伤的22MnB5热变形本构模型

Damage-coupled constitutive model of 22MnB5 steel in hot deformation

利用Gleeble 3500热力模拟试验机对22MnB5板材进行高温拉伸试验,研究了该材料在变形温度为700、800和900℃以及应变速率为0.01、0.1、1和10 s–1下的高温变形行为.在同一温度下,22MnB5的断裂应变随应变速率增加而呈现增加趋势,温度升高加剧这种趋势.建立了耦合损伤基于位错密度的统一黏塑性本构模型,该模型考虑了高温变形中损伤的演化规律,能够描述了应力–应变曲线后期的陡降段.利用遗传算法确定并优化该本构模型中的材料常数,所得材料常数确定的本构模型能够较好地预测22MnB5高温拉伸变形下的流变应力,并能较好地描述材料损伤演化规律.

The hot deformation behavior of 22MnB5 steel was investigated through tension testing on a Gleeble 3500 thermal-mechanical simulator, over a range of temperature from 700 ℃ to 900 ℃ and a range of strain rate from 0.01 s^-1 to 10 s^-1. It is found that failure strain of the steel increases with the increase of strain rate, and this trend is intensified as the temperature rises. A unified viscoplastic constitutive model coupled with damage, based on dislocation density and incorporated effects of strain, temperature and strain rate, was established to mathematically describe the steep-fall stages of the stress-strain curves. Material constants in the model were determined and optimized by a genetic algorithm. The model can accurately predict the flow stress of the steel in hot stretch and can describe damage evolution in the material.