316LN不锈钢高温拉伸颈缩区塑变行为

为准确测量颈缩发生后的应力-应变行为,本文综合物理实验、有限元模拟和MLR模型的方法确定颈缩区的塑变行为,建立316LN不锈钢高温本构模型.模型中,颈缩前的真应力-真应变呈幂函数关系,颈缩发生后,较低温度时应力随着应变的增加迅速下降,而当较高温度时应力随着应变的增加而缓慢下降,真应力-真应变呈非线性关系.基于MLR模型,修正了颈缩后不同温度、不同应变速率下的真应力-真应变曲线,并将有限元模拟的颈缩区长度与实测值相对比,相对偏差为4.73%.这说明修正后的应力-应变本构模型能够准确地描述316LN的高温塑性行为.

Behavior of plastic deformation and constitutive model of 316LN stainless steel at high temperature

In order to accurately measure the stress-strain behavior after necking,this paper determines the plastic deformation behaviors in the necking region and establishes the constitutive model of 316LN stainless steel at elevated temperature by using experiments, numerical simulations, and the model of MLR. In the new model, the true stress-strain before necking had a power function relationship. The true stress after necking decreased rapidly with the increase of strain at lower temperatures, while the stress decreased slowly with increasing strain at higher temperatures, in which the true stress-strain showd a nonlinear relationship. Further, the true stress-strain curves at various temperatures and strain rates after necking were modified based on the MLR model, and the length of the necking region of the finite element simulation was compared with the measured value, whose relative deviation was 4.73%. These results indicated that the established model could accurately describe the elevated temperature plastic behavior of 316LN stainless steel.