Ti-6Al-4V绝热剪切带的厚度及应变率效应研究

Theoretical Analysis of the Adiabatic Shear Band Width and Strain Rate Effect of Ti-6Al-4V

摘要:

通过引入与Batra及Kim类似的论点，将绝热剪切带宽度定义为绝热剪切带的中心区域的宽度(w5%)，在该区域上温度比其峰值小5%，利用Johnson-Cook模型及梯度塑性理论分析Ti-6Al-4V绝热剪切带的厚度及应变率的影响。计算表明，在名义应变率的下限(800 s-1)及上限(1400 s-1)之间，当绝热剪切带的总厚度选取为0.3235及0.0705 mm时，计算结果非常接近于绝热剪切带宽度的上限(55 μm)及下限(12 μm)。当应变率较低时，绝热剪切带较宽。随着应变率的增加，绝热剪切带宽度快速降低。在高应变率时，绝热剪切带宽度基本保持恒定。该理论结果与Dodd及Bai的理论结果有类似之处，与Weerasooriya及Beaulieu针对钨合金的实验结果非常一致，与Klepaczko及Rezaig的数值结果的前半部分相似

关键词:Ti-6Al-4V;绝热剪切带;应变率;梯度塑性理论;Johnson-Cook模型

Abstract:

The Johnson-Cook model and the gradient-dependent plasticity were used to investigate the width of adiabatic shear band (ASB) and the strain rate effect of Ti-6Al-4V. The ASB width was defined as the width (w5%) of the region surrounding the band center over which the temperature differed from its peak value by less than 5%, similar to the viewpoint proposed by Batra and Kim. The theoretical results show that the calculated ASB widths are closer to the lower bound (12 μm) and upper bound (55μm) measured in experiments when the nominal strain rate is in the range of 800 s-1 and 1400 s-1 if the total ASB widths are 0.3235 mm and 0.0705 mm, respectively. At lower strain rates, the ASB is wider. As the strain rate increases, the ASB width rapidly decreases. However, at higher strain rates, the ASB width approaches constant. The present theoretical result is similar to the analytical result by Dodd and Bai and very consistent with the experimental result of tungsten alloy by Weerasooriya and Beaulieu, and is similar to the former part of the numerical result by Klepaczko and Rezaig

Key words:Ti-6Al-4V; adiabatic shear band; strain rate; gradient-dependent plasticity; Johnson-Cook model