高应变率下U-5.7Nb合金的绝热剪切变形

利用分离式Hopkinson压杆实验和显微分析技术,研究了U-5.7Nb合金在应变率范围(102/s?104/s)内的变形特征和微观组织.结果表明:U-5.7Nb合金的动态屈服强度明显高于其静态屈服强度,表现出明显的应变率敏感效应;当U-5.7Nb合金应变率为4300/s,试件在应变达到64%时发生剪切破坏.材料内部形成了明显的绝热剪切带,剪切带在与压缩方向垂直的平面内呈环形,这与动态压缩过程中应力分布不均匀有关.

The adiabatic shear bands of U-5.7Nb at high strain rate

Split-Hopkinson pressure bar testing and microscopy were used to determine the dynamic mechanical properties and the microstructure in the strain rate range of 10~2-10~4/s for U-5.7Nb alloy samples. The experimental results showed that the dynamic yield strengths were higher than corresponding static values, and the failure was sensitive to the strain rate. Microscopic examinations revealed that the breaking (or breakdown) of specimen frequently occurred along the shear band at the strain rate of 4300/s and stress of 64%. A hemicyclic shear band appeared on the transverse section of the specimens, and this could be determined by analyzing the stress distribution.