Unveiling the rate-dependent shear instability mechanism is essential in evaluating the reliability and safety of materials under dynamic loadings. Herein, the strain rate-dependent plastic instability behaviors of 2A12 aluminum alloy with ring-shaped structure and different surface states were systematically investigated and analyzed. The stress softening was displayed in the stress-strain curves as the loading rate increased to a high level. The lubricated interface will induce the prominent shear instability property, followed by the fine-polished interface and coarse-polished interface. It is revealed that the initial interface state between specimen and bars not only influences the onset strain and the yield strength, but also determines the duration of plastic instability stage. The simulation results also indicated that the shear band runs through the two surfaces with different interface friction coefficients. The minor disturbance under quasi-static loading will be accelerated under dynamic loading owing to the instantaneous rising of local temperature, which eventually causes the observably plastic shear instability. The critical state of shear band formation mechanism and the modeling of the stress-softening stage were then theoretically analyzed and discussed. This work on the dynamic instability behavior of ring-shaped aluminum alloy could provide an insight in understanding the formation of adiabatic shear band with different strain rates and interfaces.

揭示速率相关的剪切不稳定性机制对于评估动态载荷下材料的可靠性和安全性至关重要。在此，系统地研究和分析了具有环状结构和不同表面状态的2A12铝合金的应变速率相关塑性失稳行为。当加载速率增加到高水平时，应力-应变曲线中显示出应力软化。润滑界面会引起明显的剪切不稳定性，其次是细抛光界面和粗抛光界面。结果表明，试件与钢筋之间的初始界面状态不仅影响初始应变和屈服强度，而且还决定了塑性失稳阶段的持续时间。仿真结果还表明，剪切带以不同的界面摩擦系数穿过两个表面。由于局部温度的瞬时升高，准静态载荷下的轻微扰动将在动态载荷下加速，这最终导致可观察到的塑性剪切不稳定性。然后从理论上分析和讨论了剪切带形成机理的临界状态和应力软化阶段的模型。环状铝合金动态不稳定性行为的这项工作可以为理解具有不同应变率和界面的绝热剪切带的形成提供一个见识。由于局部温度的瞬时升高，准静态载荷下的轻微扰动将在动态载荷下加速，这最终导致可观察到的塑性剪切不稳定性。然后从理论上分析和讨论了剪切带形成机理的临界状态和应力软化阶段的模型。环状铝合金动态不稳定性行为的这项工作可以为理解具有不同应变率和界面的绝热剪切带的形成提供一个见识。由于局部温度的瞬时升高，准静态载荷下的轻微扰动将在动态载荷下加速，这最终导致可观察到的塑性剪切不稳定性。然后从理论上分析和讨论了剪切带形成机理的临界状态和应力软化阶段的模型。环状铝合金动态不稳定性行为的这项工作可以为理解具有不同应变率和界面的绝热剪切带的形成提供一个见识。