含单个位错的颗粒晶体的稳态剪切流变学
Steady shear rheology of a granular crystal containing a single dislocation
浏览论文内容
中文总结 AI 辅助
研究含单个位错的颗粒晶体稳态剪切流变，发现应力比由归一化位错速度而非惯性数决定，明确了颗粒间摩擦与接触阻尼在不同速度区间的作用，为位错介导颗粒流的流变学研究提供了关键速率变量。
中文摘要 AI 辅助
单分散颗粒可形成晶体，其屈服行为受位错影响显著，与传统无定形颗粒材料的屈服行为明显不同。然而，其屈服后稳态流变学的速率依赖性仍不明确。我们采用离散元法研究含单个位错的颗粒晶体中的稳态剪切，发现稳态剪切应力与法向应力之比μ_b由归一化位错速度v_d/v_s决定，而非传统的惯性数I。其中v_d通过奥罗万运动学与施加的剪切速率相关，v_s为特征赫兹弹性波速。在低v_d/v_s时，应力比趋近于与弹性晶格势垒及颗粒间摩擦相关的小平台；在中等v_d/v_s时，接触阻尼强烈影响应力比在平台之上的近似线性增长；当v_d/v_s趋近于1时，应力呈现更强的非线性速度依赖性；在更高速度下，配位数缺陷急剧上升，标志着晶体有序性的破坏及单个位错描述的终结。这些结果确定了归一化位错速度是位错介导颗粒流稳态流变学的相关速率变量，并阐明了颗粒间摩擦和接触阻尼分别在低速和中速 regime 中的不同作用。
英文摘要
Monodisperse granular particles can form crystals whose yielding behavior is strongly affected by dislocations and differs markedly from that of conventional amorphous granular materials. Yet the rate dependence of their post-yield steady rheology remains unclear. We use the discrete element method to study steady shear in a granular crystal containing a single dislocation. We find that the steady shear-to-normal stress ratio $μ_b$ is organized by the scaled dislocation velocity $v_d/v_s$, rather than by the conventional inertial number $I$. Here, $v_d$ is related to the imposed shear rate through Orowan kinematics, and $v_s$ is a characteristic Hertzian elastic-wave speed. At low $v_d/v_s$, the stress ratio approaches a small plateau associated with the elastic lattice barrier and interparticle friction. At intermediate values of $v_d/v_s$, contact damping strongly affects the approximately linear increase of the stress ratio above the plateau. As $v_d/v_s$ approaches unity, the stress develops a stronger nonlinear velocity dependence. At still higher velocities, the coordination deficit rises sharply, marking the breakdown of crystalline order and the end of the single-dislocation description. These results identify the scaled dislocation velocity as the relevant rate variable for the steady rheology of dislocation-mediated granular flow and clarify the distinct roles of interparticle friction and contact damping in the low- and intermediate-velocity regimes, respectively.
