论文标题
关于晶体中张力的起源 - 压缩不对称及其对环状行为的影响
On the Origins of Tension--Compression Asymmetry in Crystals and Implications for Cyclic Behavior
论文作者
论文摘要
当机械地沿交替的方向加载时，大多数晶体材料在其变形曲线上表现出滞后。这种鲍森效应是原子量表上存在的机制的签名，并控制材料损坏并最终失败。在这里，微观结构演化的脱位动力学和统计分析的三维模拟揭示了两个原始基本机制。由应力驱动的曲率和塑料雪崩的部分可逆性引起的位错网络连接中的不对称性，可以解释FCC单晶体中观察到的牵引压缩不对称性。然后，使用基于脱位密度的理论将这些机制以物理上合理的方式连接到大规模表示。发现在不同材料和一系列载荷方向上的循环变形过程中的Bauschinger效应和应变硬化的无参数预测发现与实验非常吻合。这项工作为解释实验和设计结构组件的设计带来了宝贵的机械见解，以巩固其在循环负载下的使用寿命。
Most of crystalline materials exhibit a hysteresis on their deformation curve when mechanically loaded in alternating directions. This Bauschinger effect is the signature of mechanisms existing at the atomic scale and controlling the materials damage and ultimately their failure. Here, three-dimensional simulations of dislocation dynamics and statistical analyses of the microstructure evolution reveal two original elementary mechanisms. An asymmetry in the dislocation network junctions arising from the stress driven curvatures and the partial reversibility of plastic avalanches give an explanation to the traction-compression asymmetry observed in FCC single-crystals. These mechanisms are then connected in a physically justified way to larger-scale representations using a dislocation density based theory. Parameter-free predictions of the Bauschinger effect and strain hardening during cyclic deformation in different materials and over a range of loading directions and different plastic strain amplitudes are found to be in excellent agreement with experiments. This work brings invaluable mechanistic insights for the interpretation of experiments and for the design of structural components to consolidate their service life under cyclic load.
