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首页> 外文期刊>JSME International Journal. Series A >Discrete Dislocation Dynamics Study of Fracture Mechanism and Dislocation Structures Formed in Mesoscopic Field near Crack Tip under Cyclic Loading
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Discrete Dislocation Dynamics Study of Fracture Mechanism and Dislocation Structures Formed in Mesoscopic Field near Crack Tip under Cyclic Loading

机译：循环载荷作用下裂纹尖端附近介观场中断裂机制和位错结构的离散位错动力学研究

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摘要

In the present study, the 2-dimensional discrete dislocation dynamics (DDD) simulation is applied to crack tip field under cyclic loading. The crack is located on bcc (body centered cubic) iron subjected to the model I crack opening load. The crack front is taken in [110] direction and the plane strain assumption confines the number of active slip system to two ((112) [111], (112) [111]) of the 48 proper bcc slip systems. The angles θ between the slip direction and the direction of the crack extension are set 54.7 deg and 35.3 deg. The plastic deformations, obtained by different computational methods (molecular dynamics, DDD, and FEM based on crystal plasticity) in different scales are compared mutually. The shapes of plastic region, obtained by the DDD and the FEM based on crystal plasticity qualitatively correspond with each other. Under cyclic loading, the number of nucleated dislocations is almost balanced to the number of annihilated/disappearing dislocation so that the number of current dislocations is almost constant through the simulation. The cleavage stress at crack tip is increasing during this steady state. This seems to give some useful informations of ductile-brittle transition in fatigue crack extension by the DDD approach.
机译：在本研究中，二维离散位错动力学（DDD）模拟应用于循环载荷下的裂纹尖端场。裂纹位于承受I型裂纹张开载荷的密件抄送（体心立方）铁上。裂纹前沿是在[110]方向上取得的，而平面应变假设将活动滑移系统的数量限制为48个适当的密实cc滑移系统中的两个（（112）[111]，（112）[111]）。滑动方向与裂纹扩展方向之间的角度θ设定为54.7度和35.3度。相互比较通过不同计算方法（分子动力学，DDD和基于晶体可塑性的FEM）在不同尺度下获得的塑性变形。 DDD和FEM根据晶体可塑性获得的塑性区域的形状在质量上相互对应。在循环载荷下，成核位错的数量几乎与消失/消失的位错的数量平衡，因此通过模拟，当前位错的数量几乎恒定。在此稳定状态下，裂纹尖端处的劈裂应力增加。这似乎提供了一些有用的信息，即通过DDD方法进行的疲劳裂纹扩展中的韧性-脆性转变。

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