A Study on mechanisms of cleavage crack propagation of polycrystal metallic materials in crystal grain size level

晶粒级多晶金属材料解理裂纹扩展机理研究

• 批准号: 13450407
• 负责人: YOSHINARI Hitoshi
• 金额: $ 7.1万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13450407/
• 关键词: 2-D numerical simulation; cleavage crack; grain size; crack path; Charpy test; fractured surface; crystal texture; pop-in phenomena; 亀裂伝搬経路; ポップイン挙動; へい開破壊; 結晶粒; シャルピー試験片; 伝播シミュレーション

We studied on mechanisms of cleavage crack propagation in steels from mesoscopic view by 2-D numerical simulations and investigated the effects of some factors on crack path and morphology of the fractured surface. Assumptions used in simulations are that a crack propagates through cleavage plane of each grains and fracture initiation is dominated by maximum tensile stress of that plane. Stress field solutions of crack by FEM and the kink-crack analysis of Cottrel & Rice were used in simulation. For small scale yielding crack in the multi-axial stress mode, the solutions by Shih was used, too. The results simulated were compared with Charpy test and other fracture tests. As for the crystal grain diameter, fracture surface for random size of grains was rougher than constant one, and elastic-plastic cracks than elastic. Irregularity of fractured surface of cristal textures was increased as compared to the case of random distributed grains. These correspond with the experimental results from the viewpoint of tendency. Although the pop-in phenomena have been considered to take place by non-homogenious toughness of materials, it was shown that a small ckack could stop by only crack kinks. As far as crack is small, the above things can be said. But, when initial crack size is large, crack path becomes almost constant despite of grain sizes and cristal textures.

我们通过二维数值模拟从介观观察钢中的裂解裂纹传播的机制进行了研究，并研究了某些因素对断裂表面裂纹路径和形态的影响。模拟中使用的假设是，裂纹通过每种晶粒的裂解平面传播，裂缝起始和裂缝起始由该平面的最大拉伸应力支配。 FEM裂纹的应力场解决方案和cottrel＆Rice的扭结裂纹分析用于模拟。对于在多轴应力模式下产生裂纹的小尺度，也使用了SHIH的解决方案。将结果模拟与夏比测试和其他断裂测试进行了比较。至于晶粒直径，晶粒随机尺寸的断裂表面比恒定晶粒大，而弹性塑料裂纹比弹性裂纹比弹性。与随机分布式晶粒相比，Cristal纹理表面断裂表面的不规则性增加。这些与趋势的观点相对应的实验结果。尽管已经认为材料的韧性认为弹出现象是发生的，但表明只有一个小的ckack只能通过裂纹扭结来停止。就裂纹而言，可以说上述话。但是，当初始裂纹尺寸很大时，尽管晶粒尺寸和Cristal纹理，但裂纹路径几乎变得恒定。