| 晶界及其临域在疲劳加载下的力学行为 | |
| 何文林 | |
| Thesis Advisor | 王中光 |
| 1989 | |
| Degree Grantor | 中国科学院金属研究所 |
| Place of Conferral | 中国科学院金属研究所 |
| Abstract | 本文使用微网络技术对大晶粒高纯铝试样在疲劳加载的不同循环周次时，晶界临域的塑性应变分布进行了研究，并结合微观力学对晶界领域的滑移不均匀和晶界滑动等现象做了分析。由于晶体是各向异性的，晶界领域的弹性应力场是不均匀的，因而开动不同于晶内的滑移系，而塑性滑移的不均匀更使应力场的不均匀程度和范围加大，三叉晶界处的应力集中尤为严重，因此产生晶界滑动。实验结果表明，晶内均匀开动的滑移系不产生严重不均匀的变形。而晶界领域的变形场是不均匀的，晶界滑动也是不均匀的。晶界滑动导致位移和应变的间断，并产生沿界面的切应变的峰值，其影响范围很小。晶界滑动有和滑移系相似的性质，有“软化”和“硬化”现象，与循环软化和二次硬化相对应。晶界滑动的控制因素不是Σ值，而是晶粒间的相对取向和晶界的宏观取向，取向与加载方向成45°角的晶界最容易滑动。 |
| Other Abstract | In this paper, the distributions of plastic strain near grain boundaries were investigated by the fiducial grid method for pure Aluminium specimens, which have been previously fatigued for certain cycles. The slip heterogenei ties and grain boundary sliding (GBS) during cyclic deformation, are analysed by micromechanics methods. Crystal is anisotropic, so the elastic stress field is heterogeneous near grain boundary. As a result, the different slip system is active in different area. The heterogeneities of plastic slip make the heterogeneities of stress more strongly and more widely. the stress concentration of triple node of grain boundaries is th strongest. That causes the grain boundary sliding. The test result shows that the homogeneous sliping does not cause the heterogeneous deformation in grains, but the strain field is heterogeneous near grain boundary, so is the GBS, GBS causes the discontinuity of displacement and strain, and a peak value of shear strain along the grain boundary. The affected area is small. GBS is similar to the slip system. It seems that the process of GBS in cyclic loading closely related to the cyclic hardening and softening of the material. It is found that the control factor of GBS is not mainly depend on the Σ value, but on the relative orientation between two grains and macro orientation of grain boundaries. The grain boundary which is along the 45 degree with the load axis slides the most easyly. |
| Pages | 68 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.imr.ac.cn/handle/321006/17401 |
| Collection | 中国科学院金属研究所 |
| Recommended Citation GB/T 7714 | 何文林. 晶界及其临域在疲劳加载下的力学行为[D]. 中国科学院金属研究所. 中国科学院金属研究所,1989. |
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