【作者】 何瑛；

【导师】 陈旭；

【作者基本信息】 天津大学 ， 化工过程机械， 2006， 硕士

【摘要】 对Sn-0.7Cu材料进行不同应变率下的单轴和扭转试验,材料的拉伸强度和饱和应力随应变率的减小而减小,表现出较强的应变率敏感性。进行了15种加载路径下的循环试验,包括拉压循环、扭转循环、多轴比例及非比例循环等。在相同的应变幅下,材料的应力峰值随应变率的减小而减小。相同应变率下,材料在不同应变幅下的等效应力峰值满足Ramberg-Osgood方程。与比例加载的结果相比,Sn-0.7Cu在多轴非比例加载过程中表现出明显的非比例附加强化和更为明显的循环软化现象,非比例强化和软化与加载路径相关。根据Sn-0.7Cu表现出的较强的率相关性,本文采用率相关的本构模型Bodner-Partom模型对试验结果进行了模拟。首先参考前人的研究成果,对材料在单轴拉伸和扭转试验中的试验结果进行了模拟,显示了模型优越的率相关性能。而后将模型用于模拟材料的单轴循环及多轴循环试验结果,与试验结果对比发现,模型能够较好的模拟材料的滞环形状,并能预测单轴循环过程中的应力峰值。对于研究无铅焊料在复杂工况下的应力-应变响应有一定的可行性。更多还原

【Abstract】 The uniaxial tests and the torsion tests at different strain rates were conducted on the Sn-0.7Cu solder. The tensile strength and saturated stress reduced obviously with the strain rates, and Sn-0.7Cu is rate sensitive material. Cyclic tests under different 15 loading paths were conducted on the Sn-0.7Cu solder including uniaxial, torsional, proportional and non-proportional cyclic loading. With the comparison of the test results, it can be found firstly that the stress amplitudes for the same strain amplitude reduced with the strain rates. The stress amplitudes at the same strain rates followed the Ramberg-Osgood equation. It can also be found that loading history has a great influence on the mechanical properties of the material. Compared with the stress-strain relationship under proportional loading, Sn-0.7Cu has the additional hardening and more cyclic softening under non-proportional loadings. The extent of the hardening and softening are related to the loading paths.Bodner-Partom model is used to simulate the stress-strain relationship of the Sn-0.7Cu solder. The parameters can be decided by tension tests. The comparison between the simulation and the test results shows that the visco-plastic model can reflect rate dependence of the material very well. Moreover, the shape of the hysteresis loop can be simulated well at the non-proportional tests. The Bodner-Partom model can be used in the simulation of the properties of the lead-free solder under complex loading conditions.更多还原