【作者】 魏志刚；

【导师】 汤文成；

【作者基本信息】 东南大学 ， 机械制造及其自动化， 2006， 硕士

【摘要】 本文首先比较全面的介绍了塑性成形有限元法的基本原理,对弹塑性材料本构模型,热传导分析,热应力分析,热机耦合分析,有限元接触问题,有限元网格重化分等的原理和分析方法做了较全面的介绍。对工件和模具建立弹塑性有限元模型,使用准静态的热机耦合分析,综合考虑各种热效应的影响,对星形套冷挤压成形过程进行数值仿真,较好的模拟出了工件的整个成形过程,得出了工件和模具的应力场、温度场、压力曲线,模拟出了工件成形后的弹性回复和得出了残余应力的分布。研究分析了材料模型、网格尺寸、摩擦系数对成形过程仿真的影响;分析了工件成形后弹性回复对工件尺寸精度的影响;工件成形后的残余应力分布,以及网格重画对单元体积的影响;比较了采用均布载荷和采用非线性分析模具应力场的差异。分析了模具应力分布,找到了模具应力集中的位置,找出了工件提前破坏的原因,对模具的结构进行了分析,改进了模具的结构;对改进后的模具和工件进行有限元分析,分析结果和实际情况符合良好,改进后的模具使用寿命有显著的提高。比较全面的介绍了疲劳破坏分析的基本理论,详细的阐述了局部应变法、疲劳裂纹扩展法的原理和寿命预测方法。采用线弹性有限元模型对结构重新建模,将结果导入MSC.Fatigue,根据模具有限元危险点的应力变化曲线作为载荷-时间历程曲线,采用应变寿命法对模具使用寿命进行了疲劳寿命预测,并采用裂纹扩展方法对疲劳寿命进行了研究。预测寿命与实际使用寿命基本相符。研究了成形过程仿真中存在的问题,各种疲劳分析方法在模具疲劳寿命分析中的应用,进一步探讨了解决成形过程仿真和疲劳寿命预测问题的方法,最后对成形过程仿真和疲劳分析中存在的问题做了总结,提出了可能的方案,并对将来有限元发展的方向做了预测。更多还原

【Abstract】 The primary theory of the plastic forming was presented at first: the constitution of the elastic-plastic material modal, thermal conduction analysis, the thermal stress analysis, the coupled thermal-mechanical analysis and the remesh method and so on were presented in detail.the process of the cold extrusion was simulated by the coupled thermal-mechanical analysis using elastic-plastic material modal, so the stress contour and thermal contour of the workpiece and the mold were gained and did also the equivalent plastic strain contour of the workpiece and the extrusion force. These results make good agreement with the reality.The influence of the material modal ,the frictional coefficient, and the element size to the simulation, the release of the elastic deformation to the size of the workpiece were analyzed and compared ,the residual stress in the modal and the volume lost due to the remesh were also be studied.The distribution of the stress in the mold was analyzed and the reason of the stress concentration in the mold was find out. The structure of the mold was modified; the simulation of the process wad conducted again. The analysis result complies with the reality. The service life of the mold improved significantly.The fatigue theory was introduced in detail and the strain fatigue method was presented in detail especially. The linear elastic finite element modal was built according to the stress distribution,the analysis of the stress result was conducted with the fatigue analysis software and the analysis was conducted with the load history in the dangerous area was applied,the service life was predicted by the FEA,these results make good agreement with the real life of the mold.The shortcoming of the analysis was presented, the solution of the plastic foming simulation and fatigue problem was further studied. The summarization of these questions which lie in the analysis was made, the advancing trend of the problem solution was described in the end.更多还原