【作者】 陈昆；

【导师】 陈定方； 刘金华；

【作者基本信息】 武汉理工大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 金属塑性成型过程模拟是实现短周期内,以较低成本设计出参数合理的模具,并制订较优的工艺参数,生产出高质量产品,它可以实时描述整个金属塑性成型过程。成功实现挤压成型工艺的过程模拟,依赖于诸多因素,包括型材和模具尺寸、材料本构关系、摩擦、温度、挤压速度、加热长度等。管材缩径成型技术是加工轴管类零件的一种新工艺,整体热挤压轴管成型技术能极大地提高生产率,降低成本,具有显著的经济效益。汽车后桥是典型的阶梯轴管零件,采用空心管材毛坯整体缩径成型技术是改变我国国内汽车后桥生产工艺水平落后的有效方法。本文分析了国内外的研究现状,在阅读和查证大量相关文献的基础上,分析和研究了金属塑性成型和热力耦合计算的理论公式和有限元算法,并借助了多种数学处理方法,主要取得如下研究成果:(1)研究了金属在高温下的流动应力应变特性,根据商业热挤压有限元软件Deform材料库中所提供的金属流动应力、应变、应变率和温度的关系数据对高温金属材料的本构方程进行数值拟合,采用线性回归的方法进行相关性分析,可根据部分高温段的材料特性数据,得到金属在高温下的材料特性本构方程,预测其他邻近高温段的材料特性数据。从而减少因材料库数据不够齐全而只能用插值法得到临近温度段的应力、应变数据所造成的计算误差,得到比较准确的有限元模拟结果。(2)针对管材缩径成型主要是通过一次或多次缩径得到理想的阶梯形状的毛坯件的特点,本文建立了一次缩径和两次缩径两个基本模型;论述了采用Ansys/Ls_Dyan软件进行热力耦合塑性成型的求解方法,并利用两个基本模型对著名的古布金公式进行修正,提出了适合管材挤压的挤压力计算公式,并对大量的工况计算结果进行了数据验证,在模具角度大于80°时误差都在20%以内,可相当准确地计算挤压力。(3)针对一次缩径成型和两次缩径成型,综合研究了挤压速度、摩擦系数和工件预热温度对成型质量的影响,并通过大量数据采集和分析,提出了针对一次缩径成型和两次缩径成型的成型质量评价公式,可直接根据工艺参数来预测成型件质量,减少新产品的试制工作量,缩短开发周期。(4)模拟了汽车后桥桥壳的两步成型。研究了桥壳成型过程的毛坯加热长度和润滑条件对成型和壁厚的影响。验证了本文提出挤压力公式的实用性,对汽车后桥桥壳挤压两步成型分别运用第五章提出的两个成型指标评定公式进行结果验证,效果良好。更多还原

【Abstract】 By the simulation of metal deforming, the die with optimized parameter and the product with high quality could be got at lower cost in short period. The entire process of metal deforming could be described. Many facters should be considered and corresponded, such as material, die size, friction, temperature, speed of extrusion and the heat up length of blank, in a successful simulation of metal deforming.It was a new technics that axle-pipe accessory was got by the shrinking of pipe material, with the process of hot extrusion, the productivity could be improved evidently and the cost could be down. The benefit of economy is immense. Behind bridge of automobile, is a typical axle-pipe accessory. The manufacture method of behind bride could be improved with the technology mentioned above. Based on the analyzing of the domestic and foreign research status, two aspect, theoretic formula and finite element method of metal deforming and the coupling calculation with thermal structure., were analyzed. Some mathematic processing.methods were used in the research. The main research works are as follows:(1) The flow stress, strain characters and their sensitivity to temperature was analyzed. According to the material library data in Deform software, the multiple linear regression method was used to do the numerical fitting of the metal material in high temperature. The limitation of the simulation calculation with insufficient material method could be avoided and more accuracy result could be got.(2) Based on the characteristics of shrinking pipe material, two basic models were set up. ANSYS/LS_DYNA was used in the research, In the text, the affection to extrusion force of the parameters such as extrusion temperature, extrusion speed, coefficient of friction and mould angle were analyzed with two mould mentioned above, and a suitable revising formula was put forward for hot extrusion force of pipe material. The formula was validated by many simulation experiment, especially effective in the situation that the angle of the model was greater than 80.(3) Some manufacture factors such as extrusion speed, friction coefficient and the temperature of blank were analyzed for the metal deforming effect of shrinking pipe material,Deforming quality formula was set up via analyzing abundance experiment data. Therefore we could forecast the quality of shrinking pipe material and the trial-manufacture could be reduced, the development period could be shorten.(4) The figuration of automobile behind bridge was simulated by two-step deforming technology. The influence of the figuration and the thick of the blank were analyzed from two factors ,the length of blank heat up and the lubrication condition. Practicability of the extrusion force formula of pipe material in chapter4 and the effect of shaping be forecast in chapter 5 were both validated, and the results were favorable.更多还原