【作者】 于旭；

【导师】 赵坤民；

【作者基本信息】 大连理工大学 ， 车辆工程（专业学位）， 2018， 硕士

【摘要】 车身覆盖件冲压成形是应用十分广泛的一种塑性成形技术,而在此基础上的有限元数值仿真也到了广泛的应用。但是随着汽车覆盖件板材逐渐采用厚度更薄的高强度钢板以及铝板,并且车身覆盖件的外形逐渐复杂的趋势之下,表面凹陷的产生逐渐增多,有限元仿真技术的局限性也开始出现。本文在之前试验研究的基础之上,进一步探究板料冲压成形有限元仿真的一些关键技术和理论,以期通过有限元仿真更好的预测覆盖件成形之后表面凹陷产生的位置、大小以及回弹方向,并在此基础之上进行模面回弹补偿,将有限元仿真技术更好的应用于指导实际生产。首先,对之前的表面凹陷特征件试验以及成形零件的测量结果进行简要的分析。对有限元数值模拟中的关键理论以及重要的影响参数,如有限元仿真计算的显隐式算法、材料模型、单元类型、以及板料和工具体初始网格划分技术等进行深入探讨;同时介绍特征件成形结果以及回弹方向和大小的评价标准。通过对特征件试验模具设计结构的分析,基于冲压仿真软件DYNAFORM建立了特征件冲压成形及回弹数值仿真模型以及合适的算法。其次,通过数值模拟,研究板料和工具体初始网格尺寸、单元类型、压边圈控制方式、压边力大小以及厚向积分点个数等工艺参数对特征件成形和回弹结果的影响。研究结果表明:板料和工具体的初始网格尺寸划分对成形以及回弹结果有极大的影响,合适的网格大小可以获得正确的回弹大小及方向。成形仿真结果是回弹计算的基础,成形采用2号BT单元,回弹采用16号全积分单元计算得到的结果最为理想;手动偏置料厚间隙1.1t,采用固定压边力大小的压边圈控制方式与实际试验条件相符合;厚向积分点数目对成形仿真结果的影响不大,回弹仿真应适当增加积分点的数目,但多于9个的积分点数目对于回弹的精度并没有太大的提升。最后,在上述结论的基础之上,探究材料和型面因素对表面凹陷的影响。并且针对性的提出模具内空气对试验结果的影响理论,并对此大致探讨和仿真分析,虽然没有得到可靠的结论,但是对冲压模具排气孔的设计提供了参考。在表面凹陷大小以及方向计算较为精确的前提之下,利用软件的回弹补偿模块对工具体模面进行多次回弹补偿,并用补偿后的模面再次进行成形仿真分析,得到了较为理想的结果。更多还原

【Abstract】 Auto body panels stamping is a widely used plastic forming technology.Finite element numerical simulation technology has also been widely applied on the basis of this.However,with the gradual use of the thinner high strength steel plate and aluminum plate,the surface low of the body cover gradually increase,and the limitations of the finite element simulation technology have begun to appear.On the basis of previous experimental research,this paper further explores some key technologies of finite element simulation in order to predict the size of surface low and the direction of springback through finite element simulation,and to compensate the springback on the model surface on this basis,in order to apply the finite element simulation technology to better application.To guide actual production.First of all,the surface low feature test and test results are briefly introduced.The key technologies in the finite element simulation,such as the finite element solution algorithm,the material model,the element type and the finite element mesh division are discussed,and the evaluation criteria for the shape of the feature parts and the direction and size of the springback are also introduced.Based on the analysis of the characteristic parts and the dies,a numerical simulation model and a springback algorithm for feature stamping are established based on DYNAFORM.Secondly,through numerical simulation,the influence of the initial mesh size of the blank and the tool body,the type of the element,the control mode of the blank holder,the size of the blank holder force and the number of the thick integral point on the result of the forming and springback of the feature parts is studied,and the accuracy of the springback direction is observed.The results indicate that the initial mesh size of the blank and the tool has a great influence on the forming and springback results,the proper size of the initial mesh can get the correct size and direction of springback;the forming simulation result is the foundation of the springback,and the result is obtained by the simulation of the 2 BT element and the 16 full integration unit of the springback mining.The most ideal,manual offset thick gap 1.1t,the use of fixed edge force size of the edge ring control method and the actual test conditions are in line with the actual conditions,the thickness of the number of points on the simulation result is not significant,springback simulation should increase the number of integration points,but more than 9 integral points for the precision of the springback is not too big promotion,not recommended.Finally,based on the above conclusions,we explore the influence of material and surface factors on surface defects.At the same time,the theory of the influence of air on the experimental results is put forward,and the general discussion and simulation analysis have not been obtained,but it provides a reference for the design of stamping die.Under the condition that the size and direction of the surface defect are more accurate,the resilience compensation function of the software itself is used to compensate the die face two times,and the die surface after the compensation is simulated again,and the ideal results are obtained.更多还原