【作者】 张彦燊；

【导师】 刘晓晶；

【作者基本信息】 哈尔滨理工大学 ， 材料加工工程， 2011， 硕士

【摘要】 梁形件是汽车结构件的主要组成部分,在车身覆盖件中也占有很大比例。汽车梁形件的冲压成形在塑性成形的同时必然伴有弹性变形,外力卸载后弹性变形部分的回复即造成回弹,成形后经过修边的零件因形状改变使内应力重新分布也会引起回弹。回弹在成形过程中不可避免,回弹导致的尺寸变化会产生严重的装配问题,影响整车的结构稳定性和安全性。材料的屈服强度越大回弹量也越大,随着汽车轻量化进程的发展,由高强度钢板代替传统钢板带来的梁形件回弹缺陷增大的问题也越来越凸显。为实现对回弹准确预测和有效控制的目的,采用了理论分析、数值模拟和实验相结合的方法,对先进高强度钢板梁形件的回弹规律和控制方法进行研究。分析了数值模拟中单元类型和尺寸、厚向积分点数目、约束条件、计算公式、时间步长和虚拟拉延速度对回弹精度的影响。通过对U形件回弹实验和数值模拟研究得出:回弹量随压边力和拉延筋阻力增大而减小,随板料厚度增加先增大后减小,在一定范围内回弹量随摩擦系数增大而减小。通过对S梁回弹数值模拟,提出在前处理中测量截面线回弹角的方法。对斜壁U形梁采用模具型面补偿,零件回弹后的形状与标准形状吻合,使回弹缺陷消除。以后边梁为例,对具有复杂型面的汽车梁形件进行了数值模拟。提出了按变形区分曲面进行工具网格划分的方法,分析得出针对后边梁的具体计算时间步长和单点约束方式,提出了数值模拟回弹分析的分段法。在控制成形缺陷的基础上对后边梁的卸载回弹和修边回弹的最大位移及出现位置做出了预测,总结出将压边力和拉延筋阻力合理配比的回弹控制方案,经试模验证,采用优化后的成形工艺使后边梁的回弹得到了较好的控制。更多还原

【Abstract】 Beam parts are the main structural components of automobile, also a large proportion of the automobile body panels. The stamping of automobile beam parts necessarily accompanies elastic deformation at the same time of plastic forming. Springback is the recovery of elastic deformation after external force unloading. The trimming parts after forming will also lead to springback, because of stress redistribution caused by shape change. It is inevitable during the forming process, can lead to size change which is a serious assembly problem, affects the stability and safety of automobile structure. The greater the yield strength of material the greater the springback, with the lightweight development process of automobile, the beam parts springback caused by high strength steel instead of traditional steel is more and more obvious.To accurately predict and effectively control springback, using the method of theory analysis and combination of numerical simulation with experiment, research has been done on the springback regularity and control of advanced high strength steel beam parts. Analyze the influence of unit type and size, integral point number in the direction of thickness, constraint condition, formula, time step and virtual drawing speed to springback accuracy in the numerical simulation process. Conclusion of research on the springback experiment and numerical simulation of U-shaped part is that the springback decreases with the increment of blank holder force and draw bead resistance, increases first and then decreases with the increment of sheet thickness, in a certain degree, it decreases with the increment of friction coefficient. Through numerical simulation of S-shaped beam springback, propose the method of measuring the section line angle in pretreatment. Adopt die profile compensation to inclined wall U-shaped beam, shape of the part after springback is similar to the standard shape, so the springback harm is eliminated.Take the behind beam for example, do some numerical simulation on these automobile beam parts which have complex profiles. Propose the method of dividing grids of tools according to the distinguish surfaces of deformation zone. Through analysis, the method of concrete calculating time step and single point constraint according to behind beam is obtained, and put forward the segmentation method of numerical simulation on springback. Predict the maximum displacement and position of unloading springback and trimming springback of the behind beam on the basis of controlling forming defects. Summarize the springback control scheme of matching blank holder force and draw bead resistance. Verified by test drawing, springback of the behind beam is decreased effectively with the optimized scheme.更多还原