【作者】 唐志文；

【导师】 谢晖； 李红运；

【作者基本信息】 湖南大学 ， 车辆工程（专业学位）， 2020， 硕士

【摘要】 随着汽车行业的发展和人们日益对节能环保的重视,当前汽车制造业在保证汽车安全性能的前提下,也尽可能地满足节能环保的要求。汽车轻量化能够有效地节省汽车燃油消耗、减少废气排放,成为当前汽车技术发展的重要趋势。超高强钢的出现以及在汽车车身零件上的应用,能够在有效确保汽车安全性的同时,也有利于实现车身轻量化的目的。然而,由于超高强钢的高强度、低延伸率,使得对其加工成形非常困难,而且极容易出现开裂、起皱等缺陷。超高强钢的性能研究是当前材料技术的研究重点,很多学者在超高强钢的成形性方面进行了许多相关研究。然而,在超高强钢的零件应用方面的研究较少,并同时考虑超高强钢零件本身结构和冲压工艺的研究更是少之又少,不利于超高强钢的广泛应用。因此,本文从超高强钢零件应用的角度出发,面向结构和冲压工艺设计,对汽车超高强钢结构件成形性进行研究,对于指导生产过程中零件的结构设计和冲压工艺设计以及促进超高强钢的广泛应用都具有重要的意义。本文针对汽车超高强钢结构件,基于有限元模拟技术对其进行了冲压模拟分析。首先介绍了与板料成形相关的有限元基本理论,然后针对超高强钢车身零件提出了成形性的评判指标,以简单的U型件为例并结合冲压成形理论,研究了零件高度、上弯曲半径、下弯曲半径和立面倾斜角4个零件本身结构参数对超高强钢结构件成形性的影响。通过分析与总结,为超高强钢汽车车身零件的结构设计和生产制造积累一定的经验。本文还以某超高强钢B柱加强板作为研究对象,对其进行了冲压仿真分析与多目标优化。选择最大减薄率和最大起皱因子作为成形性的评价指标,综合考虑零件结构参数和冲压工艺参数,将上弯曲半径、下弯曲半径、立面倾斜角3个结构参数和压边力和拉延筋系数2个工艺参数作为优化参数,进行了试验设计并构建了Kriging近似模型。基于构建的近似模型并根据多目标优化理论,运用NASG-II算法对影响超高强钢零件成形性的相关参数进行了多目标优化设计,得到了最优的参数组合为R=14mm、r=15mm、θ=17°、F=530k N和μ=0.11。根据优化的参数组合修改零件结构和冲压工艺,并通过试验验证优化后的零件具有良好的成形性,出现开裂、起皱缺陷的风险大大降低。更多还原

【Abstract】 With the development of the automobile industry and people’s increasing emphasis on energy saving and environmental protection,the current automobile manufacturing industry also meets the requirements of energy saving and environmental protection as much as possible while ensuring the safety performance of automobiles.Lightweight of automobiles can effectively save automobile fuel consumption and reduce exhaust emissions,which has become an important trend of current automobile technology development.The emergence of ultra-high strength steel and its application in automobile body parts can effectively ensure the safety of automobiles while also contributing to the goal of the weight reduction of automobile bodies.However,due to the high strength and low elongation of ultra-high strength steel,it is very difficult to process and form,and it is very prone to defects such as cracking and wrinkling.The research on the performance of ultra-high strength steel is the current research focus of material technology.Many scholars have conducted many related researches on the formability of ultra-high strength steel.However,there are few studies on the application of ultra-high strength steel parts,and the research on the structure itself and stamping process of the ultra-high strength steel parts at the same time is even less,which is not conducive to the widespread application of ultra-high strength steel.Therefore,from the perspective of the application of ultra-high strength steel parts,this article studied the formability of automotive ultra-high trength steel structural parts for structure and stamping process design.And it is of great significance for guiding the structural design and stamping process design of parts in the production process and promoting the wide application of ultra-high strength steel.Through analysis and summary,it has accumulated some experience for the structural design and manufacturing of ultra-high strength steel automobile body parts.In this paper,an ultra-high strength steel B-pillar reinforcement plate was taken as the research object,and the stamping simulation analysis and multi-objective optimization were also carried out.The maximum thinning rate and maximum wrinkle factor were selected as the evaluation indicators of formability.Considering the structural parameters of the parts and the stamping process parameters comprehensively,three structural parameters of upper bending radius,lower bending radius,elevation tilt angle and two process parameters of blank holder force and drawbead coefficient are used as optimization parameters.The experimental design was carried out and the Kriging approximate model was constructed.Based on the constructed approximate model and according to the multi-objective optimization theory,the NASG-II algorithm was used to perform multi-objective optimization design on the relevant parameters that affect the formability of ultra-high strength steel parts.The optimal parameters combination obtained is R=14mm,r=15mm,θ=17°,F=530k N and μ=0.11.The part structure and stamping process were modified according to the optimized parameters combination.And it is verified through experiments that the optimized part has good formability.The risk of cracking and wrinkling defects is greatly reduced.更多还原