Simulation of springback variation in forming of advanced high strength steels

Variations in the mechanical and dimensional properties of the incoming material, lubrication and other forming process parameters are the main causes of springback variation. Variation of springback prevents the applicability of the springback prediction and compensation techniques. Hence, it leads to amplified variations and problems during assembly of the stamped components, in turn, resulting in quality issues. To predict the variation of springback and to improve the robustness of the forming process, variation simulation analysis could be adopted in the early design stage. Design of experiment (DOE) and finite element analysis (FEA) approach was used for the variation simulation and analysis of the springback for advanced high strength steel (AHSS) parts. To avoid the issues caused by the deterministic FEA simulation, random number generation was used to introduce uncertainties in DOE. This approach was, then, applied to investigate the effects of variations in material, blank holder force and friction on the springback variation for an open-channel shaped part made of dual phase (DP) steel. This approach provides a rapid and accurate understanding of the influence of the random process variations on the springback variation of the formed part using FEA techniques eliminating the need for lengthy and costly physical experiments.     

基于CAE的DP600高强钢零件回弹特征分析及控制

回弹是高强钢板冲压成形中影响冲压件尺寸精度和形状精度的关键因素。针对采用DP600高强钢的北京奔驰某车型的横梁减震器后桥零件,开展了零件成形、切边、回弹的全工艺流程CAE仿真分析,获得了零件的回弹特征;针对宝钢材料的性能范围获得了回弹的波动范围,并通过模具补偿的方案进行回弹控制,试验测量结果表明其形状精度得到了明显改善。     

基于Dynaform纵梁后板成形工艺及回弹控制模拟分析

阐述了应用Dynaform软件完成高强度钢板DP780标致轿车纵梁后加强板的冲压工艺设计过程和成形回弹分析、控制回弹方法及效果.通过数字模拟技术Dynaform对纵梁后加强板模型回弹前后的数据分析,按零件材料性能和几何形状,采用回弹限制方法即在适当地方设置加强筋和凹槽,使零件回弹较大区域降低约45%,从而达到纵梁后板的...     

某铝合金汽车发动机罩外板冲压成形工艺

针对铝合金材料弹性模量小、在室温条件下的冲压成形性能较差的问题,以铝合金汽车发动机罩外板为例,基于Autoform软件平台分析其冲压成形过程,通过优化型面结构改进零件的成形质量,研究了冲压工艺参数对零件减薄率和回弹的影响规律。结果表明:当采用小的压边力时,板料的减薄较小;在一定范围内,随着压边力的增大,零件的回弹有所减小。最终通过对模具进行型面补偿并结合适当的工艺参数调整,有效地减小了零件回弹。基于结果进行了发动机罩外板的冲压试验,通过模具调试使制件达到生产要求。     

基于数值模拟的板料冲压成形回弹补偿方法

板料冲压中的回弹误差可以通过修正模具形状得到解决。基于冲压及回弹数值模拟,以控制系统、傅立叶变换及传递函数为理论基础,提出了一种模具回弹补偿的修正算法并开发了springbackcom系统。该方法通过两组小量变化的模具及其数值模拟得到回弹前后冲压件,建立模具形状传递函数,修正模具形状。利用此方法对某车引擎盖冲压过程进行了数值模拟及回弹补偿的实例验证,分析结果证明此回弹补偿方法是有效的,具有工程实用价值。     

高强度双相钢DP800成形件碰撞性能仿真分析

针对双相钢板DP800,在完成U型梁冲压成形及回弹仿真分析的基础上,建立了闭口帽型梁的碰撞分析模型。采用映射的方法完成冲压成形件U型梁的厚度、应力、应变向碰撞结构件的结果传递。在考虑成形、回弹及应变率等多种因素的影响下,对帽型梁的碰撞过程进行了多工况仿真分析。研究结果表明,成形后的材料厚度变化、残余应力、加工硬化以及应变率,对碰撞过程将产生直接的影响。研究结果为提高汽车碰撞仿真分析的精度提供了参考。     

高强度钢后保险杠成形工艺优化及回弹控制

采用高强度钢板制造的保险杠能大大提高乘员安全性,但高强度钢板成形困难。采用有限元分析软件Dynaform对某轿车高强度钢后保险杠成形过程进行模拟仿真,并使用结果优化成形工艺。主要研究了工艺补充面对零件冲压成形以及回弹的影响。通过模拟结果和实际样件对比,对工艺补充部分进行了调整,并设置凸顶得到了优化的工艺型面及坯料尺寸,为同类相关高强度钢零件的生产起到了指导作用。     

片状弧形结构件成形回弹控制

针对片状弧形结构件在成形中容易出现回弹的问题,分析了制件成形时回弹产生的原因,采用增设加强筋、改善冲压工艺和模具结构等措施,使制件成形时回弹得到了很好的控制。     

1-Shot hot stamping of ultra-high strength steel parts consisting of resistance heating,forming, shearing and die quenching

A 1-shot hot stamping process consisting of resistance heating, forming, shearing and die quenching was developed to produce small- and medium-size ultra-high strength steel parts. A rectangular sheet was resistance-heated to obtain a uniform distribution of temperature, and just after the end of heating, a sequence of forming, shearing and die quenching was performed by one shot to prevent the drop in temperature. An ultra-high strength steel spur gear having a hardness of 540 HV2 was produced by 1-shot hot stamping composed of heating, blanking and die quenching. The rollover was improved by partial compression of the blanked gear. An ultra-high strength stainless steel part having a hardness of 580 HV2 was produced by 1-shot hot stamping consisting of the heating, bending, shearing and die quenching, and no springback and quenching distortion of the produced part were observed by holding at the bottom dead centre of the press. An operation for thickening the edge of the punched hole was included in 1-shot hot stamping to improve the strength of a product.     

基于Yoshida-Uemori硬化模型的高强钢冲压件回弹预测研究

基于LS-DYNA软件对高强钢薄板零件的冲压成形进行仿真分析与回弹预测,研究了不同材料硬化模型对回弹预测精度的影响。在仿真分析中应用各向同性硬化模型和考虑包申格效应的Yoshida-Uemori随动硬化模型,将模拟回弹值同试验回弹量进行比较,验证了Yoshida-Uemori材料模型在高强钢回弹预测中的可靠性,为实际生产中模具设计及修正提供理论指导。     

帝豪EC718顶盖冲压工艺分析

通过对帝豪EC718顶盖冲压工艺分析,采用回弹补偿、过拉深和增大拔模角等方法,解决了顶盖内凹陷、回弹、刚性不足和装配不良等缺陷,保证了顶盖的外观质量和尺寸精度,节省了大量模具调试、焊装调试和总装调试时间,提高了生产效率。     

Valuation method for effects of hot stamping process parameters on product properties using hot forming simulator

Hot stamping is one of the hot forming processes for manufacturing products of lightweight construction such as lightweight vehicles. Knowledge on the characteristics of the hot stamping process is significant in designing and optimizing the process conditions, dies and tools; however, until now, the characteristics of this process, such as the relationships between a product property and die temperature and between a product property and cooling rate, and the springback amount, have not been clarified consistently or precisely. A new valuation method used to measure the effects of hot stamping conditions on product properties as a function of process parameters is proposed in this paper. This method utilizes a hot forming simulator, which is a precision press with feedback temperature control and controlled cooling, and permits to know the various characteristics of the hot stamping process. Here, the basic construction of the proposed method is presented, and its application to the characterization of the hot stamping process of high-strength steel sheets, such as an evaluation of the changes in product properties upon varying the forming conditions and process parameters, is shown and discussed.     

基于凸模凹模圆角半径的改变解决支撑件回弹

以HSLA420高强钢U形结构支撑件为研究对象,在使凸、凹模的间隙、摩擦因数、压边力等因素对其回弹影响最小的基础上,用Dynaform软件对成形及回弹过程进行模拟,研究凸、凹模圆角半径变化时支撑件回弹值的变化。采用单一变量法,分别以不同大小的凸、凹模圆角半径为自变量,相应支撑件两臂之间的回弹值为因变量,作出凸、凹模圆角半径-回弹值的曲线,分析凸、凹模半径变化时回弹值的变化规律,并选择合适的凸、凹模圆角半径使支撑件的回弹值接近零,能够不用整形或仅需一次整形将支撑件的圆角部分调整到符合工艺要求的尺寸,避免多次整形造成圆角处材料过度变薄,造成冲压件出现裂纹等缺陷。     

FE Simulation Models for Hot Stamping an Automobile Component with Tailor-Welded High-Strength Steels

Ultra-high-strength in sheet metal parts can be achieved with hot stamping process. To improve the crash performance and save vehicle weight, it is necessary to produce components with tailored properties. The use of tailor-welded high-strength steel is a relatively new hot stamping process for saving weight and obtaining desired local stiffness and crash performance. The simulation of hot stamping boron steel, especially tailor-welded blanks (TWBs) stamping, is more complex and challenging. Information about thermal/mechanical properties of tools and sheet materials, heat transfer, and friction between the deforming material and the tools is required in detail. In this study, the boron-manganese steel B1500HS and high-strength low-alloy steel B340LA are tailor welded and hot stamped. In order to precisely simulate the hot stamping process, modeling and simulation of hot stamping tailor-welded high-strength steels, including phase transformation modeling, thermal modeling, and thermal-mechanical modeling, is investigated. Meanwhile, the welding zone of tailor-welded blanks should be sufficiently accurate to describe thermal, mechanical, and metallurgical parameters. FE simulation model using TWBs with the thickness combination of 1.6 mm boron steel and 1.2 mm low-alloy steel is established. In order to evaluate the mechanical properties of the hot stamped automotive component (mini b-pillar), hardness and microstructure at each region are investigated. The comparisons between simulated results and experimental observations show the reliability of thermo-mechanical and metallurgical modeling strategies of TWBs hot stamping process.     

板料多步冲压回弹的数值模拟研究

回弹是板料冲压成形过程中一种常见但很难解决的现象。首先研究了板料弯曲变形中卸载回弹的原理,然后以依维柯侧壁上内板为例,采用动态和静态算法相结合的方法,在考虑每道工序板料回弹的基础上,对其进行多步冲压回弹的数值模拟,最后对模拟结果和实验结果进行比较,验证该模拟方法提高回弹计算精度的有效性,为板料冲压成形工艺的制定提供科学依据。     

硼钢板与模具间接触热阻实验研究及其在回弹仿真中的应用

接触热阻是影响热冲压过程中热能传导的一个重要因素,而零件不同区域的温差则直接影响热冲压的回弹,因此,获得准确的接触热阻数值对提高热冲压回弹仿真的精度具有重要意义。基于稳态法设计了22MnB5板件与Cr7V模具钢接触热阻的测量实验,推导出接触热阻的计算公式;并按照实验方法搭建了实验平台,获得了不同压强下两者的接触热阻值;最后拟合了接触热阻与压强的关系方程。将关系方程带入某B柱的热冲压回弹仿真中,与原始仿真对比发现,改进后的仿真结果与实际实验值较为接近,证明获得准确的接触热阻与压强的关系方程可提高硼钢板热冲压回弹的仿真精度。     

车窗升降板弯曲成形回弹缺陷的影响因素分析与成形工艺优化

针对弯曲件汽车车窗升降板在成形过程中因板料弹性回复和残余应力的存在易产生回弹而影响零件尺寸和装配性能的问题,借用Dynaform平台对板料弯曲成形过程进行数值模拟及回弹预测。针对板料厚度A、冲压速度B、摩擦因数C和模具间隙D等4项影响因素设计9组不同的成形工艺参数组合,分别对板料进行正交试验和重复正交试验(重复次数S=3)获取回弹结果,并采用极差分析法(方案1)和方差分析法(方案2)进行影响因素的主次排序和工艺优化。方案1和方案2分别获得的影响因素主次顺序和优化工艺参数组合为ABDC,A_2B_2D_3C_2和BDCA,B_2D_3C_2A_1。将两组工艺参数进行对比验证,进而确定最佳参数组合为板料厚度A=0.9 mm,冲压速度B=5000 mm·s~(-1),摩擦因数C=0.125,模具间隙D=1.15。利用该工艺进行试生产,检测零件危险圆角处厚度为t=0.70 mm,减薄率低于25%。经过试装配证明,采用优化后工艺参数成形的零件能够满足其使用条件下的尺寸和装配要求。     

高强钢精密冲压件回弹量预测及控制研究

运用Dynaform软件建立高强钢板DP590的U形件有限元模型,进行了恒定压变力、恒定冲压速度条件下的回弹预测,并通过相同条件下的实验验证了回弹预测的准确性。为实现高强钢精密冲压件回弹的智能控制,进行了变冲压速度和变压边力条件下的U形件的拉深试验。其试验结果表明,采用变压力技术比变冲压速度技术更能有效地控制高强钢精密冲压件的回弹。     

高强钢板冲压全工序回弹补偿研究

回弹是高强钢板零件冲压中的一大难题,当前工程应用中回弹计算精度不高,仍然依赖大量修模解决回弹问题。采用全工序仿真计算和回弹补偿方法,提高回弹计算的数值模拟精度,并利用位移回弹补偿原理对拉深型面和修边型面进行回弹补偿,使冲压回弹后零件尺寸满足设计产品的精度要求。结果表明,该研究方法大大提高了高强钢冲压件的质量,实际生产应用效果良好。     

先进短流程—深加工新技术与高强塑性汽车构件的开发

在近年来国内外薄板坯连铸连轧TSCR和先进热成形处理AHFT技术发展的基础上,提出了先进的短流程与深加工技术相结合的工艺途径,为高强塑性汽车构件的生产制造开发了一种高效率、低能耗、低排放、低成本的新工艺。首先采用先进短流程工艺,包括以CSP、FTSR、ISP半无头轧制为主要特征的第2代TSCR技术和以ESP无头轧制技术为主要特征的第3代TSCR技术,生产高强度薄规格汽车板作为热冲压成形的原料; 然后采用先进热成形处理AHFT技术,对短流程薄规格热轧酸洗板进行热冲压与热处理相结合的深加工,制作高强塑性汽车构件。本文简要介绍了短流程薄板坯连铸连轧TSCR技术的发展,先进热成形处理AHFT技术的强塑化工艺与主要技术特征。讨论了采用短流程TSCR新工艺生产先进高强度钢AHSS薄规格汽车板,为先进热成形处理AHFT提供热冲压成形板料的主要技术关键。介绍了在超短流程的双辊薄带连铸工艺线上开发高强塑性TWIP钢的试验进展。短流程TSCR新工艺与先进热成形处理AHFT深加工新技术相结合,开发与生产超高强塑性汽车构件,需要钢铁与汽车行业的密切合作。这项短流程—深加工新技术不仅可以满足新一代汽车对轻量化节能减排和抗冲撞安全的要求,而且可以显著降低汽车板构件生产制造过程中的能耗与温室气体排放。