先进高强钢DP1000地板中央通道的成形回弹及补偿研究

高强度钢板因具有较高的强度而易产生严重的回弹缺陷,已成为其应用的最主要瓶颈.为此,本文以某车型地板中央通道零件为载体,针对其几何型面复杂、材料变形程度大的特点,研究先进高强度钢板DP1000的冲压成形回弹及补偿特性.通过对该零件的冲压成形工艺方案进行优化设计和全工序回弹数值模拟,并结合零件的几何特征和变形模式,对各成形工序的回弹进行精确预测.基于预测结果对模具型面采用折入处理的方式进行全工序几何补偿,实现回弹补偿的自工序完结.最后以补偿后的型面进行冲压实验,并对零件的型面尺寸进行检测分析.结果表明,全工序回弹数值模拟和型面几何补偿是解决复杂零件多工序冲压成形回弹问题的最有效方法.通过两次回弹补偿后,该零件的回弹得到完全控制,尺寸精度达到要求且成形质量良好.     

汽车中央通道冲压回弹及其补偿研究

为了研究回弹量及回弹补偿对冲压件成形的影响,以某车型中央通道为研究对象,针对其型面复杂、模型边界高、成形曲度大的特点,采用有限元分析软件Dynaform5.7.1对其进行成形分析、回弹模拟分析和回弹补偿模拟分析.利用截面法对成形及回弹后的零件进行分析,获得边缘回弹量和角度回弹量;经两次反向修模补偿,得到优化的模具型面;利用优化后的模具型面进行模具设计,并对中央通道进行实际生产验证,结果表明,采用截面法和模具型面补偿法能够使最终生产出的零件的回弹量减小,且成形效果更好.     

高强钢板冲压成形的回弹规律与工艺参数研究

高强钢板冲压成形的回弹问题在很大程度上制约了其深入应用,合理的工艺是减少回弹的关键和有效途径之一.建立了曲面扁壳件冲压成形的有限元模型,基于正交试验法研究了工艺参数,包括压边力、摩擦系数、板厚以及拉深筋的布置方式对回弹的影响规律,采用普通钢板和高强钢板分别进行了冲压成形实验,并与数值模拟结果进行对比.结果表明,高强钢板冲压成形的回弹较大,但通过合理的压边力和拉深筋布置方式可以实现高强钢板冲压成形回弹的有效控制.     

先进高强度钢板弯曲类回弹特性的试验研究

随着先进高强钢板在汽车及航天航空领域的广泛应用,回弹导致的成形精度问题日益突出.为了获取先进高强钢的弯曲回弹特性,通过采用U形件回弹模型,针对600MPa级别的3种典型高强钢(DP钢、TRIP钢、HSLA钢)进行了回弹试验研究.实验结果表明:在相同变形条件下,TRIP钢弯曲回弹最大,DP钢次之,HSLA的弯曲回弹最小;不同工艺条件、不同材料性能参数对弯曲回弹呈单调的影响规律,而润滑条件对弯曲回弹的影响趋势并未出现一致性规律.     

航空发动机燃烧室帽罩变压边热成形技术

目的 提出帽罩零件真空环境变压边热成形新技术,解决航空发动机燃烧室帽罩零件冷成形回弹大、精度低、内部应力大,以及热成形壁厚不均、氧化严重等问题。方法 利用有限元仿真和工艺试验相结合的方法,选用GH3625高温合金板材研究变压边热成形过程中压边力加载路径对帽罩成形质量的影响,分析热成形模具热膨胀与回弹变形对帽罩尺寸精度的影响,建立考虑热成形、变压边力加载及模具补偿的成形方案。结果 在900 ℃条件下,帽罩热成形力相比室温下降低约70%,内外径回弹量分别降低约67%和59%。基于几何特征优化的压边力加载路径有助于减小零件型面的回弹。结合回弹变形和热膨胀变形补偿,确定模具总补偿量为内径?0.49 mm,外径?0.62 mm。工艺试验结果表明,采用模拟所确立的成形方案成形的帽罩质量较好,尺寸精度达到IT9级,型面精度在0.2 mm以内,切边后回弹量为0.1 mm,与有限元仿真结果吻合较好。结论 建立的有限元模型和变形补偿方案可以有效地优化帽罩的工艺成形过程,所提出的变压边热成形技术能够显著降低高温合金变形抗力和回弹,可以解决高精度帽罩零件成形制造难题。     

汽车纵梁成形回弹及补偿

目的分析某型汽车纵梁的结构特点和冲压工艺性,并根据实际生产经验、条件制定多步成形工艺方案。方法借助AutoForm有限元软件对零件进行冲压成形模拟,有效防止成形缺陷的形成,降低模具形成的风险。对于高强度钢纵梁在成形后具有较大回弹的情况,使用迭代回弹补偿方法来补偿模具的回弹。在此基础上,根据回弹补偿后的模具型面设计并加工模具。结果经过多次回弹补偿,零件的最大回弹由补偿前的13mm减小至±0.5 mm以内,回弹补偿效果较为显著。结论此回弹补偿方法具有可行性并具有指导工程应用的价值。     

模具对柱面复合材料构件固化变形影响的有限元分析

针对复合材料构件固化变形问题, 分析了复合材料热压罐成型固化过程的多场耦合关系, 考虑模具的作用, 建立了柱面复合材料构件固化过程的有限元分析模型。基于此模型, 研究了模具材料、 模具厚度和模具形式对柱面复合材料构件固化变形的影响。结果表明: 模具对柱面件固化变形的影响较大, 模具材料与构件材料热膨胀系数(CTE)不匹配程度影响构件回弹角的大小; 模具的厚度不同, 导致构件的不同回弹角; 采用阴模时, 构件回弹角小于阳模的, 且回弹方向相反。     

车身用高强钢的回弹实验与分析

目的研究和分析身用高强钢在冲压过程中的回弹行为与规律。方法基于Wagoner的拉延弯曲实验模型,采用拉延弯曲(Draw-Bend)实验机,针对590 MPa级冷轧双相钢和420 MPa级低合金高强钢两个常用的典型车身用高强钢材料开展回弹实验研究,通过不同弯曲半径模拟不同冲压模具圆角半径,同时以不同张紧力模拟冲压压边力,讨论了两种材料的冲压成形及回弹性能与控制。结果两类钢的回弹量均随着冲压模具圆角半径的增大而减小,随着压边力的增大而减小,双相钢相比低合金能产生更大的回弹,厚板随冲压条件变化的回弹波动一般低于薄板。结论实验研究结果对高强钢在实际冲压过程中的回弹控制有着较强的指导意义。     

980 MPa先进高强钢材料在门槛加强梁上的辊压应用

目的为获得980 MPa级别不同先进高强钢材料在辊压零件上应用时的差异,研究典型980 MPa先进高强钢的辊压成形特性。方法采用调研和统计方法获得门槛辊压用材的主流强度与钢种,基于三点弯曲的实验方法,获得了980 MPa先进高强钢材料在指定角度和弯曲半径下的回弹特性,针对典型的门槛加强梁零件,采用CAE方法评估材料应用的可行性。结果门槛零件980 MPa级别所采用的主要先进刚强钢钢种为双相钢(DP)和马氏体钢(MS),在相对弯曲半径比R/t=2.5的情况下,980DP回弹角度最小,980QP次之,980MS最大;早期模具回弹补偿设计时对于90°圆角可给予11°~14°的回弹过弯角度;成形过程中有可能出现边波缺陷,需优化辊压成形变形过程。结论 980 MPa先进高强钢材料在应用于辊压零件时,应在设计阶段充分考虑材料回弹特性,同时变形过程应合理,避免产生边波等质量缺陷。     

纵梁前段全工序回弹预测与控制

目的结合高强度钢板纵梁前段工艺难点及特征,提出对该零件回弹进行预测和控制的方法。方法采用经验设计和CAE分析技术相结合的方法,对零件全工序成形及回弹过程进行了仿真模拟分析,同时对零件产生回弹的原因进行了深入分析,提出了回弹问题的解决方案。结果通过采取有效措施对回弹进行控制,成功解决了零件质量问题,回弹控制在了1 mm之内,平均合格率达到了91.8%,满足了装车要求。结论全工序CAE分析可有效预测高强度钢板梁类零件的成形质量缺陷和回弹状态,并指导工艺设计和模具型面补偿,合理的梁类扭曲回弹解决方案为类似零件模具的开发提供了参考。     

基于Autoform的汽车侧围回弹补偿分析

目的 针对汽车尤其乘用车侧围大量复杂表面经常出现的表面凹陷、大尺寸回弹等质量问题,对回弹过程进行分析研究并加以控制.方法 基于数值模拟的方法,采用Autoform软件对汽车侧围表面冲压回弹进行数值模拟预测,将数值计算结果与实际生产经验相结合,对侧围几何模型进行补偿和控制.结果 生产的后侧围零件尺寸合格率达到90％以上.结论 采用数值模拟对汽车侧围回弹补偿分析,能减少成形过程中的缺陷,提高尺寸精度,有效解决侧围回弹大的问题.     

汽车侧围前连接板冲压成形质量优化研究

针对汽车侧围前连接板的成形质量缺陷问题,本文通过有限元软件分析工艺参数对成形质量的影响,并完成拉延模面的回弹补偿。首先,以最大减薄率和最大回弹量为评价目标,采用正交实验对压边力、模具间隙、冲压速度和摩擦系数4个工艺参数进行分析,获得影响成形质量最大的因素为压边力,冲压速度次之,确定最优工艺参数为:压边力300 kN、模具间隙1.20 mm、冲压速度90 mm/s、摩擦系数0.11;其次,采用节点位移法对拉延模面进行2次回弹补偿,将零件的回弹量控制在允许范围内;最后,将最优工艺参数和回弹补偿面应用于现场实验,测得试模件的最大减薄率为14.64%,最大正负回弹量为1.254 4 mm/-1.327 0 mm,试模件的最大减薄率和最大回弹量均在允许范围内,实验结果与仿真分析结果相近,验证了本实验方案的可行性。研究表明:通过优化工艺参数能够有效控制减薄、起皱和拉延不足等缺陷,并能够在一定程度上减少回弹量;通过对拉延模进行回弹补偿可以有效地控制回弹量。     

Multi-regression modeling for springback effect on automotive body in white stamped parts

The use of high strength steel (HSS) materials in automotive body in white (BIW) stamped parts has increased the occurrence of springback after the forming process. Although HSS exhibits superior strength, weight reduction, and crash energy, it strongly influences springback impact on the sustainable development of BIW stamped parts. In this study, an empirical springback prediction model was synthesized based on the contemporary data sets of springback-prone components of automotive BIW stamped parts. Two different BIW stamped parts from an actual industrial stamping production line were selected as pilot parts for this study. A statistical multi-regression (MR) analysis was used to model the springback prediction effect by examining the sensitivity of springback input parameters on existing die geometry. The outputs represent the total springback values of the stamped parts. A total of 240 data from samples of selected stamped parts were tabulated to synthesize the springback prediction model. The results show that the MR models for the two parts were linear with the springback estimated errors between the measured and predicted values between 0.5° and 3°, which is acceptable from an industrial viewpoint. The proposed MR models are capable of predicting the springback effect with minimal error by incorporating all possible variations that are inherent in the shop floor process.     

Analysis of stamping performances of dual phase steels: A multi-objective approach to reduce springback and thinning failure

The industrial interest on light weight components has contributed in the last years to a significant research effort on new materials able to guarantee high mechanical properties, good formability and reasonable costs together with reduced weights when compared to traditional mild steels. Among such materials advanced high strength steels (AHSS) such as transformations induced plasticity (TRIP) and dual phase (DP), and light weight alloys proved their usefulness in stamping of automotive components. As AHSS are concerned, one of the main drawbacks is related to springback occurrence. Many aspects have to be taken into account when springback reduction is investigated: material behavior issues, process conditions, numerical simulations parameters calibration, geometrical aspects and so on. Moreover, springback minimization problems are typically multi-objective ones because springback reduction may conflict with other goals in stamping design such as thinning reduction. In this paper, such problem was investigated through integration between numerical simulations, Response Surface Methodology and Pareto optimal solutions search techniques. The design of a U-channel stamping operation was investigated utilizing two different dual phase steel grades: DP 1000 and DP 600. An explicit/forming-implicit/springback approach was utilized for the numerical simulations. Friction conditions and blank holder force were optimized as design variables in order to accomplish two different objectives: reduce excessive thinning and avoid excessive geometrical distortions due to springback occurrence.     

Semi-hot Stamping as an Improved Process of Hot Stamping

Reducing the forming load,deletion of springback,increasing the formability of sheets as well as producing high strength parts are the main reasons to apply hot stamping process.Hot stamping process and 22MnB5 steels are the state of the art process and grades,respectively;however novel processes and steel grades are under considerations.In the current research,behavior of the steel grade MSW1200 blanks under semi and fully hot stamping processes was characterized.During semi-hot stamping process,the blank was firstly heated to a temperature of about 650℃ and then formed and quenched in the die assembly,simultaneously.Microstructure and mechanical properties of semi and fully hot stamped blanks were studied and the results were compared with those of normally water/air quenched blanks.The hot stamped blanks attained the strength values as high as water quenched blanks.The highest ductility and consequently,the best formability were achieved for the blank which had been semi-hot stamped.It was concluded that for the mentioned steel,semi-hot stamping process could be considered as an improved thermo-mechanical process which not only guaranteed a high formability,but also led to ultra high strength values.