[材料绿色成形技术]高强轻质材料绿色智能成形技术与应用

对高强轻质材料绿色智能成形技术的研究成果和现状进行综述,重点介绍了近年来高强轻质材料绿色智能成形技术在冷冲压工艺智能设计、热冲压组织性能智能定制、冲压智能系统与装备三方面的重要研究进展。对高强轻质材料复杂构件绿色智能冲压成形技术在高强钢冷冲压工艺设计系统中的应用,铝合金冷冲压成形后的精度控制,高强钢热冲压的性能定制以及铝合金热冲压性能调控方面进行了探讨和展望,旨在为高强轻质材料绿色智能成形技术的发展提供借鉴。     

双向弯曲连接件冲压工艺的改进

图1所示零件为一双向弯曲连接件,材料为Q235A钢板,厚为1.6mm。冲压成形后要求零件具有良好的强度,表面平整无皱折。按常规的冲压工艺,对于这种双向弯曲件来说,第二次弯曲难以成形,但我们经过研究并结合我厂实际情况,对原设计工艺进行了改进,最终生产出了合格的工件。     

高强钢板在汽车上的应用及冲压成形性能研究现状

随着强度的提高,高强度钢板塑性变差、成形难度增加。对典型高强度钢板,如DP钢、TRIP钢和BH钢等在汽车上的应用情况进行介绍,并对高强度钢板冲压生产时成形性差、回弹严重,以及冲模受力恶劣等常见问题进行了分析,最后对高强度钢板冲压成形性能研究现状和回弹影响因素进行了总结。结果表明,高强度钢板成形性随材料、模具和工艺参数变化而波动,所以须综合研究三者的影响规律,从而提高高强度钢板的成形性能。     

22MnB5超高强钢热冲压成形工艺及试验

考虑材料的热物理性能参数、力学性能与温度的关系,利用ABAQUS软件建立了22MnB5超高强钢热冲压过程的热力耦合有限元模型,选用合适的热冲压工艺参数进行数值分析,得到了坯料热冲压成形的应力应变分布,并以板料初始温度为变量,研究不同初始温度对零件厚度分布、回弹及冷却速率的影响。进行了板料初始温度为900℃的22MnB5超高强钢热冲压试验,零件厚度分布及回弹量与模拟结果基本吻合,各区域淬火组织均为板条状马氏体,由于零件底部的淬火冷却速率较大,马氏体组织更加均匀细小。     

热冲压成形钢的研究进展

对普通热冲压成形钢,高淬透性、高抗氧化性热冲压成形钢,高强韧性热冲压成形钢,超高强度热冲压成形钢,高抗氢脆敏感性热冲压成形钢,纳米粒子强化超高强度热冲压成形钢等热冲压成形钢近年来的发展概况进行了综述,分析了热冲压成形钢零件轻量化与功能性的关系,强度与氢脆之间的关系,以及组织细化对其强韧性的影响机理,并对热冲压成形钢今后的发展方向提出了建议。     

冷旋压加工对高压气瓶性能的影响

钢坯冲压气瓶存在内外观质量差、壁厚偏差大、空瓶质量重、横向冲击韧性低等问题。通过对34CrMo4气瓶钢和34CrMo4－H高强度气瓶钢冲压制造的筒形料坯三轮旋压工艺分析及旋压成形试验,试验研究冷旋压对瓶坯内外表面质量和尺寸的影响;并采用调质处理,试验研究冷旋压加工对材料力学性能和金相组织的影响。试验结果表明,冷旋压气瓶的内外表面质量和尺寸精度明显优于冲压气瓶,延伸率提高约0．5％,横向冲击韧性提高10．5 J／cm2以上,带状组织结构有一定改善。     

马鞍形零件冲压工艺与成形模具设计

图1所示图形为某产品上一种零件。材料20钢,料厚2mm。该零件形状怪异,成形部分不仅弯曲成形,而且包含扭曲变形,零件工艺性很差。1．零件结构与工艺分析仔细分析该零件结构,该零件左部分为弯曲,右部分为扭曲引伸,中间连接部分属于扭弯变形。     

22MnB5高强钢/7075铝合金热铆接冷模具淬火无铆钉铆接研究

针对目前车用22MnB5高强钢和7075铝合金板料在连接工艺上存在的问题,提出一种高强钢和铝合金异种材料车身零件的热铆接冷模具淬火（Hot riveting quenching, HRQ）无铆钉铆接工艺,利用22MnB5在高温下良好的成形性及易淬性,实现对22MnB5高强钢与7075铝合金的有效连接。通过建立HRQ无铆钉铆接的成形和淬冷有限元模型,证明了该工艺的可行性,使铆接后接头的高强钢具有全马氏体组织,保证了接头的强度。并从仿真和试验两方面研究高强钢铆接温度对接头尺寸颈厚值T_n、自锁值T_u的影响,发现在600～800 ℃区间内,T_n和T_u均呈现先上升后下降的趋势,T_u受温度影响更显著,两者均在700 ℃时获得最大值,表明700 ℃是高强钢板料的最佳铆接初始温度。     

弯曲形压板零件弯曲工艺设计

压板零件一侧弯曲,属于弯曲成形零件,弯曲半径较小。根据该零件的特点进行工艺分析处理,可采用落料冲孔和弯曲两道工序冲压成形,本文只考虑设计弯曲工艺。     

热冲压成形技术与数值模拟研究

随着我国经济的不断发展,对钢材的热冲压性能要求越来越高。现代冲压技术是将一种先进的高强度钢板加热到奥氏体温后进行钢板快速冲压,然后对钢板进行快速冷却得到超高强度的新型零件。首先对热冲压成形技术进行了简要概述,然后对热冲压成形技术的工艺原理进行了简要说明,其次简要叙述了影响热冲压成形的主要因素,最后针对某一成型零件进行了试验仿真并且对结果进行了分析,为实际的热冲压成形技术应用提供了参考。     

Experimental analysis of coating layer behavior of Al–Si-coated boron steel in a hot bending process for IT applications

The utilization of high-strength steel for automotive structural parts has increased since the oil crisis in the 1970s owing to its high strength and potential for weight reduction. Because of the limited formability of high-strength steels, automotive components are increasingly produced through hot press forming. In some instances, high-strength steel sheets are coated with an Al–Si layer in order to prevent scaling of components during hot press forming, and this can increase their reliability with a view to the dimensional accuracy and stress distribution when they are in service. In this contribution, the coating degradation mechanisms of Al–Si-coated boron steel after the hot bending process are reported. The issues related to coating degradation during hot press forming are critically reviewed at different positions on a part that was subject to hot bending. In addition, the hardness and friction coefficient were tested by a nano-indenter at various positions. The relationship between the experimental parameters and coating layer properties is also reported. It is concluded that the bending deformation affected the coating layer behavior the most.     

Energy absorption mechanism of Al–steel bilayer sheets produced by cold roll welding during wedge tearing

The behavior of Al–steel bilayer sheets produced by cold roll welding is investigated through the wedge tearing process. It is observed that through tearing the energy absorbed by cold roll welded bilayer sheets is larger than that of non-welded ones, even though all parameters are identical. Also bilayer sheets with low bond strength have the same energy absorbed by non-welded bilayer sheets. By investigating all contributing mechanisms in tearing and mechanical properties of composite layers and developing theoretical equations, it is concluded that bending of sheets through wedge tearing plays a major role in difference of energy absorbed by welded and non-welded bilayer sheets. Moreover, there is a good correlation between experimental data and theoretical equations developed for predicting the load–displacement curves of tearing and energy absorption of Al–steel bilayer sheets.     

Impact damage and hygrothermal effects on fatigue bending strength of orthotropy composite laminates

This paper focuses on fracture mechanisms experimentally based on the scanning acoustic microscope (SAM) when subjected to impact damages, i. e., foreign object damages (FOD), and also on the influence of impact damages and hygrothermals on residual fatigue bending strength of CFRP laminates. Composite laminates used in the experiments are CF/Epoxy orthotropy laminated plates, [0₄/90₄]_s. A steel ball launched by an air gun impacts on CFRP laminates to generate impact damages. Bending fatigue tests are periodically interrupted for a nondestructive evaluation (NDE) measurement of the progressive damages to build the fracture mechanism based on impact damages, and three-point fatigue bending tests are carried out to investigate the influence of hygrothermals on the effect of the residual bending fatigue strength of CFRP laminates.     

Evaluation of material properties and internal damage within CFRP and CFRP/Al sandwich panels due to impact loading

In the present paper, damage development within Carbon fiber reinforced plastic (CFRP) laminates and CFRP/Aluminum (Al) honeycomb core sandwich panels by impact loading was evaluated, and change in material properties due to the damage development was investigated. Falling weight impact tests, 3-point bending tests and cross-sectional observation were carried out. As results, it is found that falling rate of bending elastic modulus due to internal damage in the laminate only is lower than that in the upper face-sheet of the sandwich panel, and that difference in the falling rate between them becomes maximum at the impact energy of 5.1 J. As a result of investigating the relationship between reduction in bending elastic modulus and internal damage development, the reduction is caused by delamination within CFRP laminates mainly. Since total length of cracks in CFRP/Al honeycomb core sandwich panels is smaller than that in the laminates only, the sandwich panels have high impact tolerance because of absorption of impact energy by damaging Al honeycomb core.     

Identification of material hardening parameters by three-point bending of metal sheets

Calibration of hardening and partly viscoplastic parameters of the previously published material model was the primary concern of this paper. The method used for identification of the material hardening parameters for metals, the three-point cyclic bending of sheets, constitutes a basis for this work. Plastic hardening parameters were determined by comparing load–displacement curves from FE simulations with those from the tests. Since viscoplasticity is assumed, stress–strain curves from uniaxial tension tests at selected strain rates for strain-rate sensitive materials were employed to calibrate corresponding viscoplastic parameters. The optimization problems are solved by means of a commercial optimization code, LS-OPT, using a response surface methodology. The objective is to minimize (by the least-squares method) the sum of the differences between measured and simulated loads. The material parameters were identified for two high-strength steel alloys (ZSte340 and DP600, strain-rate sensitive materials), and one aluminium alloy (AA5182).     

高强钢变模量随动强化本构模型匹配与解耦标定策略研究

高强钢通过微观组织调控获得高强度,但不同牌号高强钢微观的不均匀变形和微观诱导塑性机理不同,使得高强钢卸载及反向加载行为更加复杂,并且牌号间差异增大,为此给出模型自适应匹配及参数解耦匹配的系统化策略,实现了高强钢回弹精确预测。首先建立幂函数和指数函数混合硬化模型,基于混合模型给出自由弯曲加载的弯矩平衡方程和曲率约束方程,基于变模量模型构建截面弹性弯矩的积分方程,基于加载和卸载解析模型建立逆向识别卸载参数的子优化模型。确定变模量线性随动强化、变模量非线性随动强化模型和含边界面的变模量随动强化模型的匹配策略。基于自由弯曲、单向拉伸和拉压试验数据,确定相应本构的子优化模型参数的优化次序,最终形成本构匹配及其参数解耦标定的系统化策略,并基于Fortran语言开发标定程序库。建立U形弯曲件和弧形弯曲件预测模型,分别对DP980和DH980两种高强钢不同应变水平下的识别结果及回弹预测结果进行对比分析,验证了解耦标定策略不仅提高了不同牌号数据的相关度,而且大幅度提升了同一牌号下的模型精度和稳定性,为基于数据的材料性能统一自辨识方法研究奠定了基础。     

Positional deviation of bending point in asymmetric V-die bending process of HSS sheet: an experimental study

In this study, a series of experiments are performed to characterize the asymmetric V-die bending process for a High-strength steel (HSS) sheet. The main challenge in asymmetric V-die bending is positional deviation of the bending point during bending, given by a magnitude and a direction of deviation of the bending point. The effects of process parameters, such as radii of the punch head and the die shoulder, on the positional deviation of the bending point were experimentally examined to identify those that govern the deviation of the bending point in an asymmetric bending process. This work improves our understanding of deviations of the bending point, and can be used for developing process design guidelines for asymmetric bending of high-strength steel sheets to produce precise, asymmetrically bent parts.     

Influence of electrical discharge machining parameters on cutting parameters of carbon fiber-reinforced plastic

Today the use of high-strength carbon fiber-reinforced plastics (CFRP) composite as a material for many engineering applications is showing an increasing demand in the industry. These composites are replacing the traditional use of steel because they offer many advantages such as very light weight, high strength, and high stiffness associated with good corrosion-resistant properties. Unfortunately, there is little technological knowledge on the electrical discharge machining (EDM) process of high-strength composite materials, especially about the CFRP. In this work, a study has made into the possibility of using EDM process as a means of machining CFRP composite. Various cutting conditions such as peak current, pulse-on time, pulse-off time and open-circuit voltage were selected to perform electrical discharge machining. The effect of electrode rotation was also studied. Optimum cutting conditions and machine settings for EDM were chosen for machining CFRP composites.     

聚氨酯泡沫填充的碳纤维增强复合材料锥管吸能性能数值模拟及试验验证

提出了一种新型的碳纤维增强复合材料（CFRP）填充聚氨酯（PU）泡沫的汽车前部吸能结构，通过材料性能试验获得了PU泡沫、CFRP复合材料的力学性能参数及PU泡沫填充的CFRP锥管的准静态压缩吸能结果。应用LS-DYNA进行复合材料准静态压溃仿真分析，仿真结果与试验结果吻合较好，验证了复合材料填充结构有限元模型和材料模型的正确性，并且发现泡沫填充的CFRP锥管具有良好的吸能性能，填充结构比吸能高于两种材料单独使用时的比吸能之和。