宽板U形弯曲的回弹试验研究

带状板材在受到冲压后,如果冲压工艺设计不合理,回弹会使板料的冲压结果达不到下一步安装工艺的要求。通过试验的方法,探求在无边压力的情况下板材的回弹问题,分别就板材性能、板料厚度、凸模圆角半径、凸凹模间隙、凹模跨度和摩擦因数等诸多因素对板料回弹的影响进行了分析,得出板材U形弯曲时回弹规律:凸凹模间隙越小,回弹就越小;随着凸凹模跨度的增大,回弹角增大;同一种板材,板材厚度越小,回弹就越大。研究结果有利于工业企业控制金属板材的回弹。     

Springback characteristics of tailor-welded strips in U-draw bending

The purpose of this study is to investigate the springback characteristics of tailor-welded strips in U-draw bending. Two different welded strips were adopted to compare the effects of weld-line locations on the springback. One was welded along the centerline of the strip-width and the other was welded along the centerline of the strip-length. To investigate the effect of different thickness combinations on the springback, the tailorwelded strips were joined by a laser welding process. Three sheet thickness combinations were assessed, SCP1 0.8 t^* SCP1 1.2 t, SCP1 0.8 t^* SCP1 1.6 t and SCP1 0.8 t^* TRIP 1.0 t. Three punch profile radii of 3, 6, and 9 mm and three die profile radii of 5, 10, and 15 mm were prepared and three blank holding forces (BHF) of 125 kg_f, 250 kg_f, and 500 kg_f were applied to investigate the effects of punch profile radius (R_p), die profile radius (R_d), and BHF on the springback of tailor-welded strips. With consideration for the thickness of the sheet and the material properties, the extent of the springback on the sidewall of unloaded sheet shapes increases as the thickness and the yield strength of the sheet increase in the U-draw bending process. For longitudinally welded strips, the amount of springback of the TRIP steel sheet in TWB could be reduced through a springback combination of the thinner side and weld-line. For the thinner side (0.8 t) of the centrally welded strips, the deformed shapes after the springback were almost the same regardless of the thickness com|bination, and the extent of the springback decreased compared with that of non-welded SCP1 0.8 t. Some experimental results are compared with analytical results obtained by using the finite element method.     

基于有限元法的油孔卡环弯曲回弹分析及控制

随着对冲压件尺寸精度要求的不断提高,精确预测给定冲压件的回弹量大小显得非常重要。借助Dynaform软件对油孔卡环弯曲后的回弹规律进行了数值模拟,分析回弹产生的原因和影响因素,并利用正交实验找出制件最小回弹的条件组合。结果表明:在凸模圆角半径、活动夹块圆角半径、接触间隙、摩擦因数这4个因子中,凸模圆角半径对油孔卡环回弹的影响最大;最优成形参数为:凸模圆角半径30 mm、夹块圆角半径29 mm、接触间隙为1.1 mm、摩擦因数0.3。     

Influence of variables in deep drawing of AA 6061 sheet

Deep drawing is one of the most important processes for forming sheet metal parts.It is widely used for mass production of cup shapes in automobile,aerospace and packaging industries.Cup drawing,besides its importance as forming process,also serves as a basic test for the sheet metal formability.The effect of equipment and tooling parameters results in complex deformation mechanism.Existence of thickness variation in the formed part may cause stress concentration and may lead to acceleration of damage.Using TAGUCHI's signal-to-noise ratio,it is determined that the die shoulder radius has major influence followed by blank holder force and punch nose radius on the thickness distribution of the deep drawn cup of AA 6061 sheet.The optimum levels of the above three factors,for the most even wall thickness distribution,are found to be punch nose radius of 3 mm,die shoulder radius of 8 mm and blank holder force of 4 kN.     

工艺参数和材料性能对板料成形回弹的影响

分析总结了数值模拟中模拟参数（有限无算法、单元类型、材料模型、本构方程、积分点选取、接触和摩擦法则等）对回弹模拟精度的影响。对一细长支腿零件的工艺成形过程进行了数值模拟，研究了工艺参数及材料性能参数（压边力、凸模圆角半径、凸凹模间隙、板料厚度、摩擦系数、材料硬化指数）对工件回弹的影响。回弹角随凸模圆角半径和凸凹模间隙的增大而增大，随压边力、扳料厚度、摩擦系数和材料硬化指数的增大而减小。     

板料自由弯曲成形及回弹理论解析

对宽板自由弯曲成形及弹复过程进行理论分析,将弯曲过程分为板料未包覆凸模和已包覆凸模两个成形阶段,在每个成形阶段将弯曲板料分为弹性和弹塑性变形区。基于单向应力和小变形假设,分别建立了两个成形阶段的回弹计算模型,导出了任一成形阶段中性层上任一质点卸载前后的转角和弯曲半径数学表达式。基于VC++软件平台,对回弹计算模型进行编程计算,并进行了实验验证,计算结果与实验结果吻合较好,最大误差为0.58°。     

Springback behaviour in bending of ultra-high-strength steel sheets using CNC servo press

The springback behaviour of ultra-high-strength steel sheets in bending was investigated under controlled conditions using a CNC servo press. Although the ultra-high-strength steel sheets are attractive in reducing weight of cars, the amount of springback of the ultra-high-strength steel sheets in the forming is very large due to high strength. The CNC servo press has the function of accurately controlling the motion by two servo motors. The effects of the material, the finishing reduction in thickness, the forming speed and the holding time at the bottom dead centre on the amount of springback in V-shaped bending were examined. The scatter of the springback for the ultra-high-strength steel sheets was improved by using real thickness and not nominal thickness of each individual sheet in the control of the punch stroke. The amount of springback for the ultra-high-strength steel sheet in the V-shaped bending was much larger than that for the mild steel sheet, and the amount was decreased by the finishing reduction in thickness direction because of uniform stress distribution. The effects of the forming speed and the holding time at the bottom dead centre were small. The amount of springback for the steel sheets was almost proportional to the ratio of the tensile strength to the elastic modulus.     

高强度钢板V形弯曲板厚方向压缩对回弹的影响

定量评价了V形弯曲凸模在到达下死点后在板厚方向的压缩作用对减小回弹的影响.利用弹塑性有限元法对高强度钢板V形件的弯曲成形和回弹过程进行模拟,并通过实验进行验证.模拟结果显示:回弹随平均压强与抗拉强度比值的增大而减小;凸模圆角半径对回弹的影响不大;有限元网格划分影响回弹的模拟结果,细分网格并在与凸模接触的部分增加单元数量...     

加载速度和存放时间对树脂复合减振板弯曲类回弹的影响规律

随着树脂复合减振板的冲压件在汽车及家电等领域的广泛应用,其冲压成形性能研究受到重视。该文从加载速度及成形件的存放时间的关系出发,研究树脂复合减振板的弯曲回弹特性,通过采用90°V形弯曲件回弹模型,针对4种不同的加载速度和工件的存放时间,对树脂复合减振板进行回弹试验。试验结果表明,在加载速度为0.5mm/s~5mm/s时,随着加载速度的增加,树脂复合减振板的回弹角逐渐减小,直到趋于稳定;无论哪种加载速度,树脂复合减振板的回弹角均随存放时间的增加而减小,直到趋于稳定。     

凸模圆角半径对钢板冲压成形的影响

圆角半径的确定一直是冲压件工艺设计的关键技术,本文采用实验与理论模型相结合的手段,研究了凸模圆角半径对钢板冲压成形的影响。结果表明：冲压成形中的开裂位置和凸模圆角大小有关;圆角处的减薄率基本上与相对圆角半径R／t成反比;极限成形高度随凸模圆角半径的增大而增大。     

Prediction and elimination of springback in straight flanging using computer-aided design methods: Part 2: FEM predictions and tool design

Part 1 of this two-part paper presents the laboratory experiments on straight flanging, in which the influence of process variables, such as die shoulder radius, punch-die clearance, punch nose radius, pad force and material properties were discussed. This second part summarizes the FEM predictions for flanging and compares these results with some experimental data. Furthermore, flanging with coining to reduce springback has been investigated and evaluated by FEM for better dimensional control in flanging and hemming processes.     

Springback characteristics of steel sheets for warm U-draw bending

The purpose of this study is to investigate the characteristics of springback for various process conditions of the U-draw bending operation. The process variables are the forming temperature and the tool geometry, including punch profile radius (Rp) and die profile radius (Rd). In order to control springback, the use of a warm forming method is applied. For the warm draw-bending, five steps of temperature ranges, from room temperature to 200°C, were adopted. Two kinds of steel sheets, cold rolled carbon steel (SCP1, for general purposes in the automobile industries) and TRIP (transformation-induced plasticity) steel, were adopted. TRIP steel was the newly developed high-strength steel sheet. The results indicated that elevated temperature and the geometry of tools in the two kinds of steel sheet affected the springback.     

Effect of tool nose radius and tool wear on residual stress distribution in hard turning of bearing steel

This study presents a experimental investigation to clarify the effects of tool nose radius and tool wear on residual stress distribution in hard turning of bearing steel JIS SUJ2. Three types of CBN tools with different nose radius (0.4, 0.8 and 1.2 mm) were used in this study. The residual stresses beneath the machined surface were measured using X-ray diffraction technique and electro-polishing technique. The results obtained in this study show that the tool nose radius affects the residual stress distribution significantly. Especially the effect on the residual stresses at the machined surface at early stage of cutting process is remarkable. For the tool wear, as the tool wear increases, the residual stress at the machined surface shifts to tensile stress range and the residual compressive stress beneath the machined surface increases greatly.     

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。     

方形盒制件圆角处拉深破裂的数值模拟

金属薄板成形的数值模拟技术在冲压件生产和模具设计中起着重要的作用。文章借助Dynaform软件对某方形盒制件拉深破裂现象进行数值模拟,分析其产生原因和影响因素,并利用正交实验找出防止该制件圆角破裂的拉深条件组合。结果表明,在冲压速度、凸模圆角半径、摩擦系数和板料厚度4个因素中,凸模圆角半径对盒形件拉深破裂的影响最大。为降低因圆角处板料剧烈减薄而产生破裂的几率,盒形件拉深时应采用较大的凸模圆角半径。     

板金弯曲成形回弹问题的理论研究

分析了板金弯曲成形过程的回弹过程 ,利用成形过程中弯曲区域的平面应变和恒定厚度假设 ,根据VonMises屈服准则 ,建立了弹塑性材料线性硬化条件下板金弯曲成形的回弹计算模型 ,导出了纯弯曲条件下板金件的最小弯曲半径计算公式 ,并讨论了弯曲成形一般不等角平面弯曲问题的数值解法     

拉深筋对板料回弹影响的试验研究

分析了拉深筋对回弹的影响机理,试验研究了板料经过半圆形拉深筋后的回弹情况。结合极差分析法,研究了半圆形拉深筋主要几何参数对回弹的影响。研究表明,板料经过拉深筋后板内的残留应力是影响回弹的关键因素;拉深筋几何参数对板料的回弹具有决定性作用,拉深筋圆角半径对板料过拉深筋后的回弹有较大的影响。     

非等温模具对2024铝合金弯曲回弹和残余应力的影响

主要研究了2024铝合金在差温模具下弯曲成形时回弹和残余应力的变化规律。实验中选取板坯温度为25℃室温,凸模和凹模温度分别选取25,200,300和400℃共16组温度组合进行V型弯曲;然后进行板坯、凸模和凹模均为200℃的等温弯曲,并与差温弯曲进行对比分析。研究结果表明:分别提高凸模和凹模的温度均能够减小回弹角和残余应力;在成形结束后,当差温弯曲板坯和等温弯曲板坯开始回弹前的温度相接近时,由于温度梯度和贴模后温升的影响,差温弯曲件的回弹角和内、外表面残余应力及其差值能够达到与等温弯曲数值相近或更小的效果;通过合理控制凸、凹模温度能够使室温板坯获得与高温等温成形时同样较小的回弹和残余应力。     

U型钢压弯的有限元分析与回弹预测

采用压弯法对U型钢进行逐步冷弯成形分析。通过有限元和试验相结合的方式,得出较准确的回弹结果。经过数值模拟,发现变形过程产生的缺陷,在模具制造前修正了模具结构。在分析现有数据,参照板料成形设计公式的基础上,根据模拟结果,对板料成形的设计公式进行修正,在型材的弯曲凸模设计中引入相对弯曲半径系数K,设计出适合U型钢压弯的模具,在现场试验中取得了良好效果,生产出符合设计要求的工件。     

汽车轮毂端盖拉伸成形模计算机辅助工程

建立了汽车轮毂端盖拉伸成形三维弹塑性有限元模型,并利用MARC软件对其拉伸变形过程进行了数值模拟。分析了金属材料在拉伸成形时的流动及拉伸成形后的残留应力和应变分布情况,研究了凸模圆角半径对板料成形性能的影响及防止产生起皱与破裂的措施。研究结果表明,当凸模圆角半径值小于2~3倍料厚时,材料易产生拉裂现象。模拟结果与实际生产吻合较好,说明所建立的有限元模型是合理的。