高强钢辊弯回弹的有限元分析

随着高强钢越来越多地应用于冷弯型钢,辊弯加工中回弹也就成了辊型设计的难点之一。文章建立了U形型钢辊弯成形回弹的有限元模拟模型,并验证了该模拟建模是可靠的。同时基于该模拟建模方法,探讨了各材料参数及工艺参数对高强钢(屈服强度300MPa~600MPa)辊弯加工产生回弹的影响规律。研究表明,在材料参数中随着屈服强度和强化系数的增加,产生的回弹明显增加;而随着强化指数和厚向异性系数的增加,产生回弹变化不明显;在工艺参数中随着弯曲角增量的增加,产生的回弹减小;随着机架间距增加,产生的回弹增加。     

高强钢胀弯成形卷曲回弹评价方法与影响规律研究

通过胀弯成形试验提出了采用面积法评价冲压过程中零件卷曲回弹的方法,借助试验研究和计算机仿真方法研究了胀弯成形卷曲回弹的主要影响因素对卷曲回弹的影响规律,得出了卷曲回弹诸多影响因素中,胀弯角度影响很小,拉深筋设计影响较大的结论。此研究可为高强钢模具设计中卷曲回弹控制提供参考。     

基于胀弯成形的高强度钢板回弹特性实验与分析

高强度钢板是汽车车身结构件广泛应用的材料之一,对比普通碳钢,高强度钢板具有较高的强度、较高的屈强比、较低的延伸率等,使用过程中容易产生开裂、起皱和回弹等缺陷,特别是回弹问题严重影响了零件的尺寸精度。文章以胀弯成形为基础,通过MTS试验机进行成形实验,研究了低合金高强钢B410LA、双相钢DP500在不同冲压参数、模具几何参数等条件下成形后的回弹影响规律,并通过显著性分析得出,胀弯角度对侧壁卷曲的影响不显著,拉延筋凸筋的位置对冲压回弹有较大的影响。     

QP980超高强钢V型弯曲回弹特性研究

针对第三代QP980超高强钢弯曲时容易出现回弹问题,通过V型弯曲试验研究了弯曲角度和相对弯曲半径对回弹的影响规律,掌握了QP980超高强钢的回弹特性。研究证明:QP980超高强钢的回弹角与相对弯曲半径成正相关性,与弯曲角度成负相关性。同时基于弯曲理论,采用最小二乘法对回弹角与相对弯曲半径和弯曲角度的关系进行拟合,获得QP980超高强钢弯曲回弹预测模型,为QP980超高强钢的弯曲工艺设计提供理论参考。     

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。     

基于Dynaform的高强钢板冲压回弹补偿分析

对高强钢的冲压回弹及回弹补偿原理进行了分析。以某乘用车B柱高强钢加强板零件冲压加工工艺为例,在模具设计阶段对整个工艺过程进行CAE分析,在工艺参数优化前提下,对回弹进行全序计算和预测,并对模具进行回弹补偿。为高强钢冲压模具设计及工艺参数优化提供依据,从而降低模具开发风险,减少试模时间,缩短开发周期,提高产品质量,降低生产成本。模拟结果与实验较吻合,表明所采用回弹补偿方法是可靠的。     

基于Dynaform的高强钢U形件回弹影响因素研究

基于有限元理论与选定的回弹角度判定标准,采用Dynaform软件探究了汽车U形件在弯曲成形过程中压边力、摩擦系数、板料厚度和凸模圆角半径对回弹的影响。研究结果表明：回弹角度随板料厚度增厚而降低,随凸模圆角半径增加而增加,随压边力增大先增大后减小,随摩擦系数增加先增大后减小。不同因素对回弹影响程度并不相同,在选定参数范围内板料厚度因素影响最明显,压边力次之,摩擦系数略低于压边力,凸模圆角半径影响最小。     

板材回弹对高强钢轮毂疲劳性能影响

车轮用高强钢回弹大、成形难度大,对零件性能影响大。选用15X6车轮研究了回弹角度对疲劳性能的影响,发现轮辐冲压后接合面回弹角度为4°,装配后轮毂的疲劳寿命达不到设计要求。采用数值模拟方法,建立有限元模型分析了不同回弹角度对高强钢轮毂过盈配合的影响,发现回弹角度为4°时,轮辋和轮辐配合面有间隙,且出现应力集中,回弹角度小于2°后消除。设计整形模具对轮辐进行整形,降低回弹角为2°,与轮辋配合疲劳寿命达到了设计要求。     

拉伸量对拉弯成形回弹的影响机理

针对不锈钢型材拉弯,基于ABAQUS软件研究了拉伸量和不同拉伸量分配方式对回弹的影响机理。首先,通过仿真实验,分析了不同拉伸量下卸载前后圆弧截面上应力的分布情况。然后,在拉伸量相同的条件下,对4种拉伸量分配方式下的回弹差异进行了机理分析。结果表明,随着拉伸量增加,截面上应力分布差值逐渐减小,从而使回弹量减小,且卸载后残余应力减小。在拉伸量相同时,不同分配方式导致截面上产生不同程度的塑性变形,从而使回弹产生差异。当拉伸量为3%时,截面未完全进入塑性拉伸变形,此时4种拉伸量分配方式中前期分配拉伸量较小的线性递增产生的回弹最小。当拉伸量为5%时,截面完全进入塑性拉伸变形,此时前期分配拉伸量较大的均匀拉伸产生的回弹最小。     

高强度钢板U形件冲压回弹的仿真研究

利用Dynaform软件对高强度钢板U形件在不同成形参数下的回弹情况进行了模拟分析,着重研究了压边力和摩擦因数对回弹的影响,并通过试验对模拟结果进行了验证,对实际生产具有指导意义。     

Pulsed electrohydraulic springback calibration of parts stamped from advanced high strength steel

Electrohydraulic calibration (EHC) of springback is a novel method of removing springback from stamped sheet metal panels and is based upon the electro-hydraulic effect: a complex phenomenon related to the discharge of high voltage electrical current through a liquid. The EHC process involves clamping a stamped panel against a female die with the desired part shape and then applying several pulses of pressure onto and through the thickness of the sheet, in a process somewhat similar to conventional coining operations. However, in EHC the pressure is applied by a fluid and through the use of the electrohydraulic effect, and not with a matching hard tool as done in coining. In EHC, electrical energy is stored in a bank of capacitors and is converted into kinetic energy within the liquid by rapidly discharging the stored energy across a pair of electrodes submerged in a fluid. The objective of this paper is to describe the newly developed EHC process, to report the results of early proof-of-concept experiments, to present the results of more advanced experiments using a more industrial tool and actual part geometry, and to describe how numerical modeling techniques were used to optimize the design of the larger and more industrial tool. The developed concept of electrohydraulic stress relieving calibration is based upon clamping a stamped panel to the calibration die surface with the target shape and then applying pulses of pressure to eliminate internal stresses in the stamped panel. When a stamped blank is removed from a forming die, allowed to springback, and then clamped to a calibration die, the internal elastic stresses within the panel in such a configuration serve as a memory of the shape of the blank after springback, and it is these residual stresses that EH calibration is intended to remove from the panel. The developed concept of stress relieving calibration was initially validated by a simple experiment consisting of submerging a bent strip of aluminum into the fluid within an EH chamber, so that both the outer and inner surfaces of the strip (where the internal stresses from bending are located) were exposed to the fluid and the pressure pulse. This experiment served as an initial confirmation that impact with the tool is not necessary to achieve the calibration effect. The sheet metal materials used in this study, and for which springback was eliminated after forming, include DP 980 at 1.0 mm and 1.4 mm thick, and also DP600 at 1.0 mm thick.     

高强钢板冲压位移回弹补偿技术研究与应用

回弹是高强钢板零件冲压中的一大难题,当前工程应用中仍然依赖大量修模解决回弹问题。该文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;利用位移回弹补偿原理,对拉延型面和修边型面进行回弹补偿,使冲压回弹后的零件尺寸满足设计产品的精度要求。该研究提高了高强钢冲压件的质量,实际生产的应用效果良好。     

先进超高强马氏体钢的成形回弹控制

先进超高强马氏体钢是汽车轻量化极具潜力的钢种,但其强度高、塑性低、成形回弹量大,成形精度难以保证。文章以有限元软件ABAQUS为平台,针对1500MPa级别马氏体钢开展回弹控制方法研究,并进行实验验证。研究表明,采用变压边力和成形拉伸(form drawing)均可有效抑制回弹,而后者表现了更好的回弹抑制效果,成形拉伸中的压边力加载时刻与压边力对回弹抑制效果影响较大。     

Air bending and springback of stainless steel clad aluminum sheet

This paper deals with bending and springback phenomena of a stainless-steel clad aluminum sheet in V-shaped air bending. The aim of this study is to investigate the bending characteristics such as sheet thickness change and the bending angles of the sheet before/after springback. The first part of this paper is on the experimental observations. V-bending experiments were performed for both the cases of Al_in/SS_out (i.e., aluminum layer is located inside the bent clad) and SS_in/Al_out (i.e., stainless-steel layer is located inside the bent clad). From these results, it was found that the sheet-set condition (either Al_in/SS_out or SS_in/Al_out) has a great influence on the bending phenomena. In the second part, the accurate prediction of springback by FE analysis, especially the role of elasto-plasticity models, is discussed. When using Yoshida–Uemori kinematic hardening model (F. Yoshida, T. Uemori, Int. J. Plasticity 18, 2002; Int. J. Mech. Sci., 45, 2003), which well describes the Bauschinger effect of materials, the springback of the clad sheet is accurately calculated, whereas the classical isotropic hardening model underestimates the springback.     

高强度钢筋弯箍回弹角及箍筋精度研究

高强度钢筋在弯箍机上进行弯箍加工成一定角度后,在残余应力作用下钢筋会产生回弹现象。为了提高箍筋角度的精度,需要考虑回弹角度对箍筋角度的影响。基于弹塑性弯曲回弹理论,考虑加工硬化影响的情况下,推导出箍筋角度与回弹角度的关系式。并基于弯箍转盘几何模型,推导出弯箍转盘转角与箍筋角度的关系。应用MARC有限元软件建立弯箍模型,分析了弯箍成形速度、弯箍轴回转半径对钢筋回弹角的影响。进行弯箍成形实验,结果表明,弯箍成形速度对回弹角度影响较小,回弹角随着弯箍轴回转半径的增大而增大,实验结果与有限元模拟结果基本吻合。