三维曲面件柔性轧制成形有限元建模研究

利用柔性可弯辊轧制成形三维曲面件是一种新的板料成形方法,该文介绍了柔性轧制成形原理,基于离散化思想建立了刚性短辊按一定曲线排列的工作辊模型,解决了整体工作辊绕自身弯曲轴线无法转动的问题。给出了单元类型、网格划分技术、接触条件设置等关键问题的选择方法,利用建立的有限元模型模拟了凸曲面件的成形,模拟结果与理论分析和成形实验结果一致。     

基于六边界优化角度函数的多道次辊弯成形研究

目的 为了提高多道次辊弯成形中板材的成形质量、减少板材纵向弯曲缺陷的产生,提出一种基于新型六边界成形角度分配函数的多道次辊弯成形优化方法。方法 根据翼缘端部水平面投影五次曲线推导出最优辊弯成形角度公式,结合COPRA研究板件峰值纵向应变,以确定最佳成形角度分配区间;在相同条件下,利用Abaquse模拟与实验研究不同成形角度对帽形件辊弯成形纵向弯曲缺陷的影响,并分析辊弯成形工艺参数对板材辊弯过程中应力-应变的影响。结果 新型六边界成形角度分配函数的多道次辊弯成形方法可有效改善板材纵向弯曲缺陷;应力随着成形角度增量的增加而增大,等效塑性应变随成形角度和成形角度增量的增加而增加;实验与模拟结果基本吻合,验证了模拟结果的正确性。结论 优化成形角度分配函数的多道次辊弯成形方法可有效改善板材纵向弯曲缺陷,为提高辊弯工艺精度与板材质量提供一定的理论指导。     

冷弯薄壁卷边槽钢组合工字梁极限承载力计算的折减强度法

为了研究冷弯薄壁卷边槽钢组合工字梁的受弯性能,对3种截面形式共计9根卷边槽钢组合工字梁进行了破坏性试验研究,并采用有限元方法对试件进行模拟分析,有限元计算结果与试验结果吻合良好,验证了该文有限元方法的有效性。然后对典型截面梁构件进行了大量的参数分析,研究结果表明：随着钢材强度提高、梁长度减小、腹板高厚比和翼缘宽厚比增加...     

工艺参数对辊弯成形金属流动的影响规律

目的提高辊弯成形工艺中工件的最终成形尺寸精度,并为辊弯成形工艺参数的制定提供理论依据。方法以非能动空气导流板辊弯成形为研究对象,对不同参数下金属的流动规律进行研究。建立非能动空气导流板辊弯成形实验和仿真模型,根据模型,分析不同结构参数对金属成形流动规律的影响。结果较大摩擦不利于板材成形,摩擦因数为0.06~0.2之间时成形较好,建议采用塑料润滑;随着板材成形速度的增大,金属的变形抗力增大,板材与轧辊之间出现打滑现象,成形速度为5~10 m/min时成形结果较好;随着轧辊间距的增大,板材刚度降低,不利于板材成形,故其间距取为450~560 mm之间。结论实验结果与仿真结果基本一致,结果表明采用控制成形参数可以有效控制板材的金属流动,从而控制板材辊弯成形以得到更高精度。     

高强钢辊弯成形过程中成形力的影响因素研究

目的 探究辊弯成形过程中各工艺参数(板材厚度、弯曲角度以及总弯曲角度)对成形力的影响.方法 研究"日"字形截面的辊弯过程,利用ABAQUS有限元软件(FEA),建模分析辊弯成形过程中成形力大小的影响机制,避免实际生产中采集数据的复杂性以及困难性.为了避免各因素之间相互影响,采用单一变量实验法进行实验,根据不同板厚(1.5,2.0,2.5 mm)和弯曲角度(5°,10°,15°,30°)分别建立辊弯成形有限元模型,使板材从0°弯曲到90°,形成"日"字形截面,模拟计算后采集轧辊的成形力.结果 通过模拟结果与实际测量值对比可知,板材厚度为1 mm,弯曲角度为5°时,成形力误差为22.33％;当板料厚度为2.5 mm,弯曲角度为30°时,成形力误差为8.55％.模拟结果与实际测量值吻合良好,误差可控制在22％以内.结论 随板材厚度的增加,成形零件的强度增加,所需的成形力也大幅增加,呈现非线性关系.随弯曲角度的增加,成形力明显增大,呈现非线性关系.该结论为"日"字形截面型材成形力的选择提供了理论依据.     

铝锂合金飞机蒙皮滚弯成形试验研究

目的对第三代铝锂合金材料进行滚弯成形研究。方法对第三代铝锂合金2060-T8板料按照国标进行单拉试验,建立材料的本构模型,在此基础上采用滚弯解析计算与小件工艺试验对铝锂合金材料2060-T8的滚弯成形曲线进行了拟合,并根据曲线设计铝锂合金滚弯工艺参数,将工艺参数直接应用于实际零件的成形。结果由于大零件与小零件存在尺寸效应与各向异性的差别,设计的上辊下压量参数与实际零件的下压量存在一定的偏差,但偏差小于1 mm。结论通过解析计算与小件工艺试验对铝锂合金滚弯工艺参数进行设计的方法,对实际零件的成形过程有很好的指导作用,可以将该设计方法应用于实际零件的生产。     

基于成形角度分配优化函数的辊弯成形边波及纵向弯曲缺陷研究

目的 研究板材辊弯成形中弯曲角的分配方式,改善辊弯过程中出现的边波和纵向弯曲等各种缺陷,提高成形精度与质量.方法 以小截面型材帽形辊弯件为研究对象,首先提出五边界条件成形角分配函数,并进行成形角度优化,得到最优的成形角分配方法.其次研究各弯曲角度分配方式对板材产生的主要缺陷如边波及纵向弯曲的影响规律,并进行辊弯成形实验验证.结果 经过实验验证基于四边界条件的辊弯峰值纵向应变从4.15％降低到基于五边界条件的1.18％.验证了θN/3=33％×θ0时辊弯成形角度分配的合理性.结论 基于优化的弯曲角分配方式的纵向应变、翘曲波动量和偏差值、最大高度偏差都小于其他分配方式的相应值,表现出其在成形工艺上的优越性.研究结果为合理设计类似帽形件或复杂截面形件的辊弯工艺提供一定的理论指导.     

矫直辊辊型曲线对中厚板残余应力的影响

为深入研究矫直过程中矫直辊辊型曲线对中厚板残余应力的变化规律,分析了新一代矫直机的典型弯辊结构,针对其中一种弯辊结构运用接触有限元软件计算了其弯辊效果,得到了从负弯到正弯等多种矫直辊辊形曲线.建立了矫直辊辊形曲线对残余应力影响的解析模型和流程,运用数值方法求解该模型.研究结果表明:弯辊量对较宽的轧件的残余应力影响不显著,即使弯辊手段用反了,残余压应力仍然可以得到一部分消减;弯辊量对较窄的轧件的残余应力影响很大,如果弯辊手段用反了,残余拉、压应力都得不到有效消减.     

弯曲应力作用下的腹板转动约束刚度研究

畸变屈曲是冷弯薄壁卷边槽钢的重要屈曲模式,腹板提供给翼缘板的转动约束刚度是影响其畸变屈曲性能的关键因素之一。该文对弯矩绕截面强轴作用的冷弯薄壁卷边槽钢腹板,首先构造出一个满足全部边界条件的位移函数,利用迦辽金法求出弯曲应力作用下腹板提供给翼缘板的转动约束刚度近似解析解;接着利用有限元分析软件验证了其计算精度;最后研究提出了具有较高精度的转动约束刚度简化计算公式。研究成果为提出冷弯薄壁卷边槽钢在弯矩绕强轴作用下的弹性畸变屈曲荷载实用计算公式提供了依据和方便。     

树脂复合减振钢板U型弯曲回弹实验与数值模拟研究

通过带法兰边的U型弯曲成形实验研究,考察了树脂复合减振钢板在不同压边力下的回弹特性.实验结果表明:压边力对树脂复合减振钢板回弹特性影响显著.较大的压边力有利于减小回弹缺陷.其次,考虑树脂层的粘弹性特性,采用非线性粘弹性模型来描述树脂层的力学变形行为,并采用Cohesive单元和固体壳单元分别对树脂层和表层钢板进行离散,进行了树脂复合减振钢板在不同压边力下的U型弯曲有限元数值模拟研究.和实验结果比较表明,所建立的有限元模型能够较好的模拟U型弯曲成形过程.最后,基于建立的有限元模型,考查了成形速度,树脂层厚度和表层钢板初始屈服应力对回弹的影响.参数分析结果表明:这三个参数对回弹角的影响显著.该研究对树脂复合减振钢板冲压工艺设计具有一定的指导意义.     

径-轴双向环轧工艺的研究进展

回顾了环件径-轴双向轧制锻透条件、咬入条件、刚度条件等相关理论研究进展,分析了工艺参数对轧制过程的影响及其确定准则,在此基础上引入轧制曲线的概念,并给出了径-轴双向环轧轧制曲线的设计原则,还探讨了在利用有限元方法模拟轧制过程、优化轧制工艺参数时存在的问题,并给出了对数值模型进行控制和处理的有效方法。     

Simulation of Multiple Cold Rolls Progressive Forming for Non-symmetrical Channel Section

In cold roll forming process, the sheet is progressively formed into a very complex three dimensional surface. The design procedure for the roll formed products, forming rolls, and roll pass sequences was considered more an art than a science. Good roll pass design was the Key to successful roll forming. In order to reduce forming defects and trial production cost, computer     

Modelling of cold roll forming of steel strip

Abstract

Good roll pass design is the key to successful roll forming. To reduce forming defects and trial production costs, computer aided simulation of cold roll forming is employed. In this paper, a theoretical model, based on the updated Lagrange method of deformation mechanics and using the elastic–plastic large deformation B-spline finite strip method, is presented. The model is applied to analyse progressive roll forming of a channel section: the three-dimensional displacement field, strain field, and stress field between two stands during multiple cold roll forming are calculated. The results indicate that deformation is greatest in the leg and corner regions of the channel section. The principal deformation is in the transverse direction, the longitudinal deformation being small. The program, written in C language, can also be used to analyse other simple cross-sectional profiles.     

Development of a Model for Predicting the Transverse Coefficients of Thermal Expansion of Unidirectional Carbon Fibre Reinforced Composites

A model for predicting the transverse coefficients of thermal expansion (CTE) for carbon fibre composites is presented in this paper. The transverse CTE were calculated by finite element analysis using a representative unit cell. The analytical micromechanical models from literature were reviewed by comparing with the FEA data. It shows that overall Hashin model provides the best accuracy. However, the calculating process of Hashin model is very complicated and inconvenient for practical applications. By using FEA, Design of Experiments (DOE), and Response Surface Method (RSM), the transverse CTE of unidirectional carbon fibre composites were studied and a regression-based model was developed. The model was validated against the FEA and experimental data. It shows that the developed model offers excellent accuracy while reduces complicated computation process. The advantage of this model is that it provides a simple and accurate method for predicting the transverse CTE of composites, which helps effective and efficient design of composite structures.     

Evolution of elastic modulus in roll forming

Roll forming is a continuous process in which a flat strip is incrementally bent to a desired profile. This process is increasingly used in automotive industry to form High Strength Steel (HSS) and Advanced High Strength Steel (AHSS) for structural components. Because of the large variety of applications of roll forming in the industry, Finite Element Analysis (FEA) is increasingly employed for roll forming process design. Formability and springback are two major concerns in the roll forming AHSS materials. Previous studies have shown that the elastic modulus (Young’s modulus) of AHSS materials can change when the material undergoes plastic deformation and the main goal of this study is to investigate the effect of a change in elastic modulus during forming on springback in roll forming. FEA has been applied for the roll forming simulation of a V-section using material data determined by experimental loading-unloading tests performed on mild, XF400, and DP780 steel. The results show that the reduction of the elastic modulus with pre-strain significantly influences springback in the roll forming of high strength steel while its effect is less when a softer steel is formed.     

Study on Process Parameters Optimization of Sheet Metal Forming Based on PFEA/ANN/GA

Sheet metal forming is widely applied to automobile, aviation, space flight, ship, instrument, and appliance industries.In this paper, based on analyzing the shortcoming of general finite element analysis (FEA), the conception of parametric finite element     

Buckling failure analysis of all-terrain crane telescopic boom section

In this research work, a nonlinear structure analysis by the finite element analysis (FEA) was carried out to investigate the failure reason of an all-terrain crane telescopic boom. An overall simplified model consisting of telescopic boom and luffing jib was established by beam element, and analyzed using geometric nonlinear static method. A local detailed model consisting of the 4th and 5th telescopic boom section (TBS) was established by shell and solid element, and analyzed using geometric nonlinear and contact nonlinear static method. The result of the overall simplified model FEA indicated that the boom strength met the design criteria, and the 5th TBS of local detailed model occurred stress wrinkle.Structure experiment was designed based on the boom load characteristics in accident and analyzed using nonlinear static method and explicit dynamic method; the connection of load, boom buckling failure and stress wrinkle was studied. The result indicated that the accident was caused by elastic buckling. When the telescopic boom stress state changed from continuous state to wrinkle state, the buckling occurred. So the critical buckling state characteristic was stress wrinkle.     

TA2圆管辊弯成型边波缺陷及机理研究

目的 为消除TA2薄壁圆管在辊弯成型过程中产生的边波缺陷,研究分析不同成型方法中TA2薄壁圆管焊缝处纵向应力及应变大小的变化规律。方法 运用专业型钢软件COPRA RF和有限元MSC.MARC商业软件建立符合生产标准的三维薄壁圆管模型,展开多机架连续辊弯成型过程的有限元仿真,并进行辊弯成型试验验证。结果 试验结果表明,成型方式不合理是引起TA2薄壁圆管辊弯成型边波的重要原因。随着道次间成型结束后塑性应力与纵向应力的累积,TA2薄壁圆管焊缝处出现褶皱现象,即薄壁圆管产生边波缺陷。通过有限元分析及TA2纯钛薄壁圆管生产试验验证发现,基于普通成型法加工的薄壁圆管焊缝处失稳区辊弯纵向应变波动峰值由0.6%降低到基于上山法成型的0.3%。结论 使用上山法可以消除TA2纯钛薄壁圆管在辊弯加工工艺中产生的边波缺陷,提高了产品精度并为后续装配提供了保障,研究结果为消除工业纯钛圆管边波缺陷奠定了良好的理论基础。     

Contact geometry estimation and precise radial force prediction for the radial-axial ring rolling process

In the present research work, the modular parametric design plug-in Grasshopper, available in Rhinoceros 5, is utilized as a pre-processor for the estimation of the projection of the contact length between ring and tools in the radial-axial ring rolling process. The estimated lengths, for each round of the process, are then used in a slip line based force model for the precise estimation of the radial forming force. The proposed method allows reducing the inaccuracies of the traditional approaches since it supersedes the concept of common thickness draft on both mandrel and main roll side, allowing a more precise estimation of the projection of the contact arc between ring and tools, considered to have a unique value on both mandrel side and main roll side. The fulfillment of this last assumption ensures the forming force to have the same value regardless it is calculated on the mandrel side or on the main roll side. The model has been validated by cross-comparing the analytical results with those of laboratory experiment and finite element simulation. The developed analytical model has been also applied to three different study cases where the previous literature models for the calculation of the projection of the contact arc have shown inaccuracies, demonstrating that the proposed approach can overcome these limitations. The positive cross comparisons among laboratory experiment, FEM simulations, and analytical estimations prove the reliability of the proposed approach, as well as its good integration with authors’ previous analytical algorithms.