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。     

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。     

盘件辗轧成形技术研究进展

辗轧成形作为一种先进的连续局部塑性回转成形工艺,具有成形载荷小、生产过程自动化、近净精确成形等显著的技术经济优点。盘类零件作为重要的承载基本零件类型之一,采用辗轧技术成形盘件是机械行业的重大技术创新。介绍了采用辗轮的盘件辗轧机成形盘件的工艺原理和研究现状,叙述了利用技术改造的数控径轴向环轧机辗轧盘件的工艺原理及研究进展,结果表明盘件辗轧成形技术作为一种先进的零件柔性近净制造技术,具有十分诱人的应用前景,是未来制造业的发展方向。     

整体式超高强钢冷冲压门环零件开发

目的研究整体式超高强钢门环对车身碰撞安全性能的影响,探索高性能超高强汽车用钢制作整体式冷冲压门环零件的可行性。方法充分利用高性能超高强钢的材料特性,设计开发整体式超高强钢冷冲压门环零件,通过结构设计、坯料制备、样模开发、零件试制,研究门环零件焊缝优化、闭环坯料拼焊、大尺寸模具调试等关键工艺技术。结果整体式超高强钢冷冲压门环零件可以有效提高整车侧面碰撞性能,增强抵御25%小偏置碰的能力,实现质量减轻2%,回弹仿真精度达到75%。结论这是对整体式超高强钢门环零件的一次有益探索和尝试,整体式超高强钢门环较分体式门环在满足相同碰撞安全要求前提下,具有结构简单,可实现减重、降低模具数量和生产成本等优势,后续在零件回弹控制方面还需进一步深入研究。     

Titanium based cranial reconstruction using incremental sheet forming

In this paper, we report recent work in cranial plate manufacturing using incremental sheet forming (ISF) process. With a typical cranial shape, the ISF process was used to manufacture the titanium cranial shape by using different ISF tooling solutions with and without backing plates. Detailed evaluation of the ISF process including material deformation and thinning, geometric accuracy and surface finish was conducted by using a combination of experimental testing and Finite Element (FE) simulation. The results show that satisfactory cranial shape can be achieved with sufficient accuracy and surface finish by using a feature based tool path generation method and new ISF tooling design. The results also demonstrate that the ISF based cranial reconstruction has the potential to achieve considerable lead time reduction as compared to conventional methods for cranial plate manufacturing. This outcome indicates that there is a potential for the ISF process to achieve technological advances and economic benefits as well as improvement to quality of life.     

Simulation and software design of continuous flexible roll bending process for three dimensional surface parts

Continuous flexible roll bending process, due to its advantages of flexibility and continuous roll forming, exhibits a great ability to manufacture three dimensional surface parts effectively. To obtain a final part with desired shape and eliminate the need to depend on the experiences and skills of the operator, the longitudinal and transverse mathematical models were presented for predicting the curvatures in sheet metal forming process. A software system, which was guided with the automation and precision producing concepts, was designed based on the mathematical models for controlling the continuous flexible roll bending process. The algorithms of the mathematical models were verified by comparisons of the desired and the numerical simulation results. An application experiment for saddle surface part was performed using the developed software. Compare the experiment result with the target shape, it shows that the software system is reliable.     

闭式冷弯成形辊花设计映射数学模型及实验研究

针对金属闭式冷弯成形的多道次孔型轧制特点,考虑轧前管坯的轮廓与轧后异型管的轮廓存在拓扑等价关系和边界域的不动点性质,以双圆弧插值函数描述异型管的复杂轮廓,建立两者之间的形心映射数学模型,实现各道次孔型设计,绘制异型管闭式冷弯成形过程的辊花图。以铝合金圆管为坯料在试验轧机上进行了扇形管冷弯成形轧制实验,结果表明:轧后的扇形管内外轮廓变形柔顺且无凹凸点,壁厚偏差小于±0.5 mm,角部误差小于±1.5°,满足GB/T 6728-2002国标要求,研究结果为异型管冷弯成形的轧辊辊花设计提供了一种新方法。     

冷轧带钢孔洞缺陷分析及对策

为防止冷轧板中产生孔洞缺陷,从轧制工艺因素考虑,必须选择合适的辊型.此外,还必须考虑材质因素,要对冷轧原材料中夹杂物的大小、形态和分布进行限制.     

辊锻制坯模锻长轴类零件的模拟研究

根据所研究零件纵向截面变化较大的特点,设计出辊锻制坯方案来对坯料的纵向进行体积重新分配.经过体积重新分配的坯料在模锻过程中金属流动较直接模锻更为简单,从而避免了折叠等成形缺陷的产生,同时降低了模锻成形栽荷和对设备的要求。通过Deform-3D对辊锻及模锻过程进行模拟并分析其载荷及速度场,得到了较好的结果。     

Rapid Prototyping of Ceramica via Temperature Induced Forming

Rapid tooling is the process of directly or indirectly employing rapid prototyping technologies in tool and mold fabrication. By combining rapid tooling and temperature induced forming (TIF) a novel near-net shape process for the rapid production of complex-shaped prototypes of advanced ceramics has been developed. Rapid tooling via stereolithography quickly produces complex-shaped molds with precise surface quality and the TIF technology enables the forming and consolidation of Al2O3 green bodies in nonporous molds. Thus Al2O3 green parts with high density and without any cracks are realized. This novel process shows excellent potential for near-net shape production of advanced ceramics with complex geometry, fine surface finish and reliable mechanical properties.     

Plasma-Jet Forming of Sheet Metal Shapes

Plasma-jet forming is a newly proposed flexible sheet metal forming process. A non-transferred arc plasma torch is used as a controllable heat source to produce internal stress in sheet metals, causing plastic deformation without the necessity of hard tooling. This method has potential for rapid prototyping of sheet metal parts by reducing development costs and lead times. A robotic system has been used to perform simple linear bends in several different alloys. In order to develop a controllable process and to improve the forming accuracy, the effects of various process parameters on the obtained shape changes and ton the resulting structure and properties have been studied. The overall goal is to understand the roles of the forming parameters and their inter-relationship in optimizing the forming procedure-a high forming speed without damage to the material structure or properties.     

ALE finite element formulation for ring rolling analysis

In this paper, a ring rolling process is analysed by the Arbitrary Lagrangian Eulerian (ALE) finite element method. Phenomena associated with the process, such as large deformations, elastoplastic material behaviour and the friction on the interface, are included in the analysis. Special modelling on driven, idle and guide rolls is given. Results which include the overall shape of the formed ring, the time histories of roll separating force and driving torque, the distribution of the normal pressure on the ring–roll interface as well as the distribution of effective stresses in the formed ring, are also presented.     

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.     

Roll forming continuous fibre-reinforced thermoplastic sheets: experimental analysis

This paper describes the results of an experimental roll forming study performed on sheets of continuous fibre-reinforced thermoplastic (CFRT) material. The deformation length, or transitional region over which the material deforms under each roll station, is studied for various temperatures, laminate configurations, and roll settings using still photography and surface grid strain techniques. The severity of the deformation through the first forming pass has been found to be related to the fibre architecture as well as the forming temperature. The kinematic constraints imposed by the fibres are found to result in a trellising effect that is observed clearly using surface grid strain techniques. Finally, as a first step in the theoretical analysis of the process, kinematic relations are developed, which describe the rate of change of strain in a sheet through the deformation zone.     

Analytical modeling of deformed plain woven thermoplastic composites

This research addressed the deformation predictability of post-manufactured, plain weave architecture composite panels. Often times during the production of deep drawn composite parts, a fabric preform experiences various defects ranging from local buckling, interply slip, intraply shear, delamination, overheating and thickness variations. Minimizing these defects is of utmost importance for mass produceability in a practical manufacturing process. Considering intraply shear as the enabler for panel alteration, characterization of the local trellis angles can lead to better understanding of defects. The approach is analogous to forming limit diagrams used as a design tool in the sheet metal industry when developing new products to predict draw depth based upon the strain characteristics of the material. There were two broad objectives of this research. The first objective was to adapt a grid strain analysis technique to characterize surface deformations. These deformations were related to the extent of local trellis shearing and were used as a validation tool. The second objective was to generate a predictive model with the use of a bilinearly blended Coons patch to predict formability for the top surface of a composite panel. This model was generated independently of the results obtained from the grid strain analysis. By implementing this analytical, predictive model, it was possible to characterize formability of a composite part using nothing more than geometry of tooling, material thickness and imposed boundary conditions.     

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     

Thermo-mechanical sheet metal forming of aero engine components in Ti-6Al-4V – PART 1: Material characterisation

Ti-6Al-4V is one of the most frequently used titanium alloy in aerospace applications such as for load carrying engine structures, due to their high strength to weight ratio in combination with favourable creep resistance at moderate operating temperatures. In the virtual development process of designing suitable thermo-mechanical forming processes for titanium sheet metal components in aero engine applications numerical finite element (FE) simulations are desirable to perform. The benefit is related to the ability of securing forming concepts with respect to shape deviation, thinning and strain localisation. The reliability of the numerical simulations depends on both models and methods used as well as on the accuracy and applicability of the material input data. The material model and related property data need to be consistent with the conditions of the material in the studied thermo-mechanical forming process. In the present work a set of material tests are performed on Ti-6Al-4V at temperatures ranging from room temperature up to 560°C. The purpose is to study the mechanical properties of the specific batch of alloy but foremost to identify necessary material model requirements and generate experimental reference data for model calibration in order to perform FE-analyses of sheet metal forming at elevated temperatures in Ti-6Al-4V.     

基于弯曲实验的DP980力学性能研究

目的 针对仅通过单向拉伸实验无法准确表征金属板材在弯曲成形过程中的力学性能变化的问题,研究通过弯曲实验获取材料力学性能参数.方法 对高强钢DP980展开力学性能测试研究,主要通过弯曲实验对材料弯曲变形过程中形成的弯矩曲率进行测试,将得到的弯矩曲率转化为应力-应变.分别将弯曲和拉伸得到的应力-应变数据导入到三点弯和辊弯成...     

Modeling of the Shape Forming of Composite Roll

1. IntroductionSpray forming is a novel rapid solidification technology capable of manufacturing high quality roll ina single integrated operation. During spray formingprocess, alloy melt is atomized by high-speed gas jetsto form a spray of fine droplets. These droplets arecooled rapidly and sprayed onto a substrate bar in asemisolid state, resulting in a near-net-shape roller.Compared with conventional technologies (e.g., I/Mmethods), this advanced technology has a great dealof advalltages o…     

Improvement strategy for edge waviness in roll bending process of corrugated sheet metals

This paper focuses on the corrugated thin-walled sheet metal in the roll bending process. The main defect that appears in corrugated panels subjected to high amounts of bending deformation is a wavy edge. Edge defects are caused by excessive longitudinal stress and strain near the edge of the plate, and local edge buckling may occur when some critical value of the bending radius is exceeded. This paper proposes two different approaches to avoid a wavy edge for a formed panel: excessive stress on the edge region is restrained by controlling the length of the cross-sectional end of the corrugated panel while considering the stress distribution, and the bending radius in each forming step is determined by considering the strain limit at which the initial edge waviness occurs to avoid excessive compression at particular steps. The experimental and numerical results indicated that the two proposed design strategies can minimize wavy edges in the formed shape.