Research on forming precision of flexible rolling method for three-dimensional surface parts through simulation

Flexible rolling is a novel forming process for three-dimensional surface parts using a pair of bendable rolls. By controlling the distribution of the gap between the upper and lower forming rolls in the rolling process, the sheet metal is nonuniformly thinned in the thickness direction and the longitudinal elongation is different in the width direction of the sheet metal, which makes the sheet metal deform in rolling direction. With the rotation of the bendable rolls, the sheet metal is deformed consecutively and a three-dimensional surface part could be obtained. A small experimental device has been designed. Finite element analysis (FEA) model is established. Spherical surface and saddle surface are simulated, and their experimental results are presented. The major purpose of the present work is to analyze the forming precision of flexible rolling and the reasons for the shape errors through simulated and experimental results. The results demonstrate that the proposed process is a feasible and effective way of forming three-dimensional surface parts.     

Research on three-dimensional surface parts in multi-gripper flexible stretch forming

Multi-gripper flexible stretch forming (MGFSF) is a novel flexible forming process of sheet metal based on the multi-point forming principle. The straight jaws in traditional transverse stretch forming (TSF) are replaced by several discrete clamping mechanisms on both sides. To help understand the forming characters of MGFSF, spherical and concave–convex parts were selected as the research objects and finite element analyses on TSF and MGFSF were implemented using an explicit nonlinear finite element code. The influence of the transition length on the forming results in MGFSF was also taken into account in the present work. The simulation results reveal that a shorter transition length in MGFSF would result in an easier conformability of the sheet metal to the desired shape as well as a smaller strain variation in the forming zone. It is also found that, compared to TSF, the sheet metal can be formed without transition zone by utilizing MGFSF, which could significantly improve the material utilization and save the manufacturing costs. Finally, experimental validations were conducted on the self-developed MGFSF apparatus and the experimental results show a good agreement with the numerical results.     

Hydrodynamic effects of macroscopic deterministic surface structures in cold forging processes

The tribological conditions between tool and workpiece are crucial for process feasibility and tool durability especially in bulk metal forming processes. Therefore, friction as one main parameter in forming needs to be adjusted sensitively. While in sheet metal forming lubricant pockets are known as an appropriate way to minimize friction forces, these reservoirs for lubricants are not state of the art in bulk metal forming. This paper describes the tribological benefit of macroscopic deterministic structured semi-finished parts in cold forging.     

Continuous-forming method for three-dimensional surface parts combining rolling process with multipoint-forming technology

Flexible rolling is a novel forming process for three-dimensional surface parts, which combines the rolling process with multipoint-forming technology. This process employs a pair of forming rolls as a forming tool. By controlling the gap between the upper and lower forming rolls, residual stress caused by the longitudinal non-uniform elongation of sheet metal makes the sheet metal generate three-dimensional deformation. In this paper, the improvement of the process is introduced that the middle curve radius of the roll gap is much larger than the transverse curvature radius of the forming surface in the forming process. The forming roll rotates around its own axis easily because of the small bending deformation which is suitable for producing three-dimensional surface parts including the wide sheet metal with a relatively small transversal curvature radius. The forming principle is set forth, and corresponding formulations are presented. Finite element analysis model is established, and spherical and saddle surface are simulated. The forming precision and the causes of the shape errors are analyzed through simulated results. The experimental equipment is designed and their experimental results are obtained. Simulation results are in well agreement with the experimental results, which verifies the feasibility of using simulation to guide the experiment. The results of both numerical simulations and experiments show that the proposed process is a feasible and effective way of forming three-dimensional surface parts.     

Contact simulation for predicting surface topography in metal forming

A surface contact model that takes account of flattening, roughening and tool elastic microwedge effects on workpiece surface is developed. The model can be implemented in FEM codes to predict the final surface qualities of the products in metal forming. As an example, the proposed model has been combined with a membrane finite element code of sheet metal forming process to predict the contact area ratio, surface roughness and mean asperity spacing. Numerical results showed good agreement with the experiments.     

基才Pro／E三维钣金展开的CncKad数冲加工

详细介绍了采用Pro／E三维设计软件和CncKad数控加工软件辅助钣金件的设计与加工制造的完整过程。用Pro／E软件的钣金模块进行钣金件设计建模时,需要根据钣金材料和厚度设置折弯表程序,调用相应的折弯表,将钣金件展开成平整状态。Pro／E软件与CncKad软件集成后带有CncKad功能模块,将展开好的钣金件导入到该功能模块中,采用CncKad软件自动或者手动冲压功能加装模具,生成数冲程序,控制数冲机床加工钣金件。     

基于面融合技术的钣金CAD

提出了一种基于面融合技术的钣金零件设计方法,利用该方法不但能够方便地设计出钣金零件的三维结构,实现钣金零件的展开,而且可以根据展开工艺原理生成二维展开图。最后给出了一个开关柜行业钣金零件的设计和展开的实例。     

飞机钣金特征自动化建模技术研究

为了实现飞机钣金工艺几何特征的自动化设计,对传统的飞机钣金特征建模方法进行了研究,提出了飞机钣金特征自动化建模技术,基于知识与特征设计,开发了飞机钣金特征自动化建模系统,实现了钣金几何特征的快速自动生成,提高了飞机设计效率。     

飞机钣金特征自动化建模技术研究

为了实现飞机钣金工艺几何特征的自动化设计,对传统的飞机钣金特征建模方法进行了研究,提出了飞机钣金特征自动化建模技术,基于知识与特征设计,开发了飞机钣金特征自动化建模系统,实现了钣金几何特征的快速自动生成,提高了飞机设计效率。     

钣金冲模集成制造系统的产品信息建模

计算机集成制造是模具生产集成化和智能化的最高体现,建立钣金冲模产品信息模型是实现模具集成制造的基础。本文针对钣金冲模集成制造的功能模块,建立系统的功能模型,并给出结构化分析的 Ｉ Ｄ Ｂ Ｆ０ 图形表达;分解模具集成产品模型为制件模型、制件展开分析模型、工步设计模型、模具设计模型、零件设计模型、数控加工模型和模具装配仿真模型等,并用 Ｅ Ｘ Ｐ Ｒ Ｅ Ｓ Ｓ语言建立信息模型。     

基于实例的飞机钣金工艺设计

基于实例的钣金工艺设计是一种运用实例推理方法开发钣金工艺辅助设计系统的新思路。实例表达、实例相似性匹配算法是系统实现的关键。本文采用面向对象技术表达飞机钣金工艺实例 ,采用模糊相似算法进行实例相似性匹配 ,提出了一种基于实例的飞机钣金工艺设计系统构建方法     

Viscous pressure bulging of aluminium alloy sheet at warm temperatures

Improving the formability of aluminium alloy sheet metal by using warm or elevated temperature has become a valid approach. In this paper, viscous pressure bulging (VPB) at warm temperature is proposed. The coupled thermo-mechanical finite element method and experimental method were used to investigate the VPB of aluminium alloy AA3003 at warm temperature. The temperature distributions of sheet metal and viscous medium were analyzed for non-isothermal VPB. The influence of forming temperature on thickness distribution, forming load and failure location of sheet metal were investigated. Research results show the temperature gradient field in sheet metal forms when the initial temperature of viscous medium is lower than that of sheet metal. The formability and failure location of sheet metal changes with initial temperature of viscous medium.     

Formability analysis on the process of multi-point forming for titanium alloy retiary sheet

The multi-point forming (MPF) process of spherical surface parts of titanium alloy retiary sheet and titanium alloy sheet metal with different thickness and curvature radius was simulated by an explicit finite element software. Contradistinctive analysis between retiary sheet and sheet metal forming parts with different modes were done. The simulation results show that under the same forming conditions, titanium alloy retiary sheet is not easy to wrinkle and springback, whereas it is easy to form. The reason for differences in the formability of above-mentioned sheet metal is also analyzed. A non-wrinkling limited graph and a fracture critical graph for spherical surface parts of retiary metal sheet and metal sheet were obtained. Finally a forming test of titanium alloy cranial prosthesis was done in MPF press. Testing results indicate the customized 3D curved surface of prosthesis can be adequately shaped and the forming quality was guaranteed.     

Pro/E软件实现90°角钣金件1∶1展开的二次开发及应用

目前在钣金企业中,钣金件展开图绘制的效率较低,且易出错误。本文通过分析90°角钣金件展开长度的计算方法,对Pro/E软件自带的折弯表进行二次开发。对于前期90°角钣金件的Pro/E模型,通过加载二次开发折弯表,可以实现1∶1准确展开;对于新建90°角钣金件的Pro/E模型,可通过对钣金件公制、英制模板文件设置后,直接按照1∶1准确展开,展开后工程图可以保存为DXF文件,可以直接输入到数控塔冲和数控激光切割机中进行编程加工。二次开发折弯表仅适用于90°角钣金件。     

Solid Edge在圆锥台钣金件展开设计中的应用

对圆锥台钣金件的传统展开方法与应用Solid Edge钣金模块进行展开的方法做了分析比较.并通过一个实例介绍了Solid Edge钣金模块展开圆锥台钣金件的具体过程和注意事项,阐明了该种方法可以精确、快速、直观地展开各种不同的圆锥台钣金件,大大提高了饭金件设计的精确率及效率.     

金属板材成形应力统一解

为了弄清材料拉压强度不相等时板材成形问题的应力解答和最大截面缩减率,根据统一强度理论,对金属板材成形问题进行分析,得出考虑中间主切应力影响和材料拉压比影响的金属板材成形应力统一解,以及反映最大截面缩减率与拉压比和中间主切应力参与系数之间关系的统一解,给出韧性金属板材成形最大截面缩减率可能的取值域.分析过程中引入一个反映金属板材拉制和压制工艺的系数,将金属板材成形问题的拉制解和压制解统一起来.当材料拉压强度相同时,金属板材成形应力统一强度理论解退化为金属板材成形应力统一屈服准则解,金属板材成形应力的Mises解是金属板材成形应力统一屈服准则解的特例.     

TOOL PATH GENERATION BASED ON STL FILE FOR SHEET METAL DIELESS FORMING

Sheet metal dieless forming is a new metal forming technology. This technology adopts theprinciple of rapid prototyping technology, so it can form sheet metal parts without traditional die andmoulds. According to the charateristic of sheet metal dieless forming technology a new way of toolpath generation based on the STL file for sheet metal dieless forming is proposed.     

金属板材单点渐进成形技术的研究进展

金属板材单点渐进成形技术是一种新的板材无模成形技术,它可直接从CAD数据快速、经济地制造出复杂形状的板材件而无需昂贵的模具,并可广泛应用于样件试制和小批量生产。本文分析了金属板材单点渐进成形技术的基本原理、研究现状,探讨了存在的问题和发展趋势。     

L形折弯钣金的冲模设计技巧

以L形折弯钣金的冲压模设计为研究对象,提出了一种利于模具高效生产和稳定的设计方法。核心思想就是把L形钣金转化为利于冲压平衡的U形钣金,最后进行分离的方式。文中重点探讨此类冲压模具的结构,运用AutoCAD软件进行L形折弯钣金的级进模设计,说明此类设计的一般性方法与技巧,从而实现模具的高效率生产,并实现模具运动可靠。     

基于CATIA的飞机钣金结构特征参数化设计系统

提出了飞机钣金结构特征参数化设计系统的体系框架;构建了由特征参数库和特征模板库组成的飞机钣金结构特征数据库。通过CATIA提供的数据输入接口和功能构件开发了设计系统,实现了飞机钣金结构特征的参数化三维建模。工程应用实例表明,设计系统在飞机钣金结构设计中提高了设计质量和设计效率。