Development of a Highly Flexible Incremental Roll Forming Process for the Manufacture of a Doubly Curved Sheet Metal

A flexible incremental roll forming process has been developed by adopting the advantages of the incremental forming process and the roll forming process: i.e., inherent flexibility of the incremental forming process and continuous bending deformation of the roll forming process. It has an adjustable roll set as a forming tool composed of one upper center roll and two pairs of lower support rolls, which plays a key role. Through the experiments, it is shown that the improved forming method of the proposed process is effective in the manufacture of various doubly curved sheet metals, and the proposed relationship of the experimental parameters and the radius of curvature of the formed sheet boundary is useful to control the final shape     

Forming strategies and Process Modelling for CNC Incremental Sheet Forming

Incremental Sheet Forming (ISF) is a process capable of producing complex sheet components by the CNC movement of a simple tool in combination with simplified dies. Earlier work revealed two major process limits, namely the limitation on the maximum achievable wall angle, and the occurrence of geometric deviations. The work detailed in this paper focuses on forming strategies to overcome these process limits, including the processing of tailor rolled blanks. Additionally, finite element modelling of the process is presented and discussed with respect to the prediction of the forming limits of ISF.     

金属板料渐进成形工艺过程有限元模拟

介绍了金属板料分层渐进成形过程有限元模拟。在金属板料渐进成形过程中,材料的弹塑性变形十分复杂,影响成形过程的因素很多,同时各个工艺参数对成形过程的影响又很难确定。为此,根据金属板料分层渐进成形为多工步成形的技术特点,建立一种有限元模拟方案,对板料渐进成形过程进行了模拟分析。     

Single Point Incremental Forming and the Forming Criteria for AA3003

Single Point Incremental Forming (SPIF) is a modern method of forming sheet metal, where parts can be formed without the use of dedicated dies. The ability of SPIF to form a part is based on various forming parameters. Previous work was not accomplished with the help of design of experiments, thus reducing the number of parameters varied at any time. This paper presents two designs of experiments, which formalise the forming parameters critical in SPIF and the degree to which they affect formability.     

Numerical and experimental investigation into cold incremental rolling of doubly curved plates for process design of a new LARS (line array roll set) rolling process

The line array roll set (LARS) rolling process is a new incremental sheet metal rolling process for effective manufacture of doubly curved metal plates. In this study, design equations were developed to predict the curvatures of formed plate shapes with complex curvatures using the experimental data. A series of experiments with various curvatures have been performed. The comparison of the finite element computation results with the design equations has shown that the design equations can be effectively used for process design of forming processes in forming of doubly curved plates over a wide range of input curvatures.     

On-Line Control of Single Point Incremental Forming Operations through Punch Force Monitoring

Among the innovative sheet metal forming processes, Single Point Incremental Forming (SPIF) represents the simplest and the cheapest one. Despite its relevant advantages, up to now no specific CAE tools for SPIF were developed and the tool trajectory is generally defined utilizing CAD/CAM software developed for machining applications. In the paper an innovative monitoring and control approach, aimed to define and in-process update the most relevant process parameters during an industrial SPIF operation, is proposed. The strategy utilizes as monitoring variable the punch force trend: a set of preliminary tests demonstrated, in fact, its suitability as “spy variable” of the process mechanics and, in particular, of excessive sheet thinning and material failure approaching.     

Investigation into a new hybrid forming process: Incremental sheet forming combined with stretch forming

Asymmetric incremental sheet forming (AISF) is a process for the flexible production of sheet metal parts. In AISF, a part is obtained as the sum of localised plastic deformations induced by a simple forming tool that moves under CNC control. Three main problems exist in AISF: material thinning, geometric accuracy and the process duration. These limits restrict the range of applications of AISF. This paper focuses on a new hybrid process, the combination of AISF and stretch forming. First results are presented that show the positive impact of this hybrid process on the process limits.     

A Process/Machine coupling approach: Application to Robotized Incremental Sheet Forming

In this paper, a Process/Machine coupling approach applied to Robotized Incremental Sheet Forming (RISF) is presented. This approach consists in coupling a Finite Element Analysis (FEA) of the process with an elastic modelling of the robot structure to improve the geometrical accuracy of the formed part. The FEA, assuming a rigid machine, is used to evaluate the forces at the interface between the tool and the sheet during the forming stage. These forces are used as input data for the elastic model, to predict and correct the tool path deviations. In order to make the tool path correction more effective, the weight of three numerical and material parameters of the FEA on the predicted forces is investigated. Finally, the proposed method is validated by the comparison of the numerical and experimental tool paths and geometries obtained with or without correction of the tool path.     

金属板材数控渐进成形技术及加工轨迹坐标对位研究

金属板材数控渐进成形技术，是一种通过三轴数控成形机对金属板材进行逐层辗压而成形工件的柔性加工技术。本文探讨了金属板材数控渐进成形技术的过程、原理，同时，为了有效地排除成形过程中坐标对位对零件上出现的拉裂、材料堆积、材料硬化等现象的影响，本文提出了一种基于机器视觉的非接触式加工轨迹坐标对位方法，完成了金属板料数字化渐进成形中支撑模型的非接触式高精度快速定位。     

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。     

基于遗传算法的板料成形回弹工艺参数优化研究

研究了基于遗传算法的回弹优化模型的建立过程.以压边力和凸凹模间隙为优化变量,以板料变薄量为约束条件,以确定的回弹角度为目标函数,以DYNAFORM为目标函数求解器,建立了板料成形回弹控制的优化模型和优化系统.得到了满足工艺要求的压边力和凸凹模间隙,实现了板料成形过程的工艺参数优化,为板料成形工艺参数的优化提供了一个有效的途径.     

多弯角板料弯曲成形金属流动规律研究

以刚塑性有限元模型为基础,对典型的多弯角宽板零件弯曲用MSC／superform软件进行数值模拟,科学地分析了多弯角板料同时成形过程的金属流动规律,根据模拟得到的应力场、应变场、速度场及加载变化等,可以预测变形时产生的缺陷,为该类零件的成形工艺提供了理论依据。     

板材分段多点成形中局部剧烈塑性变形的研究

局部剧烈塑性变形是分段多点成形中特有的一种缺陷,对其进行深入的研究有利于分段多点成形技术的进一步实用化.本文以圆柱形工件为例,对分段多点成形过程进行数值模拟,详细分析了局部剧烈塑性变形的产生机理,并采用非均匀有理B样条曲面(NURBS)方法,进行过渡区的协调设计来抑制局部剧烈塑性变形的产生,实验证明这种方法能够显著提高工件的成形质量.     

板材成形中毛坯外形的逆向多步算法研究

毛坯外形的设计是金属板料成形的重要环节。针对板料拉深成形过程的特点，很多适用于毛坯形状计算的算法被提出，其中的逆向多步算法得到了一定的研究。本文着重对多步法的几种典型算法进行了综合讨论和分析，并指出研究中存在的问题以及未来研究的发展方向。     

车侧外板在曲压料面下的成形工艺有限元分析

以汽车侧外板为研究对象,采用有限元技术对曲压料面的冲压成形过程进行了工艺分析.以结果作为模具结构力学分析的边界条件,对模具零件进行了有限元的变形和强度校核.通过冲压工艺参数的调整,得到了较为合理的工艺方案和模具结构.     

板料成形数值模拟中网格节点编号优化

本文采用的有限元网格节点编号优化方法是基于归纳、演绎的方法,分析具有最优节点编号的三角形网格图,通过其特点,总结得出重新编号的原则,并按照这个原则,循环调整网格节点编号直到所形成的刚度矩阵带宽值满足给定收敛条件.结果表明,利用该方法对节点进行重新编号,简单易行,可得到较小的带宽值,节省了使用内存,提高了求解效率.     

钛板下颌假体的柔性化三维曲面展开与快速冲压成形工艺研究

针对现有定制化钛合金下颌假体的精铸加工周期长的问题。提出了一种快速冲压成形具有柔性化三维结构的钛板下颌假体的方法。以曲率变化大的颏部缺损为对象,结合有限元分析确定钛板下料的最佳初始结构和冲压加工过程的变形条件,研究该类下颌假体的冲压成形工艺性结构设计和分析方法。基于增材制造及其快速模具的树脂壳体／金属树脂填料冲压模具具有高效、低成本的特点;所完成的三维下颌假体表面质量良好,结构尺寸平均偏移量为0．5mm,证明柔性化结构的下颌假体可采用效率更高、成本更低的钣金冲压加工方法。提出了完整的冲压加工工艺路线．对下颌修复的实际应用具有一定的指导意义。     

电渣重熔34CrNi3Mo钢辊套的生产工艺研究

讨论了电渣重熔钢锭在生产辊套锻件时的优势 ,提出了对原工艺的改进方法。改进后的工艺减少了电渣钢辊套锻件的锻造火次 ,提高了锻件的成材率 ,降低了生产成本 ,取得较好的经济效益