An Incremental Roll Forming Process for Manufacturing Doubly Curved Sheets from General Quadrilateral Sheet Blanks with Enhanced Process Features

In order to manufacture a doubly curved sheet metal effectively, a flexible incremental roll forming process has been developed by adopting the advantages of the incremental forming process and the roll forming process by combining inherent flexibility of the incremental forming process and continuous deformation of the roll forming process. In the proposed roll forming system, a newly designed gripper system is attached in order to achieve automation and more precision manufacturing of the required sheet intended double curvature. The forming method has been further enhanced to form general quadrilateral blanks (including a square, a rectangle, a symmetrical trapezoid and an asymmetrical trapezoid, etc.) into doubly curved shapes by controlling the forming schedule developed by various experiments.     

Effects of temperature and blank holding force on biaxial forming behavior of aluminum sheet alloys

Biaxial forming behavior is investigated for three aluminum sheet alloys (Al 5182 containing 1% Mn (5182+Mn), Al 5754, and 6111-T4) using a heated die and punch in the warm forming temperature range of 200–350 °C. It is found that, while all three alloys exhibit significant improvement in their formability compared with that at room temperature, the non-heat-treatable alloys 5182 + Mn and 5754 give higher part depths than that of heat-treatable 6111-T4. The formability generally increases with decreasing BHP (BHP), but increasing the forming temperature and/or BHP minimizes the wrinkling tendency and improves the forming performance. The stretchability of the sheet alloys increase with increasing temperature and increasing BHP. For the alloys and forming conditions involved in the current study, the formability, measured in terms of part depth, comes mainly from the drawing of metal into the die cavity, although stretching effects do influence the overall forming behavior. The optimum formability is achieved by setting the die temperature 50 °C higher than the punch temperature to enhance the drawing component. Setting the die temperature higher than the punch temperature also improves the strain distribution in a part in such a manner that postpones necking and fracture by altering the location of greatest thinning.     

金属塑性成形过程的微观组织模拟与优化技术研究现状

介绍了金属塑性成形过程中微观组织演变的数学模型和常用的微观组织优化目标函数 ,给出了金属塑性成形微观组织模拟和优化的主要方法———微观遗传算法和灵敏度分析方法的基本原理 ,叙述了近年来国内外金属塑性成形微观组织模拟与优化研究概况。     

304不锈钢精铸件点缺陷的形成与控制

针对典型304不锈钢精密铸件内出现的黑色点缺陷,对其表面形貌、成分进行了分析,并在此基础上总结了缺陷的形成机制,确定了相应的防止措施。研究结果表明,铸件内的点缺陷可以划分为两类:一类具有不规则截面,为脱蜡过程中剩余腊料的燃烧残留物;另一类为熔炼过程中,由于脱氧剂和除渣剂的去除不彻底而引入的夹杂。通过优化脱蜡和熔炼工艺,使得铸件内的点缺陷得到了很好的控制。     

冷镦挤复合的连接成形工艺分析及模具设计

基于镦挤连接成形的金属塑性变形规律,分析了一次连接成形件的冷镦挤复合成形的形变特点和工艺特点,进行了冷镦挤一次连接成形工艺过程的可行性分析设计和模具设计,并得到了生产实践验证。     

冲压成形仿真过程中有限元网格模型的建立

网格模型对冲压成形模拟的精度和效率影响极大 ,文中阐述了有限元网格模型建立的方法 ,并从单元尺寸、单元类型、自适应网格再划分技术等方面论述了如何解决精度与效率的问题。     

刚塑性有限元模拟中体积变化问题处理方法

分析了在塑性有限元分析金属体积成形问题中引起体积变化的原因 ,指出在采用罚函数方法引入体积不可压缩条件的刚塑性有限元模拟中惩罚因子、增量步长、节点调整、网格密度和重划次数等是引起体积变化的主要原因。针对所分析原因 ,在现有的方法基础上提出基于三维有限元的节点调整和体积补偿新方法 ,并在实际模拟中应用 ,得到较好的效果 ,提高了模拟的精度和可信度。     

TC2M2δ.5钛板冷热翻边成形极限及非对称化研究

TC2Mδ2.5mm钛板室温圆孔翻边成形试验结果表明,除翻边底孔尺寸小于极限值时在唇口边缘发生破裂的正常失效方式之外,冷翻边卸载后制件还出现凸缘平面翘曲、翻边孔口部椭圆化、唇口边缘高度不一致、壁厚分布不均匀等非对称化现象。600℃高温热翻边成形可以有效地提高成形极限,并消除了凸缘平面翘曲和口部椭圆化,但口部高度差以及壁厚不均等非对称化现象依然存在。本文在给出极限翻边系数的同时,对这种非轴对称化程度进行了定量描述,并给出了理论上的分析与解释。     

板料成形中的新型可控压边力技术研究

板料成形中,压边力是控制板料流动的重要因素。前人大量的研究表明,在拉伸成形的不同行程施加合适的变压边力(VBHF),可有效避免板料成形中起皱和破裂的缺陷。文章基于压边力成形窗口的定义和分析,提出新的控制目标,并采用PID闭环控制策略来优化不同冲压行程中分块压边圈上的压边力。针对一个具有不同角部半径的盒型件进行了闭环的变压边力优化模拟,得到其不同位置的分块压边圈随行程变化的最优压边力曲线,并在变压边力压机上进行实验验证,结果表明,使用铝合金板料并在恒定压边力下难以成形的盒形件,在最优变压边力下成功成形。     

铝矾土陶瓷材料的试制

利用丰富的铝矾土原料在1350℃的烧成温度下试制出一种热稳定性极好的陶瓷材料。