中厚板挤压成形力影响因素研究

成形力作为中厚板体积成形工艺设计中的主要参数之一,是压力机选择和模具强度校核的重要依据.以体积成形有限元分析为基础,运用正交实验法,使用不同的工艺参数组合对中厚板凸台挤压成形过程进行数值模拟,结果显示在不同的成形阶段,变形程度、材料类型和初始板厚是影响成形力的显著因子.研究了变形程度、材料性能、坯料初始厚度对凸台挤压成形力的影响规律.研究结果为中厚板凸台挤压工艺及模具设计提供了一定的理论指导和参考.     

离合器式螺旋压力机挤压工艺的位置控制方法

分析了离合器式螺旋压力机挤压成形工艺中的力能关系 ,给出了成形过程中各参数的相互关系及其变化 ,提出了一种挤压成形工艺位置控制的计算方法     

基于数值模拟的铝合金四通管双向挤压精密成形工艺优化

针对四通管传统成形工艺的不足,提出一种铝合金四通管的双向挤压精密成形工艺。首先,根据铝合金四通管双向挤压精密成形工艺的原理,在三维软件SolidWorks中建立坯料和成形工具的三维模型,将其导入Deform-3D中建立数值模拟的有限元模型,进行初步模拟分析。然后,根据文献调研和初步模拟分析结果确定影响零件成形质量的主要因素为坯料温度、挤压速度和模具预热温度。采用正交试验方法对铝合金四通管双向挤压精密成形工艺进行试验设计,以坯料温度、挤压速度和模具预热温度作为试验因素,以最大等效应力和最大冲头载荷作为优化目标,利用Isight软件建立了响应面近似模型并求解得到铝合金四通管双向挤压精密成形最优的工艺参数组合为：坯料温度为374℃、挤压速度为5 mm·s^-1、模具预热温度为281℃。最后,采用优化的参数组合进行模拟验证,得到优化后的四通管零件无成形缺陷,且其最大等效应力和最大冲头载荷与多目标优化结果的误差小于3%。模拟结果表明,所提的四通管双向挤压精密成形工艺可行,可有效提高四通管的生产效率和材料利用率。     

模具工艺参数对多楔轧制高铁空心车轴力能参数影响

力能参数是有效控制多楔轧制高铁空心车轴的成形质量和设备设计的关键参数。为了研究模具工艺参数对多楔轧制高铁空心车轴力能参数的影响规律,采用DEFORM有限元软件,建立了楔横轧多楔同步轧制高铁空心车轴的三维刚塑性有限元模型;对轧制力和轧制力矩进行了理论计算;分析了展宽角、成形角、模具脱空等模具工艺参数对空心车轴力能参数的影响规律。结果表明:展宽角增大使力能参数增大;成形角增大也使力能参数增大;模具脱空能够显著改善轧件的受力状况。进行了1∶5多楔轧制空心车轴实验,实验轧制力矩与数值模拟结果相对误差均在10%以内,验证了有限元模型的正确性。     

材料常用流动应力模型研究

材料流动应力模型是金属成形数值模拟的重要参数之一。对于中厚板体积成形而言,经常规板料拉伸试验所得的流动应力范围达不到数值模拟的需要,对应大应变的流动应力一般借助外推模型进行估测。选用不同的外推模型使得中厚板体积成形数值计算所得的成形力存在较大的偏差,这种偏差会影响压力机的选择和模具强度的校核。基于中厚板材料的拉伸试验曲线结果,采用物理分析和数学推导相结合的方法研究了8种外推模型的拟合准确度、物理意义、硬化程度等因素。研究结果对中厚板体积成形数值模拟中材料流动应力模型的选择具有一定的理论指导。     

涂料在半固态钢挤压成形中的应用

在半固态钢挤压铸造成形过程中,主要由模具型腔表面涂层承受高温半固态钢浆料的热冲击,从而降低了浆料对模具的热损伤,提高了模具使用寿命。根据半固态钢挤压铸造涂料的工作环境和特点,通过大量试验对涂料配方、配比、制备工艺、涂敷工艺进行分析研究,确定了诸因素在半固态钢挤压铸造过程中的影响。     

液-固挤压复合材料过程模具传热特性研究

采用理论分析与试验研究相结合的方法,研究了液固挤压复合材料工艺过程的模具温度场,得到了模具温度沿径向和纵向随时间变化的曲线,分析了模具温度变化规律及其对成形过程的影响,模拟结果与试验结果吻合较好,说明所建模型的有效性,为优化模具设计和液-固挤压复合材料工艺的实际应用奠定了基础.     

活塞头挤压工艺模具设计与数值模拟优化

分析DFL350型活塞头的成形工艺，设计活塞头的温挤压模具。并以Deform-3D为平台，建立活塞头温挤压成形的三维塑性有限元模型，对其成形过程进行了数值模拟，主要分析温度、摩擦因子、拔模斜度以及型腔结构对成形力和模具充填情况的影响，优化成形工艺和模具结构，得出变形过程中挤压件破坏因子分布图和行程载荷曲线，给出了DFL350型活塞头的温挤压工艺参数的选择、模具设计以及设备选择。     

基于变形功法连续挤压成形过程温度模型

在连续挤压成形工艺过程中,变形温度是影响产品性能和工装模具寿命的关键因素。文章根据连续挤压的变形特征对成形过程进行分区分析,并基于能量平衡原理的变形方法,建立各区域的温度模型,构建了全过程温度预测模型,预测结果与数值模拟结果一致;以H62黄铜为工程实验材料,在连续挤压成形过程中,对挡料块和产品出口处进行温度测试。结果表明,温度模型预测值与实验测量值吻合良好。该温度模型可快速有效预测连续挤压成形过程中的温度分布,从而实现对产品性能及工装模具寿命的合理预测。     

神经网络在模具型腔温升预测中的应用

挤压成形过程中由于坯料和模具之间的滑动接触摩擦和坯料的塑性变形产生热而使模具型腔表面温度升高,加剧模具的磨损。采用热力耦合有限元法计算挤压成形过程中模具型腔表面的温升,将模拟结果与人工神经网络相结合,以有限元模拟结果作为学习样本,训练BP神经网络模型,以此模型预测模具型腔表面的温升。根据预测结果分析了挤压锥角、挤压速度和摩擦系数对型腔温升的影响,为进一步建立挤压成形过程中模具型腔表面的温升模型和磨损预测模型奠定了基础。     

板状带凸台件的精冲-挤压复合成形分析及工艺设计

总结了半冲孔型、挤压型和模锻型3种典型板状带凸台件的成形类型和特征,并以其中最具代表性的挤压型凸台作为研究对象,分析了板件挤压与正挤压在成形方面的区别,通过分析挤压型凸台成形过程中出现顶部凸起、底部缩孔、根部裂纹和外围凸包4种常见缺陷的原因,进一步提出了相应的解决措施。根据板件挤压凸台成形力的影响因素建立了计算板件挤压凸台成形力的经验公式。给出了在模具尺寸设计时,不同凸台相对高度下的挤压凸台底部孔直径的参考值;指出了凹孔直径即凸模直径越大,则成形力越大,对模具寿命不利。     

锥形凸台体积成形的一种合成力学模型

锥形凸台成形是金属体积成形工艺中一种典型的局部成形。该文通过分析锥形凸台在不同体积成形工艺中的成形机理,基于模块化思想,将其成形过程划分为挤压成形与角部充满两个特征时段,并将两个特征时段的滑移线场力学模型有机联结,构建了锥形凸台成形过程的一种滑移线力学模型,并介绍了应力场与变形力的求解方法。该模型丰富了金属体积成形过程的特征单元库,可套用于局部成形的应力场与变形力求解,实现局部成形的模具优化设计。     

The friction modeling of different tribological interfaces in extrusion process

Friction and lubrication are of great importance in many important metal forming processes such as sheet metal forming, forging and extrusion. With the products being more complex, it may utilize different lubrication medium in different tool/workpiece interface in which the metal flow could be controlled more effectively. While there is a substantial body of published research on friction modeling in metal forming processes, there has been relatively little work on forming process in which different tribological interfaces such as lubricant/grease, lubricant/dry and dry/grease are existed. The objective of this research is to investigate the friction distribution in combined forward and backward extrusion process. A realistic model of friction is developed to determine the friction coefficient of lubricated tool/workpiece interface. The friction coefficient of the other interface in which grease or different lubricant may applied is then determined by a coupled FEM and experiment investigation. Both the simulation and experimental data will be presented.     

多点成形中的柔性压边技术研究

对于薄板类零件而言,无论是利用整体模具成形还是多点成形,影响成形零件质量的关键因素是起皱。为了防止薄板类零件成形过程中产生起皱,尽量提高薄板类零件的变形量,研制了一种适合于多点成形的新型柔性压边装置,依据成形件的工艺特点、变形大小、材料特性及其弹性模量和成形零件形状,可以确定压边力的大小,且与板料直接接触的柔性压边圈随成形零件的形状不同而有所变形。介绍了多点成形压力机专用的柔性压边装置的工作原理、工作过程、布置结构、力学分析、成形力及压边力的计算。阐述了实际使用过程中的压边力和成形力的调节方法及柔性压边力,实现了数字无级调压,通过调节柔性压边力,明显改善了薄板类零件的成形质量。     

Experimental and numerical study on shaping of aluminum sheets with integrated piezoceramic fibers

Force-fit integration of piezoceramic fibers in micro-formed structures is a new approach for function integration in structural sheet metal parts. In a first step, a micro-structured surface is formed in a planar semi-finished sheet metal part by micro-impact extrusion. Piezoceramic fibers are then assembled into this micro-structured surface with a small assembly clearance. The fibers and the structured surface of the sheet metal are joined by a forming process. In the next step, the sheet metal with piezoceramic fibres within a locally micro-formed substructure is shaped by deep drawing into a 3D-geometry. In this paper, results of the micro-impact extrusion and the joining by forming experiments are presented. Furthermore, the design constraints for assembly and joining due to the dimensional and form deviations of the piezoceramic fibers are discussed. Results of a numerical study of micro-forming, joining by forming and the global loading during a deep drawing process step were in good agreement with the experimental investigations. The direct comparison between experiment and numerical simulation increases the process knowledge and shows further improvement potential.     

Process Design for Hybrid Sheet Metal Components

The global trends towards improving fuel efficiency and reducing CO_2 emissions are the key drivers for lightweight solutions. In sheet metal processing, this can be achieved by the use of materials with a supreme strength-toweight and stiffness-to-weight ratio. Besides monolithic materials such as high-strength or light metals, in particular metal–plastic composite sheets are able to provide outstanding mechanical properties. Thus, the adaption of conventional, wellestablished forming methods for the processing of hybrid sheet metals is a current challenge for the sheet metal working industry. In this work, the planning phase for a conventional sheet metal forming process is studied aiming at the forming of metal–plastic composite sheets. The single process steps like material characterization, FE analysis, tool design and development of robust process parameters are studied in detail and adapted to the specific properties of metal–plastic composites. In material characterization, the model of the hybrid laminate needs to represent not only the mechanical properties of the individual combined materials, but also needs to reflect the behaviour of the interface zone between them.Based on experience, there is a strong dependency on temperature as well as strain rate. While monolithic materials show a moderate anisotropic behaviour, loads on laminates in different directions generate different strain states and completely different failure modes. During the FE analysis, thermo-mechanic and thermo-dynamic effects influence the temperature distribution within tool and work pieces and subsequently the forming behaviour. During try out and production phase,those additional influencing factors are limiting the process window even more and therefore need to be considered for the design of a robust forming process. A roadmap for sheet metal forming adjusted to metal–plastic composites is presented in this paper.     

用模型元法建立变形力分布曲线

变形力分布曲线是用模型元法求解金属塑性成形问题的有力工具 ;而变形力分布曲线的建立又依据不同模型单元的力学模型。本文以开式模锻为例说明针对各式各样的体积成形过程建立变形力分布曲线的原理与方法 ;建立了开式模锻各个阶段的变形力分布曲线 ;综合考察了变形力分布曲线随变形过程的变化规律及特征 ;从而为变形力、变形功与节省材料的角度优化设计体积成形工艺及模具找到了有效途经 ;并以实验证明用模型元法建立变形力分布曲线的有效性与实用性。     

枝叉管形锻件的剪—挤变形规律模拟实验研究

给出枝叉管形锻件剪－挤变形工艺的理论基础及其工艺性要求。通过物理模拟实验得出一种枝叉管形件－－截止阀体锻件的剪－挤变形关键工艺参数（即成形条件）;通过网格试验研究分析了枝叉管形件剪－挤工艺过程的金属流动情况及其变形规律;由剪－挤和镦－挤成形枝叉管形件的挤压力对比模拟实验,得出剪－挤成形过程挤压力降低规律,并验证了该工艺节能省力的特点。结果表明,利用剪－挤成形新技术可以在千吨级中型锻造设备上开发大型枝叉管形锻件的成形工艺。