An analysis for three-dimensional upset forging of elliptical disks

An upper-bound method is applied to determine the forging load and the deformed configurations during upset forging of elliptical disks. A simple kinematically admissible velocity field for three-dimensional deformation is presented which takes into account the lateral sidewise spread as well as the bulging along thickness. From the proposed velocity field the upper-bound load and the deformed configuration are determined by minimizing the total power consumption with respect to two chosen parameters. Experiments are carried out with annealed AISI 1015 steel billets at room temperature for different elliptical shapes and lubrication conditions. The theoretical predictions both in the forging load and the deformed configurations are in good agreement with the experimental results.     

平锻件坯料夹紧力的计算

根据锻件变形力大小选用的平锻机能否满足坯料夹紧力的要求，本文对此作了讨论。     

大型全纤维曲轴的镦锻成形工艺研究

本文通过DEFORM-3D对全纤维曲轴三步法的镦锻工艺进行了有限元模拟,并且分析了金属流动规律和变形分布情况。从而优化了其工艺过程和工艺参数,这些结果可以为生产试验提供理论依据。     

Predicting fracture in cold upset forging by finite element methods

Experiments dealing with the cold upset forging of metals have resulted in the determination of a forming limit in terms of the local compressive and tensile strains. As the specimen is compressed, a plot of the tensile strain versus the compressive strain can be made. Fracture occurs when the strain path intersects the forming limit. Once the fracture locus is defined by experimental methods, it is possible to use the Finite Element Method to determine if some cold forging operation will exhibit a free surface crack during a deformation process. This study demonstrates this procedure by using a simple upset forging of a cylinder that is simulated using ALPID 2.3. The local strains are then calculated by a computer program called STRAIN, which was written for this study. The computer generated curves are then compared to the experimental results and to a formula derived by J.J. Shah and H.A. Kuhn.     

管坯镦锻工艺仿真及优化

管坯镦锻制品是石油、钻探等机械设备的关键部件,要求具有很高的强度、抗拉性能及抗疲劳性能。在实际生产中,管坯成形过程很容易产生失稳、内部凹陷甚至折叠。而且坯料体积不易控制。使得锻件成形困难,锻件质量得不到保证。本文采用Deform-3D塑性有限元分析软件,以钻杆头部镦锻为例对管料的镦锻成形工艺过程进行了模拟和分析．并针对原有成形工艺中出现的问题进行了改进和优化。运用Deform-3D系统模拟的油管与生产实际基本吻合,因此,该模拟结果及其参数可用于钻杆头部镦锻模的设计。     

曲轴弯曲镦锻加中RR法和TR法的分析与比较

介绍了曲轴RR法和TR法两种弯曲镦锻的加工工艺,并从力学和速度两个方面比较了RR法与TR法。得出了TR法优于RR法的结论。     

Analysis of upset forging of cylindrical billets considering the dissimilar frictional conditions at two flat die surfaces

An upper-bound method is applied to the determination of forging load and deformed bulge profile during upset forging of cylindrical billets. A simple kinematically admissible velocity field which takes into account the dissimilar frictional conditions as well as the same frictional conditions at the top and bottom die surfaces is proposed for upset forging of cylindrical billets. From the proposed velocity field the upper-bound load and the deformed profile are determined by minimizing the total power consumption with respect to two chosen parameters. Experiments are carried out with annealed AISI 1015 steel billets at room temperature for several frictional conditions. The theoretical predictions both in the forging load and the deformed profile are in good agreement with the experimental results.     

大型全纤维曲轴平衡块成形塌角问题研究

针对曲轴锻造平衡块塌角问题,从加热、工艺、模具等不同的角度分析了锻造过程中可能出现缺陷的原因,阐述了NTR法的锻造工艺特点和相应的解决措施,并简单介绍了德国的“CATEAR”镦锻模具。通过实际生产验证了NTR法锻造的可行性和优越性,为全纤维曲轴的锻造提供了新的理论依据和实际经验。     

任意模具形状的金属三维体积成形过程刚塑性无网格RKPM分析方法

将无网格方法引入三维金属体积成形分析,在给出基于刚塑性流动理论的三维无网格再生核质点方法及其基本理论方程的基础上,为了提高分析系统的通用化和自动化,采用网格法来描述任意形状的三维模具型腔曲面,给出了三维无网格法数值模拟系统中动态接触边界自动处理的非线性接触算法,实现了任意模具形状的三维体积成形过程的无网格法数值模拟。对上模为半球形的三维立方体塑性变形过程进行了数值模拟,并与三维刚塑性有限元体积成形商品软件Deform3D的计算结果作了比较,验证了本文方法的正确性。     

应变速率矢量内积解三维锻压

将三维锻压的等效应变速率表示成二维的应变速率矢量,然后利用积分中值定理确定应变速率比值函数及该矢量的方向余弦,再对其内积进行逐项积分。将逐项积分结果求和,并得出三维锻压力的计算公式与鼓形测量公式的解析解,经纯铅锻压试验将锻压力的计算结果与实测结果比较表明,由该解析解计算的结果高于实测结果,优化后的误差缩小到不大于11.2%,说明此解仍属于上界解。     

直齿圆柱齿轮精锻成形工艺及三维有限元模拟

本文在齿轮分流锻造法的基础上 ,提出了闭式模锻———向内分流法两步成形的直齿圆柱齿轮的精锻工艺方案。采用三维刚塑性有限元法模拟了此工艺的成形过程 ,并且和传统的闭式模锻工艺进行了比较分析。从模拟结果可以看出 ,两步成形工艺不仅工作载荷低 ,而且齿形充填良好 ,是适用于直齿圆柱齿轮精锻的有效工艺方案。     

铝合金筋类零件锻造缺陷分析

针对铝合金筋类零件在锻造过程中产生的折叠、充不满、穿流等各种缺陷产生的原因进行分析.分析结果表明:过渡圆角的大小对折叠和穿筋有较大影响,增大圆角,可减小材料向筋部流动的阻力,改善材料的流动状态,避免折叠和穿筋;各工序间坯料截面面积的匹配也是导致缺陷的原因,合理的坯料截面面积应比该处终锻截面面积大5％～10％,面积太小容易导致充不满,太大又会出现穿流穿筋等缺陷;模具模膛的表面质量会影响材料的流动性能,导致锻件产生充不满和起皮等缺陷.     

Application of geometric midline yield criterion to analysis of three-dimensional forging

A kinematically admissible continuous velocity field was proposed for the analysis of three-dimensional forging. The linear yield criterion expressed by geometric midline of error triangle between Tresca and Twin shear stress yield loci on the π-plane, called GM yield criterion for short, was firstly applied to analysis of the velocity field for the forging. The analytical solution of the forging force with the effects of external zone and bulging parameter is obtained by strain rate inner product. Compression tests of pure lead are performed to compare the calculated results with the measured ones. The results show that the calculated total pressures are higher than the measured ones whilst the relative error is no more than 9.5%. It is implied that the velocity field is reasonable and the geometric midline yield criterion is available. The solution is still an upper-bound one.     

直齿圆柱齿轮精锻成形工艺改进及模拟分析

采用三维有限元方法,分析了中心分流法两步成形直齿圆柱齿轮精锻工艺。模拟了两种齿轮精锻工艺方案,通过对模拟结果的比较分析,得到了相对优化的工艺方案。结果可以看出,只在下模带凸台的工艺方案,使得上端部的齿形无法完全充满。改进后的工艺方案是,使上模带有与下模同样的凸台,从而更好地起到分流的作用,使得齿形充填良好。从本文实例中可以看出,有限元分析方法对提高锻造工艺设计水平具有显著作用。     

Analysis of ejection in precision forging

A theoretical model for predicting loads for ejecting precision forgings from a die, has been developed. This has been used to determine the effects of forging load, friction and die wall/workpiece interface contact area on ejection load of cylinders forged at room and elevated temperatures. Experimental results obtained for cold and warm forgings, compare well with theoretical predictions. At higher temperatures (above 800°C), neglect of oxidation and post forging thermal contraction in the theory makes it unable to predict results with sensible accuracy.     

锻造裂纹的分析与防治

介绍了锻造裂纹的主要试验研究方法:高温拉伸、热镦粗、热扭转、热弯曲和应变诱导裂纹,并结合裂纹附近微观组织和热力学理论探讨了多种材料锻件裂纹形成的原因。得出锻件裂纹不仅取决于材料本身的内因,而且与力学性能、组织结构、制件尺寸等因素有关。阐述了目前锻造裂纹的预防原则、内裂修复原理以及应用情况。     

曲轴TR锻造三维CAD／CAPP系统开发

针对曲轴TR锻造装置开发了一套CAD／CAPP系统。该系统能进行曲轴锻造工艺分析和锻模设计。系统以Visual Basic为开发工具,Solidworks为平台实现锻造工艺和模具的三维设计,CAD图纸输出,TR装置参数计算等功能,大大减少了曲轴锻造工艺设计阶段开发时间,提高了设计质量     

316LN不锈钢锻造开裂锻件组织与断口分析

针对核电主管道用钢316IN在锻造过程中开裂的现象,借助于金相显微镜(OA)、扫描电镜(SEM)以及能谱仪(EDS)对开裂锻件常温组织以及拉伸断口进行分析.结果表明:脆性氧化铝的大量存在加大了316LN在锻造过程中开裂的倾向.     

Analysis of void closure in open-die forging

Void closure studies have been conducted numerically and experimentally for open-die forging processes. The plane-strain FEM analysis was compared with bite forging experiments in order to determine how well the plane-strain approximation predicted the material flow in open-die forging. In addition physical modeling with plasticine was used to compare the measured and calculated deformation of the internal defect. The FEM analysis was in good agreement with the experimental results. Correlations for the computed effective strain and hydrostatic stress to the void closure were then calculated. Simulations of a solid cylinder side pressed with flat dies, V-shaped dies, and FML dies were done to determine the effectiveness of these dies at consolidating internal porosity based on the calculated strain and hydrostatic stress at the center of the billet. The V-shaped dies were found to be the most effective among those investigated. However, the press load for the V-shaped dies was also the highest.