Analysis of three-dimensional upset forging of arbitrarily-shaped prismatic blocks

The present study is concerned with upset forging of arbitrarily-shaped prismatic blocks which is characterized by three-dimensional deformation with sidewise spread and bulging along thickness. A kinematically admissible velocity field to incorporate the three-dimensional deformation is proposed. From the proposed velocity field the upper-bound load and the deformed configuration are determined by minimizing the total power consumption with respect to some chosen parameters. Experiments are carried out with annealed AISI 1015 steel billets and commercially pure copper billets at room temperature for different frictional conditions and geometrical shapes such as clover and rounded rectangles. The theoretical predictions both in the forging load and the deformed configuration are shown to be in good agreement with the experimental results. Therefore, the proposed method of analysis in this work can be used for the prediction of forging load and deformation in upset forging of arbitrarily-shaped prismatic blocks.     

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。     

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。     

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。     

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。     

An analysis of the forging of spur gear forms

Forging spur gear forms in completely closed cavity dies is investigated by means of an upper bound analysis. A velocity field comprising three unit deformation regions is proposed. The tooth regions are approximated by prismatic rectangular sections. The effects of root diameter, number of teeth and workpiece/die interface friction, on flow and forging pressures, are determined.Forging pressure without friction is independent of root diameter but increases with the number of teeth. In the presence of friction forging pressure increases with reducing root diameter.     

高碳钢盘条电阻对焊失效分析

高碳钢盘条焊接区质量是影响高应力钢绞线生产效尺寸较大及材料成分不一致等,常在焊接区发生断丝现象.通过对大量的拉丝及绞线时的断裂试样进行分类、统计,并结合实际工况条件,对试样的断口形貌、微观组织进行了分析.结果表明:焊接区在拉丝工序中引起的断裂占64.1%,在绞线工序中引起的断裂占35.9%.引起焊接断裂的主要原因是焊缝处的夹杂及氧化物、焊接热影响区的过热组织及网状渗碳体、及拉丝过程中的表面形变硬化.阐明了焊接质量主要受焊接工艺、焊后热处理、去疤后的表面润滑影响.     

截齿锻件冷锻成形工艺分析

根据截齿锻件的形状特点,制定其冷锻成形工艺方案,即制坯、预成形与终锻成形。采用镦粗预成形时,易发生局部失稳现象,无法获得合格的截齿锻件。针对该问题,提出正挤预成形的改进工艺方案,并进行三维有限元模拟,模拟结果表明改进方案合理可行。在此基础上,设计出截齿锻件模具实现了截齿锻件的批量生产。     

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。     

Upper-Bound Elemental Technique (UBET) with convex circular parallelepiped and convex spherical elements for three-dimensional forging analysis

In this study, two kinematically admissible velocity fields are derived for the proposed three-dimensional convex circular parallelepiped and convex spherical UBET elements. Those elements are applied to three-dimensional closed-die forging having convex curve surfaces; the capability of the proposed elements is then demonstrated. From the derived velocity fields, the upper-bound loads on the upper die and the velocity field are determined by minimizing the total energy consumption with respect to some chosen parameters. Also, experiments of two closed-die forgings are performed with commercial pure lead billets at the ambient temperature. The theoretical predictions of the forming load correlated well with the experimental results. The results in this study confirm that the elements proposed in this work can effectively be used to predict the forming load accurately in three-dimensional closed-die forging with convex curve surfaces.     

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.     

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     

C92K-125全液压模锻锤锻打工况多体动力学分析

为了解决全液压模锻锤在锻造过程中出现的振动、冲击现象以及U型机身上多个部位易出现裂纹等问题,首先建立了C92K-125型模锻锤三维几何模型;添加了运动副和主运动,进行了运动学模拟、干涉碰撞检查和机构运动的合理性分析;参照几何模型并针对模锻锤的实际锻打工况,建立了全部由六面体网格组成的模锻锤包括工件的非线性多体有限元模型,并提交LS-DYNA求解,得到了打击过程中主要部件锤杆和机身上应变、应力的变化情况,为液压模锻锤的结构优化设计和打击过程中的能量、温度精确控制提供了依据.     

热锻模具的优化设计方法

从分析工程实际中热锻模具的失效形式入手,建立了一种考虑主要失效形式的串联模型,根据材料的最优利用原则,推导出适用于热锻模具的优化设计方法,该方法对工程实际有一定指导意义