轴对称锻造过程金属流动规律的有限元模拟

本文介绍刚塑性、刚-粘塑性有限元法的基本理论;探讨应用有限元方法模拟金属流动规律时所遇到的具体处理技术、算法及其软件实施;分析轴对称锻造过程的金属流动规律。     

单工序少无毛边锻造过程预制坯形状优化设计

针对单工锻造在终锻之前一般都需要以镦粗进行预制坯的实际情况，通过刚粘塑性有限元法，以实际锻件超出预定值线部分的体积为目标函数，以镦粗的压下量为优化设计变量，采用黄金分割法对其预制坯工艺化设计进行了研究。并对一轴对称锻件的镦粗压下量进行了优化设计，优化取得了明显的效果。     

模锻过程金属流动的数值模拟

本文简述了应用UBET研究模锻过程金属流动规律的模拟方法,对轴对称高凸台锻件模锻过程的金属充填高度和流动状态进行了仿真模拟,并且分析了飞边参数、摩擦因子、凸台直径等模锻参数的变化对轴对称高凸台锻件模锻过程中金属流动的影响。实践表明,UBET用于模拟模锻过程的金属流动规律是可行的。     

带预制孔筒形件拉深成形金属流动规律的研究

根据带预制孔筒形件成形后侧壁上获得矩形孔的工艺特点及要求,设计了预制孔初始形状为扇形的坯料,采用理论分析和运用ETA/Dyanform软件进行数值模拟实验,深入分析其在拉深过程中的金属变形流动行为的力学机理,分析不同摩擦系数和压边力对金属流动规律的影响.结果表明:预制孔的存在破坏了坯料的完整性,使得孔周围材料的流动发生...     

空调联箱多通管内高压成形金属流动规律研究

以空调联箱多通管件为研究目标,运用有限元模拟方法对金属材料的变形过程进行模拟分析.通过分析工件壁厚的分布规律和典型节点的位移规律,由此揭示成形过程的金属流动的一般规律.结果表明:端部补料区金属沿水平方向流动较明显,成形区金属沿支管方向流动较明显,支管问的金属流动量很小,这些规律为成形工艺的选择提供了参考依据.     

内螺纹冷挤压成形过程中金属流动行为研究

通过研究内螺纹的冷挤压成形过程,利用数值模拟仿真技术获得挤压成形过程的速度场分布,并通过试验方法验证了内螺纹冷挤压成形过程的金属流动规律。结果表明,内螺纹冷挤压过程中牙顶处金属受力最小,牙底部分受到丝锥的压力最大,同时也使得晶粒细化程度有所不同。     

预制孔形状对摩擦叠焊单元成形影响的数值分析

对两种预制孔形状的摩擦叠焊单元成形过程进行数值仿真分析,得到完整的包含大变形塑性变形的焊接过程结果。分析得到,由于圆锥形预制孔在焊接过程中接触面压力均匀,而圆柱形预制孔在塑性材料与侧壁接触面上没有压力,所以圆锥形预制孔得到的温度场与应力场较圆柱形预制孔分布均匀,从而影响焊接接头的结合强度。通过拉伸试验与仿真结果进行对比,结果吻合。     

金属成形的三维有限元模拟系统的发展与展望

总结了国外有关金属三维成形有限元模拟的研究现状以及相关的关键技术即单元类型问题、矩阵求解格式问题、自动网格生成、输入数据和输出结果的图形可视化等重要问题。指出三维成形有限元模拟在工业设计生产中具有广泛的应用前景。     

锻造毛坯形状优化设计的研究

近几年来，锻造形状优化得到了众多学的关注。本对单工序锻造问题的毛坯形状优化进行了研究。以毛坯高径比为优化设计变量，目标函数取为实际锻件超出预定理想直线部分的体积，以黄金分割法进行优化迭代，给出了目标函数的表示方法及计算表达式。并对一典型的轴对称H型锻件的毛坯形状进行了优化设计，取得了明显的效果。     

某输送机刮板模锻成形工艺数值模拟研究

以某输送机刮板为研究对象,建立有限元模型,分析该锻件成形过程中的零件温度场、模具温度场以及成形载荷等因素的影响,并应用Archard磨损模型分析了模具复杂多因素耦合情况下的磨损情况,预测了单次磨损的深度分布,并得出单次磨损最大深度0.00510mm,为优化模具设计、提高模具寿命提供了理论依据。     

基于锻坯的大型外凹形截面环件成形研究

针对大型外凹槽型环件成形上的困难,根据异形截面的环锻件毛坯尺寸设计三大原则和方法,设计出合理的锻坯尺寸及形状,进一步设计出比较合理的模具。并基于SIMUFACT软件建立了径轴向轧环机三维数值仿真模型,对大型异形环件一个生产周期内的环件轧制过程进行了数值模拟,揭示了环件热辗扩过程中等效应变场、温度场、辗扩力以及金属流动特性的规律。仿真计算结果表明,采用计算机模拟环件的成形过程,可用于模具改造、锻坯设计以及轧制工艺的优化,建立起一种大型外凹槽截面环件稳定轧制模型。     

Understanding of the shape-controlled synthesis of strip shape diamond under high pressure and high temperature conditions

We present the shape-controlled synthesis of strip shape diamond with stretched crystal faces along {100} or {111} direction and larger length-to-radius ratio than the conventional diamond in the designed NiFe-C system at high pressures and high temperatures (HPHT). A series of synthetic experimental results on the strip shape diamonds were obtained at different pressures and temperatures. Under the constant pressure condition, the morphology of the strip shape diamond varied with the increase of temperature obviously. Fourier transform infrared (FTIR) micro spectroscopy and Raman spectroscopy revealed that the various locations of crystal face have different nitrogen impurity concentration, and internal strain and defects in these strip shape crystals. According to these results, it can be concluded that the difference of growth rates at various crystal faces results in different crystal morphologies. Based on the growth characteristics, we suggest that composition segregation of the metal film around the growing crystal induces the formation of strip shape diamond.     

压弯成形中回弹问题的研究

介绍了在压弯成形过程中所实现的数值模拟技术。整个系统能以数据与图像结合的形式动态地显示出压弯过程的发展及其内部诸因素对压弯过程的影响,并在最终考虑回弹补偿的情况下,完成对压弯过程的数控。     

Finite element analysis of a multi-stage axisymmetric forging process having a spring-attached die for controlling metal flow lines

In this paper, a computer simulation technique for the forging process having a spring-attached die is presented. A penalty rigid-viscoplastic finite element method is employed together with an iterative force-balancing method, in which convergence is achieved when the forming load and the spring reaction force are in equilibrium within the user-specified allowable accuracy. The force balancing is controlled by adjusting the velocity of the spring-attached die. To minimize the number of iterations, a velocity estimating scheme is proposed. Two application examples found in the related company are given in order to emphasize the significance of metal flow lines for quality control and to investigate the effects of spring-attached dies on the metal flow lines as well as the decrease in forming load.     

Quantification of uncertainties in grain size predictions of a microstructure-based flow stress model and application to gear wheel forging

For reliable process design, full knowledge of the possible spread of the predicted target values such as grain size is desirable. In real production the spread of final product properties is caused by uncertainties in the processing conditions and the material behavior. This paper proposes a strategy which allows for incorporating the material behaviors uncertainties in a microstructure model. This model is applied to the design of a hot-forging process. It is shown that the probability distribution of the grain size value is asymmetric and predicts occurrences of grain sizes with a large deviation from the most probable grain size.     

Thermal and flow modelling of ladling and injection in high pressure die casting process

Air entrapment and premature solidification in the shot sleeve of the cold chamber high pressure die casting process are problems affecting the casting quality. These issues are addressed from several viewpoints, including heat loss during metal ladling, turbulence generation and gas escape during pouring, wave formation and propagation during metal pouring and injection, and heat loss and solid creation in the shot sleeve during metal injection. Measurements and simulations have been conducted for a typical industrial case where the fill ratio of the shot sleeve is about 30%. It has been found that the settling time of the aluminium alloy in the shot sleeve has a profound influence on the air entrapment. The settling time also has a negative effect on the metal quality the solid formation (premature solidification or cold flakes) in the shot sleeve. Fast pouring and quick injection (no settling time) are recommended as a good approach to minimise the air entrapment and cold flakes in the shot sleeve in this particular case. IJCMR/474     

锻压设备对热锻模型腔近表层负荷的影响

本文选取三类典型锻压设备,运用有限元分析软件对汽车前轮毂终锻模锻造过程进行数值模拟,分析不同加载方式对热锻模损伤的影响程度.研究表明:合理选择锻造设备可以降低锻模负荷,提高锻模使用寿命.     

支重轮半体模锻工艺研究

利用塑性成形软件,在对某种履带式挖掘机支重轮半体的成形过程和变形抗力进行数值模拟基础上,确定产品工艺方案.通过批量生产实践表明,该工艺方案及模具设计科学合理,对相似结构产品工艺研发设计具有一定参考价值.