The forging of helical gears (I): Experiments and upper-bound analysis

In this paper, the forging of helical gears has been investigated. A punch and a die are tooth-shaped for the guiding type forging of helical gears. The punch compresses a cylindrical billet placed in a die insert. As a consequence the material of a billet flows into the tooth region. The forging has been analysed by using the upper-bound method. Kinematically admissible velocity fields have been developed, where an involute curve has been introduced to represent tooth profile of the gear. Numerical calculations have been carried out to investigate the effects of various parameters, such as modules, numbers of teeth, helix angles and friction factors on the forging of helical gears. Some forging experiments were carried out with commercial aluminium alloy to show the validity of the analysis. Good agreements were found between the predicted values of the forging load and those obtained from the experimental results.     

The forging of helical gears (II): comparisons of the forging processes

In this study, the forging processes of helical gears have been investigated wherein they have been classified into two types: the guiding type and the clamping types. These two types of forgings of helical gears have been analyzed by using the upper-bound method. New kinematically admissible velocity fields of the clamping-type forging of helical gears have been proposed, where an involute curve has been introduced to represent the tooth profile of the gear. The proposed velocity fields of the clamping-type forging of helical gears have been applied to the non-symmetric lateral extrusion forging and the result has been compared with the solution proposed by Plancak et al. [J. Mater. Process. Technol. 1992; 34:465–472]. Numerical calculations have been carried out to investigate the effects of various parameters, such as modules, number of teeth, helix angles and friction factors on the clamping-type forging of helical gears. For the forging of helical gears, the results of the upper-bound analysis of the clamping type have been compared with those of the guiding ones. Some experiments of the clamping-type forging were carried out with commercial aluminum alloy to show the validity of the analysis. Good agreement was found between the predicted values of the forging load and the experimental forging load.     

直齿圆柱齿轮冷精锻实用化工艺研究

以实用化为目标,对１５＾＃钢、４５＾＃钢、２０ＣｒＭｎＴｉ直齿圆柱齿轮冷精锻工艺进行系统研究,提出了闭式镦挤－约束孔分流两步成形实用化工艺方案和基于变位理论和齿形模修正设计方法。     

直齿轮精锻成形新工艺及试验研究

与精锻成形工艺相比,传统的切削加工方法加工直齿轮具有诸多弊端。而当前提出的闭式镦挤成形工艺载 荷过大,严重制约着精密成形直齿轮工艺的实用化。提出采用预锻分流区一分流终锻新工艺精密成形直齿圆柱齿 轮,设计了能够进行多种组合的精锻成形试验模具,并对空心管坯和实心圆柱坯进行了传统的闭式镦挤和新的分 流成形工艺试验,试验结果表明:与传统的闭式镦挤和现有的圆柱直齿轮成形工艺对比,提出的成形工艺工序简 单,终锻后齿形充填饱满,端面平整,而且成形载荷降低了37％以上,具有生产实用化的前景。     

A Study on the Extrusion by a two-step process for manufacturing helical gear

Much research has been carried out in the manufacturing of helical gears by cold forging or by extrusion. Although cold forging is applied to some bevel, spur, and helical gears, problems in connection with the reduction forming load and tool life still make it difficult for these methods to be commercialized. In this study, focusing on reducing a load in forming helical gears, the extrusion of helical gears by two-step process is proposed. This process is composed primarily of extruding a billet to a spur gear and then twisting the previous spur gear extruded to a helical gear. Cylindrical billets of Cr-Mo steel(SCM 415) and aluminium alloy(Al60 series) were used as specimen materials for the experiments. The maximum loads obtained by upper-bound analysis and FEM are compared with the results of experiments. The loads of the analysis have good agreements with those of the experiment. The newly proposed method can be used as an advanced technique that remarkably reduces the forming load and replaces the conventional forming.     

齿轮冷精锻工艺预锻模具齿形优化设计

在直齿圆柱齿轮两步成形冷精锻工艺中 ,预锻模具齿形设计对改善材料填充性能 ,降低成形载荷具有重要意义。本文采用正交试验法与数值模拟技术相结合的方法 ,来解决预锻模具型腔优化设计问题。选取了描述预锻模具几何形状的 3个参数作为影响因素 ,以预锻终锻总载荷值为指标 ,通过有限元模拟分析来获得虚拟试验结果 ,最终确定预锻模具型腔几何形状参数的最佳值 ,为提高齿轮精锻成形质量提供有效依据。     

DESIGN AND MANUFACTURE OF STRAIGHT BEVEL GEAR FOR PRECISION FORGING DIE BY DIRECT MILLING

In the manufacture of straight bevel gears, a precision forging method has been mainly used in recent years and the precision forging die has been usually manufactured using electric discharge machining. However, it is difficult to content the high productivity and low manufacturing cost using electric discharge machining because the gears are produced through a process of several steps. In this article, a design and manufacture of a straight bevel gear for a precision forging die by direct milling is developed in order to improve the productivity and manufacturing cost for the gear production. The tooth profile of a straight bevel gear generated by a quasi-complementary crown gear instead of a usual complementary crown gear is introduced. For this study, first the numerical coordinates on the tooth surface of the straight bevel gear were calculated and the tooth profiles were modeled using a 3D-CAD system. Afterward, the direct milling of the precision forging die of the straight bevel gear in the hardened state was carried out using a CNC milling machine based on a CAM process through the calculated numerical coordinates.     

直齿圆柱齿轮精锻成形过程数值模拟及参数分析

采用三维有限元数值模拟方法分析了直齿圆柱齿轮的精锻成形过程，选择模拟表面单元数、加载步长、模数、齿数、齿轮高度等参数进行了多次模拟分析，根据模拟结果对比分析了以上诸参数对成形工艺的影响。确定了适宜的表面单元数目和加载步长值，较好地满足了模拟的需要。从数值模拟结果分析可知，在齿轮其他参数不变的情况下，锻造载荷随模数和齿数的增加而增加，模数的变化对载荷的影响显著；在对高度不同的齿轮成形过程的模拟分析中发现，在成形的初始阶段，高度越小载荷越大，在填充终了阶段，随高度增加载荷稍有增加。     

齿轮的冷挤压成形技术研究进展

随着汽车生产的大规模化,高效率、高质量、低污染、低成本的齿轮冷挤压制造技术越来越受到国内外学者和专家的关注,有限元分析和上限法等理论依据越来越多地被应用到齿轮冷挤压成形的工艺改进,闭式冷精锻和分流冷挤压成为直锥齿轮和圆柱直齿轮大批量生产的关键工艺。从理论研究和工艺研究两方面论述了汽车齿轮的冷挤压成形技术研究现状,并对其发展进行了讨论。     

矿用减速器啮合直齿轮有限元分析及优化

利用SolidWorks软件对矿用减速器啮合直齿轮进行三维建模,并运用SolidWorks中的Simulation分析软件,对一对啮合的直齿轮进行静力分析,在此基础上,以齿宽为变量,以质量最小为目标,对大齿轮的齿宽参数进行优化设计,并通过Matlab编程,得出了大齿轮的齿宽最优值,为齿轮的设计提供了参考。     

双联齿轮精锻成形工艺及数值模拟分析

针对双联齿轮的结构特点,提出了两种双联齿轮成形工艺,设计了坯料的合理形状,建立了三维有限元分析模型。通过工艺分析和不同工艺条件下的材料流动过程三维有限元动态仿真,研究了变形全过程的材料塑性变形行为、流动规律、几何尺寸变化以及成形件几何质量和缺陷等。对比有限元模拟结果发现:闭式模锻工艺齿形填充较差,产生折叠缺陷或充不满现象;挤压成形工艺齿形填充良好,是双联齿轮精锻成形的优选方案。研究结果为双联齿轮成形工艺实用化研究提供了理论指导或技术支持。     

A study on precision forging of spur gear forms and spline by the upper bound method

Precision forging is an important manufacturing procedure of spline and spur gear forms. It has advantages of improved strength, good tolerance, saving billet material, dispensing with the cutting, etc. In this paper, a mathematical model using an upper bound method is proposed for forging of spur gear forms and spline to investigate the plastic deformation behavior of billet within the die cavity. The material of solid billet was assumed as rigid–plastic and the shape of the tooth profile was accounted for the mathematical modeling of the kinematically admissible velocity field assumed for the plastic zone. The non-uniform velocity was employed for simulating the inhomogeneous deformation and the effect of barreling during the forging. Using the present model, various effects of forming parameter such as the friction factor, reduction, number of teeth, etc. upon the non-dimensional forging pressure, forging force and barreling of the spur gear forms and spline were analyzed systematically and the results compared with those of other researcher's analytical and experimental work. It is shown that the present modeling of the process improves knowledge of the process design performance for the precision forging of spur gear form and spline.     

Analysis and Optimization on Factors Affecting Forming Quality of Half Axle Gears Warm Precision Forging

Half axle gears is produced by precision forging popularly because of the advantages in minimum machining allowances, lower material consumption and good service properties. But the forming quality of precision forging is difficult to control. Many simulations and analysis of precision forging process were taken by previous researchers. But no concrete method is proposed to evaluate and optimize the forming quality of half axel gears. The primary purpose of this work is improving the forming quality of half axel gears by analyzing and optimizing the affected factors of forming quality. The enclosed-die warm forging process of half axle gears was developed, and a new type of die-set used on double action hydraulic press was brought forward. The main influential factors of precision forming quality were analyzed after the forming process had been simulated by using finite element method(FEM). These factors include die structure, web thickness and web position. A method used to evaluate the forming quality was established, which investigated the maximal forming load, the metal filling rate and the material damage factor. The FEM simulations of half axle gears precision forging were evaluated by this method. The results show that the best forming quality can be achieved when the punches were added with bosses, the web located at the middle plant of the gear, and the web thickness was 30 percent of the inner hole diameter. Verification experiments taking the above optimized parameters were performed on a 7.8 MN double action hydraulic press. The trial products were formed well. And their geometric precision meets the demand. The verification result shows that the optimization of the influential factors, according to the simulations and the evaluation method, can improve the forming quality. The new structure of precision forging die-set and the new evaluation method guarantee a high forming quality of half axel gears.     

Experimental studies on the effects of reduction in gear tooth stiffness and lubricant film thickness in a spur geared system

Gears are one of the most common mechanisms for transmitting power and motion and their usage can be found in numerous applications. Studies on gear teeth contacts have been considered as one of the most complicated applications in tribology. Depending on the application, the speed and load conditions of teeth may change triggering several types of failures on teeth surface such as wear, scuffing, micro-pitting and pitting. The above-mentioned faults influence changes in vibration and acoustic signals, due to changes in operating conditions such as increase in temperature and decrease in lubricant film thickness and specific film thickness. These abnormal changes result in cumulative effects on localised or distributed faults on load bearing surfaces of gears. Such damages cause reduction in tooth stiffness and severity of damage can be assessed by evaluating the same using vibration-based signals.This paper presents the results of experimental investigations carried out to assess wear in spur gears of back-to-back gearbox under accelerated test conditions. The studies considered the estimation of operating conditions such as film thickness and their effects on the fault growth on teeth surface. Modal testing experiments have been carried out on the same gear starting from healthy to worn out conditions to quantify wear damage. The results provide a good understanding of dependent roles of gearbox operating conditions and vibration parameters as measures for effective assessment of wear in spur gears.     

纳米Si2N2O-Sialon陶瓷齿轮超塑性锻造研究

采用Deform有限元软件对纳米Si2N2O-Sialon陶瓷超塑性锻造成形过程进行模拟,较直观地预测了齿轮成形过程中齿形充填情况。在1550℃,纳米Si2N2O-Sialon陶瓷显示出良好的超塑性成形性能,通过试验,超塑性锻造成形出了质量良好的齿轮零件。在模拟与试验的基础上,通过与金属齿轮的齿形充填情况进行对比,建立了陶瓷齿轮齿形充填模型,得到了纳米陶瓷齿轮超塑性锻造成形的基本规律:陶瓷齿轮锻造过程中齿形充填过程分为5个基本阶段,与金属齿轮锻造成形充填过程相比,齿形前端的鼓形量和齿形侧面的鼓形量明显较小。     

Influence of Oil Viscosity,Chemical Oil Structure,and Chemical Additives on Friction Loss of Spur Gears (Concerning the Influence of Synthetic Oil and Mineral Oil)

The friction loss of gears and its quantitative estimation are important problems because of their relevance to energy conservation and load-carrying capacity. Recent research results do not provide satisfactory estimates of friction loss of spur gears. Therefore, the authors carried out experiments to study the influences of lubricating oil viscosity and additives, as well as base oil type and load and rotational speed on friction loss of spur gears. Base oil types used were paraffin mineral, poly-α-olefin, and polyglycol with several oil viscosities. An EP and a mild EP additive were studied in these oils. Finally, the temperature rise of teeth of gears as a function of friction power loss was investigated, and an empirical formula for calculating the temperature rise of the spur gear teeth was derived.     

闭式冷挤锻工艺在汽车齿轮生产中的应用

阐述了直齿锥齿轮热精锻生产技术的现状，并就热精锻齿轮的品质和市场问题，提出了汽车直齿锥齿轮冷挤锻生产的必要性；介绍了工厂改造设计中采用的闭式冷挤锻生产工艺和生产设备、改造设计后的产品品质和经济效果，以及采用闭式冷挤锻工艺进行大批量生产所存在的问题和解决途径。     

锻压温度对新型汽车差速器齿轮性能的影响

采用不同的始锻温度和终锻温度对新型汽车差速器齿轮用20CrMnTiVSr试样进行了锻压成型试验,并进行了磨损性能和冲击性能的测试与分析。结果表明:随始锻温度和终锻温度的升高,新型汽车差速器齿轮用20CrMnTiVSr试样的磨损体积先减小后增大,冲击吸收功先增大后减小,耐磨损性能和冲击性能先提升后下降。与1160℃始锻相比,1220℃始锻温度下试样的磨损体积减小了44.44%,冲击吸收功增大了20%;与760℃终锻相比,820℃终锻温度下试样的磨损体积减小了47.37%,冲击吸收功增大了24.53%。新型汽车差速器齿轮用20CrMnTiVSr试样的锻压工艺参数优选为:1220℃始锻温度、820℃终锻温度。     

基于ANSYS/LS-DYNA的齿轮动力学接触仿真分析

针对渐开线直齿轮容易出现的载荷突变及噪声问题,需对齿轮进行齿廓方向的磨削修形。利用ANSYS/LS-DYNA中的APDL语句实现标准齿轮和修形齿轮的建模及动力学接触分析,并对分析结果进行比较,验证其修形的必要性。     

基于有限元的锻件变形力优化设计

以降低锻件变形力为优化设计目标,采用刚粘塑性有限元法,对锻造预成形优化设计进行了研究。给出了优化设计的目标函数,确定了优化设计的设计变量和优化设计方法,采用FORTRAN语言编制了相应的优化设计程序,并对一典型的轴对称H形锻件进行了优化设计,给出了优化设计的结果。结果表明,经过优化,锻件的变形力明显降低。