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。     

Thixo forging process of wrought aluminum alloy fabricated by rotational helical shape stirrer

The manufacture of rheology materials from wrought and casting aluminum alloys using controlling solid fraction and crystal grain is demonstrated in this paper. The equipment to form the rheology material was designed so that shear force and applied pressure could be carefully and simultaneously applied using a mechanical stirrer. The problems caused by using this method with the thixo forging process were studied by investigating the mechanical properties of a sample that had a controlled solid fraction of 45–50 %.     

Analysis of the drop forging of a piston using Slip-Line Fields and FEM

The paper analyses the process of a forging piston-type product. The Finite Element Method (FEM) is used to determine the forging loads and the kinematics of metal flow during the press forming process analysed. The Slip-Line Field Method (SLFM) is used to obtain a simplified solution. This helps to determine the distribution of material-tool contact pressures which is the basis for computing the forging load. The results from both methods were verified experimentally and good agreement was obtained. In addition a comparison is made between the forging load values obtained in the present study and those given by selected equations from the literature.     

Rheological forging process of A6061 wrought aluminum alloy with controlled liquid fraction by electromagnetic stirring system

A rheological forging process to fabricate engineering components of A6061 wrought aluminum alloy with a controlled liquid fraction has been proposed and mechanical properties of the products characterized. The process uses a medium pressure of below 45 MPa and electromagnetic stirring (EMS). The processing parameters such as injection velocity, injection pressure, and stirring time were optimized to obtain improved mechanical properties. It was also possible to determine injection time and stirring time by measuring the temperature of molten metal in the sleeve. After the products were manufactured by using EMS, their microstructure and mechanical properties were investigated by image analysis, comparing to parts produced without EMS. Those products fabricated by EMS had better mechanical properties and had over 20% higher globular microstructures than those fabricated without EMS.     

Determination of the friction factor of Ti-6Al-4V titanium alloy in hot forging by means of ring-compression test using FEM

The friction factor of Ti-6Al-4V titanium alloy under hot forging situation was determined by the combined approach of ring-compression tests and finite element (FE) simulations. It is noticed in particular that the heat-transfer (HT) coefficient has significant effects on the metal flow and calibration curves, thereby affects the measurement of interfacial friction factor. Moreover, the HT coefficients are different for glass lubricant and dry friction conditions. Therefore, different HT coefficients should be employed to generate the calibration curves when both of the lubricant conditions were applied for determining the interfacial friction coefficients in hot ring-compression of Ti-6Al-4V titanium alloy.     

Determination of the friction factor of Ti-6Al-4V titanium alloy in hot forging by means of ring-compression test using FEM

The friction factor of Ti-6Al-4V titanium alloy under hot forging situation was determined by the combined approach of ring-compression tests and finite element (FE) simulations. It is noticed in particular that the heat-transfer (HT) coefficient has significant effects on the metal flow and calibration curves, thereby affects the measurement of interfacial friction factor. Moreover, the HT coefficients are different for glass lubricant and dry friction conditions. Therefore, different HT coefficients should be employed to generate the calibration curves when both of the lubricant conditions were applied for determining the interfacial friction coefficients in hot ring-compression of Ti-6Al-4V titanium alloy.     

Numerical and experimental investigation of pulsating blankholder effect on drawing of cylindrical part of aluminum alloy in deep drawing process

In this study, the effect of a new pulsating blankholder system has been investigated on improving the formability of aluminum 1050 alloy. By using this system, during each pulsating cycle, first, the metal was easily flowed into the die through removing the blankholder force, and then the blankholder force applied by springs was employed to prevent excessive metal flow and wrinkling. Deep drawing of cylindrical cup was simulated by ABAQUS6.7 software. Cup depth, tearing, and thickness distribution of the experimental and numerical analyses were then compared. The results indicated that by using the pulsating blankholder system coupled with proper frequency and gap, the cup depth can be increased and thickness distribution can be improved. Further, good agreement was observed between simulation and experimental results.     

利用西门子电气对1400t精锻机进行电气及数控化改造

在尊重原设备设计思想的基础上,不迷信原设计,对原来的设计思路充分理解和消化,然后根据现场情况谨慎创新,对1400t精锻机进行了电气和数控化改造,实现和增加了数控系统的模块化、控制线路的数字化、控制软件的智能化、硬件平台的先进化、故障判断的直观化、故障修复的智能化设计,全面更换了1400t精锻机老化的电气系统,实现了优越先进、功能完备、安全可靠的系统数控化。     

Preform and forging process designs based on geometrical features using 2D and 3D FEM simulations

The requirements of compact and integrated industrial products make it more difficult to produce these complicated parts. The aim of this paper attempts to propose methods of finish forging die and preform designs to produce a product consisting of a solid spur gear and cylindrical cup features. One- and two-step forming processes were proposed and evaluated using computer-aided engineering simulations. For one-step extrusion or upsetting processes, diameters and heights of billet were calculated using the product volume and the corresponding cup or gear features, respectively. For two-step forming process, Tee-shaped preform designs were proposed based on the product volume and the feature volume ratio of cup to gear; corner and fillet arcs were adopted to modify the profile of Tee and control the material flow in the finisher die. The forming processes of preform and finisher were analyzed using the two- and three-dimensional finite-element method models to predict the detail characteristics of sectional material flow and the completely three-dimensional deformation results, respectively. Experimental tests were also carried out to validate the proposed simulation models and design methods. The forming loads, the stress and strain distributions of forged part, and the occurrences of defects were studied and a suitable preform and corresponding die designs were obtained. The proposed preform designs were verified via the numerical analyses for the feasibility study. Finally, a sound gear product had been made successfully using the proposed suitable design of preform.     

Effect of pre-treatment polishing on fabrication of anodic aluminum oxide using commercial aluminum alloy

Aluminum anodizing is a process in which metal is oxidized with an electrochemical method to make a metallic oxide. Because it can be used to manufacture an Anodic aluminum oxide (AAO) with dozens to hundreds of nanoscale pores that are vertically and uniformly arranged, it is widely applied in a variety of fields. In particular, most of the pre-treatment methods in the anodic oxidation processes using a high-purity aluminum adopt surface treatment through electrolyte polishing. In this study, complex polishing was performed using an abrasive film and Magnetorheological (MR) fluid for a commercial aluminum alloy to produce a uniform porous oxidized aluminum. The surface roughness and surface integrity were analyzed after each process to investigate the production behavior of AAO in relation to the pre-treatment of the surface. In addition, a study was conducted on the nano-pore production by the anodizing process in accordance with the pre-treatment polishing, in terms of the work-hardening and residual stress. Thus, in the anodic oxidation process, it was possible to generate uniform nano-pores when surface integrity including surface roughness and residual stress distribution of the aluminum alloys are excellent. Test results showed that the polishing process using the MR fluid did not generate process scratches and pits, but could effectively remove the work-hardening and compressive residual stress, proving that MR fluid polishing method is a suitable pre-treatment process to produce nano-pores in the anodizing process.

     

Near net shape spline forging: An experimental investigation and a simple upper bound analysis

A simple analysis based on an upper bound elemental technique is presented for the incremental forging of a near-net shaped splined rotor shaft-type component formed using a cylindrical rod-type specimen. The results of an experimental investigation made into the working pressures and deformation modes observed during progressive forging of tellurium-lead specimens of different aspect (length to diameter) ratios into spline shaped components are compared with those predicted theoretically. The agreement was found to be reasonable and encouraging.     

Multi-objective optimization of process parameters for the helical gear precision forging by using Taguchi method

Precision forging of the helical gear is a complex metal forming process under coupled effects with multi-factors. The various process parameters such as deformation temperature, punch velocity and friction conditions affect the forming process differently, thus the optimization design of process parameters is necessary to obtain a good product. In this paper, an optimization method for the helical gear precision forging is proposed based on the finite element method (FEM) and Taguchi method with multi-objective design. The maximum forging force and the die-fill quality are considered as the optimal objectives. The optimal parameters combination is obtained through S/N analysis and the analysis of variance (ANOVA). It is shown that, for helical gears precision forging, the most significant parameters affecting the maximum forging force and the die-fill quality are deformation temperature and friction coefficient. The verified experimental result agrees with the predictive value well, which demonstrates the effectiveness of the proposed optimization method.     

铝合金超声铸造中换能系统的有限元仿真分析

根据任意变截面杆纵向振动的波动方程,推导了用于超声波铸造的换能系统各部分的频率方程,并应用有限元分析软件ANSYS对结构进行了模态分析和谐响应分析,得到了系统的共振频率、位移节点、振速分布和输出振幅等重要参数,并应用多普勒测速仪进行了实验验证.与理论计算结果和试验测试结果比较,有限元仿真分析法获得了较高的精度.     

The effect of solid fraction and indirect forging pressure on mechanical properties of wrought aluminum alloy fabricated by electromagnetic stirring

This study demonstrated the effect of solid fraction and forging pressure on mechanical properties of the product of wrought aluminum alloys fabricated by the indirect rheoforging through electromagnetic stirring (EMS). In addition to EMS, the rheological material was examined for its response to various pouring temperatures as the rheo-material was forged into a sample which consisted parts that were directly and indirectly subjected to forge pressure. As results of investigating the relationship between microstructural features and mechanical properties of the product through microscopic inspection, the EMS rheo-forged materials revealed a fine and globular microstructure. Microstructures of Al6061 wrought aluminum alloy with uniform solid and liquid phase distributions (no segregation) demonstrated good mechanical properties with tensile strengths of up to 341 MPa.     

7075铝合金板淬火残余应力模拟及实验研究

铝合金板在淬火过程中产生较大的残余应力,导致构件出现变形、翘曲。采用准耦合法对7075铝合金板在淬火过程中的温度场和应力场进行数值模拟,利用盲孔法对淬火后的残余应力分布进行实验测量。结果表明,7075铝合金板淬火后残余应力呈现出外压内拉的分布状态,淬火过程中形成的较大温度梯度造成的不均匀塑性变形是应力产生的主要因素,铝板表层和心部冷却速度的变化导致了应力分布状态的转变。实验结果验证了准耦合模拟方法的可行性,研究结论为残余应力控制提供重要依据。     

Finite element simulation and experimental investigation of tool temperature during ultrasonically assisted turning of aerospace aluminum using multicoated carbide inserts

This paper summarizes the results of thermal finite element simulation and experimental studies of tool temperature in ultrasonic-assisted turning (UAT) of aerospace aluminum using multicoated carbide inserts. At first, mathematical models were developed in order to study the effects of tool coating, rake angle, cutting speed, and feed rate on the friction coefficient. Then with respect to the kinematics of the process, the cutting velocity model would be presented. This velocity model is used in combination with the mathematical model to define the friction coefficient during UAT. The mentioned frictional model is used to write a user subroutine to incorporate the effect of friction coefficient as a function of cutting parameters in the finite element program Abaqus. The results of this simulation make it possible to determine cutting temperature patterns accurately. It is also used to study the effect of cutting parameters (cutting speed, feed rate, rake angle, and vibration amplitude) on UAT. Finally, the simulation results are compared with experimental measurements of cutting temperatures from ultrasonic-assisted turning tests. The results show that ultrasonic-assisted turning is able to lower the maximum cutting temperature in cutting tool, about 29 %, in low feed rates (≈0.14 mm/rev), with a vibration amplitude of ≈10 μm and work velocity of ≈0.5 m/s.     

精密伺服锻压机双电机同步控制方案分析

针对新型伺服锻压机存在电机精确同步的瓶颈问题,引入了双电机交叉耦合同步控制方案.该方案将主、从电机的电流进行比较,得到了一个差值作为从电机的附加反馈信号.从电机根据这一附加反馈信号对自身的速度进行了动态调整,从而获得了较好的同步精度.先从理论角度对比分析了主令双电机同步控制方案和交叉耦合双电机同步控制方案两者的控制效果以及存在的问题.接着分别使用主令双电机同步控制方案和交叉耦合双电机同步控制方案控制锻压机执行相同的工艺曲线,通过实验对比分析了两种同步方案下的耦合误差和两电机的扭矩曲线.研究结果表明,在紧耦合的双电机系统中,交叉耦合双电机同步控制方案能满足系统的位置和扭矩同步要求,两电机的同步误差在0.35°以内.