Forming characteristics analysis of the cross-section of axially inner grooved copper tube

The simulation of the cross-section forming of axially inner grooved copper tube (AIGCT) is conducted using finite element (FE) software MSC.Marc. The stress–strain distribution, metal flow rule, and contact force are analyzed based on the simulation and experimental results. The results show that gaps in the groove walls are caused not only by the diametric clearance between the inner wall of the copper tube and the mandrel but also the bending deformation of the copper tube. The cross-sectional geometry and surface characteristics of grooves are determined by the multi-tooth mandrel. Smooth transition of the mandrel teeth addendum improves the metal flow and makes contact force vary slightly, which is good for preventing mandrel from failure. Improving the mandrel surface finish can also improve the inner surface quality of AIGCT. The results help to optimize the forming process parameters and improve the forming quality.     

Joining process for copper and aluminum tubes by rotary swaging method

Connection technique of copper and aluminum is a key challenge in refrigeration industry. In this paper, rotary swaging connection process is proposed to connect cooper tube and aluminum tube in physical way. We find the length of overlapped area has a great effect on the joint reliability, and it should exceed the deformation region length. The joint strength is approximately determined by necking. With the reduction of the diameter at the necking area, joint strength first increases and then decreases. Some experiments are carried out to test the joining strength. It is shown that the joints are reliable enough, and joining by rotary swaging method is effective to combine copper and aluminum tubes.     

内螺纹铜管滚珠旋压三维有限元模拟

内螺纹管滚珠旋压三维有限元模拟中,铜管的网格划分和滚珠加载方式是模拟的关键问题。通过建立简化的六分之一旋转对称模型和采用网格局部重划分技术,成功地模拟和再现内螺纹管滚珠旋压成形过程。对模拟结果的对称面变形的情况分析论证了模型简化的合理性和正确性。对模拟的应变分布和速度分布分析说明,齿成形的多道次局部成形规律。从计算的模具载荷变化情况分析了模具的使用寿命。     

内螺纹铜管滚珠旋压成形有限元分析

根据金属塑性成形原理和滚珠旋压成形的工艺特点,利用MSC.Mentat/Marc软件建立了内螺纹铜管滚珠旋压工艺的三维弹塑性非线性有限元模型.模拟了管坯从开始接触到变形稳定阶段内螺纹铜管的成形过程,探讨了铜管成形过程金属流动的位移规律及应变分布.     

内螺纹铜管滚珠旋压成形有限元模拟

根据金属塑性成形原理和滚珠旋压成形的特点,采用有限元软件MSC.Mentat/Marc建立了内螺纹铜管滚珠旋压工艺的三维弹塑性有限元模型.模拟了管坯从变形开始到变形稳定阶段不同滚珠压下量下内螺纹铜管的成形过程.将模拟得到的滚珠所受单位挤压力与理论分析值进行了比较,两者具有较好的一致性.以模拟结果为基础分析了滚珠压下量对内螺纹铜管成形的影响和滚珠与螺纹沟槽芯头的受力特点.     

冷凝铜管腐蚀现象显微分析

基于现代分析测试结果,分析制冷机冷凝器铜管电化学腐蚀机理。铜管的结构缺陷和加工缺陷引起冷却水中Fe3+离子沉积,从而发生氧化-还原反应及随后的电化学腐蚀,造成铜管壁穿孔;R22和冷冻机油进入冷却水系统中,提高循环冷却水酸性,加速冷却水管路腐蚀,给冷却水带来更多Fe3+,进而加速铜管腐蚀,造成制冷机失效。     

Fabrication of small size inner spiral ribbed copper tube by fluid mandrel drawing

This paper is concerned with the development of ultra-small inner spiral ribbed copper tubes with high-quality heat transfer. Since the demand for the ultra-small tubes in electrical appliances is currently high and will be greater in the future, the technology employed must enable the production of inner spiral ribbed fine tubes with various features, such as small size, high quality, high functionality, and low processing cost so as to meet the increasing demand. The conventional production method is suitable for large tubes with high drawability but is unsuitable for fabrication of long ultra-small tubes because of the difficulty to manufacture both an ultra-small spiral ribbed mandrel and a floating plug. This research paper has proposed four drawing methods as follows: tube sinking, water, oil, and wax as mandrels and presented the comparison of seven parameters, i.e., drawing stress ratio, wall thickness ratio, ribbed base width ratio, ribbed tip width ratio, ribbed height ratio, ribbed pitch ratio, and ribbed spiral angle ratio. It was found that tube sinking was unfit for making the ultra-small inner spiral ribbed copper tubes due to the resulting high ratio of wall thickness. The results of all the parameters were similar in the cases of oil and wax. Despite less impressive outcomes, water was easily removed from the inner spiral ribbed copper tube compared to oil and wax. Thus, the tube drawing using water as mandrel was most suitable for the production of the inner spiral ribbed copper tube.     

Effect of clearance on wrinkling of thin-walled rectangular tube in rotary draw bending process

The clearances between tube and various dies have a significant and complicated influence on the onset of wrinkling during the rotary draw bending process. To study the effect of clearance on wrinkling, a 3D finite element (FE) model of the process for thin-walled rectangular aluminum alloy tube has been built using the explicit code ABAQUS/Explicit and validated by comparing the experiment. Then, simulation and analysis of the process have been carried out based on the model. The influence laws of clearances between tube and various dies on wrinkling have been studied and the reasonable combination of clearances obtained using the combination method of 3D FE simulation and orthogonal experimental design. The results show that with the increase of tube mandrel clearance, Δc _m, and tube bending die clearance, Δc _b, the wrinkling wave number decreases rapidly, whereas the wrinkling wave height increases sharply. The effects of tube wiper die clearance, Δc _w, and tube pressure die clearance, Δc _p, on wrinkling are not significant. The reasonable combination of clearances is Δc _m?=?0.15 mm, Δc _b?=?0 mm, Δc _w?=?0 mm, and Δc _p?=?0 mm. These achievements are helpful to the design and optimization of the process.     

Magnetorheological finishing of grooved drum surface and its performance analysis in winding process

The fine level finishing of grooved drum surfaces is an essential requirement for enhancing the performance of the winding machines in today’s textil     

Research on cross-sectional deformation of double-ridged rectangular tube during H-typed rotary draw bending process

Based on the ABAQUS/Explicit, a three-dimensional elastic–plastic finite element model of the H96 brass double-ridged rectangular tube (DRRT) during H-typed rotary draw bending (RDB) was established and its reliability was validated by an experiment. With the model, distribution characteristic of cross-sectional deformation and effects of clearance and friction coefficient between tube and dies and core number on it were studied. The results show that the maximum cross-sectional height distortion ratio appears at the bending angle 60°. And the maximum cross-sectional width distortion ratio between side walls, as well as side walls of the ridge grooves, appears at the bending angle 80° and 60°, respectively. In addition, retracting mandrel has a great effect on the cross-sectional height distortion, but its influence on the cross-sectional width distortion can be ignored. And the maximum cross-sectional distortion ratio initially increases with increasing of clearance between tube and mandrel c _m and friction coefficient μ _b between tube and bending die, and then decreases with their increase, and initially decreases with the increase of core number N, and then increases with increasing of N. Moreover, the reasonable value of N is taken as 4.     

摇篮式五坐标加工中心C轴转台旋转故障原因分析与处理

针对HS664RT,摇篮式五坐标加工中心力矩电动机驱动的C轴转台故障,介绍了故障排查、处理方法和力矩电动机相位角同步设置步骤。     

旋锻机锻模头的运动分析

通过分析旋锻机锻头的运动发现传统锻头的不足,利用凸轮轮廓线设计等知识将原锻头结构加以改进后,再运用高等数学的积微分原理将改进后锻头的运动轨迹画出并进行分析,从而得出改进后的锻头结构,能够使对物料的瞬时打击力增大,最终实现提高加工工件时的工作效率和加工精度的目的.     

Hydrodynamic lubrication analysis for tube spinning process

A theoretical analysis based on the two dimensional isothermal Reynolds equation was developed for the hydrodynamic lubrication of the tube spinning process. The linear velocity of the forming tool and rotational velocity of the mandrel both influence the establishment of a hydrodynamic lubricant film thickness at the inlet zone. Formation of a hydrodynamic lubricant film thickness at the inside of the tube is ruled by the eccentricity of the mandrel and tube. The theoretical and experimental estimates of film thickness were compared and are in agreement.     

旋转管排式干燥机转子的强度计算

采用简化力学模型对一台旋转管排式干燥机转子系统的各部件进行了强度校核,结果表明各危险部位应力小于许用应力值,挠度与实测值相符。     

Thermo-hydrodynamic analysis of herringbone grooved journal bearings

Steady-state and stability characteristics of herringbone grooved journal bearings (HGJBs) are found considering thermal effect. The temperature of the fluid film rises significantly due to the frictional heat, thereby the viscosity of the fluid and the load carrying capacity decrease. A thermodynamic analysis requires the simultaneous solution of Reynolds equation along with energy equation of the fluid and heat conduction equations in the bush and the shaft. The linearized first-order perturbation technique is employed for the prediction of stiffness and damping coefficients of the oil film. Thereafter mass parameter and whirl ratio are found from the stability analysis. It is difficult to obtain the solution due to the numerical instability when the bearing is operated at high eccentricity ratios.     

Estimation of leakage through radial clearance during compression process of a rolling piston rotary compressor

The leakage characteristics during the compression process in a rolling piston rotary compressor were investigated in this research. The thermodynamic conditions and geometric features during the compression process were determined from the results of a numerical compressor simulation. Refrigerant R410a and lubricant oil PVE-68 were used as working fluids. Leakage models with and without consideration of the lubricant oil effect were used to examine leakage characteristics through the radial clearance. A model for pure refrigerant that included the operating conditions and geometric characteristics of a compressor was developed using the verified results of a CFD (Computational fluid dynamics) simulation. The area ratios for both the refrigerant and lubricant oil at the radial clearance was obtained by numerical analysis during the compression process of the rolling piston rotary compressor. The results showed that the cross sectional area at the radial clearance would be charged with the pure refrigerant up to a maximum of 81.2 % during the compression process.

     

斜置旋耕过程理论分析

分析了斜置旋耕的三维运动学特征 ,提出了斜置旋耕基本条件 ,确定了最佳斜置角