A model of thick film lubrication by soaps in wire drawing using a pseudo-plastic rheological law

A model for wire drawing lubrication by soap using realistic soap rheology, plastic at low temperature, non-Newtonian viscous at high temperature, is presented. A simplified analysis of the lubricant flow gives film thickness as a function of soap rheology and drawing pass parameters, which is shown to agree with experiment     

CVD金刚石薄膜涂层铜线拉丝模的制备与应用

提高金刚石薄膜的表面质量和附着力是实现CVD金刚石涂层在耐磨器件领域中广泛应用的关键因素.本文通过优化沉积工艺参数,采用直拉丝化学气相沉积法在WC- Co硬质合金拉丝模内孔表面沉积金刚石薄膜.检测了该涂层的表面形貌、薄膜质量以及表面粗糙度,并把所制备的CVD金刚石薄膜涂层拉丝模具在拉拔铜线材生产线上进行了应用试验,结果...     

超声振动拉丝实验研究

为了研究超声振动对金属丝拉拔加工过程的影响，研制了一套拉丝实验系统。系统由超声波驱动器、换能器、变幅杆、拉丝模、拉伸机等组成，通过对黄铜丝的拉拔实验，考察了超声振动对拉拔力和丝的表面质量的影响。当超声振幅达到一定值以后，超声振动使拉拔力减小显著。但随着拉丝速度增大，超声振动引起的拉拔力减小变缓。超声振动还可以减小金属丝的不均匀变形，有利于表面质量的提高。同普通拉丝相比，超声振动拉丝明显地降低了拉拔力，改善了表面盾量。     

陶瓷拉丝模在稳态拉拔状态下应力应变分析

在研制完成陶瓷拉丝模的基础上,利用数学计算和有限元法分析在稳态拉拔过程中,拉拔力与拉丝模应力的关系及拉丝模应力分布。通过论述,可以得到在稳态拉拔过程中,被拉拔线材的屈服强度、拉丝模工作锥半角、拉丝模与线材之间的摩擦系数对拉丝模应力应变的影响及拉丝模在拉拔力作用下内孔面应力应变分布     

1060纯铝微杯形件微拉深成形研究

微拉深成形以其高效率、低成本、高质量等优点成为一种可行的制造开口、空心、薄壁微型零件的微细加工方法。然而,由于微型化的影响,使得微拉深要比宏观拉深更加困难。研制精密微型落料-拉深复合模,成形出内径仅为1 mm的微杯形件。试验材料采用厚度为50 μm的1060纯铝,在真空氛围下经300 ℃分别退火1 h和8 h。微拉深试验在SANS CMT-5504电子万能试验机上进行,试验速度为0.05 mm/s,润滑剂为聚乙烯薄膜。研究退火工艺和压边力对拉深力、拉深比、制耳和起皱的影响。试验结果表明,顺利成形出质量良好、拉深比为2.1的微杯形件;经退火处理的坯料,拉深力降低,拉深比增大,制耳减弱;随着压边力的增加,起皱减弱,但当压边力超过一定数值后则导致拉裂。     

粉芯钢管拉拔时的理论解析

由于药芯的存在,管状药芯焊丝的拉拔不同于普通的钢管拉拔。对药芯焊丝拉拔过程中的受力情况进行了分析,建立了变形区和定径区的常微分方程组,推导出了拔制力、壁厚和面缩率的计算公式;在生产试验中,用所推得的解析模式计算了壁厚和拉拔力,并与实测值进行了比较,最大误差为10.18%,说明理论值与实测值的吻合较好。     

基于遗传算法的拉丝机压缩比的优化设计

以LZ-9/1200拉丝机为例,运用遗传算法,以总拉拔力最小为目标,对多道次钢丝拉拔成形过程的每道次部分压缩比进行了优化设计。以Java软件为编程工具,采用面向对象的编程技术,经过选择、交叉、变异多次迭代,得到了符合要求的满意解,为实际生产提供了可行方案。     

陶瓷拉丝模的受力分析及其结构设计

根据拉拔力的计算结果分析了陶瓷拉丝模工作时的受力状态,得到陶瓷拉丝模在拉拔加工过程中工作区和定径区的应力分布情况;基于分析结果对陶瓷拉丝模进行结构设计,得到与陶瓷材料匹配的合理的拉丝模结构。     

法兰为整体拉深的矩形盒成形应力分析

为了有效预测矩形盒拉深中的成形力和压料力，在拉深试验和有限元数值模拟的基础上，将法兰直边、曲边作为变形整体进行了应力应变分析。给出极限拉深时板坯下料以及拉深力和压料力的近似计算公式，为进一步开展试验、数值模拟和理论解析提供相应的参考资料。     

船用发动机重载工况下凸轮-滚轮副混合热弹流润滑分析

凸轮-滚轮副是大功率船用发动机配气机构的关键摩擦副,除受到弹簧力和自身的惯性力之外,还受到来自喷油器的极高燃油压力,工作条件极为苛刻。为了分析该摩擦副的性能,建立船用发动机重载工况下凸轮-滚轮副的混合热弹流润滑模型,计算燃油压力作用下的摩擦副油膜润滑、摩擦温升和磨损性能。结果表明：喷油器的燃油压力会显著降低凸轮-滚轮摩擦副之间的油膜厚度,同时产生较为严重的微凸体接触;随着环境温度的提高,凸轮-滚轮副的油膜厚度以及油膜温升会有所下降,而微凸体接触压力、摩擦力以及摩擦功率均会显著增加;滚轮打滑会造成凸轮-滚轮摩擦副的油膜厚度下降,同时导致油膜温升以及微凸体接触压力增大和并且致使表面磨损显著加剧。     

Cold drawing of regular polygonal tubular sections from round tubes

An analytical solution is obtained for the problem of cold drawing through flat idle rolls of regular polygonal metal tubular sections from round tube. The solution is based on obtaining a compatible velocity field that satisfies kinematic conditions to yield the strain-rate components. The stresses are obtained by combining the material constitutive law with Levy–Mises flow rule and integrating the equations of equilibrium. The solution is applied to the case of a low-carbon steel standard round pipe to investigate the effects of drawn section shape, friction at the roll interface, roll radius and wall thickness on the roll load and drawing force. The results obtained have shown that for different section shapes the roll load and drawing force decrease with the increase of the number of sides and increase with the decrease of corners radius. Surface friction has no appreciable effect on the loads which allows dry drawing. An increase in the roll radius increases the roll load but the drawing force remains unchanged. Increasing the wall thickness does not proportionally increase the roll load and drawing force; the tube wall behaves as a thin shell subjected to biaxial combined membrane and bending stresses.     

基于ANSYS技术的铜管空拔过程数值模拟分析

为优化铜管空拔工艺参数和提高工件加工质量,应用大型有限元分析软件ANSYS中的LS-DYNA求解器模拟了某规格铜管的空拔成形过程,得到了管件成形过程中任一时刻主要场量的分布云图,分析了成形过程中管件的变形和应力的特点,研究了摩擦力和模具锥角等因素对空拔力与管件伸长率的影响规律。数值模拟分析表明:在应变分布上,管件轴向和周向的最大塑性变形主要发生在管件与模具初始接触处与减径区;在应力分布上,轴向应力和径向应力随管件在模具中的位置不同而有较大差异,在壁厚方向上由管件的外表面到内表面其应力依次为拉应力和压应力,且最大压应力出现在减径区,而最大拉应力则出现在定径区连接处。在管件拉拔力的变化规律上,降低摩擦力和合理的模具锥角能使拉拔力控制在最小范围内。在管件伸长率的变化规律上,较大的摩擦力和模具锥角能使管件的伸长率增大。     

Experimental Investigation of Elastohydrodynamic (EHD) Film Thickness Behavior at High Speeds

At very high speeds, elastohydrodynamic (EHD) films may be considerably thinner than is predicted by classical isothermal regression equations such as that due to Dowson and Hamrock. This may arise because of viscous dissipation, shear thinning, frictional heating or starvation.

In this article, the contact between a steel ball and a glass disc over an entrainment speed ranging from 0.05 m s^?1 to 20 m s^?1 was studied. Two sets of tests were performed. In the preliminary testing, the disc was driven at speeds of up to 20 m s^?1 and the ball was driven by tractive rolling against the disc, its speed being determined using a magnetic method. After all possible explanations for the reduction in film thickness at high speeds were considered, it was shown that the results, which fall well below classical predictions, are consistent with inlet shear heating at the observed sliding speeds.

Another set of tests was then performed, with both disc and ball driven separately, so that the accuracy of the shear heating theory for different types of oils and at different sliding conditions could be assessed. It was found that the thermal correction factor predicts the trend of film thickness behavior well for the oils tested and is particularly accurate at certain slide–roll ratios (depending on the type of oil). Experimental data were also used to obtain improved coefficients for the correction factor for different types of oil to achieve better prediction of film thickness at high speed throughout the whole range of slide–roll ratios.     

电塑性效应及其应用

评述显示电塑性效应的最早实验，电塑性研究的新近信息和电塑性技术的应用前景。利用高密度电流脉冲剌激导致的电塑性现象，是一种综合物理效应，它主要由电子对位错的有效推动作用引起，焦尔热效应、磁压缩效应、电流集肤效应、电子润滑剂效应起辅助作用。与传统拔丝工艺比较，电塑性拔丝显著降低掺制力，增大金属的塑性，改进丝的质量和性能，减免中间退火，强化生产，提高生产力，节约能源，改善生态环境，是一种有发展前途的新的     

铝包钢丝制造新技术的研究

介绍了铝包钢丝的最新生产技术。该技术为采用连续挤压包覆工艺制造毛坯,再通过强制润滑拉拔工艺将毛坯拉制成产品。针对连续挤压包覆工艺,给出了变形温度、变形速度、钢线预热温度、钢线速度和钢线张力等工艺参数的确定原则,提出了各工艺参数的控制范围。对强制润滑拉拔工艺,试验研究了变形程度和拉拔速度等参数对线材力学性能的影响。     

Al_2O_3基陶瓷拉丝模材料的摩擦磨损性能

采用热压法制备出三种Al2O3基复合陶瓷材料,用于陶瓷拉丝模的制作。计算出拉丝模在拉拔加工中的应力分布,指出拉丝模应力最大和磨损最严重的区域。陶瓷拉丝模的摩擦磨损特性是影响拉丝模工作寿命的主要原因,因此在MRH-3高速环块磨损试验机上对Al2O3基复合陶瓷材料摩擦磨损行为及其磨损机理作了试验研究。测试出Al2O3基复合陶瓷材料在不同转速和载荷下,摩擦因数和磨损率的变化规律。通过扫描电镜观测其磨损区微观形貌,分析其滑动摩擦的微观机理为机械磨损耕犁、粘着和脆性微脱落。结果表明,这三种Al2O3基复合陶瓷拉丝模材料具有较高抗弯强度和断裂韧度。Al2O3基复合陶瓷材料的磨损机理主要是脆性脱落和耕犁,具有良好的耐磨性,是制备拉丝模的优良材料。     

数值模拟分析工艺参数与拉深件壁厚变化的关系

在分析板料拉深成形有限元理论的基础上建立数值模拟的分析模型,利用数值模拟技术系统地对拉深过程进行模拟。主要研究模具圆角半径、摩擦因数、压边力与模具间隙等工艺参数与拉深件壁厚最大变薄率的内在关系。     

On the optimal die curvature in deep drawing processes

The paper presents an attempt to increase the limit drawing ratio of deep drawing processes by searching an optimal die curvature, which minimizes the drawing load. The search done here for an optimal die curvature is based on experimental observations and followed by a detailed upper bound analysis. The analysis takes into account the non-steady character of the process (from a 2D circular plane blank into a 3D axisymmetric cup). The plastic flow along the die curvature is expressed in a toroidal coordinate system which seemingly describes more naturally a smooth velocity field along the real toroidal profile of the die. The outcome provides more closely the relationship between the energy dissipation rate and the die curvature so that a preferred die curvature is obtainable by energy minimization.Circular sheet blanks, made from aluminum and copper, were drawn through dies with different radii of curvature (with at least five repetitions at each radius) to capture the features of the optimal dies whenever exists.The main result is that under certain circumstances an optimal die curvature does exist. It depends largely on the drawing ratio and the blank/die interfacial friction, m, but appears quite insensitive to the initial thickness of the blanks. The optimal die curvature is pronounced in the cases where the frictional resistance is relatively low, otherwise it is indistinctable and remains practically undeterminable by designers.     

The effect of a non-Newtonian lubricant on piston ring lubrication

The effect of a non-Newtonian oil (shear thinning) on the lubrication of a piston ring is theoretically investigated. A variation of shear strain rate with shear stress that is cubic in form is used to obtain a modified form of the Reynolds equation (dynamic) applicable to a run-in ring profile which is considered to be a double parabola with a central straight portion. Numerical solutions are obtained for the film thickness, pressure and frictional force over a complete stroke for the case of a constant load. Results presented in non-dimensional form show that the effect of pseudo plasticity is to reduce slightly the minimum film thickness, peak pressure ratio and friction coefficient.     

A hydrodynamic lubrication model for the deep-drawing process

A steady hydrodynamic lubrication model that includes the pressure viscosity factor has been developed for the deep-drawing process. Equations for lubricant film thickness, radial and drawing stresses are presented. Analysis reveals that the pressure viscosity factor has a significant influence on estimating lubricant film thickness and radial and drawing stresses.