基于包络法的实时无隙钢球精密传动齿廓顶切研究

实时无隙钢球精密传动实际齿廓是否顶切直接影响其传动性能。基于包络法,对实时无隙钢球精密传动齿廓顶切问题展开研究工作。在基本设计参数给定条件下,分析出外摆线槽和内摆线槽实际齿廓非顶切条件,获取加工外摆线槽和内摆线槽时齿面均不出现顶切的刀具最大进给量(即最大槽深),并通过计算机图形仿真进行验证。根据以上分析结果,推导出钢球和齿面正确啮合时的钢球半径应满足的不等式方程,分析了钢球半径与影响参数之间的关系,结果表明钢球半径随发生圆半径的增大、短幅系数的减小而变大,且发生圆半径愈大、短幅系数愈小,钢球尺寸的选择范围愈广。研究结果可为实时无隙钢球精密传动的设计制造提供一定的理论依据。     

渐开线圆柱直齿轮结构参数对啮合效率的影响分析

以渐开线圆柱齿轮机构啮合效率为研究对象,基于齿轮副间接触反力的概念,分析了接触齿面间摩擦因数的影响因素,借鉴已有摩擦因数研究模型,分析了直齿和斜齿传动的啮合特点,推导出直齿齿轮传动的瞬时啮合效率和平均啮合效率的数学求解式;以直齿齿轮传动为例,在不同传动比、摩擦因数、压力角情况下分析了齿轮机构的啮合效率。结果表明,摩擦因数与齿轮啮合效率成反比,较大的压力角和传动比能提高齿轮的啮合效率,增速齿轮传动比减速齿轮传动的啮合效率高。     

实时无隙钢球精密传动等速啮合副闪温研究

根据机构的结构特点和闪温理论,研究实时无隙精密钢球传动等速啮合副瞬时接触温升规律,推导出啮合副中各接触点的相对滑动速度、最大接触应力和摩擦功率的计算公式,建立了等速啮合副瞬时接触温升的数学分析模型。通过Matlab编程绘制出一个运动周期内啮合副最大接触应力的变化曲线,计算出不同设计参数下机构的额定载荷,得到一个运动周期内啮合副中最大闪温的变化曲线,并分析了设计参数对最大闪温的影响。结果表明:啮合副闪温的最大值出现在环槽内侧钢球位置角为π时,设计参数对机构最大闪温有较明显的影响。研究结果为无隙钢球精密传动等速啮合副胶合强度分析与热力耦合分析奠定了理论基础。     

精密钢球传动耦合热弹性半解析接触模型及其接触特征

在修正精密钢球传动受力模型和相对滑动模型基础上,建立精密钢球传动啮合副耦合热弹性半解析接触模型。采用热源法推导啮合副接触温升的半解析式,并利用影响系数法计算考虑耦合热弹性影响的啮合刚度和啮合副变形。为提高模型的计算效率,给出了对应公式的离散卷积形式。深入分析精密钢球传动的耦合热弹性接触特征,并通过对比分析验证半解析模型的可行性。结果表明:中心盘外侧齿面上的接触温升相对最高,行星盘内侧齿面上的接触温升相对最低;啮合副耦合热弹性接触模型计算的啮合副变形和啮合刚度要大于Hertz接触模型的计算结果。研究结果可为考虑热特性的精密钢球传动动力学特性的研究以及实际工程应用提供一定的理论依据。     

实时无隙钢球精密传动啮合副本体温度场分析

根据传热学理论,建立实时无隙钢球精密传动啮合副本体温度场的计算模型,结合机构的结构特点,推导出啮合副相对滑动速度、最大接触应力和摩擦因数的计算公式,建立了啮合副热流密度以及摆线槽啮合面、钢球表面和啮合副端面等区域的对流换热系数数学模型。通过有限元软件计算出啮合副本体温度场,分析了机构设计参数对本体温度场的影响规律。结果表明:中心盘的本体温度高于行星盘,且参数变化对啮合副本体温度场有较明显的影响。研究结果为实时无隙钢球精密传动啮合副热弹耦合分析与可靠性研究奠定了理论基础。     

正交面齿轮齿面温升的研究

运用传热学基本原理，提出了面齿轮传动齿面温升计算的物理模型，获得了面齿轮齿面最大瞬时温升的基本公式。给出了温升计算中的主要参数，齿面相对速度和接触椭圆轴半径的计算方法。通过算例分析了如齿数，模数等参数对温升的影响，并得出有益的结论。     

基于热变形的摆线钢球啮合副啮合刚度分析

为研究摆线钢球啮合副热变形对精密钢球传动动力学性能的影响,应用格林函数法求解摆线钢球啮合副接触点热变形,分析系统参数对热变形的影响。根据啮合副热变形引起的行星盘转角变形,推导出啮合刚度系数表达式,分析影响啮合刚度系数变化规律的因素。建立啮合副有限元单齿模型,通过热结构耦合对啮合副热变形有限元仿真。结果表明外摆线槽热变形高于内摆线槽,最大热变形出现在外摆线槽三分之一齿高附近,热啮合刚度系数小范围内近似呈正弦函数规律周期性变化,系统参数对热变形和热啮合刚度系数影响较大。本研究为精密钢球传动热动力学分析提供理论基础。     

无隙摆线钢球传动啮合副啮合刚度系数分析

应用数值算法计算空间点接触赫兹接触系数,计算出无隙摆线钢球传动啮合副啮合刚度系数。利用啮合点刚度系数求解行星盘转角变形;基于行星盘转角变形,以偏心输入轴转角为参变量,对啮合刚度系数进行等效简化,求出等效简化后啮合刚度系数计算公式,并对影响因素进行分析。结果表明:等效简化啮合刚度系数是啮合副结构几何尺寸的函数且具有时变性,并随偏心轴输入轴转角按正弦曲线关系变化。文中研究为精密摆线钢球传动啮合副动力特性分析提供了方法,完善了精密摆线钢球传动的动力学理论。     

固体润滑膜航天高速齿轮动态传动性能的研究

本论文从理论上对固体润滑膜航天高速齿轮的传动性能做了分析研究。系统分析了该齿轮结构、传动和使用的特点,建立了齿轮传动的动力学模型与运动方程。从而得出齿轮传动中振动的位移响应和速度响应。建立了固体润滑膜轮齿弹性接触问题的数学模型和齿面摩擦温升问题的热传导数学模型。详细推导出计算齿面接触带宽尺寸、轮齿上动载荷、齿面上固体润滑膜作用下的修正动载荷、各种初值与边界条件下的齿面温升、齿面温度等的理论公式。作为输入的主动轮转速、齿轮的制造与安装误差、齿轮的结构设计参数等,通过这些理论的处理,可以得出沿啮合线上各瞬时啮合点的一系列的瞬态响应。借助计算机,可以系统研究航天高速齿轮传动的瞬态特性。绘制一系列的动态曲线和图表。从中找出齿轮设计与传动性能的综合关系,寻得齿轮失效的机理和根源。对于指导航天齿轮的优化设计与试验研究有一定的参考价值。     

旋转齿轮瞬时接触应力和温度的分析模拟

建立了高速齿轮传动轮齿瞬时接触温度的分析方法和模型;采用赫兹接触理论和有限元接触分析方法分析了标准渐开线齿廓和齿顶修形齿廓的齿面接触压力;研究了啮合过程中轮齿的相对滑动速度和齿面摩擦因数以及摩擦热流密度的计算方法;建立了轮齿本体温度的有限元温度分析模型;计算了轮齿接触面的瞬时温升;分析了标准和齿顶修形渐开线齿轮的轮齿本体温度和瞬时接触温度及相关因素对它们的影响。     

精密滚珠丝杠副丝杠滚道磨损异常的原因分析

实践中发现,精密滚珠丝杠副丝杠轴滚道的磨损明显大于螺母滚道,本文从弹性接触和润滑状态两方面分析了产生这一现象的原因。研究表明,滚珠与丝杠轴滚道的接触应力高于滚珠与螺母滚道的接触应力,而滚珠与螺母滚道接触面的润滑状态优于滚珠与丝杠轴滚道接触面。该研究结果为滚珠丝杠副的合理设计和适当润滑提供了理论依据。     

实时无隙钢球精密传动空间速度矢模型

针对实时无隙钢球精密传动机构中钢球的空间运动问题,根据微分几何理论,推导出了修正D-H变换矩阵,得到了传动机构钢球上任意一点相对于中心盘和组合行星盘的位置。利用转换机构法和空间几何建模理论,建立了钢球相对于中心盘和组合行星盘的空间相对速度矢模型。分析了传动机构摆线盘槽形角和钢球数对速度矢模型的影响。仿真结果与数值模拟结果的对比分析验证了空间速度矢模型的可靠性。     

Thermal characteristics analysis and error prediction for lubricated multi-link high-speed precision presses

Thermal models are important in the process of predicting the thermal characteristics and corresponding thermal error of multi-link high-speed precision presses (MLHSPPs) with an oil-lubrication system. Previous models only involved the effects of bearing stiffness, temperature change of bearings, flexibility of crank shaft on the heat generation power, while the influences of revolute clearance joint and flexibility of linkage are seldom considered, which inevitably reduces the accuracy of thermal analysis. To overcome this problem, dynamic models of flexible multi-link mechanisms (MLM) with clearance, lubrication, crankshaft-bearing system are constructed, the interaction forces between pin and bushing are obtained to calculate its heat generation power. Then, an improved model of MLHSPP with lubrication is proposed to analyze the temperature evolution and the thermal error between slider and work table at the position of LDP, by considering bearing stiffness, temperature change of bearings, flexibility of crank shaft, linkage, clearance, lubrication and thermal contact resistance all together. Compared with results from traditional models, the simulation data from this improved thermal model agree well with experiment, which proves the validity of the proposed model. Furthermore, the temperature rise and the thermal error of MLHSPP between slider and work table at the position of LDP under different input speeds, lubricating oil flux and contact angles of ball bearing were also studied.

     

滚动轴承弹性接触动态特性有限元分析

滚动轴承弹性滚动接触动态特性直接影响转子系统的精度及动态特性,针对滚动轴承弹性滚动接触动态特性问题,以深沟球轴承61914为例,在同时考虑内环、外环、滚珠及保持架变形的情况下,建立滚动轴承三维弹性滚动接触有限元模型,采用有限单元法计算滚动轴承在不同转速、径向力及轴向力等载荷工况下滚动轴承的接触应力及滚珠与内环的运动状态。结果表明,有限单元法能在满足高精度计算的情况下求解各种复杂工况下的滚动轴承动力学特性,为进一步研究滚动轴承弹性滚动接触动态特性提供有力的研究方法。     

Thermal characteristics of a CNC feed system under varying operating conditions

In high-speed and high-precision feed systems, thermal positioning errors are mainly caused by the non-uniform temperature variations and resulting time-varying thermal deformations under different operating conditions. The research presented here ultimately aims to develop a generic method capable of evaluating the thermal characteristics (such as temperature rise of heat sources, thermal positioning error) of the feed system induced by varying operating conditions (feed speed, cutting load and preload of ball screw). The thermal contact resistance between the balls and the inner and outer rings of supporting bearing is calculated using the Hertzian theory and JHM method. Experiments were carried out on a high-speed feed system experimental bench, and the influences of operating conditions on temperature rises of supporting bearings and ball screw nut were analyzed. Based on a WNN-NARMAL2 model, the relationship between temperature rise of supporting bearings and operating conditions was established. Furthermore, with the temperature of the ball screw nut set to be a moving heat source load, the temperature and thermal deformation distributions of the ball screw were simulated. The work described lays a solid foundation for thermal error prediction and compensation of a feed system under varying operating conditions.     

轴表面矩形微螺旋槽织构对唇形油封密封性能的影响

基于唇形油封的反向泵送作用密封原理,提出了一种轴表面矩形微螺旋槽织构,以提升油封密封性能;建立了油封唇口稳态的符合质量守恒的流体润滑理论模型,考虑了油封唇口表面粗糙形貌和弹性变形的影响,采用有限元法求解流体压力控制方程,获得了泵送率和摩擦扭矩等性能参数,研究了矩形微螺旋槽织构参数和轴转速对油封密封性能的影响规律。结果表明：泵送率具有随微螺旋槽角度的增大而呈先缓慢增大后逐渐减小,且螺旋角最佳值约25°,随微螺旋槽深度、线数和轴转速的增大而增大等变化规律;摩擦扭矩具有随微螺旋槽角度、深度的增大而减小,随微螺旋槽线数的增大而增大,随轴转速的增大而呈先增大后减小以至趋于稳定等变化规律。研究结果为轴表面微槽织构提高油封密封性能的设计与应用提供了参考。     

Lubrication of a rubber ball rolling with spin

Relative spin is present between surfaces at each point of contact when a ball is rolled between two circular contra-rotating plates. This gives rise to tangential frictional tractions transmitted across the contact surfaces which may result in a creep of the ball perpendicular to its direction of rolling. This paper reports a study made of rubber and steel balls rolling between plates of perspex lubricated with various oils and water.In dry contact an unrestrained ball, whether of rubber or steel, was found to creep radially outwards between the contra-rotating plates in a manner anticipated by earlier work, but when surfaces were lubricated with a viscous oil steel balls showed a neutral behaviour and rubber balls actually crept inwards. The inward creep was quite unexpected. Such behaviour suggests a greater traction, due to spin, over the back half of the contact zone arising by tilt between the contact surfaces. Estimates and actual measurements of tilt generated by elastohydrodynamic action were used to predict inward creep which could then be compared directly with experiment. The comparison shows that tilt clearly contributes to inward creep though does not fully explain the observed results.     

轴承用球三点接触纯滚动接触疲劳寿命试验机

介绍了一种新型的轴承用球三点接触式纯滚动疲劳寿命试验机。试验机主要包括驱动装置、从动装置和加载装置3部分,附加装置中的热电偶、加速度传感器和计数器分别测量温度、振动和转动圈数。被测试样球仅在同一最大圆截面上受到3次非等间隔但等强度的循环接触载荷作用,并沿此圆周作纯滚动,试样球的最大转速为23 000 r/min,最大赫兹接触应力可达7 GPa。该试验机可用于评定各种材料轴承用球的滚动接触疲劳性能。     

Multibody contact dynamics on mechanisms with deep groove ball bearing joints

The dynamics of ball bearings are important to fatigue breakage, dynamic performance and motion precision of mechanisms connected by ball bearings joints with multi-clearances. In this study, a new method is proposed for multibody dynamics analysis on mechanisms under the effects of radial internal clearances and impact of balls/cage pockets interactions of ball bearings. Including balls/rings interactions and balls/cage pockets interactions, the three dimensional dynamics models of the crank slider mechanism are established and calculated by generalized-α algorithms on the basis of Hertzian contact theory and penalty function method. The rules of eccentric trajectories of inner and outer ring center for one ball bearing joint are verified with the results calculated by XU’s references. The results of dynamic errors, motion trajectories, dynamic forces are achieved under different speeds, radial clearances and number of ball bearings. The speeds and radial clearances are critical to the dynamic performances and motion precision of mechanisms, especially the number of ball bearings. The number of ball bearings is important to impact force and motion stability of the mechanism.     

Ball Bearings for High Temperature Liquid Sodium

A project has been conducted in support of the liquid metal cooled fast breeder nuclear reactor development, in which ball bearings have been designed, manufactured, and tested specifically for a typical reactor application involving operation in high temperature sodium.

A powder-processed tool steel was selected for rings and balls, and cages were manufactured from various candidate materials. Test bearings were made according to 7306 size (30 mm bore) envelope dimensions and tested under pure thrust loads up to 500 lbs, and speeds up to 1,000 rpm. A bearing life of 4 million shaft revolutions (67 hrs) was achieved in 600 F liquid sodium with an oxide concentration of 51 to 69 parts per million for the major part of the test. Excessive torque (greater than 30 pound inches), bearing noise (hash) and/or incipient binding constituted failure criteria. Wear of the balls and rings was identified as the principal operative failure mechanism determined by correlating operating performance and post-test microscopic and metrological examination. The results of this program confirmed that rolling contact bearings are viable mechanisms for use in high temperature liquid sodium systems and specific recommendations for LMFBR applications are made.