基于动态啮合力的人字齿轮摩擦因数分析

计及时变啮合刚度、传递误差及摩擦力等对人字齿轮副动力学特性的影响,建立了人字齿轮副平移-扭转振动分析模型.在获得动载荷的基础上,结合混合弹流润滑理论计算了混合弹流润滑摩擦因数.基于Block闪温理论研究了齿轮啮合过程中的齿面温升效应,获得了齿面温升沿啮合线的分布规律.分析了齿面温升、齿面粗糙度和载荷对齿面摩擦因数的影响...     

不锈钢表面粗糙度对超高分子量聚乙烯摩擦磨损性能的影响

以超高分子量聚乙烯软骨材料为销样,316不锈钢硬骨材料为盘样,在自制的销－盘式磨损试验机上考察了不锈钢盘样表面粗糙度对超高分子量聚乙烯摩擦磨损性能的影响,并利用光学显微镜观察了摩擦副表面的形貌,结果表明,在干摩擦条件下,表面粗糙度对超高分子量聚乙烯的摩擦磨损有较大影响,存在着适合的表面粗糙度范围,使超高分子量聚乙烯摩擦系数,磨损率最小。     

基于时变载荷的齿轮摩擦功率损失计算研究

应用齿轮啮合原理、齿轮接触分析和摩擦学理论,提出考虑齿轮瞬态啮合过程中传动效率随齿面接触载荷时变的齿轮摩擦功率损失计算方法;建立了啮合齿面间的相对运动速度、接触压力、滑动摩擦系数及摩擦功率损失的计算模型,并编制了计算程序;分析了齿轮几何参数、运行工况及润滑油温度等对齿轮摩擦功率损失的影响规律.研究结果为齿轮传动及其润滑系统的合理设计提供理论依据.     

超光滑表面粗糙度测量的研究

本文讨论了对积分散射测量的超光滑表面均方粗糙度进行修正的问题，得出结论：可以直接依赖于散射理论从积分散射测量确定表面粗糙度值。     

基体表面粗糙度对MoS_(2)/Ti薄膜摩擦磨损性能的影响EI北大核心CSCD

为揭示基体表面粗糙度对MoS_(2)/Ti固体润滑薄膜摩擦磨损性能的影响规律,并探究其摩擦磨损机理,采用磁控溅射方法,在不同表面粗糙度的轴承钢基体上沉积MoS_(2)/Ti薄膜。通过划痕测试仪、X射线衍射仪、场发射扫描电子显微镜和粗糙度轮廓仪,分别评价MoS_(2)/Ti薄膜的膜基结合力、物相成分、表面微观形貌以及表面粗糙度,并采用球-盘摩擦磨损实验研究干摩擦、固体-油复合润滑和固体-脂复合润滑条件下,MoS_(2)/Ti薄膜的摩擦磨损性能。结果表明:随着基体表面粗糙度的增加,MoS_(2)/Ti薄膜的表面粗糙度逐渐增加;薄膜中(002)_(MoS_(2))和(100)_(MoS_(2))衍射峰的强度先减弱后增加;薄膜与基体的结合性能降低。当基体表面粗糙度为0.01μm时,干摩擦条件下MoS_(2)/Ti薄膜具有良好的润滑特性,平均摩擦因数为0.101,磨痕浅且小;随基体粗糙度的升高,样品的平均摩擦因数和磨损率均是先增大后减小,薄膜的主要磨损机制由磨粒磨损转变为屑片形成和破碎。当基体粗糙度较大时(R_(a)=0.26μm),分子间相互作用的影响大于机械啮合作用。采用固体-油复合润滑,高基体粗糙度的薄膜磨损表面不再出现片层剥落现象,磨痕较浅,平均摩擦因数最高可减小19%。固体-脂复合润滑条件下,样品摩擦磨损性能较差,基体粗糙度对摩擦因数的影响不显著。     

表面粗糙度三维测量和评定的研究

本文论述了应用相移干涉原理测量三维表面粗糙度,给出了测量系统的组成,实现相移的微位移器件压电陶瓷应用,三维表面粗糙度评定参数的确定。     

干摩擦磨损过程中表面粗糙度的定量描述

基于金属磨损试验以及得出的摩擦系数和磨损形貌的变化规律,用轮廓算术平均偏差R_a、均方差σ、统计分布参数、偏态系数R_（sk）和峰态系数R_（ku）等可用于分析摩擦副磨损表面特性的典型表面粗糙度表征参数,定量分析了磨损过程中表面粗糙度的变化规律。结果表明,磨损稳定后,R_a和σ逐渐降低,磨损表面凸峰是钝峰,轮廓高度分布...     

应用FEM与圆环镦粗实验测定TC4钛合金高温变形时的摩擦因数

采用圆环镦粗与有限元模拟相结合的方法测定了TC4钛合金高温变形时摩擦因数.利用有限元模拟确定了摩擦因数的理论标定曲线,采用圆环镦粗实验确定圆环内径变化百分比与圆环高度压缩百分比的关系曲线,将圆环镦粗后的内径减小百分比与模拟得到的摩擦因数理论标定曲线进行对比,发现TC4钛合金在干摩擦和玻璃润滑剂的条件下摩擦因数分别为0....     

Minimizing tooth bending stress in spur gears with simplified shapes of fillet and tool shape determination

The strength of a gear is typically defined relative to durability (pitting) and load capacity (tooth-breakage). Tooth-breakage is controlled by the root shape and this gear part can be designed because there is no contact between gear pairs here. The shape of gears is generally defined by different standards, with the ISO standard probably being the most common one. Gears are manufactured using two principally different tools: rack tools and gear tools. In this work, the bending stress of involute teeth is minimized by shape optimization made directly on the final gear. This optimized shape is then used to find the cutting tool (the gear envelope) that can create this optimized gear shape. A simple but sufficiently flexible root parameterization is applied and emphasis is put on the importance of separating the shape parameterization from the finite element analysis of stresses. Large improvements in the stress level are found.     

The influence of surface roughness on the starved lubrication of ball bearings

Abstract

A theoretical analysis is made for starved lubrication of a rigid point contact under the influence of surface roughness. The results show that both the directional property and the standard deviation of the combined surface roughness can affect the load carrying capacity of the lubricant film as well as the friction on the solid surfaces. The combined effects of speed ratio of the contiguous surfaces and the roughness on starved lubrication are also obtained. The results show that the effects of surface roughness may improve the starvation a little, but that they are not remarkable. A regression equation is found for determining the critically starved lubricant inlet level. Such an inlet level can indicate the minimum limit of lubricant supplied quantity, and, beyond this limit, the load carrying capacity of the lubricant film will decrease sharply. In addition, experiments have been carried out to observe the starved lubrication of a ball rolling on a flat glass disc. It is shown that higher surface speeds may make the starved condition much worse.     

基于有限元分析的直齿轮搅油损失计算及实验验证

搅油损失的影响因素包括润滑油的运动粘度、工作温度,齿轮的模数、齿数、齿宽,旋转速度、齿轮的浸油深度,当地重力数值等,多种因素并存且形成了复杂的函数关系,难以直接用理论确定解析解。在对上述各种影响进行分析的基础上使用流体力学中边界层理论对齿轮搅油功率损失进行了理论分析,使用FLUENT软件中的多相流VOF模型、涡流K_ε模型对建立的搅油流动偏微分方程进行数值仿真计算分析,最后通过齿轮搅油功率损失实验对仿真结果进行了验证。分析结果表明,在低转速条件下使用仿真计算的方法可以有效地预测搅油功率损失数值。     

六韧带手性蜂窝材料韧带的冲击动荷系数及稳定性分析

手性蜂窝材料内部韧带的变形及失稳特性控制了该类材料的抗冲击性能。本文运用能量法和泛函数极值分析的方法,分别探讨了六韧带手性蜂窝材料在受到面内冲击时缓冲第一阶段中韧带的冲击动荷系数及韧带失稳坍塌临界压力,得到了韧带的动荷系数及其失稳临界压力的解析表达式,进而揭示手性蜂窝材料抗冲击性能的内部微结构溃塌机制和关键影响因素。结果表明:视为扭簧的韧带节点环在冲击压缩变形过程中扭转角越大,韧带的动荷系数越小,而韧带的失稳临界压力随着节点环扭转角的增大而增加。研究方法和结果可为手性蜂窝材料及其它蜂窝型材料抗冲击能力的进一步研究和微结构设计提供理论参考。      

Effect of the load location along the involute curve of spur gears on the applied stress at the fillet radius

In this study, attempts are carried out to determine the amount of stress at the fillet radius region of spur gears when the applied load location changes, along the involute curve, from the top surface to the bottom. For this purpose the photoelastic method and numerical MSC/NASTRAN software are used. The gears with pressure angle (ϕ) 20^o, and 25^o were prepared from photoelastic material type PLM‐4B in this study. Practical calibration is used to determine the fringe order value of this material. Four different modules (m); 6, 10, 14, and 20 mm were prepared for two different numbers of teeth (N); 18 and 26, with different face widths (B₁, B₂, B₃); 10, 17, 25.4 mm respectively. Four load values were applied on each tooth at five to six different load locations along the involutes curve profile. In order to accomplish the comparison between the results for different methods, the same sample dimensions and parameters were prepared again for the MSC/NASTRAN software. The results showed that the maximum applied stress at the fillet radius occur when the applied load location is on the top land of a tooth, and then that amount is decreased when the applied load positions change toward the bottom land. The results of the NASTRAN method showed that the applied stress at the fillet radius would be minimum when the loading point locates between the pitch circle and dedendum circle, in particular around 1.5 times module (1.5 m) of the total tooth height which equals 2.25 module, and then the applied stresses are increased again. However, in the photoelastic method the applied stresses were decreased continuously to the bottom land. The reasons behind such results can be attributed to the type of failure theories that can be used in NASTRAN software for characterization the applied stresses, i.e. considering types of applied stresses into account, such as bending, direct compressive, and shear stresses. Moreover, in order to compare the applied stress values at fillet regions, obtained by theoretical and practical approaches, four different standard mathematical equations are used for stress calculation at fillet radius of spur gears to show the difference of the parameters and variables that can affect the applied stress results.     

惯性载荷对螺旋锥齿轮动态啮合特性的影响研究

根据动力学原理和Lagrange乘子约束,考虑惯性载荷对螺旋锥齿轮动态啮合分析的影响,提出一种新的有限元分析模型,分析惯性载荷对螺旋锥齿轮动态啮合特性的影响规律。计算结果表明,随着惯性载荷增大,齿面接触力也随之增大;惯性载荷对于啮合区宽度、齿面接触应力及最大应力位置均有影响。因此,惯性载荷对于螺旋锥齿轮动态啮合分析是必须考虑的因素。     

基于HHT变换的超光滑加工表面谱分析

Hilbert-Huang变换是最新发展起来的处理非线性非平稳信号的时频分析方法。其基本的实现分为两步,多分辨经验模态分解和瞬时频率的求解,随后可以获得信号的时—频谱。这种方法的关键部分是多分辨经验模态分解,任何复杂的信号都可以分解为有限数目并且具有一定物理意义的固有模态函数。本文针对表面粗糙度用HHT进行了分析,得出相应结论,对加工有一定的指导意义。     

Improving spur gear microgeometry and surface finish by AFF process

This paper describes improving microgeometry and surface finish of spur gears by abrasive flow finishing (AFF) by experimentally identifying optimum values of finishing time and AFF medium viscosity. An experimental apparatus was developed for gear finishing by AFF using a medium of silicon carbide as abrasives, silly putty and silicone oil as blending agents. A special fixture was developed comprising of two metalon cylindrical disks having circumferential holes for back and forth movements of AFF medium between two adjacent flanks of 20MnCr5 alloy steel spur gear teeth. Twenty experiments were conducted varying AFF medium viscosity at four levels and finishing time at five levels to study their influence on error reduction in total profile, total lead, total pitch, runout, and average surface roughness. Results showed considerable reduction in the microgeometry deviation and surface roughness with AFF medium viscosity increase and existence of optimum finishing time for attaining maximum improvement in microgeometry and surface finish. Consequently, 25?min and 135?kPa.?s were identified as optimum values and corresponding gear’s microgeometry and microstructure were studied. It revealed that AFF-finished gear flank surfaces are free from cracks, cutter marks, thermal distortions. This proves AFF as economical and productive alternative for gear finishing.     

准双曲面齿轮动态啮合性能的有限元分析研究

研究准双曲面齿轮动态啮合有限元分析模型的构建方法,建立了合理的有限元模型。基于接触动力学的基本理论和显式有限元分析方法,对准双曲面齿轮的动态啮合性能进行了研究,得到啮合接触冲击特性、齿面接触区域、齿面接触应力及齿根弯曲应力等在轮齿动态啮合过程中的变化规律。以转速和负载两个典型的工作条件为变量,建立对比分析模型,研究转速和负载对准双曲面齿轮动态啮合性能的影响。转速对准双曲面齿轮动态啮合性能影响显著,而负载对准双面齿轮的动态啮合性能影响则跟转速有关,随着转速的增大,相同的负载变化对动态啮合性能的影响逐渐减弱。