微小型零件螺纹连接中预紧力的精确控制

针对不同的螺纹副间摩擦力不确定,仅靠提高扭矩的控制精度无法保证预紧力一致性的问题,提出了一种预紧力控制方法——扭矩/时间控制法。该方法基于螺栓弹性变形范围内预紧力与扭矩、转角的关系,根据恒定转速下扭矩随时间变化的斜率关系以及系统的刚度,对每对螺纹副施加不同的拧紧力矩,以提高预紧力的一致性。仿真模拟带碟形弹簧垫圈的螺纹副拧紧螺母的装配过程,按照扭矩/时间控制法进行分析,结果表明,刚度与扭矩斜率比在±0.02%内波动时,预紧力控制精度为2.94%,说明扭矩/时间控制法具有较好的精度。     

弹性胀套结构的受力分析

弹性胀套是一种新型的联接方式，它利用2锥面压紧后所产生的摩擦力来传递扭矩和轴向力。与其他传统的联接方式相比具有以下优点：     

框架结构松动EEMD损伤识别实验研究

针对连接结构在振动环境下易发生松动的问题,进行了框架结构模型连接松动损伤识别实验研究。根据螺钉在不同扭矩下的结构稳态响应信号,分析了信号功率谱差异和松动损伤引起的非线性特征,对响应信号进行了总体平均经验模式分解(EEMD),利用第1阶固有模式函数(IMF)构造能量损伤指标进行螺钉连接松动识别。结果表明,基于高频固有模式函数所构造的能量损伤指标可以有效表征不同扭矩下的连接松动所引起的结构非线性损伤,能够较好地反映螺钉连接结构的松动情况。     

螺旋槽丝锥的结构优化及有限元分析

针对丝锥在设计制造时存在的问题,在丝锥物理模型的基础上计算了切削力和丝锥侧面与工件挤压产生的摩擦力,建立了二者产生的扭矩与轴向力的预测模型。以攻丝扭矩模型中的最小扭矩为目标对丝锥几何结构参数进行优化,并运用DEFORM软件对优化后的三维模型进行仿真分析,验证了优化方法的正确性。     

XY交流伺服工作台摩擦实验方法的研究

摩擦是影响XY交流伺服工作台运动控制精度的重要因素.采用基于扭矩测量和伺服电流测量两种方式对工作台系统中的摩擦力进行了研究.扭矩测量方式比较直接,可以方便地用于摩擦模型的参数估计;而电流测量方式能更精确地反映系统中摩擦力的变化信息.仿真实验表明,综合使用两种方法可以更加灵活地对摩擦力进行补偿控制.     

AP1000蒸汽发生器人孔法兰螺栓预紧力校核

根据在施工现场采用螺栓拉伸机不能松动由扭矩扳手紧固的AP1000蒸汽发生器(SG)人孔法兰螺栓现象,简要分析了蒸汽发生器在生产和安装期间选用的扭矩控制法、伸长量控制法等预紧方法。对螺栓在紧固、松动后的扭矩-预紧力、伸长量-预紧力分别进行了校核计算,得出了用螺栓拉伸机松动比用扭矩扳手紧固产生的预紧力小是造成施工现场不能用螺栓拉伸机松动由扭矩扳手紧固的人孔法兰螺栓现象的根本原因。最后建议,无论采用扭矩控制法还是伸长量控制法,应在保证SG人孔法兰密封性的前提下,通过校核螺栓预紧力,使扭矩控制法和伸长量控制法产生的螺栓预紧力相互匹配,以确保无论采用哪一种螺栓紧固方法都能满足螺栓的拆装需要。     

数控机床进给系统摩擦动力学分析

提出了一种机床进给系统摩擦力检测实验方法。通过测量电机的输出扭矩,间接测量床负载受到的摩擦力矩,建立了机床进给轴的数模型。通过动力学仿真研究了系统在匀低速运行摩擦对位置和速度的影响,分析了机床在不同低运行时,摩擦对运行效果的影响,确定了“低速”的体范围。将仿真结果与实验结果进行比较,分析偏差产生的原因。     

如何组织设备预修工作

设备预修制是有计划地在规定的日期内对工厂一 切机器设备进行维护、修理和检查(包括大,中,小修理)的制度。 设备在日常工作中,由於摩擦力或长期的运转,不 可避免的要产生零件的磨损,这是一种自然磨损,其结果将引起设备精度的减低或使个别零件失去作用,致使整个设备停歇。 设备在日常工作中,它的润滑、冷却、安全、动力等系统以及操纵调整和紧固等装置,常由於日久而失去原有的正常状态,如油管闭塞,手把松动等,这些现象正是促使设备发生故障而召致损坏或停歇的原因。 设备预修制正是为了在事前消除以上两种致病原因,从而保证设备经常的运转。…     

新型联轴器

新型联轴器的工作原理是依靠摩擦力传动扭矩。而且具有超负荷时“打滑”的安全保险作用。新型联轴器所传动扭矩的大小是可以随时调节的。调节方法:拧紧或松开联轴器端面的6个内六角螺钉8(图示)。即通过拧紧螺钉,使外圆锥环1和内圆锥环4靠近(加大摩擦力)和远离(减小摩擦力)。     

新型纯扭矩加载器的设计及结构优化

针对现有精密小扭矩传感器扭矩标定中存在的精度低、误差大、所加载的扭矩非纯扭矩等问题,研制出可以加载纯扭矩的加载器(加载范围为0～16.068N·m),该装置采用柔性铰链结构作为导轨机构,只需要加载一个力即会产生一个平衡对称的纯扭矩.柔性铰的尺寸参数和位置参数是该装置设计的关键,通过采用ANSYS软件对初始设计参数进行结构优化计算,确定了其最优参数.通过实验分析,验证了所设计的新型纯扭矩加载器的精度、线性度和重复性均优于传统的扭矩加载机构,且具有结构简单、制作方便的优点,可以在工程实际中使用.     

一种新型负载模拟器摩擦力矩与温度场研究

新型负载模拟器利用摩擦加载原理实现对舵机的力矩加载。利用摩擦磨损理论,提出修正的摩擦力矩计算公式,对圆环式、圆盘式、扇形式摩擦副的摩擦力矩进行计算与讨论,初步证明了修正模型的合理性;基于热力学理论,采用有限元软件(ABAQUS)分析摩擦盘瞬态温度场,结果表明,压力、转速的升高都会使摩擦盘温度迅速升高,同时造成高温区更加集中;相比压力而言温度场对转速变化更加敏感;扇形式结构和圆环式结构仿真结果表明扇形式更适合小力矩加载。     

Thermodynamic Differences of Different Friction Pairs in a Multidisc Clutch Caused by Spline Friction: Numerical Simulation and Experimental Verification

Abstract

Considering the spline friction, the dynamic model of a multidisc clutch is established that permits the calculation of the contact pressure and friction torque acting at each friction surface; the thermal model is then developed to investigate the temperature difference between different friction pairs. The corresponding test bench is established, where the effect of inertia on the torque error is analyzed in detail. The simulated and measured results are compared to validate the numerical model and confirm the existence of spline friction. The results indicate that spline friction can lead to the attenuation of contact pressure on friction pairs along the axial direction. Therefore, there exists a significant temperature gradient in the axial direction, and the maximum temperature appears in the second separate plate near the piston. Moreover, the friction torque of a single pair decreases along the axial direction. Thus, as the number of friction pair increases, the total friction torque increases nonlinearly, and the average torque of single friction pair decreases gradually.     

Mathematical model and experiment validation of fluid torque by shear stress under influence of fluid temperature in hydro-viscous clutch

The current design of hydro-viscous clutch（HVC） in tracked vehicle fan transmission mainly focuses on high-speed and high power. However, the fluid torque under the influence of fluid temperature can not be predicted accurately by conventional mathematical model or experimental research. In order to validate the fluid torque of HVC by taking the viscosity-temperature characteristic of fluid into account, the test rig is designed. The outlet oil temperature is measured and fitted with different rotation speed, oil film thickness, oil flow rate, and inlet oil temperature. Meanwhile, the film torque can be obtained. Based on Navier-Stokes equations and the continuity equation, the mathematical model of fluid torque is proposed in cylindrical coordinate. Iterative method is employed to solve the equations. The radial and tangential speed distribution, radial pressure distribution and theoretical flow rate are determined and analyzed. The models of equivalent radius and fluid torque of friction pairs are introduced. The experimental and theoretical results indicate that tangential speed distribution is mainly determined by the relative rotating speed between the friction plate and the separator disc. However, the radial speed distribution and pressure distribution are dominated by pressure difference at the lower rotating speed. The oil film fills the clearance and the film torque increases with increasing rotating speed. However, when the speed reaches a certain value, the centrifugal force will play an important role on the fluid distribution. The pressure is negative at the outer radius when inlet flow rate is less than theoretical flow, so the film starts to shrink which decreases the film torque sharply. The theoretical fluid torque has good agreement with the experimental data. This research proposes a new fluid torque mathematical model which may predict the film torque under the influence of temperature more accurately.     

Novel approach to studying the influence of surface structure on tribological properties of carbon fabric reinforced phenolic composites

In order to make clear the engagement behavior, the numerical research is conducted to explore the influence of interface pressure on the tribological properties of carbon fabric reinforced phenolic composites. It is found that the dynamic friction torque is a linear function of interface pressure by curve fitting. And then the coefficient of dynamic friction is derived as an inverse proportional function of interface pressure. To demonstrate the results, the contact model is presented based on Gaussian surface asperity height distribution and the assumption of elastic deformation. Meanwhile, the asperity contact area is considered as the critical factor.     

基于虚拟仪器的挺柱体组件摩擦转矩测量研究

针对国内挺柱体组件摩擦转矩人工检测的现象,设计了一种挺柱体组件摩擦转矩间接自动测量方法,并用虚拟仪器实现了摩擦转矩数学模型中载荷、转速和摩擦转矩的实时显示。实测结果证明,此方法可行。     

高压旋转组合密封试验装置设计与研究

针对旋转组合密封性能检测问题,设计完成可对直径100 mm的轴用旋转组合密封圈进行密封性能试验的装置。采用PLC控制驱动,实现系统数据采集和压力转速自动调节控制,可对密封件在不同转速、压力下的扭矩、泄漏量等指标进行测试。利用该试验装置对某型号旋转组合密封件进行试验研究,试验结果表明：在定转速情况下,组合密封启动摩擦力矩随压力增加而增加;相同压力下,组合密封圈在低转速情况下,摩擦力矩随转速增加而增加,当转速增加到一定数值后,摩擦力矩增幅出现下降趋势。同时测试结果也表明该装置功能完善,操作简便,自身回转阻力小,在高压下工作稳定可靠。     

Three dimensional thermal mechanical coupled simulation during hot rolling of aluminium alloy 3003

Rolling passes of a pass schedule supplied by an aluminium company and containing reliable measured data of roll load and torque is considered. Percentage reductions range from 6% to 20% and are analysed by a commercial thermo-mechanical coupled FEM program FORGE3 V5.3. An inverse analysis method is adopted to match the calculated rolling force and torque with the measured rolling force and torque by treating the friction law and the friction coefficient as free parameters. Three widely accepted friction laws are investigated; Tresca friction, Coulomb friction and viscoplastic friction. The use of viscoplastic friction is shown to yield both more reliable and more accurate results than other models. Significantly the friction coefficient can be traced to remain constant throughout the pass schedule of the breakdown rolling. The contact pressure distribution is then studied with different thickness reductions and compared with published experimental results. The predicted and experimental agreement is such that the load calculation can be regarded as satisfactory. Acceptable agreement is also obtained with the measured torque values. The distribution of equivalent strain, temperature and the stress in the roll gap and the lateral profile are discussed.     

考虑正负转速差的湿式离合器带排扭矩损失研究

基于某湿式多片式离合器的实际结构与带排扭矩损失的产生机制,分析在正负转速差下油液对摩擦片油槽作用的不同以及对带排扭矩损失的影响,并通过仿真与试验获得正负转速差下带排扭矩损失的变化规律。仿真与试验结果表明:在负转速差下,由于摩擦片的转速较大,其油槽侧面产生的动压力也较大,带排扭矩损失也相比正转速差时要大。对离合器带排扭矩损失在正负转速差下对自动变速箱换挡过程换挡力的影响进行分析,发现负转速差下需要的换挡力比正转速差下的换挡力大,因此负转速差下有换挡困难的风险。     

表面空气对制动力矩的影响

研究了摩擦表面流动的空气对摩擦力的影响。通过制动模拟试验，对4种不同表面形状衬片的制动力矩-时间曲线的波动幅度进行了比较分析，根据摩擦表面中流动空气的不同工作特性，建立了相应的简图进行了详细的说明：试验结果表明：在摩擦热的作用下，表面空气的温度升高，气压增加，从而削弱了工作载荷对表面的作用力，使摩擦力矩产生波动。随着制动速度的下降，热空气对摩擦力矩波动的影响减小。制动时，摩擦盘带入表面的空气越多，空气对摩擦力矩的影响就越大；摩擦表面存留的热空气越多，热空气对摩擦力矩的影响就越大。     

微型灵敏球轴承新型结构金属实体保持架的研制

研制新型结构轴承保持架是解决目前微型灵敏轴承摩擦力矩大的关键之一。完成了具有独特的自锁球结构的微型灵敏球轴承新型结构金属实体保持架的设计,阐述了其加工工艺、关键技术、检测手段及轴承装配方法,这种结构保持架的研制在微型灵敏轴承减摩研究方面具有重要意义。