Force distribution for a flat belt drive with a concentrated contact load

An equation based on the classical Euler formula is derived to investigate the normal and tangential belt force distribution of a flat belt drive when a concentrated contact load is applied on the pulley. This loading condition occurs in an abrasive belt grinding. The belt force equation presented in this paper has a constant coefficient of friction. Analytical results show good agreement with the experimental results and the authors' previous work, which is based on a surface model of the belt friction face with a varying coefficient of friction. The equation developed from the Euler formula is suggested for practical design due to its sufficient accuracy and simplicity.     

An approach for transition correlation of laminar pulsatile pipe flows via frictional field characteristics

Transition of laminar pulsatile pipe flow into turbulence is one of the current research topics in flow dynamics. Despite the existence of a considerable number of theoretical and experimental studies, the physical mechanism of transition is not well defined. Furthermore, there is almost no information on the start and the end of the transition in terms of pulsatile flow parameters.

In this paper, an approach which consists of attempts to correlate the governing flow parameters is presented to reveal the transition process with particular emphasis on the frictional field. The experimental data collected in slightly compressible, Newtonian, one-dimensional laminar pulsatile pipe flow without a flow reversal were compiled for this purpose. The common oscillation parameters, dimensionless frequency parameter and velocity amplitude ratio A₁ were the main variables of the experimental study covering the ranges of and 0.05≤A₁≤0.8. The time history of local static pressure gradient and axial velocity field were accumulated and the data were expressed through pulsatile flow, instantaneous λ_u(t) and time-averaged λ_u,ta friction factors using momentum-integral equation. A reference friction factor ratio λ_R, whose definition was based on the concept of steady flow friction was introduced. The start and the end of transition were predicted through the functional relationships of λ_R with time-averaged and oscillating Reynolds numbers, Re_ta and Re_os by means of a trial–error procedure. The proposed correlations and determined approximate critical limits of transition are only valid in the corresponding ranges of 2000≤Re_ta≤60 000, 620≤Re_os≤18 800 and the analysis is open to discussion.     

Experimental investigation on the effect of tangential force on wear and rolling contact fatigue behaviors of wheel material

The study aims to explore the effect of tangential force on wear and rolling contact fatigue (RCF) behaviors of wheel material using a JD-1 wheel/rail simulation facility. The normal, tangential and lateral forces between the wheel/rail rollers are controlled, and the magnetic power brake was used to generate the tangential forces (16–330 N). The results indicate that the surface hardness and wear loss of wheel rollers increase with the tangential force increasing. The surface cracks mouths are perpendicular to the resultant directions of the frictional forces. There are visible secondary cracks and multilayer cracks and the interlayer material of multilayer cracks are easy to break. The compositions of wear debris consist of Fe₂O₃, Fe₃O₄ and iron.     

金属推块V-带型CVT的研究--部分Ⅲ：金属推块上的作用力

已经用试验实测了稳定工况下推块的压缩力和环的拉力。在以前的工作中已经概要地说明了这种带型的特殊的传动机理。本文采用最近开发设计的推块测量在稳定工况下其他同时作用于推块上的力,这些力是推块和环之间的摩擦力,推块和带轮间的法向力,推块和带轮之间径向和切向摩擦力。根据新的试验数据来详细叙述金属推块Ｖ－带型ＣＶＴ的传动机理。本文着重提出以下结论。（１）在所有工况,推块和环结合的结合点在带轮上具有一个较大的     

Fluid forces in short squeeze-film damper bearings

This paper has studied influences of fluid inertia on fluid velocity profiles and provided an axial inertia velocity profile for short squeeze film damper bearings (SFDs) using as a starting point a simplified Navier–Stokes equation. The velocity profile reasonably represents influences of fluid inertia on fluid flow. From the inertia velocity profile, present work develops new theoretical models for fluid forces in cylindrical short SFDs. Published experimental work confirms that the new models for fluid forces are better than traditional short-SFD theory, especially for tangential force. The new models show that the damping coefficient for 2π film is related to fluid inertia.     

高速精密磨削9CrWMn冷作模具钢的磨削力和比磨削能

分析了高速精密磨削9CrWMn冷作模具钢的机理,采用DEFORM软件对高速磨削模具钢9CrWMn过程进行了磨削力仿真。使用高精密高速平面磨床对模具钢9CrWMn进行了高速精密磨削试验,并在线测量了多种工况下的磨削力。结果表明:在其他两组工艺参数不变时,随着工件进给速度增加,磨削力特别是法向磨削力会增大近45%;法向磨削力和切向磨削力随着砂轮的线速度上升而下降,法向磨削力下降近33%;磨削深度对磨削力影响较大,大的磨削深度对法向磨削力的影响尤其显著,可使法向磨削力增大近100%。分析了磨削工艺参数对比磨削能的影响规律,结果显示:随着磨削深度和工件进给速度的增大,比磨削能呈比较明显的下降趋势,符合磨削加工中的尺寸效应;随着砂轮线速度的增大,比磨削能呈上升趋势。最后,对高速磨削前后工件表面的微观形貌进行了对比分析,磨削力试验结果和仿真理论分析相一致。     

颗粒增强铝基复合材料铣削加工实验研究

使用K10硬质合金铣刀,在不使用冷却液的条件下,对A12024/SiCp复合材料进行铣削加工实验,研究切削参数和颗粒尺寸对表面质量、切削力、刀具磨损的影响.研究表明,随着增强颗粒尺寸的增大,表面变粗糙、切削力增大和刀具磨损加重;在不同的切削条件下,法向力均大于切向力.随着切削用量的增大,铣削力呈增大趋势,其中,吃刀量对铣削力的影响最大,切削速度的影响最小;加工表面上存在凹坑、颗粒突起和基体材料涂敷等缺陷,表面粗糙度随着颗粒尺寸增大而增大,随着切削速度的提高而减小.     

水平转弯带式输送机结构参数分析

讨论了水平转弯带式输送机转弯处的受力状态,建立了三维力学模型,利用坐标变换法将所受各力向各主坐标轴进行分解,建立了各坐标轴方向上的平衡方程,由此导出了运行阻力计算公式,据此分析了影响运行阻力的因素,为更合理地设计水平转弯带式输送机提供了理论依据。     

On the theory of power transmission by a flat,elastic belt

Frictional power transmission from a pulley to a thin, flat, elastic belt is studied. The derivation of a new formula for the tension ratio $\text{T}{}_1\text{T}{}_2$ in the creep regime stems from the quasi-static equilibrium equations and includes the effects of belt elasticity, flexural rigidity and varying coefficient of friction along the contact arc. The dynamic coefficient of friction at any point on the contact arc is determinable from slip and tension measurements on an operating belt A simplified solution is found by utilization of experimental slip measurements reported by Grimmer and Thormann. A condition of constant tangential shear stress is consistent with these data. Euler's formula proves to be inconsistent with the test data. A solution in the slip regime is proposed that reduces to Eulerian form in the case of slip over the entire contact arc.     

带式输送机虚拟样机设计研究

创新地将虚拟样机技术运用于带式输送机设计,提出用有限的离散带块单元来仿真连续输送带的设计方法;通过带式输送机系统简化、3D样机建模、样机装配、施加载荷约束等设计步骤,最终建立了基于虚拟设计软件ADAMS的简化带式输送机虚拟样机;并对样机进行了起动和正常运行的工况模拟,其运动学和动力学结果和实际工况相符。     

多点驱动的上运带式输送机起动控制策略

从分析上运长距离多点驱动带式输送机起动过程的重要性入手,采用液粘软起动装置和液压自动拉紧装置对输送机的起动过程进行控制。带式输送机的起动方式分为开环和闭环2种,闭环加速曲线采用S形曲线,主、从驱动分别由速度环和电流环进行控制。该控制策略在实际应用中取得了比较满意的效果。     

A study of the effects of non-isothermal source conditions on the transfer of radiance temperatures in the temperature-wavelength domain from 180 to 30 000 μm K

The calibration of infrared pyrometers against a commercially available cylindroconical black-body system, operating in the range from 900 to 2900 K, forms the basis for the study presented in this paper.

The main features of the black-body system, in use at VSL, are briefly described. In practice, uniformity in temperature is difficult to achieve, especially at very high temperatures. For this reason, the effect of a non-uniform temperature distribution on the calibration accuracy was studied by model calculations, varying the relative temperature difference ΔT/T_b along the cylindrical wall of the cavity with respect to its bottom temperature T_b up to a maximum of 5%. Spectral emissivities = (λ, T_b) are calculated for a cylindro-conical geometry that approximates the real system. For some specific cases the effects for actually measured temperature distributions are also evaluated.

It is demonstrated that when transferring radiance temperatures from a lower wavelength (λ_s 0.6 μm), characterising the reference pyrometer, to the higher effective wavelength of the (spectral) infrared pyrometer to be calibrated (λ_x 6 μm), compensation of errors leads in general to a considerable reduction of the overall error, arising when neglecting the effect of departures from temperature uniformity, the reduction being more pronounced the higher the temperature.     

带式输送机胶带的纠偏

从物料、胶带、托辊3者的受力关系出发，分析了胶带跑偏的起因，阐述了各托辊的防跑偏原理及其适用性。     

基于虚拟样机的带传动动态特性分析

主要利用虚拟样机技术建立的简单带传动虚拟样机模型研究带传动在非临界状态下的特性,并通过对带传动虚拟样机模型的仿真分析,得到在非临界状态下带传动中的力、速度和加速度如何变化的曲线,通过分析得到了一些结果,并为进一步如何利用虚拟样机技术对带传动系统特性做深入研究的方式和方法进行了初步探讨.     

Analysis of asymmetrical effect of tension forces in conveyor belt on the idler roll contact forces in the idler housing

This paper analyses an impact of asymmetrical tension forces, which are occurring in the conveyor belt, on the contact forces in the guiding idlers. It describes causes of an increased wear-out of the conveyor belts due to an asymmetric tensioning of the transport belt. There were investigated five measuring points loaded with a symmetrical and asymmetrical tensioning of a specimen section of the pipe conveyor transport belt, using the Friedman test for the factor of asymmetry. The tension force determines also changes of the contact force layouts in the individually investigated idler rolls. A newly developed method was applied in order to identify states of the particular experimental phases for the process of the transport belt tensioning and relaxation. This method is based on differences of the contact force time behaviours. It is possible to present a hypothesis, taking into consideration the obtained results that a side slipping of the running conveyor belt is caused by the tension force asymmetry also on the real operational conditions.     

管状带式输送机胶带特性

管状带式输送机具有密闭输送、空间布置灵活、输送倾角大等特点,能满足清洁输送的环保要求,应用越来越多.胶带是管带输送机的核心部件之一,适当的横向刚性是保证胶带成圆管状的关键,其值与管径、带速、运量等有关.合理选择胶带的横向刚性对管带输送机平稳、低阻、经济和长周期运行至关重要.管带覆盖胶的选择则与输送的物料特性、环境工况等...     

复杂接触运动下非线性摩擦力的求解

提出了复杂接触运动下求解接触非线性摩擦力的数值轨迹跟踪方法,利用该方法对几种复杂接触运动下的非线性摩擦力进行了计算。计算结果表明:数值方法在分析二维接触椭圆运动时可以得到更准确的结果;计算接触面摩擦力时不能忽略法向运动与切向运动之间的相位差,该相位差对接触状态的转变、摩擦力的大小以及迟滞回线的形状都有很大的影响;对于接触面的三维运动,必须同时考虑法向运动与接触面内两个方向切向运动之间的耦合;数值轨迹跟踪方法可以方便地求解一维、二维以及三维接触运动下的非线性摩擦力,为求解带干摩擦阻尼结构的动态响应提供了一种实用算法。     

The effect of longitudinal tangential vibrations on friction and driving forces in sliding motion

The main purpose of the work has been to qualitatively and quantitatively analyse the influence of longitudinal tangential vibrations on friction and driving forces in a sliding motion. Computational models were developed and implemented in a combined Matlab-Simulink environment. Both the dynamic Dahl's and the Dupont's and classical Coulomb's friction models were used. The influence of vibration velocity amplitude on the friction force in the presence of tangential longitudinal vibrations and on reduction of the driving force in sliding motion was analysed. It revealed that the commonly accepted view that the reduction of the average friction force is a consequence of cyclic changes in the sign of the friction force vector, only when the amplitude of vibration velocity is greater than the sliding motion velocity, is erroneous. The phenomenon was also observed without any changes in the sign of friction force vector. The results of simulations were compared with experimental data obtained with the use of a test rig specifically designed for the work. The Dahl's friction model led to the best correlation.     

煤矿带式输送机可控液压制动系统研究

结合实际工况设计一种煤矿带式输送机可控液压制动系统,它和制动器组合成一套制动系统,能够实现煤矿带式输送机制动过程中速度和加速度在可控范围内,实现煤矿带式输送机的软制动.