Effect of operation parameters on thermal loading of wet brake discs. Part 1. Problem formulation and methods of study

A dimensionless heat problem which describes the three-dimensional transient temperature field in the friction pair of a multidisc wet brake with the radial arrangement of oil grooves is developed. A method for the multifactor study of the effect of operation parameters on the formation of the temperature field in brake discs under stationary friction conditions is proposed.     

Studying thermal state of friction pairs of multidisc brake

A dimensionless heat problem for a friction pair of a multidisc brake was formulated under conditions of a linear decrease in the friction power of discs with time. Thermal state of friction pairs of the multidisc brake under load and velocity conditions of the friction of the discs that simulate service brakings of a wheel tractor was experimentally and theoretically studied. The validity of a mathematical model of the temperature field in the discs of the brake has been experimentally confirmed and functional dependences of the maximum temperature of friction surfaces of the discs on values of the main performance parameters have been obtained.     

机车制动盘三维瞬态温度场与应力场仿真

基于三维循环对称有限元模型,提出了机车制动盘制动过程中温度场和应力场的计算方法。讨论了边界条件和各种相关参数的确定方法,尤其是机车整个制动过程中制动盘换热系数的计算方法。同时运用有限元软件ANSYS7进行了制动盘及相关部件三维瞬态温度场和应力场的仿真与分析。仿真结果表明:在制动开始阶段,制动盘迅速升温,高温区集中在制动盘摩擦面表层,最高温度达220℃;制动过程结束后,整个制动盘有一段较长时间的降温过程;制动盘系统各部分的最大热应力-时间曲线变化规律不一致,但均满足材料强度要求。仿真结果与实验数据相符,证明了该三维有限元模型及其温度场计算方法的正确性。     

摩擦块形状对制动盘摩擦温度及热应力分布的影响

列车制动产生的摩擦热在制动盘表面的分布与闸片结构密切相关,并影响到制动盘的耐热疲劳程度.基于实际应用的圆形、六边形、三角形3种形状摩擦块的制动闸片,利用有限元分析软件ABAQUS,模拟制动时制动盘的温度及热应力分布情况.结果显示:制动盘摩擦表面温度及热应力呈环形带状分布,沿周向变化不明显,在径向上分布的均匀程度差异较大;其变化程度与摩擦块形状和位置有关,摩擦块为圆形时,盘面的温差和热应力最小,摩擦块为三角形时,盘面的温差和热应力最大;摩擦块的位置分布影响到摩擦副接触弧长度,接触弧长度增加,对应的摩擦环带温度升高;各环带对应的接触弧长度偏差越小,制动盘温度越低,分布也越均匀.     

Friction Instability Induced by Corrosion of Gray Iron Brake Discs

This study examined the frictional force oscillation induced by the corrosion of brake discs when two different types of brake friction materials (low-steel and non-steel types) were used. Corrosion of the disc was carried out in an environmental chamber using burnished discs to simulate disc corrosion in a parked vehicle. The thickness of the oxide layers on the discs after corrosion was examined using non-contacting distance probes, and the change in brake torque was analyzed using a single-end brake dynamometer. The results showed that the oxide thickness on the disc was affected by the friction film on the burnished disc surface, and the friction force oscillation was closely related to the removal of the oxide layers while applying the brake. The low-steel friction material removed the oxide layer faster in the early stage than the non-steel friction materials so that it produced small oscillations in the friction force. However, the low-steel friction material increased the amplitude of the friction force in the later stage of the extended brake tests due to the excessive DTV (disc thickness variation). On the other hand, the non-steel friction material produced large friction force oscillations in the early stage with the amplitude decreasing in the later stage of brake application due to removal of the oxide film.     

多片全盘式液压制动器间隙自动补偿装置

在制动器控制系统中设置多片全盘式液压制协器装置，并通过合理的结构设计及参数确定，始终保持原设计的最佳间隙值，制动行程不会改变，也无须对制动器进行复杂的预调。     

High thermal diffusivity materials for railway brakediscs

Two high thermal diffusivity brake discs have been worn againsta metallic pad, a composite pad and a new ceramic pad. Thesediscs are composed of a friction track made of molybdenum orCu-2.5% Be alloy. Molybdenum was used in the form of a coatingsprayed on an aluminum-based disc or as a thin solid disc mechanically clamped onto an aluminum-based stand disc. Coatingadherence, friction coefficient, surface temperature and wearthickness loss were determined for a set of reduced-scale steelbrake discs during a continuous braking simulation. It is shownthat the solid molybdenum disc tested against the composite padinduces significant surface temperature decreases as opposed tosliding against the bare steel disc. The friction coefficient isstable and wear damage acceptable. However, the molydenumcoating performs unsatisfactorily as the large difference inthermal expansion coefficient between molybdenum and aluminuminduces disbonding and crazing of the coating. The aluminumtitanate pad/Cu-2.5Be disc brake system has demonstrated remarkable tribological performance, with a steady frictioncoefficient, a pad surface temperature about 60°C lower thanthat of a steel disc and low pad wear.     

摩擦副组合对摩擦磨损性能的影响

在1：1惯性力矩制动试验台上研究了两种不同石墨形态的铸铁制动盘与两种混杂纤维增强的酚醛基制动闸片配副时的摩擦磨损性能。结果表明，对于某一配方的制动闸片，使用灰口铸铁盘的摩擦副具有较高的摩擦系数，但制动盘表面温度较高，闸片磨损量较大；对于某一种制动盘，使用B配方制动闸片时，制动盘表面的温度较高，但闸片的磨损量较小；在所有四种组合中，B配方制动闸片与灰口铸铁盘配副的瞬时摩擦系数能够完全满足有关技术要求。     

On the nature of tribological contact in automotive brakes

The tribological contact in automotive brakes involves dry sliding contact at high speeds and high contact forces. The commonly used organic binder-type brake pad friction materials are extremely inhomogeneous and exhibit very low bulk strengths. Despite the low strength, the specific contact surfaces that form during the use render the pads very good friction and wear characteristics. This paper gives a general view of the contact situation of organic binder brake friction materials against cast iron discs, with special emphasis on many mechanisms for contact surface variations and the corresponding variations of the coefficient of friction.     

Friction and wear of sintered metallic brake linings on a C/C-SiC composite brake disc

The friction and wear of sintered metallic brake linings on a C/C-SiC composite brake disc were studied. This paper reports on the friction and wear properties of sintered metallic (MMC) brake linings, which appear to combine well with a C/C-SiC brake disc. The friction characteristics were examined with a dynamometer on two different commercial motorcycle brake systems, differing in terms of the brake caliper and the dimensions of the disc. The influence of the components, such as graphite, and the abrasives in the metallic matrix on the formation of the friction layer was investigated using a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). The friction layer formed on the pad's sliding surface by oxidation wear, which consisted mostly of iron and copper oxides, was confirmed. The friction properties of the sintered metallic brake pads were determined and related to the composition and structure of the brake lining. This investigation of the friction characteristics of a brake couple comprising (MMC) brake linings and a C/C-SiC composite disc will increase our understanding of this material, which works in a completely different way to classical brakes based on metallic discs.     

Neural network prediction of disc brake performance

An automotive brake's performance results from the complex interrelated phenomena occurring at the contact of the friction pair. These complex braking phenomena are mostly affected by the tribochemical properties of the friction material's ingredients, the brake disc properties, and the brake's operating regimes. In this paper, the synergistic effects of the friction material's properties, defined by its composition and manufacturing conditions, and the brake's operating regimes on the disc brake factor C variation have been modelled by means of artificial neural networks. The influences of 26 input parameters, determined by the friction material composition (18 ingredients), its manufacturing conditions (5 parameters), and the brake's operating regimes (3 parameters) on the brake factor C variation, have been predicted. The neural model of the disc brake cold performance has been developed by training 18 different neural network architectures with the five different learning algorithms. The optimal neural model of disc brake operation has been shown to be valid for predicting the brake factor C variation of the cold disc brake over a wide range of brake's operating regimes and for different types of friction material.     

Investigation of thermo-structural behaviors of different ventilation applications on brake discs

One of the most common problems related to brake discs is overheating, which negatively affects braking performance especially under the continuous braking conditions of vehicles. Ventilation applications on brake discs can significantly improve the brake system performance by reducing the heating of the discs. In this study, the thermal behaviors of ventilated brake discs using three different configurations were investigated at continuous brake conditions in terms of heat generation and thermal stresses with finite element analysis. The results were compared with a solid disc. Heat generation on solid brake discs reduced to a maximum of 24% with ventilation applications. The experimental study indicated finite element temperature analysis results in the range between 1.13% and 10.87%. However, thermal stress formations were higher with ventilated brake discs in comparison to those with solid discs.     

基于马尔可夫链的飞机刹车片检查时间确定

为结合飞机实际运行工况,科学合理地制定刹车片检查时间,笔者提出一种基于马尔可夫链理论的预测模型。以某一机群刹车片检查时间确定为实例,分别论述了刹车片磨损状态的划分,转移概率矩阵的构造与估计,并对该机群刹车片磨损状态进行了预测,其预测结果与实际检查情况较吻合。根据刹车片磨损状况的预测结果,制定了该机群在实际运行工况下的刹车片检查时间。实际运行情况表明,所制定的刹车片查检时间可行、有效。     

Braking performance and noise in excessive worn brake discs coated with HVOF thermal spray process

In this paper, two excessive worn brake discs of a light commercial vehicle were coated with High velocity oxygen fuel (HVOF) thermal spray process for reuse. The coated discs were compared with uncoated Original equipment manufacturer (OEM) D1 disc in terms of braking performance and noise. The D2 disc was coated with tungsten-carbide-cobalt (88 %WC-12 %Co) powder and NiCr (80/20) binder, and 500 Gm thick coating was obtained. The D3 disc was coated with Colmonoy-88 (Ni-W-Cr-B-Si) powder and NiCr (80/20) binder and 600 Gm thick coating was obtained. Several test procedures (e.g. bedding, vibration, and structural-strength tests) was applied to three discs using inertia brake dynamometer. Results showed that coated D2 disc with tungsten carbide cobalt provided lower brake noise and higher brake performance compared with OEM disc. Considering the coefficient of friction and temperature, coated D3 disc has approximately equal braking performance with OEM D1 disc despite the high braking noise value.     

Thermal behavior of full and ventilated disc brakes of vehicles

Braking is a process which converts a vehicle’s kinetic energy into mechanical energy which must be dissipated in the form of heat. During the braking phase, the frictional heat generated at the interface of the disc and pads can lead to high temperatures. This phenomenon is even more important than the tangential stress. The relative sliding speeds during contact are also important. The prediction of surface temperature for a brake rotor is regarded as an important step in studying brake system performance. The frictional heat generated on the rotor surface can influence excessive temperature rise which, in turn, leads to undesirable effects such as thermal elastic instability (TEI), premature wear, brake fluid vaporization (BFV) and thermally excited vibrations (TEV). The objective of this study is to analyze the thermal behavior of the full and ventilated brake discs of the vehicles using computing code ANSYS. The modeling of the temperature distribution in the disc brake is used to identify all the factors and the entering parameters concerned at the time of the braking operation, such as the type of braking, the geometric design of the disc and the material used. The results obtained by the simulation are satisfactory compared to those of the specialized literature.     

Analysis of thermomechanical phenomena in multidisc clutches and brakes

The paper presents a model of transient thermomechanical phenomena occurring in a pack of friction discs of a multidisc wet clutch or a brake. Account is taken of the couplings between phenomena appearing on various friction surfaces. Numerical methods permitting an effective investigation of these are described.

Results of calculations are presented for the case when the thermoelastic instability effect appears. A mechanism for the growth of non-uniformities in normal pressure distributions on friction surfaces as well as couplings between phenomena occurring on various surfaces are discussed. It is also shown that the phenomena arising on friction surfaces strongly affect the thermal stresses inside the discs.     

Cellular automata method for macroscopic surface and friction dynamics in brake systems

The friction dynamics in the boundary layer of a brake system is closely linked with the growth and the destruction of typical structures on the brake pad. These processes are caused by an interaction of friction and wear and determine the (as well measured) time-dependence of global parameters, such as the friction coefficient μ or the temperature. Based on the simulation with a set of differential equations, this equilibrium of flow has also already been described with a cellular-automaton-discretization. This paper will show new results and fundamental conclusions with respect to the surface topography dynamics and the friction behaviour of a brake system.     

Numerical simulation of operation heat modes of multidisc oil-cooled vehicle brake. Part 1. Heat problem solution

The paper considers the operating heat modes of multidisc oil-cooled vehicle brakes under single and multiple braking, as well as under deceleration over a long downgrade. The initially boundary-value heat problem for the given operating modes of the brake is formulated and solved by the finite-element method. The regularities of formation of nonstationary temperature fields both on the contact surfaces and in the bulk of the brake friction elements are obtained for preset braking modes. The dependences are obtained for the maximal contact surface temperature on the metal counterbody and frictional material vs. the load and velocity parameters of vehicle motion. A method for forecasting the critical operating regimes of multidisc oil-cooled brakes is proposed for the given operation conditions of the vehicle.     

Neural network prediction of brake friction materials wear

Wear of brake friction materials depends on many factors such as temperature, applied load, sliding velocity, properties of mating materials, and durability of the transfer layer. Prediction of friction materials wear versus their formulation and manufacturing conditions in synergy with brakes operating conditions can be considered as a crucial issue for further friction materials development. In this paper, the artificial neural network abilities have been used for predicting wear of the friction materials versus influence of all relevant factors. The neural model of friction materials wear has been developed taking into account: (i) complete formulation of the friction material (18 ingredients), (ii) the most important manufacturing conditions of the friction material (5 parameters), (iii) applied load and sliding velocity of the friction material both represented by work done by brake application, and (iv) brake interface temperature.     

制动过程中闸片材料与制动盘温度关系试验研究

为探讨碳/陶制动盘与不同闸片材料的匹配性,对碳/陶制动盘分别与碳/陶复合闸片、铜基粉末冶金闸片和铁基粉末冶金闸片组成的摩擦副进行制动试验,研究了在制动过程中盘面各点瞬时温度、最高温度、闸片温度与制动工况的关系。结果表明：碳/陶制动盘与碳/陶复合闸片摩擦副温度及温度梯度均高于其他2种摩擦副,其温度梯度在低速制动时随压力的增加而明显增加,当制动速度较高时,温度梯度并没有随压力的增加而增加;对于碳/陶制动盘与铜基和铁基粉末冶金闸片摩擦副,随制动速度和压力的提高,盘面温度梯度变化不明显。原因在于材料导热性和起始摩擦因数决定了盘面的散热能力和制动功率,碳/陶制动盘与碳/陶复合闸片摩擦副因较高的起始摩擦因数以及较低的导热性,其制动功率高和散热能力低,导致盘面温度持续升高。