Thermal fatigue and wear of compacted graphite iron brake discs with various thermomechanical properties

The increase in payload capacity of trucks has heightened the demand for cost-effective yet high performance brake discs.In this work,the thermal fatigue and wear of compacted graphite iron brake discs were investigated,aiming to provide an experimental foundation for achieving a balance between their thermal and mechanical properties.Compacted graphite iron brake discs with different tensile strengths,macrohardnesses,specific heat capacities and thermal diffusion coefficients were produced by changing the proportion and strength of ferrite.The peak temperature,pressure load and friction coefficient of compacted graphite iron brake discs were analyzed through inertia friction tests.The morphology of thermal cracks and 3D profiles of the worn surfaces were also discussed.It is found that the thermal fatigue of compacted graphite iron discs is determined by their thermal properties.A compacted graphite iron with the highest specific heat capacity and thermal diffusion coefficient exhibits optimal thermal fatigue resistance.Oxidization of the matrix at low temperatures significantly weakens the function of alloy strengthening in hindering the propagation of thermal cracks.Despite the reduced hardness,increasing the ferrite proportion can mitigate wear loss resulting from low disc temperatures and the absence of abrasive wear.

Sustainable Biocomposites Materials for Automotive Brake Pad Application:An Overview

Research into converting waste into viable eco-friendly products has gained global concern.Using natural fibres and pulverized metallic waste becomes necessary to reduce noxious environmental emissions due to indiscriminately occupying the land.This study reviews the literature in the broad area of green composites in search of materials that can be used in automotive brake pads.Materials made by biocomposite,rather than fossil fuels,will be favoured.A database containing the tribo-mechanical performance of numerous potential components for the future green composite was established using the technical details of bio-polymers and natural reinforcements.The development of materials with diverse compositions and varying proportions is now conceivable,and these materials can be permanently connected in fully regulated processes.This explanation demonstrates that all of these variables affect friction coefficient,resistance to wear from friction and high temperatures,and the operating life of brake pads to varying degrees.In this study,renewable materials for the matrix and reinforcement are screened to determine which have sufficient strength,coefficient of friction,wear resistance properties,and reasonable costs,making them a feasible option for a green composite.The most significant,intriguing,and unusual materials used in manufacturing brake pads are gathered in this review,which also analyzes how they affect the tribological characteristics of the pads.

A numerical method for the simulation of freight train emergency braking operations based on the UIC braked weight percentage

The present paper shows the development of a strategy for the calculation of the air brake forces of European freight trains. The model is built to upgrade the existing Politecnico di Torino longitudinal train dynamics(LTD) code LTDPoliTo, which was originally unable to account for air brake forces. The proposed model uses an empirical exponential function to calculate the air brake forces during the simulation, while the maximum normal force on the brake friction elements is calculated according to the indication of the vehicle braked weight percentage.Hence, the model does not require to simulate in detail the fluid dynamics in the brake pipe nor to precisely know the main parameters of the braking system mounted on each vehicle. The model parameters are tuned to minimize the difference between the braking distance computed by the LTDPoliTo code and the value prescribed by the UIC544-1 leaflet in emergency braking operations. Simulations are run for different configurations of freight train compositions including a variable number of Shimmns wagons trailed by an E402B locomotive at the head of the train, as suggested in a reference literature paper. The results of the proposed method are in good agreement with the target braking distances calculated according to the international rules.

A simplified pneumatic model for air brake of passenger trains

Braking system performance is relevant for both railway safety and network optimization. Most trains employ air brake systems;air brake systems of freight trains mostly cannot achieve a synchronous application of brake forces, which is usually customary for passenger trains. The paper generalizes a previous air brake pneumatic model to passenger trains and describes the needed modifications. Among them, the way the pressure reduces in the brake pipe is generalized. Moreover, this paper reports an analytical bi-dimensional function for calculating the nozzle diameter equivalent to the electro-pneumatic(EP) or the electronically controlled pneumatic(ECP)brake valve as a function of the wagon length and the time to vent the brake pipe locally. The numerical results of the new model are compared against several experimental tests of high-speed passenger trains of Trenitalia, namely ETR500 and ETR1000. The model is suitable to be integrated into the UIC software TrainDy, aiming to extend its computational field to passenger trains and to simulate the safety of trains during a recovery.

Blended Regenerative Anti-Lock Braking System and Electronic Wedge Brake Coordinate Control Ensuring Maximal Energy Recovery and Stability of All-Wheel-Motor-Drive Electric Vehicles

ABS is an active safety system which showed a valuable contribution to vehicle safety and stability since it was first introduced. Recently, EVs with in-wheel-motors have drawn increasing attention owing to their greatest advantages. Wheels torques are precisely and swiftly controlled thanks to electric motors and their advanced driving techniques. In this paper, a regenerative-ABS control RABS is proposed for all-in-wheel-motors-drive EVs. The RABS is realized as a pure electronic braking system called brake-by-wire. A coordination strategy is suggested to control RABS compromising three layers. First, wheels slip control takes place, and braking torque is calculated in the higher layer. In the coordinate interlayer, torque is allocated between actuators ensuring maximal energy recovery and vehicle stability. While in the lower layer, actuator control is performed. The RABS effectiveness is validated on a 3-DOF EVSimulink model through two straight-line braking manoeuvres with low and high initial speeds of 50 km/h and 150 km/h, respectively. Both regular and emergency braking manoeuvres are considered with ABS enabled and disabled for comparison. Simulation results showed the high performance of the proposed RABS control in terms of vehicle stability, brake response, stopping distance, and battery re-charging.

Typical faults and safety analysis of brake controller for AC locomotive

Purpose–The brake controller is a key component of the locomotive brake system.It is essential to study its safety.Design/methodology/approach–This paper summarizes and analyzes typical faults of the brake controller,and proposes four categories of faults:position sensor faults,microswitch faults,mechanical faults and communication faults.Suggestions and methods for improving the safety of the brake controller are also presented.Findings–In this paper,a self-judgment and self-learning dynamic calibration method is proposed,which integrates the linear error of the sensor and the manufacturing and assembly errors of the brake controller to solve the output drift.This paper also proposes a logic for diagnosing and handling microswitch faults.Suggestions are proposed for other faults of brake controller.Originality/value–The methods proposed in this paper can greatly improve the usability of the brake controller and reduce the failure rate.

Dynamic mechanical characteristics of NdFeB in electromagnetic brake

With the continuous development of artillery,the disadvantages of hydraulic recoil brakes gradually appear.At the same time,the appearance of high-performance Nd Fe B permanent magnet makes it possible to apply electromagnetic braking technology to recoil mechanism.In this paper,prototype tests of a certain artillery were carried out to verify the feasibility of the electromagnetic brake(EMB)and obtain the electromagnetic braking force.Due to the brittleness of Nd Fe B,in order to eliminate the worry about the safety of EMB,SHPB experiments of Nd Fe B were carried out.Then,based on the assumption of uniform crack distribution,the law of crack propagation and damage accumulation was described theoretically,and the damage constitutive model suitable for brittle materials was proposed by combining the Zhu-Wang-Tang(ZWT)equation.Finally,the numerical simulation model of the artillery prototype was established and through calculation,the dynamic mechanical characteristics of Nd Fe B in the prototype were analyzed.The calculation results show that the strength of Nd Fe B can meet the requirements of the use in the working process.From the perspective of damage factor,the damage value of the permanent magnet on the far right is larger,and the damage value of the inner ring gradually decreases to the outer ring.

An approach for simulating the air brake system of long freight trains based on fluid dynamics

Air brake systems are critical equipment for railway trains, which affects the running safety of the trains significantly. To study air braking characteristics of long freight trains, an approach for simulating air brake systems based on fuid dynamics theory was proposed. The structures and working mechanisms of locomotive and wagon air brakes are introduced, and mathematical models of the pipes, brake valves, reservoirs or chambers, cylinders, etc., are presented.Besides, the dynamic motions of parts in the main valve are considered. The simulation model of the whole air brake system is then formulated, and the solving method based on the finite-difference method is used. New efficient pipe boundary conditions without iterations are developed for brake pipes and branch pipes, which can achieve higher computational efficiency. The proposed approach for simulating the air brake system is validated by comparing with published measured data. Simulation results of different train formations indicate that models that consider the dynamic behavior of brake pipes are recommended for predicting the characteristics of long trains under service braking conditions.

Analysis of a Cashew Shell and Fly Ash Rich Brake Liner Composite Material

Hybrid materials collected from organic and inorganic sources,which are traditionally used as brake lining materials,generally include fly ash,cashew shell powder,phenolic resins,aluminium wool,barites,lime powder,carbon powder and copper powder.The present research focuses on the specific effects produced by fly ash and aims to provide useful indications for the replacement of asbestos due to the health hazards caused by the related fibers.Furthermore,the financial implications related to the use of large-volume use of fly ash,lime stone and cashew shell powder,readily available in most countries in the world,are also discussed.It is shown that many manufacturing and automotive industries,which are currently experiencing difficulties in meeting the increasing demand for brake lining material,may take advantage from the proposed solution.

A trailer car dynamics model considering brake rigging of a high-speed train and its application

Brake systems are essential for the speed regulation or braking of a high-speed train.The vehicle dynamic performance under braking condition is complex and directly affects the reliability and running safety.To reveal the vehicle dynamic behaviour in braking process,a comprehensive trailer car dynamics model(TCDM)considering brake systems is established in this paper.The dynamic interactions between the brake system and the other connected components are achieved using the brake disc-pad frictions,brake suspension systems,and wheel-rail interactions.The force and motion transmission from the brake system to the wheel-rail interface is performed by the proposed TCDM excited by track irregularity.In addition,the validity of TCDM is verified by experimental test results.On this basis,the dynamic behaviour of the coupled system is simulated and discussed.The findings indicate that the braking force significantly affects vehicle dynamic behaviour including the wheel-rail forces,suspension forces,wheelset torsional vibration,etc.The dynamic interactions within the brake system are also significantly affected by the vehicle vibration due to track irregularity.Besides,the developed TCDM can be further employed to the dynamic assessment of such a coupled mechanical system under different braking conditions.

Assessment of Asbestos Exposure Associated with a Brake Grinder

The wear patterns for drum-style automotive brakes tend to enlarge internal drum diameters. Such enlargement is most profound when used brake drums are machined to restore the metal friction surfaces. Specialized arc grinding machinery has been used to match replacement shoe-style brake friction materials to enlarged drums. The process of arc grinding removes friction material, thereby producing dust. When organic-style friction materials contained asbestos, use of arc grinding machinery posed an asbestos fiber exposure risk to operators and proximate personnel. The manufacturers of arc grinding machinery have incorporated local exhaust ventilation systems designed to capture and remove this dust at the point of grinding contact and propel this dust into collection bags or other systems. This research was designed to evaluate the dust capture and retention characteristics of a specific arc grinder product, when used to custom grind asbestos-containing brake friction materials. A Bear Model 1420 automotive brake shoe arc grinder was the subject of this study. During two separate but consecutive test sessions, newly relined sets of shoe-style automobile brake friction materials were precision ground. Both area and personal air samples were collected throughout each testing session. This work took place within a closed and unventilated metal building, with total interior volume of 2500 m3. Collected air samples were analyzed using phase contrast microscopy (PCM) and transmission electron microscopy (TEM). The results of analysis using PCM for personal samples (n = 6) ranged from <0.044 to 0.055 fibers per cc (f/cc) (mean 0.05). Follow-up analysis of these personal samples using TEM indicated asbestos-adjusted PCM exposures ranging from <0.0074 to 0.055 f/cc (mean ≤ 0.041). Area air samples, taken at distances ranging from 1.5 to 9 meters from the arc grinder (n = 12), showed asbestos-adjusted PCM concentrations ranging from <0.0075 to 0.041 f/cc (mean ≤ 0.017). The process of custom arc grinding shoe-style, asbestos-containing brake friction materials can cause exposure to airborne asbestos fibers. However, when done using properly equipped arc grinding machines, such exposures are not expected to exceed the current occupational exposure limits for asbestos of 0.1 f/cc 8-hour time-weighted average (TWA) or 1.0 f/cc 30-minute average.

星形超曲面上Hamilton系统Brake轨道的多重存在性

研究Hamilton系统具有固定能量的brake轨道的个数问题.在适当条件下,证明了R2n中紧星 形超曲面∑上brake轨道的几个多重存在性定理,结果包含了Szulkin的已有结论.

正定型超曲面上Hamilton系统Brake轨道的存在性

结合Rabinowitz和Szulkin关于Brake轨道的存在性与多重性的结论,利用部分对称泛函的临界点理论研究Hamilton系统在更广泛的能量面上Brake轨道的存在性问题.在适当条件下,证明了R2n中正定型超曲面Σ上存在Hamilton系统的Brake轨道.由于星型超曲面是正定型超曲面的特殊情形,该研究包含了Rabinowitz的相应结论.

Simulation and analysis of vehicle stability based on ADAMS/CAR differential brake

To improve the braking safety of automobiles, the author studied the effect of differential brake on the stabilities. To analyze the mechanical characteristics of differential brake, automotive subsystem models were built by applying ADAMS/CAR, and automotive mechanics simulation model was built by setting the main subsystems such as body, engine and brake. The simulation model studied the distribution mode of three kinds of differential brake, and beeline braking stability and turning braking stability were simulated. It shows that differential brake can amend turning shortage of automobile brake and improve its braking stability, but the effect of automobile mass on its braking stability is great. So the distribution mode of braking force and the effect of mass change should be considered while differential brake is applied.

Development of Iron Based Brake Friction MMC Used for Military Aircraft Application by A New P/M Route

A new P/M route based hot powder pre-form forging process has been evolved to develop high density brake materials for heavy duty applications. Number of iron based MMC’s so developed offer better characteristics for braking applications in comparison to the materials developed through conventional P/M route based on high pressure compaction and pressure sintering. The process so developed in the present investigations is much simpler and easy to adopt by existing P/M industries. Hot powder pre-form forging technique for making heavy duty brake pads offers better opportunity for pore free material with better bonding between various metallic and non-metallic constituents. After conducting an initial characterization such as hardness, density and Pin-on Disc tests, the samples were tested for high energy (32,933kgfm) on Sub-scale dynamometer under Rejected Take Off conditions. The results have also been compared with respect to brake pads employed in heavy duty Military aircraft tested under identical laboratory conditions. The present work indicates that the newly developed materials compare better than the one being currently employed in heavy duty aircraft. The reasons for better performance are improved processing technique and resulting higher levels of density and improved binding of the product.

Computer aided design and analysis of a tunable muzzle brake

This research work deals with the design of a tunable muzzle brake [10] for a rifle chambered in 5.56 x 45 NATO ammunition. It proposes to solve the problem of handling differences from shooter to shooter by incorporating the feature of tunability. Beside this, it also solves the problem of requirement of optimum recoil in short recoil weapons. This innovation gives this design an edge over its already existing counterparts in the market. The product is designed using the internal ballistics calculations and the investigations been performed using solidworks flow simulation tool and ANSYS static structural to check the parameters like velocity distribution, pressure growth, and muzzle brake force along the series of ports and comparison of the so found results with those devised by the authors of the documents mentioned in references. This assures the market adaptability of the product for satisfactory performance, when brought among its already existing counterpart, though with a slight edge over them due to tunability. The results so found shall be concluded satisfactory regarding the performance of muzzle brake.

Transient Temperature Field Analysis of Brake in Nonaxisymmetric Three-dimensional Model

The disk-pad brake used in automobile is divided i nt o two parts: the disk, geometrically axisymmetric, and the pad, of which the geo metry is three-dimensional. In the course of braking, all parameters of the pro cesses (velocity, load, temperature, physicomechanical and tribological characte ristics of materials of the couple, and conditions of contacts) vary with the ti me. Considerable evidence has show that the contact temperature is an integral f actor reflecting the specific power friction influence at the combined effect of load, speed, friction coefficient, thermo physical and durability properties of materials of a frictional couple. Furthermore, the physic mechanical state of t he interface of the disk and pads is determined not only by the contact temperat ure but also by the nonstationary temperature field. Using the two-dimensional model for thermal analysis implies that the contact conditions and frictiona l heat flux transfer are independent of θ. This may lead to false thermal elast ic distortions and unrealistic contact conditions. An analytical model is presen ted in this paper for the determination of contact temperature distribution on t he working surface of a brake. To consider the effects of the moving heat source (the pad) with relative sliding speed variation, a transient finite element tec hnique is used to characterize the temperature fields of the solid rotor with ap propriate thermal boundary conditions. And the transient heat conduction problem can be solved as a nominal 3-D transient heat transfer problem with an immovab le heat source. Numerical results shows that the operating characteristics of th e brake exert an essentially influence on the surface temperature distribution a nd the maximal contact temperature. The temperature field presents a noaxisymmet ric characteristic (a function of θ) and proves to be strongly localized and po ssesses a sharp gradient in both axial and radial directions.

Opening Angle Rules of the Aerodynamic Brake Panel

In order to get the relationship between aerodynamic brake effect and the opening angle,based on a high-speed train model in CFD software FLUENT,the aerodynamic force properties from brake panels with different opening angles were analyzed as well as the flow field's variation laws. Six cases were researched,taking opening angles 45°,60°,75°,80°,85° and 90° respectively.Three-dimensional Reynolds-average Navier-Stokes equation combined with k-ε turbulence model was utilized. The control equation was discretized and solved by finite volume method.SIMPLE method was also considered to couple the pressure and velocity fields and search the numeric solutions. Conclusions can be achieved from the results which are shown as follows. When the opening angle increases from 45° to 75°,the aerodynamic forces and the central area with larger pressure increase fast,and the flow field distribution changes greatly; when the opening angle increases from75° to 90°,the aerodynamic forces and the central area with larger pressure increase slowly, and the flow field distribution changes slightly; considering train boundary and opening performance of the wind resistance brake mechanism,the opening angle should be 75°.

RESEARCH ON DESIGN METHOD OF A MULTIPLE DISC WET BRAKE IN LUBRICATED ENVIRONMENT

The rmomechanical phenomens occurring between friction pairs greatly changethe distributions of lining pressure and friction surface temperature of a multiple disc wet brake.It has become one of the main causes of brake failure. In order to understand these thermomechanicalphenomena, several design and material factors that have great influence on thermomechanicalphenomena, such as heat transfer coefficient, friction factor; sliding velocity, initial liningpressure and so on, are analyzed. An isothermal design method is proposed for designing a multipledisc wet brake.

Comparative Study on the Complex Eigenvalue Prediction of Brake Squeal by Two Infinite Element Modeling Approaches

The complex eigenvalue analysis is currently a common approach to predict squealing vibration and noise. There are two methods for modeling friction contact in the complex eigenvalue analysis of friction systems. In one method, contact springs are used to simulate friction contact. In another method, no contact spring is used. However, it has been uncertain whether these two modeling methods can predict approximately identical results. In order to clarify the uncertainty, two finite element models of the same brake system for the brake squeal prediction are established and simulated by using ABAQUS and NASTRAN software tools, respectively. In the ABAQUS model, friction coupling is applied to determine normal contact force and no contact spring is assumed. Whilst in the NASTRAN model, the contact spring is assumed by the penalty method to simulate contact connection. Through the numerical simulations, it is recognized that even if the same mesh geometry is applied, generally, these two finite element approaches are not capable of predicting approximately identical unstable frequencies. The ABAQUS approach can predict instabilities of high frequency up to 20 kHz or more, while the NASTRAN approach can only predict some instabilities of high frequency, not all. Moreover, the simulation results also show that both the contact spring stiffness and mesh size have influences to some extent on the prediction results of squeal. The present comparative work illuminates that the modeling method without contact springs is more suitable to predict squealing vibration and noise, comparing to the modeling method with contact springs. It is proposed that one should prefer using the modeling method without contact springs to predict squealing vibration and noise. The proposed study provides the reference for predicting squealing vibration and noise.