Friction Brakes Research Articles

Thermal Analysis of a Simplified Railway Brake Model with Numerical Simulation

The braking system is the most important safety device in all vehicles. When braking, the kinetic energy of the vehicle is converted into thermal energy. The use of friction brakes can cause problems in the long term, as the brake can heat up, reducing its coefficient of friction. Heating and cooling have a harmful effect on all frictional elements, causing material fatigue. As a result of the negative effects, the hot brake cannot reduce the velocity of the vehicle at the correct rate. In this paper, the propagation of frictional heat is analysed in a test specimen made of cast iron material using different numerical simulations. The computational results are validated with the results obtained during measurement. With proper validation, the brake discs are able to be modelled at different designs and materials without having to manufacture a test specimen for each case. In the study, it is important to point physical quantities to carry out the simulation.

Detectability of residual stress anomalies in railway wheels with different geometries subjected to thermal overload based on back gauge change

Temperature increases of railway wheels due to frictional braking on the running surface (wheel tread) can lead to maintenance challenges such as tread wear and thermal cracking. While heating within the anticipated design range should not adversely affect the structural safety of the wheels, excessive temperature rises resulting from brake system failures can induce tensile residual stresses in the rim, potentially leading to wheel fracture. Detecting wheels with abnormal residual stresses is therefore crucial for railway safety, and monitoring residual displacements in the rim due to changes in circumferential residual stresses is an implementable approach. However, the shape of the wheel web varies, and the displacement response to thermal input differs depending on the wheel geometries. This study aims to explore general deformation behaviours related to wheel shape and elucidate the relationship between shape and heat resistance. The elastic-plastic finite element analysis employing simplified intense thermal input revealed that residual deformation after excessive thermal loading consistently results in back gauge expansion, although the deformation and stress responses differ based on the web geometry. Differences in heat resistance are indicated by the variation in the temperature at which compressive yielding due to thermal stress occurs, depending on the web shape. The residual stress detectability of each wheel is determined based on the principle that greater residual displacement at lower stress indicates higher anomaly detectability.

Theoretical Analysis of Viscoelastic Friction System Characteristics of Robotic Arm Brake Based on Fractional Differential Theory

In engineering practice, the nonlinear vibration effect can easily lead to chaos in the system, which will not only reduce the performance of the system but also lead to premature fatigue of components, control failure, and increased safety risks. In view of the core position of the robotic arm in modern industry, this study relies on the robotic arm brake system to explore the theoretical basis of integrated viscoelastic materials as a vibration isolation layer. By analyzing the dynamic characteristics of the friction braking system with fractional differential terms, it aims to provide a new perspective for understanding and controlling the chaotic phenomena of a class of nonlinear friction systems. Firstly, we construct a model of a friction system and analyze its dynamic characteristics in detail. The self-excited vibration of the system under disturbance is studied. The relationship between amplitude and frequency is calculated by a nonlinear approximate analytical algorithm, and the accuracy of this relationship is verified by a numerical algorithm. Then, we compare the differences between non-fractional systems and fractional systems. It is found that with the increase in the fractional order term, the vibration amplitude of the system decreases significantly, which helps to reduce the nonlinear characteristics generated by the friction system and narrow the range of unstable solutions. Secondly, we also study the influence of parameter coefficients on the amplitude–frequency characteristics and analyze the local static bifurcation characteristics through singularity theory. Finally, we study the dynamic bifurcation behavior under different parameter perturbations and find that the change in system parameters will lead to the alternation of periodic motion and chaotic motion.

Performance assessment of agricultural waste based eco‐friendly brake friction composites

AbstractThere has been growing interest in using sustainable and eco‐friendly products to produce engineering materials. For this purpose, composite material applications obtained from agricultural wastes are gaining popularity. This study examines the synergistic effect of rice husk and rice stalk wastes on the fade and recovery performance of brake friction composites. Brake friction materials were developed using rice husk and rice stalk separately and in two different weight percentages as a 5–10 ratio in the formulation. For comparison purposes, a reference brake pad using copper as a substitute and a commercially available brake pad were used. Various physical, mechanical and thermal properties were analyzed. The tribological behavior of friction composites was evaluated on the Krauss test device in line with the ECE R90 procedure. The worn surface properties were analyzed using scanning electron microscopy. Tribo test results of friction composites were taken as criteria for performance optimization. While the importance weight of the criteria was determined by AHP, the VIKOR method was used in the sorting of alternatives. The experimental results have revealed that rice husk‐added friction composites had a good coefficient of friction value with better fade and recovery performance compared to rice stalk‐added ones. Increasing the amount of rice husk and rice stalk in the formulation tended to decrease the fade performance; however, it has increased the wear rate and recovery properties. Optimization results have shown that the brake friction composite containing 5 wt % rice husk ranks first in meeting the desired tribological criteria.Highlights Cu‐free rice husk and rice stalk‐added friction composites were developed. Fibrous structure in the matrix developed the contact plateaus. Rice husk‐based tribo‐layer protected the composite from further wear damage. The addition of agro‐waste to friction composites exhibited good potential.

Clamping Force Control of Electromechanical Brake Actuator Considering Contact Point between Friction Lining and Brake Disc

Currently, most electromechanical brake (EMB) schemes are only suitable for passenger cars, and their maximum clamping force is insufficient to satisfy the braking demands of commercial vehicles. Additionally, previous studies on clamping force control are largely based on an EMB equipped with sensors. Due to constraints in installation space and cost, sensorless EMBs are gradually gaining attention. Furthermore, accurately identifying the contact point between the friction lining and the brake disc is the promise of clamping force control for sensorless EMBs. Hence, a sensorless EMB scheme suitable for commercial vehicles is proposed in this study. Secondly, a dynamics model of the EMB actuator is established. After a comprehensive analysis of the proposed EMB actuator, a clamping force control strategy considering the contact points between the friction lining and the brake disc is proposed. Finally, simulation analyses of the strategy are carried out. The results show that the axial length of the proposed EMB actuator is shortened by 17.6% compared with a mainstream pneumatic disc brake. Furthermore, the proposed method can accurately identify the contact points between the friction lining and the brake disc, and the proposed control strategy enables the EMB actuator to achieve the fast response, accurate tracking, and stable maintenance of the target clamping force.

Preparation and Properties of Brake Friction Materials Reinforced with Coconut Fiber and Dypsis Lutescens Fiber.

Brake friction material reinforced with coconut fiber and dypsis lutescens fiber was designed and prepared in this study. Specimens incorporating 0-8 wt.% of coconut fibers or dypsis lutescens fibers were fabricated. The effect of the content of these reinforcing fibers on the overall properties of brake friction materials was systematically investigated. The results indicate that the inclusion of reinforcing fibers in the formulation of brake friction materials can improve the physical properties and friction and wear properties of brake friction materials. The specimen incorporating 6 wt.% plant fiber obtained the optimal comprehensive performance with excellent fade resistance and recovery properties, and better wear resistance. In order to further investigate their performance, nine hybrid fiber brake friction materials were designed using the golden section method and orthogonal test method. The study indicated that the F-6 hybrid fiber-reinforced brake friction materials have better physical properties, thermal degradation resistance, recovery properties, and abrasion resistance than the single-fiber-reinforced brake friction materials. This study provides new concepts for the preparation of fiber-reinforced brake friction materials as well as formulation optimization.

Mechanical and microstructure characterisation of 2.5D C/C-SiC composites applied for the brake disc of high-speed train

Carbon fibre reinforced silicon carbide (C/C-SiC) composite materials have attracted increasing attention in brake system of high-speed trains, due to their low density, high specific strength, thermal stability, and frictional wear performance. This study aims to explore the mechanical properties of the 2.5D C/C-SiC composites, in order to characterise its potential application to the friction braking system of high-speed trains. To comprehensively evaluate the mechanical performance of the 2.5D C/C-SiC composites, the chemical vapor infiltration (CVI) method was adopted to prepare novel samples with high densification and low content of residual Si. The mechanical properties and failure mechanisms of the composites were investigated under various loading conditions, including tension, compression, bending, and shear tests. The experimental results indicated that the 2.5D C/C-SiC composites exhibited superior mechanical properties, with average in-plane tensile strength, compressive strength, bending strength, and interlaminar shear strength reaching 127.67 MPa, 326.92 MPa, 355.74 MPa, and 9.77 MPa, respectively, which are 2–8 times higher than the mechanical properties of C/C-SiC composites in existing publications. Under different loading conditions, the composites demonstrated characteristics of ductile fracture, pseudo-plastic compression fracture, pseudo-plastic bending fracture, and brittle shear fracture. Both high fibre content and the formation of SiC structure were advantageous for enhancing the load-bearing performance of C/C-SiC composites. The outstanding mechanical properties of the 2.5D C/C-SiC composite render the brake disc highly resistant to deformation and cracking under high stress, thereby enhancing its durability and establishing it as the ideal material for the next generation of high-speed train brake discs.

Enhancing Estimating the Charge Level in Electric Vehicles: Leveraging Force Fluctuation and Regenerative Braking Data

Accurate determination of the state of charge is vital to optimize the performance and lifespan of electric vehicle batteries. Traditional methods which rely on battery models and direct measurements can be error-prone due to fluctuating operating conditions and battery degradation over time. Regenerative braking systems are crucial in electric and hybrid vehicles for improving energy efficiency by transforming kinetic energy into electrical energy during braking. However, force fluctuation is a challenge that can affect the performance and comfort of regenerative braking. It is known to us that electric motors and generators used in regenerative braking have non- linear torque characteristics, especially at low speeds, leading to inconsistent braking force. Variations in road conditions, such as wet or uneven surfaces, can affect the grip of the tires, leading to fluctuations in deceleration. Interactions of regenerative braking system with conventional friction brakes can cause force fluctuations, especially during the transition between the two systems. This study introduces an improved state of charge estimation technique based on force fluctuation and a regenerative braking system. This research shows that this approach significantly enhances state of charge accuracy compared to traditional methods, especially in urban driving conditions with frequent braking. The findings underscore the potential of using regenerative braking as well as force fluctuation condition data as a valuable input for state of charge estimation, ultimately leading to better battery management and an extended electric vehicle range.

Inhibitory Control of Downhill Turning Using Friction Brakes for Manual Wheelchair

Inhibitory Control of Downhill Turning Using Friction Brakes for Manual Wheelchair

Brake Wear and Airborne Particle Mass Emissions from Passenger Car Brakes in Dynamometer Experiments Based on the Worldwide Harmonized Light-Duty Vehicle Test Procedure Brake Cycle

Brake wear particles, as the major component of non-exhaust particulate matter, are known to have different emissions, depending on the type of brake assembly and the specifications of the vehicle. In this study, brake wear and wear particle mass emissions were measured under realistic vehicle driving and full friction braking conditions using current commercial genuine brake assemblies. Although there were no significant differences in either PM10 or PM2.5 emissions between the different cooling air flow rates, brake wear decreased and ultrafine particle (PM0.12) emissions increased with the increase in the cooling air flow rate. Particle mass measurements were collected on filter media, allowing chemical composition analysis to identify the source of brake wear particle mass emissions. The iron concentration in the brake wear particles indicated that the main contribution was derived from disc wear. Using a systematic approach that measured brake wear and wear particle emissions, this study was able to characterize correlations with elemental compositions in brake friction materials, adding to our understanding of the mechanical phenomena of brake wear and wear particle emissions.

The role of the damping component deformation in improving the tribological behavior at the high-speed train braking interface

Aiming to the issue of the unclear mechanism and lack of design basis for the influence of the deformation of the damping component installed in the brake pads of high-speed train, various perforated configurations were implemented on the damping component to obtain different typical deformation. The damping component was then installed on the back of the friction block and the tests on friction braking were performed using a test rig designed to assess high-speed train braking performance. A finite element model (FEM) was established for wear simulation to obtain block worn surfaces that closely matched the test results, succeeded by conducting both complex eigenvalue analysis (CEA) and implicit dynamic analysis (IDA). The findings indicate that the perforated configurations effectively provided damping components with different deformation capabilities, and increasing the deformation weakened its damping effect on vibration. The damping component deformation not only significantly affected the non-uniform wear on the block surface but also altered the wear patterns. Inappropriate deformation exacerbated the degree of non-uniform wear, leading to complex abrasive wear and adhesive wear, and added to the interface damage. Therefore, the damping component deformation significantly altered the friction-induced vibration and noise (FIVN) characteristics. Enhancing the deformation disrupted the continuity of FIVN but intensified its strength. The major reason is that the damping component deformation determined the time length of its compression and rebound, and inappropriate deformation significantly amplifying the oscillation intensity of contact area and friction force. This posed a challenge in establishing stable contact at the braking interface, ultimately leading to the generation of intense FIVN. Installation of damping components in brake pad to improve interface contact characteristics and suppress FIVN should carefully consider the structural of the braking system, and design damping components with appropriate deformation. Otherwise, it may lead to opposite effects.

Characterization of Glass Waste Resulting from Milling Process for Reuse as Filler in Brake Friction Composites

Characterization of Glass Waste Resulting from Milling Process for Reuse as Filler in Brake Friction Composites

Analysis of friction-induced vibration and wear characteristics during high-speed train friction braking process

This study explored the evolution of friction-induced vibration (FIV) and wear in high-speed train friction braking through experiments, theoretical analysis, and numerical simulation. Experimental tests revealed that vibration behavior transitions from high-frequency modes at high speeds to low-frequency stick-slip at lower speeds. Theoretical analysis indicated that brake disc speed, coefficient of friction (COF), and contact stiffness affect system stability. Specifically, the system experiences high-frequency vibrations at high speeds due to mode coupling, and the friction block surface primarily undergoes abrasive wear mechanisms. At lower speeds, the system demonstrates low-frequency stick-slip vibrations induced by the combined effects of mode coupling and negative friction velocity slope (NFVS) characteristics, and the friction block surface mainly experiences adhesive wear mechanisms.

Modification of friction block connection for improving the tribological behavior of high-speed train braking interface

This work aims to improve interface tribological behavior by modifying the friction block connection. The effectiveness of this approach and its underlying mechanisms are evaluated through friction braking test and finite element analysis (FEA). A finite element model (FEM) was established based on the main structure and material parameters of the high-speed train braking performance simulation test setup. The Achard wear formula was used to adequately run-in the friction block. Using a restart analysis to inherit the model post run-in, complex eigenvalue analysis (CEA) and implicit dynamic analysis (IDA) were conducted. Results indicate that the disc spring deformation significantly affects tribological behavior and friction-induced vibration and noise (FIVN) via regulating the contact state at the braking interface. Inappropriate deformation of the disc spring can lead to severe eccentric wear of the friction block, exacerbating the tribological behavior at the braking interface and inducing the brake system to generate high-intensity FIVN. Therefore, rational design of disc spring connection is an effective strategy for improving interface tribological behavior, but the disc spring connection design must provide it appropriate deformation capability. This is essential to ensure that the braking interface exhibits favorable contact state, thereby improving tribological behavior.

Design of ABS sliding mode control system for in-wheel motor vehicle based on road identification

Aiming at the problem that the current Anti-lock Braking System (ABS) control algorithm can not make full use of the ground friction to complete the braking when emergency braking on complex roads, an ABS sliding mode control method based on road surface identification is proposed. Combined with the in-wheel motor of in-wheel motor electric vehicle, a coordinated control method of motor regenerative braking and mechanical friction braking is designed. Based on the neural network control method, the road friction coefficient is estimated to realize the identification of typical roads and dynamically obtain the optimal slip ratio of different roads. The ABS sliding mode controler is designed with the optimal slip ratio and the actual slip ratio as input, and the saturation function is used to replace the symbol function in the traditional sliding mode control to weaken the chattering problem, and then the ABS controller is designed. The research results show that compared with the traditional ABS sliding mode controller, the designed ABS neural network sliding mode controller has the following advantages: 1. Through the identification of tire-road friction coefficient by neural network, the real-time performance and road adaptability of ABS controller are improved; 2. When the braking simulation is carried out at a given speed, the braking time is reduced by about 1.03 % and the braking distance is shortened by about 1.01%; 3. The identification of tire-road friction coefficient is realized, which weakens the chattering problem of traditional sliding mode control and improves the stability and robustness of ABS controller.

Coordinated control strategy of electro-mechanical composite braking for four-wheel drive electric vehicles

Regenerative braking energy recovery technology is critical for electric vehicles, which can significantly improve vehicle mileage. In addition, the regenerative braking system is often used with the friction braking system to provide vehicle braking force. This paper presents an electro-mechanical compound brake control strategy for four-wheel drive electric vehicles equipped with an electro-mechanical braking system. Firstly, the configuration of a four-wheel drive electric vehicle with an electro-mechanical braking system is introduced. The mathematical models of the driving motor, battery, and electro-mechanical braking are established. Secondly, a new control method is introduced by optimizing torque allocation based on maximum energy recovery with considering battery limits and a cooperative control method of the electro-mechanical composite braking system. It can be ensured that the braking energy recovery capability and braking comfort. Finally, simulation results indicate that the introduced control strategy can increase the braking recovered energy by 3% and 4%, respectively, under NEDC and WLTC conditions, compared to the ideal braking force distribution strategy. The introduced control method can effectively decrease the braking impact and ensure braking comfort in the coordination control section.

Comparison of performance and tribological properties of electromechanical brake with magnetorheological fluid and magnetic powder

Brakes, which are the safety component of any automobile used to control the motion of the vehicle as per the driver's choice. In conventional brakes, friction lining materials are used, which affect the health of human beings and pollute the environment. Hence, there is a need to look for new types of brake systems. In the present work, a new type of electromechanical (EM) drum brake is designed that does not use friction lining materials for brake application. It can use magnetorheological (MR) fluid as well as magnetic powder (MP) for brake application. The presented brake has been designed to operate in hybrid mode that is, shear plus compression mode. When MR fluid is used, these brakes face the problem of the leakage of MR fluid which motivates to use of MP. In addition to the design of the new brake, the performance of the new brake has been tested with MR fluid and MP separately on a full-scale brake inertia dynamometer. The performance test results have been compared for both MR fluid and MP and compared with conventional friction brakes. 14.56% and 11.38% more braking torque have been observed for MP compared to that of MR fluid in shear and hybrid mode respectively. In addition to the performance study, the effect of MR fluid and MP on brake shoe surface properties has been studied.

Long Downhill Braking and Energy Recovery of Pure Electric Commercial Vehicles

The thermal decay of the brake has a great impact on the long downhill braking stability of pure electric commercial vehicles. Based on the road slope and using the fuzzy control method, the motor regenerative braking force and friction braking force distribution strategies were designed to reduce the friction braking force, improve the braking stability and recover the braking energy. By establishing road driving conditions with different slopes, numerical analysis methods are used to verify the proposed control strategy. The results show that the vehicle maintains a constant speed downhill at 30 km/h under the condition of 6% constant slope driving, and the braking energy recovery rate reaches 50.93% under 60% initial battery SOC, 50.89% under 70% initial battery SOC, and 50.81% under 80% initial battery SOC. The speed of the vehicle fluctuates slightly under the driving condition of an 18 km long variable slope distance, but the power torque of the electric mechanism can still be maintained at a constant speed of 30 km/h by adjusting the electric mechanism, and the braking energy recovery rate reaches 49.96%. During the downhill driving at a constant speed, the friction braking force does not participate in braking, and the recuperation rate of braking is determined by the slope and the magnitude of braking deceleration.

Effect of uneven wear on the stability of friction braking system in high-speed train

The frictional interface in high-speed train braking systems is subjected to prolonged exposure to high loads and frequent friction, leading to noticeable macroscopic surface alterations. Uneven wear, as the primary manifestation change, is characterized by a discernible inclination angle between the friction block and the brake disc. In this study, a three-dimensional numerical model incorporating six degrees of freedom is developed to investigate the influence of wear-induced inclination angles on the stability of the disc-block coupling system. Modal analysis and practical experiments are conducted to validate the accuracy of the model. The analysis reveals that both tangential and axial inclination angles significantly affect the system's stability, with the system demonstrating heightened sensitivity to variations in the axial inclination angle. These angles induce variations in the contact area, subsequently leading to changes in the friction coefficient and contact stiffness. Decreasing the stiffness ratio between the normal and tangential directions proves advantageous in enhancing the system's stability and reducing the tendency for unstable vibrations within the friction system. Similarly, increasing the friction coefficient yields similar effects. Besides, time-domain analysis of acceleration signals obtained from both the numerical model and practical experiments indicates that an escalating inclination angle results in unstable vibration behavior, potentially leading to system instability. Therefore, understanding and controlling wear-induced inclination angles are essential for maintaining the stability and performance of high-speed train braking systems.

Modelling of Energy Recovery in Electric Vehicles for Various Braking Scenarios on Changing Road Surfaces

Due to great braking energy losses caused by traffic jams, changing velocity, and frequent start-stop modes, recovery of braking energy has become a top priority. In this paper, the universal braking system is described that operates at various driving scenarios including smooth braking and emergency antilock braking on different road surfaces and integrates both the friction and the electric braking strengths. The vehicle model reflects multiple factors, such as air resistance, road slope, and variable friction. The refined tire model recognizes changing road surfaces at different velocities. In the motor and battery model, the state of charge and electric current/voltage restrictions of the hybrid energy storage are taken into account. Braking torque generated by the Sugeno’s fuzzy logic controller established in the Simulink environment is allocated between friction and electric brakes. Often cited torque oscillations at low vehicle velocities have found their description, being reduced and evenly distributed throughout the braking process with the help of torque stabilisation loop. The outcomes of this study can be considered in the design of braking systems for electric vehicles with superior energy recovery capacity.