Braking Temperature Research Articles

Impact of initial braking temperature on thermal-induced brake fade during long-downhill operations

The advancement of high-speed railways and the widespread application of complex terrains have highlighted the issue of performance degradation in braking friction pairs during long-downhill braking, especially under high-temperature conditions. This study addressed this problem using a self-developed high-speed train braking simulation test rig to investigate the effects of varying initial braking temperatures (IBTs) on the performance degradation of braking friction pairs. A combination of thermal imaging, energy dispersive spectroscopy (EDS), high-temperature hardness testing, and X-ray diffraction (XRD) was employed to assess performance changes under different temperature conditions. By controlling the IBT of the brake disc, a detailed analysis of the coefficient of friction (COF), frictional heat distribution, wear morphology, hardness variation, and residual stress were conducted to uncover the brake fade mechanisms. The findings reveal that as IBT increases, COF decreases with greater fluctuations, resulting in significantly extended braking times and distances. At elevated IBTs, the brake disc and friction block materials experience reduced hardness, increased tangential residual stress, decreased radial residual stress, and accelerated wear, leading to unstable COFs and extended braking distances. This work provides valuable insights into the mechanisms of thermal-induced brake fade during long-downhill braking, offering crucial technical guidance for enhancing the safety and reliability of high-speed train braking systems under extreme conditions.

Influence of thermal expansion and wear on the temperatures and stresses in railway disc brakes

Thermo-mechanical coupled systems are typically complex, however, the demand for analyses of this kind of multi-physics system is increasing, for example, accurately predicting the temperature and thermal stress of the railway disc brakes. However, many models ignore the phenomenon of thermal expansion and wear on brake pads. Therefore, their influence on the result is unclear. This research aims to investigate the effect of these two phenomena on the temperatures and stresses. These influences represent different heat flux input methods. Based on the finite element method (FEM), a three-dimensional (3D) transient thermo-mechanical model is built up. Three cases with or without thermal expansion and wear are conducted. The model is validated against measurement data. Simulation results show that thermal expansion and wear on the brake pads cause a 10% difference in the average temperatures of the brake discs, while a 257% difference in the maximum temperatures. As for the equivalent stresses (Von Mises stress), the difference can reach 3500%. Overall, this research builds a thermo-mechanical model and quantifies the effects of thermal expansion and wear on the temperatures and stresses of railway brake discs. The model can be transferred to other thermo-mechanical coupled multi-physics systems.

Alloy selection for wear-resistant lightweight aluminium brake disc

Brake discs for the rear axle of a high-performance sports car have been manufactured in three different lightweight materials; AA6082, AA7075 and AA2024 aluminium alloys. These were subsequently coated with a Keronite plasma electrolytic oxidation (PEO) ceramic layer. Full-scale dynamometer tests have been conducted against a standard low-met brake pad using a modified AK master test at increasing levels of braking temperature until a physical limit is reached. Microstructural characterisation of coating and brake pad wear and tribo-layer have been studied using SEM and EDX. In addition, post-dynamometer-test friction discs have been exposed to salt fog testing. Dynamometer tests give confidence that PEO-coated aluminium brake discs are a viable technical solution for vehicle lightweighting. In particular, compelling performance with respect to good coefficient-of-friction (CoF), extremely high coating adhesion, minimal disc and pad wear, low disc run-out, good heat dissipation, and good corrosion resistance has been demonstrated for Mat A (AA6082) alloy discs. Despite higher room temperature strength, the resulting performances of Mat B (AA7075) and Mat C (AA2024) are poor at higher braking temperatures, resulting in excessive coating spallation and subsequent grain boundary attack followed by severe intergranular corrosion.

Evaluation of the Mechanical and Tribological Behavior of Polyether Ether Ketone Fiber-Reinforced Resin-Based Friction Materials Fabricated by Wet Granulation.

Resin-based friction materials (RBFMs) strengthened by polyether ether ketone (PEEK) fiber were designed and prepared in this study. Specimens incorporating PEEK fiber of 2-8 wt.% were fabricated based on wet granulation, and then the effects of the PEEK fiber content on the mechanical and tribological properties of RBFMs were systematically investigated. The results showed that PEEK fiber can sense the braking temperature and then effectively regulate the comprehensive properties of RBFMs. The specimen incorporating 6 wt.% PEEK fiber obtained the optimal comprehensive performance with a stable friction coefficient (COF), excellent fade resistance and recovery properties, and better wear resistance. The worn surface was inspected using a scanning electron microscope. After the friction-wear test, the specimen with 6 wt.% PEEK fiber presented a number of primary and secondary plateaus and a reduced number of pits with wear debris on the worn surface. The study indicated that PEEK fiber could not only enhance the mechanical and tribological properties of RBFMs at low temperatures because of their high strength and self-lubrication but also adhere to wear debris to reduce abrasive wear at high temperatures; furthermore, the adhered wear debris could form a secondary plateau under normal pressure, which could alleviate abrasion.

Study on reliability of emergency braking performance of high-speed and heavy-load monorail crane

The reliability of monorail crane braking system has an important influence on braking safety, high-speed and heavy-load operation, which poses great challenges to braking safety, and it is necessary to evaluate its braking reliability accurately and efficiently. Firstly, the dynamic performance and thermal-mechanical coupling characteristics of high-speed and heavy-load monorail crane under different braking parameters were analyzed. Secondly, the random response model of braking distance and braking temperature was established by combining the design of experiment method (DoE) and Dendrite Net (DD). Finally, the high-order moment saddlepoint approximation (SPA) method was used to evaluate the emergency braking reliability of the monorail crane. The results can provide a reference for the selection of key parameters and the evaluation of braking safety of the monorail crane braking system under high-speed and heavy-load conditions.

Research on wear rate of train brake pads driven by small sample data

Increased wear leads to the failure of brake pads. Both the International Union of Railways (UIC) and the China Railway Production Certification (CRCC) take wear rate as an extremely important parameter that characterizes the degree of wear, and its value can provide reference for the braking performance of the brake pads. Since the braking performance test of brake pads is time-consuming and costly, the sample data of wear rate is small. In this study, we explore the coupling relationship between the wear rate of train brake pads and its features such as initial braking speed (IBS), braking pressure (FB), braking temperature and average coefficient of friction (ACOF), and propose a Butterfly Optimization Algorithm-Back Propagation (BOA-BP) method suitable for small sample data for the wear rate prediction of brake pads. The grey relational analysis (GRA) and Pearson correlation analysis (PCA) are used to arrive at preferred features for the prediction of wear rate of brake pads, such as IBS, FB, braking distance and ACOF. The dynamic GM(1, N) and the least square method are used for sample expansion. Furthermore, the wear rate is designated as the output feature parameter and the preferred features are designated as the input feature parameters, a BOA-BP model is established for predicting the wear rate of brake pads. The results show that the wear rate obtained by dynamic GM(1, N) is consistent with the actual braking test, the maximum temperature and the braking pressure are important factors affecting wear rate. Compared to the comparison methods such as PSO-BP, GA-BP, and BP, the BOA-BP exhibits better advantages in prediction with small samples, and the average prediction accuracy with 33 sets of data and 99 sets of data are 95.70 % and 97.21 % respectively.

BRAKE SURFACE TEXTURE EXPLORATION AND TEMPERATURE CONTROL DURING BRAKING IN THE NEW KNEE IMPACT TEST

During the braking process, frictional heat generation between brake strip and brake block can lead to high temperatures, significantly affecting the braking performance. This paper proposes a novel knee impact test method and innovatively investigates the effect of brake friction surface texture shape on braking performance. A comparative evaluation of the braking performance of different surface textures is conducted using the new knee impact test, with a focus on studying the temperature rise during braking to optimize the brake system. Research findings indicate that the best braking performance was achieved when friction surface texture of the brake block was rhombus-shaped with a diagonal ratio of 5:5. By implementing this improved brake design, the maximum temperature during braking was reduced from 184.44[Formula: see text]C to 75.963[Formula: see text]C, resulting in a significant reduction in thermal stress from 155.22 MPa to 64.40 MPa. Moreover, the acceleration and brake distance are extracted and compared with the target values of Euro NCAP. The improved brake acceleration exhibits stability and a deviation from target value within 10%. Additionally, the deviation between our brake distance and target distance is −3.63%. These results provide a valuable reference for improving the braking performance of braking systems in the new knee impact test.

Braking performance and temperature characteristics analysis of parallel multi-channel magnetorheological brake

In order to improve the braking performance of magnetorheological (MR) brake, a new MR brake with parallel multi-channel structure was developed in this paper. The three layers of axial damping gaps in the MR brake were utilized by using of the magnetic conductivity of the material, and the double excitation coils was also adopted to effectively improve the braking performance. The braking torque and temperature characteristics were analyzed theoretically, and the electromagnetic field and temperature field were simulated and verified. Braking performance and temperature characteristics of the parallel multi-channel MR brake were tested, and the torque, braking time and temperature characteristics of the MR brake were obtained. The test results show that under the condition of constant rotational speed of 700 r/min and applied current of 2 A, the maximum torque can reach 26.25 N⋅m, and the temperature rises from 18.3 °C to 58.01 °C within 20 s. Meanwhile, the braking time is about 1.63 s.

Study on the influence of running parameters on the temperature field of disc brake on long downhill road

The braking system of the vehicle is liable to fail due to the high temperature of frequent braking in the downhill road. This paper analyzes the influence of the main operating parameters of the vehicle on the maximum temperature of the brake disc surface. Firstly, the mechanical characteristics of the vehicle on the long downhill road are analysed, and the Finite Element Model of the brake disc/friction plate is established; Secondly, the effects of gradient, vehicle weight, brake speed threshold and brake pressure on the braking cycle and disc brake temperature field on long downhill roads are studied. The results show that when the gradient increases from 3° to 9°, the maximum temperature of the brake disc increases by 41.6%, while when the vehicle weight increases from 4 to 7 tons, the brake disc temperature only increases by 16.7%. For the braking speed threshold and braking force that the driver can control, selecting a smaller braking force and a lower braking speed threshold can better inhibit the temperature rise of the brake disc. Finally, the effectiveness of the simulation method is verified by the real vehicle test. It is found that the average measured temperature is 9.2%–11.8% lower than the simulated average temperature. It is considered that the modified temperature value can be obtained by reducing the maximum temperature of the simulation model by 5%–6%.

Study on reduction of squeal noise of disc brake system considering braking temperature of urban railway vehicle

Study on reduction of squeal noise of disc brake system considering braking temperature of urban railway vehicle

Study on the mechanism of expanded graphite to improve the fading resistance of the non-asbestos organic composite braking materials

To improve the anti-fading performance and braking reliability of non-asbestos organic composite braking materials (NAOCBM) and to decrease vehicle driving risks due to braking failure, we studied the addition of expanded graphite (EG) to NAOCBM. The properties were optimized when the EG dose was 4 wt%. The reason for improvement was that the local flexible internal stress due to graphite expansion at high braking temperature partially offset the crack expansion, and thereby significantly decreased the damages of delamination wear to braking materials and braking performances. These results uncover the mechanism of EG addition to the performance optimization of braking materials, and provide an effective method to improve the reliability of braking materials and to reduce the probability of traffic accidents.

Simulation of Temperature Distribution in a Brake Pad Ceramic Composite Material

The temperature distribution is an important aspect of any brake pad composite material. The braking temperature affects the performance and efficiency of any brake pad composite material. It is difficult to measure the interface temperature between the brake pad and disc by thermocouples or infrared thermal sensors during braking. This work investigates the temperature distribution of a ceramic composite brake pad material by the transient thermal analysis method. The transient thermal approach method helps to visualize the interface temperature through simulation. Also, it provides pin temperature at a distance of 4 mm and 6 mm away from the disc surface to observe the temperature distribution of the brake pad. The experimental values of the temperature of the pin at 4 mm and 6 mm away from the disc are collected from the literature and compared with the predicted temperature through simulation. It is found that there is a close agreement between the predicted and experimental temperature values.

Experimental and simulation study on braking noise characteristics and noise reduction strategies of the friction pair between the SiCp/A356 brake disc and the synthetic pad

During the braking process, abnormal noise often occurs between the friction pair of SiCp/Al composite disc and synthetic brake pad. Through 1:1 bench noise test and simulation method based on complex eigenvalue analysis, the induction mechanism, influencing factors, variation rule and noise reduction strategy of braking noise were studied. The results of MM-1000 friction reduced-scale test and simulation show that the sound pressure levels of two groups of friction pairs using SiCp/A356 composite material are lower than those of FE-928W friction pair under the same working conditions. The friction surfaces of different friction pairs show different degrees of surface scratches, material transfer and peeling, which will cause the friction pairs to have different tribological properties and contact relationships, resulting in differences in braking noise. 1:1 bench test and simulation results show that the main type of brake noise of service brake parts is brake squeal, which is induced by the braking temperature rise. Its main frequency is concentrated around 2.2 kHz, and the maximum sound pressure level can reach 110 dB(A). Braking squeal is more likely to occur when the energy input of a single brake is too large, resulting in high temperature rise of the brake parts, or when the brake temperature is kept at a high level in continuous braking for several times. The orthogonal test and the control variable method were used to study the influence law of 10 variables on the tendency of braking noise. It is found that the brake pad is the main component of the braking noise, and the friction coefficient of the friction pair and the Young's modulus have a significant effect on the tendency of braking noise. Considering the test results and simulation laws, the brake noise control strategies were proposed, such as increasing the chamfer depth of the pad friction surface, reducing the friction coefficient of the friction pair, increasing the young's modulus of the pad and controlling the brake temperature rise. In addition, compared with the original model, the instability tendency coefficient (TOI) of the new disc model established through variable selection is reduced by 81.21 %, and the brake noise tendency is obviously reduced, which verifies the effectiveness of the brake noise control strategy at the simulation level.

Intelligent prediction of wear life of automobile brake pad based on braking conditions

PurposeTo avoid braking accidents caused by excessive wear of brake pad, this study aims to achieve online prediction of brake pad wear life (BPWL).Design/methodology/approachA simulated braking test bench for automobile disc brake was used. The correlation and mechanism between the three braking condition parameters of initial braking speed, braking pressure and initial braking temperature and the tribological performance were analyzed. The different artificial neural network (ANN) models of wear loss were discussed. Genetic algorithm was used to optimize the ANN model. The structure scheme of the online prediction system of BPWL was discussed and completed.FindingsThe results showed that the braking conditions were positively correlated with the wear loss, but negatively correlated with the friction coefficient. The prediction accuracy of back propagation (BP) ANN model was higher. The model was optimized by genetic algorithm, and the average deviation of prediction results was 4.67%. By constructing the online monitoring system of automobile braking conditions, the online prediction of BPWL based on the ANN model could be realized.Originality/valueThe research results not only have important theoretical significance for the study of BPWL but also have practical value for guiding the maintenance and replacement of automobile brake pads and avoiding the occurrence of braking accidents.

Design and test validation of a novel permanent magnet eddy current brake

Aiming at slippage and belt breakage of large mechanical conveyor belts, a new type of water-cooled permanent magnet brake (WPMB) is proposed. In order to determine the braking performance of WPMB, a multi-physics coupling model and analysis method of magneto-thermal-structure are built. The braking torque and temperature characteristics of WPMB under different working conditions are obtained. Based on the magnetic vector potential equation, an electromagnetic eddy current model is established, and the variation trend of braking torque with speed is predicted. The temperature field model is built based on the equivalent thermal network method. Using multi-field coupling analysis method and 3-D FEM, the influence factors of WPMB braking torque are analyzed. Two test prototypes with rated speed of 78 rpm, braking torque of 3000 N⋅m are designed and developed. Braking torque characteristic tests and magnetic shielding characteristic tests at different speeds and continuous braking characteristic test are carried out. Experiments show that the proposed method provides very practical results to ensure the continuous and stable operation of WPMB.

Estimating Brake Pad Life in Regenerative Braking Intensive Vehicle Applications

<div class="section abstract"><div class="htmlview paragraph">Regenerative braking without question greatly impacts brake pad service life in the field, in most cases extending it significantly. Estimating its impact precisely has not been an overriding concern - yet - due in part to the extensive sharing of brake components between regen-intensive battery-electric and hybrid vehicles, and their more friction-brake intensive internal combustion engine powered sibling. However, a multitude of factors are elevating the need for a more accurate estimation, including the emerging of dedicated electric vehicle architectures with opportunities for optimizing the friction brake design, a sharp focus on brake particulate emissions and the role of regenerative braking, a need to make design decisions for features such as corrosion protection for brake pad and pad slide components, and the emergence of driver-facing features such as Brake Pad Life Monitoring. Tackling this question raises questions such as “is the proven braking energy and temperature based wear model still sufficiently predictive of wear or do other mechanisms become dominant?”, and “how does customer behavior for charging and discharging of the battery affect brake pad life?” In the present study, validated models for brake pad life in the field are adapted for regenerative braking equipped vehicles, including simple models for the battery charge acceptance power, battery state of charge, electric drive unit characteristics, and customer battery charging habits. After correlating with field data, the models are used in case studies to illustrate some of the important considerations for friction brake wear on regenerative brake equipped vehicles.</div></div>

Theoretical Foundations of Construction of the Electronic System for Spatial Measuring of Air Signals Aircraft Plane’s with One Fixed Receiver of Incoming Air Flow

It is noted that it is necessary to obtain reliable information about air signals that determine the spatial movement of aircraft plane (AP), including small-sized, unmanned and manned, to ensure flight safety in the surface disturbed layer of the atmosphere. It is shown that traditional air data systems of AP implementing aerodynamic and wind cock methods for measuring the parameters of incoming air flow using air pressure receivers installed on the right and left side and distributed over the fuselage, braking temperature receiver and wind cock sensors of aerodynamic angles of incidence and gliding have a complex design, considerable weight and cost, which limits their use on small-sized, unmanned and other aircraft classes. It is noted that the developed air data system with one fixed receiver of incoming air flow, built on the basis of the vortex method for measuring the parameters of incoming air flow, can significantly simplify the design and reduce the mass of system, but provides measurement only in the azimuthal or vertical plane in a limited range of measurement of the aerodynamic angle. The air data system being developed, which implements an ion-mark method for measuring the parameters of incoming air flow, allows for panoramic measurement of the aerodynamic angle, but also only in one plane with increasing complexity of the design and increasing requirements for the identity of the channels of the multichannel measuring circuit, which also limits their use on small-sized aircraft. The known capabilities and advantages of the ultrasonic method for measuring the parameters of gas flows and a panoramic sensor of the aerodynamic angle and true airspeed with a fixed receiver of the incoming air flow have determined the possibility of using the ultrasonic method for spatial measurement of air signals. The functional scheme of the electronic system for spatial measuring air signals of aircraft plane with one (integrated) fixed receiver of incoming air flow and ultrasonic instrumentation channels connected to the input of the computer is revealed. To expand the functionality, a static pressure receiver-hole is installed on the external streamlined surface of the system’s receiving board, connected by a pneumatic channel to the input of an absolute pressure sensor with a frequency output, which is also connected to the input of a computer, at the output of which digital output signals of the air data system of aircraft plane are generated. Analytical models of informative signals and algorithms for spatial determination of air signals in instrumentation channels of the electronic system with one fixed receiver of incoming air flow are obtained. The essential advantages of the considered electronic system are revealed, which increase the competitiveness and efficiency of the system application on small-sized and other classes of aircraft planes to improve flight safety and the efficiency of solving flight tasks.

Development of a Model for Predicting Brake Friction Lining Thickness and Brake Temperature

Road traffic injuries and deaths are a growing public health concern worldwide, majorly in developing countries. Brake failure constitutes to be one of the primary reasons for accidents. The majority of brake failures are caused due to overheating of the brakes, while wear of lining is another big share-holder. Early detection of such causes can prevent these accidents. This study puts forth a model that can be used for onboard monitoring of drum/disc temperature & lining/pad thickness by taking velocity & road inclination in real-time as inputs. Many quantities are interdependent and vary with respect to time/temperature. Therefore, an incremental approach is used. The model is implemented in the Simulink software. Many standard profiles are also fed to compare results for different terrains and driving conditions. The drivers can also be classified based on their driving behavior. The thermal model can give us an early warning about the brake overheating. This model can be used to study the energy distribution while braking. Researchers and designers can also use this model to study & optimize the brake system.

Experimental study of the effect of brake drum cooling grooves on motorcycle braking performance

Some important indicators in the braking system performance on a motorcycle are the braking temperature and stopping distance. High temperatures due to frictional heat in the drum brake can decrease the braking force and cause a slip. To improve braking performance, an effective strategy is needed to reduce the drum temperature and shorten the stopping distance. This study aims to analyze the effect of cooling grooves on the standard brake drum to decrease the drum brake temperature and the length of stopping distance. The measurements were compared to the standard drum brake as a reference, and two types of the modified ones to increase the braking performance by adding the slant-grooved and a straight grooved on brake drum. Braking is performed by providing a compressive load of two kg on the brake pedal for three cases of motorbike speed: 20, 40, and 60 km/hour. The results show that the brake drum with straight cooling grooves provides better braking performance compared to other drum brakes. For a speed of 60 km/h, the temperature of the straight grooved brake is 3.5 ºC. The stopping distance is 29.1 % shorter compared to the standard one. It shows that adding cooling grooves on drum brake can increase the effectiveness of motorcycle braking performance at various speeds. The results show that the brake drum with straight cooling grooves provides better braking performance compared to other drum brakes

Noise and vibration performance of automotive disk brakes with laser-machined M-shaped grooves

This work makes use of experimental and numerical studies to investigate the reduction of braking noise and vibrations of brake disks by introducing various M-shaped grooves on the brake disk frictional surfaces. Experiments with a brake test dynamometer have been carried out to compare the braking vibrations and noise of the grooved disks with that of the un-grooved disk. The experimental results demonstrate that disks with grooves significantly reduced braking vibrations and noise at both low and high frequencies, and as the initial braking temperature and braking pressure increased, the reduction effect is further enhanced. The investigation also shows the wear rates of both the grooved disks and brake pads are also significantly reduced. Thermo-mechanical coupled finite element models of the brake pads and disks with and without grooves are developed to investigate the mechanisms of the reduction of braking noise and vibrations by the introduction of grooves on the disk frictional surfaces. The numerical results show that the number of grooves plays an important role in reducing the interface surface temperatures, enhancing heat flux, reducing thermal deformation, changing the contact pressure distribution, and stabilizing the coefficients of friction of the braking sliding contacts. The thermal effects contribute to the wear reduction of both the braking disks and pads, and the reduction of braking noise and vibrations. In addition, both the finite element modal analysis and the experimental modal testing results show that surface grooves increase the modal damping ratio of the disks, which certainly plays a role on the reduction of braking noise and vibrations. This study has significance to the surface modification of brake disks in order to reduce braking noise and vibrations, as well as the wear resistance of brake disks and pads.