Corrosion Phenomena in Braking Systems

The vibration and noise issues of lightweight friction pairs in suburban train braking systems have become a critical bottleneck restricting their engineering application. This study investigated the lightweight friction pairs composed of three representative synthetic brake pads and an aluminum matrix composite brake disc. Utilizing tribological tests, interfacial wear analysis, and dynamic modelling, the study investigated the impact of interfacial wear and contact behaviors on vibration and noise, and elucidated the mechanisms by which pad material properties influence these responses. The experimental findings revealed that the pad material properties significantly affect the wear behavior and friction-induced vibration and noise responses of lightweight friction pairs. The pad enriched with lubricating phases (Pad A) readily established stable lubricating films, while the highly plastic pad (Pad C) effectively captured wear debris to build the third-body layers that cushioned loads. Both reduced friction fluctuations and contact stiffness, thereby attenuating vibration and noise. Conversely, the high-hardness pad (Pad B) failed to form continuous lubricating films, leading to intensified friction, higher contact stiffness, and pronounced vibration and noise. Numerical simulations further confirmed that the friction coefficient and normal contact stiffness synergistically regulated system stability, directly affecting the vibration and noise responses. Systems characterized by high friction and large contact stiffness (Pad B) were particularly susceptible to modal coupling, resulting in dynamic instability and elevated vibration and noise levels. Therefore, optimizing the pad material properties and regulating the behavior of wear debris to facilitate the stable formation of lubricating films or third-body layers can effectively suppress friction coefficient fluctuations, reduce normal contact stiffness, and enhance interfacial stability, thereby mitigating vibration and noise. The findings provide a theoretical foundation and engineering guidance for optimizing the design of low-noise lightweight braking systems and selecting appropriate friction materials.

Wear behavior of a low metallic friction material dry sliding against a cast iron disc: Role of the heat-treatment of the disc

Chapter 6 - Brake system layout design

The paper focuses on issues related to selected automotive brakes with the aim of applying the proposed methodology to other structural systems of this type. The main aim of the paper is to identify the factors that differentiate the course of wear and occurrence of a fault in brake system components of passenger cars and light commercial vehicles during the warranty service period. The following methods were used in this study: systematic literature review, process analysis, and descriptive and inferential statistics, including analysis of variance and multiple classification analysis. As a result of an analysis of 295 brake system repairs, six differentiating factors that allowed for ex post analysis of the repairs were identified. An analysis of the interaction of these factors made it possible to distinguish three groups of motor vehicles depending on the cause of failure of the braking system. Based on the data generated in the warranty process, it is possible to determine the factors that differentiate the occurrence of a fault and the course of brake disc and pad wear.

In the process of enhancing the braking safety and performance stability of the automotive braking system, comprehensively considering the failure modes of the braking system and obtaining an accurate reliability function model are crucial for completing the reliability-based robust optimization design (RBROD) of the braking system. In engineering practice, the modal characteristics and thermal-mechanical coupling reliability robust design method under multiple failure modes encounter problems such as low computational efficiency and difficult problem-solving. To tackle these issues, this paper proposes a new method called Reliability-Based Robust Optimization Design under Multi-Failure Mode (MF-RBROD). In the proposed optimization method, the deep learning surrogate model replaces the experiments and finite element analysis (FEA) in the original adaptive process, greatly saving time and cost. The accuracy of the finite element model is determined by comparing the modal experimental results with the finite element analysis results of the disc brake. A total of 300 training samples and 50 testing samples were obtained. After establishing the reliability performance function through samples, among the four surrogate model methods, the DL-AK method with the smallest average relative error was selected to conduct a reliability sensitivity analysis of the braking system. The error of this method is only 0.01911%, which is significantly better than the other three surrogate models. The MF-RBROD model was formed by weighted transfer method. The MF-RBROD method has effectively improved the reliability of the disc brake. Specifically, the frequency reliability has been significantly enhanced from 0.9414 to 0.9971, while the thermo-mechanical coupling reliability has been raised from 0.9483 to 0.9951. At the same time, the sensitivities of various design parameters affecting the braking system reliability and the total mass of the disc brake were significantly reduced. The optimization results of the disc brake have demonstrated the effectiveness of the MF-RBROD method.

Chapter 3 - Braking system design for passenger cars and light vans

Aiming at the problems existing in the design of the braking system of the student driverless formula racing car, such as difficulty in ensuring braking stability and long response time, research and design were carried out, and the advantages and disadvantages of the hydraulic braking and pneumatic braking systems were analyzed to achieve Air pressure is directly converted into oil pressure, and the design of the air and oil circuits is optimized at the same time. Its working status under driverless driving conditions is controlled through EBS (emergency braking system). It participated in the National Student Driverless Formula Competition and verified the braking System’s stability and reliability.

<div class="section abstract"><div class="htmlview paragraph">The most used rotor material is gray cast iron (GCI), known for its susceptibility to corrosion. The impact of corrosion on the braking system is paramount, affecting both braking performance and the emission of particulate matter. The issue becomes more severe, especially when the brakes are left stationary or unused for extended durations in humid conditions, as seen with electric vehicles (EVs). Brake disc corrosion amplifies the risk of corrosion adhesion between contacting surfaces, leading to substantial damage, increased quantity and mass of non-exhaust particulate emissions, and decreased braking effectiveness. In addition, brake pads' friction material plays a crucial role in generating the necessary stopping force, creating friction that transforms kinetic energy into heat. However, heightened pressure during braking elevates rotor temperatures, contributing to the degradation of the friction material. This degradation manifests in decreased mechanical strength, heightened pad-to-rotor force, wear, and reduced braking efficiency. To address all these challenges and meet the stringent Euro7 particulate emission standards, we have developed controlled wear-resistant nitrocarburized layers on cast iron surfaces with customizable thicknesses, compositions, and porosity coupled with a new generation of post-oxidized layers referred to as Smart-ONC®. These layers, known for their remarkable "self-healing" capabilities, are formed through a controlled, in-situ post-oxidation process by incorporating additional metals into the oxide layer to enhance corrosion resistance and fortify the surface against damage and potential failures. the dyno tests validated the integrity of the FNC-Smart ONC (Ferritic nitrocarburizing-Smart oxidation of the nitrocarburized layer) layers, affirming their ability to preserve mechanical properties without experiencing wear, delamination, or cracking. Notably, FNC-Smart ONC discs demonstrate pad material accumulation, effectively sustaining braking performance as an additional protective interface between pads and discs.</div></div>

Brake friction materials play an important role in automobiles to reduce speed and to stop the vehicles. Advances in friction materials were updated to ensure effective performances in braking systems and to provide the maximum safety and comfort. Presently eco-friendly friction materials have been used as a replacement for conventional friction materials. Many synthetic and natural products were identified and claimed as better alternatives to banned toxic materials like asbestos and copper. Friction materials developed from natural products are eco-friendly and assure a great promise when applied in modern vehicles. To develop innovative formulations, basic knowledge of common ingredients and their effects in friction materials was needed. This review focuses mainly on providing detailed information about the common ingredients used, processing methods and the characteristics of brake friction materials.

The tribological and thermal properties enable iron based sintered materials with hard phase ceramic reinforcements as promising friction material for heavy-duty wind turbines. In wind turbines, the braking system consists of aerodynamic and mechanical braking systems. During application of mechanical brakes, the friction materials are pressed against the rotating low-speed shaft. The desired braking efficiency is achieved by utilizing a number of friction materials, which in turn are joined in a steel backing plate. Though this arrangement increases the braking efficiency, the hard phase ceramic reinforcement particles reduces the bonding strength between the friction material and steel backing plate. The joint failure leads to catastrophic failure of wind turbine. Therefore, the need of the hour is to develop friction materials with functional gradients that have high wear resistance (contact area) and high bond strength (interface). In this study, an attempt is made to fabricate and characterize a friction material with gradient profile of composition along the cross section to provide functional gradient property. The functional gradient friction material is synthesized by gradient deposition of Fe, Cu, Cg, SiC and fly ash powders which is then compacted and sintered. The prepared functional gradient friction material was characterized in terms of microstructure and microhardness. The tribological performance (wear rate and coefficient of friction) of the developed functionally gradient friction material was investigated at various loads using pin-on disc apparatus. The results show that as the load increases, the wear rate decreases and at the same time the COF tends to increase at higher loads. The predominant wear mechanism was deduced from the morphology of the worn surface.

The following work encompasses the design of a disc braking system for a single seated solar electric racing vehicle and serves as a guide for developing a desired braking system for various student racing competitions. The basic aim of this work is to design and fabricate a safe, reliable and an efficient hydraulic braking system according to the required standards .Reliability, lightweight materials, manufacturing ease and costs, maximum braking force, safe stopping distance and manageable temperature are some of the considerations done for the braking system. Modelling and simulation are done in Spaceclaim 2020 and Ansys 2020R2.Topology optimization of brake disc is done to reduce the weight of the braking system done. This brake system is designed according to the rules and regulations of ESVC organized by ISIE and accredited by Ministry of New and Renewable Energy, Government of India and Ministry of MSME, Government of India.

Thermally sprayed WC-based coating systems are generally used to increase engineering components’ wear resistance. This research presents the results of a comparative study conducted to examine the tribological characteristics of a new brake disc created with thermal sprayed WC-10Co4Cr coating. This study implemented braking tests on the WC-10Co4Cr coated brake disc against commercial friction material on a laboratory scale disc-pad tester and compared the findings with the reference disc. The coating system was created with a high velocity oxygen-fuel spraying on a cast iron disc. The braking tests followed the sections of the SAE-J2430 test procedure. The microstructure, phase composition and properties of the coating were characterized by SEM/EDS, XRD and Vickers microstructure. The effect of carbide coating on the friction and wear behaviour of the tribological system was examined. The WC-10Co4Cr coating has increased the hardness by 3 times with a thickness of 300 μm compared to the cast iron surface. The amount of wear in the coated disc (CD) was reduced by about 85% compared to the reference disc (BD). The coefficient of frictions of BD and CD was found to be in the range of 0.43–0.61 and 0.47–0.62, respectively. The inclusion of hard phases (WC and W2C) in the disc coating played an important role in improving the sliding wear resistance by maintaining the coefficient of friction of the brake disc at an acceptable level. In brief, carbide coating could be claimed to be promising for challenging braking implementations.

Safety aspect in automotive engineering has been considered as a number one priority in development of new vehicle. Each single system in brake system has been studied and developed in order to meet safety requirement. Instead of having air bag, good suspension systems, good handling and safe cornering, there is one most critical system in the vehicle which is the braking systems. If there is no proper braking system in the vehicle the passenger in the vehicle is in unsafe position. Therefore, it is a must for all vehicles to have proper braking system. Due to critical system in the vehicle, many of researchers have conducted a study on brake system and its entire component. In this project, we have conducted a study on performance of normal disc brake rotor of normal passenger vehicle at different speeds when different materials are used. The study is more likely concern of Stress distribution on disc brake rotor and deformation and stresses developed on it due to different speeds. The widely used brake rotor material is cast iron which consumes much fuel due to its high specific gravity. The aim of this project is to select the optimum material for the application of brake disc system emphasizing on the substitution of this cast iron by any other lightweight material. The present project is aimed to study the given disc brake rotor for its stability and rigidity, for this Thermal analysis and coupled structural analysis is carried out on a given disc brake rotor to find out its deformation, stress when different materials are used. For these three different materials in each case is analyzed. KEYWORDS: Disc brake, Disc brake rotor, CATIA, ANSYS

In braking systems, which consist of dry sliding lining against a pearlitic cast-iron disc, disc wear has a significant impact on the overall wear rate. In this work, dynamometer tests were conducted to find out the friction and wear behaviour of 20NiCrBSi-WC12Co cermet coating accumulated on the cast-iron disc by High velocity oxy-fuel spraying (HVOF) and the findings were compared with those of the uncoated disc. Braking tests of the coated and uncoated discs were performed on a full-scale brake dynamometer, which was designed in line with the SAE-J2430 Brake Effectiveness Procedure. Microhardness values, surface properties, scanning electron microscopy (SEM) analysis, energy dispersive x-ray (EDX) and x-ray diffraction (XRD) analysis of the discs were evaluated. As a result of these analyses, it was found out that cermet coating had a much higher microhardness and abrasion resistance with the combination of hard WC phase and mild Ni matrix compared to the conventional disc. The coated disc exhibited stable braking effectiveness with lower surface contact temperature. At the same time, this coating results in longer service life by reducing abrasive wear on the brake disc surface and a lower lining wear rate, reducing particle matter emissions to the environment.

The characteristics of electro-hydraulic braking systems have a direct influence on the fuel consumption, emissions, brake safety, and ride comfort of hybrid electric vehicles. In order to realize efficient energy recovery for ensuring braking safety and considering that the existing electro-hydraulic braking pressure control systems have control complexity disadvantages and functional limitations, this study considers the front and rear dual-motor-driven hybrid electric vehicle as the prototype and based on antilock brake system (ABS) hardware, proposes a new braking pressure coordinated control system with electro-hydraulic braking function and developed a corresponding control strategy in order to realize efficient energy recovery and ensure braking safety, while considering the disadvantages of control complexity and functional limitations of existing electro-hydraulic system. The system satisfies the pressure coordinated control requirements of conventional braking, regenerative braking, and ABS braking. The vehicle dynamics model based on braking control strategy and pressure coordinated control system is established, and thereafter, the performance simulation of the vehicle-based pressure coordinated control system under typical braking conditions is carried out to validate the performance of the proposed system and control strategy. The simulation results show that the braking energy recovery rates under three different conditions—variable braking intensity, constant braking intensity and integrated braking model—are 66%, 55% and 47%. The battery state of charge (SOC) recovery rates are 0.37%, 0.31% and 0.36%. This proves that the motor can recover the reduced energy of the vehicle during braking and provide an appropriate braking force. It realizes the ABS control function and has good dynamic response and braking pressure control accuracy. The simulation results illustrate the effectiveness and feasibility of the program which lays the foundation for further design and optimization of the new regenerative braking system.