Browse Topic: Friction materials

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Development of an Electronic Braking System Applied to Commercial Vehicles Focused on Improvement of Braking Pedal Feeling and Braking Performance2026-36-03087/30/2026
Embedded electronics are becoming increasingly common in solutions developed for commercial vehicles. Technological advancements enabled the development of electronic solutions that provide braking systems with functions to improve safety, comfort, performance, durability, and cost-effectiveness of wear components. In this context, the electronic braking system, EBS, has become increasingly present in the electronic architecture of commercial vehicles. Considering the functions that can be developed within the electronic braking system, the following stand out: the pedal characterization, which potentially improves comfort and increases the sensation of safety during braking; and the brake force distribution, which can be adjusted to ensure that the vehicle achieves an optimal balance between performance and friction material’s durability. This work consists of the presentation of tests and results of technical activities required to develop an EBS for medium-heavy and heavy-duty vehicles designed for a variety of applications. EBS was developed to prioritize comfort and safety, with optimized braking sensation and performance without compromising the durability of the wear components of the vehicles. Activities started with the experimental determination of the brake factor—a value that transmits to EBS the braking capacity of the truck. In sequence, brake pedal setup was performed based on data extracted from a vehicle equipped with a mechanical braking system and validated by subjective assessment. In addition, the braking force distribution definition started by establishing its target: friction material’s wear equalization or braking performance; went through balancing the mechanical braking power per axle; and finished being validated by data obtained from vehicles in use. Results showed that the implementation of electronic braking systems in commercial vehicles brought several benefits to the product, in particular, improvement of braking feeling when pressing the brake pedal, and in both braking performance and friction material’s durability, which resulted in a better balance between maintenance costs and technical advantages.
Travaglia, Carlos A. P., Rodrigues, André, Rudek, Claudemir, Dias, Eduardo Miranda, Silveira, Juliana
2025 International Conference on Solid Mechanics and Materials2026-99-16007/24/2026
TOC
Tobolski, Sue
Influence of Modified Fly Ash Content on the Properties of Resin-Based Friction Materials2026-99-16577/24/2026
In this study, five resin-based brake pad samples with modified fly ash contents of 0%, 4%, 8%, 12%, and 16% were prepared to investigate the influence of fly ash content on the comprehensive performance of the friction materials. The tribological properties of all samples were evaluated under temperature conditions ranging from 100 °C to 350 °C, and their overall performance was assessed using five evaluation indices. Based on the AHP-MOORA algorithm, sample F12 exhibited the highest comprehensive weighted score of 0.11, followed by samples F0 and F8 with scores of 0.10 and 0.09, respectively, indicating a slight decline. In contrast, the comprehensive weighted scores of F4 and F16 were relatively low, at 0.05 and −0.01, respectively. Among the five composites, F12 demonstrated the best overall performance, with F0 and F8 ranking next, while F4 and F16 performed poorly. These results suggest that, within a certain range, increasing the fly ash content can enhance the comprehensive properties of the material. However, excessive addition of fly ash may lead to the detachment of harder particles during wear, thereby increasing wear thickness and wear rate.
Li, Xiaobiao, He, Kang, Zhao, Zhuanzhe, Wu, Bo, Sun, Fei
Clutch Thermal Adequacy Assessment in Repeat Restart Launch Conditions on Gradient2026-26-04341/16/2026
The clutch is a mechanical device that connects and disconnects engine power to the drivetrain through the clutch disc and cover assemblies. The disc, with friction material linings is mounted on the transmission shaft, transmits power when clamped between the flywheel and cover assembly. During operation, wear occurs due to speed differences and slippage between the engine and transmission. Clutch performance is evaluated under repeat restart conditions on steep gradients to assess thermal durability and reliability in commercial vehicles. The repeat restart test on a 12% gradient replicates truck launches under full load, where excessive slippage generates heat that may lead to friction material wear or failure if critical temperature limits are exceeded. To address the high cost and time of physical testing, a 1D thermal simulation was developed using GT Suite. The model replicates 90 repeat vehicle launches on a 12% gradient in first gear, integrating driver inputs and drive cycles to predict clutch housing air temperatures. The simulation shows a 95% correlation with test data, validating its accuracy and reliability. This virtual approach enables early-stage design validation and optimization of parameters influencing heat generation and thermal degradation, minimizing dependence on physical trials and reducing development time. Applied to heavy commercial vehicles, this methodology supports design of experiments for drivetrain parameter analysis, guiding optimal configurations that minimize thermal stress. The adoption of GT Suite as a digital validation tool improves product development efficiency, lowers warranty costs, and enhances product quality. It provides a strategic advantage in competitive markets through faster, data-driven decision-making and enables more reliable and robust clutch design in early development stages.
Munisamy, Sathishkumar, Chollangi, Damodar, Mane, Sudhir
Niobium Alloyed Brake Disc for reduced NVH and Emission Control2026-26-02851/16/2026
Recent regulations limiting brake dust emissions have presented many challenges to the brake engineering community. The objective of this paper is to provide a low cost, mass production solution utilizing well known existing technologies to meet brake emissions requirements. The proposed process is to alloy the Gray Cast Iron with Niobium and subsequently Ferritic Nitrocarburize (FNC) the disc. The Niobium addition will improve the wear resistance of the FNC case, reducing wear debris. The test methodology included: 1. Manufacture of disc samples alloyed with Niobium, 2. Finish machining and ferritic nitrocarburizing and 3. Evaluation of airborne wear debris utilizing a pin-on-disc tribometer equipped with emission collection capability. The airborne emission and wear surfaces were further analyzed by Scanning Electron Microscopy, Energy Dispersive techniques (SEM-EDS), X-Ray Diffraction and Optical Microscopy. The cast iron test matrix included four groups; Unalloyed eutectic 4.3% Carbon Equivalent (CE), Unalloyed hypereutectic >4.3% CE, Niobium alloyed Eutectic and Niobium alloyed hypereutectic gray cast iron. The results demonstrate the advantages of Niobium alloyed FNC treated discs in reduced wear and meeting Euro7 airborne emission requirements. The Niobium alloyed eutectic Gray Cast Iron plus FNC treatment exhibited the best wear debris performance for both the Non-Asbestos organic (NAO) and Low Metallic (Low Met) friction materials. The Niobium alloyed hypereutectic Gray Iron plus FNC treatment also performed well with both NAO and Low Metallic friction materials.
Barile, Bernardo, Holly, Mike
Investigation of Particulate Matter Emissions from Brake Pads of Light-Duty Vehicles: A Comparative Analysis of Friction Material Compositions2025-36-020012/18/2025
Studies correlate air pollution with an increase in the incidence of respiratory diseases, affecting lung function and raising hospitalization rates. Among the pollutants associated with these diseases, inhalable coarse particulate matter (PM10) and fine particulate matter (PM2.5) stand out. The emission of particulate matter resulting from the wear of brake pads in light vehicles is the second largest source, accounting for approximately 33% of a vehicle’s total emissions. The particulate matter generated during the braking process can be analyzed through its collection in tests conducted on dynamometers, using enclosure and sampling systems. The development of the dynamometer used was based on the braking cycles described in the SAE J2522:2003 standard, whose main objective is to provide comparative data on different friction materials. Given the variations in particulate matter emissions depending on the composition of the brake pads, as reported in the literature, this study presents an analysis of the emissions from two distinct formulations, as well as a comparison of wear parameters and the surface roughness of the pads. The characterization of the particulate matter was carried out using a sampling system in accordance with ISO 9096:2017, with a sampling duct aligned with the flow duct downstream of the enclosure chamber, and particle retention achieved through fiberglass filters. The airflow velocity was controlled to ensure isokinetic transport conditions in the sampling system, adjusting the connected pump to match the probe velocity. The results show that wear was not uniform between the pairs of brake pads, also revealing differences in the chemical composition of the particulate matter according to the different formulations, consistent with what is reported in the literature, but with similar particle concentrations by size.
Catão, Vítor Gustavo Gomes, Machado, Amanda Ribeiro, Fiorentin, Felipe Klein, Silva, João Pedro Anuto, Bernardino, Lucas Gabriel, Fiorentin, Thiago Antonio, Carboni, Andrea Piga
Study on the Clarification of the Mechanism of Scooter Centrifugal Clutch Squeal2025-32-002211/3/2025
A centrifugal clutch is used in many machines such as scooters, lawn mowers, outboard motor of boats, brush cutters, and so on. It may produce a shrill sound, similar to a brake squeal, when the clutch engages for starting. In this study, we have proved that this shrill sound, in another word, clutch squeal, is caused by the self-excited vibrations of the centrifugal clutch. And we have also clarified that the clutch squeal can be restrained by employing an asymmetrical shape for the clutch housing. The clutch squeal tends to occur when the centrifugal clutch becomes hot due to repetitive starting and stopping, which causes the friction coefficient of the friction material on the clutch shoe to increase. It is presumable that vibration on the clutch housing generated by the self-excited vibrations is the cause of the clutch squeal. In an attempt to clarify the cause of clutch squeal, we first measured the sound pressure of the clutch squeal and the vibration shapes of the clutch housing when the squeal occurred. Then, using the complex eigenvalue analysis, which is one of the finite element methods, we got unstable modes of the centrifugal clutch that could lead to self-excited vibrations. By conducting a comparative verification of each result, we have proved that the cause of clutch squeal is the higher frequency self-excited vibrations in the centrifugal clutch. And using the complex eigenvalue analysis, we gained the perspective that applying an asymmetric shape to the clutch housing is a prospective solution to restrain the generation of unstable modes, and this was verified by testing with an actual scooter.
Yamamoto, Kohei, Iwamoto, Tatsuya, Otsuka, Takashi
Thermal Performance Evaluation Methodology for Wet Clutch: Simulation and Testing Correlation2025-28-037210/30/2025
This paper describes a simulation methodology developed to predict the temperature distribution in separator plate and friction disc of the wet clutch corresponding to given slip power, oil flow rate and clutch geometry for off-highway applications. This study adopts a model-based design approach to understand thermal behavior of the wet clutch. This simulation methodology has been developed in a 1D environment with the right fidelity modeling approach to predict thermal performance of the clutch. This model includes heat flow through conduction and convection corresponding to heat generated due to friction between separator plate and friction material. Lab test includes multiple thermocouples installed on separator plate to capture temperature distribution in radial direction. This methodology has been correlated >90% with test data acquired in the lab. This dynamic simulation model aids to identify the potential root cause of clutch failures and risk mitigation. DOE has been performed to assess the impact of various parameters like separator plate thickness, friction disc groove geometry and oil flow rate on the surface temperature and oil exit temperature. This methodology can be used to develop new predictive simulation workflows to address design issues in virtual environments with significant reduction in product development time, cost and risks associated with lab and field tests.
Kumar, Suneel, Memane, Nilesh, Veerkar, Vikrant
Development of an SSP-180 Synchronizer Durability Test2025-01-040810/7/2025
Synchronizers are designed to provide smooth, efficient and safe transfer of torque between mechanical gears. Friction level, durability, and consistency of the fluid / friction lining system are crucial to ensuring crisp gear engagements without clashing and noise, vibration and/or harshness (NVH) for the life of the transmission. Excellent wear control of gears, synchronizer ring and cone surfaces is also critical to protecting the life of moving mechanical parts. The SSP-180 synchronizer rig measures friction durability and wear up to 100,000 engagements, using a variety of fluids and friction materials. Methodology for the development of a synchronizer durability procedure using the SSP-180 rig is presented for qualifying fluids for dry dual clutch (DCT) and manual transmission (MT) applications for General Motors. It will be shown that the new DEXRON® SSP-180 Synchronizer Durability Test in Appendix C of the GMW 16612 fluid specification [1] satisfies four key conditions for new mechanical test methods: discrimination, repeatability, effective failure mode analysis, and reasonable test duration.
Glasgow, Michael B., Zreik, Khaled, Ezanno, Philippe Nicolas, Shelton, Robert W.
Development of a Laboratory Brake for a Flywheel Mass Test Rig for Variable Pad Sizes and Shapes with a Force Distribution Unit for Ideal Contact Pressure and a Topography Measurement System for In-Situ Recording of Surface Changes and Wear2025-01-03319/15/2025
Pin-on-disk tribometers are used to determine the frictional behaviour and boundary layer dynamics of material pairings. Material pairings are examined under defined conditions in order to reason about the friction behaviour and wear. Pairings for real brake systems with larger pad sizes can be tested on flywheel mass test rigs in order to provide proof of suitability. This is mainly due to a lack of knowledge about the scaling behaviour of friction linings. The Department of Machinery System Design at TU Berlin has combined the classic approach of a pin-on-disk tribometer with a flywheel mass test rig (up to 12.78 kgm2) and thus set up a laboratory brake on which material pairings with different pad shapes and sizes (up to 48 cm2) can be examined. The flywheel mass test rig consists of an adjustable DC-motor that drives a shaft on which variable flywheel masses and brake disks can be installed. The variability allows for different kinetic energies at different friction speeds. The test stand also has a linear table on which the pad sample holder sits. The specified braking force is generated by a hydraulic cylinder. The normal force is applied to the friction lining sample by means of a force expansion and distribution unit. This expansion ensures a uniform contact force over the entire pad surface, which has been designed with FEM simulations and proven with pressure measurement film. Different force expansions are possible for different pad geometries. During the tests, the torque, the forces in the normal and tangential directions, the temperature of the brake disk and lining sample as well as the speed are recorded using NI measuring cards and corresponding sensors. Furthermore, the lining sample can be moved with the linear table to a topography measuring unit including a camera system. By using the linear table and a laser distance sensor mounted on a linear motor, the topography of the lining sample is recorded and images can also be taken. This flexible setup allows to record the topography between individual braking operations without the need for long changeover times. The laboratory brake can be used to investigate the influence of brake force distribution on the friction process. Topographical changes can be observed in situ in between braking operations. The test rig has already been used in an initial series of tests and the first results of a running-in process of a material pairing consisting of a gray cast iron disk and an organic friction lining for truck brakes are shown.
Heuser, Robert Michael, Rosenthal, Tobias Richard, Wiest, Daniel Christian, Meyer, Henning Jürgen
Effects of Moisture Behavior on Corrosion Stiction in Friction Materials2025-01-03339/15/2025
This study investigates the correlation between moisture behavior and corrosion stiction mechanisms in NAO friction materials. While previous studies on corrosion stiction have primarily focused on electrochemical approaches, this study aims to elucidate the mechanism by examining moisture behavior within the friction material. Although recent research has investigated changes in pad properties in humid environments, most studies have primarily focused on variations in pad stiffness and the friction coefficient. To date, no studies have investigated the behavior of moisture within pads using Fick’s Second Law and its impact on corrosion stiction. In this study, Fick’s Second Law was applied to model moisture behavior in friction materials. The diffusion coefficient and maximum moisture content were quantified, revealing that moisture behavior in the friction material can be divided into two distinct stages: one following Fick’s Second Law and the other not. For NAO friction materials, experimental results indicate that a higher diffusion coefficient and lower maximum moisture content - leading to faster surface saturation- exacerbate corrosion and increase the risk of corrosion stiction. These findings highlight the importance of managing moisture behavior in friction materials to mitigate stiction-related issues. Further research is needed to examine the impact of lubricating films formed after burnishing friction material.
Choi, Nakcheon, Ju, Joungsu, Youn, Deokki
Water Interaction and Its Effect on the Tribological Behavior of NAO Friction Materials2025-01-03369/15/2025
Moisture is known to be a relevant factor during a friction material life, affecting tribological behaviors such as friction coefficient and torque variations. In this study we investigated the interaction between friction materials and water; employing various techniques such as contact angle measurements, water adsorption, and exposure to controlled environmental condition changes. Focusing on NAO friction material, mix modifications were studied to highlight differences and understand mechanisms, in particular, organic content and hydrophobic agents, were examined. Characterization results showed that brake pads hydrophobicity can be influenced by water interaction conditions; even low-wettability surfaces, such as those treated with hydrophobic modifiers, can still absorb water depending on internal factors (e.g., porosity) and external conditions (e.g., contact time, humidity). Additionally, we investigated the capacity of a friction material to adsorb water and desorb it back to its initial state. Climatic chamber tests revealed that under high-humidity conditions, the differences between materials were minimized. Following this characterization, the materials were tested with Bruker UMT tribometer to assess how different conditioning treatments influence the tribological response, with particular emphasis on vibrations.
Iodice, Valentina, Durando, Pietro, Balestra, Simone, Pellerej, Diego
Influence of Titanate Composition and Particle Size on Friction Stability and Wear in Brake Pads2025-01-03379/15/2025
The effects of particle size and composition of platelet titanates, including potassium titanate and potassium-magnesium titanate, were investigated to determine their friction stability, wear resistance, and transfer film formation. The composition and properties of titanates were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), and particle size analysis. Tribological properties were evaluated using a tribometer (MFT-5000), while the worn surfaces were analyzed with scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Results indicate that the transfer film characteristics are significantly influenced by the particle size and composition of platelet titanates. Brake pads containing potassium-magnesium titanates formed a more uniform transfer film, leading to improved friction stability and reduced wear rates. In contrast, potassium titanates increased friction levels but also resulted in higher wear on the brake friction materials. These findings demonstrate the importance of carefully controlling titanate composition and particle size to enhance brake pad performance. This research provides valuable insights for designing more durable and stable brake materials.
Jara, Diego Chavez, Lorenzana, Carlos, Sliepcevich, 1Lt Andrea, Conforti, Michael
Further Investigation of Disc Pad Compression Deformation during ISO Compressibility and Dynamic Modulus Measurements under Relatively Low Pressures2025-01-03349/15/2025
In an earlier publication, it was reported that the pad compressibility measured under 160 bars on NAO formulas keeps decreasing with increasing number of repeated measurements due to unrecoverable residual deformation of the friction material combined with increasing moisture adsorption, which increases the hardness of the friction material. This current investigation was undertaken to find out if this same phenomenon occurs for NAOs under a low pressure of 100 bars during compressibility measurements and under 700N during dynamic modulus measurements. In all cases, it is found that the same phenomenon occurs, meaning that friction materials become permanently compressed without full recovery, making them harder to compress and raising up the modulus. The dynamic modulus of friction material attached to a backplate is found to be lower as compared with the friction material without the backplate, which is caused by more rapid moisture adsorption of friction material pads without a backplate. As pad properties are continuously changing under pressure at temperature during usage, compressibilities and dynamic moduli measured for the initial quality must not be used for predicting brake performance/NVH – an important issue for AI databases.
Sriwiboon, Meechai, Rhee, Seong Kwan, Sukultanasorn, Jittrathep
A Novel Framework for Elastic Constants and Damping Ratio Optimization of Friction Material in Brake Squeal Simulations2025-01-03509/15/2025
Friction material properties critically impact brake squeal simulation outcomes due to their nonlinear and transversely isotropic behaviors, which vary with load type and direction. To improve the reliability of brake squeal predictions, this study introduces the Transversely-isotropic Elastic Constants Optimization (TECO) method, a novel multi-dimensional constrained optimization framework for refining the elastic constants and damping ratio of friction materials. By integrating experimental testing, finite element analysis (FEA), and an advanced optimization technique - Gradient Response Surface Algorithm (GRA), the TECO method minimizes discrepancies between simulated and experimental data, ensuring accurate characterization of elastic properties. The TECO method offers significant advantages, including flexibility and robustness, making it an effective alternative to ultrasonic measurements and traditional optimization techniques, especially for anisotropic friction lining materials. Unlike existing approaches, TECO imposes no restrictions on the number of defined modes, allowing accurate characterization with fewer input data points. Its iterative process ensures strong correlation between experimental and simulated results while preserving essential modal attributes, such as natural frequencies and mode shapes. Focused on drum brake squeal prediction, the TECO method enhances complex eigenvalue analysis (CEA) by incorporating friction material properties measured under actual squeal loading conditions. This approach yields highly correlated NVH simulation models at the component level, providing a reliable framework for brake squeal analysis and design. By advancing the predictive accuracy of brake squeal simulations, the TECO method offers a versatile and effective solution for characterizing friction material properties, contributing significantly to noise, vibration, and harshness (NVH) optimization strategies in braking systems.
Philip, Rony, Muralidharan, Sudharsan, Mohanam, Gopalakrishnan
Achieving Euro 7 Compliance: Cost-Effective Brake Wear Particle Emissions and Performance with FNC-Smart ONC® GCI Rotors2025-01-03329/15/2025
Advanced ferritic nitrocarburizing process combined with a specialized post-oxidation treatment described as FNC + Smart ONC® [1] is developed for brake rotor applications. The process can be applied to standard grey cast iron brake rotors, significantly reducing PM 10 emissions to levels below the Euro 7 limits for most vehicles equipped with at least some recuperative braking capabilities, all without compromising performance. Finished grey iron brake rotors, ferritic nitrocarburized and post oxidized were evaluated according to several industry standards. The standards include SAE J2707B (Block Wear Test including Highway) [2], GRPE-90-24 Rev.1 Emission Test (Full WLTP Brake Cycle 6 Times) [3], and SAE J2522 (AK-Master Performance) [4]. Nitrocarburized post oxidized brake rotors were compared to untreated grey iron rotors exposed to several friction materials. Ferritic nitrocarburizing and post oxidation addresses the issue of corrosion, which is particularly relevant for brake rotors that experience less use in vehicles with recuperative braking systems. Improved corrosion performance of ferritic nitrocarburizing and post oxidation could potentially eliminate the need for the conventional practice of painting rotors. Corrosion performance was validated by conducting cyclic corrosion according to SAE J2334 (Cyclic Corrosion, 36 cycles) [5]. A reduction in brake emissions by 50 percent was achieved for existing vehicles without recuperative braking systems.
Winter, Karl-Michael, Holly, Mike
SAE No. 2 Friction Test Machine 3600 rpm Stepped Power TestJ2487_202507 (Current)7/16/2025
This SAE Recommended Practice is intended as the definition of a standard test, but it may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 Friction Test Machine is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluids. It can also be used to conduct durability tests on wet friction systems. The specific purpose of this document is to define a 3600 rpm stepped power test for the evaluation of wet friction system performance variation as a function of power level. This procedure uses an initial engagement speed of 3600 rpm and is intended as a standard procedure for common use by both suppliers and end users. The only variables selected by the supplier or user of the friction system are: a Friction material b Fluid c Reaction plates These three variables must be clearly identified when reporting the results of using this test. If any of the test parameters or system hardware as described in this document are changed, other than the friction material, test fluid, or reaction plates, the data may not be reported as having been obtained using this document. This procedure is not intended to evaluate the initial coefficient or break-in characteristics. For this information, refer to SAE J2490.
Automatic Transmission and Transaxle Committee
Thermal Swell, Growth, and Hot Compressibility of Brake Friction Materials and Noise InsulatorsJ160_202505 (Current)5/27/2025
This document specifies a universal method of measuring the thickness change of friction materials to determine the effects of temperature. The test applies to both disc and drum-type linings commonly used in hydraulic and air brake systems for automotive or commercial vehicle applications. This document describes several methods for thermal swell and growth. Method A is where the friction material is in contact with a heated surface to simulate the heat input to the pad that occurs during actual usage. Method B uses an oven to heat the freestanding material and is an approximate procedure requiring less instrumentation. Method A is recommended for disc brake pad assemblies, noise insulators, or flat coupons, while Method B is recommended for curved drum brake linings. This document also describes how to test the warmed-up disc brake pads and noise insulators for hot compressibility using Method A.
Brake Linings Standards Committee
A Nonlinear Characteristics Identification and Compensation Control Method for Electromechanical Brake System2025-01-88104/1/2025
Clamping force control in Electromechanical Brake (EMB) systems must overcome various nonlinear characteristics, such as motor distorted voltage, Back Electromotive Force (EMF), and actuator friction disturbances. Therefore, modeling and parameter identification of these nonlinearities are necessary. This paper first proposes a motor parameter identification method based on the mathematical model of a Permanent Magnet Synchronous Motor (PMSM). A combination of the Least Square Method and Particle Swarm Optimization (PSO) is used to stepwise identify both the electrical and mechanical parameters of the motor. The accuracy of the identified parameters is validated by comparing simulation results with test bench responses. The identified parameters are applied to design the motor Back EMF compensation module, the distorted voltage compensation module, and to tune the current loop parameters. Next, a lumped parameter friction model suitable for closed-loop clamping force control in EMB systems was established, and specific operating conditions for identifying friction parameters were designed. The feasibility of this identification was validated through simulation analysis. Finally, a closed-loop clamping force control strategy based on friction compensation was developed. The proposed method is applied to the clamping force control system of a vehicle equipped with four-wheel EMB. Experimental results demonstrate that the stepwise parameters identification method for both motor and actuator effectively improves the response speed and accuracy of EMB clamping force control.
Qiao, Le, Xiong, Lu, Zhuo, Guirong, Shu, Qiang
Material-Combined Vehicle Brake Disc Design for Enhanced Cooling Performance2025-01-81894/1/2025
The improvement of heat dissipation performance of ventilated brake discs is vital to braking safety. Usually, the technical approaches shall be material optimization or structural improvement. In this paper, a simulation model of the heat transfer of brake discs is established using STAR-CCM+ software. Cast iron, aluminum metal matrix composite (Al-MMC), and carbon-ceramic composite materials (C-SiC) are compared. The results show that: Al-MMC has better thermal conductivity so that a more uniform temperature gradient distribution shall be formed; C-SiC has poorer heat capacity yet, according to previous studies, it has better thermal stability, which is the ability to ensure its friction factor under high-temperature condition; cast iron performs better with convective heat transfer rate, which enhances the heat transfer between the surface and surrounding flow field. Based on the results, this paper proposes four types of material combined brake discs using different friction materials and geometry structures. Al-MMC and C-SiC friction layers are compared at the level of material application. At the level of geometric structure, 3mm and 5mm are chosen to be the thickness, and the different simulations of simulation are discussed. For material selection, the material-combined discs have lower friction surface temperatures compared to the use of single materials, and the overall temperature gradient distribution is more uniform; for the selection of the friction layer thickness, the use of the 3mm composite friction layer scheme, regardless of the Al-MMC or C-SiC, has a lower friction surface temperature than the 5mm friction layer scheme. For different friction layer thicknesses, using a 3mm friction layer has a lower friction surface temperature than 5mm regardless of the materials, and the temperature distribution is more uniform. However, due to the increased cast iron content, the 3mm solution is less lightweight than the 5mm solution. Overall, the material combination approaches can offer a significant performance improvement over the single material discs, which contributes to the safety of automotive braking.
Wang, Jiarui, Jia, Qing, Zhao, Wentao, Xia, Chao, Yang, Zhigang
A Comparative Study on the Working Efficiency of Journal Bearing Employing Different Micro-Textures04-18-02-00112/19/2025
This study proposed the different micro-textures of the SC (square cylinder), SWS (square wedge shape), HS (hemispherical shape), and CR (cylindrical round) to improve the working efficiency of the journal bearing. A hydrodynamic lubrication model of the journal bearing under the impact of the changing dynamic loads is established to analyze the performance of micro-textures. The maximum oil film pressure and minimum frictional force in the journal bearing are selected as two evaluation indices. Some outstanding research results show that all the SC, SWS, HS, and CR added on the bearing surface improved the working efficiency of the journal bearing better than without the micro-textures. Moreover, the HS also improved the working efficiency of the journal bearing better than other structures of SC, SWS, and CR. To optimize the working efficiency of the journal bearing using HS, the dimension ltex and depth htex of HS should be selected and designed in a range of 3.6 < ltex ≤ 3.9 mm and 7.5 ≤ htex ≤ 10 μm, especially at ltex = 3.6 mm and htex = 10 μm. Research results not only provide a detailed assessment of the lubrication efficiency of different micro-textures but also find a new structure of HS with their optimal parameters to further improve the working efficiency of the journal bearings.
Song, Fengxiang, Nguyen, Vanliem, Liu, Yaxi
Road Vehicles - Friction Materials - Finished Brake Pad Normalized Elastic Constant of Friction MaterialJ3175_202412 (Current)12/6/2024
This SAE standard specifies a method for testing and measuring a normalized elastic constant of brake pad assemblies using ultrasound. This document applies to disc brake pad assemblies and its coupons or segments used in road vehicles.
Brake Linings Standards Committee
Objectively Quantify Creep Groan and Dynamic Grunt Performance of Different Brake Friction Materials2024-01-30359/8/2024
The assessment of brake friction materials extends beyond squeal noise and thermal roughness testing as it play crucial role in other brake noise phenomena such as creep groan and dynamic grunt. These low frequency noise types are significant as they directly affect passengers comfort levels. Creep groan noise defined as audible stick-slip noise at low vehicle speed during partial brake application, typically encountered in dense traffic conditions. Dynamic grunt is another form of stick-slip noise observed during high-speed braking and it is noticeable just prior to vehicle’s complete stop. This noise is indicative of frictional interaction between the brake pad and disc under deceleration scenario. Comparative analysis of two distinct brake friction materials was conducted utilizing both NVH dynamometer and real-world vehicle testing. The NVH dynamometer procedure was designed to evaluate the creep groan and dynamic grunt phenomena under controlled environmental conditions. For the creep groan assessment, a static motor varied speed between 0 and 2 kph under a constant brake pressure, whereas the dynamic grunt evaluation involved applying various braking speeds at different deceleration rates. Vehicle testing for dynamic grunt evaluated under varied temperature and humidity conditions, with the procedure repeated after 10,260 and 510 burnish stops to gauge materials performance consistency over time. Objective quantification of the dynamometer test data was achieved by analyzing peak-to-peak vibration amplitudes from accelerometer channel, vibration duration, brake torque variation, spectral density within the 0 to 1000 Hz range. In contrast, the vehicle tests relied on subjective evaluations from the drivers to gauge noise characteristics. The test results demonstrated the significant impact of the friction materials on both the dynamometer and vehicle testing outcomes. Material A exhibited superior performance, evidenced by notably lower peak-to-peak vibration amplitudes and spectral density values compared to Material B, implying the importance of material selection in mitigating undesirable brake noise phenomena.
Barot, Ankit, Wang, Weicherng
Niobium Alloyed Ferritic Nitrocarburized Brake Rotors2024-01-30319/8/2024
Niobium (Nb) alloyed Grey cast iron in combination with Ferritic Nitrocarburize (FNC) case hardening heat treatment is proposed to improve wear resistance and reduce brake dust generation of brake rotors. Standard Eutectic and Hypereutectic Grey irons alloyed with Niobium were evaluated in comparison to baseline unalloyed compositions. Brake speed snub sensitivity tribological testing was performed on a matrix including Niobium alloyed, Unalloyed, FNC, Non FNC, Non-Asbestos Organic (NAO) friction and Low metallic (Low Met) friction materials. Full size brake rotors were evaluated by Block Wear and Corrosion Cleanability. Improved wear, corrosion resistance and reduced brake dust debris were demonstrated by the Niobium alloyed FNC brake rotor combinations. Corrosion is an important consideration when evaluating brake performance. Combining cyclic corrosion and brake rotor testing provides the best comparison with field exposure.
Holly, Mike
Enhancing Brake Performance: FNC-Smart-ONC® Technology to Address Corrosion Challenges and Extend the Durability of GCI Rotors2024-01-30449/8/2024
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.
Nousir, Saadia, Winter, Karl-Michael
A Study on the Countermeasure to EURO7 Brake Dust Regulation Phase 12024-01-30499/8/2024
This is a case study to cope with the brake dust regulation of EURO7, countermeasures were listed, and evaluation and verification studies using C segment sports utility vehicle were conducted on them. Through this phase1 study, it was most reasonable to apply hard metal cladding disks and metallic friction material to front brake and apply friction materials as NAO with less dust generation to rear brake. This was because it is possible to satisfy new regulations without deteriorating the required performance in Europe. However, it is necessary to develop detailed specifications of discs and friction materials to satisfy our braking development goals for European models in the Phase 2.
Kim, Yoon Cheol, Kim, Jwa Kyum
Time for a Model Change - Inorganic Friction Materials2024-01-30429/8/2024
This paper’s aim is to explain alternative friction lining formulations based on inorganic polymer binders for the production of new, future-proof brake friction materials. The aspects of high-temperature stability in the fading tests of the AKM- and AMS tests, as well as the reduction in PM10 emissions compared to classic organic friction materials, make these materials particularly fascinating for future use. Additionally, the energy savings potential of this type of friction lining could be of particular importance when sustainability considerations further influence our development activities in friction brake related applications.
Milczarek, Roman Paul, Wittig, Niels
Microstructural Analysis and Tribological Performance of Composite Iron Sulfides in Automotive Brake Pads2024-36-03228/9/2024
This research explores the tribological characteristics of brake friction materials, focusing on synthetic iron-based sulfides with unique microstructures. Tribological testing, conducted per the SAE J2522 and SAE J2707 standards across diverse temperatures, reveals the superior performance of brake pads incorporating composite iron sulfide, especially at high temperatures. These pads exhibit stable friction levels and reduced wear compared to those utilizing pure iron sulfide, signifying a noteworthy advancement in overall tribological properties. A comprehensive cross-sectional analysis of friction materials using Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM/EDS) reveals chemical alterations. Pure iron sulfide undergoes extensive oxidation compared to composite iron sulfide, which exhibits oxidation near the friction surface due to differences in the oxidation mechanism because of the differential microstructure. Furthermore, Thermogravimetric Analysis (TGA) and X-ray Diffraction (XRD) techniques were employed to validate the observed differences. The research highlights the pivotal role of microstructure in influencing the kinetics of thermal oxidation. An alternative oxidation mechanism is postulated for composite iron sulfides, offering insights into disparities in oxidation processes compared to pure iron sulfides. A noteworthy aspect is the protective function of magnesium oxide in composite iron sulfide, acting as a shield against oxidation. These findings indicate significant performance enhancements for composite iron sulfide (FE50), particularly in high-temperature conditions, exhibiting consistent friction coefficients and reduced wear compared to pure iron sulfide (FE10).
Jara, Diego Chavez, Lorenzana, Carlos, Cotilli, Edoardo, Sliepcevich, Andrea, Conforti, Michael
Thermal coupled structural analysis of a brake disc2024-36-03058/9/2024
Designing a brake disc is a very challenging job. Besides to being a key item in vehicle safety, we are referring to a product that goes through several manufacturing processes and during its application it is exposed to extreme conditions of mechanical stress, temperature and vibration. The raw material for a large portion of commercial brake discs is normally gray cast iron with the possibility of adding alloy elements. This material is characterized by having high resistance to wear due to friction and having practically zero plasticity. As it is a material without a plastic working regime, it is very important to properly size the product for use, once the material’s resistance limit is reached, a catastrophic failure in operation may be inevitable. Quality control systems in casting and machining have great importance in the development of the disc, but physical tests are always essential in this type of product. Dynamometer tests are great options for validating brake discs, due to their ability to simulate practically all the severe conditions to which they will be exposed in real application. However, it is possible to predict possible disc failures even before subjecting them to the dynamometer, using numerical analyzes through the finite element method, a methodology that ensures that we are more assertive in the project, reducing time and money spent. In view of this challenging scenario, this work presents the results of a thermal analysis (CFD) of a brake disc, coupled with a structural analysis (FEA), with the objective of predicting a possible failure in the product and finally correlating the numerical results data with data from physical tests obtained on a dynamometer. At the end of this work, it was possible to determine the thermal distribution of the disc at the thermocouple installation point with an accuracy of 95% and find tensile stresses in the order of the yield stress of the disc material, thus predicting a probable breakage.
Deckmann, Jardel Luis, do Nascimento, Vagner
Development of Brake Shoe with Carbon Footprint Reduction2024-36-03118/9/2024
Considered one of the greenest forms of transport, the rail industry is at an exciting point pursuing several key initiatives to decarbonise its operations, assets, and supply chains. Therefore, having a brake shoe with a lower carbon footprint is essential for achieving the goals related to decarbonizing the operation, as it is a wear item. For this purpose, a carbon footprint measurement methodology was applied to the development of a friction material for railway brake shoes in order to reduce the carbon footprint generated in the production of the material, combining a sustainable material with greater durability in operation, thus reducing the total cost of ownership. In order to assess the advantages of the new product, a comparative analysis was carried out of the carbon footprint of the conventional shoe and the new railway shoe proposal, both used in the same application, considering the performance and environmental impact of each raw material and stage of the production process. This assessment was carried out by compiling and analyzing greenhouse gas emissions throughout the entire life cycle, from the extraction of raw materials, through all the links in its production chain to the gate, in accordance with ABNT ISO/TS 14067:2018. Performance was also assessed based on the AAR M-926 standard using a 1:1 scale inertial dynamometer capable of simulating the various operating conditions following the specifications of the Brazilian market. The comparative analysis showed that the new railway shoe is a more sustainable option, as it emits 43% less greenhouse gases than the conventional shoe (avoiding 4.7 kg of CO2e in the environment). The performance results also indicated a durability gain of 20% compared to conventional brake shoes.
Casagrande, R.B., De Souza, A.R.A., Finimundi, A.V., Pereira, C.H.S, Masotti, D., Rombaldi, R.J., Gotardo, T.
Proposed Test Method for Brake Pad Lining Robustness in Cold Conditions2024-01-50494/24/2024
With globalization, vehicles are sold across the world throughout different markets and their automotive brake systems must function across a range of environmental conditions. Currently, there is no current standardized test that analyzes brake pads’ robustness against severe cold and humid environmental conditions. The purpose of this proposed test method is to validate brake system performance under severe cold conditions, comparing the results with ambient conditions to evaluate varying lining materials’ functional robustness. The goal of this paper is to aid in setting a standardized process and procedure for the testing of automotive brakes’ environmental robustness. Seven candidate friction materials were selected for analysis. The friction materials are kept confidential. Design of experiment (DOE) techniques were used to create a full-factorial test plan that covered all combinations of parameters. The test script involves brake applications at 5, 10, 15, and 20 bar, at both ambient/non-humid and cold/humid conditions. Each brake application collects the stop time and coefficient of friction (COF) values throughout the stop. Failure modes are subjectively long braking times and failed brakes. The test results verify that brake pad effectiveness is dependent on friction lining, braking pressure, and environmental conditions. Other than at the lowest tested braking pressure, the COFs appear to be consistent across the tested braking pressures. Each material was evaluated for robustness against cold conditions by calculating their signal-to-noise (S/N) ratio, a common method used during design for six sigma (DFSS) robust optimization analysis. The braking time S/N is calculated using smaller the better (STB) analysis, whereas the COF S/N is calculated using the larger the better (LTB) analysis. Using the S/N ratio, it can easily be determined which brake pad friction lining material is the most robust against environmental conditions. Friction designation A was consistently calculated to be the most robust friction material against the cold environmental conditions. All friction linings had extended stopping times in cold conditions when compared to ambient conditions. In some cases, the lining materials reached critical failure in severe cold environments. Additionally, the collected friction values gave insight into potential extreme pad wear rates.
Passador, Stephen Daniel Austin, Boudreau, Douglas Barret, Capacchione, Christopher James
The Influence of Torsional Vibrations on the Longevity of Manual Transmission Synchronizers and the Durability of Clutch Dampers2024-01-50101/25/2024
This study delves into the impact of engine torsional vibration on transmission component failures, specifically synchronizers and clutch damper springs. Synchronizers are crucial in ensuring smooth gear shifts by synchronizing the rotational speeds of the transmission input and output shafts. While design factors such as geometry, friction material, and lubrication are often attributed to synchronizer failures, engine-generated torsional vibrations significantly affect their lifespan. Clutch damper mechanisms integrated into the clutch disc are designed to mitigate these vibrations. This research employs 1D powertrain simulation modeling to predict powertrain torsional vibration behavior. Additionally, rig tests are conducted to simulate vehicle-level angular accelerations and examine the impact of torsional vibrations on synchronizer life. The results provide valuable insights into optimizing clutch damper design to effectively dampen vibrations and prolong transmission component lifespan.
Jagtap, Amol, Rudramath, Sagar, Chollangi, Damodar, Bhandari, Kiran
Power Cylinder Effects on Friction and Fuel EconomyJ2904_202401 (Current)1/22/2024
This document covers the mechanisms from the power cylinder, which contribute to the mechanical friction of an internal combustion engine. It will not discuss in detail the influence of other engine components or engine driven accessories on friction.
Piston and Ring Standards Committee
Reliability Prediction and Demonstration for Wear Failure Mechanism2024-26-03231/16/2024
Wear phenomenon has extensively been published in the literature and this paper presents a methodology of how the wear models were used to assess the risk of failures in a field application, through endurance testing at a system level. Correlation of the wear prediction by the model with actual measurement was performed and used to predict the field operation reliability. Results are shown for sliding wear as well as impact wear phenomenon in this paper. In the case of sliding wear, wear modeling and prediction was done for a friction material using a system level metric, and the mean wear predicted was not different from the model predicted values at 95% confidence under a field application duty cycle.
SR, Ranjith Kumar, Soma, Nagaraju
Brake Pad Life Monitoring System Using Machine Learning2024-26-00321/16/2024
In the context of vehicular safety and performance, brake pads represent a critical component, ensuring controlled driving and accident prevention. These pads consist of friction materials that naturally degrade with usage, potentially leading to safety issues like delayed braking response and NVH disturbances. Unfortunately, assessing brake pad wear remains challenging for vehicle owners, as these components are typically inaccessible from the outside. Moreover, Indian OEMs have not yet integrated brake pad life estimation features. This research introduces a hybrid machine learning approach for predicting brake pad remaining useful life, comprising three modules: a weight module, utilizing mathematical formulations based on longitudinal vehicle dynamics to estimate vehicle weight necessary for calculating braking kinetic energy dissipation; and temperature and wear modules, employing deep neural networks for predictive modeling. Notably, the model’s training leverages rig-level data, with limited vehicle-level data for validation, achieving a validation accuracy of 94.8%. This innovative indirect approach holds the potential to be deployed universally in vehicles, enhancing safety without imposing additional burdens on customers or the environment.
Iqbal, Shoaib, Bhambri, Mihir, lahase, Rahul
Inertia Dynamometer Disc and Drum Brake Effectiveness Test ProcedureJ2522_202312 (Current)12/13/2023
This SAE Recommended Practice establishes a standard method to perform screening test sequences that identify a brake friction material’s effectiveness under various test conditions. The result is an evaluation of brake friction material effectiveness under a set of defined braking conditions considered most relevant to automobile braking system development.
Brake Dynamometer Standards Committee
Low-Speed Continuous Slip SAE No. 2 μPVT ProcedureJ2964_202311 (Current)11/15/2023
This SAE Recommended Practice is intended as the definition of a standard test, which may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 friction test is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluid combinations. The specific purpose of this document is to define a µPVT test for the evaluation of the variation of wet friction system low speed slip characteristics as a function of speed, temperature, and pressure. This procedure is intended as a suggested method for both suppliers and end users. The only variables selected by the supplier or user of the friction system are: Friction material Fluid Reaction plates Oil flow (optional) These four variables must be clearly identified when reporting the results of this test. If any of the test parameters or system hardware as described in this document are changed—other than the friction material, test fluid, or reaction plates—the data may not be reported as being obtained using this document. This procedure is intended to evaluate ramped speed friction characteristics, also called sweeps, and can be used to demonstrate capacity changes that occur between the different levels of slip speed, applied pressure, and fluid temperature. The level of coefficient of friction, as well as the trends in torque capacity with speed, can be used to compare candidate materials or fluids.
Automatic Transmission and Transaxle Committee
Effect of Soft Reinforcement Particles on Microstructural, Mechanical, and Tribological Properties of Sintered Copper-Based Brake Composite Friction Material2023-28-013211/10/2023
The main objective of the work is to investigate the friction and wear behavior of sintered copper-based brake composite friction material with a change in the volume percentage of soft reinforcement particles namely MoS2 by pin-on-disc tribometer for medium-duty automotive applications. The composite brake friction material contains copper (Cu) as a matrix, tin (Sn) as an additive, silicon carbide (SiC) and molybdenum disulfide (MoS2) as hard and soft reinforcement particles and barium sulfate (BaSO4) as filler. These hybrids copper-based brake composite friction (pin) samples are successfully prepared by a change in compositions of MoS2 from 0 to 5 vol. % in the step of 1 vol. % and the characterizations of friction samples are studied to understand the physical and mechanical properties such as density, hardness, and compressive strength. Finally, the dry sliding friction and wear test is conducted against grey cast iron material (disc) at constant load and sliding speed of 50 N and 5 m/s respectively using pin-on-disc equipment under room atmosphere. Based on the analysis of the result, the developed copper-based brake composite friction sample with 2 vol. % of MoS2 has shown better mechanical and tribological properties among other compositions. Further, post-test analysis on the worn-out sample surfaces using a field emission scanning electron microscope (FESEM) with energy dispersive spectroscopy (EDS) revealed that change in wear mechanisms from abrasion to adhesion as an increase in the volume percentage of MoS2.
P, Raja, Ramkumar, Penchaliah
Development of Asbestos Free Aramid Fibre based Friction lining Material for Automotive Application2023-28-012211/10/2023
The usage of asbestos-free material has grown in the automotive, aviation, and marine sectors due to its carcinogenic nature. The present investigation is to evaluate the non-asbestos organic friction material for automotive applications using aramid fibers. The aramid fibers or pulp is one of the essential ingredients of friction material as it possesses good qualities of friction material like high wear resistance and reliability. The present work is to optimize the pulp required for the best performance of friction lining material for brake pads in the automotive industry. The pulp percentage is varied by 0, 5, 7.5, and 10 weight percentages in hybrid composite friction materials. The various mechanical, wear and microstructural analysis are studied. The experimental result revealed that friction material having 10 wt% of aramid fiber (AF) proved the best performance with superior mechanical and wear characteristics.
J, Chandradass, T, Thirugnanasambandham, M, Amutha Surabi, P, Baskara Sethupathi, Rajendran, R
Reproducibility of Physico-Chemical Properties in Brakes Emissions Generated at Different Dynamometric Benches2023-01-187711/5/2023
In recent years, brakes emission tests have become increasingly standardized to meet progressively stricter intra and inter laboratory reproducibility requirements. In particular, following the recent EURO 7 regulation proposal, WLTP-Brake cycle has surged as EU standard braking sequence to determine emission factors of investigated brake systems. Furthermore, the UN GTR (United Nations Global Technical Regulation) on Laboratory Measurement of Brake Emissions for Light-Duty Vehicles collects all the information needed to perform emission tests in laboratory. This includes design specifications for the testing platforms as well as the typology and configuration of measuring instruments. Notably, laboratory emission tests are also increasingly used to collect particulates for chemical characterization, since the compositional information is crucial to: i) provide correct assessment of their toxicological and environmental behavior; and ii) better understand tribological and emission mechanisms. Therefore, this work specifically aims at investigating the topic of the inter laboratory reproducibility of physico-chemical properties in particulates generated by the same friction couple when collected during emission tests carried out on different testing platforms. In particular, the contribution focuses on the comparison of PM10 emissions generated by three different friction couples (i.e., ECE R90 Low Steel, NAO and Inorganic-bound friction materials coupled against grey cast iron brake discs) during sets of WLTP tests performed at two different facilities. More in detail, a wide physico-chemical characterization performed by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDXS) and X-Ray Diffraction (XRD) analysis is used to unveil the inter laboratory reproducibility of both the particle size distribution and the chemical composition of corresponding twin particulates collected at the two testing laboratories. The reported results will provide useful insights regarding the variability level to be currently expected in selected physico-chemical properties of non-exhaust emissions from brakes when collected in different testing facilities.
Mancini, Alessandro, Tsyupa, Bozhena, Della Bella, Pietro, Russo, Simone, Martinelli, Elia, Leonardi, Mara, Belotti, Stefano, Hense, Maximilian, Niemann, Hartmut, Bertasi, Federico, Bonfanti, Andrea
Experimental Investigation of Tribochemical Processes in Frictional Contacts Using a Pin-on-Disk Tribometer2023-01-188911/5/2023
Friction in tribological systems can lead to significant energy consumption and wear. While there are several dissipation mechanisms in the frictional boundary layer, the role of chemical processes is not fully understood. The aim of this study is to investigate the influence of chemical reactions on the tribological behavior of sliding friction pairs. In order to carry out initial analyses, minimal mixtures with a few simple components and epoxy resin as a binder are developed, produced and used. A series of experiments are performed on a pin-on-disc tribometer with different minimal mixtures. Temperature and friction coefficient are measured throughout the friction process, and the rubbed surface of the samples is measured in situ. Three types of chemically inert minimal mixtures are developed in the first phase of the experiment. In the second phase of the experiment, copper powder is added to all minimal mixtures to study the influence of copper oxidation as the main chemical reaction. The tribometer measurement results show that the addition of copper has little effect on fine alumina samples and increases the friction coefficient and average wear volume of coarse alumina samples. In particular, the greater the amount of copper added to the mixtures, the greater the effect of copper and the more unstable the friction behavior of the coarse alumina samples. Following the tribometer measurements, the samples are also analyzed using energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) to investigate the changes in the mixtures after the addition of copper. Initial chemical analysis results show that the coarse alumina samples with a certain amount of copper in them have more plateau-like patches formed in the boundary layer. These patches are mainly caused by the oxidation of iron coming from the disk during the measurement. Our results contribute to a better methodology for the study of tribochemical processes with predefined minimum mixtures in frictional contacts and to a better understanding of the role of tribochemical processes in the boundary layer dynamics, and can aid in the development of simulation tools.
Fang, Chengyuan, Ostermeyer, Georg-Peter, Schiefer, Frank, Schilde, Carsten, Lehmann, Christina, Bräuer, Günter
Engineering Properties of Drum Brake Friction Materials2023-01-189011/5/2023
The rising popularity of EVs has led to a resurgence of interest in drum brakes. Drum brakes benefit from less complex mechanical design, have no residual brake drag, and the enclosed design is less susceptible to corrosion and debris emission. For the commercial EVs, the elimination of engine noise makes brake noise a major contributor to vehicle noise. With the renewed interest in drum brakes, there is an increased need for property data for NVH simulations to optimize noise performance. Similar to disc brakes, the modeling of drum brake performance requires a complete set of friction material engineering properties determined over the pre-loads and temperatures encountered in brake applications. Results are presented for eight different drum brake formulations and platforms. The measurement approach and data analysis parallels that used for the elastic property measurements of disc pad friction materials, SAE J2725. A complete set of elastic properties and engineer properties are measured on several formulations over the temperature range from 20°C to 325°C and pre-loads from 5 bar to 30 bar. These drum brake friction material elastic properties are compared with those typically encountered in disc pads. The sample preparation techniques, data collection methods, and analysis procedures used to mitigate the influence of drum brake curvature will be described.
Yuhas, Donald, Vorres, Carol, Oleksak, Loretta, Divakaruni, Saikiran, Subramanian, Vijay
Effect of Moisture Adsorption on Low-Speed and Moderate-Speed Braking: Effect on In-Stop Friction Coefficient and Low Frequency Noise2023-01-186211/5/2023
Copper-free NAO disc pads of passenger cars were investigated for a combination of prior braking conditions and moisture adsorption influencing in-stop friction and noise during low-speed stops, and in-stop-friction during moderate-speed stops. Prior braking conditions and moisture adsorption strongly influence subsequent in-stop friction behavior and noise at room temperature. The low-speed in-stop friction behavior looks totally different from that of moderate-speed stops. The low-speed in-stop friction increasingly oscillates with increasing moisture adsorption and goes down towards the end of a stop, which is accompanied by increasing low-frequency noise. The moisture content needs to be quantified/specified to obtain repeatable/reproducible brake test results as the moisture is an unintended and uncontrolled ingredient of a friction material. As the disc surface roughness increases due to prior braking conditions, the friction coefficient of low-speed stops is found to decrease. The changing friction coefficient is explained by the nature of the friction film and its interactions with moisture.
Sriwiboon, Meechai, Koetniyom, Saiprasit, Rhee, Seong Kwan, Sukultanasorn, Jittrathep, Kaewlob, Kritsana, Kunthong, Jitpanu
Sound Source Identification of In-Plane Squeal of Disc Brakes Using Array Microphones and Its Verification by Acoustic Simulation2023-01-186911/5/2023
As the vehicle electrification progresses and the demand for acoustic comfort increases, the NVH performance of brakes becomes more important theme. In-plane squeal of disc brake is one of phenomena that is difficult to countermeasure. In this study, we used array microphones to search for sound sources of in-plane squeal in order to elucidate the mechanism. The Microphones were set in the out-of-plane direction and the lateral direction of a disc in brake components on a full-sized dynamometer. In the vibration mode in which in-plane stretch vibration was dominant, the sparse and dense parts showed high sound pressure. 3D laser vibrometer was used to check displacements of the disc, and the result indicated a possibility that the sparse and dense parts could vibrate in the out-of-plane direction and generate the sound. Then, complex eigenvalue analysis (CEA) and acoustic simulation were conducted to validate the experimental results. Firstly, frequency of instability mode occurred in CEA was almost the same as that of the actual brake squeal and the mode was identified as in-plane squeal mode. Secondary, acoustic simulation resulted that areas near the sparse and dense parts in a disc had high sound pressure as similar to the sound source identified by array microphones. Finally, parametric studies of friction material property showed correlation between the CEA results and the sound pressure distribution obtained by acoustic simulation.
Tanamachi, Shuhei, Millsap, Tom, Yamaguchi, Yoshiyuki
Brake Pad Moisture Adsorption and Its Effect on Brake Pad Compression Strain/Modulus and Friction Coefficient: Effect of Pad Cure Temperatures2023-01-186311/5/2023
The moisture adsorption kinetics of copper-free brake pads was studied to confirm an earlier finding that the adsorption weight gain follows a logarithmic relationship with respect to the square root of humidity exposure time and the relationship is linear in the beginning. When the pad cure temperature was raised from 120 to 180 and 240 °C, the adsorption rate increased. The 180 °C cure produced the highest pad modulus. With increasing moisture adsorption, the pad compression modulus increased just like the pad dynamic modulus, meaning decreasing compression/compressibility while the ISO ‘compressibility’ determined after 3 compressions under 160 bars increased in contradiction. It is concluded that the ISO ‘compressibility’ is a destructive hardness measurement like the Gogan or Rockwell hardness: the key difference is the indenter covers the entire surface of the pad. The true compressibility must be determined as an inverse function of bulk modulus. It is recommended that the pad compression modulus should be measured under low pressures like 10 bars for the purpose of determining the initial quality of virgin pads if the current ‘compressibility’ machines are to be used. Compression tangent modulus and dynamic modulus measurements produce the same results, meaning that one could replace the other. Pad cure temperature affects friction coefficient and moisture adsorption influences friction coefficient in opposite direction for moderate-speed snubs of 80 km/h vs. low-speed stops of 5 km/h.
Rhee, Seong Kwan, Rathee, Aman, Singh, Shiv Raj, Kumar Sharma, Devendra
Dynamometric Investigation on Airborne Particulate Matter from Brake of Automobile: Impact of Disc Materials on Brake Emission Factor2023-01-186111/5/2023
Non-exhaust airborne particulate matter (PM) from automobiles might lead to potential adverse effects on the respiratory system. In this work, we evaluated the impact of surface properties of disc rotors on brake wear PM emission for passenger vehicles. Dynamometric measurements using the novel cycle were made for gray cast iron (GCI), nitrocarburized (NC), and superhard ceramic coated (SCC) disc rotors using non-steel (N/S) friction materials. The brake emission factors (BEF) for the GCI and NC disc rotors ranged from 1.76 to 1.74 mg/km/vehicle, whereas that of the SCC rotor exhibited a much-reduced value of 0.50 mg/km/vehicle. As the hardness of the SCC rotor increases (> 1150 HV), lower BEF was obtained, whereas the coefficient of friction (COF) of the SCC disc was more than 20 % higher than the NC rotor. Temperature-dependent data indicated that disc temperature (Tdisc) for the SCC disc (~115 °C) was lower than that for the GCI and NC (Tdisc >130 °C).
Jeong lng, Mu Hyeok, Lee, Jungju, Choi, SungWoo, Sung, Sanghun, Kim, Jong-Young, Oh, Yoonsuk, Pee, Jae-Hwan
Desorption of Brake Friction MaterialsJ3281_202305 (Current)5/10/2023
This SAE Recommended Practice specifies a method to reduce and stabilize the moisture of products containing brake friction material (disc brake pads, drum brake shoes, friction blocks) so the parts are conditioned and maintained in a stable low moisture state.
Brake Linings Standards Committee
Root Cause Analysis of Limited Slip Differential Noise Vibration Harshness2023-01-11385/8/2023
The primary objective of this research was to identify the root cause of limited slip differential (LSD) NVH. The study examined the significance of different oils and additives that make up the lubrication mix in the axle. The impacts of gear marking compound type, friction modifier type, gear marking compound level, friction modifier level, reaction plate surface finish roughness, and friction material type were studied using Taguchi's Design of Experiment. Eaton's Vertical Friction Tester (VFT), a sub-system level test stand, was used to measure the performance characteristics of the clutch pack and oil mix. Sequential approximation and cumulative analysis methodologies were used to analyze test data where NVH was beyond the measurement capacity of the test stand. The DOE analysis showed that the type of gear marking compound used to set the ring gear mesh during axle build had the most significant influence on NVH levels.
Sarkar, Subrata, Samuelson, Eric, Allen, Jordan, Spiekermann, Ryan
Road Vehicles - Friction Materials - Elastic Properties MeasurementsJ2725_202304 (Current)4/21/2023
This SAE Standard specifies a method for testing and measuring elastic constants in friction materials by precise ultrasonic velocity measurements. Measurement methods are also described for measurement of the out-of-plane modulus as a function of pre-load as well as the measurement of engineering constants as a function of temperature. Finally, methods are formulated to produce all engineering constants as a function of pre-load and temperature.
Brake Linings Standards Committee
Correlated Simulation of Pseudo Transient Torque Converter Clutch Engagement Using Coupled Fluid Structure Interaction2023-01-04574/11/2023
This investigation utilizes a correlated fluid-structure interaction (FSI) model of the torque converter and clutch assembly to perform a pseudo transient clutch engagement at steady state operating conditions. The pseudo transient condition consists of a series of nine steady state simulations that transition the torque converter clutch from fully released to near full lockup at a constant input torque and output speed representative of a highway cruising speed. The flow and pressured field of the torque converter torus and clutch are solved using a CFD model and then passed along to a transient structural model to determine the torque capacity of the lockup clutch. Bulk property assumptions regarding the friction material, deformation of the clutch plate, and deflection of supporting structures were made to simplify the model setup, run time, and solution convergence. Telemetry pressure measurements acquired in an operating torque converter under similar operating conditions on a transmission dynamometer test stand are provided to demonstrate FSI model correlation and behavior. A total of nine steady-state speed ratio simulations were run, from fully released to nearly fully locked torque converter clutch with less than 5% error in predicted pressure values compared with measured telemetry data. Visualization of the transmission fluid behavior within the torque converter pressure vessel during the engagement of the clutch from released to less than 10 rpm slip condition are provided. The overall objective of the investigation was to seek out and identify any potential fluid phenomena that contribute to undesirable control of the lockup clutch at low slip speed ratios.
Beldar, Aniket, Robinette, Darrell, Blough, Jason
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