Browse Topic: Brake pads

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Characterisation of Brake Wear PM2.5 and PN10 Emissions Across Pad/Disc Technologies, Light-Duty Vehicle Types, and Braking Behaviours Under Real World Conditions2026-24-00229/21/2026
Targeted brake emissions investigations undertaken within the Department for Transport’s Non-Exhaust Emissions programme are described in this paper. The non-exhaust emissions study aimed to improve understanding of particulate mass and particle number emissions from friction braking, and to quantify the influence of component selection, vehicle technology, operating conditions, and emissions control measures. A brake enclosure and sampling methodology, developed in an earlier project phase, was refined to improve airflow control, reduce leakage, and minimise artefacts. The updated system incorporated MPEC (hot and cold), APC10, DMS500, and eFilter instruments, enabling simultaneous measurement of volatile and non-volatile PN10, plus PM2.5. Nine brake pad formulations and two disc types were evaluated using a common C-segment platform during chassis dynamometer and on-road drive cycles, and under specific controlled braking events. Speed, deceleration and temperature effects on PM2.5 and PN10 emissions were investigated. The common platform testing included ICE, PHEV, and EV variants to capture test mass and regenerative braking influences, together with assessments of aged components. Results showed clear, repeatable differences between pad formulations, with low dust/ceramic pads yielding the lowest PM2.5 and PN10 emissions. Disc type effects were minimal, while component ageing/conditioning reduced emissions and improved repeatability. Brake temperature and energy input dominated emissions behaviour: dynamic braking produced the highest emissions, these increasing with road speed and disc temperature. Regenerative braking reduced EV and PHEV PM2.5 versus ICE, but PN10 remained comparable due to the dominance of non-volatile PN emissions during friction braking events. Increased vehicle mass led to proportionally higher emissions.
Andersson, Jon
Further Investigation of Brake Squeal: Effect of (Inboard/Outboard) Pads Property Differential2026-01-07999/14/2026
It was reported earlier that the wear differential between the inboard pad and the outboard pad leads to brake squeal generation. The (inboard/outboard) pads wear differential can occur due to hardware issues such as brake pad drag and/or two different wear rates of the (I/O) pads, which is caused by two different material properties of the pads although the pad formula may be the same. It is found that (I/O) pads compressibility differential/hardness differential/friction differential are all interrelated and that they contribute to brake squeal generation in addition to the inboard pad tangential/radial taper wear. A method has been found to separate the inboard pad friction and the outboard pad friction and to estimate each friction coefficient.
Liu, Richard, Wu, Shane, Wu, Godot, Zou, Tianlang
Advanced Brake Force Distribution and Pad Wear Life Integration in Supervisory Electronic Brake Control System for Combination Vehicles2026-01-07979/14/2026
Commercial vehicle fleets frequently operate with tractors that connect to different trailers and dollies, resulting in combinations with varying brake pad wear across wheel ends. Traditional brake-force distribution strategies do not consider these pad-life differences, which can lead to uneven brake utilization, irregular maintenance intervals, and increased total cost of ownership (TCO) in mixed-trailer operations [7, 9]. While modern electronically controlled braking systems (EBS) already incorporate pad wear based braking for the tractor itself [5], these capabilities do not extend across the entire vehicle combination because trailer-side communication is typically limited to standardized CAN protocols such as ISO 11992 and J1939 [1, 2, 3]. As braking systems become more software defined and rely heavily on distributed electronic communication, ensuring the authenticity and integrity of trailer originated brake information becomes essential for both functional safety and cybersecurity [6]. In the proposed architecture, trailers and dollies communicate brake related data to the tractor over the ISO 11992 Tractor-Trailer CAN (TT-CAN) network [1, 2], allowing the tractor Brake Control ECU to securely validate the source of the information and register each towed unit for health aware braking. Once authenticated pad life data is available, the tractor constructs a combination level brake health map covering every wheel end in the configuration. During normal braking, a supervisory allocator computes wheel end specific brake pressure targets that bias braking toward wheel ends with greater remaining pad life while ensuring full compliance with stopping distance regulations and stability requirements [4, 7]. By integrating authenticated pad wear information with tractor hosted supervisory control, the system improves braking consistency across mixed combinations, harmonizes pad utilization, enhances maintenance predictability, and reduces TCO while meeting the safety and cybersecurity expectations of modern commercial vehicle fleets.
Ganesha, Vinodkumar
Aerodynamic Disc Brake Drag: An Elusive Source of Variability2026-01-08029/14/2026
The ever-present drive to increase vehicle range and efficiency has resulted in disc brake caliper requirements at or near zero residual drag. It is increasingly critical to understand and design around potential edge cases that can drastically increase off-brake drag. One frequently observed, but often misunderstood, phenomenon is drag induced by aerodynamic forces surrounding the brake pad. Complex airflow characteristics surrounding the pad in the brake corner environment can lead to Venturi Effect induced air pressure differentials on each side of the pad, leading to transient, yet pronounced, increases in brake drag. This paper will follow a case study during which brake pad pressure differentials were discovered and objectively measured, review the Venturi Effect as it relates to brake corners, and explore modelling approaches for identifying and correcting designs that are prone to this phenomenon.
Robere, Matthew, Tresmondi, Thales
Finite Element-Based Wear Analysis of Brake Pads2026-01-08179/14/2026
Brake pad wear progressively changes the pad–disc contact interface and can influence braking performance, wear uniformity, and component durability. This study presents a finite element-based procedure for predicting brake pad wear under braking conditions using generalized Archard’s wear law as the base framework. The method combines contact-pressure and slip-distance calculations with iterative geometry updating in Abaqus using the UMESHMOTION and USDFLD subroutines so that accumulated wear and evolving contact conditions can be continuously reflected during the analysis. To improve robustness in repeated-cycle wear simulation, a wear-direction algorithm, an extrapolation factor, and a contact stiffness scale factor are incorporated to reduce element distortion, enhance numerical stability, and control computational cost. Because temperature-dependent friction behavior, contact conditions, and material-property variations are strongly coupled in actual braking, their combined influence is represented through an effective wear coefficient calibrated from physical data using regression analysis, instead of independently modeling them. The proposed procedure was applied to burnish and subsequent evaluation modes, and the predicted wear results were compared with test measurements. Among the regression models considered, the log-linear model provided the best overall agreement with the experimental wear data. The results show that the proposed framework can reproduce both mean wear and location-dependent wear trends with good agreement over the evaluated operating range. The proposed procedure offers a practical numerical workflow for predicting brake pad wear under temperature-dependent operating conditions while maintaining acceptable numerical stability and computational cost.
Song, Seong Il, Joo, Sang Don, Kim, Min Sock, Kerszberg, Nicolas, Lee, Heewook
Comparison of the Surfaces and Coefficients of Friction of Truck Brake Pads Tested on a Flywheel Test Bench and a Scaled Tester – A Case Study2026-01-08269/14/2026
Mechanical brakes have been used and studied in many areas of mechanical engineering and automotive technology for decades. However, the processes in the contact zone have not yet been described with sufficient accuracy. One reason for this is the inability to observe the contact zone during contact. Studies show that replacing a friction partner with a visually transparent material affects the processes in the contact area. Researchers are therefore forced to examine the surfaces of the contact partners after the actual contact has taken place. Various measuring systems, such as microscopes or laser sensors for surface structure measurement, are used to measure the surfaces of the brake pads. Due to shorter measuring times, mainly only smaller samples from measurements using pin-on-disc tribometers are examined for this purpose. However, various studies show that the friction and wear values of pin-on-disc tribometers cannot be transferred to real brake systems. For this reason, surface measurements are performed on full-size truck brake pads in this publication. For this purpose, the SN6 truck brake from Knorr and the corresponding brake pads were subjected to defined load scenarios. The load scenarios comprise four different surface pressures of 0.8, 1.7, 2.5, and 3.3 MPa, as well as three different starting speeds of 10, 20, and 40 km/h. The rotational masses used in the flywheel test bench correspond to an equivalent translational mass of approximately 9 t. For each combination, 450 braking test cycles were performed. Following each measurement cycle, the surfaces of the brake pads are photographed and measured using a laser triangulation sensor. In addition, the contact surface between the brake pads and brake disc is examined using pressure measurement film. In addition to a qualitative and quantitative evaluation of the surfaces of the truck brake pad from the truck brake, a comparison is made with a partial lining sample of the same truck brake pad, which has been tested on a partial lining test bench under comparable test scenarios.
Rosenthal, Tobias Richard, Wiest, Daniel Christian, Meyer, Henning Jürgen
Predicting Wear of NAO Brake Pad Using Scaled-Down FMVSS 135 Testing and Machine Learning2026-01-08089/14/2026
Brake pad wear is a major and growing source of non-exhaust particulate emissions, projected to reach 1.3 million tons annually by 2030 and contributing up to roughly 55% by mass of non-exhaust traffic-related PM10 in urban environments, underscoring the need for improved durability and material optimization. This study investigates a three-stage eXtreme Gradient Boosting (XGBoost) ensemble paired with a residual Fully Connected Neural Network (FCNN) corrector to predict brake pad wear rate and support formulation optimization. Experiments used a simplified FMVSS 135 protocol on a Universal Mechanical Tester (UMT) simulating realistic braking across eight friction regimes. Wear rate was the sole machine-learning prediction target, while coefficient of friction (CoF) was retained as an input feature rather than a target. Despite a limited but high-quality 280-cycle dataset, regime-aware stratified splitting, sample reweighting, and hyperparameter optimization enabled robust generalization. The three-stage XGBoost ensemble with residual FCNN correction achieved a global held-out test R2 of 0.976 for wear rate prediction. A Taguchi L8 design of experiments defined the brake pad compositions, reducing experimental time and material consumption compared to conventional approaches. The framework demonstrated strong agreement between measurements and predictions for the dominant low-severity regime, while per-regime analysis identified the high-severity minority regimes as the priority for additional data collection, since within-regime R2 remains negative for every regime given current sample sizes. A sequence-aware mean absolute scaled error (MASE) analysis further shows that, despite the high global R2, none of the four pipeline stages currently outperforms a naive one-cycle persistence forecast on absolute error, a distinction reported here for transparency. The scalable architecture enables straightforward integration of additional material and process parameters, supporting iterative brake formulation development in industrial settings and, by reducing empirical testing requirements, sustainable brake material development with reduced replacement frequency and associated emissions.
Katakam, Abhishek, Eslamiat, Hossein, Kancharla, Sai Krishna, Filip, Peter
Real-Time Estimation of Brake Temperature using Physics-Informed Machine Learning Model2026-01-08109/14/2026
The current work presents a novel approach to estimating brake surface temperature in real-time to aid in brake wear prognostics. Brake prognostics involve estimating brake pad wear in real-time, which enables its predictive maintenance. Brakes are a safety-critical system for vehicles; therefore, they require accurate and robust pad wear estimation to ensure vehicle safety. However, it involves several challenges. The estimation of pad wear is fundamentally a two-stage process: the first stage involves the accurate prediction of brake pad surface temperature, while the second stage utilizes this thermal history to calculate cumulative material wear. A significant challenge in estimating brake pad wear without an expensive sensor is that it is sensitive to the surface temperature prediction; any error in the thermal model propagates and compounds in the wear prediction stage. To identify surface temperature, traditional physical sensors are often cost-prohibitive or prone to failure in the harsh thermal and mechanical environments of the wheel end, necessitating a robust virtual sensing solution that can capture complex, non-linear heat transfer dynamics. The current work addresses the above challenge of identifying temperature dynamics using a Physics-informed Machine Learning approach. We employ Symbolic Regression (SR), a data-driven method that discovers the underlying mathematical expression of the system dynamics by searching for the optimal functional relationship between variables. SR provides an interpretable model that can be generalized across automotive platforms, offering a transparent, computationally efficient, and analytically tractable alternative to traditional ‘black box’ models. To generate the temperature dataset, a test vehicles were equipped with thermal sensors and underwent various braking scenarios. The SR-based virtual sensing model demonstrated strong and consistent predictive fidelity across all braking conditions tested. Under mild braking scenarios, the model achieved a Mean Absolute Percentage Error (MAPE) of approximately 6.0% in predicting brake surface temperature. This performance remained highly robust under mixed and harsh, high-speed braking, the most thermally demanding scenario, yielding MAPEs of only 11.6% and 11.9%, respectively.. Across all regimes, this level of temperature estimation fidelity directly limits error propagation into the downstream brake pad wear prediction stage, enabling reliable, sensor-less, cloud-based brake health monitoring at scale.
Gannavarapu, Shivadath, Pal, Anuj, Fan, Mengdi
Study on Nonlinear Dynamic Characteristics of High-Speed Train Braking Systems2026-99-11419/11/2026
To address the oversimplification in prior brake system models, this study develops a 10-degree-of-freedom (DOF) dynamic model of a disc brake system. A control-variable approach is employed to numerically simulate the effects of braking force, rotational inertia, brake pad tangential stiffness, suspension stiffness, and damping. The vibration responses under different braking conditions and in the presence of multi-parameter coupling are analyzed through bifurcation diagrams, phase trajectories, and Poincaré sections. The main findings indicate: (1) Increasing braking force induces a transition from period-1 to higher-order periodic motions (e.g., period-6), accompanied by significant vibration amplification; (2) Enhanced brake pad tangential stiffness suppresses vibration amplitude but extends the sticking phase duration; (3) Exceeding a critical primary suspension stiffness threshold triggers system instability. These results suggest that structural optimization of suspensions and reasonable selection of brake pad support stiffness are important measures to prevent stick-slip vibrations.
Li, Songge, Wang, Jingyue
Feasibility of CFD-thermal-structural simulation based on real braking tests2026-36-03317/30/2026
During the development of mechanical components, engineers use numerical tools as a first step to design, develop, and analyze potential solutions for specific requirements, thereby reducing time- to-market of new components. Furthermore, numerical tools are also highly useful for analyzing components that exhibit failures. For brake discs, numerical analysis must consider not only mechanical behavior but also thermal and fluid dynamic behavior. In this context, as a further step, experimental tests can be performed in test facilities such as dynamometers, where the brake discs are evaluated under different operating conditions to determine their susceptibility to failures such as thermal distortion, judder (hot or cold), squeal, coning, etc. If such failures occur, corrective actions can be implemented using different approaches: a) redesign of the disc and braking system aided by numerical tools; b) tuning of the matching between disc and pad materials; and c) modification of the disc and/or the pad material. Regarding the first approach, the finite element method (FEM) is one of the most important numerical tools, and to obtain reliable results, accurate boundary conditions must be applied. The aim of the study is to demonstrate the feasibility of the CFD-thermal-structural boundary conditions derived from an experimental test performed on a ventilated brake disc assembled in an instrumented vehicle. Firstly, a comparison between an analytical method and the CFD solution was made regarding convective heat transfer coefficient (HTC). The test consisted of 16 main braking cycles from 140 to 0 km/h, conducted under eight different pedal pressure levels. After each main braking, a thermal shock was applied to the disc using water, followed by a secondary braking from 80 to 0 km/h, always with the same pedal pressure. The numerical analysis results showed good agreement with experimental tests in terms of temperature distribution. In addition, axial displacement distribution along the circumference is presented, with emphasis on coning deformation, one of the main triggers for judder.
Bagatini, Pablo Schettert, Viotti, Matias Roberto, Pereira, Leonardo, Tuzzin, Matheus, Titton, Angelo Pradella, Boaretto, Joel, De Leon, Daniel Milbrath
Innovative Friction Modifier for Copper-Free Brake Pad Applications2026-36-03137/30/2026
The development of copper-free brake pads poses a significant challenge because copper plays a critical role in tribofilm formation and friction stability. This study proposes a novel approach using a recycled flake iron oxide material, characterized by high thermal stability and a unique plate-like morphology, as a sustainable alternative. The material acts as a friction modifier, promoting the formation of stable tribofilms and serving either as a copper substitute or a functional additive. Its iron-oxide composition ensures strong compatibility with the counterface tribofilm, enhancing adhesive friction, while its role as a primary plateau contributes to friction stability and reduced wear. Three application scenarios were investigated: (i) copper substitution in Low-Steel (LS) and Non-Asbestos Organic (NAO) formulations, (ii) partial replacement of steel fibers in copper-free LS formulations, and (iii) synergistic use with iron sulfide in copper-free NAO formulations. Tribological performance was evaluated using a tribometer, and worn surfaces were analyzed by SEM and EDS to characterize tribofilm formation. Results demonstrate that the proposed material provides friction stability and wear resistance comparable to copper in both LS and NAO formulations. Partial substitution of steel fibers improved wear resistance by up to 75%, while synergistic addition with iron sulfide further enhanced friction and wear performance in copper-free NAO pads. These findings highlight the potential of this recycled material as a sustainable and effective alternative for copper-free brake pads, offering both environmental benefits and high tribological performance while reducing reliance on critical raw materials.
Jara, Diego Chávez, Lorenzana, Carlos
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
Test Procedures for Shear Strength of Automotive Brake Pads and Brake Lining AssembliesJ840_202603 (Current)3/31/2026
This SAE Recommended Practice covers equipment capabilities and the test procedure to quantify and qualify the shear strength between the friction material and backing plate or brake shoe for automotive applications. This SAE Recommended Practice is applicable to: bonded drum brake linings; integrally molded disc brake pads; disc brake pads and backing plate assemblies using mechanical retention systems (MRS); coupons from drum brake shoes or disc brake pad assemblies. The test and its results are also useful for short, semi-quantitative verification of the bonding and molding process. This Recommended Practice is applicable during product and process development, product verification and quality control. This Recommended Practice does not replicate or predict actual vehicle performance or part durability.
Brake Linings Standards Committee
Brake Pads, Lining, Disc, and Drum Wear MeasurementsJ2986_202602 (Current)2/19/2026
This SAE Recommended Practice provides a common method to measure wear of friction materials (brake pad assemblies and brake shoes) and their mating parts (brake disc or brake drum). These wear measurements apply to brakes fitted on passenger cars and light trucks up to 4536 kg of Gross Vehicle Weight Rating under the Federal Motor Vehicle Safety Standard (FMVSS), or vehicles category M1 (passenger cars up to nine occupants, including the driver) under the European Community’s ECE Regulations.
Brake Dynamometer Standards Committee
Vibrational Analysis of Hybrid Composite Laminated Plates of E – Glass and Areca Fibers with Brake Pad Waste Powder2026-28-00732/12/2026
This study focuses on the vibration analysis of hybrid composite laminated plates fabricated from E-glass Fiber and areca Fiber reinforced with epoxy resin. The hybrid laminates were prepared using the Vacuum Assisted Resin Transfer Moulding (VARTM) process with different stacking sequences and Fiber ratios, where brake lining powder was also incorporated as a filler in selected configurations to enhance mechanical and damping properties. The fabricated plates (280 × 280 mm) were subjected to experimental modal analysis using an impact hammer and accelerometer setup, with data acquisition carried out through DEWESoft software. Natural frequencies and damping ratios were determined under three boundary conditions (C- C-C-C, C-F-C-F, and C-F-F-F). The results revealed that Plate 1, with E-glass outer layers, areca reinforcement, and filler addition, exhibited the best vibration performance, achieving a maximum natural frequency of 332.8 Hz under C-C-C-C condition, while Plate 2 showed a balanced response and Plate 3 demonstrated higher stiffness but lower damping capability. These findings suggest that incorporating areca Fiber in combination with E-glass not only reduces weight but also improves damping without significantly compromising structural integrity. The developed hybrid composites hold strong potential for lightweight, vibration-sensitive applications such as automotive interiors, marine structures, construction panels, and sports equipment, where both sustainability and performance are critical.
D R, Rajkumar, O, Vivin Lenin, R, Saktheevel, R G, Ajay Krishna, Ng, Bhavan
Agricultural Tractor Brake Linkage Efficiency Prediction and Correlation Using Flexible Multibody Dynamics Model2026-26-01031/16/2026
In agricultural tractors, braking actuation is usually done through control linkages consisting of a series of connected four-bar linkages with multiple pivots from the pedal to the brake pads. The quality of force transmission is critical as it directly affects the braking performance of the tractor. Forces measured at the end of the control linkage or brake pull rod often show deviation from theoretical values based on mechanical advantage calculations. This is due to various factors such as linkage transmission angle, elasticity, and friction losses in joints. A standardized simulation method needs to be developed and validated to predict the losses in the control linkage system. In this paper, the author proposes a simulation approach using multi-body dynamics, which includes contribution factors such as transmission angle, linkage elasticity, and friction in joints. MBS models for brake linkage systems for three different tractors were developed with flex bodies using ADAMS/View software. Coulomb friction and LuGre friction models were used to describe friction in joints. Force on the brake pull rod of the simulation model correlated with measured test data, showing above 85% correlation. The developed method can be adopted to design efficient brake linkage systems for agricultural tractors.
Subbaiyan, Prasanna Balaji, Nizampatnam, Balaramakrishna, Redkar, Dinesh, Arun, G, K, Vinoth, R, Sengottu, Paulraj, Lemuel
Multi-Physics Numerical Modelling of a Magnetorheological Braking System2025-36-005012/18/2025
The global effort to reconsider transport in compliance with ecological challenges leads to a significant increase in the market share of Electric Vehicles (EVs), enlightening secondary sources of pollution. One of the most important is the particles emitted by the abrasion of braking pads. The innovative system addressed in this paper is among the most promising non-polluting solutions to ensure safety and comfort. It uses the capability of the Magneto-Rheological Fluid (MRF) to change its properties when subjected to a magnetic field, generating a braking torque between a stator and a rotor. This study focuses on characterizing the system's performance and endurance during an emergency braking situation by developing a numerical model that involves fluid and structural considerations. This model takes the form of a Finite-Element Model (FEM) that interpolates local forces determined from Computational Fluid Dynamics (CFD) and takes them as input. It enables analysis of the stresses induced by the variation of fluid behavior described by a Bingham theoretical model developed following experimental rheological results.
de Carvalho Pinheiro, Henrique, Billiant, Lucas, Imberti1, Giovanni, Carello, Massimiliana
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
Wear Test Procedure on Inertia Dynamometer for Brake Friction MaterialsJ2707_202509 (Current)9/23/2025
This RP specifies a dynamometer test procedure to characterize wear rates of automotive service brake linings (brake shoes) and disc brake pads.
Brake Dynamometer Standards Committee
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
Further Investigation of Variables Affecting Brake Squeal: Porosity Effect on Lowmet Pad Properties2025-01-03359/15/2025
As Lowmet pad porosity increases, pad hardness decreases; pad ISO compressibility increases; the nominal friction coefficient increases (SAE J2522); and the disc wear/pad wear decreases. Brake squeal occurrence is affected by the total wear of disc and pads; the wear differential between the inboard pad and outboard pad; pad tangential taper; and pad hardness/material damping. Also, pad chamfer shape has a strong influence on brake squeal occurrence.
Rhee, Seong Kwan, Rathee, Aman, Singh, Shiv Raj, Sharma, Devendra
Anti-Noise Brake Pads Shims: T-Pull Test and Bond CoverageJ2694_202503 (Current)3/5/2025
This recommended practice covers the attachment of bonded anti-noise brake pad shims only. Mechanically attached shims (those without bonding) are not covered by this procedure.
Brake Linings Standards Committee
Study of Mechanical, Barrier and Tribological Behaviour of Jute & Glass Fiber Epoxy Hybrid Polymer2025-28-00312/7/2025
The incorporation of natural available material into synthetic materials to form a fiber within a single polymer matrix has been ignited since environment concerns become crucial nowadays. Composite materials embedded with two or more types of fibers makes a composite as hybrid. The study of hybridization of natural and synthetic fibers brings out superior mechanical and tribological properties. In our present studies, fabrication of jute & glass fiber reinforced epoxy-based polymer hybrid composites were carried out using resin infusion technique. For comparing the various properties, the composite made of pure jute fiber i.e 100% jute, pure glass fiber i.e 100% glass, the hybrid composite containing 75% jute and 25% glass fiber, 50% jute and 50% glass fiber, and 25% jute and 75% glass fiber were made and its functional behaviors were studied. The results revealed the hybrid composite containing 25% jute and 75% glass fiber possessed maximum tensile strength of 292±5.8 MPa, flexural strength of 188.3±3.7 MPa, impact strength of 130±2.6 kJ/m2, storage modulus of 17050MPa, loss modulus of 2883MPa, and minimum moisture absorption and wear loss. As compared with the obtained values of composite containing pure jute fiber, tensile strength was increased by 346%, flexural strength increased by 278%, impact strength increased by 227%, hardness increased by 184%, storage modulus increased by 431%, loss modulus increased by 454%, moisture absorption decreased by 88% and wear loss decreased by 100% . Thus prepared hybrid composites, could be employed in different automobile components such as panels, fenders, engine components, brake pad materials, bonnets and heat shields.
J, Chandradass, T, Thirugnanasambandham, M, Amutha Surabi, P, Baskara Sethupathi, Rajendran, R, Murugadoss, Palanivendhan
Composite Brake Pads Reinforcement with Natural Fiber: A Comparative Analysis of Mechanical and Thermal Properties2024-01-511212/30/2024
This work pioneers the development of eco-friendly brake pads using coconut fiber and sawdust as reinforcement materials, combined with abrasives and friction modifiers. The innovation lies in the utilization of these natural fibers, which are not only cost-effective and abundantly available but also contribute to the sustainability of brake pad manufacturing. The study aims to explore the feasibility and performance of these organic fibers in brake pad applications. Coconut fiber and sawdust were chosen for their unique properties, such as high strength-to-weight ratio and thermal stability, making them ideal candidates for enhancing brake pad performance. The inclusion of abrasives and friction modifiers further optimizes the braking efficiency and durability of the pads. Comprehensive testing was conducted, including hardness, compression, wear (using a pin-on-disc apparatus), and thermogravimetric analysis (TGA), to thoroughly evaluate the mechanical properties and thermal stability of the fabricated brake pads. The results demonstrated that the brake pads possess satisfactory hardness, compression strength, and wear resistance, aligning with industry standards for organic brake pads. Notably, the TGA indicated excellent thermal stability, even under elevated temperatures, underscoring the material’s robustness. This project underscores the potential of using coconut fiber and sawdust in the formulation of organic brake pads, offering a sustainable and high-performance alternative to conventional materials. The novelty of this work lies in the strategic selection and combination of natural fibers with advanced testing to validate their application in automotive braking systems. Future research will focus on optimizing the composition and refining the manufacturing processes to further enhance performance and environmental benefits, paving the way for more sustainable practices in the automotive industry.
Ajay Devan, V., Gunasekar, N., Ravikumar, K., Balaguru, B. A., Deepak, S.
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
TOC99-06-05-0TOC10/10/2024
TOC
Tobolski, Sue
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
Brake Particle Emission Influenced by Grooved Disc Friction Surfaces with or without a Hard Coating2024-01-30309/8/2024
Many performance sport passenger vehicles use drilled or grooved cast iron brake rotors for a better braking performance or a cosmetic reason. Such brake rotors would unfortunately cause more brake dust emission, appearing with dirty wheel rims. To better understand the effects of such brake rotors on particle emission, a pin-on-disc tribometer with two particle emission measurement devices was used to monitor and collect the emitted airborne particles. The first device was an aerodynamic particle sizer, which is capable of measuring particles ranging from 0.5 to 20 μm. The second device was a condensation particle counter, which measures and collects particles from 4 nm to 3 μm. The testing samples were scaled-down brake discs (100 mm in diameter) against low-metallic brake pads. Two machined surface conditions (plain and grooved) with uncoated or ceramic-coated friction surfaces were selected for the investigation. The results showed that the grooved friction surface led to a higher particle emission than a plain friction surface finish. The ceramic coating can indeed reduce the negative effect of the grooving through reductions of both the brake wear and particle emission.
Cai, Ran, Nie, Xueyuan, Lyu, Yezhe, Wahlström, Jens
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
Initial Corrosion and Wear Behavior of Brake Rotors Treated with Plasma Electrolytic Aluminating or Ferritic Nitrocarburizing Process2024-01-30439/8/2024
To combat corrosion and wear issues of automotive brake discs, many manufacturers have introduced various surface treatment technologies, such as thermal spraying, laser cladding, and ferritic nitrocarburizing (FNC). Besides those surface treatment technologies, a plasma electrolytic aluminating (PEA) process has also shown to be effective in producing alumina-based ceramic coatings on cast iron substrates, providing an enhanced corrosion resistance. In this study, the PEA-coated brake rotor and FNC-treated brake rotor were comparatively tested in various corrosion conditions, including an electrochemical corrosion test and simulative corrosion experiment, before and after a road driving test. A scanning electron microscope (SEM) and an energy-dispersive X-ray (EDX) were used to observe and analyze morphology and chemical compositions of the surfaces and cross-sections of the tested rotors. The results showed that the new PEA-coated brake rotor demonstrated the best corrosion resistance in the electrochemical corrosion test among all given tested cases. After the vehicle test, the PEA-coated rotor surface had an obvious materials transfer layer which can protect the rotor from abrasive wear. The transfer layer materials sourcing from the low-met brake pads however contained metallic elements, leading to appearance of a lower corrosion resistance during the electrochemical corrosion test. In duration of the vehicle road test (1000 braking events at 0.3-0.4 g), the FNC brake rotor showed some loss of its white layer but maintained its nitrogen diffusion layer, which still showed protection to the brake rotor base material from corrosion. It was also found that some surface areas where the graphite flakes were located on FNC-treated cast iron brake disc surface were exposed to the ambient environment, which may be a reason why the localized corrosion appeared on the FNC-treated rotor in the late stage of the vehicle road test.
Liu, Yinting, Nie, Xueyuan
Low-Speed Stop and Near Zero-Speed Start-to-Move Brake Noise: Effect of Moisture Adsorption, Prior Braking and Deceleration Rate2024-01-30579/8/2024
The influence of moisture adsorption, prior braking, and deceleration rate on the low-speed braking noise has been investigated, using copper-free disc pads on a passenger car. With increasing moisture adsorption time, decreasing severity of prior braking or increasing deceleration rate, the noise sound level increases for the air-borne exterior noise as well as for the structure-borne interior noise. The near-end stop noise and the zero-speed start-to-move noise show a good correlation. Also, a good correlation is found between the noise measured on a noise dynamometer and on a vehicle for the air-borne noise. All the variables need to be precisely controlled to achieve repeatable and reliable results for dynamometer and vehicle braking groan noise tests. It appears that the zero-speed start-to-move vehicle interior noise is caused by the pre-slip vibration of the brake: further research is needed.
Sriwiboon, Meechai, Rhee, Seong Kwan, Sukultanasorn, Jittrathep, Kunthong, Jitpanu
Analysis of Disc-Brake Squeal Considering Lining Wear2024-01-30369/8/2024
Brake squeal is a phenomenon caused by various factors such as stiffness of brake components, mode coupling, friction coefficient, friction force variation, pressure, temperature and humidity. FEA simulation is effective at predicting and investigating the cause of brake squeal, and is widely used. However, in many FEA simulations, models of brake lining are mostly a brand-new shaper, so that the change of pressure distribution or pad shape, which can occur due to the lining wear, are not taken account. In this research, brake squeal analysis was conducted with consideration of lining wear, applying Fortran codes for Abaqus user subroutine. The brake assembly model for the analysis is created by using a 3D scanner and has a close shape to the real one. The wear patterns calculated by the analysis are similar to those of brake pads after a noise test. The complex eigenvalue analysis shows two unstable modes at the frequency of squeal occurred in the noise test. One is out-of-plane vibration mode of the rotor and another is in-plane vibration mode of the rotor. These modes do not come out in the case of analysis with a brand-new lining shape. The results of parameter studies on physical properties and geometries of brake lining show the analysis model in this research is effective in reducing squeal of the brake system.
Ikegami, Tokunosuke, Millsap, Tom, Yamaguchi, Yoshiyuki
Moisture Adsorption and Compression Deformation Behavior of Semimet vs. NAO Brake Pads: Effect of Pad Cure Temperatures and Moisture Adsorption on Low-Speed Friction2024-01-30569/8/2024
Moisture adsorption and compression deformation behaviors of Semimet and Non-Asbestos Organic brake pads were studied and compared for the pads cured at 120, 180 and 240 0C. The 2 types of pads were very similar in moisture adsorption behavior despite significant differences in composition. After being subjected to humidity and repeated compression to 160 bars, they all deform via the poroviscoelastoplastic mechanism, become harder to compress, and do not fully recover the original thickness after the pressure is released for 24 hours. In the case of the Semimet pads, the highest deformation occurs with the 240 °C-cure pads. In the case of the NAO pads, the highest deformation occurs with the 120 0C-cure pads. In addition, the effect of pad cure temperatures and moisture adsorption on low-speed friction was investigated. As pad properties change all the time in storage and in service because of continuously changing humidity, brake temperature and pressure, one must question any approach trying to relate unused virgin pad properties to brake friction and noise in service, including any attempt to model or simulate brake friction and noise using virgin pad properties.
Rhee, Seong Kwan, Rathee, Aman, Singh, Shivraj, Sharma, Devendra
Investigation on Brake-Drag-Optimization on Vehicle-Level2024-01-30379/8/2024
Brake drag in disc brakes occurs during the off-brake-phase, when the brake is not applied but friction contacts between brake disc and pads persist. First and foremost, the resulting drag torque increases energy consumption, where a few Newton meters can have a significant impact on the crucial factor – range – of battery-electric-vehicles. Moreover, brake wear is accelerated in conjunction with enlarged taper-wear of the pads. Additional wear can also imply increased brake particle emissions which are going to be limited by upcoming regulations due to their potential health risk. In this light different countermeasures aim to create and maintain a sufficient air gap between brake disc and pads when the brake is released to avoid residual friction contacts. Among others these include optimization of piston retraction by adjusting the seal-grooves and integrating pad springs into the caliper to push the pads back. State of the art to analyze the effectiveness of countermeasures are component-level tests on brake dynamometers. As they provide high repeatability and the necessary accuracy to develop brakes with drag near zero. Though the laboratory conditions usually exclude influencing factors that are present on vehicle-level and can have a significant impact on brake drag, for example lateral acceleration. Therefore, this work uses a prototypical drag torque measurement system based on piezo-electric sensors to analyze, whether countermeasures that have been proven to be effective on component level also reduce brake drag on vehicle-level. A default brake setup with relatively high brake drag is compared to an optimized setup during chassis dynamometer tests, certain driving maneuvers on proving grounds and a real-driving cycle on the road.
Huchtkoetter, Philipp, Neubeck, Jens, Wagner, Andreas
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
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
Effect of Surface Roughness on Tribological and NVH Behaviour of Brake System2024-01-27324/9/2024
Brake assemblies are an essential part of any vehicle, and their effective functioning is critical for the safety and comfort of passengers. The surface roughness of brake components plays a vital role in figuring out their tribological and NVH (Noise, Vibration, and Harshness) behavior. It is essential to understand the impact of surface roughness on brake performance to ensure efficient braking and it has been a topic of interest in the automotive industry. In this study, the influence of surface roughness on the wear, and noise characteristics of a brake assembly has been investigated. The study also provides insights into the relationship between surface roughness, frictional behavior, and NVH performance, which can be used to improve the design and manufacturing of brake assemblies. The brake assembly includes of a disc, caliper, and brake pads, which work together to convert the kinetic energy of the vehicle into heat energy, has been considered in this study. First, the tribological behavior of the brake assembly under varying surface roughness conditions has been studied. The roughness of the rotor affected the formation of a transfer layer on the brake pad, which contributed to the frictional behavior of the assembly. Increase in surface roughness results in increased contact area and adhesion between the rubbing surfaces, leading to higher frictional forces and wear. The wear of the brake pads and their respective operational life is calculated according to different surface roughness conditions. Another crucial parameter affected by surface roughness is the NVH behavior of brake assemblies. The surface roughness of brake components alters the contact pressure distribution and affects the vibration behavior of the brake system. The change in NVH performance according to the surface roughness value is predicted. This study highlights the importance of considering surface roughness as a critical parameter in the design and development of brake assemblies. The findings of this study can help the automotive industry and improve the safety and comfort of vehicle occupants.
S, Gurumoorthy, Bhimchand, Naresh, Bourgeau, Alyssa, Bhumireddy, Yugandhar
Gap Adjustment Strategy for Electromechanical Brake System Based on Critical Point Identification2024-01-23204/9/2024
Abrasion of the Electromechanical brake (EMB) brake pad during the braking process leads to an increase in brake gap, which adversely affects braking performance. Therefore, it is imperative to promptly detect brake pad abrasion and adjust the brake gap accordingly. However, the addition of extra gap adjustment or sensor detection devices will bring extra size and cost to the brake system. In this study, we propose an innovative EMB gap active adjustment strategy by employing modeling and analysis of the braking process. This strategy involves identifying the contact and separation points of the braking process based on the differential current signal. Theoretical analysis and simulation results demonstrate that this gap adjustment strategy can effectively regulate the brake gap, mitigate the adverse effects of brake disk abrasion, and notably reduce the response time of the braking force output. Monitoring is critical to accurately control EMB clamping force. Pressure transducers are often expensive and have limited accuracy in high-temperature environments, so an estimate of the clamping force is required. In this research, the clamping force is estimated based on the identified contact points and the stiffness profile of the EMB. This method performs exceptionally well under low stiffness conditions and maintains a narrow error range even in high-stiffness scenarios.
Zhang, Yilong, Chen, Zixuan, Wu, Jinglai, Zhang, Yunqing
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
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
Development of Organic Reinforcement Composite Materials for Brake Pads2023-28-006911/10/2023
Commercial brake pads are being wind down because of asbestos fibre which causes carcinogenic effect. By observing it is obligatory to analyse about the alternate materials for brake pads additionally there are heaps of alternatives for asbestos furthermore to develop an organic composite material for brake pads using organic fibers including grind orange peel and banana peel as the reinforcement material. Disparate alternatives for filler materials and different binders such as epoxy resin, phenolic resin and distinctive organic materials used to alter the material for asbestos fiber and studied miscellaneous possible formulations and their effect on the performance of the brake pads by varying the reinforcement composition from 20% - 30%, binding material from 30% - 40%, filler materials as 17.5%, friction modifiers as 22.5%, and fabricated the material for brake pads using grinded orange peel and banana peel as reinforcement further performed hardness test and wear test to compare results among samples. The hardness is greater for the composition R 25% + EP 35%. And the same composition has less wear. The optimum content of reinforcement is 25% and for epoxy resin is 35%. In comparison between composite materials made with orange peel powder and banana peel powder as reinforcement, the samples made with banana peel powder has better braking performance than samples made with orange peel powder.
Jamuna Rani, G, Konda, Chaitanya Sai Teja, Gollamudi, Srivalli, Lakshmipuram, Naveen Babu
Some Considerations for Brake-Based Park Systems, Including Residual Drag Impact2023-01-187811/5/2023
Brake-based park systems, where an electric parking brake system becomes fully responsible for vehicle immobilization and enables elimination of the traditional driveline-based parking pawl, has increased in popularity, especially in full Electric Vehicles. At face value, the promise of saving mass, cost, and critical packaging space in an electric drive unit is compelling. However, this must be weighed carefully against less obvious impacts, which include engineering in added redundancy, significant changes in “real world” duty cycle of EPB components, risk of brake pad and rotor crevice corrosion, and perhaps most acutely because it affects every drive cycle, the impact to residual drag and therefore vehicle energy use. The present work endeavors to present a balanced view of the considerations, both advantages and tradeoffs, for brake-based park systems, with a special focus on the residual drag behavior because it is perhaps the most difficult to characterize, most variable in its behavior, but most impactful to the vehicle effect.
Antanaitis, David, Harris, Maria Richelle, Connor, Kevin, Riefe, Mark
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
Simulated LACT Procedure for Predicting Lining Life for Vehicles with Regenerative Braking2023-01-189211/5/2023
The Simulated Los Angeles City Traffic (SLACT) test is a well-established dynamometer test procedure used to evaluate brake noise and lining wear performance under a typical US city driving conditions. This procedure is based on a vehicle test conducted on the roads of Los Angeles, California. Unlike ICE vehicles, in electric vehicles regenerative brakes do a significant amount of the work to stop the vehicle, resulting in less work required from the foundation brakes. This means that the life of a brake pad could significantly increase in electric vehicles. It is possible then to reduce the thickness of the brake pad to improve packaging and cost. However, in situations where regenerative braking is disabled due to a failure or low battery charge level, all the work must be done by the foundation brake with no support from the regenerative braking. Hence, it is crucial to select the optimal brake pad thickness for such scenarios. The SLACT test was designed primarily for ICE vehicles and may not represent the lining life of electric vehicles accurately. As more auto manufacturers have started developing electric vehicles, there is now a need to establish a test procedure that considers regenerative braking for lining life predictions. This paper discusses in detail a modified SLACT test procedure that considers regenerative braking for electric vehicle lining life prediction.
Jayyousi, Wael, Divakaruni, Saikiran
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