Browse Topic: Brake discs

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Driveline Parking Brake Test Procedure for Medium Duty VehiclesJ2690_202110 (Current)10/28/2021
This SAE Recommended Practice establishes uniform test procedures for friction based parking brake components used in conjunction with hydraulic service braked vehicles with a gross vehicle weight rating greater than 4500 kg (10 000 lb). The components covered in this document are the primary actuation and the foundation park brake. Various peripheral devices such as application dashboard switches or indicators are not included. These test procedures include the following: a Brake Related Tests 1 Brake Functional Performance 2 Brake Dynamic Torque Performance 3 Brake Corrosion Resistance 4 Brake Endurance with Torque 5 Brake Endurance without Torque 6 Vibration Resistance 7 Brake Ultimate Static Load 8 Brake Lining Wear Adjuster Function b Actuation Related Tests 1 Mechanical Actuator Functional Performance 2 Mechanical Actuator Endurance 3 Mechanical Actuator Quick Release 4 Mechanical Actuator Ultimate Load 5 Spring Apply Actuator Functional Performance 6 Spring Apply Actuator Operating Temperature Range 7 Spring Apply Actuator Endurance 8 Spring Apply Actuator Corrosion Resistance 9 Spring Apply Actuator On-Off Switch 10 Spring Apply Actuator Vibration
Truck and Bus Hydraulic Brake Committee
Low-Duty Inertia Dynamometer Hydraulic Brake Wear Test Procedures for Vehicles Above 4536 kg (10000 pounds) of GVWRJ3006_202005 (Current)5/26/2020
This Recommended Practice is derived from OEM and tier-1 laboratory tests and applies to two-axle multipurpose passenger vehicles, or trucks with a GVWR above 4536 kg (10 000 pounds) equipped with hydraulic disc or drum service brakes. Before conducting testing for a specific brake sizes or under specific test conditions, review, agree upon, and document with the test requestor any deviations from the test procedure. Also, the applicable criteria for the final test results and wear rates deemed as significantly different require definition, assessment, and proper documentation; especially as this will determine whether or not Method B testing is needed. This Recommended Practice does not evaluate or quantify other brake system characteristics such as performance, noise, judder, ABS performance, or braking under extreme temperatures or speeds. Minimum performance requirements are not part of this recommended practice. Consistency and margin of pass/fail of the minimum requirements related to wear rates and wear behavior can be assessed as part of the project in coordination with the test requestor. NOTE: This Recommended Practice uses the unit conversion and rounding techniques from the NIST Special Publication 811. This to ensure the use of standard conversion factors and to determine the appropriate number of significant digits to ensure the Rounding Error (RE) of the converted unit is smaller than or similar to the RE of the original English or Imperial unit.
Truck and Bus Hydraulic Brake Committee
Model-Based Brake Disc Temperature Prediction on High Speed Testing Mode and Circuit2020-01-02144/14/2020
A brake is a mechanical device that inhibits the motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by friction energy. Commonly, most brakes use friction between two surfaces pressed together to convert the kinetic energy of the moving object into heat, though other methods of energy conversion may be employed. If braking is repeated or sustained in high load or high-speed conditions, the motion will be unstable and can lead to a loss of stopping power because the disc capability for braking is not enough. These phenomena are generally defined as brake fading. Brake fade is caused by an overheating brake system. This paper describes the thermal modeling and process to predict the disk temperature under a condition which causes the fade characteristics. Also, the model of disc temperature prediction developed with consideration of acceleration and deceleration from the vehicle specification by combining the full vehicle modeling with thermal disc model. The disc temperature model is a highly reliable model because it is correlated with measurement data and based on this correlated thermal model, it can be predicted the brake disc geometrical parameters according to the specification change of the vehicles in the concept stage before the prototype development.
Jeong, PilYoung, Lee, Jaekil, Oswald, Mario, Kellner, Stefan
Flow Field Experimental Study in Brake Discs with Aerodynamic Ventilation Columns06-13-01-00042/27/2020
This work presents a new design of ventilation pillars in ventilated brake discs. The use of National Advisory Committee for Aeronautics (NACA) aerodynamic profiles is proposed. Of the references consulted, there is no standard or procedure that indicates how the pillars should be installed in the ventilated discs. Therefore, it is proposed using the Kaplan’s error triangles theory of turbo hydraulic machinery to have a geometrically orderly way of placing the NACA 66-209 profiles from the suction diameter to the discharge diameter. To validate this new design, a 1:1 scale acrylic disc model was constructed, and tests were conducted in water using the particle tracking velocimetry technique to characterize the water model. The water experiment was performed at test speeds of 35, 41, 48, and 54 rpm. From the experiment in water, it is possible to visualize the flow field from the suction diameter to the model discharge diameter and scale the results to the prototype in air. Being 54 rpm in water equivalent to N = 1020 rpm in air, the radial velocity is 15.4% higher than a straight vanes disc. In addition, comparing the mass flow at the point of maximum speed, it is observed that the results obtained in this work are 40.21%, 65.49%, and 98.11% higher than those obtained by other works. Finally, the error of the accumulated experimental bias is extremely low, where the maximum error did not reach 1.17%. For this reason, it can be ensured that both the measurements made as well as the results obtained are highly reliable.
Rivera López, Jesús Eduardo, Gutiérrez Paredes, Guadalupe Juliana, Quintero Orozco, Abner, Tamayo Meza, Pedro Alejandro, Orozco Durán, Gabriela Esmeralda, Arciniega Martínez, José Luis
Regressions of brake pads compressibility from experimental data2019-36-00141/13/2020
One of the critical characteristics in a brake pad is its deformation when subjected to compressive loads. This deformation is called compressibility, which can be obtained quantitatively through compression cycles performed by a specific test bench. However, such testing is costly and long enough not to meet the demand of manufacturers of friction materials. To overcome this difficulty, this work presents regressions for the estimation of compressibility through the natural frequencies of the pads, since they can be obtained quickly and at low cost through a simple modal analysis. The theoretical basis for the correlation between compressibility and natural frequencies includes the theory of elasticity - which defines an inverse relationship between strain and stiffness - and the theory of vibrations, which defines the natural frequencies of a mechanical system as a function of its mass matrices and stiffness. Since the dependent variable (compressibility) and explanatory variable (natural frequency) are linked to stiffness, it is theoretically plausible to direct estimative. As additional explanatory variables, in addition to the experimental data of natural frequencies, the work uses the mass values and the temperature during the natural frequency measurement to improve the regression models.
Suetti, André Garcia Lima
Influence of Pads and Brake Disc wear on Brake Squeal Noise2019-36-00051/13/2020
The present work aims to investigate the influence of wear of the pads and brake disc on the brake squeal behavior with the help of the Finite Element tool. Brake discs basically work by the pressure of the brake pads against a rotating disc. The friction between the pads and the disc causes the latter to decelerate, but it can also cause dynamic instabilities of the system giving rise to noises. Among the main noise in vehicle brake systems, there is the squeal noise, which is usually associated with the coupling of two neighboring natural modes. One possible way to identify unstable modes is by extracting complex eigenvalues from the system. An unstable mode can be identified when, in the result of the extraction of the complex eigenvalues, the real part of the eigenvalue is positive. In the present work, a brake system (disc and positioned pads and their respective materials and friction coefficients) was duly modeled and validated. The validation was done by means of a correlation between the frequency of the noises found experimentally and the frequency of the unstable modes found in the virtual model. A parametric analysis was performed simulating the wear of the disks and pads to understand the effect of the mass variations and stiffness on the instability of the system. According to the results found in the analyzes that simulate the wear, with the decrease, mainly the thickness of the brake pads, there was an increase of numbers of unstable modes, that is, the brake system is more prone to squeal generation.
dos Anjos, Marco Túlio Batista, Gutiérrez, Juan Carlos Horta, Ferreto, Cláudio Junior, Silva, Felipe Dornellas, Donadon, Lázaro Valentin
Performance Gains of Load Sensing Brake Force Distribution in Motorcycles2019-28-242611/21/2019
Commercial motorcycles and scooters incorporate independent circuits for front and rear brake actuation, thus precluding load-dependent brake force distribution. In all cases of manual brake force modulation between the front and rear wheels, there is poor compensation for the changes in wheel loads on the account of longitudinal weight transfer, thus making it challenging to provide an adequate braking force to each wheel. The ratio in which the braking force should be distributed between the front and the rear wheels is dependent on the motorcycle’s geometry, weight distribution, mechanical sizing of braking system components, and is a variable based on the instantaneous deceleration. This connotes that a fixed bias of front and rear braking forces can be optimized only for a narrow range of motorcycle’s deceleration. Maximum braking performance occurs just prior to wheel lock-up, as a sliding tire provides less grip than a rolling tire. This is also the scenario when both the tires are doing the maximum work in decelerating the motorcycle. Therefore an optimal brake force distribution is one that locks both the wheels at the same instant. In practice, however, a rider would avoid a front wheel lock-up as it would make the motorcycle challenging to steer. In theory, an apt distribution of the braking forces between the front and rear wheels maximizes the overall braking efficiency of the motorcycle whilst reducing its stopping distance. This paper examines the plausible performance gains of load sensing brake force distribution in a motorcycle.
Chakraborty, Apurva
A New Appraisal of the Thermomechanical Behaviour of a Hybrid Composite Brake Disc in a Formula Vehicle2019-28-257211/21/2019
The present work promotes a hybrid composite brake disc for thermal and structural analysis of a formula vehicle. In order to reduce the un-sprung weight without compromising the strength, hybrid composite materials were incorporated in the disc plates of the braking system. In the disk brake system, the disc is a major part of a device used for slowing or stopping the rotation of a wheel. Repetitive braking of the vehicle leads to heat generation during each braking condition. Based on the practical understanding the brake disc was remodeled with unique slotting patterns and grooves, using the selected aluminium alloy of (AA8081) with reinforcement particle of 15wt% Silicon carbide (SiC) and 3wt% Graphite (Gr) as a hybrid composite material for this proposed work. By varying slotting pattern and groove angles the transient thermal and structural analysis using ANSYS workbench on the hybrid composite disc plate of disk brake is done. The main purpose of this study is to analyse the thermomechanical behavior of composite brake disc for a formula vehicle under severe braking conditions. To ensure the braking conditions, the coupled field analysis is done on the disk brake to determine the deformation and the Von Mises stress developed in the disc for both solid disk and disk provided with multiple ventilations (slotting patterns and grooves angles) using the hybrid composite material to improve the performance of the brake disc. Hence the best suitable design of disc plate with the hybrid composite material is recommended based on the performance, strength and rigidity criteria. Also, it will be recommended for fabrication and real-time usage in formula vehicles.
Ranganathan, Soundararajan, Kuppuraj, Sathishkumar, Gopal, Shanthosh, Chandrasakaran, Pradeep
Nondestructive Measurement of Residual Strain in Connecting Rods Using Neutrons05-12-03-001810/15/2019
Abstract Increasing the strength of materials is effective in reducing weight and boosting structural part performance, but there are cases where the residual strain generated during the process of manufacturing of high-strength materials results in a decline of durability. It is therefore important to understand how the residual strain in a manufactured component changes due to processing conditions. In the case of a connecting rod, because the strain load on the connecting rod rib sections is high, it is necessary to clearly understand the distribution of strain in the ribs. However, because residual strain is generally measured by using X-ray diffractometers or strain gauges, measurements are limited to the surface layer of the parts. Neutron beams, however, have a higher penetration depth than X-rays, allowing for strain measurement in the bulk material. The research discussed within this article consists of nondestructive residual strain measurements in the interior of connecting rods using the Second Generation Neutron Residual Stress Mapping Facility (NRSF2) at Oak Ridge National Laboratory (ORNL), measuring the Fe (211) diffraction peak position of the ferrite phase. The interior strain distribution of the connecting rod, which was prepared under different manufacturing processes, was revealed. By the visualization of interior strains, clear understandings of differences in various processing conditions were obtained. In addition, it is known that the peak width, which is also obtained during measurement, is suggestive of the size of crystallites in the structure; however, the peak width can additionally be caused by microstresses and material dislocations.
Ikeda, Tomohiro, Jeffery, Bunn R., Fancher, Christopher M., Motani, Ryuta, Matsuda, Hideki, Okayama, Tatsuya
Fatigue Life Prediction of Heavy Duty Automobile’s Brake Drum through Coupled Thermo-Mechanical Analysis2019-28-003110/11/2019
The aim of this paper is to demonstrate the methodology to simulate the induced stresses/strains due to thermo-mechanical loading of automobile brake drum.. The brake drum undergoes mechanical load due to applied brake pressure and thermal load due to friction generated between brake pad and brake drum while brake is applied. This coupled thermo-mechanical loading affects the life of the brake drum as the stiffness of the brake drum is reduced. The conventional method of simulating this problem is done using Lagrangian discretization in which the load is applied and inertia effect due to angular velocity is applied to a drum at static condition. In contrast, in this paper Eulerian discretization is adopted for finite element analysis, in which drum brake model is discretized as spatially dependent that facilitates actual rotation of brake drum with simultaneous application of brake load resulting more precise simulation. A sequentially coupled transient thermo-mechanical analysis is carried out using ABAQUS 6.12 simulation tool to predict the induced stresses/strains and fatigue life of the brake drum.
Annamalai, Krishnamoorthy, Naiju, Chooriyaparambil Damodaran
The Improvement Brake’s Qualities of Vehicle by Developing the Method of the Choosing Frictional Pairs of the Brakes Mechanisms2019-01-21459/15/2019
One of the reasons for the large number of road accidents on highways in Ukraine [1] is the instability of the braking properties due to the unstable characteristics of the brake mechanisms’ friction pairs. The manufacturer produces new automobiles with installed brake pairs (brake pads and their counter bodies), which have passed long-term tests for the stability of the friction coefficient and braking forces distribution of between the axles. This ensures the compatibility of the friction pairs characteristics for front and rear brake mechanisms according to the criteria of heat resistance. During operation, instead of worn-out brake pads, brake discs and drums, drivers can purchase new ones, manufactured as spare parts. However, in the well-known literature there are no methods that allow to check the compatibility of the friction pairs characteristics for front and rear brake mechanisms according to the criteria of heat resistance. In the article a method for choosing a set of friction pairs of brake mechanisms for passenger car during operation is proposed. Assessment of the compatibility of the friction pairs characteristics for front and rear brake mechanisms was carried out according to the criteria of heat resistance.
Podrigalo, Mikhail, Klets, Dmytro, Kholodov, Mykhailo, Bogomolov, Viktor, Turenko, Anatoliy, Molodan, Andrii, Rudzinskyi, Volodymyr, Tarasov, Yurii, Mykolai, Aloksa, Hatsko, Vasyl
Frequency Inspection of Brake System Components2019-01-21179/15/2019
Frequency inspection has long been a tool utilized by manufacturers of brake system components as a means of quality control. This is important to combat perceived defectiveness of a system that experiences issues, such as brake squeal, as well as to identify actual defects in the parts going out to customers. Every component has its own resonance frequencies based on the dynamics of that component. Knowledge of the resonance frequencies of each component provides insight that can prevent manufacturers from sending out defective units, whether they be perceived defects or actual defects. NVH engineers who understand these phenomena perform theoretical analysis and acquire experimental data in the lab to gain insight into their parts that will eventually be produced on the assembly line. Unfortunately, the frequency requirements, and the consequences thereof, defined by the NVH engineers can still remain somewhat of a mystery to the manufacturing engineers who are tasked with applying them. Oversights in specifications can lead to avoidable scares that lead to delays and downtime. For example, differences in accelerometer placement on a brake rotor from the lab to the assembly line can lead to issues such as variable frequency reporting. This leads to inaccurate data reporting, which leads to poor Gage R&R. A basic understanding of vibration and how to analyze data would allow the manufacturing engineer to troubleshoot such an issue and prevent unnecessary delays. This paper will attempt to take these concepts beyond the specification sheet and into the science and mathematics behind the dynamics of the different components of the total brake system. The knowledge gleaned from this analysis allows for intelligent decision making for go/no-go on the production line, as well as root cause analysis in the lab.
Cagle, Robert
Brake Rotor Corrosion and Friction Cleaning Effect on Vehicle Judder Performance2019-01-21159/15/2019
Brake disc corrosion has emerged as an important field of study within the automotive industry due to the wide range of lining materials that are currently used worldwide, and their inherent rust-cleaning properties. The presence of oxide layers irregularly deposited on the cast iron disc surfaces usually leads to a forced, braking-induced vibration that can reach the driver’s position as a pronounced annoyance. Hence, the friction material composition directly impacts on the judder performance during the early corrosion-removal stage. This study incorporates both dynamometer and vehicle tests into the definition of a predictive methodology that allows corrosion-induced vibrations to be investigated at both system and vehicle levels. The oxide film is artificially generated by means of a salt spray chamber under steady-state climate conditions in order to guarantee a repetitive and robust procedure. The vibration response of the system is objectively evaluated in the form of caliper accelerations and pressure (BPV) / torque (BTV) oscillations throughout a reduced rust-removal test sequence composed of 30 snubs; basic spectral and order analyses are conducted with the gathered data. Furthermore, vehicle-based results are correlated with the subjective ratings that an expert driver gives to the different vibrations perceived at chassis level. The in-service roughness of the oxide layer, on the other hand, is indirectly monitored by using a couple of non-contacting capacitive sensors that measure the variation in disc thickness (DTV). Ultimately, this paper is intended to characterize the inherent corrosion-cleaning capability of different friction materials -paying special attention to the presence of copper-, as well as revealing their impact on the vehicle judder subsequently induced during the actual removal of the oxide layers.
Molina Montasell, Narcís, Ferrer, Bernat
Development of Regenerative Brake Control Strategy to Remove Brake Rust2019-01-21259/15/2019
This study is the development concept of regenerative braking cooperative control to reduce creep groan noise considering fuel efficiency. Creep groan noise is a traditional brake system noise that has been improved with advances in technology such as brake materials, surface treatment and transfer path. However, recently creep groan noise is again an issue in electronic vehicle which applied a drive motor. Generally, creep groan noise frequently occurs when rust occurs on the friction surface of the brake disc and the brake pad is humidified, but it is easily removed by friction braking several times. However, in the case of electric vehicles which applied regenerative braking system, it is hard to remove. In case of electric vehicle, instead of friction braking, most of brake toques are made by motor regenerative braking. Therefore, even if the same conventional brake system and chassis system are applied, the noise level of the electric vehicle is higher than gasoline or diesel vehicle, and the field claim is also higher. To improve the noise, regenerative braking cooperative control logic was developed that detects long-term vehicle parking condition and control the regenerative brake ratio of total driver demand brake toque considering fuel efficiency. Also several tests are proceeded to review the effect of creep groan noise and fuel efficiency.
Jang, Sora, Kim, Gwichul
The Analysis of Brake Squeal Noise Related to the Friction Properties of Brake Friction Materials2019-01-21329/15/2019
The friction properties related to squeal noise was analyzed with the development histories and simplified computational method. Firstly, the development histories were investigated especially focusing on the case which the friction materials were modified to improve squeal noise occurrence. Based on the histories, the friction properties of selected friction materials were newly measured using dynamometer. The average friction coefficient levels, torque oscillations, the increment of friction coefficient during full-stop, and etc. were compared with the squeal noise occurrence, and the results showed that increase of friction properties cause production of squeal noise. The result suggested that the size of friction energy was important factors related to triggering the squeal noise. Also, the contact conditions between rotor disc and friction materials were significant factors deciding the noise occurrence. We performed simplified computational analysis using MATLAB program to prove the effect of friction energy on the noise occurrence. The friction surfaces were roughly designed and the distribution of contact plateaus was controlled to simulate different contact conditions. The different contact conditions were designed and performed sliding at low velocity condition to observe stick-slip phenomena. The friction energy was calculated with the amplitude of stick-slip for each case. The results showed that when the similar sized contact plateaus were increased, friction energy or the amplitude of stick-slip was also increased. And the total size of contact plateaus, which denote contact area, also affected the amplitude of stick-slip profile. Therefore the computational analysis supported the test results. In this study, we suggest that the design of friction surface considering contact condition is important to reduce triggering of the squeal noise.
Lee, Sang-mok, Woo, Jung Hoon, Cho, Younggu, Kim, Dong Won
A Study of the Disc Scoring Generation Principle and Reduction(III)2019-01-21129/15/2019
In the latest works [12], we presented the guideline for reducing Metal pick up(MPU, the main component of disc scoring) by controlling the location of the roughness of disc, the brake pad friction coefficients and the disc slot's size. In this study, the previously studied iron transfer theory to 'Cu free' brake pad and the disc surface roughness controlling methods which are based on the mass production manufacturing process are applied. It is possible to suggest the ways to improve the scoring-free disc without reducing friction coefficient between the disc and pad, and any demerit such as increased wear and airplane noise like conventional slot discs [11].
Jeong, ByeongUk, Ryu, Hyoung Tae, Jung, Kwang Ki, Kim, Chang Jin, Lee, Hyunkyoung
Inboard Mounted Disc Brake Rotor/Disc Wheel Hub Interface Dimensions - Commercial VehiclesJ2696_201909 (Historical)9/3/2019
This SAE Recommended Practice establishes dimensions and tolerances for the interface between inboard mounted disc brake rotors and disc wheel hubs. This document is intended for inboard mounted disc brake rotors and disc wheel hubs for Class 5, 6, 7, and 8 commercial vehicles. Special and less-common applications are not covered.
Truck and Bus Wheel Committee
Effect of Slot and Chamfer Shape of Brake Pad on Mode Coupling2019-01-14193/25/2019
In the present, one of the essential quality concerns in the automotive industry is brake squeal. Brake pad shape is one of the factors affecting to brake vibration and squeal noise. This research aims to study the effect of slot and chamfer shape on mode coupling through the Finite Element Analysis (FEA), impact hammer testing and performance test from dynamometer. The results can be used to develop geometry of the brake pad surface that leads to brake squeal reduction in the design stage. The natural frequencies and mode shape of brake components calculated by FEA are compared with the impact hammer testing to ensure the accuracy of the results. The FE results are also verified through the standard test with a dynamometer.
Yeamdee, Sirapath, Bovornratanaraks, Thiti, Sriwiboon, Meechai, Chantalakhana, Chak, Ratanasumawong, Chanat
EDITORIAL: The future of motorsports is…quiet19AUTP08_091/1/2019
Perched up on jackstands, its fat Michelin-shod wheels removed, the Audi e-tron FE05 looks like a multicolored shark out of water. Mechanics are swirling around this battery-electric race car, preparing it for a practice session during the Brooklyn E-Prix-the final race of the 2019 FIA Formula E championship season in New York. Standing just outside the garage perimeter on a hot July morning, I watch clouds of steam swirl around the rear of the car, one of two FE05s campaigned by the Audi Sport ABT Schaeffler team. While charging, the 52 kW-h lithium-ion battery is being force-fed cold air through its radiator side pods to keep it thermally happy. The dry-ice clouds are a familiar pit scene in Formula E racing, a signature of the “JuicePump” charging system from Italian renewable-energy giant Enel that is used by each of the 11 teams in this 13-race global series.
Brooke, Lindsay
Properties and Limitation of an Oxide Coated Aluminum Brake Rotor2018-01-187710/5/2018
The electrification of the powertrain and the thereto related recuperation of the electric engine saves the energy in the battery and thus reduces the thermally dissipated brake energy, which leads to lower brake rotor temperatures compared to combustion engine vehicles (ICEVs). These new conditions enable to reconsider brake disc concepts. Including lightweight design in heavy battery electric vehicles (BEVs) and the increasingly reliant corrosion resistance of brake rotors, Aluminum is a promising approach for new brake disc concepts. In the past, Aluminum brake disc concepts have already been deployed. For instance Aluminum Metal-Matrix Composite (Al-MMC) concepts in the Lotus Elise S1 and on the rear axle of the Volvo V40 [1]. The presented concept is a different approach and separates the friction system from the bulk Aluminum brake disc, achieved by coating of the friction rings. By locally reinforcing the friction rings, the good machinability and ductility of the base body is maintained and simultaneously the friction surface is sufficiently protected to resist the frictional loading during a brake application. In this work, fundamental studies on a brake dynamometer were conducted and supplemented by microstructural investigation to identify damage mechanisms and to judge the technical application of the concept.
Gulden, Florian, Gramstat, Sebastian, Stich, Anton, Hoppel, Heinz Werner, Tetzlaff, Ulrich
A New Model Describing the Formation of Heat Cracks in Brake Discs for Commercial Vehicles2018-01-188210/5/2018
During the development process of brake discs for commercial vehicles, heat cracks are a frequent problem. Since no profound model to forecast the occurrence of cracks has been presented yet, their prediction is hardly ever possible. The standardized heat crack test puts the brake disc under severe thermomechanical load and therefore forces it into cracking. In this paper, results from a series of heat crack tests on the dynamometer are presented, which provide insight into the hidden processes that accelerate or slow down the heat crack propagation in brake discs. This includes an extensive experimental setup using a thermographic camera, a set of capacitive displacement sensors, a pyrometer, and sliding thermocouples as well as a unique eddy-current heat crack detector that was developed at TU Darmstadt. Continuous monitoring of disc deformation, surface temperature, and crack propagation at high sampling rates provides the base for a new, profound causal model. The model describes a chain of effects including the qualitative and quantitative influence of the surface temperature distribution to local crack propagation rates in connection with local deformation and coning of the disc. Therefore, spatiotemporal patterns of thermal and mechanical distortions of the disc are compared to each other and to the crack pattern in time and frequency domain. The observation of local hardening effects as well as microstructural transformations in regions of high crack growth completes the model. Furthermore, relations between crack propagation and brake disc design are evaluated, which reveal the influence of the cooling channel pin configuration to the crack propagation. Finally, possible future applications of the model are shown, regarding its ability to forecast the cracking tendency of a certain brake disc design during finite element analysis as well as its integration into the development process of brake discs.
Bilgic Istoc, Sami, Winner, Hermann
Non-Asbestos Organic (NAO) Disc Pad Wear Behavior: Divergence of Thickness Loss and Weight Loss2018-01-186610/5/2018
There is anecdotal evidence that disc pad wear numbers measured in thickness loss and disc pad wear numbers measured in weight loss do not show the same wear trends after wear or performance testing. However, research papers on this topic are difficult to find. Therefore, this investigation was undertaken to study and document this behavior in detail on high-copper, low-copper and no-copper (or copper-free) NAO pads. In all cases, thickness loss measurements are found to be substantially lower than expected from the weight loss data according to the SAE J2522 test schedule. This divergence is caused by pad swelling in the pad layer adjacent to the friction contact surface during brake testing at high temperatures. In addition to formulation changes, disc pad processing conditions such as mixing time and hot molding pressure are found to affect pad swelling. As pad physical properties, especially in the layer adjacent to the friction contact surface, are expected to dynamically change during braking due to the pad swelling, one has to seriously question any attempt to correlate physical properties of unused pads to brake performance and squeal generation. Detailed characterization of the dynamic changes taking place in the pad during testing/usage is recommended to gain better understanding and better prediction of brake performance and squeal.
Sriwiboon, Meechai, Tiempan, Nipon, Kaewlob, Kritsana, Rhee, Seong
Lightweight, Wear Resistant, High Thermal Conductivity Metal Matrix Composite Brake Rotors2018-01-187910/5/2018
Aluminum (Al) - silicon carbide (SiC) metal matrix composite (MMC) brake rotors have been investigated for lightweight vehicular applications but have not widely been utilized due to issues with uniformity of distribution of SiC particulates, residual porosity, formation of undesirable phases such as aluminum carbide, and high temperatures incurred during braking that degrade the rotor’s integrity and performance. ATS-MER has overcome these issues with the development of a patented sandwich type structure with wear resistant thin Al-SiC MMC surface layers and a high thermal conductivity aluminum alloy core. Substantial dynamometer and vehicle testing has been performed by a major automobile company with excellent results, including much lower induced temperatures, 96.3 to 99.6% less particulate (dust) generation in comparable testing of cast iron rotors, and almost 10 times the number of maximum cycles possible during testing of cast iron discs. Thus, ATS-MER’s novel Al-SiC MMC brake rotors offer significant environmental benefits of much reduced dust generation and lower CO2 emissions due to lighter weight including unsprung weight, a more comfortable ride, and elimination of the need to replace the rotors over the life of the vehicle. The unique processing technology will be presented along with the current state of development and performance for conventional and electric vehicles.
Bracamonte, Lori, Withers, James, Smith, Thomas
Instabilities Induced by Thermal-Mechanical Couplings in Clutch and Brake Discs2018-01-189410/5/2018
The interaction between thermal buckling and thermoelastic instability (TEI) can play an importance role in frictionally-excited hot spot development in automotive disc brakes. In this study the distributions of temperature variations were obtained from the eigenmodes based on the classical TEI analyses. The critical buckling temperatures and the associated deformation modes were subsequently computed using the commercial software ABAQUS. The effects of sliding speed, coefficient of friction and boundary conditions have been investigated for both banding and focal modes. It is concluded that the TEI induced temperature variations can significantly alter the distribution of thermal stresses, and that there could exist a strong coupling between TEI and thermal buckling under some conditions. Although the analyses were performed in the settings of clutch applications, the conclusions are applicable to brake discs as well because of the shared similarities. Adding the complexity in the brake disc geometry such as hat and vent sections is an ongoing research.
Yi, Yun-Bo, Shaahu, Joseph-Shaahu, Chen, Zhuo
Numerical Study on Fluid Flow and Heat Transfer Characteristics of a Ventilated Brake Disc Connected to a Wheel2018-01-187810/5/2018
The role of a brake disc is to convert the kinetic energy of automobiles into thermal energy caused by friction between the brake pads and disc surfaces. The braking performance of an overheated disc is decreased due to hot judder and fade. Hence, the cooling technology of a brake disc is one of the most important issues related to automobile safety. In the present study, the fluid flow and heat transfer analysis of a ventilated brake disc are conducted numerically. Some geometries of automotive parts such as bearings, hubs and wheels are considered in this study. The commercial code ANSYS CFX is used to simulate the fluid flow and the conjugate heat transfer which includes conduction and convection. To evaluate the cooling performance in each case, the results, including the flow patterns of cooling air inside the wheel and the heat transfer coefficient distribution at the disc surfaces, were investigated and compared for various disc-hub combinations.
Lee, Byung Ju, Chung, Jin Taek, Jung, Yunho, Kim, Honglae, Lee, Seungpyo, Kim, Hee Yeol
The Factors Governing Corrosion Stiction of Brake Friction Materials to a Gray Cast Iron Disc2018-01-189910/5/2018
Corrosion stiction at the contact interface between a brake friction material and a gray iron disc under the parking brake condition was investigated by evaluating the possible parameters that affect the shear force to detach the corroded interface. Using production brake friction materials, comprising non-steel and low-steel types, corrosion tests were carried out by pressing the brake pad onto the gray iron disc using a clamp at various conditions. Results showed that the shear force to detach the corroded interface tended to increase with applied pressure and corrosion time. On the other hand, porosity, acidity, and hydrophobicity of the friction material did not show a reliable correlation to the stiction force. The poor correlation of the stiction force with the friction material properties indicated that the stiction force was not determined by a single factor but governed by multiple parameters including surface contact areas and inhomogeneity of the ingredients. Microscopic observation of the detached disc surface showed adhered fragments that were removed from the friction material surface, thus shedding light on the possible estimation of the stiction force from the disc area covered by the friction materials. The scattered small areas without corrosion on the gray iron surface, which were well matched with hollow areas on the friction material surface, supported the importance of the contact area information in understanding the poor correlation between the stiction force and of the friction material properties.
Gweon, Jaehyun, Shin, Sanghee, Jang, Ho, Lee, Wangyu, Kim, Dooyeon, Lee, Keeyang
On the Wear Dependence of Low-Frequency and High-Frequency Brake Squeal2018-01-190210/5/2018
The dynamics of disc brakes, and in particular their NVH behavior, have long been the focus of research. Measurements by Rhee et al. show that brake pad wear has a significant influence on the occurrence of low and high frequency squealing [1]. It is suspected that low frequency squealing is more likely to occur when the wear difference between the inner and outer brake pads is high. If the two pads incur comparable wear, however, the prevalence of high frequency squealing increases. In order to investigate this hypothesis, this paper focuses on a simplified model of a commercial brake system. First, the friction force between the inner pad and the disc is iteratively adjusted, while the force between the outer pad and the disc is held constant. In a second step, the inner pad’s wear is iteratively increased, while the wear on the outer pad remains unaffected. With the aid of the Complex Eigenvalue Analysis (CEA), the real part of the eigenvalue is used as a quantification measure in order to investigate the dependence between wear and high and low frequency squealing.
Otto, Johannes, Ostermeyer, Georg, Rhee, Seong
A Study of the Disc Scoring Generation Principle and Reduction (II)2018-01-189110/5/2018
In the latest paper [10], we presented our work based on experiments studying MPU (Metal Pick Up) of the pad and scoring(scratching) of the disc. The main component of MPU was iron “Fe”. If the roughness of the disc was small, the content of iron “Fe” was increased and the segregation of that was decreased especially in initial condition. In this study, we extended our study based on the results by adding some additional factors such as the location of the roughness of the disc, the coefficients brake pad friction, and disc slots. We made various discs of different roughness boundaries and slots, and pads of pad friction coefficients; and conducted two types of tests for whether a slot is present or not with the other same conditions to confirm the impact of the scoring. We find and believe that our experimental data should serve a useful guideline for reducing MPU of the pad and scoring of the disc.
Jeong, ByeongUk, Ryu, Hyoung Tae, Kim, Chang Jin, Jung, Kwang Ki, Lee, Hyunkyoung
Study on Brake Disc Dynamics under Asymmetric Thermal Loads2018-01-190110/5/2018
In order to explore the generation mechanism of hot-spots on the automotive brake disc, disc tests under non-frictional thermal loads are carried out on the brake dynamometer test bench. In the tests, the oxy-acetylene flame is used as the heat source, and the distribution characteristics of the disc temperature and displacement are measured and analyzed. To confirm the mechanism of the disc deformation, a disc thermal buckling model using finite element method is established, and the key factors for the disc thermal buckling under thermal loads are further analyzed. It is found that the temperature circumferential gradient is small but the temperature radial gradient is large. The disc presents waviness deformation mode with 5th order in circumferential direction, which is the first thermal buckling mode of the disc. A method using spatial frequency spectrum has been proposed to find the critical time and load of thermal buckling. The heat source power and the rotational speed have no significant influence on the temperature and displacement circumferential and radial distribution of the disc. The temperature radial gradient is the main reason for the disc thermal buckling. The larger the temperature radial gradient is, the more easily the disc thermal buckling occurs.
Meng, Dejian, Liu, Jialin, Zhang, Jingyi, Zhang, Lijun
Performance Evaluation of Two Wheeler Brake System Using Coupled Thermo-Mechanical Simulation2018-01-189610/5/2018
Safety aspect has been a key requirement in designing braking system. However, non-safety aspect like NVH and thermal performance are gaining equal importance. High engine capacity (cc) motorcycles are prone to thermal and NVH issues as braking energies are more. Therefore, virtual validation of brake disc system by considering both dynamic and thermal load with predefined assumptions is a toughest challenge when confronted with reality boundary conditions. Thus, the paper comes in a unique way of coupling dynamic and thermal load executed between multi body dynamics (MBD) and heat transfer equation which will convey results closer to real time scenario. MBD solves motion and the dynamic influence on heat transfer is calculated using “sliding boundary condition”. A series of repeated braking condition are performed on front brake disc of motorcycle. The results obtained from the analysis shows critical temperature rise. As a consequence, disc thickness variation (DTV) due to thermal expansion are aggregated when coupled with dynamic friction. DTV will prove to be critical in concerning NVH and durability issues of brake disc. Braking conditions are numerically simulated on finite element method (FEM) using nonlinear approach and results are summarized with test data.
Sukumaran, Suraj, Kalani, Dinesh, Suryavanshi, Yogesh, Kokane, Girish, Deshpande, Moresh, Kharul, Ravindra
WHAT WE'RE DRIVING18AUTP10_0510/1/2018
Mercedes-Benz is fond of saying it cascades at least some of the S-Class' posh luxury and technology throughout its range. That's just what it has done for the fourth-generation A-Class, the nameplate that sits at the bottom of the brand's lineup. The new A-Class is heaped with cabin tech, in particular. Built on Mercedes' MFA2 front-wheel-drive platform, the A200 AMG Line version driven is well-connected, having the MBUX (Mercedes-Benz User Experience) touchscreen interface (and a touchpad), plus “Hey Mercedes” voice recognition.
Lattice Brake Disc Instability Analysis Using Transient Complex Eigenvalue Method in Terms of Excitation Applied to the Pad2018-01-00914/3/2018
This paper describes an integrated approach to the analysis of brake squeal with newly lattice brake disc design. The procedure adopted to define the lattice properties by considering the periodicity cell of lattice plates, present equations of motion and modes response of a periodic lattice disc in principal coordinates on the rotating disc which excited by distributed axial load. The non-linear contact problem is carried out based on a typical passenger car brake for vanned and lattice brake disc types as it undergoes a partial simulation of the SAE J2521 drag braking noise test. The experimental modal analysis (EMA) with impact hammer test is used to obtain the brake rotor modal properties and validated finite element Free- Free State and stability analysis. The fugitive nature of brake squeal is analyzed through the complex eigenvalue extraction technique to define dynamic instability. The likelihood of squeal noise occurrence is quantified by the definition of a single indicator derived from the system eigenvalues. The lattice type brake disc indicated lower propensity to squeal with leading to the standard deviation (SD) of the instability measurement and indicated that it is more reliable at low squeal frequencies.
KARAMOOZIAN, AMINREZA, Tan, Chin, Wang, liangmo
Fast Prediction of Disc Brake Squeal Uncertainty Based on Perturbation Concept2018-01-06774/3/2018
It is a worldwide technical difficulty to predict brake squeal uncertainty and its propagation regularity due to key parameters’ randomcity. However, as a widely used stochastic finite element method, Monte Carlo Method costs a large amount of time in calculation. It is very important to establish a fast prediction method for brake squeal uncertainty due to key parameters. In this paper, perturbation concept was applied for disc brake squeal uncertainty prediction. Firstly, a simplified, parameterized finite element model of disc brake was established for complex eigenvalues calculation. Then sensitivity analysis of real parts and frequencies of complex eigenvalues to influence parameters was carried out based on the finite element model. A series of second order perturbation polynomial formulas were fitted from the sensitivity analysis results, which were used for calculation of uncertain complex eigenvalues. The comparison between the results of Monte Carlo method and those of Perturbation method was done from the viewpoints of samples values, statistical values, probability density histograms and probability density curves. The comparison results show that the relative error of perturbation method to Monte Carlo method is less than 5%, and the calculation time is reduced to less than 5%, too. This indicates that the established uncertainty prediction method based on perturbation ideal is a satisfied object oriented brake squeal uncertainty method, which has higher precision and higher efficiency.
Li, Wenbo, Zhang, Lijun, Meng, Dejian
Toyota rethinks THE FLAGSHIP17AUTP11_0211/1/2017
The 2018 Lexus LS moves to twin-turbo V6 power and piles on the takumi. Toyota has engineered a complete road-to-roof redo of its flagship Lexus LS sedan, dropping the V8 engine in favor of a twin-turbo V6, adding Aisin's new 10-speed planetary automatic and retaining a hybrid-electric powertrain option-and that's just the beginning. The 2018 model marks the fifth generation of the luxury sedan that rocked the luxury-sedan establishment almost 30 years ago. While the LS has represented less than 2% of the brand's U.S. sales in recent years, its significance to Toyota exceeds its sheer numbers. Chief Engineer Toshio Asahi and his team began work on the new LS500 and hybrid LS500h in late 2011. One key goal was to attract a younger buyer with what Asahi calls “Brave Design,” picking up the Lexus family ‘spindle’ grille theme and developing a longer, more muscular exterior form. Lowering the hood by 1.2 in (30.5 mm), the decklid by 1.6 in (40.6 mm) and dropping the roof 0.6 in (15 mm) versus the 2017 LS helps the new version look more ground-hugging as well.
Sessions, Ron
Finite Element Analysis of a Brake Disc under Constant Mechanical Loading2017-01-24909/17/2017
A brake disc is one of the most critical components in modern vehicle’s brake systems; hence, thorough validation of its performances in the development process by simulations, rig and vehicle tests is essential. In this paper, a disc brake system under a constant braking torque is analyzed using finite element method, and the stress and strain in a rotating ventilated brake disc employed are studied comprehensively. From detailed examination of the stress distribution and the cyclic stress history, it is found that the maximum stress in the rotating brake disc under the constant mechanical loading only occurs at some specified locations; and the stress history is multiaxial and non-proportional. These findings will help, as guidelines, to develop suitable evaluation tools for the strength and the fatigue of the brake discs; to setup proper laboratory test procedures and equipment; and to design strong and durable brake discs. Furthermore, the stress and strain under various amplitudes of loading are analyzed, and a linear relationship between the maximum stress/strain and the amplitude of loading is established. Finally, two simplified finite element modeling methods to shorten the analysis time are evaluated.
Yang, Qianjin, Zhang, Baozhi, Ding, Kangrong, Song, Liqiang
Influences of Initial DTV on Thermomechnical Coupling in Disc Brake System2017-01-24929/17/2017
In this paper, the initial disc thickness variation (DTV) of a ventilated disc in automotive brake system is modeled as sinusoidal function of the second order. The transient thermomechanical coupling properties of the brake system is simulated using finite element (FE) modeling. The system models and results were verified by a thermomechanical coupling test of a disc brake conducted on a brake dynamometer. By using varied evaluation indexes such as the temperature distribution, the normal stress and the elastic deformation of disc surfaces, the influences of the initial DTV and its direction as well as its amplitude on the thermomechanical coupling characteristics were analyzed. The simulation results show that the distribution of temperature and the normal stress in circumferential direction exhibit the same sinusoidal function of the second order as the modeled initial DTV property, which is different from the thermomechanical coupling characteristics caused by disc surface initial run-out (LRO). Whereas the thermomechnical coupling property of the disc in circumferential direction exhibit the same sinusoidal function of the second order as that of the initial DTV, the distribution of the temperature, the normal stress and the elastic deformation in radial direction are found to be uniform. The changes in the magnitude of initial DTV are found to have insignificant effects on the changes in the overall thermomechnical coupling property. However, the circumferential gradients of the temperature, the normal stress, and the maximum disc distortion increase linearly with the increase of the magnitude of the initial DTV. The radial gradients of these quantities are not linear proportional to the magnitude of the initial DTV.
Meng, Dejian, Wang, Ziyi, Zhang, Lijun, Yu, Zhuoping
Evaluation of an Energy Dissipation Mechanism by Friction for Brake Shims2017-01-24879/17/2017
Brake squeal is uncomfortable noise that occurs while braking. It is an important issue for automobile quality to prevent brake products from squealing. Brake shims are widely used to reduce squeal occurrence rate. In particular, laminated shims can effectively suppress squeal via the viscoelastic damping of an adhesive layer. However, there are cases where the damping performance at low temperature and the durability performance at high temperature deteriorate. In that regard, we thought of applying frictional damping to shims instead of relying on a temperature-sensitive adhesive layer. To study the application of frictional damping for shims, it is necessary to clarify the characteristics thereof. In order to quantify the damping performance of shims, loss factor has been generally measured with a bending mode tester. However, the influence of friction cannot be evaluated because it is measured under pressure-free condition. Therefore, we developed a device that can measure damping of shims under pressure and evaluated the basic characteristics of frictional damping. To quantify the frictional damping, the developed method calculates the total energy loss from the area of hysteresis in a cycle of force-displacement oscillation. In addition, the influence of friction on damping is analyzed from the shape of the hysteresis loop. In this paper, we report the results of comparing laminated shims against textile fabrics, which served as samples for evaluating frictional damping. As a result of measurement by the developed method, it was confirmed that the amplitude and pressure dependency of the laminated shim was small, while on the other hand, the textile fabric has characteristics whereby damping increases with large amplitude and low pressure.
Kanehira, Yasuyuki, Aoki, Yusuke, Nishizawa, Yukio
A Study of the Disc Scoring Generation Principle and Reduction2017-01-25019/17/2017
Owing to the enhanced performance of engines these days, more heat should be dissipated in the braking system. Success of doing this properly causes more heat to the disc in the brake system which results in the deformation or scratches on the surface of it and a reduction in the appearance of the product. A study for detailed factors to aggravate this was done as a solution to prevent these from happening. In this paper, we present our work based on experiments to study MPU (Metal Pick Up) of the pad and the scoring(scratching) of the disc. MPU of which the main component is “Fe”, is formed through the process of fusing the separated materials from the disc by friction with the pad, and by local heat generation to the pad. [1,2,3,4,5] The occurrence of MPU and the possibility of the disc scoring resulting from this were studied by noting “Fe” which was transferred to the surface of the pad to different extent and degree of segregation according to the roughness of the disc. For verification purposes, the vehicle and bench tests were conducted.
Jeong, ByeongUk, Ryu, Hyong Tae, Jung, Kwang Ki, Kim, Chang Jin
In-Plane and Out-of-Plane Vibrations of Brake Linings on the Rotor2017-01-25309/17/2017
The dynamics and, in particular, the NVH phenomena in brakes are still in the focus of research. Recent investigations of for example Rhee et al. show two principal vibrational forms of the linings on the rotor [1]. The first form is characterized by vibrations where both linings are in-phase (minimal differential torque between the inner pad and the outer pad). This produces in-plane vibrations of the rotor and results in high-frequency squealing events in the brake. The second form is an antiphase vibration of the brake linings with respect to each other (increased differential torque between the inner pad and the outer pad). This produce directly out-of-plane vibrational modes of the disc, which results in lower-frequency caliper and rotor oscillations. One hypothesis is that different wear densities of the linings essentially characterize the two vibrational modes. The wear behavior is not taken into consideration of this paper as it will be discussed in further publications. This paper deals with a low dimensional dynamical system and examines the vibrations, and analyzes essential influencing parameters on the different vibrational events.
Ostermeyer, Georg Peter, Otto, Johannes, Rhee, Seong Kwan
Studies on Friction Mechanism of NAO Brake-Pads Containing Potassium Titanate Powder as a Theme Ingredient05-11-01-00069/17/2017
Potassium titanate (KT) fibers/whiskers are used as a functional filler for partial replacement of asbestos in NAO friction materials (FMs). Based on little information reported in open literature; its exact role is not well defined since some papers claim it as the booster for resistance to fade (FR), or wear (WR) and sometimes as damper for friction fluctuations. Interestingly, KT fibers and whiskers (but not powder) are proved as carcinogens by the International Agency for Research on Cancer (IARC). However, hardly any efforts are reported on exploration of influence of KT powder and its optimum amount in NAO FMs (realistic composites) in the literature. Hence a series of five realistic multi-ingredient compositions in the form of brake-pads with similar parent composition but varying in the content of KT powder from 0 to 15 wt% (in the steps of 3) were developed. These composites were characterized for physical, mechanical, chemical and tribological performance. Composites were tribo-evaluated on reduced scale prototype (RSP) as well as on full scale brake inertia dynamometer by following ECE R90 and Japanese Automobile Standards (JASO C 406) testing procedure respectively. Optimum content of KT powder was evaluated by multiple objective optimization on the basis of ratio analysis’ (MOORA) method on the basis of several performance parameters such as performance µ, fade µ, recovery µ, % fade ratio, % recovery ratio, wear resistance etc. The friction and wear mechanisms were studies in details based on worn surface analysis. It was concluded that increase in KT amount played important role in improving wear and fade performance. With increase in amount of KT powder, most of the properties improved. Overall 12% KT powder shows best performance.
Mahale, Vishal, Bijwe, Jayashree, Sinha, Sujeet
Estimation of Brake Friction Coefficient for Blending Function of Base Braking Control2017-01-25209/17/2017
The brake architecture of hybrid and full electric vehicle includes the distinctive function of brake blending. Known approaches draw upon the maximum energy recuperation strategy and neglect the operation mode of friction brakes. Within this framework, an efficient control of the blending functions is demanded to compensate external disturbances induced by unpredictable variations of the pad disc friction coefficient. In addition, the control demand distribution between the conventional frictional brake system and the electric motors can incur failures that compromise the frictional braking performance and safety. However, deviation of friction coefficient value given in controller from actual one can induce undesirable deterioration of brake control functions. The main objective of the presented study is to propose a method to compensate disturbances induced by variations of brake linings friction coefficient through modifications of the brake torque demand for the enhancement of both brake performance and active safety. The achievement of a compensation mechanism requires the estimation of relevant vehicle states. Hereunto, a novel technique based on a linear Kalman observer is proposed for the online estimation of the brake friction coefficient by relying upon the wheel speed sensors and inertia measurement unit (IMU). Such a tool enables a more efficient use of the frictional brakes aimed at minimizing losses of friction coefficient by keeping them in the optimal operational conditions. A simulation analysis will be carried out using the commercial vehicle dynamics simulation software IPG CarMaker to test the functionality of the developed estimator in the real-time mode. Experimental results from brake dynamometric test rig will be considered in the vehicle dynamics simulation software to reproduce the real behaviour of brake linings friction coefficient. The resulting improvements in brake control functions will be analysed against longitudinal base braking cases involving blending functions also in presence of failure of the electric motors.
Ricciardi, Vincenzo, Savitski, Dzmitry, Augsburg, Klaus, Ivanov, Valentin
Integrated Brake Squeal with Induced Thermal Stress Analysis2017-01-19006/5/2017
Brake squeal is an instability issue with many parameters. This study attempts to assess the effect of thermal load on brake squeal behavior through finite element computation. The research can be divided into two parts. The first step is to analyze the thermal conditions of a brake assembly based on ANSYS Fluent. Modeling of transient temperature and thermal-structural analysis are then used in coupled thermal-mechanical analysis using complex eigenvalue methods in ANSYS Mechanical to determine the deformation and the stress established in both the disk and the pad. Thus, the influence of thermal load may be observed when using finite element methods for prediction of brake squeal propensity. A detailed finite element model of a commercial brake disc was developed and verified by experimental modal analysis and structure free-free modal analysis. This analysis includes prediction of disc thermal deformation and a complex eigenvalue analysis to evaluate its effect on squeal propensity. The finite element model should be parameterized in order to investigate the effect of variability. The process includes geometry simplifications to reduce calculation time, allowing for more configurations to be computed. Several parametric studies were conducted to assess the effects of the friction coefficient, of the rotating direction and velocity, Young’s modulus, etc.
Yang, Leiaixin, Li, Yinong, Ding, Peiran, Zamankhan, Parsa, Cherng, John G.
Wear, Friction and NVH Characterization Using a Laboratory-Scale Tribometer2017-36-00035/24/2017
The current study presents some testing procedures which have been designed for friction and noise measurements of brake friction materials using a laboratory-scale tribometer. The uncertainties (errors) and precision of the measurements are also described in this paper. Some case studies related to friction, wear and noise related issues in brake friction materials were chosen to show the respective testing procedures. Through the error study, it was shown that the uncertainties of the lab. test bench are mainly associated with 3 variables: torque, force and sliding radius. The combined uncertainty of the friction measurements is less than or equal to ±1%, considering the typical operating range of the machine. The possibility of using two samples from a single brake pad also contributes to the reliability of the machine test and procedures. Finally, the laboratory-scale tribometer and testing procedures discussed in the present paper proved to be adequate to characterize friction, wear and Noise, Vibration and Harshness (NVH) related issues in brake friction materials.
Pavlak, Rafael Paini, Neis, Patric Daniel, Poletto, Jean Carlos, de Barros, Liu Yesukai, Ferreira, Ney Francisco
Residual Brake Torque Measurement on Dynamometer in Terms of Wheel Load and Side Forces2017-36-00165/24/2017
Residual brake torque (RBT) is generated in disc brakes as a result of contact between brake disc and brake pads when the braking pressure is not applied. Among the negative implications of RBT are, notably, dispensable additional fuel consumption as well as increased pad (taper) wear. Several properties of the brake system have a direct influence on the level of residual torque [1]. A major effect is connected to the caliper properties determining the clearance gap. This is characterized by the default air gap between pads and disc and its distribution regarding vehicle inner and outer sides (piston and fist sides for floating type calipers). Initial air gap is mainly influenced by the sealing grove design (between piston and housing, where the sealing ring is positioned). The retraction of the piston due to the sealing ring, also called rollback, mainly depends on the load case (e.g. applied pressure and temperature). Insufficient air gap will lead to residual clamping forces between pads and rotor and thus the friction coefficient itself influences residual brake torque directly. In addition, there are also parameters which can exert influence on the residual brake torque, which are not caliper, but primarily rotor-related. These include axial thermal deformation, thermal coning effects, lateral runout (LRO) of the rotor due to geometrical tolerances and also LRO excited by tensioning the rotor to the wheel hub. These influences on caliper drag are typically well known and understood at least qualitatively. To accomplish customer’s requirements according to RBT, the calipers are extensively tested (e.g. NEDC/WLTP, coast down, ATE) in different test procedures on dynamometers. Some test specifications contain ambitious requirements on the intended drag torque (e.g. less than 0.1 Nm). In contrast to the requirements, other possible influencing parameters, e.g. disc deflection, caused by vehicle dynamics, is currently not included in any RBT-test on dynamometer. During e.g. curve driving, the lateral forces are generated between tire and road and can also be transferred into the rim/rotor/hub/bearing contact at the knuckle. Additionally this is overlain by the wheel load. It must be assumed that the side forces and wheel load affect the deflection of the disc. Thus, this may also influence residual brake torque. This paper shows Continental’s setup for application of wheel load and side forces on dynamometer. Based on previous results from vehicle test, the disc deflection during dynamic driving is characterized and the wheel load setup was enhanced to apply side forces. Different positions of side force and wheel load induction are compared. Furthermore the setup is used to identify the influence of dynamic disc deflection on caliper drag. This is done with an exemplarily floating-type caliper (FN). Dedicated measurements illustrate the influence of left and right curve driving on the level of RBT.
Haag, Mathias, Reich, Achim, Sardá, Angelo, Wurmlinger-Georg, Michael, Semsch, Martin, Borim, Leonardo Felix
Modeling, Simulation and Experimental Analysis of Brake Pedal Feel for Passenger Car2017-01-13713/28/2017
Brake pedal feel plays an important role in the driver's comprehensive subjective feeling when braking, which directly affects the active safety and riding comfort of passenger car. A systematical mathematical model of the vehicle brake system is built in according with the structure and system characteristics of hydraulic servo brake system. A complete hydraulic servo brake system simulation model composed of brake pedal, vacuum booster, brake master cylinder, brake pipe, brake wheel cylinders, brake calipers is established in AMESim. The effects of rubber reaction plate stiffness, rubber valve opening, brake master cylinder piston, brake caliper, brake pipe deformation and friction liner deformation on brake pedal feel are considered in this model. The accuracy of this model is verified by real road vehicle tests under static and dynamic two different conditions. The influence of six structural parameters of vacuum booster, brake pipe and brake caliper on brake pedal feel are analyzed in detail. Finally, based on the evaluation system of BFI, the influence degree of different factors in different levels on the brake pedal feel are discussed through the orthogonal experiment design. The optimal scheme of brake pedal feel is put forward based on the sensitivity of various factors and validated by experiment. This study can serve as important reference for obtaining the best brake pedal feel, and also provides the theoretical basis for pedal simulator design and braking intention recognition in Brake-by-wire.
Pan, Hao, Guo, Xuexun, Pei, Xiaofei, Dong, Xingzhi
A CFD Investigation of Aerodynamic Effects of Wheel Center Geometry on Brake Cooling2017-01-15373/28/2017
Improving brake cooling has commanded substantial research in the automotive sector, as safety remains paramount in vehicles of which brakes are a crucial component. To prevent problems like brake fade and brake judder, heat dissipation should be maximized from the brakes to limit increasing temperatures. This research is a CFD investigation into the impact of existing wheel center designs on brake cooling through increased cross flow through the wheel. The new study brings together the complete wheel and disc geometries in a single CFD study and directly measures the effect on brake cooling, by implementing more accurately modeled boundary conditions like moving ground to replicate real conditions correctly. It also quantifies the improvement in the cooling rate of the brake disc with a change in wheel design, unlike previous studies. The axial flow discharge was found to be increased to 0.47 m3/min for the suggested design in comparison to 0.04 m3/min for traditional design. The increased axial flow enhances the velocity of flow over the brake disc leading to quicker dissipation of heat from turbulent eddies in the outer boundary layer. The brake disc exhibited approximately 33%-50% higher Heat Transfer Coefficient with the change in wheel center geometry. It is suggested that the implementation of a similar design is highly beneficial for improved brake cooling, and could bring a positive impact on the exploitation of wheel designs for the same, which currently are more tuned towards aesthetics than performance.
Bhardwaj, Ananya
Development of a High Fidelity CAE Model for Predicting Brake System Temperatures2017-01-01453/28/2017
In order to specify a brake system that will have robust performance over the entire range of expected vehicle drive cycles it is vital that it has sufficient thermal inertia and dissipation to ensure that component temperatures are kept within acceptable limits. This paper presents a high fidelity CAE (computer aided engineering) technique for predicting the temperature of the front brake and the surrounding suspension components whilst installed on vehicle. To define the boundary conditions the process utilizes a coupled unsteady CFD (computational fluid dynamics) and thermal solver to accurately predict the convective heat transfer coefficients across a range of vehicle speeds. A 1-D model is used to predict the brake energy inputs as well as the vehicle speed-time curves during the drive cycle based on key vehicle parameters including wide-open-throttle performance, drive train losses, rolling resistance, aerodynamic drag etc. The convective heat transfer coefficients are interpolated based on the vehicle speed curve to generate the time varying convective heat transfer coefficients for each component. These boundary conditions are then applied to a transient thermal model consisting of the brake and suspension system. To demonstrate the advantage of using a fully transient method over a steady state cooling and 1-D modeling approach a case study has been performed examining the relative performance of single piece conventional iron rotors and two piece discs fitted to the Jaguar XE saloon car. The results are validated against vehicle test data, showing a much stronger correlation between the predicted and experimental brake disc temperatures for the full transient model compared to the steady state cooling
Palmer, Edward, Jansen, Wilko
Critical Assessment of Some Popular Scale-Resolving Turbulence Models for Vehicle Aerodynamics2017-01-15323/28/2017
Some widely-used scale-resolving turbulence models are comparatively assessed in simulating the aerodynamic behavior of a full-scale AUDI-A1 car configuration. The presently considered hybrid RANS/LES (RANS – Reynolds-Averaged Navier-Stokes; LES – Large-Eddy Simulation) models include the well-known DDES (Delayed Detached-Eddy Simulation) scheme and two further variable-resolution formulations denoted by PANS (Partially-Averaged Navier-Stokes; Basara, 2011) and VLES (Very LES; Chang et al., 2014). Whereas the DDES method represents the originally proposed formulation based on the one-equation Spalart-Almaras model (Spalart et al. 2006), whose RANS/LES interface position is directly correlated to the underlying grid resolution, the other two models represent ‘true’ seamless formulations, providing a smooth transition from Unsteady RANS to LES in terms of a dynamic “resolution parameter” variation. The latter parameter is evaluated by contrasting the length scale related to the residual turbulence of both PANS and VLES methods to the grid spacing. The dynamics of residual motion in both methods is modelled by a four equation model (Hanjalic et al., 2004). All computations are performed by the OpenFOAM code. The PANS and VLES formulations, in conjunction with the ‘hybrid wall functions’ used for the wall treatment, were implemented by the authors. The car configuration considered accounts for mirrors, detailed underbody accommodating the exhaust system, as well as the rotating wheels including brake discs and rim details. The solution domain representing a regular hexahedron was meshed by two grids consisting approximately of 31 and 62 million cells in total. The results representation includes detailed time-dependent mean flow and turbulence fields, surface pressure distribution and the resulting drag and lift force coefficients. The results’ analysis is performed by discussing the models’ predictive capabilities along with the available experimental results.
Jakirlic, Suad, Kutej, Lukas, Unterlechner, Peter, Tropea, Cameron
Experimental and Numerical Thermal Analysis of Brake Disks of a Formula SAE Vehicle2016-36-045710/25/2016
Through a computing transient thermal analysis, the team evaluated the quality of the material and its resistance to thermal fatigue by a comparative method. With the steel used in 1020 failed in 2014, for the team Formula UFMG, the 1020 steel, 1045, 1070 and stainless steel 304 were compared, where the stainless steel was the parameter of better resistance to thermal cracking. The main calculated parameters were subjected to empiric validations and the best material has been applied and used in the 2015 season. The use of the disks in a competition and in a battery of tests superior to 2014, permitted the evaluation of the final result of applying the material.
Veloso, Weber Ferreira, Garcia, Marcela Rodrigues Machado, Firmino, Sabrina Glicéria, Queiroga Gazaniga de Assis, Juliana, Palhares de Faria, Diego
Applying the Dynamic Inertia Measurement Method to Full-Scale Aerospace VehiclesTBMG-2549610/1/2016
Researchers at NASA’s Armstrong Flight Research Center have been interested in using the Dynamic Inertia Measurement (DIM) method on full-scale aerospace test vehicles, given its advantages over traditional methods for determining the mass properties of such vehicles. Developed at the University of Cincinnati, the DIM method uses a ground vibration test setup to determine mass properties using data from frequency-response functions. The method has been successfully tested on a number of small-scale test articles — including automobile brake rotors, steel blocks, and custom fixtures — but until now, has had limited success being tested in larger applications. Armstrong’s recent efforts, in conjunction with ground vibration tests, represent a step forward in applying the DIM method successfully to full-scale aerospace vehicles.
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