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The FISITA Library is the central repository for all technical contributions from FISITA events and member-led output papers. Employees of FISITA Corporate Members get free access to the content here. People registered for FISITA events are provided with a special password in their confirmation email to access event-specific content here, for which abstracts can be browsed freely. Members of FISITA automotive engineering societies get discounted access. Find out about access and how anyone can register for instant access here.

The library includes all of the FISITA output papers plus content from the EuroBrake 2012-2021 events and the FISITA Intelligent Safety Conference 2020-2021, FISITA Web Congress, and FISITA World Mobility Summit. Use the drop-down list box on the right below to browse content from a particular event or type keywords into the search box below.

 

FISITA has over 10,000 papers in it content repository. Much of this is currently being migrated from go.fisita.com/store to this location. As content is added this page will be updated.

Welcome to the FISITA Library

EB2012-ABT-13

Paper

Shi, Leilei, Li, Qing, Kim, Hunmo* - Sungkyunkwan University; Park, Manbok - Mando Co.

Detail

In this paper, the Hybrid Automatic Repeat Request (HARQ) scheme for Brake-by-Wire (BBW) system is presented. Recently, the use of electronic components is growing, so error signals will be encountered caused by Electromagnetic Interference (EMI).These error signals will cause system failures of BBW systems. To solve these problems in the BBW system, we design a HARQ scheme which is a combination of Forward Error Correction (FEC) scheme and Automatic Repeat Request (ARQ) scheme. FEC scheme uses Reed-Solomon (R-S) code to correct random errors and burst errors and ARQ scheme uses Cyclic Redundancy Check (CRC) code to detect errors in the systems. In this paper, the performance of FEC scheme, ARQ scheme and HARQ scheme is presented through the experiment and we see clearly how the fault tolerant logic for BBW system works.

EuroBrake 2012

Advanced Brake Technologies (ABT)

EB2012-ABT-16

Paper

Boretti, Alberto - University of Ballarat

Detail

Mechanical kinetic energy recovery systems have been proposed so far as a driveline component made up of a flywheel, a clutch and a continuously variable transmission connected to the driving wheels and designed for long time and high energy storage and high power charge and discharge rate. In the approach proposed here, there are actually two small KERS, one acting individually on each wheel, made up of just a clutch, a CVT and the flywheel. In this system, braking on one of the two rear wheels otherwise not motored is obtained by engaging the CVT through the clutch. Then, the wheel reduces its speed while the flywheel accelerates. Powering of one of the two rear wheels is then obtained when needed by engaging again the CVT through the clutch. Then, the wheel increases its speed while the flywheel decelerates. When the clutch is disconnected, flywheel and rear wheel are decoupled. This configuration is aimed to a further reduce the complexity and further reduce the costs of the KERS. This KERS has same potentials to reduce the fuel consumption of the traditional driveline based KERS. The system also offers the benefits to produce same accelerations of a four wheel drive car powered by a larger engine with a two wheel drive arrangement.

EuroBrake 2012

Advanced Brake Technologies (ABT)

EB2012-ABT-21

Paper

Andersen, Olaf, Meinert, Jens, Studnitzky, Thomas, Stephani, Günter* - Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research
Kaina, Steffen, Kieback, Bernd - TU Dresden
Saame, Christoph, Münchhoff, Jan - AUDI AG
Mayer, Ralph - Daimler AG

Detail

A new concept for the improvement of cast vented brake disks has been developed which re-lies on the interesting properties of a new type of constructed material: 3D wire structures. This type of material shows a comparably high specific compressive modulus and strength combined with a large internal surface area which is completely accessible by external fluid flow. The high strength of the 3D wire structures is obtained by brazing of the wire joints. It is conceivable to replace the cast internal venting structure of a disk brake by 3D wire structures and hence improve the venting of the rotors. At the same time, considerable weight savings can be expected as a cast fin structure usually occupies about 50 vol% of the space between the rotors, whereas a 3D wire structure occupies only 10 to 20 vol% of the available space. Moreover, the narrow spacing of the 3D wire structure may account for a very homogeneous heat transfer, thus avoiding hot spots and improving the level of comfort. This paper discusses relevant mechanical and thermal properties of 3D wire structures with regard to their applica-tion in vented disk brakes.

EuroBrake 2012

Advanced Brake Technologies (ABT)

EB2012-ABT-22

Paper

Putz*, Michael, Faul, Bernhard, Wunsch, Christian, Morgan, John E. - Vienna Engineering

Detail

The VE Brake is an electro-mechanical floating caliper disc brake (EMB) that uses a novel mechanism (effectively a mini crankshaft) with lowest possible friction in actuation, non linearity and a designable self amplification for very low actuation power, e.g. 100 W for mid size cars. It can cooperate for best regenerative braking and it can be designed to have no residual drag losses, both highly actual topics for electric and hybrid vehicles.


Earlier versions were intensely tested on a lab dynamometer. Latest road going versions are with fully integrated actuators are being developed for mid size SUV class vehicles. The new challenge was to fully protect the actuators (small electro motors with gears) and to integrate the actuators into the mechanical parts of the brake so that the brake fits into the given front axle, suspension and rim of standard SUV components maintaining the full steering angle, spring stroke and brake location without modifications. Both, a normal single channel design with one actuator for clamping forces and one for wear adjustment, and a two channel design with two clamping-force actuators and two wear adjustment actuators are presented.


This VE brake can be used as well in single channel design (saving costs) as in two-channel-design (for very high reliability purpose with few brakes, e.g. with only two brakes on motorcycles, city cars or even aircraft). In the conference paper it is shown how to solve the space issues for the single and the two channel design and how to adequately protect the complete actuation against impacts, dirt and salt water. Of course the wear adjustment can be done mechanically ( as with drum brakes). This version does it electrically to offer full flexibility of electronic control. It is also shown how the parameters of the brake could (if intended) even be changed "on the ride" by selecting the involved range of the eccentric part that changes transmission ratio, non-linearity and self amplification. Although these parameters have been unchanged on dynamometer tests the advantages of making them adjustable are shown, resulting in a further reduction in actuation power and size of mechanical parts.

EuroBrake 2012

Advanced Brake Technologies (ABT)

EB2012-BC-02

Paper

Deichmann, Tobias*, Lathwesen, Holger - Sheet Cast Technologies GmbH

Detail

The SHEET CAST Technologies GmbH succeeded with the first SHEET CAST Disc in combining the weight and performance advantages of multi-part disc with simple and cost effective manufacturability. By the integration of radial elastic steel inlays into the sand core, which is inserted into the sand mold, a unique and serial production lightweight composite brake disc was developed. The production costs can be halved in comparison to others on shift-based composite brake discs. The weight advantage of the SC-Disc is surpassing all know technologies.


The newest evolution is designed for e-mobility based on a wheel hub motor. The package is perfectly aligned to external rotor electric motors. This solution is still in the patent application and celebrates its world premiere at EuroBrake in April 2012.

EuroBrake 2012

Braking Components & Systems (BC)

EB2012-BC-07

Paper

Curry, Eddie - MIRA Limited

Detail

As part of the low carbon vehicle technology project, a study was undertaken of the issues associated with regenerative braking control. There are a number of issues that need to be addressed whilst designing these systems, including compliance with legislation, providing good pedal feel and driver confidence, as well as maximising energy recovery.


Whilst many vehicle manufacturers and their suppliers are spending considerable time and resources on investigating regenerative braking and control systems, there is little information in the public domain about how well these systems work in practice, especially with respect to driver confidence and pedal feel.


This paper seeks to contribute to the understanding of these systems and their effectiveness by summarising the legal constraints on these systems and the implications on their design and extensive subjective and objective brake tests. The paper will summarise areas where these systems work well and also where there are shortcomings, as well as highlighting some of the strategic decisions that need to be made when developing the control strategies.

EuroBrake 2012

Braking Components & Systems (BC)

EB2012-FM-01

Paper

Österle, Werner*, Deutsch, Cornelius, Rooch, Heidi, Dörfel, Ilona - BAM Federal Institute for Materials Research and Testing

Detail

Brake discs on the basis of carbon fibre reinforced SiC-ceramics are appreciated as a light weight high performance alternative to conventional cast iron brake discs. Although efforts are going on to develop ceramic pads of a similar material but with additions of friction modifiers, comfort requirements cannot be reached with a full ceramic system and therefore commercial solutions still are based on polymer matrix composites (PMCs) and in some rare cases on sinter metallic (SM) friction materials.


In previous studies with conventional automotive brakes an iron oxide based friction film on the surfaces of pads and discs was observed. This seemed to be plausible since iron is the major element of the cast iron disc and furthermore is contained in most pad formulations in the form of steel fibres. Therefore it was of great scientific interest to determine the relevance and composition of friction films on ceramic brake discs which do not contain any iron.


Three brake systems (2 with PMC and 1 with SM pads) were investigated in this study. For proprietary reasons the companies did not communicate their formulation recipes, but they agreed to publish the results of microstructural and microanalytical investigations in a generalized form. Anyway, all three pad formulations contained iron either in the form of steel fibres or as powder particles. Friction films were characterized by Light optical Microscopy (LM) and surface analytical methods (SXFA, SEM/EDS) and by cross-sectional methods (FIB, TEM, STEM/EDS, EFTEM).


Surprisingly, the basic structure of friction films was similar for all three systems and again the main constituent was iron oxide of type magnetite mixed with other pad constituents. This result clearly shows that tribooxidation of the ferrous pad constituents has occurred, and that the wear particles are able to form a film which is screening both first bodies. Significant differences between the three systems were observed in respect to film thickness and coverage of the disc surface with the third body film. Whereas the disc of the SM-system was covered almost completely with a ferrous film, only fragments of a film, or deposition of wear debris in a network of cracks were observed for the two PMC-systems, respectively. It seems that the surface structure of the C-SiC disc, i.e. carbon fibre content and number and arrangement of cracks plays an important role in respect to the formation of stable third body layers. Furthermore, incorporation of additional soft and hard constituents from the pad formulation is necessary to stabilize the friction properties of the iron oxide film. Compared to conventional brakes the ratio of additives to iron oxide in the third body is higher for the ceramic discs.

EuroBrake 2012

Friction Materials (FM)

EB2012-FM-06

Paper

Langhof, Nico*, Bettina, Greuel, Christian, Hilpert, Martin, Kozub, Alexander, Voigt, Rebecca, Krenkel, Walter, Alber-Laukant - University of Bayreuth

Detail

The frictional properties of two different C-fiber reinforced ceramic composites were investigated. These composites, e.g. C/SiC were manufactured by applying the liquid silicon infiltration process (LSI). C/SiC means C-fiber reinforcement within a SiCmatrix and residual silicon. To study the frictional properties of C/SiC brake pads (material A) and Si-free C/SiC brake pads (material B) decent tests with defined conditions were realized. On a dynamometer test rig braking pressures between 0.54 N/mm² and 2.44 N/mm² and rotating speeds of a commercial C/SiC ceramic brake disc between 5.5 m/s (300 rpm) and 42.6 m/s (2262 rpm) were applied. Due to the observation of the microstructure and the measurements of the coefficient of friction (COF = μ), the wear rates, the surface roughness and finally the determining friction mechanisms could be detected. Adhesive, abrasive, fatigue wear and oxidative wear occur, partially simultaneously. In general, the COF decreases with increasing speed and pressure. At low braking pressure (0.54 N/mm²) and moderate speeds (17.4 m/s) no adhesive wear due to free silicon is detectable. Examinations of the surfaces of brake pads (C/SiC material) and brake disc after increasing the pressure and/or the speed show, that the residual silicon causes extraordinary high wear rates at 42.6 m/s by combining adhesion and abrasion of free-Si and SiC. Wide distributed roughness peaks on the surface of the brake disc were observed. Each of them consists of a silicon matrix with embedded hard SiC particles. As a result, significantly deep grooves on the pads surface can be detected at moderate speed (17.4 m/s) and finally at higher speeds C/SiC brake pads (material A) were rapidly abraded. By removing of the residual silicon, the porosity increases and the adhesive wear can be avoided. Therefore, no asperities were formed, the real contact area for friction increases compared to the C/SiC pads and the wear rate decreases with increasing speed and increases with increasing the pressure. Nevertheless, no stable sliding friction independent on the conditions is observable, due to the lack of a friction layer.

EuroBrake 2012

Friction Materials (FM)

EB2012-FM-07

Paper

Andersen, Torben Paarup*, Fischer, Gert, Tønnesen, Jesper, Larsen, Jørgen - Scandinavian Brake Systems A/S

Detail

The aim of the investigations was to reduce wear of brake pad as well as of brake disc. The brake pad to be investigated was a commercial sintered brake pad produced at Scandinavian Brake Systems A/S (SBS) and composed of more than 10 different materials. Even excluding process parameters the number of experimental variables was quite large. It was therefore decided to use design of experiments (DOE) as a systematic approach to reduce wear.


The team discussed which parameters and materials that could be of most importance to wear and a DOE was selected. It was decided to lock process parameters and focus on materials among these the amount of hard metal which turned out to be a significant factor for both disc and pad wear.


Based on the results of the first DOE, a second DOE was initiated in order to expand the model of the first DOE. The second DOE was a fractional design as before and investigated 4 of the factors from the first DOE and including a center point. The optimal setting for hard metal from the first DOE was selected as center point to check if the setting actually was the best.


Based on the results of the second DOE, a recipe was made and pads manufactured. The reduced wear of the improved pad is reported and compared with the original pads.

EuroBrake 2012

Friction Materials (FM)

EB2012-FM-09

Paper

Matějka, Vlastimil*, Kukutschová, Jana, Vaculík, Miroslav - VSB - Technical University Ostrava
Wang, Hui, Qi, Shicheng, Lu, Yafei - Beijing University of Chemical Technology
Matějková, Petra - VSB - Technical University Ostrava

Detail

The nowadays trends reflected in growing demands on the eco-friendly character of materials utilized for manufacturing of industrial products has not avoided the automotive industry. Automotive brake linings represent part which is constantly abraded during their service and wear debris released during the braking directly enter environment. This fact evoked the interest about the composition of the friction composites since the strong negative health effect was observed for asbestos, which instead of many other applications served as an excellent filler for friction composites for brake linings. Since the utilization of the asbestos has been banned the systematic search for suitable candidate of filler for brake linings has resulted in research dealing with utilization of organic fibers as the filamentous fillers. Despite the fact, that the negative effect of the wear debris releasing during friction of NAO composites containing aramide fibers has not been verified yet, the hazardous compounds originating during their manufacture evoked the efforts for utilization of natural fibers.


Five sets of NAO friction composites with growing content of jute fibers and proportionally decreased content of other 8 components (wollastonite, basalt fibers, zircon, baryte, vermiculite, graphite, phenoloic resin and cardanol based benzoxazine) were prepared in laboratory scale and their functional properties were tested using friction tester in the temperature range of 100 - 350 °C. The results showed that the values of the friction coefficient were slightly lower in comparison to reference composite (without jute fibers). The dependency of friction coefficient on the temperature revealed that the fade phenomenon at the samples containing jute fibers occurs at temperature 250°C, what is the same temperature as was observed for the reference sample. The specific wear rate determined for samples with jute fibers was lower at all of the tested temperatures in comparison to the reference sample. The obtained results show the jute fibers as a suitable filamentous component for friction composite designed for automotive brake linings.

EuroBrake 2012

Friction Materials (FM)

EB2012-FM-10

Paper

Allrath, Peter*, Bruggen, Ivan, Grabiec, Tomasz, 1Grochowicz, Jaroslaw - Ford; Albrecht, Gerald, Hodges, Tim, Paul, Hans Günther, Rudd, Adrian, Schaus, Holger - Federal Mogul

Detail

Since introduction of a new customer satisfaction survey in Europe containing special questions in regard to brake dust, this subject has become more important within the brake development process.


A global Ford internal survey was prepared to establish the level of customer concerns on brake dust in order to better understand the issue. In the survey two subjects were addressed:

  • Dust generation on wheels

  • Removal of dust from wheels


In addition to the general survey results, a methodology used for investigation of factors potentially influencing dust generation is presented. Several characteristics of brake discs (material and machining of friction surface) and pads (thermal treatment) have been specified. The testing using DOE method has been carried out on a specially prepared brake dynamometer.

EuroBrake 2012

Friction Materials (FM)

EB2012-FM-12

Paper

Vernersson, Tore* - CHARMEC & Epsilon, Lundén, Roger - CHARMEC; Abbasi, Saeed, Olofsson, Ulf - KTH Machine Design

Detail

An experimental study on a pin-on-disc rig is presented where the wear of some brake block materials at controlled elevated disc temperatures are reported. It is found for the three studied organic composite materials that the (specific) wear rate increases radically at a temperature of about 500 oC. For temperatures below 500 oC, the wear rate is found to increase with temperature. The cast iron material shows an increase of the wear rate up to 500 oC, after which a transition in the wear mechanism occurs and the wear rate is decreasing with increasing temperature. The studied sinter material shows a weak dependence of the wear rate with temperature.

EuroBrake 2012

Friction Materials (FM)

EB2012-FM-16

Paper

Santamaria Razo, Diego A.*, Merlo, Fabrizio; Buonfico, Pietro - ITT Motion Technologies
Borello, Gaia - Università di Torino
Oliva, Cristiana - Politecnico di Torino

Detail

Friction material properties depend on the raw materials and production processes used during their fabrication as any other composite-like material. Efficiency, wear, vibrations and physical-chemical characteristics are tested in order to evaluate if the developed material has the correct composition for the related application. Brake pads industry puts many resources to understand and manipulate the real impact and influence of each raw material. The increasing number of quality controlled characteristics and the higher attention on ecology and health have pushed product developers to understand which kind of compound they can use and why.


Chemical composition is very important when talking about formulation, but when it is about composites behaviour, it is not enough to know the forming elements of our formula. It is interesting to observe that a group of ingredients may have the same chemical composition but that it may behave completely different under same testing conditions. There is more information to find about each raw material: morphology, surface area, size, density, porosity, hardness, etc.


The use of potassium titanates is very common in the production of brake pads, a very wide range of those compounds is available on the market and their quantity on the formula can vary depending on the desired characteristics of the final product. The selection of the right one and its quantity, according to the pointed market, is very important when speaking about efficiency and in particular about fading. A deep study on the characteristics of different potassium titanates has been done to understand and correlate the raw materials properties with the performance of the final friction materials. Mercury porosimetry, laser granulometry, surface absorption studies (N2 adsorption at 77K), x-ray diffraction (XRD), x-ray fluorescence (XRF) and scanning electron microscopy (SEM) have been carried out in order to characterize the materials in terms of surface area, morphology, density, purity and grain size. An interesting aspect evidenced in this study concerns the comparison between the data of specific surface areas and porosity obtained through mercury porosimetry and gas-volumetric nitrogen adsorption at 77K. Mercury porosimetry (MP), in fact, is the most widely used technique for porosity determination of this kind of materials, but it was found to have an useful complementary technique in gas-volumetric nitrogen adsorption, since nitrogen is able in determining the real porosity of samples, even the presence of small pores, not accessible (and thus not visible) to mercury.


Results were then related to efficiency tests (AK Master), and wear tests. This way, it was possible to find the correlations of morphological and structural behaviours vs. efficiency and stability given by potassium titanates to friction materials. This should help brake producers to achieve materials desired characteristics without passing by a long and costly trial and error process.

EuroBrake 2012

Friction Materials (FM)

EB2012-FM-17

Paper

Wegmann, Enrique*, Stenkamp, Axel - TMD Friction GmbH
Ostermeyer, Georg-Peter - Technische Universität Braunschweig

Detail

Anisotropy is a typical property of friction materials, which can be influenced by temperature gradients, depending on the geometry and the production process, as well as by the components itself present in the mixture like fibres and its orientation. Although orthotropic descriptions from continuum mechanics, as a special case of anisotropy, give good results in simulations of the average brake pad's behaviour using the Finite Element Method (FEM), they don't allow a "mixture simulation" of the friction material and its corresponding components to predict physical properties like stiffness and strength in the mesoscopic range.


This work is a first approach to describe exemplary in a mesoscopic scale the interaction of different components present in a friction material, in particular the influence of temperature gradients on the reaction of binding materials (like resins) and how, together with the orientation of fibres, the local mechanical properties are generated in the brake pad. The simulation explains simple mesoscopic effects in a mixture, responsible for the creation of internal forces, resulting in the macroscopic properties like material stiffness and strength.


A numerical method based on the Discrete Element Method (DEM) and Molecular Dynamics (MD) is used to create a Mesoscopic Particle System (MPS), in which a penalty force definition describes the interaction between different particles, a potential definition is used for the particles correspondent to the fibres material and a newly temperature dependent cross-linking radius is introduced to simulate the corresponding material reaction and its binding properties to other particles. The temperature gradient of the selected brake pad section for the investigation is extrapolated from a thermal simulation during the pressing process using FEM.

EuroBrake 2012

Friction Materials (FM)

EB2012-FM-20

Paper

Hentati Nesrine* - Univ Sfax, Univ Lille Nord de France, ECLille, LML, CNRS; Najjar Denis - ECLille, LML, CNRS; Kchaou Mohamed, Elleuch Riadh - Univ Sfax; Cristol Anne-Lise, Desplanques Yannick - Univ Lille Nord de France, ECLille, LML, CNRS

Detail

Developing organic friction materials for brake lining is a complex task. Friction materials for brake lining contain four classes of ingredients: binder, fibers, friction modifiers and fillers, with some overlap of functions at times. The combination of several ingredients in right amount and acting synergistically is one key to develop desired friction material for a particular braking application. On the other side, friction material efficiency is highly dependent of the hot-molding elaboration process, which affects the lining microstructure and properties. Large efforts have been made to develop these organic friction materials. However, the lake of understanding of the link between material formulation, elaboration process and brake-induced phenomena limits material braking performance improvement that is mainly drive by the know-how and empirical experience of manufacturers.


The present study concerns the hot-molding process of elaboration of a phenolic-resin based composite lining for truck drum brake. In order to limit the complexity of the composite material and consequently of couplings between formulation, process and friction-induced phenomena, a specific formulation is developed with a reduced number of ingredients, derived from an industrial formulation. Temperatures and durations of curing are evaluated considering differential thermal analysis (DTA) of the binder resin and a characterization of its glass transition using a torsional test performed on a KINEMAT device. Lining elaboration with the selected hot-molding parameters is studied on the industrial line process, and friction materials are characterized and compared in terms of tribological behavior and wear on both continuous and braking tribometers.

EuroBrake 2012

Friction Materials (FM)

EB2012-FU-04

Paper

Kirchner, Stefan*, Augsburg, Klaus Prof. Dr.-Ing.- Ilmenau University of
Technology

Detail

The amount of electric and hybrid electric vehicles in development or offered on the market is strictly increasing. To make such vehicles more efficient a common method is energy recuperation during braking. So the generator and hydraulic friction brake have to interact, called brake blending. A main focus of the development of braking systems with the ability for recuperation is the quality of the Human-Machine-Interface (HMI). The aim of the HMI is to give a feeling of authenticity and safety; it also should enable an intuitive brake actuation, so that brake situations and actuations have to be reproducible. This Paper shows in a first step the benchmark of vehicles with regenerative braking systems in combination with decoupled brake-by-wire and conventional coupled braking systems. Typical characteristics are analyzed. In a further step the results of the benchmark are validated with test drives in a special built up research vehicle with programmable pedal and brake characteristic with a wide spectrum of parameters. So the aim of the paper is to infer from objective characteristics to subjective feelings, especially with the focus on disturbances in deceleration caused by the interaction of components of the regenerative braking system.

EuroBrake 2012

FU (FU)

EB2012-IFD-04

Paper

Ostermeyer, Georg-Peter, Graf, Matthias* - Technische Universität Braunschweig

Detail

One type of thermoelastic instability in a brake system occurs as circular hot bands on the disk. Their appearance typically interferes with the observation of other thermoelastic instabilities, e.g. hot spots. The present investigation will focus on the phenomenon of such hot bands. Experiments demonstrate that they are usually not stationary, but slowly change their radial position on the disk, which leads to a nearly periodic brake moment on a timescale of minutes.


We present a family of models that explain this observation taking into account elasticity, thermal expansion, thermal conduction and wear. A minimal model demonstrates how a thermoelastic instability can be partially stabilized, if surface wear is included. Different stability zones can be distinguished, including one where the load is periodically distributed between different contact areas. A nonlinear analysis covers the local loss of contact. Furthermore a discrete Multi-DOF-Model is introduced that describes the contact between brake pad and disk. In an instability regime hot bands periodically change their radial temperature profile on the disk. Highest amplitudes occur at the outer and the inner radius of the pad. The obtained stability zones, the frequencies and wavelength meet the results found by experiments. The presented model allows the investigation of the impact of single parameters, as well as principal mechanisms can be identified that must be taken into account when hot banding phenomena are modeled.

EuroBrake 2012

Interface Friction Dynamics (IFD)

EB2012-MS-07

Paper

Nishiwaki, Masaaki* - Teikyo University
Langthjem, Mikael A - Yamagata University

Detail

The higher brake performance is required for vehicle safety. At the same time, the mass reduction of brake system is especially required for vehicle economic long run performance with lower fuel consumption. Under these backgrounds, higher friction pad materials come to be adopted for brake system in vehicle. But it is well known that pad materials with higher friction coefficient sometimes cause brake noise problems. Therefore it is very important technical issue to reduce brake noises for vehicle with higher brake performance and economic long run with lower fuel consumption.


Many papers have been ever presented for brake squeal, moan noise, creep groan noise and so on. Today it is required in brake design to consider the influences of countermeasure for every brake noise, because moan noise countermeasure sometimes causes low-frequency disk brake squeal for example. The countermeasure should be derived from the analysis for reducing all brake noises, but there is almost no paper of the relationship research between each brake noise. This paper describes the importance of every brake noise relationship, for example, the relationship between low-frequency disk brake squeal and moan noise.


Low-frequency disk brake squeal around 2 kHz was analyzed before. First, the equation of motion for low-frequency disk brake squeal is given by 4 degrees of freedom of calliper with suspension and brake disk. This equation of motion shows the influences of the friction coefficient of pad materials, the contact condition between disk and pad, and the natural frequencies of calliper with suspension and brake disk. Moan noise around 300 Hz was also analyzed before. Secondly, the equation of motion for moan noise is given by 2 degrees of freedom of calliper with suspension. This equation of motion shows the influences of the friction coefficient of pad materials, the contact condition between disk and pad, and the natural frequency of calliper with suspension.


Moan noise is not influenced by the natural frequency of brake disk, because of sufficiently small amplitude of brake disk during moan noise generation. Moan noise gives us the different phenomena impression from low-frequency disk brake squeal.


This paper describes that moan noise is one of the dynamic instable solutions of lowfrequency disk brake squeal, given by 4 degrees of freedom of calliper with suspension and brake disk. When the system has lower stiffness of calliper support, the vibration amplitude of disk is sufficiently small and the amplitude of disk is considered to be negligible. Then the equation of motion is reduced into 2 degrees of freedom, which gives the equation of motion in moan noise. This consideration enables us to reduce moan noise and low-frequency disk brake squeal at the same time.

EuroBrake 2012

Modelling & Simulation (MS)

EB2012-MS-10

Paper

Pevec, Miha*, Vranešević, Darko - Cimos d.d. Automotive Industry
Oder, Grega, Potrč, Iztok, Šraml, Matjaž - University of Maribor

Detail

The stopping capability of disc brakes is an important part of vehicle active safety system, which is predominately affected by the rate at which heat is dissipated due to forced convection and the thermal capacity of the rotor. It is widely known that concentrated high temperatures are responsible for most problems in vehicle braking systems. Any improvements to the thermal mass or cooling characteristics of a braking system will reduce the risk of temperature associated problems and provide safer transport.


In order to improve the safety and to ensure that brake discs will operate within the normal operational range, which is specified by standards, homologation tests were developed to examine the newly developed brake discs operation in extreme braking conditions. Each car manufacturer has developed its own homologation procedures to best correspond to the predicted operation of a specific vehicle.


The current form of a mid-sized passenger car brake disc failed to pass homologation tests due to excessive temperature suggested by specifications at sequential braking test and excessive deformation at deformation – deflection test. Therefore, numerical analyses of different disc brake geometries and their affect to the heat dissipation and deformation characteristics were performed. The thermal and deformation behaviour was first analysed on an existing design using thermo-mechanic finite element analysis (FEA). Non-linear material physical data tested in laboratory combined with wall heat transfer coefficient obtained from CFD airflow analysis were used as a boundary condition. The airflow properties at all operating temperatures and speeds were examined and data were then organized in such a way that could be transferred into FEA analysis. The “swan neck” section and the ventilation channels were especially carefully examined.


Two different brake disc models were proposed, one with increased thermal capacity in the critical areas, best for short single stops and one with improved cooling properties, best suited for multiple sequential followed stops. FEM simulation of the portions of brake dynamometer homologation tests was done on the proposals using the same procedure as on the original brake disc.


The prototypes with proposed modifications were then manufactured and tested on the state of the art brake dynamometer. It turned out that numerical simulation and dynamometer experiment test have closely comparable results. The proposal with the increased cooling properties and modified “swan neck” area was finally chosen because its temperature and deformation are within the proposed boundaries of the homologation test.

EuroBrake 2012

Modelling & Simulation (MS)

EB2012-MS-13

Paper

Dmitriev, Andrey* - Institute of Strength Physics and Materials Science SB
RAS

Detail

Automotive brake pads consist of many components and the role of each of the elements of this complex composition in respect to specified regimes of sliding is not yet completely clear. This is due to mutual interactions and multi-scale mechanisms realized during the friction. In this work we have attempted to partly answer this question using computer simulations. Since the simulation allows us to consider various combinations of the structure of the system being simulated ceteris paribus, it becomes possible to study the impact of each ingredient separately. According to observations by Godet a dry friction is largely determined not by the properties of friction materials of contacting pair, but the characteristics of structure and composition of the thin film that forms on the surface of both bodies as a result of compaction of wear product, its chemical composition and oxidation. This layer, also named as a third body or friction film, differs in composition and microstructure from the first two bodies – a pair of contacting materials, which also may be modified as a result of plastic deformation. We considered a single contact for the steady state sliding when the structure and composition of friction films already are formed. From pad side it was considered cold-worked ferritic steel representing a reinforcing ingredient of the brake pad. From disc side - pearlitic steel representing the major constituent of a gray cast iron brake disc. Both substrates were covered by nanocrystalline iron oxide of type magnetite representing the major phase of the third body and graphite particles representing a typical solid lubricant inclusion in the third body. As a modeling tool we used the method of movable cellular automata (MCA), which has well proven itself in solving of such tasks. This method belongs to methods of discrete approach and is a synthesis of conventional cellular automata and particle method. We investigated the influence of modification of the structure and composition of the third body on the features of system behavior at friction. The following parameters were varied: mechanical properties of inclusions, their concentration, their size, uniformity of distribution in an iron oxide matrix, and the structure of the oxide matrix itself. The results show the influence of the presence of both soft and hard inclusions of different size on the frictional characteristics of the system. To assess the adequacy of the numerical model experimental studies with an artificial third body were also carried out. Comparison of simulation results with experimental data was done on those tests where it was possible from the side of the experimental study. The simulation results are in good agreement with those experimental data.

EuroBrake 2012