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2015-09-27
Technical Paper
2015-01-2677
Amir Reza Daei, Diptarka Majumdar, Peter Filip
Automotive brake lining materials are complex composites consisting of numerous ingredients allowing for their optimal performance. Since regulations are increasingly limiting Cu content in brake pads and Cu exhibits extremely high thermal conductivity, graphites being excellent heat conducting materials themselves, are often considered for use as potential Cu replacement. This paper surveys the role of two types of carbons (Superior Graphite) with high thermal conductivity but different mechanical properties and morphology: the so-called i) purified flake graphite (PFG) and the ii) resilient graphitic carbon (RGC). A successful “high-end” commercial low-metallic brake pad was re-formulated (SIU Carbondale) by removing of over 20 wt. % of Cu and replacing it with a cocktail of ingredients including 15 wt. % of these two graphite types (RGC and PFG).
2015-09-27
Journal Article
2015-01-2670
Achim Reich, Angelo Sarda, Martin Semsch
Abstract Drag torque is generated in disk brakes as a result of contact (dynamic friction) between brake disk and brake pads when the braking system is not actuated. Among the negative implications of drag torque are, notably, dispensable additional fuel consumption as well as increased pad wear, which can also unfold as uneven along the pads' surfaces. The paper is based on extensive knowledge acquired through several measurement-based studies and contains a comprehensive assessment of the main topics related to the subject. Dedicated measurements illustrate the influence of different parameters on the level of drag torque and deliver a basis for a discussion about the conflict of objectives which may arise from the implementation of specific mitigation measures. Further emphasis is laid on the presentation of the state of the art concerning the main direct and indirect methods to evaluate drag torque characteristics of brake systems.
2015-09-27
Journal Article
2015-01-2673
Toshikazu Okamura
Abstract Brake judder is one of the most serious problems in automotive-brake systems, and brake discs play a significant role in judder. There are two types of brake judder: cold and hot. Hot judder is caused by the thermo-mechanical deformation of a disc rotor due to high-speed braking. There are several causes and shapes of the deformation, e.g., coning and circumferential waviness. Circumferential waviness of brake discs is typically found as a butterfly shape in a 2nd rotational-order and corrugation (or hot-spotting) around a 10th order, which are caused by thermo-mechanical buckling. The author focused on the effects of material and dimensional homogeneity on the transient and permanent wave-like deformation of ventilated discs in low rotational-orders during repetitive high-speed braking. The tested discs were in two groups that had the same design and gray-cast-iron class but were cast in two foundries by using horizontal- and vertical-molding machines, respectively.
2015-09-27
Technical Paper
2015-01-2674
Dragan Aleksendric, Velimir Cirovic, Dusan Smiljanic
Abstract Customer perception of brake pedal feel quality, depends on both the customer's subjective judgment of quality and the actual build quality of the brake system. The brake performance stability represents an important aspect of a vehicle performance and its quality of use. This stability is needed especially in brake by wire system and braking system with regenerative braking. In order to provide stable braked pedal feel i.e. consistent the brake performance against the brake pedal travel, the model of the brake performance versus the brake pedal travel needs to be established. In this paper new hybrid neuro-genetic optimization model was developed for dynamic control and optimization of the disc brake performance during a braking cycle versus the brake pedal travel. Based on such model, the brake performance optimization of the passenger car has been provided against the brake pedal travel.
2015-09-27
Technical Paper
2015-01-2684
Seongjoo Lee, ShinWook Kim, ShinWan Kim, Seong Rhee
Rear disc brake squeal test results confirm the disc wear - brake squeal correlation reported earlier on front disc brakes. A significant amount of Fe transferred from the disc to the NAO pad surface is detected and the distribution of the transferred Fe is very non-uniform on the pad surface. The pad surface formulation reaches that of Low-Steel Lomets. Disc pads from a noisier brake retain more transferred particles than from a less noisy brake. The pad surface retains more transferred Fe after noise test procedures than after performance test procedures. The transferred Fe particles are either barely visible or invisible. During brake noise test procedures, discs wear in weight as much as disc pads. No correlation is found between average in-stop Mu, maximum in-stop Mu or in-stop delta Mu and brake squeal.
2015-09-27
Technical Paper
2015-01-2685
Diego Masotti, Patric Neis, Ney Ferreira, Kássio Gomes, Jean Poletto, Luciano Matozo
Abstract The present work presents evaluation of the sliding surface morphology of brake pads during stick-slip. A low-metallic (LM) and a Non Asbestos Organic (NAO) brake friction materials were subjected to slide against a brake disc under conditions favorable to produce stick-slip phenomenon. The experiments were conducted in a laboratory-scale tribometer, which was especially designed to test brake pads used in vehicle. Delta torque divided by slip time (dT/dtslip) was the parameter used to quantify stick-slip propensity. In addition, optical microscope images of the material's surface were obtained at different stages of the braking test. These images were post-processed in appropriate computational software and by means of the segmentation technique, the real contact area, size and amount of contact plateaus related to the brake pad surface were estimated. This technique was effective to quantify the differences in the sliding surface morphology during low speed braking test.
2015-09-27
Technical Paper
2015-01-2680
Kazuhiko Tani, Hironori Nakamura
Abstract Combined Brake System for small motorcycles has been developed. In small motorcycles, some models have a hydraulic disc brake both in the front and rear wheels but many of them have a hydraulic disc front brake and a mechanical drum rear brake. Accordingly, it was necessary to develop a new system to link the hydraulic system with the mechanical system to allow an application of Combined Brake System to these models. In this paper, a CBS having a new configuration is described where a disc brake and a drum brake are linked in a simple lever structure of an input force distributor, and an inhibitor spring at the foot pedal. With this mechanism equipped, the distribution of brake forces is controlled. When a large input force is applied, a large proportion of brake force is applied to the front brake to obtain adequate deceleration. When a mild input force is applied, which is frequently operated, the brake force proportion is large in the rear compared to the front.
2015-09-27
Technical Paper
2015-01-2681
Ramakanta Routaray
Abstract In a two wheeler efficient braking becomes indispensable. CBS, ABS plays a significant achievement in meeting the required braking efficiency [2, 5, and 6]. Conversely for non CBS & non ABS motor cycles, braking efficiency [2, 5, and 6] becomes a challenging task for two wheeler OEM suppliers. This is because of the customers' affordability for the required degree of efficiency [2, 5, and 6]. This paper depicts the innovative design of brake drum [3, 4] pertaining to its functional aspect; catering to meet customer needs economically. Cast iron Brake drum [3, 4] is redesigned with an engineered solution which allows draining the water in rainy season. This has been verified though mathematical approach about contact [1] area between liner and brake drum [3, 4]. Thereafter proto part has been made as per 3D concept. Test Results of proposed design have been compared with the existing drum brake system.
2015-09-27
Technical Paper
2015-01-2692
Giulia Garello, Niccolò Patron, Pietro Buonfico, Luca Martinotto
Abstract The nature of braking friction is extremely complex and a deeper understanding of the physical mechanisms that govern the energy dissipation at the interface of friction pairs is an important tool to create an even deeper knowledge of tribological behavior of friction material. Friction brakes need to transform kinetic energy into heat: a complete knowledge of thermal effects during this process in every brake component is an essential part of brake design. As referred to brake pads, the analysis of dynamometer testing data highlighted experimental evidence related to thermo-mechanical effects, such as the different wear resistance capabilities of material classes (NAO and Low Steel). As is well known in the industry and already published, we observed that tribological characteristics are not constant under all testing conditions and they strongly depend on temperature being the direct consequence of kinetic energy dissipation.
2015-09-27
Journal Article
2015-01-2694
Cheng Ruan, Lijun Zhang, Dejian Meng
Abstract During light to moderate braking at high speed, the local high temperature phenomenon can be observed on the brake disc surfaces, known as hot spots. The occurrence of hot spots will lead to negative effects such as brake performance fade, thermal judder and local wear, which seriously affect the performance of vehicle NVH. In this paper, based on the bench test of a ventilated disc brake, the basic characteristics of hot spots is obtained and the evolution process of temperature field and disc deformation is analyzed in detail. In temperature field, hot bands appear first and grow, migrate from inner and outer radius to the middle, with the growing temperature fluctuation and finally hot spots appear in the middle radius of the brake disc. The stable SRO waviness forms much earlier than the temperature fluctuation. In the stop brake studied in this paper, the SRO waviness stabilizes in main 7 order state which is lower than the final hot spot order.
2015-09-27
Journal Article
2015-01-2693
Neno Novakovic
Abstract Aircraft anti-skid brake control system is considered one of the most complex aircraft systems whose performance depends not only on subsystem parameters but rather on many other external conditions and physical parameters which are difficult to control and predict. Over the years aircraft brake control system performance and fault diagnostics have been simulated and analyzed from various aspects. Based on the task to enhance aircraft brake control system diagnostic methods, this article presents one approach to mathematical modeling and a numeric identification method of the hydro-mechanical brake control components. For any complex system behavioral or performance analysis approach, system modeling and simulation are the most common tools. Most often, the complete system model is unknown, and only simple segments of the unknown system or a small number of subsystem components may be known in a form of transfer function with static and dynamic characteristics.
2015-09-27
Technical Paper
2015-01-2687
Aditya Kant Choudhary, Yogesh Mense, Saurabh Singh, Mahesh Shridhare
Abstract Brake noise is one of the common complaints and an irritant not just for the vehicle occupants but equally for the passers-by. Brake noise is actually vibration that is occurring at a frequency that is audible to the human ear. This occurrence of brake noise like brake squeal (>1 kHz) and groan (<1 kHz) is often very intense and can lead to vehicle complaints. During a brake noise event, vehicle basic structure and suspension system components are excited due to brake system vibration and result in a resonance that is perceived in the form of a noise. Proposed work discusses an experimental study that is carried out on a vehicle for addressing concern regarding disc brake squeal and groan noise. Based on the preliminary inputs, vehicle level study was carried out in order to simulate the problem and objectively capture its severity.
2015-09-27
Technical Paper
2015-01-2689
Katsuhiro Uchiyama, Yuji Shishido
Abstract Brake groan analysis and improvement is progressing based on experimental measurements. An advanced brake assembly FEA model was built which considers torsional stiffness of suspension for analyzing creep groan. Creep groan is a representative groan noise of brake system from stick-slip phenomenon standpoint. This year we will present our study for advantageous direction for reduction of creep groan which will focus on friction material µ vs. Velocity (µ-V) property, friction material physical properties and relative velocity between brake pads and rotor by advanced brake assembly FEA model.
2015-09-27
Technical Paper
2015-01-2704
Michael Herbert Putz, Harald Seifert, Maximilian Zach, Markus Schiffer, Jure Peternel
Abstract At first glance a friction brake should be controlled by normal force to produce predictable brake force. Controlling an actuator (and hence brake pad) position basically seems to introduce uncertainties to normal force and brake force, because at first view the position tells little about actual normal force. The electro-mechanical brake (EMB) of Vienna Engineering (VE) can be operated by position-control, either without force sensor (saving costs) or even with a true brake torque sensor. For position control a relation between actuator position and normal force is used. When pad wear is correctly adjusted a certain actuator position produces a given deformation and at known elasticity the deformation produces a defined normal force. In the VE-EMB this relation uses a three-dimensional curve and includes temperature influence of the coefficient of friction, thermal expansion and thermal elasticity change.
2015-09-27
Technical Paper
2015-01-2702
Chihoon Jo, Jaeseung Cheon, Jongsung Kim, Yongsik Kwon
Abstract EMB (Electro-Mechanical Brake) which converts electrical motor power to brake clamping force at each wheel is a system that has been investigated and developed by various automotive part suppliers through the years. In particular, as the number of electrically powered vehicles, such as hybrid electric vehicles, electric vehicles and fuel cell electric vehicles, has expanded, the EMB has received increased interest due to its fast response that is much suited for effective cooperative control with regenerative braking. However, issues such as cost competitiveness, reliability and regulations need to be solved for commercialization [1-2]. A new concept, the hybrid Electro-Mechanical Brake (hEMB) is characterized by a dual piston structure linked by hydraulics inside of the caliper. It is possible to reduce the required motor power and increase the level of emergency back-up braking through the amplification effect of the dual piston mechanism [3].
2015-09-27
Technical Paper
2015-01-2708
Yi Yang, Liang Chu, Liang Yao, Chong Guo
Abstract During the vehicle braking, the Regenerative braking system (RBS) transforms the kinetic energy into electric power, storing it in the power sources. To secure the baking process, it is required to use hydraulic braking pressure to coordinately compensate the regenerative braking pressure. The traditional hydraulic pressure control algorithm which is used in regenerative braking system coordinated control has obvious laddering effect in braking. Unit control cycle pressure deviations seriously affect the comfort and the braking feeling on the vehicle.
2015-09-27
Technical Paper
2015-01-2703
Guirong Zhuo, Fei Yu, Yilin Ren
Abstract Study on the braking torque allocation of the ABS (Anti-lock Brake System) of the electro-hydraulic brake system in the distributed drive electric vehicles, using a hierarchical control structure, of which the lower controller takes a braking torque allocation strategy based on frequency, so as to achieve a good braking effect. The lower controller uses the strategies which are based on the filter principle or the weighted least squares algorithm. To the former, Butterworth filter is selected to execute the braking torque allocation. Then the ABS braking torque allocation strategy based on Butterworth filter and the weighted least squares are designed and analyzed respectively, finally their braking effects are simulated and contrasted in Simulink and AMESim.
2015-09-27
Technical Paper
2015-01-2699
Songyun Xu, Zhuoping Yu, Lu Xiong
Abstract With the electrification and intelligentialization of vehicle, requirements on more intelligent and integrated brake system are put forward. A novel integrated-electro-hydraulic brake system (I-EHB) for automotive is presented to fulfill these requirements. I-EHB is consisted of active power source (APS), pedal feel emulator (PFE), electro control unit (ECU) and hydraulic control unit (HCU). The system characteristics of I-EHB are tested through test rig. According to characteristics experiments, friction and non-linear phenomena in hydraulic pressure control are found. In order to overcome these phenomena in control of I-EHB, chatter-compensation is adopted based on experiment analysis. Algorithm are tested and optimized through test rig. As a result, through chatter-compensation the hydraulic pressure is controlled accurately and chatter-compensation is optimized for different working conditions.
2015-09-27
Technical Paper
2015-01-2701
Meixia Ji, Xuexun Guo, Zhenfu Chen, Bin Wang
Abstract The control forms of the vehicle have transformed from hydraulic or mechanical control to electrical control owing to the increasing demand of automotive safety and soaring development of electronic technology. Compared with the traditional mechanical parking brake system, the electrical control of brake named Electrical Parking Brake (EPB) System presents a variety of advantages. What's more, it shares common actuators and realizes the communication between electrical control systems to advance the vehicle industry to intellectualization. With such superiority, the EPB System has aroused much interest. But the difficulty in building the simulation model lies in the description of friction in screw-nut system of which the nonlinear component causes the hysteresis. However, almost all models found in the literature before are the static friction model with the limit of description of dynamic features like pre-sliding frictional features and parameters variation.
2015-09-27
Technical Paper
2015-01-2698
Guirong Zhuo, Subin Zhang
Abstract In this paper, a novel Electromechanical Brake actuator (EMB) is redesigned aimed at an electric vehicle driven by wheel hub motor. The two way ball screw is adopted in this mechanism. Clearance automatic adjustment and parking braking function is added in this mechanism. As a consequence, fast braking response is achieved and the wear difference of the inner and outer pads can be minimized and the initial braking force can also be improved. The electric vehicle is based on a traditional chassis. In this electric vehicle which driven by wheel hub motor, the brake disc and brake actuator will be correspondingly moved inside because wheel hub motor will take up inner space of wheel hub. As a result, the actuator might interfere with the suspension and steering systems and influence hard spot of chassis design. To solve this problem, conversely installed caliper concept is used in this paper.
2015-09-27
Journal Article
2015-01-2672
Aihong Meng, Jian Song
Abstract High speed on-off valve is applied widely in vehicle control systems. When high speed on-off valve is controlled by Pulse Width Modulation (PWM) of high frequency, the valve core can float at a certain position which is adjusted by changing the duty ratio within a certain effective range. Then the high speed on-off valve can control the flow and pressure linearly like proportional valve. Thus it is essential to extend the effective range of duty ratio to improve the linear control performance of high speed on-off valve. In this paper, the high speed on-off valve of the automotive Electronic Stability Program (ESP) is the focus, and its flow force is analyzed in detail to get the effects of hydraulic parameters on the valve performance. The mathematic model of the high speed on-off valve is derived. Then the valve structural parameters are optimized according to the Genetic Algorithm(GA), offering the theoretical references for extending the effective duty ratio of PWM.
2015-09-27
Technical Paper
2015-01-2690
Joo Sang Park
Abstract There are three kinds of noise mechanisms which are stick-slip, self-excited vibration and unstable dynamic behavior. This study is of a pad unstable behavior caused by pad spring contact stiffness and weak forces and improving a lower squeal noise due to self-excited vibration in brake system. This paper discusses a theoretical approach, numerical and experimental test to understand the squeal mechanism for unstable pad behavior and the analysis and measurement of mode coupling between brake components to decrease noise propensity. Three different approach are considered to understand noise mechanism. Fundamental approach is more important than experimental modal analysis, CEA (Complex Eigen value Analysis) because the minimal vibration analysis is principle approach which has been proved by many researchers. CEA and modal test is useful to study the relationship between lower squeal noise and self-excited vibration for more details.
2015-09-27
Technical Paper
2015-01-2696
Shuichi Okada
We had developed Electric Servo Brake System, which can control brake pressure accurately with a DC motor according to brake pedal force. Therefore, the system attains quality brake feeling while reflecting intentions of a driver. By the way, “Build-up” is characteristics that brake effectiveness increases in accordance with the deceleration of the vehicle, which is recognized as brake feeling with a sense of relief as not to elongate an expected braking distance at a downhill road due to large-capacity brake pad such as sports car and large vehicles. Then, we have applied the optical characteristic control to every car with Electric Servo Brake System by means of brake pressure control but not brake pad. Hereby, we confirmed that the control gives a driver the sense of relief and the reduction of pedal load on the further stepping-on of the pedal. In this paper, we describe the development of brake feel based on the control overview.
2015-09-27
Technical Paper
2015-01-2683
Sarah Chen, Steve Hoxie
Abstract Developing a quiet brake system has been a constant task for OEMs as well as their brake suppliers. As a major component in the brake system, the rotor plays a significant role in brake noise performance. Owning to the cost and damping property advantages, gray iron is still the most widely used material for brake rotor application. When pads/rotor coupling is examined to address noise issues, however, most efforts have been on pads and insulators. Rotor specifications are rather general and the component is typically accepted based on grades defined by mechanical property minimum (mostly in G3000 SAE J431). Nevertheless, we have found that gray iron within a grade can have wide microstructure variations, and the deviation (especially on the rotor friction surface) can critically affect the noise propensity in addition to friction output performance and wear characteristics. In this work, the impact of brake disc material on brake noise and output performance is investigated.
2015-09-27
Journal Article
2015-01-2667
David B. Antanaitis, Chris Ciechoski, Mark Riefe
Abstract Previously published research [1] covering the role of piston material properties in brake torque variation sensitivity and roughness concluded that phenolic pistons have significantly higher low-pressure range compliance than steel pistons, which promotes lower roughness propensity. It also determined that this property could be successfully characterized using a modern generation of direct-acting servo hydraulically actuated brake component compression test stands. This paper covers a subsequent block of research into the role of the caliper piston in brake torque variation sensitivity (BTV sensitivity) and thermal roughness of a brake corner. It includes measurements of hydraulic stiffness of pistons in a “wet” fixture, both with and without a brake pad and multi-layer bonded noise shim.
2015-09-27
Journal Article
2015-01-2661
Amir Reza Daei, Nima Davoudzadeh, Peter Filip
Abstract Brake linings have complex microstructure and consist of different components. Fast growing automotive industry requires new brake lining materials to be developed at considerably shorter time periods. The purpose of this research was to generate the knowledge for optimizing of brake friction materials formula with mathematical methods which can result in minimizing the number of experiments/test, saving development time and costs with optimal friction performance of brakes. A combination of processing methods, raw materials and testing supported with the Artificial Neural Network (ANN) and Taguchi design of experiment (DOE) allowed achieving excellent results in a very short time period. Friction performance and wear data from a series of Friction Assessment and Screening Test (FAST) were used to train an artificial neural network, which was used to optimize the formulations. The averaged COF, COF variation and wear were used as the output parameters.
2015-09-27
Journal Article
2015-01-2662
Daniela Plachá, Pavlina Peikertova, Jana Kukutschova, Poh Wah Lee, Kristina Čabanová, Jiří Karas, Jana Kuchařová, Peter Filip
Abstract The brake wear contribution to the environmental pollution has been extensively discussed, with major focus on asbestos and heavy metals released to the environment. Only limited attention was paid to released organic compounds generated during friction processes, although the organic and carbonaceous components are not the minor part in brake lining formulations. Friction processes in brakes are associated with relatively high temperatures and high pressures on the friction surfaces which relates to the thermal decomposition of the organic components in friction materials and to brake lining thermal fade. Thus, this study focuses on the identification of organic compounds released from a model low metallic brake material.
2015-09-27
Journal Article
2015-01-2678
Diego Adolfo Santamaria Razo, Johan Decrock, Ann Opsommer, Maarten Fabré, Fernao Persoon
Abstract Friction performance is the result of the interaction between rotor and friction material surfaces. Kinetic energy has to be transformed into heat, plastic deformations, chemical reactions and wear debris. The later generates the formation of the so-called third body layer and its initiation, growth and degradation will generate the actual friction coefficient and vibrations behavior. Some raw materials seem to promote third body layer formation more than others. The composition of plateaus usually contains iron oxide, copper, carbon, silicon and calcium. Since copper free materials are under development, the importance of understanding the third body layer formation has become bigger. Promaxon® D is widely used in NAO non steel formulations. It is a calcium silicate with a special morphology that influences friction material at two levels: the macro -bulk- scale and the micro -surface- scale. Bulk effect is related to the volume and porosity degree of the friction material.
2015-09-27
Journal Article
2015-01-2679
David B. Antanaitis
Abstract An aspect of high performance brake design that has remained strikingly empirical is that of determining the correct sizing of the brake pad - in terms of both area and volume - to match well with a high performance vehicle application. Too small of a pad risks issues with fade and wear life on the track, and too large has significant penalties in cost, mass, and packaging space of the caliper, along with difficulties in maintaining adequate caliper stiffness and its impact on pedal feel and response time. As most who have spent time around high performance brakes can attest to, there methods for determining minimum brake pad area, usually related in some form or another to the peak power the brake must absorb (functions of vehicle mass and top speed are common). However, the basis for these metrics are often lost (or closely guarded), and provide very little guidance for the effects of the final design (pad area) deviating from the recommended value.
2015-09-27
Journal Article
2015-01-2691
Ju Young Kim, Jeongkyu Kim, Young Min Kim, Wontae Jeong, Hojoon Cho
Abstract In the brake system, unevenly distributed disc-pad contact pressure not only leads to a falling-off in braking feeling due to uneven wear of brake pads, but also a main cause of system instability which leads to squeal noise. For this reason there have been several attempts to measure contact pressure distribution. However, only static pressure distribution has been measured in order to estimate the actual pressure distribution. In this study a new test method is designed to quantitatively measure dynamic contact pressure distribution between disc and pad in vehicle testing. The characteristics of dynamic contact pressure distribution are analyzed for various driving conditions and pad shape. Based on those results, CAE model was updated and found to be better in detecting propensity of brake squeal.
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