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Technical Paper

Empowering the brake systems

2021-10-11
2021-01-1261
Some researches show that the transport system is one of the main responsible for the emission of pollutants in the atmosphere. The growing demand for automobiles contrasts directly with the scarcity of inputs, planet temperature increasing and air quality degradation in large cities. This counterpoint is explored and discussed a lot, demanding that studies would be conducted to find out sustainable solutions in the production to end-customers. Instead of use fossil resources, one of the options to reduce gas emissions is the use of vehicles powered by electricity. When converting part of the vehicle's kinetic energy into electrical one its reduces emissions in the production electricity – power plants - as well burning gases in transport. Through technological innovations applied in brake systems with stability control embark safety and environment considering a single system.
Technical Paper

Decoding Genuine Ceramic Pad Formulations – materials and processing

2021-10-11
2021-01-1277
Decoding Genuine Ceramic Pad Formulations - materials and processing Bharat S. Tomar, Dr. Sharafat Ali, Dr. Keith Ellis, Yogesh Chaudhary Allied Nippon Private Limited, Sahibabad, Ghaziabad 201010, UP, India --------------------------------------------------------------------------------------------------------------- ABSTRACT The need for development of genuine ceramic composite for PV application arose to overcome the challenges associated with traditional semi-metallic pads. The main focus is to achieve better performance, pad and disc wear along with low dust in comparison to semi-metallic pads. In general, brake pads convert kinetic energy to thermal energy through friction and operating temperature in semi-metallic brake pads is higher due to presence of steel having high thermal conductivity. Over the last decade, the customer preference has moved over to ceramic pads due to light coloured pad surface, low disc and pad wear and low dust in comparison to semi-metallic pads.
Technical Paper

Effect of Material Anisotropy on Thermal-Mechanical Instabilities in Metal Free Friction Materials

2021-10-11
2021-01-1289
Effect of Material Anisotropy on Thermal-Mechanical Instabilities in Metal Free Friction Materials Joseph-shaahu Shaahu, Kingsford Koranteng, and Yun-Bo Yi Department of Mechanical and Material Engineering University of Denver Denver, CO 80208, USA An anisotropic ceramic matrix composite (CMC), which consists of a silicon carbide (SiC) based ceramic matrix reinforced with carbon (C) fibers, is considered as a metal free friction material replacement in brake and clutch applications. The fibers are assumed to have circular cross section, arranged unidirectionally and packed in a rectangular array without the presence of voids. The rule of mixture showed the C-SiC composite to be transversely isotropic with the circumferential plane as the plane of isotropy. A set of parametric studies have been performed to computationally investigate the dominant parameters that affect thermal-mechanical instabilities.
Technical Paper

Investigation of the rational area of friction surfaces in contact of friction linings for disc brakes of passenger cars

2021-10-11
2021-01-1295
It is important for assessing the service life of the braking mechanisms of passenger cars that are in operation is the establishment of the speed and the value of the permissible wear of the friction surfaces, which ensures the durability of the brake. The purpose of the study is to assess effect of area friction surfaces on resource of vehicle braking mechanisms. This will extend the service life of the disc brakes on cars. In the work, the regularities of wear of mating parts of disc brakes were established depending on the change in the geometric parameters of the friction surfaces and operating modes during their operation. It was found that the service life of disc brakes can be increased by 1.16 times with an increase in the area of frictional contact by 15 %, for passenger cars DAEWOO LANOS and LADA PRIORA. A comparative assessment of the wear of the new DAEWOO LANOS and LADA PRIORA brake pads, which perform cyclic emergency braking, is provided.
Technical Paper

Lining Wear Measurements using a Coordinate Measurement Machine

2021-10-11
2021-01-1270
Accurate measurements of brake friction materials are critical to understanding brake behaviors during testing. Current methods typically utilize a hand gauge (or a machine, in some cases) to sample various discrete points on the brake lining. This approach limits measurements to planar wear characteristics, taper and thickness, and excludes more complex measurements such as cupping. The limited number of points means that a single errant point measurement or the choice of point locations can have a large impact on the reported wear measurement. This paper will describe a method for utilizing a Coordinate Measurement Machine (CMM) fitted with a laser line scanning tool to generate a point cloud of data that can then be compared to an earlier measurement of the same piece or to a math model. This method produces thousands of data points which allows for more accurate volumetric wear calculations and color maps of the entire friction face.
Technical Paper

A Contribution to the Understanding of Friction and Squeal of Automotive Brakes: Wear Particle Generation and Deformation of Sliding Surface Region Influencing the Friction Coefficient

2021-10-11
2021-01-1288
Copper-free disc pads of 9 different compositions were made using a traditional hot molding process and tested to study frictional behavior. It is found that the friction coefficient consists primarily of two parts; one part controlled by the plastic deformation of the friction surface region of the disc and pad, and the second part controlled by the total wear of the disc and pads. As the plastic deformation and the wear are non-linear with respect to the load and sliding speed, the friction coefficient becomes a non-linear function of the load and speed. Under moderate braking conditions, the plastic deformation part is more significant in determining the friction coefficient while under more severe braking conditions, the wear contribution becomes more significant.
Technical Paper

An Investigation of Property Changes of Copper-Free Brake Pads During Wear Testing: Pressure and Temperature Dependence of Pad Modulus, and the Correlation Between Modulus and Friction Coefficient

2021-10-11
2021-01-1276
Earlier publications have demonstrated that pad and disc properties change during storage and also during the SAE J2522 Brake Effectiveness Test Procedure. The current investigation was undertaken to find out how the properties change under milder braking conditions, using the SAE J2707 Wear Test Procedure. A copper-free formulation was selected for the investigation and tested on an inertia dynamometer using a front caliper designed for a passenger car. The pad dynamic modulus changed up or down throughout the test, depending on the test conditions. The pad dynamic modulus, the pad natural frequencies and the disc natural frequencies all decreased by the end of the test. Under high-speed, high-deceleration and high-temperature braking conditions, the pad surface region permanently expands, which results in reduced dynamic modulus and also leads to reduced pad thickness loss as compared with pad weight loss.
Technical Paper

A Molecular Dynamics Study of Tribological Properties of Silicon Carbide as a Metal-Free Friction Material

2021-10-11
2021-01-1284
Friction materials containing metal ingredients used in automotive industry can cause unfavorable environmental impacts. Existing laws and regulations require phase out of heavy metals in brake pads. Substitutions for metals in friction materials, however, may introduce operational safety issues. In the current study, a molecular dynamics model based on LAMMPS has been developed to study the effect of material composition, density and geometric configurations on the tribological, mechanical and thermal properties of silicon carbide under various contact conditions at the atomic level. Successful simulations are performed to predict the elastic modulus, thermal conductivity, wear rate and coefficient of friction, with the incorporation of interfacial contact between surface asperities. The predicted properties can help enhance the performance of engineered metal free friction materials against thermal-mechanical failures.
Technical Paper

Thermomechanical Instabilities in Metal Free Friction Materials Using a Nonlinear Transient Simulation Approach

2021-10-11
2021-01-1286
The invention of metal-free friction materials is gaining popularity in the manufacturing of brake pads and clutch friction discs because of the negative factors associated with metals such as copper. To gain more insight into the failure mechanism of the recent invention during brake or clutch applications, a nonlinear transient thermomechanical model is established using ABAQUS. The model is based on a two-dimensional configuration for an investigation on the onset of TMI (Thermo-Mechanical Instability) during sliding contact in such material. The model is validated by comparing the transient simulation results for a full-contact regime to the result from the existing eigenvalue method. A parametric study is carried out to examine how the thermal conductivities and the elastic moduli influence TMI. The simulation results show that the thermal conductivities in the transverse direction can stabilize the system.
Technical Paper

Chemistry of the Brake Emissions: Influence of the Test Cycle

2021-10-11
2021-01-1300
The reliable chemical characterization of non-exhaust emissions generated by brakes is of fundamental importance in order to provide correct information for source apportionment studies as well as for their toxicological and environmental assessment.[1,2,3] Nowadays, the best option to obtain samples of PM10 emissions composed only by material worn from the tribological interface, i.e. the braking disc (BD) and friction material (FM) rubbing surfaces, is to sample them on suitable collection filters at a dedicated dyno-bench, during a standard braking test cycle.
Technical Paper

Cathodic Protection of Brake System Components

2021-10-11
2021-01-1275
Several components of high-end disc brake systems (e.g. Caliper) are obtained using Aluminium alloys and can face severe corrosive attacks if exposed to aggressive environments [1,2]. These phenomena can lead to the formation of non-acceptable aesthetic defects and require the implementation of corrosion protection strategies. Among these, anodization is probably the most common and allows to fulfil the requirements of the automotive market in terms of corrosion resistance (e.g. Neutral Salt Spray resistance) and surface hardness of Aluminium–based elements. Nevertheless, in the presence of galvanic coupling between components (e.g. contact between materials with different nobility, in the presence of an electrolyte) the corrosion rate of Aluminium can increase up to 4-5 orders of magnitude with respect to stand-alone conditions [3]. As a consequence, further corrosion protection strategies are necessary in order to avoid the corrosion of Aluminium parts [3] even if anodized.
Technical Paper

Measurement of Particle Dynamics on the Real Vehicle in Different Driving Scenarios with Swarm Sensors

2021-10-11
2021-01-1299
Due to the increase in public attention to non-exhaust emission sources and their impact on human health extensive measurements have been performed in recent years with the aim to establish a consistent and comparable test standard. In particular, the consideration of tyre and brake abrasion is key because of the small and hazardous particle size and because the increasing ratio of electric vehicles only has these non-exhaust emissions. Measurements under controlled and laboratory-like environments, for example with a brake on a dynamometers, lead to attempts of a uniform test standard according to the WLTP. However, a transfer to the real driving environment is not yet feasible because of many external variables, such as wheel housing or atmospheric influences. Typical reference measurement sensors in the vehicle are only suitable to a limited extent for mobile operation due to their size and the necessary measurement infrastructure.
Technical Paper

Investigations on the deposition behaviour of brake wear particles on the wheel surface.

2021-10-11
2021-01-1301
The deposition behavior of brake wear particles on the surface of a rim and the mechanisms involved have not been fully researched. Similarly, it has not yet been answered how high the proportion of particles deposited on the wheel surface is compared with the particles emitted by the brake and what influences this. This information is a prerequisite for evaluating measurements of particle number and particle mass on the inertia dynamometer and comparing them with real emission behavior. The aim of this study is to verify the deposition behavior of brake particles on the surface of wheels. For this purpose, the real deposition behavior is first determined by on-road tests. For particle sampling, collection pads are adapted at different positions of a front and rear axle wheel. In addition to an RDE-compliant test cycle, urban, rural and motorway sections are used to evaluate speed-dependent influences.
Technical Paper

Transfer Film Composition and Characteristics in Copper-Free NAO Brake Pads

2021-10-11
2021-01-1278
Copper-free non-asbestos-organic (NAO) brake pads have been developed to satisfy the copper content regulations in North America. Copper-free NAO brake pads are required to have a stable friction coefficient owing to the electrification of the control systems, as well as to exhibit improved wear resistance to reduce brake dust emissions. Our previous study indicated that the transfer film formed on the rotor surface affects both the friction coefficient stability and amount of wear. In this study, we investigated how different types of inorganic fillers affect the transfer film formation and its composition in a wear test controlled by temperature. It was confirmed that the main component of the transfer film was iron oxide derived from the rotor. Furthermore, the contained components changed according to the appearance of the rotor surface after each wear test.
Technical Paper

Lining Property Characterizations for an Improved Integration Cascade

2021-10-11
2021-01-1272
New technologies, such as electrified powertrain and autonomous driving solutions, are transforming the automotive industry in such a way that achieving vehicle level performance requirements demands an increasingly intensive and detailed system integration exercise. Validation of the braking system, critical to any vehicle level project, must evolve so that the ever-increasing requirements cascade is answered in a way that ensures the highest level of safety and performance as the industry moves toward a new frontier of features. To support this evolution of integration methodology, critical-to-performance components, such as brake pads, must undergo a transformation in how performance metrics are characterized, communicated, and documented.
Technical Paper

The Impact of Wheel Rotations to the Lateral Runout of a Hybrid Material or Dimensionally Reduced Wheel Bearing Flange

2021-10-11
2021-01-1298
The automotive industry is continuously striving for lower mass components including wheel bearings. A typical wheel bearing is mostly steel, including both the wheel and knuckle mounting flanges. Mass optimizations through cross section reductions and/or the use of alternative materials is now part of component development. While bearing component performance is varied thru analysis and testing by the supplier, Vehicle integration impacts over time also need to be comprehended. In a recent new vehicle architecture, the wheel bearing flange was optimized for low mass. The wheel mount flange thickness was reduced, and holes were added for further optimization. While the design met all the supplier and OEM’s component level specifications, vehicle testing revealed that the wheel bearing developed high assembled lateral runout (ALRO) when the wheels were rotated multiple times during a durability schedule.
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