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Viewing 1 to 30 of 14338
Technical Paper
2014-11-11
Simone Vezzù, Carlo Cavallini, Silvano Rech, Enrico Vedelago, Alessandro Giorgetti
The deposition of thick, pore-free and high performances copper alloy matrix composite coatings is a topic of interest for several industrial applications such as friction materials, high mechanical resistance electrical contacts, and welding electrodes. This study investigates the opportunity to use cold spray for the deposition of CuCrZr/Al2O3 cermet coatings on 6060 aluminium alloys. The project’s aim is to investigate the feasibility of producing integral coolers on mechanical parts. This will make it possible to the design of high performance hybrid motorcycles more compact. Fused and crushed alumina and gas-atomized CuCrZr powder blends have been used as initial feedstocks, with compositional weight ratio of 65/35 and 80/20 (ceramic/metal). The deposition process and coating growth have been studied as a function of carrier gas temperature, exploring the range between 200°C and 750°C. Pure CuCrZr alloy coatings have been also deposited for comparison. The coatings have been characterized in terms of microstructure and morphology, coating microindentation hardness, adhesion to the Al alloy substrate, and cohesion.
Technical Paper
2014-11-11
Akiko Tanaka, Ikue Sato
Southeast Asian Nations are large scale markets for motorcycles and the market size is still growing. Moreover, the volume of plastic parts used for those motorcycles is increasing with growing popularity of scooter-type motorcycles. Accordingly, decorative features applied for plastic coverings are increasingly important to enhance the attractiveness of exterior designs of those motorcycles. Under these circumstances, we had adopted the magnetically-formed decorative painting and applied to a mass-production motorcycle model sold in Thailand in 2008. The magnetically-formed decorative painting is the method in which the designed patterns are formed by painting the material that contains flakes movable along with the magnetic lines of force, while applying an auxiliary attachment to the backside of the parts for generating magnetic fields, such as magnetic sheet trimmed to fit the shape of ornamenting designs. The magnetically-formed decorative painting offers three-dimensional appearance even though its actual surface has no protuberances or dents.
Technical Paper
2014-10-13
Sakthinathan Ganapathy Pandian
Nanolubricants are suspensions of nanoparticles in base fluids, a new challenge for thermal sciences provided by nanotechnology. The objective of this work is to analyze the thermal and tribological properties of yttria stabilized zirconia (YSZ) nanolubricants. Nanosized YSZ particles were prepared by milling YSZ (10μm) in a planetary ball mill equipped with vials using tungsten carbide balls. After 40 hrs, milled YSZ nanoparticles of sizes ranging from 70-90nm were obtained. The nanoparticles were characterized by Energy Dispersive X-ray analysis (EDXA), Scanning Electron microscope (SEM), Transmission Electron Microscope, Thermo Gravimetric-Differential Scanning Calorimeter and non contact 3D surface profilometer and the images of the same were obtained. The heat transfer properties of automotive engine lubricants were determined by utilization of measured thermal conductivity, viscosity index, density, flash point, fire point and pour point, which revealed that lubricants with additive constituents have a significant effect on the resultant heat transfer characteristics of the lubricants.
Technical Paper
2014-10-13
Vicente Macian, Bernardo Tormos, Santiago Ruiz, Guillermo Miró, Tomás Pérez
Abstract Due to the increasingly stringent emissions standards in the world and, on the other hand, the foreseen shortage of fossil fuels, the application of low viscosity engine oils (LVO) is considered one of the most interesting options for counter these threats. In parallel to a fuel consumption fleet test, the aim of this study was to assess the performance of commercial low viscosity oils regarding their degradation and engine wear, since the use of LVO could imply an increase in wear rate. Potential higher engine wear could result in a reduction in the expected engine life cycle, obviously is a non-desired effect. In addition, currently limited data are available regarding “real-world” performance of LVO in a real service fleet. On this test, 39 urban buses were monitored using a detailed and extensive oil analysis program, comprising two engine technologies (Diesel and CNG) and four different lubricants, two of them LVO and other two considered as a reference baseline, during an oil drain period of 30000 km.
Technical Paper
2014-10-13
Oliver P. Taylor, Richard Pearson, Richard Stone, Phil Carden, Helen Ballard
Abstract Most major regional automotive markets have stringent legislative targets for vehicle greenhouse gas emissions or fuel economy enforced by fiscal penalties. Large improvements in vehicle efficiency on mandated test cycles have already taken place in some markets through the widespread adoption of technologies such as downsizing or dieselization. There is now increased focus on approaches which give smaller but significant incremental efficiency benefits such as reducing parasitic losses due to engine friction. Fuel economy improvements which achieve this through the development of advanced engine lubricants are very attractive to vehicle manufacturers due to their favorable cost-benefit ratio. For an engine with components which operate predominantly in the hydrodynamic lubrication regime, the most significant lubricant parameter which can be changed to improve the tribological performance of the system is the lubricant viscosity. Low viscosity lubricants are increasingly being specified by vehicle manufacturers who are now more frequently working directly with the lubricant supplier to design fluids specific to their requirements.
Technical Paper
2014-10-13
Zhiyong Chen, Zhiyuan Chen, Yang Mao, Wenku Shi, Guihui Zhang
Abstract To research the torsional vibration damping characteristic of magneto-rheological fluid dual mass flywheel (MRF-DMF) and the control system in power train, the multi-degree power train torsional vibration model which contains MRF-DMF and semi-active fuzzy control model are built, then the damping characteristic of MRF-DMF in several conditions are gained and compared with MRF-DMF when no control system. The result indicates: the damping characteristic of MRF-DMF effect on power train when using control is better than without control in idle, speed up, slow down, ignition and stalling, while the damping characteristic is less obvious in constant speed because the simulation condition and damping moment relatively stable.
Technical Paper
2014-10-13
Zhi-yong Chen, Ning Sun, Wenku Shi
Abstract In order to improve structure and performance of magneto-rheological dual mass flywheel (MRF-DMF), some parameters effects on dynamic characteristics are acquired by parameters analysis. The dynamic stiffness and loss angle in different current and different frequency are gained through dynamic characteristic test. The fluid-structure interaction finite element model of MRF-DMF is built and the accuracy is verified by comparison between test and simulation. Based on the model, the parameters analysis is done and the law of MRF viscosity, arc spring stiffness, working clearance, rotor radius and axial width effect on dynamic characteristics are gained, it will prove some guidance for the structure and performance improvement.
Technical Paper
2014-10-13
Anandan Sivakumar, V. Saishanker, Raghvendra Gopal
Abstract Success of the vehicle in cold countries depends on performance of the vehicle under cold climatic conditions. In automobiles, structural elastomer components have strong influence on vehicle performance including NVH, ride comfort & durability. Elastomers are sensitive in nature to these climatic conditions due to its temperature dependent visco-elastic behavior. Thus, it is very important to understand structural elastomer component's performance at sub zero temperatures. In a vehicle, Engine mount is used to hold engine firmly and isolate vibrations away from chassis. Vibration isolation of a mount at low temperature is generally affected by the rubber composition. Major ingredients of the rubber composition influencing the low temperature characteristics are Elastomer type, filler type, plasticizer and curing system. Rubber composition plays key role in achieving engine mount properties like static stiffness, dynamic stiffness, permanent set and durability. In this work, influence of low temperature has been successfully evaluated for engine mount application by varying elastomer type, filler type, plasticizer and curing system.
Technical Paper
2014-10-13
Benjamin Kingsbury, Jonathan Stewart, Zhentao Wu, Roy Douglas, Kang Li
Abstract This study describes an innovative monolith structure designed for applications in automotive catalysis using an advanced manufacturing approach developed at Imperial College London. The production process combines extrusion with phase inversion of a ceramic-polymer-solvent mixture in order to design highly ordered substrate micro-structures that offer improvements in performance, including reduced PGM loading, reduced catalyst ageing and reduced backpressure. This study compares the performance of the novel substrate for CO oxidation against commercially available 400 cpsi and 900 cpsi catalysts using gas concentrations and a flow rate equivalent to those experienced by a full catalyst brick when attached to a vehicle. Due to the novel micro-structure, no washcoat was required for the initial testing and 13 g/ft3 of Pd was deposited directly throughout the substrate structure in the absence of a washcoat. Initial results for CO oxidation indicate that the advanced micro-structure leads to enhanced conversion efficiency.
Technical Paper
2014-10-13
Mohammad Reza Hamedi, Athanasios Tsolakis, Jose Martin Herreros
Abstract Recent developments in diesel engines lead to increased fuel efficiency and reduced exhaust gas temperature. Therefore more energy efficient aftertreatment systems are required to comply with tight emission regulations. In this study, a computational fluid dynamics package was used to investigate the thermal behaviour of a diesel aftertreatment system. A parametric study was carried out to identify the most influential pipework material and insulation characteristics in terms of thermal performance. In the case of the aftertreatment pipework and canning material effect, an array of different potential materials was selected and their effects on the emission conversion efficiency of a Diesel Oxidation Catalyst (DOC) were numerically investigated over a driving cycle. Results indicate that although the pipework material's volumetric heat capacity was decreased by a factor of four, the total emission reduction was only considerable during the cold start. Different insulation strategies (e.g. double layer pipe with air gap and vacuum) were simulated using CFD and the improvement in the DOC emission conversion was monitored over the New European Driving Cycle (NEDC).
Technical Paper
2014-09-30
Hongyu Zheng, Linlin Wang
Abstract A brake pad wear control algorithm used under non-emergency braking conditions is proposed to reduce the difference in brake pad wear between the front and rear axles caused by the difference in brakes and braking force. According to the adhesion state of the pad wear, the control algorithm adjusted the braking force distribution ratio of front and rear wheel that balanced adhesion pad wear value. Computer co-simulations of braking with Trucksim and Matlab/Simulink using vehicle models with equal brake pad wear, greater wear on the front axle and greater wear on the rear axle respectively is performed. The computation simulation results show that meet the brake force distribution system regulatory requirements and total vehicle braking force unchanged.
Technical Paper
2014-09-30
Zhigang Wei, Yunfei Qu, Yanping Zhang, Fulun Yang, Matthew Yule, Kay Ellinghaus, Markus Pieszkalla, Figen Lacin
Thermo-mechanical fatigue (TMF) resistance characterization and life assessment are extremely important in the durability/reliability design and validation of vehicle exhaust components/systems, which are subjected to combined thermal and mechanical loadings during operation. The current thermal-fatigue related design and validation for exhaust products are essentially based on testing and the interpretation of test results. However, thermal-fatigue testing are costly and time consuming, therefore, computer aided engineering (CAE) based virtual thermal-fatigue life assessment tools with predictive powers are strongly desired. Many thermal-fatigue methods have been developed and eventually implemented into the CAE tools; however, most of them are based on deterministic life assessment approach, which cannot provide satisfactory explanation for the observed uncertainties introduced in thermal-fatigue failure data. In this paper, a probabilistic thermal-fatigue life assessment procedure is developed.
Technical Paper
2014-09-30
Zhigang Wei, Shengbin Lin, Limin Luo, Litang Gao
Road vibrations cause fatigue failures in vehicle components and systems. Therefore, reliable and accurate damage and life assessment is crucial to the durability and reliability performances of vehicles, especially at early design stages. However, durability and reliability assessment is difficult not only because of the unknown underlying damage mechanisms, such as crack initiation and crack growth, but also due to the large uncertainties introduced by many factors during operation. How to effectively and accurately assess the damage status and quantitatively measure the uncertainties in a damage evolution process is an important but still unsolved task in engineering probabilistic analysis. In this paper, a new procedure is developed to assess the durability and reliability performance, and characterize the uncertainties of damage evolution of components under constant amplitude loadings. The linear and two nonlinear probabilistic damage accumulation models are briefly described first.
Technical Paper
2014-09-30
Fatih Kosar, Mehmet Burak Yegin, Okan Dogru, Cüneyt Akarsu
Abstract Nowadays, a lightweight component design plays a significant role in both cost of a vehicle and fuel economy in competitive heavy duty truck industry. This paper describes the optimization study of an Anti-Roll Bar (ARB) bracket used in a heavy duty truck. ARB system is used to avoid rolling of a vehicle. In order to measure real forces acting on ARB links, calibration study is performed in laboratory conditions. According to this study, measured strains are correlated with theoretical strain-force curve. After the correlation study, fatigue based topology optimization is made on ARB cast iron bracket according to correlated Road Load Data (RLD) which is performed at Proving Ground. Most of the optimization studies in the literature depend on maximum static loading condition. However, many components or structures in the industry subjected to fluctuating loads when they are in service condition. Small loads in a fluctuating load domain may cause potential danger in the design because there will be damage accumulation on the part when those loads are repeated.
Technical Paper
2014-09-30
Venkatesan Chokkalingam, Mohan Rao
Abstract The durability of the components in a vehicle plays one of the major roles in its life cycle cost. The powertrain mount is one such component since its rubber characteristics have significant impact on the vehicle's NVH and fatigue life. This paper presents the enhanced durability benefits obtained by changing the polymer composition, manufacturing methods and design optimization of a powertrain mount for an off-road commercial vehicle. The methodology involved characterization[2] of the existing mount, arriving a new compound formulation, making of prototypes, experimental validation for durability[3] and repeatability in the laboratory combined with rigorous on field vehicle trials. NVH measurements were also carried out on the improved mounts. The above exhaustive exercise resulted in the development of a comprehensively far better mount than an existing mount with improved durability without compromise on NVH properties. The cost benefit in terms of the total vehicle life was enhanced to a large extent.
Technical Paper
2014-09-30
Balakrishnan Natesan
Abstract Phosphorous is an important alloying element in powder metallurgy applications. It is used in Powder metal parts for effective Sintering, dimensional stability, improved machinability, corrosion resistance etc. However it does have some negative effects on properties of Powder metal parts. The purpose of the paper is to study the effect of phosphorous on Powder metal gear of Mix A and Mix B having identical composition differing only in phosphorous content. The samples were detailed on each stage, viz. sintering & Heat treatment. In addition two defective samples were studied to observe the extent to which phosphorous may deteriorate the Powder metal Gear.
Technical Paper
2014-09-30
Nishant Mohan, Mayank Sharma, Ramesh Singh, Naveen Kumar
Abstract The economics of operating internal combustion engines in cars, buses and other automotive equipment is heavily affected by friction and wear losses caused by abrasive contaminants. As such, dust is a universal pollutant of lubricating oils. Road dust consists of depositions from vehicular and industrial exhausts, tire and brake wear, dust from paved roads or potholes, and from construction sites. Present research investigates the influence of dust powder of size 5 μm-100 μm as contaminant in SAE 20W-40 lubricant on the relative motion of a plane surface over the other having circular surface in contact. A pin-on-disk setup as per ASTM G99 has been used to conduct the experiments, firstly at increasing rpm keeping constant load of 118 N, and secondly by increasing loads, keeping rpm constant at 1000. The contaminated lubricant has been used to study its influence on friction and wear rate at the interface of pin of 12 mm diameter and disk at track diameter of 98 mm. Based on the experiments at constant load, the coefficient of friction decreased with increase in rpm and the wear rate first increased and then decreased.
Technical Paper
2014-09-30
Jon Dickson, Matthew Ellis, Tony Rousseau, Jeff Smith
Abstract Fuel efficiency for tractor/trailer combinations continues to be a key area of focus for manufacturers and suppliers in the commercial vehicle industry. Improved fuel economy of vehicles in transit can be achieved through reductions in aerodynamic drag, tire rolling resistance, and driveline losses. Fuel economy can also be increased by improving the efficiency of the thermal to mechanical energy conversion of the engine. One specific approach to improving the thermal efficiency of the engine is to implement a waste heat recovery (WHR) system that captures engine exhaust heat and converts this heat into useful mechanical power through use of a power fluid turbine expander. Several heat exchangers are required for this Rankine-based WHR system to collect and reject the waste heat before and after the turbine expander. The WHR condenser, which is the heat rejection component of this system, can be an additional part of the front-end cooling module. Packaging this WHR condenser as part of the front-end cooling module can be an engineering challenge given the tight underhood environment where the current powertrain cooling components are already near system-capable thermal limits.
Technical Paper
2014-09-30
Francis J. Walker
Abstract According to the International Energy Agency (IEA), the United States consumes 20 million barrels of crude oil per day (840,000,000 gallons)1. More than half of this quantity is imported. It is expected that by 2025 this quantity is expected to rise to 26 million barrels per day with an estimated sixty percent of the consumed quantity being imported. With the prices of oil to continue to be above $90/barrel, the expected annual expenditures on imported oil is estimated to be >$250 billion. With the cost of fossil fuel continuing to increase as its quantity is depleted, there is a strong driver for continued investment in renewable fuel sources. One such approach is the use of plant-based feedstock to augment conventional fossil fuel for diesel applications. Use of such feedstock has given rise to the biodiesel fuel industry (BD). Studies have documented fuel-oil dilution issues in diesel applications. The presence of BD in the engine oil reduces the life of the oil as well as its effectiveness2.
Technical Paper
2014-09-30
Vinod Kumar Mannaru, Sunil M Makhe, Lori Stephens, Dinesh Kumar, Shivaprasad Goud
Abstract Vapor management system is critical to manage fuel tank capacity, evaporative emissions and pressure control for hybrid applications. Due to stringent emission norms and other regulations there has been lot of advancements in design and application of vapor control valves that are used in automotive fuel tanks. Continuous exposure of these valves to fuel vapor or fuel in some instances led to swelling of assemblies and poses serious threat to product functionality and maintaining required tolerances. Swelling of plastics in fuel is ideally a case of multi physics, which involves modeling of complex mass transfer phenomena. In this study a simple thermal analogous approach has been used to model swelling behavior by characterizing the basic plastic-fuel soaking through coefficient of hygroscopic swelling. Extensive testing has been performed with multiple plastic-fuel combinations with different shapes at different temperatures. Periodic measurements helped to extract coefficients in different directions, which have been used to predict swelling induced strains and stresses in the specimens through finite element analysis.
Technical Paper
2014-09-30
C Venkatesan, R DeepaLakshmi
Abstract The automotive industry is constantly looking for new alternate material and cost is one of the major driving factors for selecting the right material. ABT is a safety critical part and care has to be taken while selecting the appropriate material. Polyamide (PA12) [1] is the commonly available material which is currently used for ABT applications. Availability and material cost is always a major concern for commercial vehicle industries. This paper presents the development of ABT with an alternative material which has superior heat resistance. Thermoplastic Elastomer Ether Ester Block Copolymer (TEEE) [3] materials were tried in place Polyamide 12 for many good reasons. The newly employed material has better elastic memory and improved resistance to battery acid, paints and solvents. It doesn't require plasticizer for extrusion process because of which it has got excellent long term flexibility and superior kink resistance over a period of time. Also it has got better heat ageing properties and higher burst pressure at elevated temperature.
Technical Paper
2014-09-30
C Venkatesan, V Faustino, S Arun, S Ravi Shankar
Abstract The automotive industry needs sustainable seating products which offer good climate performance and superior seating comfort. The safety requirement is always a concern for current seating systems. The life of the present seating system is low and absorbs moisture over a period of time which affects seat performance (cushioning effect). Recycling is one of the major concerns as far as polyurethane (PU) is concerned. This paper presents the development of an alternative material which is eco-friendly and light in weight. Thermoplastic Polyolefin (PO) materials were tried in place PU for many good reasons. It is closed cell foam which has better tear and abrasion resistance. It doesn't absorb water and has excellent weathering resistance. Also it has a better cushioning effect and available in various colours. Because of superior tear resistance, it is possible to eliminate upholstery and would reduce system level cost. The development involves testing and characterization of the materials, making of prototypes and validations.
Technical Paper
2014-09-30
Abhishake Goyal, Nadeem Yamin, Naveen Kumar
Abstract Fuel cells are a promising energy source on account of their high efficiency and low emissions. Proton exchange membrane fuel cells (PEMFC) are clean and environmental-friendly power sources, which can become future energy solutions especially for transport vehicles. They exhibit good energy efficiency and high power density per volume. Working at low temperatures (<90°C), hydrogen fuelled proton exchange membrane fuel cells (PEMFCs) are identified as promising alternatives for powering autos, houses and electronics. At the middle of the proton exchange membrane (PEM) fuel cell is the membrane electrode assembly (MEA). The MEA consists of a proton exchange membrane, catalyst layers, and gas diffusion layers (GDL). However, most of the researchers have already mentioned that PEMFC are not competitive enough to rechargeable lithium ion battery with respect to price because of the rare metal used such as platinum in it. Presence of platinum in PEM fuel cells is one of the reasons why fuel cells are excluded from commercialization.
Technical Paper
2014-09-30
Steffen Hoppe, Troy Kantola
Abstract The fundamental drivers in the development of commercial vehicle engines are improved fuel efficiency and the need to meet more stringent exhaust emissions legislation. This strategy presents significant challenges in the development of engine components, particularly piston rings. Within the power cylinder, piston rings are significant contributors to friction losses, with the ring pack contributing up to 25 percent of the total mechanical engine friction loss, and a corresponding fuel consumption of up to four percent. The challenge lies in reducing friction power loss, without compromising oil consumption, while also mastering the increasing thermo-mechanical and tribological demands that piston rings must endure due to increased power density, smoother cylinder bores, reduced lubrication, and the use of alternative fuels. In this context, the robustness of the piston ring running face, as characterized by wear resistance and scuff resistance in particular, plays an increasing role.
Technical Paper
2014-09-30
Marco Carriglio, Alberto Clarich, Rosario Russo, Enrico Nobile, Paola Ranut
Abstract The main purpose of this study is the development of an innovative methodology for Heat Exchangers (HE) design to replace the conventional design procedures. The new procedure is based on the definition of a software package managed by modeFRONTIER, a multi-objective optimization software produced by ESTECO, able to create HE virtual models by targeting several objectives, like HE performance, optimal use of material, HE minimal weight and size and optimal manufacturability. The proposed methodology consists first in the definition of a workflow for the automatic CFD simulation of a parametric model of a periodic HE cellular element. This is followed by the definition of a Response Surface (meta-model) covering all the possible range of parameters' combination, the definition of a “bridge”, e.g. low-fidelity - standard or macroscopic - models to extend the behavior of the liquid and air HE cellular elements to a real scale HE, and an optimization process to obtain the optimal HE design for any proposed application and requirements.
Technical Paper
2014-09-28
Veronika Mayer, Brian Richards
Abstract Fierce competition demands more and more consideration for raw materials that are price competitive without the sacrifice of technical results. High and very often fluctuating raw material costs and availability challenge and complicate the calculation for brake pads raw materials. Therefore there is a strong demand for raw materials with high technical performance at stable predictable costs. For these reasons micaceous Iron Oxide (MIO) is evaluated. A case study describes the substitution of two well-established materials Zirconium Silicate and Potassium Titanate by micaceous iron oxide MIO in disk brake pads. MIO is a naturally occurring mineral with lamellar particle shape. The study compares the addition of 3 wt-% and 6 wt-% of Zirconium Silicate, Potassium Titanate and of MIO in a low-metallic formulation for disk brake pads. Regarding technical performance several properties are evaluated. Tests for friction coefficients are carried out according to the AK-Master SAE J2522.
Technical Paper
2014-09-28
Kazuho Mizuta, Yukio Nishizawa, Koji Sugimoto, Katsuya Okayama, Alan Hase
Abstract Brake pads are composite materials made from dozens of ingredients intended to simultaneously satisfy various performances such as brake effectiveness, wear, noise and vibrations. For this reason, the friction phenomena that occur during braking are complicated. It is important to clarify the friction phenomena, but that is not easy because the associated complexities as mentioned above. We looked to acoustic emission (AE) as an online evaluation method of friction phenomena. AE is a non-destructive testing method that measures elastic stress waves caused by the deformation and fracturing of materials. In fact, it has been reported that the difference between abrasive wear and adhesive wear of a metal can be identified from the change in the frequency spectrum of AE signals. In this study, we verify whether differences in the friction phenomena of brake pads are detectable by the AE method. Three kinds of brake pads were used in the experiments. One of the specimens included an abrasive ingredient, one included an adhesive ingredient, and another included neither.
Technical Paper
2014-09-28
Axel Stenkamp, Michael Schorn
Abstract Starting in the late '90s, a new and innovative brake disk technology entered the high performance passenger car market. Approx. 2 years later, small volume production of carbon-ceramic brake disks started. In the past ten years the number of cars equipped with the new generation of ceramic matrix composite (CMC) brake disks has continuously increased, with main usage in low volume, high horse power applications. The goal of this paper is to give an overview of the system specific boundary conditions as well as today's and tomorrow's targets and aspects of friction material development used in CMC-disk based brake systems. Starting with a description of the system component properties, a comparison of typical CMC vs. standard gray cast iron disk (GCI) applications will be made. The impact of the component properties, especially the disk as friction counterpart to the pad, will be shown by comparing industry standard test scenarios. One described system boundary will be the thermal load to the brake pad.
Technical Paper
2014-09-28
Yannick Desplanques
Abstract The ratio of two forces acting respectively perpendicular and normal to a contact surface of two bodies, the coefficient of friction, is widely used in engineering and science depicting the friction resistance of materials sliding over one another. Ruled by the so-called Amontons-Coulomb friction laws (independence from the load, the contact area and the sliding speed), this dimensionless quantity appears to be convenient for engineering and relatively easy to determine. Nevertheless, the use of tabulated friction coefficients becomes somewhat an issue to predict friction behavior of mechanical systems. The system dependence of friction is sometimes ignored, leading to misapplication. Moreover, the fundamental origins of sliding resistance are not as clear and care should be taken when attributing a fundamental significance to the friction coefficient. This paper aims to clarify findings on friction Charles Augustin Coulomb did and that have been used for hundred of years. At the demand of the French Académie Royale des Sciences calling for rules and accurate data to design machines, Coulomb developed an experimental study of friction of woods and metals used for rubbing parts in machinery.
Technical Paper
2014-09-28
Werner Oesterle, Andrey I. Dmitriev
Abstract Third bodies, also termed friction layers, tribofilms or secondary contact patches, are layers of more or less compacted wear debris between pads and rotor of a disc brake. Our approach of assessing the sliding behavior and friction properties induced by third bodies has been: i) structural characterization after AK-master test procedure, ii) sliding simulation of model structures similar to the observed ones but with simpler and well defined compositions, and iii) verification of simulation results by pin-on-disc tests with artificial third bodies showing the same microstructures and compositions as the model structures. The idea was to simulate structure formation during real braking conditions by high energy ball milling of appropriate powder blends. The final outcome of numerous parameter studies was that a third body containing 15 vol% soft ingredients and 0-20 vol % hard ingredients, both distributed homogeneously in a nanocrystalline iron oxide matrix, should be most desirable for braking.
Viewing 1 to 30 of 14338