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Technical Paper

The Behavior of Fuel Droplets on a Heated Substrate

2021-10-15
2021-01-5099
The processes of surface wetting and film evaporation play a major role in any application using liquid fuels. Since the behavior of entire multi-liquid films is influenced by many simultaneously occurring physical processes, exact modeling is not yet possible. In order to reduce the complexity and to determine the basic effects in the spreading and evaporation of multi-component films, this study was carried out by placing single 5 μl droplets on a heated metal surface. Various alkanes, ethanol, and mixtures, as well as real gasoline, were studied at surface temperatures between 69°C and 140°C. To describe the processes qualitatively and determine the time-dependent wetted surface area, the droplets were visualized using cameras. With the results, it was possible to determine the course of the wetted surface over time and to compare different liquids under varying surface temperatures.
Research Report

Unsettled Issues Regarding First- and Last-mile Transport

2021-10-15
EPR2021024
Sustainable first/last/only-mile (FLO-mile) transport is the key to sustainable travel. It could directly replace private car use for short urban journeys, which account for 1% of global greenhouse gas emissions. More importantly, it could enable public transport to be used for longer journeys, which account for 6% of emissions. Active travel, such as walking and cycling, has the lowest emissions and provides huge economic benefits that pay for the required infrastructure many times over. Unsettled Issues Regarding First- and Last-Mile Transport discusses the mass switch to more sustainable modes of transport and how to increase their perceived value to users. It also covers the prioritization of publicly owned cycles over rideshare options due to the latter’s higher lifecycle emissions, including manufacture, redistribution, and service operations and station construction. Click here to access the full SAE EDGETM Research Report portfolio.
Technical Paper

Research on Braking Energy Recovery Strategy of Pure Electric Vehicle

2021-10-11
2021-01-1264
With the increasingly serious global environmental and energy problems, as well as the increasing number of vehicles, pure electric vehicles with its advantages of environmental protection, low noise and renewable energy, become an effective way to alleviate environmental pollution and energy crisis. Due to the current pure electric vehicle power battery technology is not perfect, the range of pure electric vehicle has a great limit. Through the braking energy recovery, the energy can be reused, the energy utilization rate can be improved, and the battery life of pure electric vehicles can be improved. In this paper, a pure electric vehicle is taken as the analysis object, and the whole vehicle analysis model is built. Through the comparative analysis, based on the driver's braking intention and vehicle running state, the braking energy recovery control strategy of double fuzzy control is proposed.
Technical Paper

Decoding Genuine Ceramic Pad Formulations- Materials and Processing

2021-10-11
2021-01-1277
The need to develop genuine ceramic composites for PV applications arose to overcome the challenges associated with traditional semi-metallic pads. The main focus is to achieve better performance, low noise, better pad and rotor wear, and low dust compared 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 the 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 rotor and pad wear and low dust compared to semi-metallic pads. The traditional steel has been replaced by Aramid, engineered ceramic fibre, potassium titanate (TISMO D), lapinus fibre (RB 250) to impart similar/better performance. The current work investigates the characterisation of genuine ceramic and semi-metallic composites.
Technical Paper

Research on High-efficiency Test Method of Vehicle AEB based on High-precision Detection of Radar Turntable Encoder

2021-10-11
2021-01-1273
With the increasingly complex traffic environment, the vehicle AEB system needs to go through a large number of testing processes, in order to drive more safely on the road. For speeding up the development process of AEB and solve the problems of long cycle, high cost and low efficiency in AEB testing, in this paper, a millimeter wave radar turntable is built, and a high-precision detection algorithm of turntable encoder is designed, at the same time, a test method of vehicle AEB based on the detection data of radar turntable encoder is designed. The verification results show that methods described in this paper can be used to develop the vehicle AEB test algorithm efficiently.
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 Finite Element Code. 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 and elastic moduli in the longitudinal direction can stabilize the system.
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 the automotive industry can cause unfavorable environmental impacts. Existing laws and regulations require heavy metals in brake pads to be phased out of production. Substitutions for metals in friction materials, however, may introduce operational safety issue and other unforeseen problems. 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. Simulations which incorporate interfacial contact between surface asperities were performed to predict the elastic modulus, thermal conductivity, wear rate, and coefficient of friction. The resulting predicted properties may help enhance the performance of engineered metal-free friction materials against thermal-mechanical failures.
Technical Paper

Development of a Simulation for a Shim Durability Test

2021-10-11
2021-01-1283
Shim durability is an important aspect of shim performance. During the brake operation, no mechanical failure of the shim is allowed. Typically, when releasing a shim into production, durability tests must be performed to ensure no failure occurs around the locator holes, and the shim does not walk over the locators. Since the durability test requires an actual pad and shim, the mechanical retention mechanism for the shim (locators) need to be designed, and backplates must be produced. If a failure is detected during these durability tests, either the shim needs to be changed or the retention locators have to be redesigned, which could negatively impact NVH performance and project timing/costs. In this paper, a finite element model is developed to simulate a stop in a shim durability test. The model can be used to predict stress levels at the shim’s locator holes and the failure mode of a shim during a durability test stop.
Technical Paper

Analysis of the Effect of the Wedged Type Brake Caliper Piston on Brake Drag

2021-10-11
2021-01-1293
Recently, there’s a massive flow of change in the automotive industry with the coming era of electric vehicles and self-driving (autonomous) vehicles. The automotive braking system field is not an exception for the change and there are not only lots of new systems being developed but also demands for researches for optimizations of conventional brake systems fitting to the newly appeared systems such as E-Booster and Electric Motor Brake (EMB) Caliper. Taking the Electric Motor Brake Caliper for example, it is considered as a very important and useful system for autonomous vehicles because the motor actuator of the caliper is much easier to control with ECUs compared to the conventional hydraulic pressure system. However, easy of control is not the only thing that excites brake system engineers.
Technical Paper

Sensor-controlled Friction Materials based on Liquid Friction Compounds, Chip-in-Pad Concept

2021-10-11
2021-01-1296
In this paper, the concept of integrating thin-film piezo transducers into friction pads by using a liquid friction material compound (LIQFRIC® HP), which is capable of completely embedding the sensor surface and allowing for the force transfer due to a direct contact between sensor and friction material, is explained. The low thickness of the sensor allows for an excellent ratio of sensor volume / friction volume in the pad. The piezo transducer, besides being able to detect positive and negative pressure changes, can also be used via its EMI capability to allow measurements of changes in the shape (and therefore thickness) of the pad during and after testing. Measuring the pressure distribution, the wear and possible defect situations of the pad potentially opens up new means of friction pad- and brake operations or developments.
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 in the analysis of non-exhaust emission sources because of the growing electrification of vehicles, measurements have been performed in recent years to develop a consistent test standard. In particular, the consideration of tyre and brake abrasion took a predominant position due to the small particle sizes. With measurements under controlled and laboratory-like athmosphere, for example for brakes on dynamometers, attempts have been made to create a uniform test standard according to the Worldwide harmonized Light vehicles Test Procedure (WLTP). However, a transfer to the real driving environment is not yet feasible because of many external disturbance variables, such as the wheel housing or atmospheric variables. 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

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. 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 the friction material (FM) rubbing surfaces, is to sample them on suitable collection filters at a dedicated dyno-bench, during a standard braking test cycle. In particular, the use of enclosed dyno-bench is necessary for excluding other spurious contributions from the environment, while defined test cycles are necessary to simulate standard driving conditions.
Technical Paper

Empowering the Brake Systems

2021-10-11
2021-01-1261
Some research shows 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. Technological advances allow us to use Electronic Stability Control to generate environmental and safety results in mobility for next years.
Technical Paper

Dynamic Brake Test Stand

2021-10-11
2021-01-1274
Nowadays, inertia dynamometers or roller dynamometers are used for the development and testing of vehicle brakes. However, these testing methods are either entirely unable to simulate dynamical conditions, close to real driving maneuvers, or they can do so approximately only at very high costs. This means that brakes, braking systems and brake-related assistance systems such as the ESC system can ultimately only be tested in a full prototype of the car, or before that on hardware-in-the-loop test stands. In the case of the ESC, these test stands have to simulate the behavior of the brake and the surrounding vehicle in real time, then stimulate the interfaces of the ESC sensors accordingly, and finally evaluate the reaction of the ESC system in different situations. The problem here, however, is that the braking system can only be approximated by simulations.
Technical Paper

Research on Trajectory Planning and Tracking Strategy of Lane-changing and Overtaking based on PI-MPC Dual Controllers

2021-10-11
2021-01-1262
Aiming at the problem of poor robustness after the combination of lateral kinematics control and lateral dynamics control when an autonomous vehicle decelerates and changes lanes to overtake at a certain distance. This paper proposes a trajectory determination and tracking control method based on a PI-MPC dual algorithm controller. To describe the longitudinal deceleration that satisfies the lateral acceleration limit during a certain distance of lane change, firstly, a fifth-order polynomial and a uniform deceleration motion formula are established to express the lateral and longitudinal displacements, and a model prediction controller (MPC) is used to output the front wheel rotation angle. Through the dynamic formula and the speed proportional-integral (PI) controller to control and adjust the brake pressure.
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 wheel and the mechanisms on it have not been fully understood. In addition, the proportion of brake wear particles deposited on the wheel surface compared to the total emitted particles is almost unknown. This information is necessary to evaluate the number- and mass-related emission factors measured on the inertia dynamometer and to compare them with on-road and vehicle-related emission behaviour. The aim of this study is to clarify the deposition behavior of brake particles on the wheel surface. First, the real deposition behaviour is determined in on-road tests. For particle sampling, collection pads are adapted at different positions of a front and rear axle wheel. In addition to a Real Driving Emissions (RDE)-compliant test cycle, tests are performed in urban, rural and motorway sections to evaluate speed-dependent influences.
Technical Paper

Development of a Modeling Approach to Numerically Predict Filtration Efficiencies of Brake Dust Particle Filters

2021-10-11
2021-01-1285
According to the European Environment Agency, air pollution is the biggest environmental health risk in Europe. Since traffic is one of the main contributors of fine dust, technical solutions are necessary to reduce the particulate emission footprint of vehicles. Also, the Health Effects Institute hosted recently an international workshop on non-tailpipe emissions. Brake dust filtration concepts have proven to be a promising solution to significantly reduce fine dust emissions from brakes directly at the source. While CFD simulations for inner-ventilated brakes have become state-of-the-art, a holistic model from particle generation and emission to particle dynamics in the vicinity of the brake is not yet available. However, a good modeling approach of particle tracks is essential to predict filtration efficiencies of brake dust particle filters.
Technical Paper

Design and Analysis of a Pneumatically Actuated Drag Reduction System

2021-10-05
2021-01-5080
The main goal of race car aerodynamics is to generate a desired intensity of downforce for the least possible amount of drag. Nonetheless, the balance of the forces under all circumstances due to speed and acceleration is equally important. The modeling was performed using SolidWorks, and the analysis was done both analytically and by means of computational fluid dynamics (CFD) using a flow simulation with STAR-CCM+. The aerodynamics package, which includes the rear wing, front wing, and undertray that help in faster cornering, is analyzed in the full-car analysis. The full-car analysis is done for pitch and yaw. The increase in cornering ability can come from two major aspects: an increase in the aerodynamic downforce and a decrease in the aerodynamic drag of the vehicle. In order to implement the desired aerodynamics package, an airfoil with a predefined profile was selected. The main factor that limits the selection of an airfoil is its effectiveness at low velocities.
Technical Paper

A New Approach to Describe Thermal Aging of Automotive Catalysts Containing Precious Metal Alloys

2021-10-04
2021-01-5095
Regarding thermal real-world aging of automotive catalysts, no deeply developed model or correlation is yet available. Therefore, a new method is developed. A diesel oxidation catalyst (DOC) is aged in the oven and indicated a systematic crystallite growth. Additionally, catalytic deactivation is only dependent on the crystallite size. The crystallite size acts as an indicator for the precious group metal (PGM) surface. This determines a quantitative correlation between the temperature stress, the crystallite size, and, finally, the catalytic activity for oven-aged samples of a DOC. On the basis of this result, the method for the description of oven aging is worked out. It is a physical model that gets as input parameters the aging temperature and aging time for oven aging. This information can be used to calculate the crystallite growth. Further, the corresponding catalytic activity for all species (NO, CO, HC) can also get calculated.
Technical Paper

Aerodynamic Performance Assessment on Typical SUV Car Model by On-Road Surface Pressure Mapping Method

2021-10-01
2021-28-0188
Aerodynamics of on-road vehicles has come to the limelight in the recent years. Better aerodynamic design of vehicle would improve vehicle fuel efficiency with increased acceleration performance. To obtain best aerodynamic body, the series of design modifications and different testing methodologies must be involved in vehicle design and validation phase. Wind tunnel aerodynamic force measurement, road load determination and computational fluid dynamics were the common methods used to evaluate the aerodynamic behavior of the vehicle body. As a novel approach, the present work discusses about the on-road (Real time) testing methodology that is aimed to evaluate the aerodynamic performance of vehicle body using surface pressure mapping. A 64-Channel digital pressure scanner has been utilized in this work for mapping the pressure at different locations of the typical vehicle body.
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