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Technical Paper

ED-247 (VISTAS) Gateway for Hybrid Test Systems

2018-10-30
2018-01-1949
Testing a full Aircraft System that includes several on-board computers, physical I/O, and communication buses requires connecting the system to adequate test benches to stimulate or monitor the I/O in a suitable manner. Next generation benches are controlled by test scenarios that reproduce flight situations that occur in a real aircraft. In many situations, it makes sense to replace one or several real computers with a virtual device. Basically, a software representation of the equipment running on a PC helps achieving Verification & Validation (V&V) tasks, even when the real systems are not all available yet. This type of setup, which combines real and virtualized systems, is called a hybrid test system. The required high level of fidelity requires that the next generation bench handles avionic I/O and buses on virtual equipment. ED-247 EUROCAE standard, also called VISTAS, which was recently brought to a mature state allows for this.
Technical Paper

Design, Manufacturing, Testing, and Analysis of a Highly-Constrained Single-Use UAV Wing

2018-10-30
2018-01-1958
Unmanned aerial vehicle (UAV) design aspects are as broad as the missions they are used to support. In some cases, the UAV mission scope can impose design constraints that can be difficult to achieve. This paper describes recent work performed at West Virginia University (WVU) to support repeated flight testing of a single-use UAV platform with emphasis on the highly specialized wings required to help meet the overall airframe mass properties constrained by the project sponsor. The wings were fabricated using a molded polyurethane (PU) foam as the base material which was supported by several different types of rigid and flexible substructures, skins, and matrix-infused fiber elements. Different ratios of infused fiber mass to PU foam were tested and additional tungsten masses were added to the wings to achieve the correct total mass and mass distribution of the wings.
Technical Paper

Numerical and Experimental Second Law Analysis of a Low Thickness High Chamber Wing Profile

2018-10-30
2018-01-1955
This paper presents a coupled numerical and experimental study of an unconventional wing profile such as cp-180-050-gn (Cambered plate C = 18% T = 5% R = 0.78). This wing profile deals with low speeds. It is not currently used on any aircraft model. Otherwise, it presents interesting performances that can be exploited for the design of low-speed STOL or VTOL aircraft by mean of the very high lift that it can generate and can fit with different uses such as VAWT, cyclorotors drones, which are designed explicitly for low-speed operations. After a preliminary CFD assessment of the wing a complete experimental characterisation also at high angles of attack has been performed. The excellent agreement between CFD and experiments has allowed producing a complete analysis of the behaviour of the wing profile both before and after stall conditions. This study has the objective of analysing the viability of such an unconventional wing in traditional or over-stalling conditions.
Technical Paper

Potential Improvements in Turbofan’s Performance by Electric Power Transfer

2018-10-30
2018-01-1962
Bleeding in engines is essential to mitigate the unmatched air massflow between low and High Pressure (HP) compressors at low speed settings, thus avoiding unstable operation due to surge and phenomena. However, by emerging the More Electric Aircraft (MEA) the engine is equipped with electrical machines on both high and Low Pressure (LP) spools which enables transfer of power electrically from one spool to another and hence provides the opportunity to operate engine core components closer to their optimum design point at off-design conditions. At lower power setting of the engine, HPC speed can be increased by taking power from LP shaft and feeding it to HP shaft which can lead to the removal of the bleeding system which in turn reduces weight and fuel consumption and help to overcome engine instability issues. Fuel consumption can be decreased by decreasing inconsistent thrust with the aircraft mission for flight and ground idle settings.
Technical Paper

Multi-Layer Framework for Synthesis and Evaluation of Heterogeneous System-of-Systems Composed of Manned and Unmanned Vehicles

2018-10-30
2018-01-1964
The advancement of both sensory and unmanned technology, combined with increased utilization of autonomous platforms in complex teaming scenarios, has created a need for practical design space exploration tools to aid in the synthesis of effective System-of-Systems (SoS). The presented work describes a modular, flexible, and extensible framework, referred to herein as the Technologies and Teaming Evaluation (TATE) framework, for straightforward identification of high-quality SoS, which may include both manned and autonomous elements, through quantitative evaluation of system-level and SoS-level attributes against a set of user-defined reference tasks.
Technical Paper

Nominal Stress Calculation Based on FEA Element Nodal Forces

2018-10-05
2018-01-1898
Engineering Stress, also known as Nominal Stress, is used in material testing, to quantify load carrying characteristics and abilities, such as ultimate tensile strength (UTS), modulus of rupture (under bending), yield strength, etc. Standard testing, however, is limited to regular cross-section shapes (rectangular, circle, etc.). In engineering applications, however, geometry and loading are typically much more complex. While FEA can be used to calculate local stress concentrations, the underlying Nominal Stress is not known. This paper introduces a method to calculate nominal stresses, based on FEA element nodal forces. Internal testing results of FCD500 (common material for brake components) bars, with and without notches, will be presented. Corresponding Nominal Stresses and local stress concentrations will be discussed, along with testing results.
Technical Paper

Physical and Virtual Simulation of Lightweight Brake Drum Design for Heavy Duty Commercial Vehicles Using Alternate Material Technologies

2018-10-05
2018-01-1897
Brake drum in commercial vehicles is very important aggregate contributing towards major weight in brake system module. The main function of brake drum is to dissipate kinetic energy of vehicle into thermal energy, as a results in braking operation major load comes on brake drum. Hence this is very critical component for vehicle safety and stability [1]. Objective of this paper is to increase the pay load, which is utmost important parameter for commercial vehicle end customers. To achieve the light weighing target, alternate materials such as Spheroidal graphite iron (SGI) has been evaluated for development of brake drum. Many critical parameters in terms of reliability, safety and durability, thickness of hub, wheel loading, heat generation on drum, manufacturing and assembly process are taken into consideration. The sensitivity of these parameters is studied for optimum design, could be chosen complying each other’s values.
Technical Paper

The Factors Governing Corrosion Stiction of Brake Friction Materials to a Gray Cast Iron Disc

2018-10-05
2018-01-1899
Corrosion stiction at the contact interface between a brake friction material and a gray iron disc under the parking brake condition was investigated by evaluating the possible parameters that affect the shear force to detach the corroded interface. Using production brake friction materials, comprising non-steel and low-steel types, corrosion tests were carried out by pressing the brake pad onto the gray iron disc using a clamp at various conditions. Results showed that the shear force to detach the corroded interface tended to increase with applied pressure and corrosion time. On the other hand, porosity, acidity, and hydrophobicity of the friction material did not show a reliable correlation to the stiction force. The poor correlation of the stiction force with the friction material properties indicated that the stiction force was not determined by a single factor but governed by multiple parameters including surface contact areas and inhomogeneity of the ingredients.
Technical Paper

Boundary Layer Dynamics and Sound Generation

2018-10-05
2018-01-1900
In recent years, characteristic structures in the boundary layer of high-load contacts such as brakes have been reported, which substantially influence the dynamics of the tribological contact. Usually, local assumptions concerning the friction behavior of these patches are used to reach global conclusions about the brake system. Several numerical methods (e.g. Cellular Automata) have been developed which employ such assumptions. The validation of these methods through measurement data tends to be laborious and costly. Sprag-Slip elements are friction elements that are exclusively subjected to static friction, never undergoing sliding friction. Implementing such elements on a mesoscopic scale, it is possible to generate global descriptions of macroscopic stick and slip friction phenomena. Locally, these Sprag-Slip elements are similar to the patch structures in the tribological boundary layer of brakes.
Technical Paper

A Study on Trigger of Small Friction Noise in Disc Brake Squeal

2018-10-05
2018-01-1872
Disc brake squeal is caused by flutter of dynamic unstable systems under small disturbance. Therefore the research of small disturbance is very important technical issues for disc brake squeal reduction. The experimental set-up for basic research was developed based on the actual disc brake squeal vibration mode in experiment and its theoretical analysis, which replaces actual caliper and pads to cantilever type pad-caliper. Disc brake squeal depends on the natural frequency of cantilever type pad-caliper, which occurred at 2.7 kHz, 2.0 kHz and 5.3 kHz for each cantilever length L=40 mm, 50 mm and 80 mm in each friction test. In friction tests L=40 mm and 50 mm, cantilever type pad-caliper vibrates with the 1st order bending vibration mode and disc vibrates with the 1st or 2nd order bending vibration mode. In friction test L=80 mm, cantilever type pad-caliper vibrates with the 2nd order bending vibration mode and disc vibrates with the 4th order bending vibration mode.
Technical Paper

Comparison of Different Variable Braking Force Systems

2018-10-05
2018-01-1865
An automobile braking system has a crucial role in the safety of the passengers and riding quality of the vehicle. The braking force mainly depends on the normal reaction on the wheel and the coefficient of adhesion between the tire and the road surface. The required braking force for a vehicle varies with the load on the vehicle. If the applied braking force is greater than the required brake force, wheel gets locked which results in increased stopping distance. In order to prevent the wheel lock at low load conditions or deficient braking force at extremely high load conditions, a variable braking force system is developed. Whenever a motorcycle is loaded, the normal reaction on the rear wheel is increased. Thus, the amount of braking force required to halt the motorcycle with minimum stopping distance and stability of the motorcycle is based on the pillion load on the motorcycle.
Technical Paper

Compressible Brake Fluid Turbulent Flow Simulation and Experimental Verification on Brake Bleeding Performance Improvements of an EPB Caliper

2018-10-05
2018-01-1876
Brake bleeding is the process of removing air bubbles present on hydraulic brake systems from the master cylinder to the calipers of a vehicle, including the brake pipes and hoses. This is very important procedure affecting on brake performance, but still has been a key issue in automobile industry for last decades because reaching best bleeding performance has a limit that there is always remaining air in brake system. In this paper, it is reported on numerical and experimental investigations into the topic of bleeding performance improvements. Compressible brake fluid turbulent flow simulation with two-phase mixture model was performed to investigate the details of the bleeding performance drop during its cycles.
Technical Paper

A Study on Optimization of Brake Cooling System Considering Aerodynamics

2018-10-05
2018-01-1875
As powertrain performance of vehicle improves, brake load is gradually increasing. But it is not easy to increase brake size due to increment of cost and weight despite judder and fade problems are worried in field. Cooling-duct which provides additional forced convection to cool front brake is being considered instead of increasing brake size. However, cooling-duct causes loss of aerodynamic that increases drag coefficient of vehicle. This paper covers the optimization of brake cooling system including cooling-duct, deflector on suspension parts to direct air into front brake and dust cover so that minimize aerodynamic loss and maximize brake cooling performance. The optimal solution had been derived from thermal and aerodynamic simulation with CFD and verified through experimental test with vehicle.
Technical Paper

Design Optimization of the Disc Brake for Squeal Noise Reduction

2018-10-05
2018-01-1874
In this paper, squeal noise reduction method of the disc brake was proposed. And, its effectiveness was described. Pad motion was studied with pad abutment types comparison. The brake design was optimized by using the design of experiment method. The effectiveness of the optimum design was clarified by the noise tests with a dynamometer.
Technical Paper

Incorporation of Friction Material Surface Inhomogeneity in Complex Eigenvalue Analysis to Improve the Accuracy of Brake Squeal Analysis

2018-10-05
2018-01-1873
The sliding surface of the brake friction material is not uniform but composed of random contact plateaus with a broad pressure distribution, which are known to closely related to the triggering mechanism of friction induced noise and vibrations. The non-uniform contact plateaus are attributed to the various ingredients in the friction material with a broad range of physical properties and morphology and the size and stiffness of the plateau play crucial roles in determining the friction instability. The incorporation of friction surface inhomogeneity is, therefore, crucial and has to be counted to improve the accuracy of the numerical calculation to simulate brake noise. In this study, the heterogeneous nature of the friction material surface was employed in the simulation to improve the correlation between numerical simulations and experimental results.
Technical Paper

Increase of Stability for Motor Cars in Service Braking

2018-10-05
2018-01-1880
New solutions for actual problems of determination the efficient distribution of braking forces between the axles of the vehicle, and the stability and drivability of two-axles vehicles at service braking are received in the thesis. It permitted for the first time to determine the Law of distribution of the braking forces between the axles, that ensuring straight-running stability of two-axle vehicle at service braking, to obtain the ideal characteristics for the braking system of two-axle vehicle at service braking and to determine possible values for the distribution of braking force on the front axle. The drivability criterion at service braking obtained further development; it is offered to use boundary at gripping front or rear wheels angular vehicle acceleration on the road.
Technical Paper

Lightweight, Wear Resistant, High Thermal Conductivity Metal Matrix Composite Brake Rotors

2018-10-05
2018-01-1879
Aluminum (Al) - silicon carbide (SiC) metal matrix composite (MMC) brake rotors have been investigated for lightweight vehicular applications but have not widely been utilized due to issues with uniformity of distribution of SiC particulates, residual porosity, formation of undesirable phases such as aluminum carbide, and high temperatures incurred during braking that degrade the rotor’s integrity and performance. ATS-MER has overcome these issues with the development of a patented sandwich type structure with wear resistant thin Al-SiC MMC surface layers and a high thermal conductivity aluminum alloy core. Substantial dynamometer and vehicle testing has been performed by a major automobile company with excellent results, including much lower induced temperatures, 96.3 to 99.6% less particulate (dust) generation in comparable testing of cast iron rotors, and almost 10 times the number of maximum cycles possible during testing of cast iron discs.
Technical Paper

Numerical Study on Fluid Flow and Heat Transfer Characteristics of a Ventilated Brake Disc Connected to a Wheel

2018-10-05
2018-01-1878
The role of a brake disc is to convert the kinetic energy of automobiles into thermal energy caused by friction between the brake pads and disc surfaces. The braking performance of an overheated disc is decreased due to hot judder and fade. Hence, the cooling technology of a brake disc is one of the most important issues related to automobile safety. In the present study, the fluid flow and heat transfer analysis of a ventilated brake disc are conducted numerically. Some geometries of automotive parts such as bearings, hubs and wheels are considered in this study. The commercial code ANSYS CFX is used to simulate the fluid flow and the conjugate heat transfer which includes conduction and convection. To evaluate the cooling performance in each case, the results, including the flow patterns of cooling air inside the wheel and the heat transfer coefficient distribution at the disc surfaces, were investigated and compared for various disc-hub combinations.
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