scholarly journals Influence of Contact Plateaus Characteristics Formed on the Surface of Brake Friction Materials in Braking Performance through Experimental Tests

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4931
Author(s):  
Rafael Lucas Machado Pinto ◽  
Juan Carlos Horta Gutiérrez ◽  
Robson Bruno Dutra Pereira ◽  
Paulo Eustáquio de Faria ◽  
Juan Carlos Campos Rubio
Keyword(s):  
Friction Pair ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Performance Measurements ◽  
Friction Materials ◽  
Braking Performance ◽  
Emergency Braking ◽  
The Coefficient Of Friction ◽  
And Performance

This work applies a procedure for analysis and characterization of the surface of brake friction materials, correlating them with the tribological and thermal properties achieved in different vehicle braking conditions. Experiments were performed in a vehicle under two real conditions of braking operation, simulated flat track descent and emergency braking. Characteristics of the plates formed on the surfaces of the friction materials were analyzed by scanning electron microscopy (SEM) and correlated with the performance during braking, as measured by the coefficient of friction at the interface of the friction pair and temperature. As a result, the formation of the primary and secondary plateaus in these two different braking operating conditions was observed, and the relationship between the characteristics of the plateaus formed on the surface and the surface roughness parameters and performance measurements during braking.

scholarly journals Analysis and Comparative Assessment of Basic Tribological Properties of Selected Polymer Composites

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 75 ◽  
Author(s):  
Jerzy Jozwik ◽  
Krzysztof Dziedzic ◽  
Marcin Barszcz ◽  
Mykhaylo Pashechko
Keyword(s):  
Polymer Composites ◽  
Friction Force ◽  
Tribological Properties ◽  
Friction Pair ◽  
Computer Software ◽  
Operating Conditions ◽  
The Coefficient Of Friction ◽  
Cast Polyamide ◽  
Friction Path ◽  
Materials Used

Phenomena occurring in the contact area between two mating bodies are characterised by high complexity and variability. Comparisons are usually made between parameters such as the coefficient of friction, friction force, wear and temperature in relation to time and friction path. Their correct measurement enables the proper evaluation of tribological properties of materials used in the friction pair. This paper concerns the measurements of basic tribological parameters in the friction of selected polymer composites. Knowing the tribological properties of these composite materials, it will be possible to create proper operating conditions for kinematic friction pairs. This study investigated the coefficients of friction, friction force and temperatures of six polymer composites: cast polyamide PA6 G with oil, PA6 G with MoS2, polyoxymethylene POM with aluminium, polyethylene terephthalate PET with polytetrafluoroethylene PTFE, PTFE with bronze, and PTFE with graphite. The friction surface was also examined using an optical system and computer software for 3D measurements. As a result, PA6-G with oil was found to be the best choice as a composite material for thin sliding coatings.

Flow Coefficient Evaluation of Poppet Valves Used in Reciprocating Compressors for LDPE

2008 ◽  
Author(s):  
Enzo Giacomelli ◽  
Massimo Schiavone ◽  
Fabio Manfrone ◽  
Andrea Raggi
Keyword(s):  
Pressure Drop ◽  
Time Pressure ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Operating Life ◽  
High Fatigue ◽  
Strongly Connected ◽  
And Performance ◽  
Poppet Valves

Poppet valves have been used for a long time for very high pressure reciprocating compressors, as for example in the case of Low Density Polyethylene. These applications are very critical because the final pressure can reach 350 MPa and the evaluation of the performance of the machines is strongly connected to the proper operation and performance of the valve itself. The arrangement of cylinders requires generally a certain compactness of valve to withstand high fatigue stresses, but at the same time pressure drop and operating life are very important. In recent years the reliability of the machines has been improving over and over and the customers’ needs are very stringent. Therefore the use of poppet valves has been extended to other cases. In general the mentioned applications are heavy duty services and the simulation of the valves require some coefficients to be used in the differential equations, able to describe the movement of plate/disk or poppet and the flow and related pressure drop through the valves. Such coefficients are often determined in an experimental way in order to have a simulation closer to the real operating conditions. For the flow coefficients it is also possible today to use theoretical programs capable of determining the needed values in a quick and economical way. Some investigations have been carried out to determine the values for certain geometries of poppet valves. The results of the theory have been compared with some experimental tests. The good agreement between the various methods indicates the most suitable procedure to be applied in order to have reliable data. The advantage is evident as the time necessary for the theoretical procedure is faster and less expensive. This is of significant importance at the time of the design and also in case of a need to provide timely technical support for the operating behavior of the valves. Particularly for LDPE, the optimization of all the parameters is strongly necessary. The fatigue stresses of cylinder heads and valve bodies have to match in fact with gas passage turbulence and pressure drop, added to the mechanical behavior of the poppet valve components.

scholarly journals Simulation Study of the Process of Friction in the Working Elements of a Car Braking System at Different Degrees of Wear

2018 ◽  
Vol 12 (3) ◽  
pp. 221-226 ◽  
Author(s):  
Andrzej Borawski
Keyword(s):  
Simulation Study ◽  
Friction Pair ◽  
Experimental Studies ◽  
Real Life ◽  
Operating Conditions ◽  
Heating Process ◽  
Passenger Cars ◽  
The Road ◽  
Emergency Braking ◽  
Braking System

Abstract Among the many elements of a modern vehicle, the braking system is definitely among the most important ones. Health, and, frequently, life, may rest upon the design and reliability of brakes. The most common friction pair used in passenger cars today is a disc which rotates with the road wheel and a cooperating pair of brake pads. The composite material of the pad results in changing tribological properties as the pad wears, which was demonstrated in experimental studies. The change is also facilitated by the harsh operating conditions of brakes (high and rapid temperature changes, water, etc.). This paper looks into how changing tribology reflects on the heating process of disc and pads during braking. And so a simulation study was conducted, as this method makes it possible to measure temperature in any given point and at any time, which is either impossible or extremely difficult in real life conditions. Finite element method analyses were performed for emergency braking events at various initial speeds of the vehicle reflecting the current road speed limits.

Tribological performance characterization of brake friction materials: What test? What coefficient of friction?

2018 ◽  
Vol 233 (1) ◽  
pp. 214-226 ◽  
Author(s):  
Mohamed Kchaou ◽  
Amira Sellami ◽  
Jamal Fajoui ◽  
Recai Kus ◽  
Riadh Elleuch ◽  
...  
Keyword(s):  
Material Properties ◽  
Experimental Methods ◽  
Tribological Performance ◽  
Small Sample ◽  
Large Field ◽  
Friction Materials ◽  
Braking Performance ◽  
Specific Protocol ◽  
Reduced Scale

This article describes and explains the tribological tests and methods for the evaluation of the performance of the brake friction materials. It starts by discussing the particularities of these materials and the variation of characterization tests, which can experimentally simulate many aspects of brake situation but with a large field of tribo-test, from standard to specific protocol. Examples of preparation, procedures, instrumentation, and analysis results for the tribological aspect testing ranging from the scale of vehicle braking performance (by methods including inertia dynamometers, Krauss testing, friction assessment screening test, and Chase testing) to simplified test using reduced-scale prototypes for small-sample friction, are explained. A particular attention is attributed to the discussion of the viability of the friction coefficient report in relation to the material properties and brake compound performance. At the end of this article, the guarantee of the performance output or ranking evaluated by such experimental methods is discussed.

Predicting the Coefficient of Friction in Sliding-Rolling Contacts

1989 ◽  
Vol 111 (2) ◽  
pp. 386-390 ◽  
Author(s):  
Yufeng Li ◽  
Ali Seireg
Keyword(s):  
Surface Roughness ◽  
Coefficient Of Friction ◽  
Thermal Regime ◽  
Surface Coating ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Published Data ◽  
Excellent Correlation ◽  
Rolling Contacts ◽  
The Coefficient Of Friction

This paper deals with the development of a dimensionless empirical formula for calculating the coefficient of friction in sliding-rolling steel on steel contacts under different operating conditions in the thermal regime. The effect of lubrication, surface roughness, and surface coating on friction are considered. The formula shows excellent correlation with the experimental tests conducted by many investigators and provides a unified relationship for all the published data.

scholarly journals Estimation peculiarities of external polymer insulation reliability of gas-filled instrument transformers

2021 ◽  
pp. 3-9
Author(s):  
Liudmyla Zhorniak ◽  
Alexej Afanasiev ◽  
Vitaliy Schus ◽  
Olexij Morozov ◽  
Julia Rudenko
Keyword(s):  
High Voltage ◽  
Accurate Determination ◽  
Experimental Studies ◽  
Experimental Tests ◽  
Operational Reliability ◽  
Current Transformer ◽  
Operating Conditions ◽  
Distribution Law ◽  
Instrument Transformers ◽  
And Performance

In the article, the authors propose a method for estimating the parameters of theoretical distributions for calculating the indicators of operational reliability. In the article, the authors propose a method for estimating the parameters of theoretical distributions for calculating the indicators of the operational reliability of a solid insulating structure of high-voltage devices, which is a supporting insulating cover for high voltage instrument transformers filled with gas as an insulating liquid. This technique makes it possible to estimate the parameters of a new distribution law, which is chosen on the condition that it does not contradict the existing distribution law with its known parameters. The developed technique makes it possible to obtain the values of the indicators of the operational reliability of high-voltage equipment by determining the parameters of theoretical distributions, if the developer is the data of experimental studies or statistical information as a result of monitoring the operation of insulating structures, taking into account the actual operating conditions of such high-voltage devices.  This makes it possible to take into account the influence of external factors and performance characteristics inherent in instrument transformers, both current and voltage. In the proposed methodology, as an example, a supporting insulating casing is considered, which is during operation in the most unfavorable conditions, such as external pollution, humidification, overvoltage, etc. The theoretical conclusions are confirmed by the results of calculations using the example of the design of a current transformer of the ТОГ-362 series. A more accurate determination of the effectiveness of the proposed method for predicting the parameters of theoretical distribution laws can be achieved by performing an additional series of calculations and experimental tests of specific insulating structures. Thus, it was concluded that it is possible to use the results obtained to assess the operational reliability of both gas-filled instrument transformers and similar high-voltage equipment.

Performance Measurements of a 1/6-Scale Model of the 1907 Cornu Rotor

2012 ◽  
Vol 57 (3) ◽  
pp. 1-5
Author(s):  
Benjamin Hance ◽  
J. Gordon Leishman ◽  
Joseph Milluzzo
Keyword(s):  
Aspect Ratio ◽  
Figure Of Merit ◽  
Ground Effect ◽  
Operating Conditions ◽  
Scale Model ◽  
Performance Measurements ◽  
Aerodynamic Efficiency ◽  
Rotor Design ◽  
Average Profile ◽  
And Performance

Measurements of the performance of an approximate 1/6-scale Cornu 1907 rotor system are discussed. The rotor was tested in hover, both in and out of ground effect, over a range of rotational speeds and collective blade pitch angles. The measurements showed that the rotor had low aerodynamic efficiency, with a maximum attainable figure of merit of only about 0.35 for out of ground effect operating conditions. An analysis of the measurements showed that the performance of this rotor is dominated by relatively high induced losses, with an average induced power factor of over two, mainly because of the use of low-aspect-ratio blades. Extrapolation of the performance polar back to zero thrust with the aid of modified momentum theory suggests that the average profile drag coefficient for the blade sections was of the order of 0.1. However, even with the benefits of a proper airfoil section of lower drag, it is shown that without also using a blade design of higher aspect ratio, the figure of merit of the Cornu rotor design could not be improved much above 0.4. The measured results confirm previous modeling assumptions used for the aerodynamic and performance analysis of the Cornu rotor design and conclusions drawn regarding the unfeasibility of successful free flights of the Cornu helicopter.

Amphiphilic Zirconium Phosphate Nanoparticles as Tribo-catalytic Additives of Multi-performance Lubricants

2021 ◽  
pp. 1-8
Author(s):  
Yan Chen ◽  
Xuezhen Wang ◽  
Zehua Han ◽  
Alexander Sinyukov ◽  
Abraham Clearfield ◽  
...  
Keyword(s):  
Material Removal ◽  
Zirconium Phosphate ◽  
Surface Characterization ◽  
Film Growth ◽  
Removal Rate ◽  
The Coefficient Of Friction ◽  
And Performance ◽  
Catalytic Additives

Abstract The advancement of electric vehicles demands lubricants with multifunction and performance. In this research, we investigated amphiphilic a-ZrP nanoparticles as lubricant additives. Experimetns showed that the nanolubricant produced a tribofilm reduced the friction for 40% and wear 90%, while the electrical conductivity remained to be stable during tribotesting. Surface characterization of the tribofilm showed that there was a layered pyrophosphate on the wear track . The in situ impedance study about tribochemical kinetics revealed that the process in formation of a tribofilm involved synergetic growth and wear. During growth, the coefficient of friction increased with continued formation of such a file. During wear, the material removal rate was a function of friction, i.e., the higher the wear rate, the higher the friction coefficient. The competing mechanisms of film growth and wear resulted in an electrically uniformed surface.

Fast X-ray powder diffraction on I11 at Diamond

2011 ◽  
Vol 18 (4) ◽  
pp. 637-648 ◽  
Author(s):  
Stephen P. Thompson ◽  
Julia E. Parker ◽  
Julien Marchal ◽  
Jonathan Potter ◽  
Adrian Birt ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Structural Changes ◽  
Biomimetic Synthesis ◽  
Synthesis Process ◽  
Performance Measurements ◽  
Fully Integrated ◽  
X Ray ◽  
And Performance

The commissioning and performance characterization of a position-sensitive detector designed for fast X-ray powder diffraction experiments on beamline I11 at Diamond Light Source are described. The detecting elements comprise 18 detector-readout modules of MYTHEN-II silicon strip technology tiled to provide 90° coverage in 2θ. The modules are located in a rigid housing custom designed at Diamond with control of the device fully integrated into the beamline data acquisition environment. The detector is mounted on the I11 three-circle powder diffractometer to provide an intrinsic resolution of Δ2θ ≃ 0.004°. The results of commissioning and performance measurements using reference samples (Si and AgI) are presented, along with new results from scientific experiments selected to demonstrate the suitability of this facility for powder diffraction experiments where conventional angle scanning is too slow to capture rapid structural changes. The real-time dehydrogenation of MgH2, a potential hydrogen storage compound, is investigated along with ultrafast high-throughput measurements to determine the crystallite quality of different samples of the metastable carbonate phase vaterite (CaCO3) precipitated and stabilized in the presence of amino acid molecules in a biomimetic synthesis process.

Thickness and Distribution of the Transfer Film in Journal Bearing

2005 ◽  
Author(s):  
Adam Polak ◽  
Janusz Grzybek
Keyword(s):  
Journal Bearing ◽  
Film Formation ◽  
Friction Pair ◽  
Transfer Film ◽  
Operating Conditions ◽  
Formation Processes ◽  
Sliding Speed

Paper presents investigations of the transfer film formation processes in tribological pair: steel journal–plastic bushing. Processes of transfer film formation were examined for different operating conditions of friction pair (pressure, sliding speed and temperature). Conducted tests and examinations enabled characterization of transfer film formation processes in dependence of operating conditions. Obtained results allowed, to determine dependencies between operating conditions and thickness and distribution of the transfer film.

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