Given the current context and the advanced stage of technology, which the braking systems of vehicles have reached, the main purpose of the studies and research is focused on presenting the main tribological aspects that contribute at improving the performance of braking systems, in order to ensure the vehicles’ safety and stability at braking, in any conditions. The performance of the braking system is a key factor for both producers and vehicle passengers, due to safety requirements, everincreasing. Thus, over time, numerous studies and research have been carried on in order to improve the performance of the braking system. In this paper are studied tribological phenomena through those, which contribute to the improvement of the braking system as performance, safety and stability.
For road safety, braking system performance has become a very important requirement for car vehicle manufacturers and passengers. To this end, vehicle designers must understand the characteristics of tribological behavior and the causes of their variation in properties. This paper analyzes the tribological behavior (at friction and wear) of the most recent material couples of the braking disk-pad system affected by their structural change through the implications on the braking system stability, reliability and suitable characterizations. Obtaining information to design a very efficient braking system and assessing the influence of the material’s structural changes on its stability has become a necessity. This has been made possible by using several methods of testing a brake disk-pad couple on various devices intended for this purpose. The materials of the contact surface disk-brake pad with their tribological performance (friction, wear), especially the friction coefficient, present particular importance. Also, system components’ reliability, heat transfer and the noise and vibration of the brake disk-pad couple are vital to the correct operation of the braking system and should be given special attention. The test results obtained define the friction patterns and the influence of structural changes and other environmental factors that can be used in computer analysis.
Molybdenum disulfide (MoS2) is used as a solid lubricant and is well known for its tribological behavior (friction and wear). The tribological properties of the lubricating oil–MoS2 nanoparticles mixture in different conditions of friction are studied using a four-ball tribometer, and the operating conditions of the four balls when immersed can be modeled. The current paper presents a calculating method for the critical sliding velocity (ωcr) and friction maximum torque (Mfmax) depending on the temperature (T) from the contact areas, obviously demonstrating low tribological performances. The film composition formed by friction, the topography, and the morphology of the particles and the friction-and-wear tracks of the balls following experiments using contact surfaces are analyzed and investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscope (TEM). XPS and SEM show that nanoparticles by deposition form a protective and lubricating layer of MoS3, which allows for an increase in the friction pair’s load capacity. MoS2 nanoparticles (n- MoS2 of ~ 40 nm in diameter) compared to the common (commercial) MoS2 particles (c-MoS2 of ~ 1.5 μm in diameter) presented lower friction coefficients and higher wear-resistance values, due to the protective-layer microstructure as an intermediate lubricant between the contact surfaces. Therefore, the present paper reports the tribological properties of the lubricating oil with n-MoS2 as an additive compared to the c-MoS2, and by the application of the friction modeling theory using a Couette flow, it was possible to calculate the temperature, T, when the friction torque, Mf, was at its maximum, the basis on which the value of its sliding velocity, ω, was obtained corresponding to the contact areas of the four-ball system.
The vehicles number continuously growing lead to increasingly intense and congested traffic and it will additionally demand the braking system, and drivers behave more aggressively and as result is required that the braking system to be durable and efficient. For this is necessary the study the braking system behavior in conditions of intense and moderate traffic to increase the safety of traffic participants, respectively to demonstrate the need for more frequent replacement of some braking system elements. Thus, on a vehicle were performed a series of successive tests, through which the degree of wear of the brake pads and discs was monitored periodically and as a result the efficiency evolution of the braking system. The tests were carried out both in laboratory (on dynamometer) and in traffic to establish the efficiency of the braking system according to some parameters considered essential. The experimental tests showed that the recommendations regarding the frequency of replacement of brake pads and disks are inconsistent with their actual wear. Therefore, the aim of this paper is the establishment of the braking system efficiency of an auto-vehicle, subject to testing depending on the auto-vehicle mass, travel speed, distance driven, and braking time, based on experimental on stand and in-traffic tests, according the road safety regulations.
The growing number of vehicles leads to increasingly intense and congested traffic, which will additionally put demand on the braking system, and drivers behave more aggressively. As a result, the braking system must be durable and efficient. For this purpose, the study of the braking system behavior in conditions of intense and moderate traffic is required to increase the safety of traffic participants—respectively, to demonstrate the need for more frequent replacement of some braking system elements. Thus, a series of successive tests were performed on a vehicle, through which the degree of wear of the brake pads and discs was monitored periodically, resulting in the efficiency evolution of the braking system. The tests were carried out both in the laboratory (on a dynamometer) and in traffic to establish the efficiency of the braking system according to some parameters considered essential. The experimental tests showed that the recommendations regarding the frequency of replacement of brake pads and discs are inconsistent with their actual wear. Therefore, the aim of this paper is to establish the braking system efficiency of a vehicle, subject to testing depending on the vehicle mass, travel speed, distance driven, and braking time, based on experimental tests, on stand and in-traffic, according to the road safety regulations. The validation of the braking system efficiency of the tested vehicle was done by measuring the stopping distance and time in relation to the initial speed, the mass of the vehicle, the number of kilometers traveled, and conditions of intense and moderate traffic.
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