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Tribology in the Automotive Sector
Published in Jitendra Kumar Katiyar, Alessandro Ruggiero, T.V.V.L.N. Rao, J. Paulo Davim, Industrial Tribology, 2023
Sudheer Reddy Beyanagari, P. Kumaravelu, Dhiraj Kumar Reddy Gongati, Yashwanth Maddini, S. Arulvel, Jayakrishna Kandasamy
Brakes are the devices used to slow down or stop a vehicle. Braking is required to reverse the vehicle’s acceleration and lead it rearward. During the braking operation, the vehicle’s kinetic energy is converted to heat and dispersed into the air; thus, the brakes are more important in vehicle control. The braking system acts on the wheels; it is controlled by a foot pedal/hand. Friction resists the motion of the vehicle, when a moving vehicle is abruptly stopped by applying brakes. The motion of the brake shoes/pads creates friction between the brakes and the braking drum/disc and then tyre-road friction slows or stops vehicle motion. In the present scenario, the majority of low-weight vehicles employ disc brakes rather than drum brakes [31]. Thus, the tribological characteristics of discs and pads have a considerable impact on the braking process. The discs are often made of grey cast iron due to its excellent wear and frictional resistance, high thermal efficiency, and anti-vibration characteristics, but they are heavy in weight. So, discs made with composite materials have developed, particularly for sports cars. Brake friction components may wear out in many ways. The major prevalent kind of wear is abrasion, which occurs when friction parts rub against each other. Scratching, micro-grinding, and groove development cause the material loss of the pads.
Energy Conservation and Efficiency
Published in Robert Ehrlich, Harold A. Geller, John R. Cressman, Renewable Energy, 2023
Robert Ehrlich, Harold A. Geller, John R. Cressman
In normal braking systems, the kinetic energy of a car is transformed into heat by friction in the brakes as the car is brought to a stop. In contrast, regenerative brakes use the initial kinetic energy of the vehicle to power a generator whose electricity is then stored in the car battery and not wasted. Some hybrid (combined gas and electric) vehicles already use regenerative brakes, which are a major reason for their better gas mileage. Apparently, the key to getting the biggest energy recovery using regenerative braking is to come to a stop very slowly whenever possible, because the current generated depends on how quickly you decelerate, and there is a maximum charging current that the car battery can handle. Regenerative shock absorbers use the up and down motion of the vehicle to generate electricity (and, in the process, cushion the oscillations). Regenerative shocks are another energy-recovery system, but they have much less potential than regenerative brakes—at least for a passenger vehicle on smooth terrain. However, there are applications—including military vehicles traveling on dirt roads—where the fuel efficiency can be improved by up to 10% through their use.
Hybrid Electric Vehicles
Published in Ali Emadi, Handbook of Automotive Power Electronics and Motor Drives, 2017
Regenerative braking, or energy recuperation, is the principal means through which kinetic energy of the vehicle is returned to electric energy storage rather than burned off as heat in the brake pads. But there are practical limits to how much and how fast regenerative braking can be applied. Smooth and seamless brake feel is the result of a fine balance between M/G energy recuperation and the vehicle’s foundation brakes. The best brake system for a hybrid is what is known as series regenerative braking system (RBS). With series RBS the M/G extracts braking energy without application of the service brakes, then when higher braking forces are required, or if the brake pedal is depressed faster than a prescribed threshold, the service brakes are engaged so that total braking effort is delivered. A less costly and less efficient approach is parallel RBS. With parallel RBS the vehicle’s service brakes and M/G retarding torque are managed simultaneously to deliver the desired total braking effort. Parallel RBS can be envisioned as M/G braking the front axle and foundation brakes on the rear axle. The vehicle’s antilock brake system (ABS) controller then manages the distribution of front-rear braking efforts so that vehicle longitudinal stability is not lost.
Experimental analysis of the heat transfer generated during the operation of an automotive disc brake
Published in Australian Journal of Mechanical Engineering, 2023
R. A. García-León, G. Guerrero-Gómez, N. Afanador-García
Disc brakes are fundamental elements to maintain manoeuverability and, above all, safety in any vehicle, whether it is rotary or linear, and that of its occupants. Braking systems work by taking advantage of friction to slow down the moving vehicle through mechanical contact between two surfaces (pad and disc brake). There are currently various types of brakes, depending on the application: drum, band, disc, and conical. In particular, for the automotive sector, the most common is the disc auto-ventilated type in the front part and the drum type in the rear part (García-León, Flórez-Solano, and Acevedo-Peñaloza 2018; Asim 2014). Disc brakes differ from other types in that the applied force is normal to the disc herd and not radial, as in drum and band brakes. Another characteristic is that the friction moment does not help the actuation moment (self-energising effect), as occurs in drum and bevel brakes. This behaviour allows slight changes in the friction coefficient not to affect the braking force required to dramatically stop the car. For example, a 30% variation in the friction coefficient, which is a normal condition in humid environments, causes an increase in the force of 50%. That behaviour is why the disc brakes have occupied an important place in the automotive industry, especially in the commercial vehicle market (Wahlström 2011; Blau 2001).
Finite element analysis (FEA) of frictional contact phenomenon on vehicle braking system
Published in Mechanics Based Design of Structures and Machines, 2022
Ali Belhocine, Oday Ibraheem Abdullah
During active braking process of moving vehicle, its kinetic energy is converted to heat energy by dry friction between the two parts (disk and brake pads) producing a distribution of heat flux on both sides of the disk. The general formula for calculating the initial flux entering the automotive brake disk can be expressed as follows (Reimpel 1998), this equation is detailed and described as (Belhocine and Wan Omar 2018b): where g is the acceleration of gravity (9.81) (ms−2), a is the vehicle deceleration (ms−2), z = a/g is the braking efficiency.
Investigation on the intermittent braking strategy of high-speed train
Published in Numerical Heat Transfer, Part A: Applications, 2022
Jianyong Zuo, Xueping Wang, Sufen Zhou, Fan Yang
The essence of disk brake is the friction between the brake disk and the friction blocks of the pad, which transforms the kinetic energy into the heat energy. The main influence factors of friction heat are the braking speed and the brake pressure. In order to optimize the braking performance of the train, a brake force control mode based on the braking deceleration feedback control was proposed [26–28]. It is the braking deceleration that was used as a feedback value, and the braking force was adjusted according to the difference between the actual deceleration value and the target value. The control mode has been verified in bench test.