The brake system is the most important equipment for ensuring the safety of vehicles. Disc brakes have been increasingly used in passenger cars for sixty years. Later, they were used in motorcycles. Big brake kits are used to slow the vehicle down, and the kinetic energy of the moving the sliding friction between the brake discs and the brake pads.
The operation of the brake system affects the stability and handling of the car. This is especially important for two-wheeled vehicles. Vehicles of this type are characterized by sensitivity to effective braking. In general, motorcycles and bicycles have separate front and rear brake systems that require operator balancing to achieve effective braking.
As a result, bicycles and motorcycles do not remain stable in an upright position, for example, after the appearance of excessive locking of the front wheels and skidding. The ability to control traffic is sensitive to surface conditions such as potholes, wet or oily roads. In addition, bicycle tires tend to have a reduced road contact area compared to cars.
The traction schemes and the trains used to make them may be suitable for a limited set of road conditions. Motorcycle braking involves driver control tasks that can be significantly more complex than in the case of cars. The correspondence between the skills of the operator and the properties of the vehicle is more important for safety in the case of a motorcycle and bicycles than a car. As usual, the experienced rider made the most of the front brake.
However, apparently due to a lack of confidence in front-wheel braking control, novice riders used the rear brake to a greater extent. Due to the place where it is assembled, the brake disc is exposed to external factors. This results in the sensitivity of the torque efficiency to the presence of water on the disc surface. Therefore, the brake disc system must be characterized by stable friction and properties in various conditions as follows from the above.
Brake discs
The difference between the brake systems is the mechanism and the components used in the assembly of the system. All of them use friction materials. Performance brake pads are usually pressed against the rotating brake disc. This will slow down the car and stop the movement. The basic geometry of the brake disc can be divided into two main types: solid disc brake and ventilated disc brake. The classification is based on their constructive form. It may have a vented geometry, or it may not have a vented geometry.
A solid disc brake is a flat surface that has no incisions or grooves in the disc. This design form had a larger contact surface area during braking compared to the ventilated disc brake. This tends to have more localized thermoelastic instability at the contact sites. Since the solid-state drive does not have a suitable vented opening that can help dissipate the heat from friction when braking into the environment, some problems arise. Thermoelastic instability can cause the phenomenon of brake damping and pad glazing. The geometry of ventilated disc brakes has been extensively researched in the industry. The geometry properties were compared with a solid disc brake.
A vented disc brake is lighter than a solid one. Another feature is the convective heat transfer, which is also better due to the advantage of the ventilation hall. Kang and Cho studied the effect of the disc brake geometry on the heat dissipation characteristics. Their analysis showed that a vented disc has better braking performance in terms of heat dissipation compared to a solid disc. Also, at a lower speed, the vented disk can be more manageable. It can provide a suitable torque value during braking.
Some researchers link the design of the vent geometry to aerodynamic cooling. The airflow can increase the braking efficiency during braking. In addition, the shape of the cross-section plays an important role in the braking performance. The ventilated disc brake has gained more advantages over the solid disc. However, it has some disadvantages, such as lower heat capacity and a higher temperature rise when braking is applied again.
Therefore, when designing and selecting a ventilated disc, its heat capacity and thermal deformation coefficient should also be taken into account to optimize the design of the brake disc. During the braking process, the friction force in the contact area of the brake pad and the brake disc causes wear on the contact area. The wear behavior affects the coefficient of friction that destroyed the contact zone.
The design of the brake disc geometry should be aimed at extending the life cycle of the disc. The friction force occurs due to mechanical action and intermolecular force between the friction surfaces of the pad and the disk Rotors.
The friction surface is characterized by a large number of micro picks or depressions. Micro-peaks are commonly referred to as bumps. The mechanical force involved micro-peaks and troughs connected. They lead to deformation and shifting of irregularities. The interaction of the unevenness with the double surfaces causes plowing on the friction surfaces. As for the difficult road conditions, vehicles experience different braking modes. During prolonged downhill braking and repeated high-speed braking, friction heating can significantly increase the temperature of the friction pair.
Many studies have shown that such overheating can lead to a deterioration in the coefficient of friction in the brake, increased wear of the brake pad, thermal cracking, shaking, and screeching of the brake system due to uneven thermal deformation of the brake disc. Thus, the effective cooling of the brake disc is significant to ensure the safety and comfort of the brakes, especially for modern vehicles.
This tribosystem is very complex and variable, and despite many studies conducted on it, it is still not fully understood and understood.
Conclusions
The brake system is the most important security equipment for vehicles, so it is important to keep an eye on it and make bleeding brakes from professionals brakes-shop.com. To slow down the car, the moving vehicle’s kinetic energy is converted into thermal energy using the sliding friction between the brake discs and the brake pads. The operation of the brake system affects the stability and handling of the car. This is especially important for two-wheeled vehicles.
The measurements carried out on the test bench made it possible to compare the tribological characteristics of two brake discs of different geometries. The disks differed in the diameter and location of the air vents. Changing operating conditions as a result of environmental pollution entering the surface of the disc can significantly impact the change in the coefficient of friction and, consequently, the braking performance.
Based on the conducted research, the following conclusions can be drawn:
- The most significant factor determining the value of the coefficient of friction of a pair of brake pads and a disc is the temperature of the brake disc. In the estimated range of variability, this caused a change in the coefficient of friction of up to 15%.
- Regardless of the disk geometry, an increase in the value of the coefficient of friction was observed with an increase in the sliding speed. In the range of speed changes from 0.1 to 0.5 m, the difference exceeded 15%.
- The geometry of the brake disc can have a significant impact on maintaining the braking performance in the case of wet discs. It is established that in this case, the differences in the values of the coefficient of friction can reach 30%. Furthermore, their geometry also determines the stability of the coefficient of friction when the sliding speed changes. This is due to the ability to remove water from the contact area of the disc and the pad.
