Browse Topic: Brake fluids
The braking system in a vehicle is one of the most crucial parts for proper and safe operation. It is required to slow down or stop the vehicle and work by converting the kinetic energy of the wheel to heat. It is essential to dissipate the generated heat for optimal working and the long life of the disc brakes. Heat generated is due to friction between the brake pad and disc. Due to overheating of brakes due to prolonged braking and heavy braking, brake fade occurs. This leads to boiling of the brake fluid, gassing, and glazing of brake pads, hence reducing braking performance. Therefore, in this study, we used computer simulations to determine the best design that allows for the most heat dissipation by analyzing four different conventional disc brake designs. It was found that the slotted disc brake design had the maximum value of heat transfer coefficient (87.2% more than that of the vented disc brake) and also correspondingly the most decrease in the maximum temperature (39.56% decrease than that of the vented disc brake). We used CFD to study the effects of airflow on convection and FEA for thermal analysis. This study aims to understand the heat transport behaviour, in general, and heat dissipation disc brakes in a comprehensive manner, in particular.
This SAE Recommend Practice specifies a method for measuring the deflection of friction materials and disc brake pad assemblies in a manner more consistent with classical material compressive strain testing. This SAE test method differs from SAE J2468 in the preload and maximum load applied to the test sample when deflection is measured. It adopts the material applied stress levels found in ISO 6310 (0.5 to 8.0 MPa) using a 25 mm diameter flat plunger.
The noise and vibration are directly related to the perceived quality of a vehicle and it is crucial that the manufacturers focus their efforts to reduce that. When an unusual noise appears, it is a great challenge to define an approach for understanding the phenomenon, identifying the cause and then defining a solution to reduce its effect. A “knocking noise” coming from the brake rigid pipes is perceived while driving the vehicle in a cobbled pavement at low speed and it coincides with the closure of brake system module inlet valves. When a valve closes quickly, there is a sudden change in the flow velocity, which generates a pressure transient in the brake fluid inducing vibrations in the rigid pipes. The pressure transient can be minimized by reducing the speed at which the pressure waves travel in the pipe. The bulk modulus, the density of the fluid, the velocity of valve closing, the Young’s modulus and the dimensions of the pipes, determine the wave speed. The objective of this work is, first to correlate the phenomenon with the theory regarding the transient flow by presenting the measurements of pressure change in the brake lines during the brake unit valves actuation. Afterwards, evaluate the experimental results of changing the variables that affect the wave speed, and its influence in the noise perception. At the end, show how the application of a hybrid pipe solution, which reduces the Young’s modulus of the brake line, can reduce the pressure transient as well as the “knocking noise”.
The noise and vibration are directly related to the perceived quality of a vehicle and it is crucial that the manufacturers focus their efforts to reduce that. When an unusual noise appears, it is a great challenge to define an approach for understanding the phenomenon, identifying the cause and then defining a solution to reduce its effect. A “knocking noise” coming from the brake rigid pipes is perceived while driving the vehicle in a cobbled pavement at low speed and it coincides with the closure of brake system module inlet valves. When a valve closes quickly, there is a sudden change in the flow velocity, which generates a pressure transient in the brake fluid inducing vibrations in the rigid pipes. The pressure transient can be minimized by reducing the speed at which the pressure waves travel in the pipe. The bulk modulus, the density of the fluid, the velocity of valve closing, the Young’s modulus and the dimensions of the pipes, determine the wave speed. The objective of this work is, first to correlate the phenomenon with the theory regarding the transient flow by presenting the measurements of pressure change in the brake lines during the brake unit valves actuation. Afterwards, evaluate the experimental results of changing the variables that affect the wave speed, and its influence in the noise perception. At the end, show how the application of a hybrid pipe solution, which reduces the Young’s modulus of the brake line, can reduce the pressure transient as well as the “knocking noise”.
This article describes experimental research results of the inductive sensor of the electropneumatic clutch control system for the mechanical transmission. Inductive sensors are used to determine the position of the car body, the position of the controls and the position of the rod of the clutch control actuator. The design of the clutch pedal position sensor is proposed, which can be brought into line with the master cylinder to unify the clutch control systems. Complete unification of the automated electropneumatic clutch control system for trucks will allow creating modifications in which it is possible to completely abandon the use of brake fluid in the drive, which will improve the ergonomic and environmental performance of the vehicle. The advantages of such sensors are the ability to receive a signal in digital form without additional converters, the ability to work using only two wires, no contact between moving parts, resistance to aggressive environments and compact size. The disadvantage is the influence of ambient temperature on the electrical parameters of the sensor (inductance and resistance) and on the measuring circuit of the electronic control unit. The temperature effect creates significant deviations in the data received by the processor. During the laboratory experimental study, the influence of ambient temperature on the measurement data in the temperature range of -45°С + 45°С was determined separately for the sensor and for the sensor with the measuring system. Significant nonlinearity of the characteristic was determined. The effect of spontaneous operation of the clutch control system during changes in ambient temperature was experimentally obtained. The influence of temperature change on the measuring range of the inductive sensor is also revealed. The transfer characteristic of the sensor (% /mm) is determined. The approach that provides a stable transfer characteristic within the specified temperature range is proposed.
Hydraulic brake pipes are responsible for fluid flows and as consequence the proper functionality of the most important safety system in passenger vehicles. Even so, this component has no much development since it was applied in the 1930s. In fact, the brake pipes can be particularly vulnerable components, being mainly in an exposed condition under the vehicle and near of components with relative movement. Externally it needs to survive a wide range of environmental conditions whereas internally it must withstand pressurized brake fluid. Brake pipes failures is an obvious safety hazard. Using simulations with car body, burst and corrosion bench test and multiple linear regression, this paper attempts to present, basing the pipes lifetime in the burst bench test, how the pipes are really vulnerable or not to damages caused by interference with other components, corrosion or even in frequent abrasion. As well as pipes behavior during interference, how such as corrosion in spot exposed regions degrades the pipes, how such as quantity, type and bending location influence the lifetime, which are the most relevant damage factors, how the damage usually occurs on vehicles, and specify an equation capable of projecting burst pressure considering the damage dimensions as variables. This paper shows the most vulnerable regions and pipes diameter most affected, clarify how the bends impact on the pipes lifetime and defines a equation able to correlate a pipe lifetime prediction based on the damage dimensions.
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. The rig test of the hollow cylinder was carried out in order to secure the brake consumption amount curve whose results were used for the criterion of the parametric simulations using Tait equation to estimate the property of the brake fluid with the bulk modulus of 19,535 bar and 0.00016%. It was observed that the experimental curve data from the rig test of the hollow cylinder is divided into two regions with high and low compressibility, and more volume change in the low region below 1 bar is required to gain the same pressure variation due to the compression of the tiny air bubbles. The improved design of the nut-spindle with 6 holes in circumferential direction was drawn for the better removal of the trapped air. The simulation of the improved model showed the manual bleeding performance improvements of 18.9% than the baseline model due to the holes effect on circulation of the trapped air. It was experimentally verified that the air bubbles from their visualization are compressed to form the smaller size bubbles in the process of pressurization and gathered on the topmost side, whereas they are again expanded to form the larger size bubbles in the process of pressure release and spread into the wider space. The bleeding performance for the improved model was also experimentally verified to be effective up to approximately 51% through the caliper performance tester.
Motor vehicle brake fluid must conform to the requirements of SAE J1703 or J1704, not only when manufactured, but also after extended storage in any commercial packaging container. The purpose of this SAE Information Report is to generate an awareness of the major problems involved in the storage of brake fluids and, to some extent, provide means of circumventing them. It is also the purpose of this document to relate to experience and to test data accumulated and to list certain conclusions which should aid in the proper selection of containers for brake fluid.
This procedure is applicable to squeal type noise occurrences for passenger car and light truck type vehicles that are used under conventional operating conditions. For the purposes of this test procedure, squeal is defined as occurring between 900 and 18 000 Hz.
One potential fire ignition source in a motor vehicle is the hot surfaces on the engine exhaust system. These hot surfaces can come into contact with combustible and flammable liquids (such as engine oil, transmission fluid, brake fluid, gasoline, or Diesel fuel) due to a fluid leak, or during a vehicle collision. If the surface temperature is higher than the hot surface ignition temperature of the combustible or flammable liquid in a given geometry, a fire can potentially ignite and propagate. In addition to automotive fluids, another potential fuel in post-collision vehicle fires is grass, leaves, or other vegetation. Studies of hot surface ignition of dried vegetation have found that ignition depends on the type of vegetation, surface temperature, duration of contact, and ambient conditions such as temperature and wind speed. Ignition can occur at surface temperatures as low as 300 °C, if the vegetation is in contact with the surface for 10 minutes or longer. At surface temperatures of 400 °C, ignition can occur in 3 minutes, and at surface temperatures of 500 °C, ignition can occur in a few seconds. We made measurements of the surface temperature at various locations along the exhaust system of a passenger vehicle, including on the catalytic converter, under different transient conditions. The temperatures were measured using thermocouples welded to the exhaust system. The tests show that the maximum external surfaces temperatures occur under transient conditions after the vehicle comes to a sudden stop. Thus, testing that only measures steady-state temperatures or temperatures while the vehicle is moving will not necessarily capture the worst-case temperatures. For the vehicle tested, exhaust system components can reach temperatures of 400 °C and these temperatures can be sustained for minutes after the vehicle stops, and thus are capable of igniting dried vegetation.
This SAE Standard specifies a method for measuring the deflection of friction materials, noise insulators, and disc brake pad assemblies to be used in road vehicles with a Gross Vehicle Weight Rating below 4336 kg. This part of the SAE J3079 includes the test for deflection and creep at various pressures under ambient temperature conditions. This SAE test method differs from SAE J2468 and ISO 6310 in the preload and maximum load applied to the test sample when deflection is measured. It also introduces additional measurements such as for deflection offset, hysteresis, and creep.
Items per page:
50
1 – 50 of 293