Browse Topic: Brake lines
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”.
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.
This SAE Recommended Practice is intended for qualification testing for brake drums used on highway commercial vehicles with air brakes using an inertia-dynamometer procedure. This Recommended Practice consists of two distinct tests: Part A - durability and speed maintenance test, and Part B - heat check drag sequence test. Each test can be considered to be an independent evaluation of the brake drum which tests different properties.
Keeping it simple is a key component in turning around the fortunes of Kettering University's Formula SAE team. KETTERING UNIVERSITY HAS A LONG-STANDING HISTORY with deep ties to the automotive industry. Formerly known as General Motors Institute (GMI), the university is known for developing engineers with an automotive focus, and the students of the Formula SAE team on campus take that to heart. They are passionate about cars, and having the chance to design, build, and compete their own product is a learning experience unlike any other. As of late, Kettering University Formula SAE has been going through a sort of transition. In the 2016 season, there was a large gap between young and old members; the team was predominately graduating seniors and incoming freshmen, with few class ranks in between. The interest was there, but there was a lot of knowledge that needed to be transferred in a very short amount of time. This created a very foggy outlook for a program that has had success in the past. Previous members laid the groundwork for a program that could thrive, but it would take a lot of effort to maintain after a rough season rattled much of the team.
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.
Specific gravity is a nondestructive test used as a quality control check of the consistency of formulation and processing of brake lining. The specific gravity and the range of specific gravity are peculiar to each formulation and, therefore, the acceptable values or range must be established for each formulation by the manufacturer. Specific gravity alone shows nothing about a materials in use performance. The specific gravity of sintered metal powder friction materials, particularly those which have steel backing members, is usually determined somewhat differently. Reference ASTM B 376.
Hydraulic Load sensing brake valves are used in vehicles from a long time in the market. They proportionate the rear brake line pressure according to the rear axle load in order to avoid the rear wheel lock during braking. During the actual test of the Hydraulic load sensing valve on a subject vehicle, there was drop in performance against its expected peak brake performance. In the current work a detailed analysis is made to understand the sensitivity of the load sensing valve & its effect on the vehicle performance. The parameters affecting the valve sensitivity along with vehicle level factors affecting the performance are analysed during the work.
This Recommended Practice provides a road test procedure for trucks and buses, to evaluate their compliance with Federal Motor Vehicle Safety Standard (FMVSS) 121; Air Brake Systems. Units of measure are English in lieu of metric to be consistent with FMVSS 121.
The transient thermo-mechanical coupling dynamic model of ventilated disc brake with asymmetrical outer and inner thickness was established by means of Msc-marc software. In the model, pad backplate is simplified as a rigid surface with the same shape of brake lining and is bonded together with brake lining. Control node is associated with the rigid surface and the equivalent force that replaces the pressure is applied on the control nodes, of which the degrees of freedom in radial and rotational directions are constrained. With distribution characteristics of disc temperature field, normal stress field and lateral thermo-elastic deformation and thickness for the evaluation, the impacts of brake pad constraints on brake thermomechanical coupling characteristics were analyzed. The simulation results show that the brake pad back plate is an important structure in brake thermo-mechanical coupling analysis, which can’t be ignored in simulation computing. The brake pad constraints can affect thermo-mechanical coupling characteristics of disc brake directly.
Brake linings have complex microstructure and consist of different components. Fast growing automotive industry requires new brake lining materials to be developed at considerably shorter time periods. The purpose of this research was to generate the knowledge for optimizing of brake friction materials formula with mathematical methods which can result in minimizing the number of experiments/test, saving development time and costs with optimal friction performance of brakes. A combination of processing methods, raw materials and testing supported with the Artificial Neural Network (ANN) and Taguchi design of experiment (DOE) allowed achieving excellent results in a very short time period. Friction performance and wear data from a series of Friction Assessment and Screening Test (FAST) were used to train an artificial neural network, which was used to optimize the formulations. The averaged COF, COF variation and wear were used as the output parameters. Weight percentage of raw materials denoted as an input parameter and these data were used to train ANN. A two layer feedforward ANN with back propagation was used in this study. Back propagation learning algorithm can be divided into two phases: i) propagation and ii) weight update. The friction performance of the optimized friction materials was considerably better when compared to the baseline commercial brake lining materials. This method can be applied to development of any type of complex friction materials.
The brake wear contribution to the environmental pollution has been extensively discussed, with major focus on asbestos and heavy metals released to the environment. Only limited attention was paid to released organic compounds generated during friction processes, although the organic and carbonaceous components are not the minor part in brake lining formulations. Friction processes in brakes are associated with relatively high temperatures and high pressures on the friction surfaces which relates to the thermal decomposition of the organic components in friction materials and to brake lining thermal fade. Thus, this study focuses on the identification of organic compounds released from a model low metallic brake material. Several methods were used for the analysis: GC/MS screening of brake pad samples, brake wear debris and carbonaceous raw materials used in formulations of model pads; GC/MS screening of brake pad samples pyrolyzed at 300, 750, and 1000°C, respectively, and FTIR analysis of brake pads and their wear debris. Higher quantity of organic compounds was identified in extract of the milled brake pad composite compared to the wear debris. More than 80 organic compounds were identified to be potentially released during braking. The major constituents were phenols, aliphatic and aromatic hydrocarbons, and their derivatives. Some of the identified compounds are known to have adverse effects even with mutagenic and carcinogenic potency to humans.
In engineering development, simulation methods are frequently used to perform thermal and mechanical stress components analysis. In brake systems, where the components are exposed to mechanical and thermal loads, the numerical analysis is very helpful. Once a numerical model for brake assembly is available, it will be possible to understand the effects of successive brake applications on the temperature distribution in drum brake’s friction materials. This is a fundamental aspect to determine, for instance, the thermal stress distribution which is related to the warming and cooling of the brakes. In this work, an analytical solution to calculate stabilized temperature was used to establish a heat flux through a pneumatic S cam drum brake’s friction material applied to a numerical model in a finite element analysis. After including the effects of the riveting process and the warming in one of the 17 t bus front brake lining, areas where the stresses vary with considerable amplitudes during temperature increase were identified. The study has indicated that friction material can be submitted to cyclic loads that can cause damage accumulation. These areas have corresponded to local regions of brake linings where historically failures occur during development tests. Also, it was possible to compare results from numerical model to vehicle’s experimental data and understand its proximity to real braking events. By the application of the methodology and using the numerical model proposed in this work, it will be possible to contribute considerably for a more accurate design of the friction material.
This SAE Recommended Practice establishes a method of testing the structural integrity of the brake system of all new trucks, buses, and combination vehicles designed for roadway use and falling in the following classifications: a Truck and Bus—Over 4500 kg (10 000 lb) GVWR b Combination vehicle—Towing vehicle over 4500 kg (10 000 lb) GVWR The test consists of two distinct tests: a Structural Endurance Test followed by a Structural Ultimate Strength Test. NOTE—These two tests originated from separate procedures, and were combined in this Recommended Practice. Each test can be considered to be an independent evaluation of the service brake’s structure. Based on time available, cost limitations, and the desired evaluation and historical data available, either of these tests could be considered as a complete evaluation of the brake’s structure.
In engineering development, simulation methods are frequently used to perform thermal and mechanical stress components analysis. In brake systems, where the components are exposed to mechanical and thermal loads, the numerical analysis is very helpful. Once a numerical model for brake assembly is available, it will be possible to understand the effects of successive brake applications on the temperature distribution in drum brake's friction materials. This is a fundamental aspect to determine, for instance, the thermal stress distribution which is related to the warming and cooling of the brakes. In this work, an analytical solution to calculate stabilized temperature was used to establish a heat flux through a pneumatic S cam drum brake's friction material applied to a numerical model in a finite element analysis. After including the effects of the riveting process and the warming in one of the 17 t bus front brake lining, areas where the stresses vary with considerable amplitudes during temperature increase were identified. The study has indicated that friction material can be submitted to cyclic loads that can cause damage accumulation. These areas have corresponded to local regions of brake linings where historically failures occur during development tests. Also, it was possible to compare results from numerical model to vehicle's experimental data and understand its proximity to real braking events. By the application of the methodology and using the numerical model proposed in this work, it will be possible to contribute considerably for a more accurate design of the friction material.
The study and prevention of unstable vibration is a challenging task for vehicle industry. Improving predicting accuracy of braking squeal model is of great concern. Closed-loop coupling disc brake model is widely used in complex eigenvalue analysis and further analysis. The coupling stiffness of disc rotor and pads is one of the most important parameters in the model. But in most studies the stiffness is calculated by simple static force-deformation simulation. In this paper, a closed-loop coupling disc brake model is built. Initial values of coupling stiffness are estimated from static calculation. Experiment modal analysis of stationary disc brake system with brake line pressure and brake torques applied is conducted. Then an optimization process is initiated to minimize the differences between modal frequencies predicted by the stationary model and those from test. Thus model parameters more close to reality are found. Unstable mode prediction results using parameters before / after optimization are compared with those from brake noise bench test. The results after parameter optimization are in good correlation with test result and illustrate obvious improvement of predicting accuracy. Finally, the presented method is used to study the relationship between the coupling stiffness and brake conditions, i.e. brake-line pressure. The result shows accordant with literature.
This SAE Recommended Practice provides instructions and test procedures for air braked trailers and dollies used in single and multiple trailer combinations on highway. This document is not intended for off-highway application.
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