Browse Topic: Brake shoes
The use of drum brakes in Battery Electric Vehicles (BEVs) offers numerous benefits, including energy efficiency, reduced brake dust emissions, and reliable performance under challenging weather conditions. The capability of regenerative braking reduces the friction brake application frequency in BEVs and therefore the brakes can be prone to corrosion and performance degradation especially considering conventional disc brake systems. The closed design of a drum brake prevents corrosion of the friction-components by sealing out water, dirt or snow. A common sealing concept is performed with a labyrinth between the gap of the rotating drum and the axle mounted backplate. A hermetical isolation of water and snow ingress into the drum cannot be achieved with this concept, so additional aerodynamic measures are necessary to deflect the air/water path and protect the inner brake components. Additionally, interfaces like wheel cylinders, electric park brake parts, brake shoe pins, and axle mountings can potentially lead to leaks on the backplate. This study highlights the impact of water/snow ingress on the example of a frozen parking brake during cold climate on-road testing. Through scientific investigation using the state-of-the-art fluorescence method, drum leakages were visualized, and the extent of water ingress was measured. Multiple multiphase CFD simulations supported the design phase of the aerodynamic measures. Subsequently, the vehicle was cooled down to -10 °C to simulate the cold climate test conditions. The frozen parking brake situation could be reproduced with this method, and beneficial aerodynamic and sealing measures were extrapolated to avoid the drum brake from freezing. The tests were conducted in the FKFS Thermal Wind Tunnel, a wind tunnel comprising a two-axle-dynamometer and water irrigation systems with UV illumination.
This SAE Recommended Practice is intended for measuring the static brake torque performance of a pnuematically actuated brake assembly, friction material, and drum/disc combination on an inertia brake dynamometer.
This study aims to present a numerical structural validation procedure for the drum brake spider component. To implement the procedure, the ANSA, ABAQUS, Fe-Safe, and Minitab engineering software were used for stress analysis, fatigue life calculation, and statistical validation using Weibull distribution. The results obtained from these tools allowed us to determine with acceptable error the spot failure of the component and the number of cycles until the occurrence of the failure. The input data to support the pre-processing of the numerical model and obtain the virtual results were determined from the application and analysis of the following methods: determination of the stress strain curve of the Spheroidal Graphite Iron (SG) material of the component, applied to Theory of Critical Distance (TCD) of fracture mechanics and evaluation of the behavior of Nodular Cast Iron under fatigue life. Given the non-linear characteristics under the conditions of use, the need for correction of numerical elastoplasticity was evaluated. The results of the virtual analysis were compared with experimental data collected in an accelerated durability bench, specific for the component under study, in order to validate the method. The procedure presented in this work proved to be effective, obtaining an error of -0.0039% in the fatigue life estimate compared to the experimentally defined target, and an error of 0.0476% in the maximum main stress estimated in comparison with the experimental stress, allowing the use of this procedure as a form of numerical validation of the component.
The aim of this paper was the proposal of a numerical procedure for the structural evaluation and durability validation of brake shoes, employing fatigue and finite element softwares that are able to predict the failure locations (and number of cycles to failure) with acceptable accuracy. The software Abaqus was used in the calculation of the stress and strain fields whereas the software fe-safe was employed in the evaluation of fatigue life. Accelerated tests were performed on a bench test that has been designed to match the operating conditions of the vehicles were the brake shoes are assembled. In those cases where only local plasticity is expected (rather than generalized plasticity) the procedure can somewhat be simplified by running linear elastic finite element analysis (instead of full non-linear), which is often called pseudo-elastic analysis [1]. Then the pseudo stresses and strains are corrected at post-processing time by means of the Neuber’s rule and Ramberg-Osgood equation [2]. The fractographies of the tested components suggest brittle failure mode, which requires a method like SWT (Smith-Watson-Topper) for the mean stress correction [10]. The full brake assembly was considered in the simulations. All the contacts are non-linear and the material of the brake lining is orthotropic. In the present context experimental life to failure is defined as the arithmetic mean of the failed samples (there were three of them). The numerical and experimental results (in terms of life) differ by no more than 52%, and the failure locations correlate really well. The developed numerical procedure has shown to be sufficiently accurate to replace the experimental tests. Therefore it can be used in a more comprehensive study where the sensitivity to geometry, material and loads can be investigated.
The static coefficient of friction between lining and shoe plays a fundamental role in the lining fixing project, which is the most important parameter for the riveted joint calculation. For the lining riveting, the rivet needs to ensure that friction material and shoe remain in contact through the normal force applied on the surfaces, but the rivet should not be exposed to shear forces. Thus, the brake torque transmission must occur through the static coefficient of friction between lining and shoe, not allowing relative slips or movements between the pair in contact. Therefore, the present study aims to understand the influence of the static friction coefficient between lining and shoe as a function of the lining internal superficial roughness, from the evaluation of different roughness conditions - contact area with shoe -. The static coefficient of friction between lining and shoe is a complex measurement to be performed, due to the cylindrical geometry of the drum brake system, so for the present study, a measuring device based on plane geometry will be proposed. Thus, three different friction materials were evaluated, and each one of them had a different formulation and mechanical properties, such as hardness, shear strength, impact resistance, dynamic coefficient of friction, and stiffness. Plane samples were made for each of these friction materials, with three different surface finishing obtained by changing the machining parameters - speed and feed -, generating different surface roughness profiles. For each friction material sample, three sequential tests were performed in order to measure the static coefficient of friction, using a universal testing machine and a flat counter piece with the same material and painting of the shoe. For the test, a specific device was developed, allowing the application of tangential force only on the friction material, keeping the counter piece fixed. From this study, it was possible to conclude that each friction material tested has its level of static coefficient of friction, nevertheless, the superficial roughness did not show influence over static CoF. The static coefficient of friction shows a variation up to 14% for the same friction material and surface condition, being higher than the variation of the same material under different surface conditions.
Lift axle is essentially provided in commercial vehicles to increase the vehicle’s load-carrying capacity. The axle is lowered in the case of a high payload and the load is evenly distributed among the wheels both on fixed axles and the lift axle. This ability to lift the axle implies better maneuverability in turns, better fuel consumption, and less wear and tear on the tires and brake shoes. Also, it will reduce the damage to the road surfaces. This lowering and lifting of the lift axle are controlled by a series of valves together called the Lift Axle Control System (LACS). This LACS must consider the vehicle load condition, the ignition state, and gear state to decide if the axle must be lifted or lowered. This paper deals with the modeling and simulation of the LACS system at the vehicle level and optimize the design for the respective desired design solution.
The paper is devoted to the study of the influence of braking devices over the stability of braking properties of the cars. A technique is proposed for assessing the stability of braking devices using the generalized braking torque equation, which allows the selection of a rational type of braking devices and optimization of the geometric parameters thereof at the design stage of the cars. Stability assessment of the braking torque is carried out according to the criterion of the sensitivity of the braking torque to a change in the coefficient of friction between the friction surfaces of the braking mechanism. Using the dimensionless functions and coefficients depending on the geometric parameters of the friction pairs and the feedback sign in the braking mechanism, it was found that the braking mechanism with one active and one passive pad has less sensitivity to a change in the friction coefficient than the braking mechanism with two active pads. The analysis of the influence of the nonuniformity of the braking forces on the wheels of a certain axis of the car over the deviation of the distribution of braking forces between the axles from its calculated value has been performed. When assessing the error in regulating the distribution of braking forces between the axles of the car, three components were taken into account: theoretical error due to the imperfection of the selected control method (the difference between the actual calculated control characteristic and the ideal one), the error created due to the instability of the ratio of braking forces on the front and rear wheels, and an additional error due to the unevenness of the braking forces on the wheels of individual axles. The proposed method allows assessing the quality of regulation of the distribution of braking forces between the axles of the car, taking into account the instability of the braking forces on the wheels.
On account of the traditional friction brake for heavy-duty truck (HDT), the massive quantity of heat accumulating constantly because of frequent using of friction brake system in the long and steep downhill road leads to brake temperature rising rapidly. Affected by structure frictional couple installed in the closed environment of the brake drum, it is difficult to dissipate the heat in time via heat conduction, heat radiation and heat convection, and the heat fade phenomenon of the brake emerges easily. The HDT would be in danger because of braking efficiency descending. This paper proposes an active water-cooled drum brake system (AWBS) to solve the problem. According to the principle of engineering thermodynamics, the structure and size of the back-stretching water jacket of brake shoe and the inner riveted the friction plate of brake drum are designed with restrained of GB 12676-2014 ‘Technical requirements and testing methods for commercial vehicle and trailer braking systems’. In order to meet the requirements of heat dissipation and structural strength for tractor and trailer, the composition and parameters of AWBS are proposed, including volume and type of coolant, radiator size, hydraulic pump parameters, tank capacity and connection type. To verify the performance of the system, the three-dimensional model and simulating model are established to simulate, the simulation results show that structure meet s strength requirements and the AWBS can significantly inhibit the rise of brake temperature, reduce the probability of brake thermal decay of heavy truck on long downhill, and improve the driving safety of the vehicle significantly.
The air brake system is still the most common brake system in use in heavy diesel vehicles. For safety and economic reasons it is imperative to understand the performance and durability (especially fatigue and wear) of every component of a drum brake, particularly the brake shoes. In applications where torque is lower than 20kNm brake shoes are made of ductile metals such as SAE 1030 steel. For such ductile materials Brown-Miller and Fatemi-Socie are the most recommended methods for fatigue crack initiation life prediction. The next pages discuss the validation of these fatigue methods in the case study of a 325mm brake shoe.
This SAE Recommended Practice establishes a uniform procedure for the level road test of the brake systems of all classes of motorcycles intended for highway use.
During the development of a new friction material, besides the interface between lining/drum is also fundamental take in account all aspects involving the attachment of the linings on the brake shoes. This paper presents an optimization approach to the development and manufacturing parameters of brake linings, applied on medium and heavy duty commercial vehicles, aiming to assure the correct specification of the riveted joint clamp forces. These evaluations were conducted based on the quality tools documents and the theoretical aspects of the product usage as well as the modeling of key elements of the referred mechanism throughout various known applications. A calculation methodology was developed based on brake geometry, its generated forces and braking reactions required for each vehicle family. Taking in consideration the mathematical modeling of lining riveting process, the study incorporated calculated parameters on the production of new parts to proceed with bench and dynamometer preliminary tests. After theoretical approach an optimized process of lining riveting was implemented on the riveting machine focusing on its capacity to generate the required clamp force on a production scale. With the results from experimental testing, further vehicular performance correlations were performed aiming durability endurance maximization on proving ground tracks. The main objective of this paper is to show all steps involved on defining a robust riveting process based on calculation, experimental testing and rooted on vehicular correlation and validation aspects, obtaining a method to specify the required clamp force of the riveted joint on brake linings development.
This code provides a test procedure for obtaining and determining extremely high brake fluid temperature encountered in the brake system of a vehicle that is equipped with disc brakes. Vehicles in normal operation may or may not produce brake fluid temperatures that are obtained in this procedure.
The purpose of this study is to propose an effective model to estimate the excitation force accompanied with stick-slip between shoe and disc, considering the strain distribution on contact surface of the shoe, and then to propose an effective concept to design the brake which reduced the brake squeal under practical use. In order to investigate the influence of configuration of the hole, three types of discs were prepared in which the size of holes was different. The SPL (Sound Pressure Level) and the frequency of squeal for three types of discs were measured when the brake squeal was observed at conditions of low sliding speed. The change of stability of the brake shoe passing on hole was analyzed by 2-D simplified brake system model. In order to investigate how the strain distribution of the shoe affected on the excitation force caused by stick-slip, FE (Finite-element) and FDTD (Finite-difference time-domain) analysis were utilized to simulate the elastic wave propagation in the shoe under braking. Test result showed that the SPL of the brake squeal was reduced at significant peak of SPL around 700Hz when the disc had large diameter holes on the frictional surface. The stability analysis also showed that the stable region was extended when large hole was opened on the disc. The excitation force estimated by FE and FDTD model of the shoe was reduced when the diameter holes was increased. These results indicated that the excitation force at brake squeal was prevented by the modification of strain distribution. Such discussion was experimentally confirmed by the bench test with modified shoes which had concentrated strain distribution. This paper proposed an effective concept to prevent the squeal of the brake disc for motorcycles.
This SAE Recommended Practice establishes a uniform procedure for the level road test of the brake systems of all classes of motorcycles intended for highway use.
Items per page:
50
1 – 50 of 98