Initial Braking Velocity Research Articles

Friction Performance Analysis of Mine Wet Multi-Disc Brake

<div>This article takes the wet multi-disc brake used in mining Isuzu 600P as the research object, establishes a simplified three-dimensional model of its key components through SOLIDWORKS and imports it into ANSYS Workbench to establish the flow field and structure field model of the wet brake. Based on the fluid–solid coupling, the finite element simulation of the temperature field and stress field of the friction pair of the wet brake under different braking pressures, braking initial speeds, and fluid viscosities was carried out, and then the position changes of the friction pairs at high temperature hot spots and high stress points were analyzed to determine the stability of its friction performance. Finally, by comparing the temperature change curves of the same point during the braking process under different braking conditions, the validity of the finite element analysis results is verified. The results show that the flow field pressure inside the wet brake is opposite to the flow field velocity, the initial braking velocity is the most influential factor on the friction performance of the friction pair, affected by the fluid, the maximum equivalent stress of the groove between the core plates is the same as the braking force. Pressure, braking initial speed, and fluid viscosity are proportional.</div>

RETRACTED] Investigation for Evaluating the Energy Recovery Capacity of the Mechanical Brake System on Urban Buses: A Case in Vietnam

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 Available online: 31 October 2020
 
 This article has been retracted by International Journal on Advanced Science, Engineering and Information Technology Editorial team, following clear correspondence and confirmation with authors.
 
 The paper is retracted from 18 July 2022.
 
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 Currently, traditional fossil energy is gradually exhausted for sustainable economic development, and environmental protection is an urgent requirement for all countries. Therefore, the issue of saving energy, as well as exploiting renewable energy sources, is being prioritized for development. The braking system collects dynamic energy, also known as the regenerative braking system, which is understood as the brake system; instead of converting kinetic energy into heat, the brake system can collect and store energy. The brake system of the bus in use is usually frictional. During braking, this type of brake system converts the vehicle's kinetic energy into heat, dissipates it into the surrounding environment, and cannot be recovered. Moreover, due to the operational characteristics, the bus has high stopping frequency and high braking capacity, leading to wasted energy, in addition to producing many emissions causing environmental pollution. This study focuses on experimental research for evaluating the dynamic energy acquisition of the mechanical brake system on a school bus as a function of operating parameters such as vehicle speed according to gears, vehicle mass as well as hydraulic pressure parameters. The results are noticed that the highest dynamic energy recovery rate is about 35% in the lowest gear. In the case, from the initial braking velocity of 30km/h to 0 km/h, the initial working pressure of the hydraulic tank is 100bar, the dynamic energy recovery rate is about 25%.

Thermo-Mechanical Coupling Analyses for Al Alloy Brake Discs with Al2O3-SiC(3D)/Al Alloy Composite Wear-Resisting Surface Layer for High-Speed Trains.

In the present work, a theoretical model of three-dimensional (3D) transient temperature field for Al alloy brake discs with Al2O3-SiC(3D)/Al alloy wear-resisting surface layer was established. 3D transient thermo-stress coupling finite element (FE) and computational fluid dynamic (CFD) models of the brake discs was presented. The variation regularities of transient temperature and internal temperature gradient of the brake discs under different emergency braking conditions were obtained. The effects of initial braking velocity (IBV) and thickness of Al2O3-SiC(3D)/Al alloy composite wear-resisting layer on the maximum friction temperature evolution of the disc were discussed. The results indicated the lower temperature and thermal stress distributed uniformly on the wear-resisting surface, which was dominated by high conductivity and cooling ability of the Al alloy brake disc. The maximum friction temperature was not obviously affected by the thickness of the wear-resisting layer. The maximum friction temperature of the brake discs increased with the increase of the IBV, the maximum friction temperature and thermal stress of the brake discs is about 517 °C and 192 MPa at IBV = 97 m/s considering air cooling, respectively. The lower thermal stress and fewer thermal cracks are produced during the braking process, which relatively decrease the damage. The friction behavior of the tribo-couple predicted using FE method correlated well with the experimental results obtained by sub-scale testing.

Braking Efficiency and Stability of Chassis Braking System of Combine Harvester: The Theoretical Derivation and Virtual Prototype Simulation

With the advancement of agricultural mechanization, the safety of agricultural vehicles has aroused extensive concern. However, conventional methods evaluate the performance of the combine harvesters in a laborious and inaccurate filed-test way. It is still a challenge to evaluate their performance in a theoretical derivation-based simulation way. Here, we accurately derive the braking model of the combine harvester, which provides a guidance for further braking simulation. Firstly, a four-wheel braking system was designed and theoretically checked. Secondly, the virtual prototype of the chassis braking system was established in ADAMS, in consideration of the complicated contact characteristics between the tire and the road and between the friction pad and the brake disk. Finally, simulation experiments of braking efficiency and directional stability were carried out under different braking conditions. By this means, we find a novel effective yet simple way to optimize the braking efficiency as well as the sufficient braking stability of combine harvesters. The results show that braking efficiency would be improved with stronger braking force, lower initial braking velocity, and lighter weight of the combine harvester. Compared with straight-line braking, steering braking shows lower braking efficiency and less inclination of rear wheel bounce under the same braking conditions. As for braking directional stability, the lateral slippage would be increased with the locking of rear wheels, higher driving speed, or lower road adhesion coefficient. In addition, the simulation results are in agreement with the theoretical results, proving the validity of the virtual prototype simulation. Overall, other than traditional filed-test methods, our method provides an effective yet simple way for designing and evaluating the chassis braking system of combine harvesters.

Analysis of longitudinal forces of coupler devices in emergency braking process for heavy haul trains

To reduce the longitudinal coupler forces of heavy haul trains and improve the running safety, the velocity method and New-mark method were used for the coupler simulation and numerical integration, and a numerical model on the longitudinal dynamics of heavy haul trains was established. Validation was performed against the experimental data. Using this model, the emergency braking process for a combined marshalling heavy haul train was investigated to obtain the distributions of the longitudinal compressive forces and strokes of coupler devices. Then, the influences of the initial braking velocity, the synchronization time of master and slave locomotives, the coupler stiffness and the vibrator mass on the longitudinal forces and strokes were analyzed. The results show that it should be avoided that the emergency braking starts at a low initial speed. Keeping synchronism between master locomotive and slave locomotives effectively helps to reduce the longitudinal forces. Reducing the coupler stiffness appropriately and adding rigid arm connections, the longitudinal vibration frequency can be brought down and the longitudinal forces will be decreased, which improves the running safety of heavy haul trains. All of these research results can provide a reference for the operation and development of heavy haul trains.

Thermal Fatigue Analysis and Evaluation of Wheel-Rail Contact under Braking Conditions

Recently, reliability design considering the fatigue has been demanded for ensuring the driving safety for the high speed railway. In particular, the railway wheel and rail are subjected not only to mechanical load but also to highthermal load due to frictional heat generated when the railway wheel contacts with the brake shoe during tread braking. As repetitive thermal load accelerates damage to the wheel surface, it leads to shorten the replacement cycle and increase the maintenance cost. Therefore, we expect to achieve the economic efficiency by using the wheel over the life expectancy while maintaining the structural health. Initial braking velocity is one of the main factors affecting the behaviors of contact surface between the wheel and rail. Therefore, it is necessary to evaluate the effect of thermal stress according to it. In this study, through the thermalmechanical analysis considering both mechanical load and thermal load caused frictional heat under braking conditions, thermal stress subjected to the contact surface between the railway wheel and rail was calculated. Based on these results, the thermal fatigue analysis was carried out to evaluate the safety under fatigue and predict the fatigue life.

Objective Characterization on the Dynamic Friction Coefficient of Disc Brake

ABSTRACTAs the most significant parameter for evaluating the friction state of disc brakes, the friction coefficient was characterized solely by its average and stability coefficient, which cannot accurately represent its dynamic variation characteristics during braking. In this article, a new characterization parameter set consisting of an overall and a partial characteristic parameters subset was established to characterize the dynamic variation in friction coefficient of disc brakes. Moreover, the influence of braking conditions on these new parameter sets was studied by tribological experiments. Several simulated braking experiments were carried out and the dynamic variation rules were observed. Secondly, a new characterization parameter set including eight parameters (mean value, stability coefficient, energy coefficient, end point of rapid rising, starting and end points of the up-tail, trend coefficient, and catastrophe coefficient) was established. Finally, the influence of initial braking velocity and braking pressure on these parameters and its mechanism was analyzed by braking experiments. It is concluded that the parameter set established in this article can be used to characterize the dynamic variation rules of the friction coefficient of disc brakes more objectively and comprehensively.

A new temperature parameter set for characterizing the frictional temperature rise of disc brakes

Purpose – The purpose of this study is to establish a new temperature set for characterizing the frictional temperature rise (FTR) of disc brakes. The FTR produced by braking is an important factor which directly affects the tribological properties of disc brakes. Presently, most existing researches characterize the FTR only by several static parameters such as average temperature or maximum temperature, which cannot reflect accurately the dynamic characteristics of temperature variation in the process of braking. In this paper, a new temperature parameter set was extracted and the influences of braking conditions on these parameters were investigated by experiments. Design/methodology/approach – First, several simulated braking experiments of disc brakes were conducted to reveal the dynamic variation rules and mechanisms of the FTR in braking. Second, the characteristic parameter subset of the FTR was extracted with five significant parameters, namely, initial temperature, average temperature, end temperature, maximum temperature and the ratio of maximum temperature time. Furthermore, the fitting parameter subset of the FTR was constructed based on the temperature rise curve. Finally, the influence and mechanisms of initial braking velocity and braking pressure on the new temperature parameter set were investigated through braking experiments. Findings – This paper extracted a new temperature parameter set including a characteristic parameter subset and a fitting parameter subset and revealed the influences of braking conditions on it by experiments. Originality/value – The results showed that the new temperature parameter set extracted in this paper can characterize the dynamic characteristics of disc brake’s FTR variations more objectively and comprehensively. The research results will provide a theoretical basis for extracting the fault feature of friction properties.

Characterization and experiments on the friction catastrophe behaviors of brake material during emergency braking

Based on previous researches on the phenomena and mechanisms of Friction catastrophe (FC), the characterizing methods of the FC were established and the influences of braking conditions on the FC were investigated by experiments. It is found that the FC intensity, duration and starting time can be used for characterizing the FC, which reflects respectively the decreasing degree, velocity and critical time of the friction coefficient in FC. For short duration, the starting time is more practically valuable. With the increasing of initial braking velocity or braking pressure, the FC starting time becomes shorter while the FC intensity grows bigger. By comparison, the influence of initial braking velocity on the FC starting time is more obvious while the braking pressure affects the FC intensity more intensely. It is believed that the results must be valuable for further studies on the FC and can also provide a theoretical basis for reducing the occurrence of frictional failure of friction brakes.

Frictional Performance and Temperature Rise of a Mining Nonasbestos Brake Material during Emergency Braking

By simulating emergency braking conditions of mine hoisters, tribological experiments of a mining nonasbestos brake material sliding on E355CC steel friction disc investigated a pad-on-disc friction tester. It is shown that, under combined influence of braking velocity and pressure, the lubricating film and micro-convex-apices on wear surface would have complex physicochemical reactions which make the instant friction coefficient rise gradually while the instant surface temperature rises first and then falls. With the antifriction effect from lubricating film and the desquamating of composite materials, the mean friction coefficient decreases first, then rises, and decreases again with the increasing of initial braking velocity. And with the existence of micro-convex-apices and variation from increment ratio of load and actual contacting area, it rises first and then falls with the increasing of braking pressure. However, the mean surface temperature rises obviously with the increasing of both initial braking velocity and braking pressure for growth of transformed kinetic energy. It is considered that the friction coefficient cannot be considered as a constant when designing brake devices for mine hoisters. And special attention should be paid to the serious influence of surface temperature on tribological performance of brake material during emergency braking.

Experimental verification of numerical model of integral bridge

The paper presents the results of analyses of displacements for a real reinforced concrete integral bridge. The research consisted of the measurement of vertical displacement in the middle of the span and lateral displacement of the abutment. Ten load cases were considered. Two of them concerned vehicles placed motionlessly, the rest ones – braking vehicles. Moreover, the influence of initial braking velocity was analysed. The results of research were compared with numerical simulations. Two options of numerical models were considered. In the first case, cooperation between construction of span and road layers was ignored, but in the second one it was not. In the both options, the same soil conditions were assumed.Cooperation between construction and road layers was took into consideration by the increase of stiffness of span. A real heterogeneous cross section was reduced to homogeneous one. Road layers were converted to equivalent concrete layers. Neutral axis, moment of inertia and thickness were calculated for a reduced cross section and applied into model.Relations between displacements and duration were presented for load cases with braking vehicles. Displacements due to braking forces and static load were compared.

Wear performance and its online monitoring of the semimetal brake lining for automobiles

Purpose – In order to improving the braking reliability and assuring the driving safety of automobiles, this paper aims at the wear performance and its online monitoring of its brake lining. Design/methodology/approach – The wear performance of the semimetal brake lining for automobiles was investigated on a self-made braking tester for disc brakes. Based on the experimental data, an intelligent forecasting model for the wear rate was established by the artificial neural network (ANN) technology. And by taking it as a core, an online braking wear monitoring system for automobiles was designed. Findings – It is shown that the wear rate rises obviously with the increasing of both initial braking velocity and braking pressure. By the contrast, the initial braking velocity affects the wear rate more seriously. The ANN model trained by the experimental data shows favorable capability for predicting of the wear rate. The big forecasting errors at high velocity and heavy load should be attributed to the jumping of the wear rate at this period. Based on the existed sensors and electronic control unit system of automobiles, the online braking wear monitoring system can be established easily by the ANN technology. Originality/value – A self-made braking tester for disc brakes was used to test the wear performance, which can simulate better the actual disc braking conditions than the standard pin-on-disc friction tester. An online braking wear monitoring system was designed to help improving the braking reliability and safety of automobiles.

A cusp catastrophe model for the friction catastrophe of mine brake material in continuous repeated brakings

The frictional performance of the brake material used in mine hoisters varies abnormally under some extreme braking conditions. Its friction coefficient runs the danger of falling suddenly in such a braking. Based on the catastrophe theories and the energy transforming ideas, this article established a cusp catastrophe model to describe and predict the friction catastrophe behaviors of the brake material in some continuous repeated brakings of mine hoisters. The predictive capability of the model was verified by some braking experiments. It is shown that the catastrophe phenomena of the friction catastrophe in braking can be described by the catastrophe theories as a cusp catastrophe. The friction coefficient can be taken as its state variable. The initial braking velocity and braking frequency can be taken into account for one control variable while another control variable may contain the braking pressure and braking time. Moreover, the friction catastrophe of the brake material has a critical braking state. The cusp model built in this article can properly predict its critical braking frequency. However, in the present state, the exact time that the friction catastrophe occurs in a critical braking cannot be accurately located.

Influences of Initial Braking Velocity and Passenger Capacity on Mean Fully Developed Deceleration

In order to improve the comprehensive and rationality of examination for driving braking performance with Mean Fully Developed Deceleration (MFDD) in road test, also to provide a basis for driving braking performance evaluation with MFDD when real driving, an approach for determining the MFDD threshold is proposed considering initial braking velocity and passenger capacity. According to the vehicle braking performance road test rules in GB7258, a simulation model is built, and simulation tests are made with different initial braking velocities. Based on simulation data, MFDD is calculated, and the curve of MFDD with initial braking velocity is also given, and then the effects of initial braking velocity on MFDD and its threshold are analyzed; the curves of MFDD thresholds with initial braking velocity are plotted with no-load and full-load respectively. The influence of passenger capacity on MFDD threshold is analyzed, and the curve of MFDD threshold with passenger capacity is given, too. Finally, the formula of MFDD threshold with initial braking velocity, seating capacity and passenger capacity is resulted.

A Systematic Research on Reconstructing the Accident Velocity with Braking Traces

Braking trace is the important basis to reconstruct the speed of the accident vehicle. There does not exist one-to-one relationship between the barking trace and the vehicle speed. It needs to have a further research on the factors influencing their corresponding relations, otherwise it may appear great errors to reproduce the vehicle speed with the braking trace. This paper analyzes the influence of people, cars, roads, environmental factors on the corresponding relationship between the initial braking velocity and braking traces, explores the use conditions and parameters selection of the reconstructed model in the standard GA/T643-2006, and the experiment is designed to research on the uncertainty of the reconstruction of the model. Besides, it has proposed the experimental reconstruction method.

Dynamic performance analysis of a seismically isolated bridge under braking force

In order to study the dynamic performance of seismically isolated bridges under the most unfavorable loads in the longitudinal direction, a dynamic equation for vehicle braking in the longitudinal direction is established. A four or fiveorder Runge-Kutta method is adopted to obtain the time-history response of a wheel set under braking force. The quadratic discretization method is then used to transform this time-history into a braking and bending force time-history of a structural fixed node, and a dynamic response analysis of the seismically isolated bridge under the vehicle’s braking force is carried out using ANSYS, a universal finite element analysis software. According to the results, seismic isolation design results in a more rational distribution of braking force among piers; the influence of the initial braking velocity on the vehicle braking force is negligible; the location where the first wheel set leaves the bridge is the most unfavorable parking location; a seismic isolation bridge bearing constructed according to typical design methods enters into a yield stage under the braking force, while the shearing force at the bottom of the pier declines as the isolation period is extended; the design requirements can be met when the yield displacement of the seismic isolation bearing is less than 5 mm and the yield strength is greater than the braking force.

Influence of initial braking velocity and braking frequency on tribological performance of non‐asbestos brake shoe

PurposeThe purpose of this paper is to find the influence of the initial braking velocity and braking frequency on the tribological performance of the non‐asbestos brake shoe used in mine hoisters during some continuous emergency brakings.Design/methodology/approachThe tribological performance experiments of the WSM‐3 non‐asbestos brake shoe braking on the 16 Mn steel are investigated on the X‐DM friction tester, by simulating continuous emergency brakings of a mine hoister ten times. Three kinds of tribological indexes: friction coefficient, its stability coefficient, and wearing rate are considered to score the tribological performance of the brake shoe.FindingsWhen the initial braking velocity increases, the mean friction coefficient of the brake shoe decreases at first, then rises, and falls again finally. But when the braking frequency exceeds seven times, the falling process of the friction coefficient at low‐velocity period does not appear again. Second, when the initial braking velocity is no higher than 10 m/s, the mean friction coefficient rises with the braking frequency increasing. But when the velocity exceeds 10 m/s, the mean friction coefficient rises with the braking frequency increasing at first, then falls. Third, when the initial braking velocity is no higher than 12.5 m/s, the friction coefficient of the brake shoe has quite a favorable stability with the coefficient is no bigger than 75 percent. But when the velocity exceeds 12.5 m/s, the stability of the friction coefficient is diminishing obviously. Fourth, the wearing rate of the brake shoe increases quickly, during the process that the velocity rising from 10 to 12.5 m/s, but increases much more slowly after that period.Originality/valueThe paper investigates the tribological performance of the WSM‐3 non‐asbestos brake shoe during some continuous emergency brakings and finds that, when the initial braking velocity is no higher than 12.5 m/s and the braking frequency is no more than seven times, the WSM‐3 non‐asbestos brake shoe has quite a high friction coefficient, a good friction stability, and a low‐wearing rate, which indicate that it is very appropriate for using in the disk brake of mine hoisters in China.