Braking Effect Research Articles

Thermal Effect of Braking on Pavements during Heat Waves in Ouagadougou

Thermal Effect of Braking on Pavements during Heat Waves in Ouagadougou

Modeling the Vehicle Movement and Braking Effect of the Hydrostatic Regenerative Braking System

Modeling the Vehicle Movement and Braking Effect of the Hydrostatic Regenerative Braking System

Reliability evaluation of electromechanical braking system of mine hoist based on fault tree analysis and Bayesian network

Electromechanical braking system is the key way to improve the braking response ability of mine hoist. At present, the reliability research of electromechanical braking system is less. In order to further analyze and improve the reliability of electro-mechanical braking system, this paper adopts the reliability analysis method of electro-mechanical braking system based on fault tree and Bayesian network. Firstly, the fault tree of the electro-mechanical braking system is established, and then the fault tree is transformed into a Bayesian network, and the posterior probability, probability importance and key importance of each root node are inversely deduced. The diagnosis results show that the ball screw is the weakest link of the electro-mechanical braking system. Then the static simulation and fatigue life simulation of the ball screw are carried out for optimization, and the optimal model of the ball screw is determined. Finally, the electro-mechanical brake installed with the optimized ball screw is tested and analyzed. After the reliable performance test of the electro-mechanical brake, it is finally determined that the braking effect of the optimized electro-mechanical brake is stable.

Tracing Magnetic Fields in IC 1954 with Velocity Gradient

Magnetic fields, especially the magnetic braking effect, are crucial in transporting fuel materials to the galactic center and powering nuclear starbursts. To access the magnetic fields directly associated with molecular gas, we use the novel velocity gradient technique (VGT). By applying VGT to the high-resolution CO (2-1) emission lines obtained from the PHANGS-ALMA survey, we present the magnetic field orientation map for the galaxy IC 1954. With the advent of next-generation radio and spectroscopic observations from SKA and ngVLA, we discuss the promise of studying extragalactic magnetic fields at pc-scale.

Angular momentum Based-Analysis of Gas-Solid fluidized beds in vortex chambers

Gas-solid vortex chambers are a promising alternative for reactive and non-reactive processes requiring enhanced heat and mass transfer rates and order-of-milliseconds contact time. The conservation of angular momentum is instrumental in understanding how the interactions between gas, particulate solids, and chamber walls influence the formation of a rotating solids bed. Therefore, this work applies the conservation of angular momentum to derive a model that gives the average angular velocity of solids in terms of gas injection velocity, wall-solids bed drag coefficient, gas and particle properties, and chamber geometry. Three datasets from published studies, comprising 1 g-Geldart B- and d-type particles in different vortex chambers, validate the model results. Using a sensitivity analysis, we assessed the effect of input variables on the average angular velocity of solids, average void fraction, and average bed height. Results indicate that the top and bottom end-wall boundaries exert the most significant braking effect on the rotating solids bed compared with the cylindrical outer wall and gas injection boundaries. The wall-solids bed drag coefficient appears independent of the gas injection velocity for a wide range of operating conditions. The proposed model is a valuable tool for analyzing and comparing gas–solid vortex typologies, unraveling improvement opportunities, and scale-up.

Influences of the Braking Effect of Ruler EMBr on Molten Steel Flow and Steel–Slag Interface Fluctuation in a Continuous Casting Mold

Electromagnetic braking (EMBr) technology, as one of the most effective technologies in the continuous casting process, provides an effective tool for improving the internal and external defects of steel products. Specifically, the EMBr technology takes the benefit of the generation of Lorentz force to decrease flow instability, mold powder entrapment, and surface defects, if applied properly. For this purpose, to gain a clear understanding of the effect of EMBr technology on the continuous casting process, a commonly used EMBr technology, namely ruler EMBr technology, is applied in the current work to investigate the dynamic behaviors of molten steel flow and steel–slag interface fluctuation inside a slab mold. Furthermore, to obtain a desirable braking effect of the ruler EMBr technology, operational parameters including the magnetic flux density, submerged entry nozzle (SEN) depth, and magnetic pole location are numerically investigated. The results demonstrate that the braking effect exerted by the ruler EMBr device is favorable for suppressing the impact of upward stream on the steel–slag interface with the magnetic flux density exceeding 0.3 T. For the influence of the SEN depth and magnetic pole location on the effect of ruler EMBr mold, the results show that a steady jet flow pattern can be obtained through the adjustment of a location between the ruler EMBr device and the SEN depth. For instance, when the ruler EMBr device installation position of 225 mm corresponds to the SEN depth of 150 mm, the upward deflection of jet stream is suppressed and a stable interface fluctuation profile is formed. With this adjustment, the possibility of mold flux entrapment is decreased.

An improved combination of ruler and local electromagnetic brakes for continuous casting process

In the present study, using computational fluid dynamics, we aim to systematically propose an improved combination of local and ruler ElectroMagnetic Brakes (EMBr) to reduce the surface and internal defects in the thin-slab steel continuous casting. To achieve this goal, first, each of governing submodels, including turbulent fluid flow and heat transfer, solidification, and electromagnetics, is carefully validated. Then, the model is used to evaluate the performance of different EMBr design configurations in terms of six flow metrics, i.e., the flow pattern, solidified shell thickness, surface velocity, turbulent kinetic energy, level fluctuation, and superheat transport. The results manifest that the braking effect, imposed by the combinations of ruler and local EMBrs, effectively resolves the problem of uneven solidified shell growth, especially for SEN-type casters. On the other hand, using local EMBrs on the thin wall midway the SEN and meniscus can result in unstable flow structures which are prone to change to the detrimental single-roll pattern under the perturbations in the operating conditions. Finally, the best performance is achieved by the combination of a single-ruler EMBr below the SEN and a couple of local EMBrs near the center of the meniscus. This configuration substantially increases the superheat transport to the surface and decreases surface mean and fluctuating velocities, especially at the meniscus near the walls, and can effectually prevent the formation of defects.

Modeling Study on Melt Flow, Heat Transfer, and Inclusion Motion in the Funnel-shaped Molds for Two Thin-Slab Casters

For the purpose of studying compact strip production (CSP) funnel-shaped mold and flexible thin-slab rolling (FTSR) funnel-shaped mold, a three-dimensional (3D) multi-field coupling mathematical model was established to describe the electromagnetic braking (EMBr) continuous casting process. To investigate the metallurgical effect of EMBr in the CSP and FTSR funnel-shaped thin-slab molds, a Reynolds-averaged Navier–Stokes (RANS) turbulence model, together with an enthalpy–porosity approach, was established to numerically simulate the effect of ruler EMBr on the behaviors of melt flow, heat transfer, solidification, and inclusion movement in high-speed casting. The simulation results indicate that the application of ruler EMBr in the CSP and FTSR molds shows great potential to improve the surface temperature of molten steel and reduce the penetration depth of downward backflow. This contributes to the melting of the slag rim near the meniscus region and facilitates the floating removal of the inclusions in the molten pool. In addition, in comparison with the case of no EMBr, the parametric study shows that the braking effect of ruler EMBr with an electromagnetic parameter of 0.5 T can enhance the upward backflow in the two high-speed thin-slab molds. The enhanced upward backflow can successfully entrain the inclusions to the top of the mold and improve the activity of surface fluctuations to avoid the formation of the slag rim. For instance, for the ruler EMBr applied to the FTSR mold, the maximum amplitude of surface fluctuation and the floatation removal quantity of inclusions with a diameter of 100 μm are increased by 4.6 percent and 51 percent, respectively.

A novel Halbach array electromagnetic pump for liquid metal flow: Design proposal and performance analysis

This paper proposes a “Halbach array electromagnetic pump for liquid metal” (HA-EMP) by applying the “Halbach ring permanent magnet array” to a direct current conductive electromagnetic pump (DC-EMP). Material selection and structure designs are carried out based on the application background of the liquid metal secondary loop in a space reactor. Performance under different flow rates, currents and duct dimensions of the electromagnetic pump are studied. The conclusions are as follows. The magnetohydrodynamic (MHD) braking effect caused by the magnetic field is responsible for the limited flow rate in DC-EMP. Increasing the magnetic flux density in the fluid facilitates a higher pressure head but also a lower flow rate. Comparing with the traditional structure electromagnetic pump (Trad-EMP), HA-EMP possesses more development potential in view of higher pressure head, smaller size and lighter weight. For the same size, the HA-EMP increases static pressure head and work efficiency by more than 84% and 15%, respectively, while the flow rate is reduced by more than 41%, at conditions of the currently studied parameter ranges. When the magnetic flux density is the same, HA-EMP can save more than 50% of volume compared to Trad-EMP. However, the end effect of the magnetic field along the flow still severely hinders its better performance and will become the next focus of optimization.

Research on Electric Control Brake System Based on Railway Vehicle

The trackless train may be mixed with other vehicles in the city. Therefore, developing a vehicle braking system with high reliability, fast response, and powerful braking force is necessary. In this research, the chip module control is added to each control part to realize rapid electric signal collection and response, and then the pneumatic control of each actuator is used to realize rapid and flexible electric braking control of the vehicle. The braking system has been tested on the test bench in the factory, and its response speed and braking effect have increased by 10% compared with the traditional bus braking system. When the performance test is carried out on the real vehicle, the braking effect is also improved by nearly 10%. Through the design of the braking system, the braking system of domestic trackless trains can be perfectly solved.

Thermomechanical testing and modelling of railway wheel steel

Studies of thermal effects of tread braking on railway wheels show that the wheel temperatures may reach above 600 °C, at which the mechanical properties of the wheel steel are significantly impaired. Computational models that simulate the thermomechanical behaviour of the wheels are commonly based on results from laboratory tests which do not reflect actual in-service scenarios. Anisothermal testing and modelling are omitted due to the difficulties in designing relevant experiments and implementation of the results. In this paper, a preexisting numerical material model is extended in order to implement fully anisothermal behaviour. This is done by performing several thermomechanical experiments mimicking real-world service and worst-case scenarios ranging from room temperature up to 650 °C. The results from the laboratory testing are then used in combination with data from traditional isothermal tests to optimise the numerical material model by calibrating its material parameters. As part of this process it was found necessary to include a time- and temperature-dependent, non-recoverable (irreversible) mechanism for material softening and microstructural changes which occur above 400 °C. Finite element simulations with the material model using the new parameters and the softening law show markedly improved adherence to anisothermal and strain-controlled experimental results compared to the preexisting model(s). The results demonstrate that anisothermal testing is a requirement for models that are intended to simulate material behaviour for thermomechanical loads and thermally induced microstructural changes.

A Pneumatic Control Method for Commercial Vehicle Electronic Brake System Based on EPV Module

The traditional electronic braking system (EBS) of a commercial vehicle has the problems of sluggish pressure response, large dynamic error and unsatisfactory braking effect during braking. First, a novel EBS system based on electronic pneumatic valves (EPV) module is designed, which integrated the control of each pneumatic valve. Secondly, the hardware of the EBS bottom controller and the air pressure closed-loop control are carried out. A kind of similar to PWM (SPWM) air pressure control method is proposed. By controlling the opening and closing time of the solenoid valves, the brake air pressure could be precisely regulated, and the dynamic response characteristics of the system are improved. Eventually, commercial vehicle air brake hardware in the loop (HIL) test platform based on LabVIEW and NI-PXI system is built to verify the effectiveness of the EBS dynamic response characteristics. The experimental results showed that the continuous control of EBS solenoid valves is realized by using the SPWM control method, and the fine dynamic response characteristics of EBS air pressure closed-loop control are ensured.

Quantifying the effects of high-speed shaft braking on the substructural dynamics of monopile offshore wind turbines

ABSTRACT This paper investigates the effects of high-speed shaft braking (HSB) on the substructural dynamics of monopile-type offshore wind turbines. By incorporating blade aerodynamics, generator-torque control, monopile structural dynamics, and the HSB control, the main dynamics of the offshore wind turbine are analyzed. Dynamic simulations of a monopile 5 MW offshore wind turbine by utilizing a high-fidelity aeroelastic offshore wind turbine model are used to provide detailed results. Orthogonal experiments are also conducted using the Taguchi method for different levels of the HSB control. The results reveal that the roll/sway displacements of the monopile and the side-to-side shear force of the tower-top/yaw bearing experience amplitude vibrations (around 20% of the rated value) due to the HSB control. The HSB control not only changes the instantaneous dynamic loads (more than 25% of the rated values) on the blades but also can interact with the normal wind turbine control. Therefore, the HSB control should be carefully designed and applied when the offshore wind turbine is in normal operation since incorrect HSB control may excite large oscillations.

Locating the cocktail and scaling-relation breaking effects of high-entropy alloy catalysts on the electrocatalytic volcano plot

High entropy alloys (HEAs) have been the star materials in electrocatalysis research in recent years. One of their key features is the greatly increased multiplicity of active sites compared to conventional catalytic materials. This increased multiplicity stimulates a cocktail effect and a scaling-relation breaking effect, and results in improved activity. However, the multiplicity of active sites in HEAs also poses new problems for mechanistic studies. One apparent problem is the inapplicability to HEA catalysts of the currently most popular mechanistic study method, which uses the electrocatalytic theoretical framework (ETF) based on the computational hydrogen electrode (CHE). The ETF uses a single adsorption energy to represent the catalyst, i.e., a catalyst is represented by a ‘point’ in the volcanic relationship. It naturally does not involve the multiplicity of active sites of a catalyst, and hence loses brevity in expressing the cocktail effect and scaling-relation breaking effect in HEA catalysis. This paper attempts to solve this inapplicability. Based on the fact that the adsorption energy distribution of HEAs is close to a normal distribution, the mean and variance of the adsorption energy distribution are introduced as descriptors of the ETF, replacing the original single adsorption energy. A quantitative relationship between the variance and the cocktail and scaling-relation braking effects is established. We believe the method described in this work will make the ETF more effective in mechanistic studies of HEA electrocatalysis.

Simulation of the Braking Effects of Permanent Magnet Eddy Current Brake and Its Effects on Levitation Characteristics of HTS Maglev Vehicles

High-temperature superconducting (HTS) magnetic levitation (maglev) trains for designed high speed need a non-contact braking method that can produce stable and sufficient braking forces to ensure the safety of the train during emergency braking. In order to study the braking effects of permanent magnet eddy current braking (PMECB) used in HTS maglev vehicles and its effects on the levitation performance of HTS maglev vehicles, an equivalent two-dimensional simulation model of PMECB for a HTS maglev test vehicle under different working air gaps of 5 mm, 10 mm, 15 mm and 20 mm was established in Maxwell software. Then, a 6 degree of freedom dynamic model of the vehicle was established in Universal Mechanism software. In the dynamic simulation, the normal force of PMECB was not considered, and only the detent force of PMECB was taken as the excitation of the vehicle. The simulation results show that PMECBs can reduce the vehicle to relatively low speed in a few seconds. During the operation of PMECBs, the levitation height and levitation force of the maglev Dewar will be affected, and maximum variations in levitation heights and levitation forces occur on the Dewars at both ends of the vehicle. These help us to understand the braking and levitation performance of HTS maglev vehicles under the action of PMECBs and enrich the design idea of braking and levitation systems of HTS maglev vehicles equipped with PMECBs.

Comparative analysis of AEB effectiveness based on typical and atypical scenarios of electric two-wheeler accidents in China

Electric two-wheeler (ETW) accidents are one of the most important types of traffic accidents in China. Currently, the China New Car Assessment Program (C-NCAP) has proposed test scenarios to evaluate the effectiveness of autonomous emergency braking (AEB) for ETWs, including several common typical crash scenarios, but other atypical scenarios have not been considered. To determine the performance of AEB in real accidents, 16 in-depth accident cases with typical scenarios and 11 cases with atypical scenarios were selected based on a proposed C-NCAP typical scenario set and reconstructed using the virtual simulation tools MADYMO and PC-Crash. The crashes were re-simulated with a car equipped with an AEB system while varying the sensor field of view (FOV), time-to-collision (TTC), sensor delay time (SDT), and lateral trigger width ( W). The results show that for almost all combinations of AEB parameters, the crash avoidance rate was much higher in the typical scenario than that in the atypical scenario. When using an AEB with a FOV of 90° (±45°), all ETW accidents were avoided in typical scenarios, while even with the most efficient AEB system (FOV = ±60°, TTC trigger value = 1.5 s, SDT = 0.1 s), only 82% of crashes were avoided in atypical scenarios. Further considering the effect of lateral width, increasing the width from 2 to 5 m, the maximum avoidance rate of the AEB system increased by 43% in the typical scenarios and 18% in the atypical scenarios. The findings suggest that the typical AEB test scenarios proposed for C-NCAP were useful for other crash scenarios, but that including additional test scenarios may better reflect real world crash scenarios. It is recommended that atypical scenarios should be considered in C-NCAP, particularly perpendicular crash scenarios with the car or ETW turning, to better describe real accidents and improve vehicle safety.

The IACOB project

Context. Stellar rotation is of key importance in the formation process, the evolution, and the final fate of massive stars. Aims. We perform a reassessment of the empirical rotational properties of Galactic massive O-type stars using the results from a detailed analysis of ground-based multi-epoch optical spectra obtained in the framework of the IACOB & OWN surveys. Methods. Using high-quality optical spectroscopy, we established the velocity distribution for a sample of 285 apparently single and single-line spectroscopic binary (SB1) Galactic O-type stars. We also made use of the rest of the parameters from the quantitative spectroscopic analysis presented in prior IACOB papers (mainly Teff, log g, and multiplicity) to study the v sin i behavior and evolution from the comparison of subsamples in different regions of the spectroscopic Hertzsprung–Rusell diagram (sHRD). Our results are compared to the main predictions – regarding current and initial rotational velocities – of two sets of well-established evolutionary models for single stars, as well as from population synthesis simulations of massive stars that include binary interaction. Results. We reassess the known bimodal nature of the v sin i distribution, and find a non-negligible difference between the v sin i distribution of single and SB1 stars. We provide empirical evidence supporting the proposed scenario that the tail of fast rotators is mainly produced by binary interactions. Stars with extreme rotation (>300 km s−1) appear as single stars that are located in the lower zone of the sHRD. We notice little rotational braking during the main sequence, a braking effect independent of mass (and wind strength). The rotation rates of the youngest observed stars lean to an empirical initial velocity distribution with ⪅20% of critical velocity. Lastly, a limit in v sin i detection below 40–50 km s−1 seems to persist, especially in the upper part of the sHRD, possibly associated with the effect of microturbulence in the measurement methodology used.

Assessment of the effect of motorcycle autonomous emergency braking (MAEB) based on real-world crashes

Objective: Vehicles are increasingly being equipped with Autonomous Emergency Braking (AEB) and literature highlights the utility to fit a similar active safety system in Powered Two-Wheelers (PTWs). This research attempts to analyze the efficacy of PTW Autonomous Emergency Braking (MAEB) when functioning solely, and in the case where both the PTW and Opponent Vehicle (OV) have AEB installed. Methods: 23 crashes involving motorcyclists that occurred in metropolitan areas of Italy between 2009 and 2017 were selected. The “In-depth Study of road Accidents in FlorencE (InSAFE)” provides data for the study. Each crash was reconstructed in PC-Crash 12.1 software. The obtained simulation of the crash dynamics was then used to create the dataset of cases fitted with AEB and MAEB systems. A custom MAEB system was implemented with specifications based on literature. Results: The majority of crashes occurred on urban roads, at intersections, on dry asphalt, with clear visibility, and in daylight. The passenger vehicle was the most frequent opponent vehicle (70%). Almost half the sample involved the PTW rider traveling beyond the speed limit permitted on urban roads. MAEB was found to be applicable in 19 out of 23 real-world crashes allowing the avoidance of two crashes with the progressive triggering criteria (Time to Collision (TTC) − 1.0 s) and one crash in the case where both the PTW and OV have AEB installed with more conservative setups. MAEB simulations show important trends in the reduction of the PTW impact speed (ISR) from the conservative (TTC-0.6s) to standard (TTC-0.8s) to progressive (TTC-1.0s) triggering criteria. The mean impact speed reduction (ISR) becomes 8.6 km/h, 13.8 km/h, 19.1 km/h, respectively. Conclusions: The results suggested that MAEB may be extremely effective in the PTW impact speed reduction and that an earlier MAEB intervention is beneficial in achieving higher reductions in the PTW impact speed. Further, the effect of opponent vehicles also possessing AEB was studied, and it was found that this increased the likelihood of crash avoidance and greater reduction in crash severity in unavoidable circumstances.

Vortex dynamics in an electrically conductive fluid during a dipole–wall collision in presence of a magnetic field

We numerically investigate the flow physics generated by the collision of a vortex against a wall in an electrically conductive fluid. Governing magnetohydrodynamic equations are solved by the lattice Boltzmann method. Our findings demonstrate that the presence of a magnetic field modifies significantly the vortex dynamics. Specifically, it exerts a braking effect on the vortex that increases with the magnetic Prandtl number. Our results are linked to the transfer of energy between the velocity and the magnetic fields as well as to the evolution of their enstrophies.

A nature-inspired optimal design for a ventilated brake disc

Brake discs are critical automobile components that provide the braking effect and ultimately ensure the safety of passengers. Because of intermittent braking operations, brake discs are subjected to fluctuating loads and are provided with ventilation to facilitate cooling. The present study utilized a combination of response surface methodology parametric analysis, finite element analysis, statistical analysis, predictive modeling, and design optimization. Based on the response surface methodology design of experimental runs, ventilated brake discs were modeled considering the critical design parameters, viz., radius of center hole, thickness of inboard and outboard plate, height of vanes, and offset. Using finite element analysis, the brake discs were simulated under actual braking conditions for fatigue life cycles. Thirty-two (32) trial finite element analysis trials were performed. The obtained results were interpreted using ANOVA and an effective predictive model was established. Parametric analysis was performed using plots of response surface methodology and contours to predict the optimal parameter settings. In addition, two nature-inspired optimization techniques, the genetic algorithm and particle swarm optimization, were implemented and the optimal design parameter settings were determined for maximum fatigue life. The genetic algorithm and particle swarm optimization produced 7.67% better results than the parametric analysis, clearly demonstrating that the proposed design techniques exhibited significant performance improvement compared to widely used classical techniques.