An Effect of a Carbon-Containing Additive in the Structure of a Friction Material on Temperature of the Wet Clutch Disc

This paper consists of two parts. The first one contains a description and methodology of the composite material used as friction material in clutches. Four variants of such material, differing in the type of carbon additive (the elemental graphite, pencil graphite and foundry coke powder of various fractions) were considered. Thermal conductivity, thermal diffusivity as well as the specific heat all materials were determined experimentally. On the inertial IM-58 stand, a simulation of the braking process of the friction pair consisting of a steel disc with friction material and a counterpart in the form of a homogeneous steel disc was carried out. On this basis, averaged coefficients of friction, unchanging in the entire sliding process, were found for the four friction pairs. The experimental data obtained in the first stage were used in the second stage to develop two (2D and 3D) numerical models of the friction heating process of the friction pairs under consideration. For four variants of the friction material, a comparative spatial-temporal temperature analysis was performed using both models. It was found that a simplified axisymmetric (2D) model can be used to estimate the maximum temperature with high accuracy. The lowest maximum temperature (115.6 °C) obtained for the same total friction work was achieved on the friction surface of the material with the addition of GP-1.

Substantiation of the influence of changes in the coefficient of axle distribution of braking force on the handling of a passenger car

The article considers the change of the radius of the instantaneous center of rotation of a car moving along a curved trajectory during braking, taking into account the lateral input of the wheels of both axles of cars, both equipped with electronic tracking systems and not equipped with such. A criterion for assessing the controllability of cars moving on a curved trajectory in a braked state, by comparing the ratio of the current speed of the car to the longitudinal base with the ratio of the coefficients of lateral tire input to the product of the longitudinal base of the car, mass and cosines. It is established that the radius of instantaneous rotation of the longitudinal axis of the car moving along a curved trajectory during braking depends on the speed of the center of mass of the car, the coefficient of axle distribution of braking force, physical characteristics of applied tires, steering wheel angle and design and weight parameters. As a result, it allows you to set controllability. The authors obtained dependences that will create new algorithms for the operation of modern electronic control systems for stabilizing the longitudinal axis of a braked car, taking into account the speed of the car, its design and weight characteristics, the main characteristics of its braking system (coefficient of axle braking force distribution), physical characteristics used tires on wheels and connect them to the angles of the steered wheels, controlling the deviation of the longitudinal axis, which allows the driver to maintain the possibility of quite sharp maneuvers directly in the braking process, moving along a curved trajectory.

Review of the coatings used for brake discs regarding their wear resistance and environmental effect

Wear of a friction pair of brake (brake disc and pads), in addition to reducing the active safety of vehicles, leads to the formation of particles that can affect the environment and human health. In addition to the technologies that are being developed for the collection of particles created by the wear of brakes during braking process, today new materials are being introduced, as well as various technologies for processing friction pairs with the aim of reducing brake wear and thus the formation of particles. Furthermore, today, technologies for coating (cladding) the friction surfaces of disc brakes with some materials are increasingly applied and researched, in order to reduce the wear intensity (wear rate) of disc brakes, i.e. the emission of particles created by wear of friction pairs. The aim of this paper is to analyse and review different deposition techniques and materials used for brake discs coatings, as well as the effect it has on the wear rate of friction pair. There are many coating deposition techniques, and special attention is paid to the technology of laser hardfacing of brake rotors.

Optimization of Train Energy Cooperation Using Scheduled Service Time Reserve

The main aim of the paper was to develop an innovative approach to the preliminary estimation possibility of train energy cooperation based on data from timetables, without traction calculations. The article points out the need to strive for sustainable and environmentally friendly transport. It was pointed out that rail transport using electric traction is one of the more ecological branches of transport. It also offers a number of possibilities for improving energy efficiency and reducing energy consumption, one of which is the recovery and reuse of energy lost in the electrodynamic braking process. The main ways in which such energy can be used are listed, but the focus is mainly on the aspect of the so-called “energy cooperation” of trains. Then, the current state of the research and knowledge on the narrowed scope of rail traffic management and recuperative braking in rail transportation is presented; an innovative approach to the indirect optimization of the amount of recuperated electrical energy immediately usable by another vehicle by maximizing the duration of energy co-optimization is proposed; and the authors’ function is proposed to enable optimization, taking into account various parameters. The optimization was performed with the use of a proprietary, multi-criteria objective function and the Solver optimization module. Finally, the results obtained using the proposed approach are presented and illustrated with the example of train timetables used by some of the largest railway stations in Poland.

AN APPROACH TO EVALUATION OF FREIGHT TRAINS BRAKING EFFICIENCY BY THE RESULTS OF EXPERIMENTAL STUDIES IN COMPLIANCE WITH HOST 34434-2018 REQUIREMENTS

The approach of experimental study of the freight trains braking efficiency using computer simulation based on the implementation of the simulation model in the form of a differential equation of the wagon motion during braking, is proposed. The methodology of experimental studies is based on universal formulas for power-law dependences of braking parameters. The braking efficiency is evaluated by the use of computer software packages written in VBA (Visual Basic for Application) in Excel. The software package al-lows you to increase the automation of testing, the accuracy of calculations, to reduce the time for testing, and also minimize the number of errors caused by the human factor. The presented methodology significantly extends the number of parameters of the braking process used to analyze the braking efficiency of a freight train based on the results of running braking tests: actual values of braking coefficients; braking distances of a freight train not only on the site, but also on normalized gradient descents for a given number of wagons in the train, taking into account the increase in the braking force along the wagons in the train formation; actual values of wheel and rail adhesion coefficients during braking; the deceleration of the freight wagon and the train during braking, as well as the braking time. Examples of computational and experimental studies of a freight train with tread brake are given. A comparative analysis of experimental and computational studies demonstrates sufficiently satisfactory matching of their results. Key words: freight train, braking distance, braking speed, braking coefficient, increase in braking force, mathematical model, trend line, braking wave.

Thermo-Structural Analysis of Brake Disc-Pad Assembly of an Automotive Braking System

Braking is a phenomenon of stabilizing a moving vehicle to rest by actuating the braking system. The available kinetic energy from the dynamic body is transformed into mechanical energy by the braking system which is further converted into thermal energy for its dissipation into the surroundings. During the process of braking, the frictional contact between the brake disc and brake pad creates enormous amount of heat elevating the temperature of the system to a higher level. The objective of this numerical study is to minimize the heat produced during the braking process. Three unique ventilated brake disc and two brake pad profiles were developed using PTC Creo modelling tool and were subjected to ANSYS workbench to evaluate its thermal and structural performance with a braking cycle time of 4.50 sec. Total deformation, equivalent stress, temperature distribution and total heal flux were assessed. Based on the study, ventilated disc 3 can be the possible design with either of the brake pad profiles for effective usage in the automotive braking system.

Tractor-trailer-train braking time sequence detection based on monocular vision

The tractor-trailer-train at the braking process prone to braking instability caused by asynchronous braking between the shafts. With respect to the lack of intelligent detection of Braking Time Sequence (BTS), a non-contact dynamic detection scheme of intelligent vehicle BTS is proposed. Based on the monocular vision principle, the edge markers of tractor-trailer train tires are identified, and the tire slip rate is solved. The noise reduction of the collected image is processed. The marker area is obtained by Blob analysis. This region at the image to be matched is identified by the template matching algorithm based on contour. The camera is calibrated by Zhang’s calibration method. In order to verify the effectiveness of the detection scheme, the real vehicle test was carried out. The test results show that the error of slip rate solution is below 4.2%.

Temporal loss boundary engineered photonic cavity

Losses are ubiquitous and unavoidable in nature inhibiting the performance of most optical processes. Manipulating losses to adjust the dissipation of photons is analogous to braking a running car that is as important as populating photons via a gain medium. Here, we introduce the transient loss boundary into a photon populated cavity that functions as a ‘photon brake’ and probe photon dynamics by engineering the ‘brake timing’ and ‘brake strength’. Coupled cavity photons can be distinguished by stripping one photonic mode through controlling the loss boundary, which enables the transition from a coupled to an uncoupled state. We interpret the transient boundary as a perturbation by considering both real and imaginary parts of permittivity, and the dynamic process is modeled with a temporal two-dipole oscillator: one with the natural resonant polarization and the other with a frequency-shift polarization. The model unravels the underlying mechanism of concomitant coherent spectral oscillations and generation of tone-tuning cavity photons in the braking process. By synthesizing the temporal loss boundary into a photon populated cavity, a plethora of interesting phenomena and applications are envisioned such as the observation of quantum squeezed states, low-loss nonreciprocal waveguides and ultrafast beam scanning devices.

Full-Scale Train-to-Train Impact Test and Multi-Body Dynamic Simulation Analysis

When a train crashes with another train at a high speed, it will lead to significant financial losses and societal costs. Carrying out a train-to-train crash test is of great significance to reproducing the collision response and assessing the safety performance of trains. To ensure the testability and safety of the train collision test, it is necessary to analyze and predict the dynamic behavior of the train in the whole test process before the test. This paper presents a study of the dynamic response of the train in each test stage during the train-to-train crash test under different conditions. In this study, a 1D/3D co-simulation dynamics model of the train under various load conditions of driving, collision and braking has been established based on the MotionView dynamic simulation software. The accuracy of the numerical model is verified by comparing with a five-vehicle formations train-to-train crash test data. Sensitivities of several key influencing parameters, such as the train formation, impact velocity and the vehicle mass, are reported in detail as well. The results show that the increase in the impact velocity has an increasing effect on the movement displacement of the vehicle in each process. However, increasing the vehicle mass and train formation has almost no effect on the running displacement of the braking process of the traction train. By sorting the variables in descending order of sensitivity, it can be obtained that impact speed > train formation > vehicle mass. The polynomial response surface method (PRSM) is used to construct the fitting relationship between the parameters and the responses.

Mechanical and Dynamic Maps of Disc Brakes under Different Operating Conditions

The operating conditions during the braking process in an automobile affect the tribological contact between the pad and disc brake, thus, influencing the times and distances of braking and, in a more significant way, the safety of the braking process. This mathematical work aimed to provide a general visualization of the disc brake’s mechanical, dynamic, and thermal behavior under different operating conditions through 2D maps of the power dissipated, braking time, and braking distance of a disc brake with a ventilation blade N- 38 type. However, the dissipated energy on the disc brake in terms of temperature was analyzed considering Newton’s cooling law and mathematical calculations through classical theories of the dynamic and mechanical behavior of the disc brakes. For this purpose, the Response Surface Methodology (RSM) and Distance Weighted Least Squares (DWLS) fitting model considered different operating conditions of the disc brake. The results demonstrate that the disc brakes can be used effectively in severe operational requirements with a speed of 100 km/h and an ambient temperature of 27 °C, without affecting the occupant’s safety or the braking system and the pad. For the different conditions evaluated, the instantaneous temperature reaches values of 182.48 and 82.94 °C, where the high value was found for a total deceleration to 100 km/h to 0, which represent a total braking distance of around 44.20 to 114.96 m depending on the inclination angle (θ). Furthermore, the energy dissipation in the disc brakes depends strongly on the disc, blades and pad geometry, the type of material, parameters, and the vehicle operating conditions, as can be verified with mathematical calculation to validate the contribution of the effectiveness of the braking process during its real operation.