Thermomechanical and Tribological Properties of SiC/Gr Reinforced Hybrid Aluminum Composite for Disc Brake Application

The disc brake motorcycle material has been developed by using aluminium matrix composite (AMC) reinforced with matrix particulate ceramic. The composite has many advantages: lightweight, high re-sistance to wear, and controllable strength by adjusting the reinforcement materials percentage. The main issue is the environmental factor that influences the surface properties of the disc. The research aims to study thermomechanical and tribology characteristics to determine the effect of the environmental factor on the composite's wear-out rate. The disc is made from matrix Al7Si6Mg9Zn composite matrix with 10% SiC and 10% graphite (v/v). The disc is produced by squeeze casting method and heated for 4 hours at 180 °C as artificial aging heat treatment. Thermomechanical characteristics are carried out by observing the temperature changes when a load is introduced to the disc. The pin-on-disc method is applied at three different speeds (60, 80, and 100 rpm) under the wet and dry surface on the disc for observing the tribo-logical properties. Thermomechanical characteristics of the disc are average braking time is 3.72 seconds, where the average braking distance is 515.8 cm at speed 40 km/hour with the average temperature of 46.12 °C. The wear-out rate results are steady, where the highest wear out rate for the dry surface is 0.725 mm3/N.m and 6.133 mm3/N.m for the wet surface at 100 rpm.

Design, characterization, and performance analysis of Miscanthus fiber reinforced composite for brake application

This study deals with the development of new friction materials by incorporating Miscanthus fiber (5, 10, and 15 weight %, noted Mat1, Mat2, and Mat3, respectively). The friction materials were tested for their physical, mechanical, and microstructural properties as per international standard. The performance analysis was carried out using Chase friction test rig. Results revealed that the biomass is beneficial with good fade, wear resistance, and recovery characteristics, with the same trend of other natural fibers. Therefore, this natural ingredient proved to be useful in the development of brake friction material.

An Evaluation of Derailment Mechanics and Derailment Analysis Methodologies

Detailed analyses of vehicle and train collisions are a common part of new vehicle design projects. It is relatively simple to describe appropriate collision scenarios for a train and the resulting collision mechanics are reasonably controlled if the trains remain upright and in-line. These scenarios are well suited to advanced dynamic finite element simulation codes. Alternatively, train derailment analyses are less common and have unique characteristics that make the analyses difficult. The derailment event can involve the interaction of many cars and have a relatively long duration compared to other crash events. Freight derailments can involve trains in excess of 100 cars long and the duration of the derailment response can be on the order of a minute before coming to rest. Further complicating the analysis are the many parameters that are not well characterized or controlled. The motions of rail cars after leaving the tracks are not well known and difficult to model. The wheels and trucks can plough through ground or remaining track sections. The material properties and geometry of the ground can have large variations and are typically not well known or characterized for specific derailment events. Additionally, the geometry of the surrounding terrain can have a wide range of variability at derailment sites. As a result of these complexities, there are far fewer standardized methodologies used for the analysis of derailments. The detailed finite element models are applied in some cases, but the computational requirements to model these events in high fidelity are quite high. This paper provides a review of some past derailment modeling efforts and recent investigations and analyses of derailment events to provide insights into the derailment mechanics of freight trains. The objective is to assess the relative magnitudes of effects such as the braking characteristics, brake application delay time, and blockage force caused by the derailed and overturned cars on the subsequent deceleration of the trailing cars on the rail.

Selection of optimal composition of MR fluid for a brake designed using MOGA optimization coupled with magnetic FEA analysis

The design of Magnetorheological (MR) brake and the composition of MR fluid (MRF) used in it have a significant effect on its performance and hence an effort has been made in this study to determine the optimal dimensions of MR brake and composition of MRF suitable for the brake application. Initially, optimum parameters of MR brake were computed considering the properties of commercially available MRF 132DG fluid using multi-objective genetic algorithm (MOGA) optimization. This was performed in MATLAB software coupled with magnetostatic analyses in ANSYS APDL software. The braking torque of designed MR brake utilizing MRF 132DG fluid was experimentally determined and validated with analytical ones. Further, selection of optimal composition of MRF was done considering In-house MRF samples composed of different combinations of particle mass fractions, mean particle diameters and base oil viscosities. A design of experiments (DOE) technique was employed and braking torque corresponding to the synthesized MRF samples at different speeds and current supplied were measured along with the variation of shaft speed during braking process. Grounded on the experimental results, using MOGA optimization technique, MRF composed of smaller sized iron particles (2.91 microns) with mass fraction of 80.95% and lower viscosity base oil (50 cSt) was selected as optimal composition of MRF for use in MR brake. Maximization of field induced braking torque and minimization of off-state torque were chosen as the objective functions for both the optimal design of MR brake and selection of optimal composition of MRF. Finally, the sedimentation stability of MRFs were investigated.

THERMAL CONTROL INVESTIGATION OF ROLLING-STOCK SHOE BRAKES BY SIMULATION METHOD

The development of heavy speed freight train communications in the Russian Federation results in the increased thermal loading of braking system elements of rolling-stock, in particular, in shoe brakes. Taking into account the requirements of branch program documents on wheel life increase, it is evident that the further development of freight communications requires a complex application of thermal diagnostics means for auto-brake equipment of rolling-stock during a train motion. The statistics shows that the fifth part of wheel pair failures is connected with thermal-mechanical damages and the situation goes on to be aggravated. In view of this hardware and software means for thermal diagnostics of shoe brakes require further improvement. The purpose of this paper is the process investigation of shoe brake thermal control by method of computer simulation and the estimate of infrared optics position impact upon control results. There is considered a model for the definition of a scanning path and computation of a signal level being part of a complex simulation model of wheel thermal control. The model offered is based on the methods of solid dynamics system investigations in the basis of which there is an application of theorems on mass center motion and changes of a solid kinetic moment. The model is used for finding a form and a spot area at every time moment of scanning by a solution of a problem on a dynamic spatial intersection of a wheel surface with the control area. There are considered different versions of optics orientation to an object of control for each of which for the first time there are obtained calculated thermal signals from the object under control. The analysis has shown that at the optics orientation to wheels from the outside a wheel tread appears to be in the control area that allows defining a maximum temperature of a wheel. But at the realization of emergency brake application a sharp short-time temperature increase of a tread is possible which indicates an improper operation of a brake unit. The optics orientation to a wheel from its inner side allows excluding false alarm indices at emergency brake application. The correctness of the results shown in the paper is confirmed by convergence with the results of wheel heating monitoring and environmental tests of experimental complexes of thermal control means of shoe brakes.

Interfacial characteristics between mineral fillers and phenolic resin in friction materials

Mineral fillers are indispensable constituent part of friction materials, which are capable of improving and stabilizing coefficient of friction, decreasing wear, enhancing thermal conductivity and reducing costs of friction materials, in addition, decreasing the noise in brake application. Based on their roles in the friction materials, mineral fillers are classified into abrasives, lubricants, functional fillers, and space fillers. Herein, four typical commercial mineral fillers, namely quartz, graphite, expanded vermiculite, and barite were studied for revealing their effects on the performance of friction materials. The composition, thermal stability, structural characteristics such as surface area, pore volume, and distribution of the pore size, and thermal conductivity of these mineral fillers were researched mainly by X-ray diffraction (XRD), differential scanning calorimetry and thermogravimetry (DSC-TG), N2 adsorption–desorption isotherms, and thermal conductivity tester. Moreover, in order to illustrate the interfacial characteristics of mineral-based in friction materials, four ideal brake pads only consisting of mineral filler, BaSO4 and phenolic resin were prepared. Microstructure and combination of mineral fillers and phenolic resin were investigated by scanning electron microscopy (SEM), polarizing microscope, and Fourier transformation infrared spectroscopy (FTIR). The results showed that different types of material fillers had special functions for friction materials, and they combined with phenolic resin mainly in a physical way.

Maximum temperature of the disc during repeated braking applications

A computational finite element model of a brake disc for determining transient axisymmetric (two-dimensional) temperature field during repeated brake application has been proposed. The presented research is a subsequent stage of a previous study on the coupling of velocity and maximum temperature for a single braking in accordance with the system of equations of heat dynamics of friction and wear. In the analysed case, changes in the mean, flash, maximum and bulk temperature of the disc were determined and discussed. The calculations were carried out at the temperature-dependent coefficient of friction, the thermophysical properties of cast-iron disc combined with cermet brake pads and the time-varying contact pressure. The obtained results were compared with the reference values from the braking simulation at constant operating parameters and independent of temperature properties of materials. It was shown that the maximum values of the mean temperature for both cases differed slightly during the entire process. The flash temperature determined from the heat dynamics of friction and wear system of equations was the highest at the beginning and gradually decreased with the number of brake applications.

Adaptivity as a Property to Achieve Resilience of Load-Carrying Systems

Load-carrying systems often suffer from unexpected disruptions which can cause damages or system breakdowns if they were neglected during product development. In this context, unexpected disruptions summarize unpredictable load conditions, external disturbances or failures of system components and can be comprehended as uncertainties caused by nescience. While robust systems can cope with stochastic uncertainties, uncertainties caused by nescience can be controlled only by resilient load-carrying systems. This paper gives an overview of the characteristics of resilience as well as the time-dependent resilient behaviour of subsystems. Based on this, the adaptivity of subsystems is classified and can be distinguished between autonomous and externally induced adaption and the temporal horizon of adaption. The classification of adaptivity is explained using a simple example of a joint brake application.

Multibody analysis of longitudinal train dynamics on the passenger ride performance due to brake application

In this paper, longitudinal train dynamics and coupler forces were modelled based on experimental results of Research Design and Standard Organisation and from the available literature. The model was solved numerically in MATLAB. Moreover, a multibody model was developed in Universal Mechanism software considering a locomotive and two coaches that were validated with the mathematical model by comparing acceleration responses of locomotives and coaches running at 150 km/h and then applying emergency braking. The validated model in the Universal Mechanism software was extended and used for additional study. For the case study, the Rajdhani Express train was considered running at its maximum operational speed of 160 km/h with track gradient of New Delhi and Agra Cantt station. The performance of the rail vehicle in five braking phases was evaluated. The maximum compression force in coupler increased after the application of each brake phase. Moreover, the maximum compressive coupler force of 149 t was experienced at the third quarter of the train. However, the ride quality and comfort were within the satisfactory range prescribed by Research Design and Standard Organisation.