Full-scale dynamometer tests of composite railway brake shoes: Effect of the resin-rubber ratio on friction performance and wear

Designing a friction material for a brake system entails considering the effects of each constituent and the interactions that they may present between them. In the present work, a characterization of the influence of the resin-rubber ratio in a brake block material is carried out. Railway brake shoes were produced and tested in a full-scale railway dynamometer in demanding conditions. The brake blocks had also their physical and mechanical properties tested. The progressive addition of resin was proven to heavily affect the friction level in dry and wet conditions. Interestingly, the use of 5% of resin showed significantly higher friction in wet conditions. This composition also presented more severe metal pick-up. The nature of the binder also affected wear rates (which were lower for lower resin contents), and the wear mechanism. The sample using only rubber presented thermal cracks and heavier delamination as specific failure modes. Differences on the microstructure of the friction materials were observed depending on the binder. A 5% of resin appears as a very interesting choice to avoid friction loss in wet environments without incurring in high wear rates, as long as metal pick-up is by different means diminished. Otherwise, a 100% of rubber as a binder grants the instantaneous friction stability that is often threaten by thermal fade.

Simulation of the Thermal Behavior of Cast Iron Brake Block during Braking Maneuvers

In recent years, the interest in monitoring the operating conditions of freight wagons has grown significantly to improve the safety of railway vehicles. The railway research group of the Politecnico di Torino has been working for years on the development of solutions to effectively monitor the operating conditions of passenger and freight rail vehicles. As part of the national Cluster ITS Italy 2020 project funded by Italian ministry of education, university and research (MIUR), the Politecnico di Torino has collected a considerable amount of data thanks to the wired and wireless prototypes developed. The data obtained are used in this paper for the validation and calibration of a finite element (FE) model that simulates the temperature variation of a cast iron brake block due to braking operations of an intermodal freight wagon. The developed model can be a useful tool to predict the temperature at the wheel–shoe interface as a function of the current operating conditions since a direct measurement is not easy to perform.

Characterization of train brake-blocks composite reinforced with aluminum-dross

Brake blocks are usually made from asbestos, metals and ceramics. It has been realised that asbestos discharges dangerous gases which can be harmful. This problem necessitated the search for human-friendly materials. Therefore, this paper studies the production and characterization of train brake blocks produced from clay reinforced with aluminum dross. This was done by producing samples of composite using clay from a deposit at Osiele and aluminum dross from Tower Rolling Mill Otta, both in Ogun state. The percentage composition of aluminum dross was varied from 0% to 25% to produce brake samples. Their wear rate, tensile strength, compressive strength, hardness, thermal conductivity and microstructure were analysed. The results from this project such as Ultimate tensile strength (UTS) of 7.4Mpa, Impact energy 6.92J, Hardness 28.8 HV, wear rate 0.0071g/sec and thermal conductivity of 0.01075 indicate that, with 5% aluminium dross it is possible to develop brake block that exhibits property recommended by Rail Industry Safety and Standard Board (RISSB). Keywords: Train, Brake blocks, Clay composite, Aluminum Dross, Mechanical properties.

Effects of Oil Palm Empty Fruit Bunch and Magnesium Oxide Volume Fraction on Mechanical Characteristics of Railway Brake Block Composite Material

Railway brake block is one of the most important components of the braking system of a railway vehicle. Materials for railway brake blocks are commonly made from metal or composite. The metallic brake blocks have some disadvantages that are heavy, low wear-resistant and has potential in generating a spark. While the composite brake blocks do not have those disadvantages. Natural fiber from oil palm empty fruit bunches as the waste from the production of palm oil can be used as a composite constituent. This composite brake blocks made from oil palm empty fruit bunches as reinforcement, phenol resin as matrix, and alumina, magnesium oxide and iron powder as a friction modifier. Density, hardness, coefficient of friction, compressive strength and flexural strength tests were carried out to determine the mechanical characteristic of the composite railway brake block material. The railway brake block test results consist of the density of 1.96 g/cm3, the hardness of 57.6 HRB, coefficient of friction of 0.43, the compressive strength of 37.1 MPa, and flexural strength of 33 MPa. There are three samples of volume fraction combination with 20% of oil palm empty fruit bunch in sample 1, 15% oil palm empty fruit bunch in sample 2 and 10% oil palm empty fruit bunch in sample 3. Percentage of MgO is adjusted to compensate the volume fraction of oil palm empty fruit bunch in the sample. Sample test results show that composite with volume fraction 10% of oil palm empty fruit bunch, phenolic resin of 30%, Al2O3 of 25%, MgO of 20%, iron powder of 15% has better mechanical properties for the alternative composite railway brake block material as compared to the other two.

An integrated numerical framework to investigate the running safety of overlong freight trains

Long freight trains up to 1500 m in length are currently not in regular operation in Europe. One of the important reasons for the same is high inter-wagon forces generated during the operation, especially when pneumatic (P-type) brake systems are used. For long trains with multiple locomotives at different positions along the train, radio communication with necessary fail-safe mechanisms can be used to apply the brakes. Long freight train operation on a given line is subjected to various attributes such as braking/traction scenarios, loading patterns, wagon geometries, brake-block materials, buffer types, track design geometries, etc., which are referred to as heterogeneities. The complex longitudinal train dynamics arising in the train due to various heterogeneities play a major role in determining its running safety. In this context, the maximum in-train force refers to the maximum force developed between any two wagons along the train during operation. The tolerable longitudinal compressive force is the maximum compressive force that can be exerted on a wagon without resulting in its derailment. Here, the authors adopt a bottom-up approach to model pneumatic braking systems and inter-wagon interactions in multibody simulation environments to study the complex longitudinal train dynamics behavior and estimate maximum in-train forces and tolerable longitudinal compressive forces, subjected to various heterogeneities. These two force quantities intend to facilitate a given freight train operation by providing guidelines regarding the critical heterogeneities, that currently limit its safe operation. In doing so, the authors propose the notion to have an operation-based approval for long freight trains using the simulations-based tool.