The cover photo of July 2019 issue is dedicated to the 41st anniversary of the first reported synthetic approach of dendritic hyperbranched structure. The cover photo adopted from the Valer et al., where they reported the preparation of dendritic hyperbranched copolymers based on bis(hydroxyl methyl) propionic acid polyester and studied the architecture - behavior - properties relationship. Dendritic structures are known for their perfect chemical definition, highly dense structure, and a well-defined number of surface functionalities. The soft multifunctional modifications could be compliant to valuable flexibility for embedding different chemical moieties on the surface either within the structure or at the core.
Influence of railway-track grinding on the track material condition and tribological behaviour
Eckart Uhlmann1, Mykola Bobyr2, Yuriy Borodiy2, Pavlo Lypovka1, Pavel Protsenko2, Janis Thalau1,*
1Chair of Machine Tools and Manufacturing Technology, Institute for Machine Tools and Factory Management (IWF), Technische Universität Berlin, Berlin, 10587, Germany
2Igor Sikorsky Kyiv Polytechnic Institute, National Technical University of Ukraine, Kiev, 03056, Ukraine
Adv. Mater. Lett., 2019, 10 (7), pp 449-454
Publication Date (Web): Jan 14, 2019
Copyright © 2019 VBRI Press
As societies have a rising demand regarding mobility as well as an increasing ecological awareness, the energy efficiency, noise emissions and availability of transportation in urban environments become essential for growing cities. In this context, the role of rail-bound traffic in urban environments as well as in intercity-connections is of rising importance. To guarantee travelling comfort and safety, shorter downtimes as well as power efficiency, the condition of the railway network is subject to rising quality requirements. Therefore, the maintenance, repair and overhaul as well as the material quality of railway-tracks is faced with new challenges. An important part of track maintenance is track grinding. To ensure an economically reasonable track life cycle and to prolong the time period between repair tasks, grinding processes should not induce damage such as cracks and hardening. On the other side, high productivity of track grinding, which tends to induce damage, is crucial to reduce disruptions and delays from repair. Research work presented in this paper aims at reducing the lack of knowledge concerning interactions between the track grinding parameters, grinding tool specifications and the topology of the track’s surface and damage of the track’s sub surface. Industrial track grinding processes were tested under laboratory conditions with a variation of the grinding wheel circumferential speed and depth of cut. Afterwards the ground tracks specimens were evaluated with regard to the achieved surface roughness as well as the micro-hardening, induced cracks and residual stresses in the sub surface zone. Furthermore, the influence of different external factors such as environmental conditions on the results of track grinding is analysed by evaluating the influence of the track’s initial temperature on the process results. As a result, the main influencing factors on the surface quality and the sub surface damage in track grinding were identified and their influence on the tribological behaviour of the ground tracks in contact with an opposing steel disc was analysed. Based on these considerations, recommendations on eligible track grinding strategies, which lead to highly productive yet low-damage track repair, are derived.
Railway maintenance, track grinding, tribology.