This article presents a comparison of carbon dioxide emission during passengers and freight transporting by different transport modes. Because of significant diversity of transport means, the emissions expressed in grams per passenger kilometre or tonne kilometre were compared. Available data published in references were used to achieve this goal. The comparison revealed significant differences between transport modes as well as inside them, between transport means. High CO2 emission during aircrafts takeoff caused a necessity to take into account the flight distance for the air transport.
Recently a development of new rail steels takes place. Steels with bainitic microstructure are considered to be alternative for pearlitic ones, because they exhibit high strength and good toughness. Also their wear behaviour can outperform the other microstructures in some conditions. Nevertheless no or little attention is devoted to study how the use of bainitic rail steels influences wear processes of wheels. This article is an attempt to file this gap. The influence of slippage and rotational speed on wear behaviour of a B6 tyre steel mated with the first polish bainitic rail steel, in rolling-sliding, high-pressure, friction conditions was studied. For this study laboratory friction and wear tests were carried out on an Amsler apparatus. The effect of slippage and rotational speed on mass loss and coefficient of friction was determined. To study wear mechanisms optical microscopic observations were carried out. The dependence between test parameters and thickness of plastically deformed layer as well as fracture length and depth was assessed.Keywords: tyre steel, wear, coefficent of friction, wear mechanismsObecnie ma miejsce rozwój nowych stali szynowych. Stale o strukturze bainitycznej są uważane za materiały alternatywne wobec tradycyjnych stali perlitycznych, ponieważ wykazują wysoką wytrzymałość i odporność na pękanie. Również pod względem odporności na zużycie stale bainityczne mogą przewyższać stale o innych mikrostrukturach. W badaniach nad takimi stalami niewiele uwagi poświęca się wpływowi ich zastosowania na zużywanie kół kolejowych. Niniejsza praca stanowi próbę wypełnienia tej luki. Określono w niej wpływ poślizgu i prędkości ruchu obrotowego na zużycie próbek ze stali obręczowej gatunku B6, w styku z pierwszą, polską, bainityczną stalą szynową, przy wysokim nacisku w warunkach suchego tarcia tocznego z poślizgiem. W tym celu przeprowadzono badania tribologiczne na stanowisku Amslera. Ich wynikami było zużycie wagowe i współczynnik tarcia dla różnych poślizgów i prędkości obrotowych współpracujących elementów. Mechanizmy zużywania były badane za pomocą obserwacji mikroskopowych powierzchni po teście tribologicznym oraz obserwacji metalograficznych przekrojów próbek. Na ich podstawie określono również zależność grubości warstwy odkształconej plastycznie oraz długości i głębokości pęknięć od parametrów badań.
In the paper the results of sliding wear tests were used to model the dependence of steel volume loss on railway wheel tyres on selected material parameters and sliding conditions. The material properties included in this modelling were the hardness and chemical composition of the tyre material (specimens) and the hardness of the mating material (counter-specimens). The conditions for sliding were the initial maximum Hertzian pressure and the sliding distance. The tests were carried out in the ring-block system. Artificial neural networks were used for modelling. It was found that the constructed model made it possible to quantify the volume loss from the above–mentioned factors. A clear influence of the pressure, friction distance, and hardness of both cooperating materials on the studied wear was found. The influence of the chemical composition is less noticeable due to the rather narrow range of its allowable changes. The microscopic tests allowed us to identify the main wear mechanisms in the sliding friction of the tested tyre and rail steels.
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