Experimental Investigations on the Stress State in the Bearing Structure of a Special Wagon to Transport Liquid Iron

In order to increase productivity, to reduce energy consumption and for environmental protection, a special wagon intended for the transport of liquid pig iron, in steel mills, it was designed and manufactured. This wagon consists of an especial chamotted torpedo, with a capacity of 300 tons, rested, at each end, by means of a box beam, on two buggies, with four axles each one. To evaluate the mechanical behavior of this wagon during service, its prototype was investigated experimentally in terms of the stress and strain state. Due to difficulties encountered related to the long duration of loading and unloading time of the torpedo pot with liquid cast iron and due to very large dimensions of the carriage gauge, experimental investigations were performed on the torpedo pot and box beam models, manufactured at scale. The buggy structure was investigated on a special stand, set up in the laboratory of Strength of Materials Department of the Polytechnic University of Bucharest. The torpedo pot and box beam were investigated using two combined experimental techniques (brittle coatings technique and resistive strain gauge technique). Brittle coatings technique was used to identify the principal stresses directions, which then were applied electro-resistive transducers. Using strain gauge amplifiers the principal strains were measured, and principal stresses in measurement points were calculated. The results of these studies have led to changes of constructive solutions in the case of some substructures, contributing to increase the operational safety of the wagon.