Residual Stress Characterization by X-Ray Diffraction and Correlation with Hardness in a Class D Railroad Wheel
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JMEPEG https://doi.org/10.1007/s11665-020-05097-x
Residual Stress Characterization by X-Ray Diffraction and Correlation with Hardness in a Class D Railroad Wheel A.B. Rezende, S.T. Fonseca, D.J. Minicucci, F.M. Fernandes, P.F.S. Farina, and P.R. Mei (Submitted May 15, 2020; in revised form August 12, 2020) This article focused on the microstructure characterization and residual stress measurements of the flange from classes D and C railway wheels (called 7D and 7C steel, respectively) to contribute with the residual stress level on new forged wheels flange area. A correlation with the hardness was conducted. The residual stress was measured in three points of the flange using the x-ray diffraction technique, and the microstructure characterization on SEM microscopy. We found the 7C steel has fine pearlite and ferrite microstructures, and 7D steel has degenerated pearlite and bainite microstructures. In the 7D steel, the compressive residual stress in the flange region was higher than in the 7C steel, which is related to the presence of bainite on the microstructure. There was a correlation between the hardness and residual stress value. The knowledge of the residual compression stress level is important for safety train wheels operation. The traction stress generated by the brake system on the wheel is attenuated by residual compression stress. Keywords
heavy haul, microalloyed steel, railway wheel, residual stress, x-ray analysis
1. Introduction Railroad transportation has been widely used to move people and the economy of the countries over the years and has supported the development of many regions in the world (Ref 1). To increase the economic viability of the transport, researchers work to improve the transport safety, the weight capacity, and the train velocity (Ref 2, 3). In countries like Australia for example, the weight transported achieves 40 tons/ axle (Ref 4). To support this weight increase, the development of new railway wheels is required. The Heavy Haul category (class D by Association of American Railroad-AAR) is the recent class of the railway wheels that have been developed to meet this demand. In these wheels, niobium, vanadium, and molybdenum are added in usual medium carbon steel, attaining higher toughness, mechanical, and wear resistance (Ref 5). The high load on heavy haul operation induces high brake stress on the wheel, for this reason is so important to know and evaluate the residual compressive stress on class D wheels, in order to guarantee the safety operation for these wheels (Ref 6, 7). Besides, the flange supports the weight when the train passes by a curve stretch, and in this situation, higher tangential forces and contact stresses are detected (Ref 8). Residual stress is resulting from wheels manufacturing, and with control, it is beneficial to the wheel rolling contact fatigue (Ref 9). The
A.B. Rezende, S.T. Fonseca, F.M. Fernandes, P.F.S. Farina, and P.R. Mei, Faculty of Mechanical Engineering, University of Campinas, Campinas, SP 13083-860, Brazil; and D.J. Minicucci, DJ Consult
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