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Assessing surface fatigue crack growth in railway wheelset axle

Rudavskyi D. V., Kaniuk Yu. I., Duriagina Z. A., Kulyk V. V., Shefer M. S., Dolinska I. Ya.

Archives of Materials Science and Engineering

2020

Vol. 106, nr 2

59--67

Purpose: The aim of the proposed research is to create a calculation model of surface fatigue crack growth at the axle of railway wheelset working under operational loads. Design/methodology/approach: The energy approach of the fracture mechanics was used to formulate the calculation model of fatigue crack propagation at the wheelset axle surface. The method of least squares was used to determine the investigated material mechanical constants that the kinetic equations of the calculation model contain. The system of differential equations of crack growth kinetics was solved numerically using the Runge-Kutta method. Findings: On the basis of the energy approach of the fracture mechanics the calculation model of fatigue macrocrack growth in three-dimensional elastic-plastic body in case of a mixed-mode I+II+III macromechanism of fracture has been built. On the basis of the created calculation model, the kinetics of the growth of fatigue cracks was investigated both in the middle part of the wheelset axle and in the axle journal. Research limitations/implications: The results obtained on laboratory specimens should be tested during a real railway wheelset axle investigation. Practical implications: The created calculation model can be used in practice to formulate method of residual lifetime estimation of railway wheelset axle. Originality/value: It was shown, that surface crack kinetics depends not only on the crack initial area but also significantly depends on the crack edge geometry and comparatively small crack-like defects at the wheelset axle surface can reach critical sizes in comparatively short run. It has been found that mechanical shear stresses caused by the weight of the loaded railway wagon in the cross section of the wheelset axle journal can significantly accelerate the growth of the transverse fatigue crack at the axle surface, reducing the period of crack subcritical growth by about 20%.

Use of e-learning in teaching fundamentals of materials science

Dobrzański L. A., Brom F., Brytan Z.

Journal of Achievements in Materials and Manufacturing Engineering

2007

Vol. 24, nr 2

215-218

Purpose: The main aim of this article is to present the usage of educational platform Moodle in teaching Fundamentals of Materials Science in the Institute of Engineering Materials and Biomaterials at Silesian University of Technology in Gliwice, and to analyse the efficacy of e-learning as the means of introducing education within a traditional model. Design/methodology/approach: This article contains the description of learning within the mixed mode, which is education embracing a face to face method and distance learning method for the first-year students. The comparison of the efficacy of mixed mode learning versus traditional learning will be presented. Findings: The efficient method of assisting remotely the e-learning students acquiring skills and knowledge at a varying pace has been developed, providing them with the personalised support. Research limitations/implications: Larger population of students should be tested so as to give measurable results, which would imply what needs to be worked on and what changes to introduce in order to improve the e-learning process. Originality/value: The course presented in this article confirms that e-learning enables the introduction of the new education formula, which may embrace advantages of traditional teaching and distance education as far as Materials Science is concerned.