Fatigue crack propagation behavior in railway steels

Abstract

Purpose -The present paper aims to characterize the fatigue crack propagation behavior of wheel and rail steels, in particular the AVE wheel steel and an UIC60 rail steel, including several R-values and near threshold behavior. To accomplish this objective, mode I fatigue crack growth tests were performed according to the ASTM E647 standard on C(T) specimens taken from a Spanish high-speed AVE train used wheel and a UIC60 rail, tested with 0.1, 0.4 and 0.7 load ratios. Design/methodology/approach -In the present study, the two different methodologies presented in the ASTM E647 standard were used to characterize the fatigue crack propagation behavior of the two studied materials. The K-decreasing test procedure was used to characterize fatigue crack propagation near the threshold, whereas the K-increasing with constant load range method was used in the Paris law regime. Findings -It was observed that for the wheel a small influence of R-ratio was found, with greater R implying higher fatigue crack growth rates. For the rail, the influence is small, and for large values of DK, it is slightly reversed. The near-threshold results obtained indicate lower threshold values for higher R-ratio, a fact that is possibly associated with crack closure phenomena. A scanning electron microscope (SEM) study of fatigue crack propagation surfaces identified a random behavior in the striation orientation for both materials and no correlation was found between striation spacing and actual fatigue crack growth rate. Originality/value -R-ratio and threshold behavior of fatigue crack propagation of a steel used in high-speed train wheels, as well as of UIC60 rail steel, were studied, with the objective of generating data to be used in maintenance and damage tolerance models.

Efeito Da Razão R Entre Tensões Na Resistência Ao Crescimento De Trinca Por Fadiga De Cinco Aços De Aplicação Em Trilho Ferroviário

“…Percebe-se o efeito deletério do aumento da razão R no comportamento de todos os aços estudados, o que está de acordo com a literatura [16][17][18][19]. Posto isto, deve-se comentar que a forte sensibilidade à razão R entre tensões para os aços estudados indica o risco de ocorrência de uma fratura catastrófica, caso ocorra uma variação de carregamento na linha ferroviária.…”

Experimental and numerical study for detection of rail defect

“…The cracks in rails may initiate near surface area or at the surface and propagates below the surface due to high traction forces between the rail and wheel contact, this phenomena is called Rolling Contact Fatigue (RCF). Several studies of crack growth rates in wheel-rail interaction are published in the literature [19][20][21]. The critical size of a crack should be defined as the size that can be expected to cause failure in the structure, this crack size can be estimated according to Linear Elastic Fracture Mechanics (LEFM) from the stress intensity factors compared to the material toughness.…”

X-Ray Diffraction Residual Stress Measurements for Assessment of Rolling Contact Fatigue Behaviour of Railway Steels

“…The AVE train wheel is a real used wheel that reached the geometrical limits for continued usage. In order to characterize these two materials, chemical composition, mechanical properties, microstructure and hardness measurements, were carried out [5]. The chemical composition of the studied wheel and rail steels, obtained by optical emission spectrometry on samples taken from the AVE wheel and UIC60 rail is presented in Table 1.…”

“…Both materials present a pearlitic microstructure. Fatigue crack growth rate determination tests were also performed in order to characterize the fatigue crack propagation behaviour [5], as this is essential for the objectives of this project. Twin disc test machines are commonly used to simulate heavy loaded contacts like the wheel/rail contact and to predict materials behaviour in rolling contact fatigue.…”