Some comments on surface cracks in rails

Abstract

A B S T R A C TThe present work considers the problem of whether a shallow angle surface crack on a rail may propagate either parallel or perpendicular to the surface. After referring to a classification of crack-like defects, a distinct surface crack with a typical length of 1 mm and more, inclined to the surface by an angle of approx. 30 • , is introduced. Then various strain and stress states are discussed (eigenstress, residual and load stress state) which may control the crack growth. Stress intensity factor equations are provided for the internal and load stress states. In particular, the deformation process due to a single pass (overrolling) by a wheel is investigated. Recommendations are presented on how to relate the stress intensity factor ranges to the actual deformation process. For a typical loading condition, the positive part of the mode I stress intensity factor range is near to the effective threshold value of a rail steel. The influence of the material and its strength on the crack propagation behaviour is discussed qualitatively.

Fatigue crack closure: a review of the physical phenomena

“…It is well known that residual stresses significantly affect the fatigue crack propagation behaviour . Macroscopic residual stresses can be considered as an additional applied static loading, and they change locally the stress ratio.…”

Surface effects on time-dependent fracture parameter of subsurface crack in plates under tension

“…To date, most efforts have been devoted to analyzing the interaction of surface-crack and multiple cracks under linear-elastic and elastic-plastic fracture mechanics regimes (Leek and Howard 1996;Moussa et al 1999;Sethuraman et al 2003;Carpinteri et al 2004;Feng and Xu 2006;Fischer et al 2006). The existing studies on this issue are focused on the methodology of fracture parameter analysis to obtain a quantitative description on the interaction of multiple cracks (Murakami and Nemat-Nasser 1982;Krishnamurthy and Raju 1990).…”

Interaction between cracks and microstructure in three dimensions for rolling contact fatigue in railway rails

“…Fischer et al . discussed factors determining the difference of rail steels concerning cracks . They concluded that tensile strength alone is not sufficient to explain the difference in performance in field trials of head hardened grades and normal pearlitic grades, for example 900A seen by Heyder and Girsch .…”