Numerical Modelling of a 3d Rail RCF ‘Squat’‐type Crack Under Operating Load

Abstract

The analysis is based on the 3D FE model of the rail Rolling‐Contact‐Fatigue (RCF) ‘squat’‐type crack, which tends to be common in tracks with high‐speed passengers and mixed traffic. The model incorporates the section of rail and a wheel of real geometry, in which the wheel is rolling over the running band of rail containing the ‘squat’‐type crack. The state of stress in the vicinity of the crack front is determined, and consequently the values and ranges of the stress intensity factors (SIFs) KI , KII andKIII at the crack front are calculated for the cycle of rolling. To simulate loading conditions occurring in practice, residual, bending and thermal stresses acting in the presence of the tractive force were taken into account. The results indicate a significant role of face friction and tractive force in the loading mechanism at the ‘squat’. The longitudinal and lateral residual stresses may also influence the loading cycles, especially for the cases with reduced friction between the crack faces. Reduction of the face friction coefficient to values close to zero creates conditions for crack propagation driven by the shear mode mechanism. These results were obtained under a project sponsored by the ERRI D173 Committee, Utrecht, The Netherlands.

An investigation into the causes of squats—Correlation analysis and numerical modeling

“…In 1990s the European Rail Research Institute (ERRI) carried out a RCF research program [2], in which Bogdański et al [6] modeled a squat as a plane oblique semi-elliptical crack. The state of stress in the vicinity of the crack front is determined, and the values and ranges of the stress intensity factors at the crack front are calculated.…”

Measurement of microslips of subsurface fatigue crack faces due to rolling loads

“…4 P n normal load R radius of the cylinder u, v in-plane displacement components relative to x and y respectively (mm) w 1 , w 2 out-of-plane displacement components along the z axis, determined on the basis of equations (2) and (3) respectively x, y, z Cartesian coordinate system x 1 , x 2 positions of the loading cylinder in relation to the crack tip during the rst and second exposures of the holographic plate respectively # angle between a normal to the holographic plate and the di racted beams according to the schematic representation shown in F ig. 4 wavelength of the light used to reconstruct the hologram…”

“…Analysis of the stress state in the proximity of the crack tip was made in order to predict crack propagation [1], and numerical models of such cracks were developed [2,3]. H owever, these models still contain the most uncertain and unreliable factor, that is, the crack face interaction [4,5].…”

Calculation of minimum crack size for growth under RCF between wheel and rail

“…Although the finite element method [5][6][7][8][9][10] is very comprehensive, it has the major drawback that its complexity makes model generation very timeconsuming, especially a three dimensional crack under the elliptical shape contact load, and solving the models is slower than any other alternative approaches. While the Green function method does not have wide applicability compare to the FEM, it gives fast and reasonable accuracy.…”

“…Fracture mechanics is concerned with providing a method [1, -2] for predicting the failure of a material by crack growth analysis. A great deal of research [5][6][7][8][9][10][11][12][13][14][15] has been made to predict crack growth during wheels rolling over a crack, and great advances have been achieved. But the calculation of MCSG has not been fully investigated yet.…”