Nucleation of squat cracks in rail, calculation of crack initiation angles in three dimensions

A numerical model of wheel-track system is developed for nucleation of squat-type fatigue cracks in rail material. The model is used for estimating the angles of squat cracks in three dimensions. Contact mechanics and multi-axial fatigue analysis are combined to study the crack initiation mechanism in rails. Nonlinear material properties, actual wheel-rail geometries and realistic loading conditions are considered in the modelling process. Using a 3D explicit finite element analysis the transient rolling contact behaviour of wheel on rail is simulated. Employing the critical plane concept, the material points with the largest possibility of crack initiation are determined; based on which, the 3D orientations/angles of the possible squat cracks are estimated. Numerical estimations are compared with sample results of experimental observations on a rail specimen with squat from the site. The findings suggest a proper agreement between results of modelling and experiment. It is observed that squat cracks initiate at an in-plane angle around 13°-22° relative to the rail surface. The initiation angle seen on surface plane is calculated around 29°-48°, while the crack tend to initiate in angles around 25°-31° in the rail cross-section.

[1]  Stanisław Bogdański Predicting the growth of RCF crack with the use of the 3D multi size finite element model. , 2005 .

[2]  Mohammadali Farjoo,et al.  Modelling a squat form crack on a rail laid on an elastic foundation , 2012 .

[3]  Hisayo Doi,et al.  Fatigue Crack Initiation Life Prediction of Rails Using Theory of Critical Distance and Critical Plane Approach , 2012 .

[4]  Yanyao Jiang,et al.  A model for rolling contact failure , 1999 .

[5]  W. R. Tyfour,et al.  The steady state wear behaviour of pearlitic rail steel under dry rolling-sliding contact conditions , 1995 .

[6]  A. Kapoor A re-evaluation of the life to rupture of ductile metals by cyclic plastic strain , 1994 .

[7]  B. L. Josefson,et al.  Finite element analyses of rolling contact fatigue crack initiation in railheads , 2001 .

[8]  Jonas W. Ringsberg,et al.  Cyclic ratchetting and failure of a pearlitic rail steel , 2000 .

[9]  Makoto Akama,et al.  Development of Finite Element Model for Analysis of Rolling Contact Fatigue Cracks in Wheel/Rail Systems , 2007 .

[10]  W. Daniel,et al.  Early stages of rail squat formation and the role of a white etching layer , 2013 .

[11]  Z. Qian,et al.  Residual fatigue life evaluation of rail at squats seeds using 3D explicit finite element analysis , 2014 .

[12]  J. Beynon,et al.  Prediction of fatigue crack initiation for rolling contact fatigue , 2000 .

[13]  J. Chaboche Constitutive equations for cyclic plasticity and cyclic viscoplasticity , 1989 .

[14]  Xuesong Jin,et al.  Prediction of Crack Initiation of Rail Rolling Contact Fatigue , 2013 .

[15]  S. Bogdański,et al.  3D model of liquid entrapment mechanism for rolling contact fatigue cracks in rails , 2008 .

[16]  Francis Franklin,et al.  Modelling wear and crack initiation in rails , 2007 .

[17]  Jože Flašker,et al.  Numerical procedure for predicting the rolling contact fatigue crack initiation , 2003 .

[18]  C. Esveld,et al.  An investigation into the causes of squats—Correlation analysis and numerical modeling , 2008 .

[19]  Stanisław Bogdański,et al.  Numerical modelling of a 3D rail RCF 'squat'-type crack under operating load , 1998 .

[20]  Zili Li,et al.  The solution of frictional wheel–rail rolling contact with a 3D transient finite element model: Validation and error analysis , 2011 .

[21]  J. Chaboche,et al.  Mechanics of Solid Materials , 1990 .

[22]  Jun Wu,et al.  Substantial Fatigue Similarity of a New Small-Scale Test Rig to Actual Wheel-Rail System , 2014 .

[23]  Rolf Dollevoet,et al.  The vertical and the longitudinal dynamic responses of the vehicle–track system to squat-type short wavelength irregularity , 2013 .

[24]  Herbert S. Cheng,et al.  Micromechanics Modeling of Crack Initiation Under Contact Fatigue , 1994 .

[25]  W. Daniel,et al.  Metallurgical and physical understanding of rail squat initiation and propagation , 2012 .