Abstract
Simulation of stress intensity factor as function of rolling contact fatigue cracks of railway tracks and the vehicle load is made with the help of COMSOL Multiphysics software. It is found that the critical stress intensity factor i.e. 41.6 MPa. m1/2 is reached at a stress level of 32 MPa and at the crack size 11.5 × 10-2 m.Noting the power law variation of acoustic emission count with increase in crack size (analogous to Paris Law), the simulation was further carried out to model the dependence of measured AE count with the stress intensity factor ahead of a growing RCF crack tip. It is demonstrated that AE measurement can be effective to trigger a control loop for avoidance of fatigue failure of railway track. In view of potential difference in the intensity of back scattered light from surface irregularities, a model is developed to find out the threshold intensity of scattered light that insures safety in the railway system against fatigue failure.
Highlights
In the present era of high speed, high axle load railway system, the derailment of trains is a major concern
Noting the power law variation of acoustic emission count with increase in crack size, the simulation was further carried out to model the dependence of measured AE count with the stress intensity factor ahead of a growing rolling contact fatigue (RCF) crack tip
Since Stress intensity factor is a function of the length of the crack, its critical value for unstable crack growth corresponds to a critical RCF crack size under the present condition
Summary
In the present era of high speed, high axle load railway system, the derailment of trains is a major concern. BANERJEE due to dynamic loading of a material is associated with the emission of elastic waves and that this is detectable by piezoelectric crystals [9] Since such acoustic emission (AE) is a function of crack growth parameter, the present work has further attempted to find out the AE count, commensurate with the threshold crack size for unstable crack growth; but AE count measurement at a point in the railway track has to be made with the probe placed in the near vicinity of the growing crack. Attempt is made to develop a model of crack detection by means of measurement of the intensity of light back scattered from the defects on tracks at remote locations; this entails the scope for evolution of suitable design formalism of a control system for derailment prevention
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