Numerical simulation of near surface rail cracks subject to thermal contact stress

• The effect of surface temperature on sub-surface crack growth in a rail is examined.
• Temperatures of 1000 °C, 500 °C and 20 °C were modelled, covering wheel spin conditions.
• Thermal input can ‘unlock’ crack growth in a similar way to fluid entry into cracks.
• Contact temperature can be significant in the behaviour of rail defects.

Boundary element modelling was conducted to investigate rail cracks subject to combined thermal and contact loading such as occurs in ‘stud’ or ‘squat type’ defects in which white etching layer lies above shallow cracks formed without evidence of plastic flow. An embedded crack at 0.5 mm below the rail surface was modelled, revealing a thermal mechanism of crack opening. Stress intensity values for a range of contact temperatures were calculated.