Plastic flow at the gauge corner of the low rail in heavy-haul sharp curves: Field investigation and formation mechanism

Abstract

Plastic flow is a common form of damage on the low rail of sharp curves in heavy-haul railways; however, its quantitative characterization, evolution, and formation mechanism remain to be systematically clarified. Based on long-term field measurements from an in-service sharp curve, a rail-profile-based geometric indicator was proposed to quantitatively characterize the magnitude and morphology of gauge corner plastic flow. Two models were subsequently established to reconstruct the plastic flow morphology using cumulative gross tonnage and vertical wear, respectively. Multibody dynamics simulations were conducted to evaluate the effects of gauge corner protrusions on wheel–rail contact and vehicle dynamic responses and to identify the dominant factors among those investigated. A refined finite-element model was further developed to examine the associated local elastoplastic mechanism. The results indicate that both the proposed plastic flow indicators and conventional wear indicators correlate strongly with cumulative gross tonnage. Plastic flow evolution is closely coupled with rail wear, and sections with more pronounced plastic flow exhibit higher vertical wear rates. The protrusion formed at the gauge corner reduces the effective contact area and raises the contact pressure, thereby increasing the derailment coefficient and the wheel unloading rate and adversely affecting running safety. Wheel profile variability was identified as the dominant factor among the parameters investigated. Finite-element analysis further demonstrates that under repeated wheel–rail loading, plastic deformation develops within and around the contact patch. In the main contact and wear band it is gradually removed by wear; in contrast, because wheel–rail contact rarely occurs at the gauge corner, residual deformation is retained and accumulated there, eventually developing into plastic flow. These findings provide a quantitative basis for optimising maintenance strategies, adjusting rail-grinding intervals, and preventing plastic-flow damage in heavy-haul curved tracks.