An efficient 3D elastic-plastic finite element (FE) model was developed to simulate the evolution of contact mechanics under wheel-rail cyclic rolling contact and to predict rolling contact fatigue (RCF). A periodic crack nest derived from rail corrugation was selected as a representative case to investigate contact stresses and accumulated plastic strain on corrugated rails, with emphasis on the effects of corrugation geometric gradients. An incremental multiaxial fatigue-damage criterion was used to predict fatigue accumulation and crack initiation, followed by 3D oblique crack propagation simulation to elucidate corrugation-induced RCF formation. The FE results show that the maximum accumulated plastic strain shifts from the crest to the upslope, promoting localized ratchetting, accelerated fatigue damage, and dominant crack formation. Crack interaction and coalescence during cyclic rolling contact drive material shelling and crack nest development. These observations and simulations demonstrate the reliability of the developed FE model for predicting RCF.
The wave steepness enables the initial compression wave (ICW) to coalesce into a weak shock wave and induce a sonic boom. Field tests were conducted in five tunnels longer than 10.0 km. Results imply that amplitude of ICW is not sensitive to the spatial location. Distortion enables weak shock waves occuring when the distortion rate exceeds 1.0 and keeps increasing. The maximum pressure gradient approaches 198.25 kPa/s. Sonic boom happens inside the tunnel and can be detected outside the tunnel depending on its magnitude of A-weighted sound pressure level Lp- A. Within the tunnel, Lp-A of sonic booms first increases and then decreases, with the peak value reaches 102.4 dBA. Sonic booms are classified into four typical levels, i.e. critical value 60 dBA, slight booms within 60 similar to 70 dBA, clear booms within 70 similar to 90 dBA, and explosive bangs beyond 90 dBA. Loudness of the explosive bangs in present tunnels is less than 80 phon.
