Longitudinal creep force properties of wheel and rail under short-pitch corrugation state

Shallowness factor and wavelength ratio were induced to group sinusoidal short-pitch corrugations with simple harmonic waveforms and to analyze the properties of longitudinal wheel/rail creep forces for unsteady state rolling contact, the longitudinal creep forces due to sinusoidal short-pitch corrugations were calculated by Kalker 3D rolling contact theory, and the calculation result was compared with the calculation result from steady rolling contact theory. The system identification method of frequency response was used to fit the fluctuating part of unsteady longitudinal creep force. The relationship of fluctuating parts for unsteady state and steady state longitudinal creep forces was described as two order transfer function of wavelength ratio when sinusoidal short-pitch corrugations had same shallowness factor. The fluctuating part of unsteady longitudinal creep force was calculated according to the fluctuating part of steady longitudinal creep force, thereout, the unsteady longitudinal creep force was calculated. Calculation result shows that under small creep condition, the fluctuating part of unsteady longitudinal creep force decreases in amplitude and phase lag with the growth of wavelength ratio. The bigger wavelength ratio is, the smaller amplitude is, and the more phase lag is. However, the result from steady state theory is independent of wavelength ratio. For unsteady longitudinal creep forces calculated by the transfer function and Kalker 3D rolling contact theory, the waveforms in time domain, the amplitudes and phase spectrums in frequency domain are accordant.