A Full Information Expression Model for Track Irregularity Based on Stochastic Harmonic Functions in Vehicle–Turnout Structure Stochastic Vibration Analysis

• • Hamming window with 4096-point length yields optimal turnout irregularity PSD estimation; a fifth-order polynomial fits the PSD with minimal error, providing a standardized spectral basis for turnout-specific condition monitoring rather than relying on generic track spectra. • • TIFIEM sample size of 250 irregularity realizations minimizes RMSE against the target spectrum; PSD amplitudes at each frequency point follow a Chi-square distribution with 2 degrees of freedom, enabling probabilistic reliability assessment without exhaustive Monte Carlo sampling. • • At 300 km/h on a No. 18 turnout, the straight switch rail 3–7 m from the switch rail tip and the point rail 53–54 m from the tip are the most wear-prone zones, directing inspection resources to specific longitudinal positions where degradation accelerates. • • Vehicle–turnout structural reliability at the crossing panel drops to 95.8% at 300 km/h, quantifying the safety margin erosion under high-speed operation and justifying prioritized maintenance at the crossing panel.