• • Service-induced damage reduces remaining useful life by up to 70.54% in as-welded (AW) regions and 22.31% in base metal (BM) regions, necessitating region-specific inspection intervals and retirement criteria for bogie frames.
• • Crack-tip strain response increases by more than 2× in AW and 1.44× in BM after service, directly correlating with reduced crack growth resistance and indicating accelerated damage accumulation under cyclic loading.
• • Phased array ultrasonic testing detected no macroscopic defects in post-service AW regions, yet microscopic analysis revealed secondary cracks, blurred fatigue striations, and unstable crack paths, exposing a critical gap in non-destructive evaluation sensitivity.
• • The integrated full-scale fatigue test and numerical simulation approach yields equivalent crack loading conditions that closely match actual service spectra, improving remaining useful life prediction accuracy by grounding experiments in engineering reality.