Experimental investigation into the causes and mitigation measures of localised wheel tread defects of high-speed EMUs

Nearly the entire fleet of high-speed electric multiple units (EMUs) at a specific depot exhibited localised wheel tread defects (LWTDs), resulting in rapid progression of high-order wheel polygonisation and significantly shortened wheel re-profiling intervals. This incident marks the first documented occurrence of its kind in high-speed EMU operations across China in the past two decades. Comprehensive field investigations and experimental studies were conducted to identify the root causes of LWTDs and investigate the influence of operating speed on the formation of LWTDs. The main findings indicate that LWTDs originate from severe impact loads generated as wheels pass over damaged insulated rail joints (IRJs) and fixed frogs on a mixed-traffic railway line serving both passenger and freight trains. Although the speed limit was reduced to 60 km/h, this measure alone was insufficient to fully mitigate LWTDs without rail defect remediation. Based on long-term vehicle vibration tracking test data, two novel diagnostic indicators for IRJs and fixed frogs are proposed, utilising axle-box impact acceleration measurements to detect damaged rails. After remediation of the defective IRJs and fixed frog nose rails, LWTDs have been substantially mitigated, with high-order roughness levels of wheel out-of-roundness returning to normal operational levels.