Keywords: operational safety, wheel web, fracture toughness, microcleanliness, rolling contact fatigue, standards.

Due to increases in axle load and the speed of railway freight wagons, wheels have evolved to meet growing braking demands under high levels of mechanical and thermal stress. The most serious failure mode that can occur in a railway wheel is fracture, which carries a high risk of causing derailment. In the 2020s, several critical failure events were observed in the web region of Association of American Railroads standard cast railway wheels, used by a heavy-haul railway operator in Brazil. These events resulted in significant material losses and prolonged interruptions to rail freight traffic. Laboratory test results from the last four failure events revealed the following detrimental factors: poor microcleanliness, surface or subsurface macroscopic flaws in the fracture region of the web, and low web toughness. This article presents technical analyses of a newly designed cast railway wheel, based on previous studies and investigations of wheels that failed in service in Brazil. Additional tests on the rim and especially on the web were conducted to assess the operational safety of this new wheel design. New quantitative requirements are proposed with the aim of improving the operational safety and reliability of railway wheels.

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