Fracture Toughness Test in Railway Wheels

The railway industry has been enhancing rail and train safety over the last few years, on a global scale. We have noticed that there are two well-defined trends: railroad car capacity increase in the freight sector and increased speeds in the passenger sector. Both increased freight capacity and higher speed imposes an overload on wheels. Early cracks and breaks, especially due to fatigue, are more likely to occur. The fracture toughness test, initially developed for the naval sector, has been used for several years in railway wheels, especially those of passenger cars, in order to analyze this material's behavior when there are cracks. The wheel manufacturing process had to undergo some adaptations in order to meet this test's requirements. This paper shows this process' evolution, in an effort to improve the fracture toughness test results, as well as a theoretical introduction of this test's conceptual aspects. The results obtained in forged wheels bound for several railroads (New York City Transit, New Jersey Transit) are shown herein, attesting, in practice, to the results obtained in theoretical studies. In its conclusion, the paper shows the manner in which the fracture toughness test results are being used to develop new railway wheel materials.