An essential problem in the usage and maintenance of a wheel set with an automatic gauge change system is posed by the wear on the surface of wheel-axle rotary joint. Operational tests have shown that the problem includes fretting wear. This article presents an attempt at explaining this type of wear in a wheel-axle rotary set. The tests were performed on a joint model in which the similarity with the real object in the aspect of dimensions was maintained as well as the character and value of loading. In the description of the fretting wear mechanism in a rotary joint an analogy with wear in a wheel-axle press-fitted joint of a conventional wheel set was shown.
