Stresses and strains in tyred wheels during tyre fitting process

Monobloc wheels are used today in almost all railway vehicles. Even if they give clear advantages for high-speed applications and where tread brakes are used, they are replacing tyred wheels also in urban and suburban trains. Lengthy and expensive maintenance procedures wheels are largely responsible for dismissing tyred wheel. The theoretical advantage of using infinite life wheel centres and axles heavily contrasts with increasing labour costs required by mainly manual overhaul operations on tyre wheels. As the authors are developing a strategy to revitalize tyred wheels in a large number of contexts, a design check of existing tyred wheels was compulsory. Unfortunately, no data were available from mainly manual calculations performed several decades ago. It was therefore necessary to do a sort of “reverse engineering” to understand how old existing tyred wheels work. A specific step in the assembly of a tyred wheel is the shrink fit of the tyre, which has diametrically opposite requirements from the structural point of view. The paper tries to draw some general conclusions that the designer of tyred wheels should properly take into account when approaching the design of a new wheel. The paper therefore shows the results of several simulations performed in order to analyse stressed and strains resulting from the tyre fitting process. A large number of parameters are evaluated to understand the behaviour of the current design of tyred wheels, with particular attention to the different shapes of the wheel centres. The ultimate aim of the research is to build a sound basis for a structural optimization of tyred wheels.