Crack propagation in pneumatic tires: Continuum mechanics and fracture mechanics approaches

In this paper, the fatigue life of pneumatic tires is investigated with particular focus on the phenomenon of belt separation. This phenomenon yields the propagation of fatigue cracks in the rubber separating the belts; not the separation of the rubber at the interfaces with the belts. Cracks at the belts edges are related among others to the high stress concentration due to the very different stiffness of the two materials. A steady-state rolling finite element model of the full tire is used to evaluate the stress and strain fields in the rubber at the edges of the belts. Suitable life predictors are defined and computed for the identification of the zones with a higher expectation of failure. For the evaluation of crack propagation in the bulk rubber material between different belts, in principle, two different approaches are employed associated with crack nucleation and crack growth. The two approaches are applied to the study of crack propagation in a truck tire and the results of different predictors are compared to crack propagation found in a real tire.