Fatigue analysis of random variable loads acting on wheels for special off-highway applications from experimental data

Wheels for off-highway applications are subjected, in service, to fatigue phenomena caused by cyclic loading of variable amplitude, which is often difficult to assess in the product design phase. Experimental field tests can help to understand their stress conditions in real use, particularly for special applications or load cases. In this work, a special load condition for an off-highway wheel is investigated. The wheel is mounted on an agricultural tractor and the stress state in its critical points recorded by strain gauges. Two configurations are considered: the standard one, as single rear wheel, and a particular configuration as internal wheel in a dual wheel assembly. The data acquisitions show a remarkable increase of the stress on the wheel disc in that specific configuration. Therefore, such load case can have a big impact on the fatigue life of the component and must be considered thoroughly, as the total number of working hours in this configuration in the lifetime of the vehicle is often unknown. Current industrial test standards, used for the durability validation of agricultural wheels, seem to be inappropriate for this specific application. Therefore, new specific test parameters should be defined, based on additional acquisition campaigns in real service conditions.