A Method to Combine a Tire Model with a Flexible Rim Model in a Hybrid MBS/FEM Simulation Setup 2011-01-0186

During the last ten years, there is a significant tendency in automotive design to use lower aspect ratio tires and meanwhile also more and more run-flat tires. In appropriate publications, the influences of these tire types on the dynamic loads - transferred from the road passing wheel center into the car - have been investigated pretty well, including comparative wheel force transducer measurements as well as simulation results. It could be shown that the fatigue input into the vehicle tends to increase when using low aspect ratio tires and particularly when using run-flat tires.

But which influences do we get for the loading and fatigue behavior of the respective rims? While the influences on the vehicle are relatively easy to detect by using wheel force transducers, the local forces acting on the rim flange (when for example passing a high obstacle) are much more difficult to detect (in measurement as well as in simulation). This paper is dealing with a method to detect local rim forces for very severe events (like curb strikes), in which the tire belt can have contact with the rim. One key issue of the overall method is a special tire model which can handle the respective large tire deformations up to belt/rim contact and which can predict local rim forces on the rim flanges in a suitable way. The second key issue is a method to combine the tire model with a model of a flexible rim (which is embedded in a full vehicle MBS model).

This method can be used to perform virtual load prediction of local rim forces, which are the basis for a CAE based fatigue life prediction of rims, especially for misuse-like events. On the other hand, by using nonlinear FEM models of the rim including plasticity effects, this method is the basis for misuse simulations in a combined MBS/FEM simulation setup where the rim and its affected suspension parts are modeled in FEM and the whole complementary vehicle is modeled in MBS.