This research addresses modeling of material damping at the component level of tires for vibration simulations in the low to mid frequency range (0 to ~200 Hz) using finite element analysis (FEA).  Historically in these simulations, damping has been assumed or measured at the global level of the tire and therefore has provided limited usefulness for virtual design processes.  The proposed method introduces an implementation of the material loss moduli at the component level to complement existing material storage moduli and density implementations.  It therefore introduces the capability to predict tire damping and making it useful for design and tuning.  Testing and analysis techniques developed previously to measure and characterize material storage moduli at vibratory strains are revisited to include the material loss moduli.  The vibratory loss moduli are included into FE models used for vibration simulations in a manner parallel to existing vibratory storage moduli.  The technique is first validated on single elastomeric compounds with good correlation achieved between measured and predicted frequency response functions (FRF’s) of dual-lap shear specimen modal tests.  The technique is then applied to a full tire FE model with multiple compounds and validated with good correlation between measured and predicted FRF’s from the unloaded portion of the SAE-J2710 modal test.

Rubber is a very unique material. During processing and shaping, the uncured rubber behaves like a viscoelastic fluid. Proper analysis of rubber processing requires special material modeling and nonlinear finite element analysis tools that are quite different from those used for cured rubber. Key features of rubber flow behavior include: shear-rate dependence of the shear-thinning viscosity; presence of normal stresses in viscometric flows; and memory effects associated with the elasticity of the fluid. It has been known that modeling 3-D rubber flow with the traditional viscoelastic models remains to be a great challenge which requires excessive CPU time and memory.

An alternative to the traditional viscoelastic models is the simplified viscoelastic models which have emerged in recent years. To meet the challenge in modeling the die design for contoured rubber extrudates, a special material characterization procedure for a simplified ViscoElastic (VE) fluid model was developed based on the Capillary rheometer measurement data. The fitted simplified VE fluid model was then applied to 3-D rubber extrudate swell simulations. Without the elastic contribution, simulation results show significant unrealistic extrudate shrinkage. When rubber elasticity is incorporated, promising results of predicted extrudate swell were obtained with the simplified VE model. The parameter study results demonstrated that the amount of elastic swell can be easily and effectively controlled in the simplified VE model. Details of the material characterization process, benchmark tests of the simplified VE model and simulation results will be presented in this paper.

The 'Bend-over-Sheave' test has proven its relevance in the tire industry since the 1930's, especially on fatigue interply delamination and rubber-fabric & rubber-cord adhesion degradation. The typical cyclic load of tension of the sidewalls or tension- compression of the belt can be achieved by the proper definition of 2-ply laminates bended on a wheel with defined radius and traction force.

The new ecological challenges on rolling resistance, wet grip, noise & mileage life are driving the emergence of alternative rubber, filling and hybrid re-inforcement materials, for wich the overall fatigue behaviour should be tested in the early stage of new tire design.

Modern FEA methods like Abaqus are permitting to define the stress & strain within the tire sidewall & belt re-inforcing layers and to simulate crack initiation & propagation.

By using the same material properties and calculation methods, relevant fatigue test conditions can be defined to early predict the performance of the new materials.

The results obtained show the relevance for this test of the following points :

- non-linear properties of the re-inforcement cord
- the compression of the interply rubber
- interply shear deformation
- free length of the specimen
- clamping method
- specimen manufacturing quality

Also a simplified mathematical model is proposed for rapid estimation of the specimen test conditions.