29th Annual Business Meeting and Conference on Tire Science and Technology

Doubletree Hotel Akron/Fairlawn: Akron, OH, USA

Monday, September 20, 2010: 4:10 PM
Aspen Ballroom (Doubletree Hotel Akron/Fairlawn)
Minwu Yao, Ph.D, Simulation Technology, The Goodyear Tire & Rubber Company, Akron, OH
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.