FUNDAMENTAL APPROACH TO PREDICT TIRE AIR PRESSURE LOSS OVER TIME

Rubber material used in consumer products is vulcanized to improve its strength, viscoelasticity, and long and short-term durability. During the cure process, the morphology of the material evolves to form a highly crosslinked chain network, leading to a product that is less porous and less susceptible to air diffusivity. However, the formulation of the rubber compounds always create micropores or voids within them. Several laboratory tests are used to measure the material’s ability to resist the flow of air through it and to assess its porosity, especially under pressure. Residual-based integrated surface flux calculations are used to determine the evolution of air pressure as a function of time in an enclosed volume such as the cavity of an inflated tire. A finite element formulation was established for complex applications such as tires to predict the intracarcass pressure distribution. The capability of this simulation methodology was demonstrated for a tire with different inner liner compositions.