Abstract
During manufacturing, tires are naturally cooled to room temperature after release from their molds. The manner in which the post‐cure cooling process is performed can greatly influence a tires overall performance. As an effective procedure, post‐cure inflation (PCI) had been commonly used during the post‐cure cooling process to control dimensions and shapes of tires. However, since the introduction of dimensionally stable polyester as tire carcass cord material, PCI has been considered an unnecessary step and has been eliminated from some tire manufacturer's lines. By convention, tires manufactured with PCI are designated as PCI tires whereas tires manufactured without PCI are designated as no‐PCI tires. As a result of the different loading histories experienced during the post‐cure cooling process, PCI and no‐PCI tires exhibit different behavioral aspects including dimensions and footprint shape. More specifically, when the same mold is used, the most prominent difference between PCI and no‐PCI tires is the profile. No‐PCI tires have smaller section widths and inflated crown radii than PCI tires due to the thermal shrinkage occurring in the cords during the post‐cure cooling process. On the other hand, no‐PCI tires exhibit more dimensional change than PCI tires when subjected to exercise. In this study, experimental passenger tires (235/75/R15) with and without PCI are built using the same curing mold, and a series of tests are conducted to establish the differences between these two kinds of tires. Meanwhile, material characterizations of the polyester tire cords used in the tire construction are conducted with various thermal‐mechanical loading histories, and the influences of the post‐cure cooling process on the cord properties are determined. Then an axisymmetric and a three‐dimensional finite element model are constructed and the post‐cure cooling processes with and without PCI are simulated. With the input of the cord material properties obtained through the material characterization, the numerical analyses successfully predict the tire dimensions, profile, and footprints for both PCI and no‐PCI tires. The analytical results obtained are in agreement with the experimental measurements obtained from the experimental tires.
