Theoretical-Experimental Method for Determining the Short- and Long-Term Creep Parameters of Technical Rubber in Shear

A technique is developed for identifying the hereditary properties of technical rubber in short-term shear creep from the experimental shift the center of damped flexural vibrations of a vertically fixed three-layer test specimens of symmetrical structure with a technical rubber midlayer after their preliminary holding in a static bent state. This technique is based on the finite element method and integral equations of the hereditary viscoelasticity theory with the Koltunov–Rzhanitsyn heredity kernel. For identifying the rheological parameters of this kernel an objective function is constructed. To minimize the function, the direct zero-order search is used, which does not require the calculation of its gradient. The rheological parameters found are compared with experimental data of the long-term shear creep of the rubber. Noted is the unfoundedness of the direction, developed by some researchers, where only equations of the theory of hereditary viscoelasticity is used to model the vibration processes and the energy dissipation. The parameters of rubber creep kernel were identified in a long-term regime at a constant shear stress, and results showed that this type of testing is inapplicable to studying the short-term creep of rubber in shear.