EXPERIMENTAL STUDIES OF RATE-DEPENDENT MECHANICAL BEHAVIOR OF LAMINATED RUBBER BEARINGS

The paper is devoted towards an experimental investigation of the rate-dependent mechanical behavior of the laminated rubber bearings under horizontal shear deformation with a constant vertical compressive load. Three types of bearings are used in this study: natural rubber bearings (RBs), lead rubber bearings (LRBs) and high damping rubber bearings (HDRBs) with ISO standard geometry. The experimental scheme is comprised of three types of test at room temperature (23±1℃): cyclic shear (CS) test, multi-step relaxation (MSR) test, and simple relaxation (SR) test. The purpose of conducting the CS test is to identify the instantaneous behavior of the bearings; the SR test, to evaluate the viscosity induced rate-dependent behavior; and finally the MSR test, to obtain the equilibrium behavior. Moreover, a series of sinusoidal loading tests (at 0.5 Hz) are carried out at different temperatures ranging from 23℃ to -30℃. The objective of conducting the sinusoidal loading tests is to identify the basic mechanical characteristics of the bearings at different temperatures: the equivalent stiffness and damping of the bearings. The experimental results show that the viscosity induced rate-dependent behavior is more prominent in the HDR than the LRB and the RB. The viscosity induced rate-dependent behavior of the bearings is more significantly appeared in loading than in unloading. However, this typical behavior is not so significant in the RB as in the other two bearings. Furthermore, the temperature dependency of the equivalent stiffness is more remarkably emerged in the HDR and RB than the LRB, while that of the equivalent damping is more significant in the RB than the others