Mechanism of mechanical properties degradation of rubber isolation bearings at low temperatures

When exposed to low temperatures, the mechanical properties of rubber isolation bearings change significantly. However, the mechanism of the performance change has not been systematically investigated. This study aimed to investigate the performance degradation mechanism of isolation bearings at low temperatures. First, the relationship between the critical shear strain and initial strain of the strain-induced crystallization (SIC) of rubber materials in isolation bearings was discussed. Second, a uniaxial tensile test of rubber materials was performed at different temperatures ranging from-60 degrees C to 23 degrees C to investigate the effect of instantaneous thermal stiffening and SIC of the rubber materials. Subsequently, the degradation mechanism of the mechanical properties of the isolation bearings at low temperatures was analyzed by simultaneously considering instantaneous thermal stiffening, low-temperature crystallization, and SIC. Finally, compression and shear performance tests of the natural rubber bearings at different low temperatures were performed to verify the accuracy of the performance degradation mechanism of isolation bearings proposed in this study. This study found that the performance degradation of the isolation bearings at low temperatures may be the result of the combined effects of low temperature and strain. When the shear strain of a seismic isolation bearing exceeds the critical shear strain, stress hardening occurs rapidly because of the SIC of the rubber material. In addition, the critical shear strain varied depending on temperature. This study assists in understand how isolation bearings operate at low temperatures and provides a reference for the design and manufacture of seismic isolation bearings.