The Effect of High-low Temperature Cycle Ageing on Mechanical Properties of Silicone Rubber under Tensile State

High-speed locomotives will pass through different climatic zones when crossing long-distance lines, which will make locomotive electrical equipment face the test of high and low temperature cycle changes. The locomotive cable terminal is in an expanded state due to interference fit, resulting in the terminal insulation material in the thermal-mechanical combined field. This paper aims to explore the effect of high-low temperature cycle aging on the mechanical properties of silicone rubber under tensile state for cable terminals. Specifically, a combined aging test of high-low temperature cycle (from -40°C to 90°C) and mechanical stress was designed and conducted, and the effect of combined aging on the mechanical property and molecular chain structure of silicone rubber insulation under different aging time was compared and analyzed. The results showed that, as the aging time increases, the tensile strength and elongation at break of the silicone rubber gradually decrease. The infrared spectroscopy test results show that the main chain of the silicone rubber is obviously destroyed after combined aging, and the crosslinking density test results show that the crosslinking density of the silicone rubber after aging decreases, which is consistent with the infrared results. The mechanical stress field will aggravate the damage effect of the high-low temperature cycle field on the mechanical properties of the rubber material. In the tensile state, the curled silicone rubber molecules are forced along the tensile direction, and it is easier to break under the effect of the high-low temperature cycle. The research results are expected to be used in the selection and structural design of rubber insulation for locomotive terminals.