冻融循环与热老化交替作用下天然橡胶力学性能试验

Experimental study on the performance of natural rubber under alternation effects of freeze-thaw cycles and thermal aging

考虑北方地区暴露在空气中的建筑橡胶隔震支座冬季时段和夏季时段分别受到冻融循环和热老化作用,极有可能影响支座隔震效果的正常发挥。为此,开展了天然橡胶材料的冻融循环和热老化及其交替作用试验,研究了天然橡胶材料力学性能随时间及劣化深度的变化规律。结果表明:热老化作用是影响橡胶材料硬度、定伸应力的主要因素;在冻融循环和热老化作用下,拉伸强度和拉断伸长率呈现出随时间降低的趋势,且二者交替作用的影响并不是简单的叠加。冻融循环作用下,橡胶块在深度方向上硬度影响不大,但定伸应力在最外层区域内影响较大。在热老化作用、冻融循环-热老化交替作用下,橡胶块最外层20 mm的硬度、定伸应力影响较大。橡胶块在劣化深度方向上的拉伸强度和拉断伸长率的影响在表层20 mm最为明显。以上研究成果可为橡胶隔震支座性能劣化规律研究以及隔震结构全寿命性能评估提供依据。

Considering that the rubber isolation bearing of buildings,which is exposed to the air,will be respectively subjected to the freeze-thaw cycles and thermal aging in the wintertime period and the summertime period,the isolation effect of the bearing is very likely to be affected.To this end,the freeze-thaw cycle,thermal aging and alternation effects tests of natural rubber materials were carried out,and the mechanical properties of natural rubber materials with the changing of the time duration and the depth of deterioration were studied.The results show that:thermal aging is the main factor affecting the hardness and the stress at definite strain of rubber materials;the tensile strength and the elongation at break trend to decrease with time under the freeze-thaw cycles and thermal aging,and the influence of the alternating actions is not a simple superposition.The influence on the hardness in the depth direction of the rubber block is little,while that on the stress at definite strain is greater on the surface area of the rubber block under freeze-thaw cycles.The influences on the hardness and the stress at definite strain of the rubber block in the depth direction are rather greater in the 20 mm deep surface layer under thermal aging and alternation effects.The influence on the tensile strength and elongation at break of the rubber block in the depth direction are most obvious in the 20 mm deep surface layer.The results provide a basis for the study of the degradation of the rubber isolation bearing and the evaluation of the life cycle performance of the isolation projects.