摘要
高温真三轴试验机研制过程中,高温环境、循环加卸载和循环热冲击等复杂加载条件对试验系统隔热性能提出了严苛要求.为了科学合理地选择复杂条件下高温真三轴试验机的隔热材料,制备了3种高温工程隔热材料,分别是高聚热能酰胺脂隔热材料(GX)、玻璃纤维与耐高温树脂复合隔热材料(BX)和高温阻隔复合云母材料(YM),并开展考虑实际仪器设备工况下的循环热冲击、高温环境和循环加卸载等室内试验.结果表明:在高温环境影响下3种隔热材料的导热系数均随温度的升高呈现先升高后降低的趋势,弹性模量出现了一定幅度的下降;随着循环加热冷却次数的增加,YM材料的导热系数数值平稳下降,BX和GX材料的导热系数呈现先升高后降低的变化趋势,弹性模量变化规律与高温环境影响下相似;隔热材料的导热系数均随着循环加卸载次数的增加呈现先升高后降低的变化趋势,其中初次加卸载对材料隔热性能和物理性能的影响最大;综合热—力学性能评判,YM材料性能最稳定,为岩石真三轴试验机隔热材料的最优选.
Abstract
During the development of high-temperature true triaxial testing,the imposition of high-temperature environments,cyclic loading and unloading,cyclic thermal shocks,and other complex loading conditions necessitates stringent requirements for the thermal insulation performance of the test system.In oder to scientifically and rationally select appropriate thermal insulation materials for the high-temperature true triaxial test machines under such complex conditions,three kinds of high-temperature engineering thermal insulation materials(GX),glass fiber,and high-temperature resistant resin composite thermal insulation material(BX)and high temperature barrier composite mica material(YM)were prepared.A series of laboratory tests,including cyclic thermal shock,high-temperature exposure,and cyclic loading and unloading,were conducted to simulate the mechanical and thermal conditions representative of operational environments.These tests aimed to evaluate the thermal conductivity,elastic modulus,compressive strength,and microstructural evolution characteristics of the materials under complex working conditions.The results indicate that the thermal conductivity of the three insulation materials initially increases and subsequently decreases with rising temperature under high-temperature conditions,while the elastic modulus exhibits a certain degree of reduction.During cyclic thermal shock experiments,the thermal conductivity of the YM material demonstrated a consistent decline with an increasing number of heating and cooling cycles.In contrast,the thermal conductivity values of the other two materials initially increased and then decreased.The variation in the elastic modulus exhibited a pattern analogous to that observed under high-temperature conditions.Under cyclic loading and unloading conditions,the thermal conductivity of the insulation material initially increases and subsequently decreases as the number of cycles progresses.Notably,the first cycle of loading and unloading exerts the most significant influence on the thermal insulation and physical properties of the material.Scanning Electron Microscopy(SEM)results indicate that the pores within the laminated structure of the YM material remained small following thermal shock,with no significant crack formation observed after high-temperature treatment.The structure was both complete and stable.A comprehensive evaluation of the thermo-mechanical properties revealed that,after exposure to high-temperature environments and cyclic thermal shock,the structural integrity of the YM material was exceptionally stable.Consequently,YM material is deemed the optimal choice for insulation in rock true triaxial testing machines.This study establishes a foundational framework for the selection of thermal insulation materials in true triaxial test equipment and offers significant guidance for both the research and application of thermal insulation material sheets in true triaxial test machines.
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