冲击荷载作用下热处理花岗岩动态力学特性研究

Research on Dynamic Mechanical Properties of Heat-treated Granite Under Impact Loading

为研究冲击速度和热处理温度对黑云母花岗岩动态力学特性的影响,利用改进的霍普金森压杆系统对25~800℃共9个温度等级的热处理试样分别进行3种弹速下的冲击压缩试验。试验结果表明:随着冲击速度的增加,25~700℃热处理试样的应力—应变曲线由“Ⅱ型”转变为“Ⅰ型”,而800℃热处理试样均表现出“Ⅰ型”应力—应变曲线特征。同一温度热处理下试块的峰值应力、应变和平均应变均随动荷载的升高而增大。相同的冲击速度下,300℃热处理试样的动力学性能有所改善,500℃后试样的动力学性能开始逐渐劣化。同一温度热处理试样的破碎程度随冲击速度的增加而增加;相同冲击速度下,热处理试样的破碎程度随温度的升高先减弱后增强。

In order to study the influence of impact velocity and heat treatment temperature on the dynamic mechanical properties of biotite granite,the improved Hopkinson Pressure Bar system was used to conduct impact compression tests on the heat-treated granite at 25~800℃under three impact velocities.The experiment results show that with the impact velocity increasing,the stress-strain curves of the heat-treated samples at 25~700℃change from“typeⅡ”to“typeⅠ”.But the heat-treated samples at 800℃all show the“typeⅠ”stressstrain curve.The peak stress,average strain and peak strain of the sample at the same temperature increase with the impact velocity increasing,showing obvious loading rate effect.The elastic modulus does not change much with the impact velocity,and the loading rate effect is not obvious.Under the same impact velocity,the dynamic properties of the heat-treated samples at 300℃are improved.After 500℃,the dynamic properties of the samples begin to gradually deteriorate,and the heat-treated samples at 800℃have the weakest dynamic properties.The relationship between peak stress,average strain rate,peak strain and elastic modulus and heat treatment temperature can be expressed by single exponential function.Under the same treatment temperature,the damage degree of granite increases with the increase of impact velocity.Under the same impact velocity,the fragmentation degree of the heat-treated sample at 300℃is the smallest,and the heat-treated sample at 800℃is the most serious.From the field emission scanning electron microscope image,it can be seen that the fundamental reason for the change of rock macro mechanical properties is that the temperature changes the microstructure inside the rock.