冲击荷载作用下灰岩的能量耗散及损伤演化规律研究

Research on Energy Dissipation and Damage Evolution Law of Limestone under Impact Loads

利用改进后的直径50 mm的分离式Hopkinson压杆(SHPB)试验装置,对灰岩试件施加不同加载速率的冲击压缩试验,分析了试验中灰岩试件的能量耗散特征;通过基于Weibull分布的动态统计损伤理论并结合试验曲线分析了灰岩的损伤演化规律,并探讨了最大损伤变量与能量耗散密度的关系。研究结果表明:透射、吸收、反射能量受入射能量的影响显著,并且透射能的相关性最显著;能量耗散密度随应变率的增加而显著增加,呈现较好的线性正比关系,能量耗散密度为零时的临界应变率为62.56 s^-1;动态抗压强度与应变率呈指数函数关系;灰岩试件的能量吸收率随应变率的提高而显著减小。基于Weibull分布的动态损伤本构模型的计算曲线与试验曲线较为一致,损伤变量D随应变的增加而逐渐增加,在应力应变曲线峰值处,损伤变量D存在一个明显的拐点,损伤在此处开始急剧增大;灰岩的最大损伤变量Dmax与能量耗散密度呈较强的对数函数关系,存在Dmax为零时的临界能量耗散密度值。

The impact compression test of limestone specimens under different loading rates has been carried out by using the improved split Hopkinson pressure bar(SHPB)testing apparatus of 50 mm in diameter.Energy dissipation characteristics of limestone specimens in the experiments were analyzed.The laws of the damage of the limestone specimens were analyzed by using the dynamic statistics damage model based on the Weibull random distribution and the stress-strain curves,and the relationship between Dmax and SEA was explored.The results show that transmitted energy,absorbed energy and reflected energy are affected significantly by incident energy,and transmitted energy has the most significant correlation;SEA is significantly increased with the increase of strain rate,and there is a positive linear relation between SEA and strain rate,62.56 s^-1 is the critical strain rate when SEA is zero;The dynamic compressive strength and strain rate is exponential function relation;But the energy absorptivity of limestone is greatly reduced with the increase of strain rate.The model curves and the test curves have good consistency,the limestone damage degree increases with the increase of strain,at the peak of stress-strain curve,the damage degree has an inflection point,which means that rock damage rapidly increases in this time;There is a remarkable logarithmical relationship between Dmaxand SEA,and exists a critical SEA when Dmax is zero.