花岗岩冲击力学特性及损伤演化模型

Impact mechanical characteristics and damage evolution model of granite

使用分离式霍普金森压杆（SHPB）对花岗岩进行不同应力波波长（0.8~2.0 m）和不同应变率（20~120 s-1）组合下的冲击试验,对其动态力学特性和损伤演化规律进行了研究。试验得出：花岗岩的动态抗压强度与应变率呈线性正相关,动态抗压强度因子与应变率的自然对数呈线性正相关;峰值应变与应变率呈线性正相关,且波长的增加使峰值应变水平整体抬升。通过多次冲击试验得出：在同一波长下,花岗岩的累积损伤随着应变率的增长呈指数型递增形式;当保持应变率范围不变的情况下,增大应力波波长,花岗岩的损伤累积效应加剧,依然呈指数型递增形式;在多次冲击作用下,花岗岩损伤整体发展趋势相似,但增长速率加快;并由此建立以指数函数为基础的损伤演化模型,确定出模型中参数物理意义,该模型能够同时能反映应力波参数和冲击次数影响。通过验证表明模型的合理性及参数物理意义的正确性。

By using the split Hopkinson pressure bar（ SHPB）,the impact test at different stress wavelengths（ 0. 8-2. 0 m） and strain rates（ 20- 120 s- 1） was carried on to study the dynamic mechanical properties and damage accumulation evolution law of granite. Test results show that the dynamic compressive strength and strain rate of granite have significant correlation,whose relationship is linear positive correlation and the relationship between the factor of dynamic compressive strength and the natural logarithm of strain rate is linear positive correlation. The relationship between peak strain and strain rate is linear positive correlation,and the increase of wavelengths makes the level of peak strain uplift overall. The multiple-impacts test indicates that at the same wavelength,the cumulative damage of granite shows exponential increasing form with the increase of strain rate; when keeping the increase of strain rate constant and increasing the stress wavelength,the damage accumulation effect of granite is intensified and still shows exponential increasing form; under the effect of multiple impacts,the damage development trend of granite is similar overall,but the increasing rate is accelerating. Thereby the damage evolution model was established based on the exponential function,and the physical meaning of parameters in the model was determined. The model can reflect the effect of the wave parameters and multiple impacts. The validity of the model and the physical meaning of the parameters were verified bytest.