应力波作用下红砂岩复合动态断裂特征研究

Study on the dynamic fracture characteristics of red sandstone composite under stress waves

  • 摘要: 为探究应力波作用下红砂岩的复合动态断裂特性,采用分离式霍普金森压杆和数字图像技术对带预制裂缝的半圆盘三点弯曲试样开展冲击加载实验,分析加载率、波长对红砂岩动态拉伸、断裂特征的影响。结果表明:①红砂岩试样加载率与动态抗拉强度、断裂韧度及破坏率均呈一次函数关系;断裂能随加载率增大而增长415.27 %。②随着波长增加,动态抗拉强度增长742.14 %,其中断裂能增长54.49 %,但能量吸收率呈下降趋势;裂纹扩展平均速度增长4.09 %,且首尾裂纹应变增长时间出现滞后现象;破坏率增长效应得到强化。③冲击速度8 m/s时试件主裂纹首尾监测点位的应变平均增加84.31 %。

     

    Abstract: To investigate the composite dynamic fracture characteristics of red sandstone under the action of stress waves, the impact loading experiment was carried out by using separated Hopkinson press bar, digital image technology and on the three-point bending specimen of semicircular disc with prefabricated cracks, to analyse the effects of loading rate and wavelength on the dynamic tensile and fracture characteristics of red sandstone. The results show that: ①the loading rate of red sandstone specimens has a primary function relationship with the dynamic tensile strength, fracture toughness and damage rate; the fracture energy increases by 415.27 % with the increase of loading rate. ②With the increase of wavelength, the dynamic tensile strength increased by 742.14 %, of which the fracture energy increased by 54.49 %, but the energy absorption rate showed a decreasing trend; the average speed of crack expansion increased by 4.09 %, and there is a hysteresis phenomenon in the time of strain growth of the first and last cracks; the effect of growth of the damage rate was strengthened. ③The strain at the first and last monitoring points of the main crack of the specimen increased by 84.31 % on average when the impact velocity was 8m/s.

     

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