C75混凝土动态层裂强度试验研究

Experimental Study on Dynamic Spall Strength of C75 Concrete

基于线弹性力学理论和一维应力波的基本假定，采用大直径霍普金森杆对C75混凝土进行了一维杆层裂试验，以研究其动态拉伸强度和应变率效应．为了确定不同子弹速度下的混凝土弹性模量，在试件上采用了多点贴片的方法；通过优化子弹的尺寸，大大降低了应力波的波形弥散现象；提出了一种测定混凝土衰减系数的新方法，该方法能消除试件不均匀性、应变片个体差异以及信号衰减微弱等不良因素的影响，所获得的衰减系数比较精确．结果表明：C75混凝土动态拉伸强度具有较强的应变率相关性，在10^0～10^2S^-1应变率范围内，其层裂强度随着应变率的增大呈线性增长关系．

Based on the linear elastic theory and one-dimension stress wave assumptions, the spalling tests for C75 concrete bars were conducted by using a large-diameter φ74 mm Hopkinson bar to study its dynam- ic tensile strength and strain rate effect. Firstly, the multipoint gauge-mounting method was adopted to determine to dynamic elasticity modulus of concrete under different velocities of projectile. Secondly, the dispersion phenomenon of stress wave was greatly decreased via optimizing the projectile size. Finally, a new procedure for determining the coefficient of attenuation of concrete was further proposed, which could eliminate the influences of the nonuniformity of specimen, the differences of strain gauges and the attenuation weakness of signal. Experimental results show the dynamic tensile strength and strain rate are almost linearly correlated when strain rate ranges from 10^0 s^-1 to 10^2 s^-1.