It is known from the split Hopkinson pressure bars experiments on dynamic uniaxial compression of brittle materials such as rocks and concrete that the strength increases with the increase of loading rate and the sample size. Friction and crack propagation do depend upon the loading rate, but this dependence would lead to the opposite effect – the strength decrease with the loading rate. Forrestal et al. (2007) showed that in dynamic loading the inertia effect induces additional, dynamic stresses. We demonstrate that (1) the circumferential component of the dynamic stress works to enable the failure mechanism based on extensive crack growth in uniaxial compression sufficient to cause splitting or spallation; (2) the radial component increases the strength by reducing the extent of wing crack growth such that higher load is required to induce failure. We propose a model of brittle dynamic failure which predicts the observed increase in dynamic compressive strength with the loading rate and sample size.

从岩石和混凝土等脆性材料的动态单轴压缩分裂霍普金森压杆实验可知，强度随着加载速率和样本尺寸的增加而增加。摩擦和裂纹扩展确实取决于加载速率，但这种依赖性会导致相反的效果——强度随加载速率降低。福雷斯特尔等人。(2007) 表明，在动态加载中，惯性效应会引起额外的动态应力。我们证明了 (1) 动态应力的圆周分量可以使基于单轴压缩中广泛裂纹扩展的失效机制成为可能，足以导致分裂或剥落；(2) 径向分量通过减少机翼裂纹扩展的程度来增加强度，从而需要更高的载荷来诱导失效。我们提出了一种脆性动态破坏模型，该模型可以预测所观察到的动态抗压强度随加载速率和样本大小的增加。