中文摘要：

动态拉伸载荷下,混凝土断裂强度随应变率的增加而提高。根据混凝土内部骨料与砂浆的力学性能,建立描述混凝土材料的细观有限元模型。通过ABAQUS二次开发单元UEL计算动载荷下垂直骨料砂浆界面裂纹的扩展,计算不同加载率下裂纹的扩展路径。计算结果表明,在低加载率下,裂纹沿着骨料与砂浆界面传播,在高加载率下,裂纹将穿过骨料,分析表明混凝土应变率效应的物理成因应为骨料断裂所致。

英文摘要：

Under dynamic tensile loadings, the fracture strength of concrete increases with the strain rate. The mesoscale FEM model of concrete is established according to the mortar and aggregate mechanical properties. Using ABAQUS UEL technique, the dynamic crack propagation path under different loading rates, which is normal to the interface of mortar and aggregate, can be calculated. The results show that, under the lower loading rates, the crack will deflect along the interface, while under the higher loading rates, the crack will grow straight through the interface. It can be seen from the results that the physical mechanism of strain rate effect in concrete is due to the fracture of aggregates.