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研究岩石、混凝土类不均匀脆性材料动态强度提高的机制。对不同加载速率下特殊设计的三点弯曲梁的破坏形态进行理论分析,提出其动强度提高的根源主要是材料的不均匀性和惯性效应联合作用的结果,并认为此类材料的静、动强度与其破坏后裂纹的发展路径有关。静态加载时,裂纹沿着混凝土的最薄弱面发展,材料破坏所需的能量较小;动态加载时,裂纹能够穿过部分高强度区域沿着能量释放更快的路径发展,所需的能量也相应增大,材料不均匀性对动强度提高的贡献显现出来,惯性效应也随着加载速率提高而逐渐显著;当加载速率超过某一临界值时,由材料不均匀性贡献的动强度将不再增长,只有惯性效应的贡献发挥作用。通过特殊设计的不均匀脆性材料三点弯曲梁准静态加载试验和不同速率的冲击试验对提出的理论进行验证,试验结果与理论设想基本相符。
The mechanism of improving the dynamic strength of heterogeneous brittle materials in rock and concrete is studied. The theoretical analysis of the failure mode of a specially designed three-point bending beam under different loading rates shows that the root causes of the dynamic strength increase are mainly the result of the combined effect of material inhomogeneity and inertial effect. It is also believed that the static and dynamic behavior of such materials The strength is related to the development of crack after its failure. At static loading, the crack develops along the weakest surface of the concrete and the energy required to destroy the material is small. During dynamic loading, the crack can propagate through some high-intensity areas along a path of faster energy release and the energy required Correspondingly, the contribution of material inhomogeneity to the increase of dynamic strength appears, and the inertial effect becomes more and more obvious with the increase of loading rate. When the loading rate exceeds a certain critical value, the dynamic strength contributed by the material inhomogeneity will not Re-growth, only the contribution of inertial effect to play a role. The proposed theory is validated by the quasi-static loading test and the impact test with different velocities of the specially designed three-point bending beam with inhomogeneous brittle materials. The experimental results are in good agreement with the theoretical ones.