冲击荷载作用下混凝土细观力学性能研究

发布时间：2018-10-09 15:42

【摘要】：混凝土作为一种率敏感性材料,在强冲击载荷作用下其材料特性会发生很大的变化。长期以来,混凝土动态力学性能研究多数是在宏观层面上开展的,即将混凝土视为一种各向同性的均质材料,且大多数研究都建立在试验基础上,试验成果多偏离原型。为了清楚的掌握混凝土在冲击荷载作用下的动态力学性能以及影响因素,本文从细观层面上,将混凝土视为骨料、砂浆以及二者之间的界面层组成的非均匀复合材料,采用随机骨料模型,借助富勒Fuller三维级配曲线计算出各个区间骨料的颗粒数,利用MATLAB编程语言结合蒙特卡罗方法实现了混凝土细观结构三维球形骨料模型的自动生成。运用有限元软件ANSYS/LS-DYNA对纯砂浆、仅有一个骨料(骨料含量为3.35%)的混凝土试件、以及骨料含量为24%的单级配、二级配混凝土试件进行应变率分别为10s-1、102s-1下的冲击荷载下的动力分析,最后,对不同应变率下相同骨料含量和不同骨料含量相同应变率下的冲击结果进行了对比。结果表明： (1)从细观层次上对各相材料赋予不同的本构模型是合适的。 (2)界面层是最薄弱、最需要加强的地方。 (3)在低应变率下,试件碎成数块,碎块较大；在高应变率下碎块多为小块。 (4)纯砂浆在不同应变率冲击荷载作用下表现出的率敏感性没有混凝土强烈。混凝土(骨料含量为24%)在应变率为100s-1的冲击荷载作用下的极限抗压强度比应变率为10s-1下的提高了80%,并且其应力应变曲线下降段很陡,表现出明显的脆性。 (5)混凝土(骨料含量为24%)峰值压应变随应变率的增加有所增加,单级配和二级配的峰值压应变分别提高了21.2%和12.5%。 (6)冲击荷载作用下,骨料含量相同时不同级配对力学性能的影响不大,且在高应变率下不同骨料含量对力学性能的影响较大。
[Abstract]:Concrete, as a rate sensitive material, will change greatly under strong impact load. For a long time, the research on the dynamic mechanical properties of concrete has been carried out on the macroscopic level, that is to say, the concrete is regarded as an isotropic homogeneous material, and most of the studies are based on the experiment, and the experimental results deviate from the prototype. In order to clearly understand the dynamic mechanical properties of concrete under impact load and the influencing factors, this paper regards concrete as a nonuniform composite material composed of aggregate, mortar and interfacial layer between them from the meso level. Based on the random aggregate model and Fuller three-dimensional gradation curve, the particle number of each interval aggregate is calculated, and the automatic generation of three-dimensional spherical aggregate model of concrete meso-structure is realized by using MATLAB programming language and Monte Carlo method. The finite element software ANSYS/LS-DYNA is used to analyze the dynamic behavior of concrete specimens with only one aggregate (3.35% aggregate content) and single gradation (24% aggregate content) under impact load with strain rate of 10s-1102s-1. Finally, the impact results of the same aggregate content and different aggregate content under the same strain rate were compared. The results show that: (1) it is appropriate to assign different constitutive models to different phase materials at the meso level. (2) the interface layer is the weakest and most in need of strengthening. (3) at low strain rate, the specimens are broken into several pieces, and the fragments are large, and the fragments are mostly small at high strain rate. (4) the rate sensitivity of pure mortar under different strain rate impact load is not as strong as that of concrete. The ultimate compressive strength of concrete (aggregate content is 24%) under impact load with strain rate of 100s-1 is 80% higher than that under strain rate (10s-1), and its stress-strain curve decreases steeply, showing obvious brittleness. (5) the peak compressive strain of concrete (aggregate content is 24%) increases with the increase of strain rate, and the peak compressive strain of single grade and secondary distribution increases by 21. 2% and 12. 5%, respectively. (6) under impact load, different gradation of aggregate has little effect on mechanical properties when the content of aggregate is the same, and different aggregate content has great effect on mechanical properties at high strain rate.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528.01

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