钢-PVA混杂纤维混凝土动态本构模型及其有限元分析

发布时间：2018-08-16 12:45

【摘要】：钢-PVA混杂纤维混凝土(Steel and PVA Hybrid Fiber Concrete,简称S-PHFC)可以阻止混凝土内部初始微裂纹的发展,控制宏观裂缝的开展速度,提高其强度、抗冲击性和抗裂性能、韧性等。在一些易受冲击、爆炸等动力荷载作用的工程领域,混杂纤维混凝土的力学性能发挥得更加显著,具有广阔的应用前景。由于钢纤维和PVA纤维在混凝土中乱向分布,因此S-PHFC是一种性能极为复杂的材料,对它的力学性能的研究至今尚未完善,其在动力荷载下的本构研究更少。本文首先对国内外关于混杂纤维混凝土的发展历程、本构研究和数值模拟现状进行简要的综述,阐述了六种常用的混凝土类材料的动态本构模型,并对每个本构模型作了详细分析。HJC模型是应用比较多且研究相对来说比较成熟的混凝土动态本构模型,但是原始的HJC本构模型并不适用含有一定体积分数的钢纤维和PVA纤维的混杂纤维混凝土,于是基于课题组钢-PVA混杂纤维混凝土冲击压缩实验,考虑纤维的增强作用和应变率效应,本文提出改进HJC动态本构模型,利用有限元软件LS-DYNA进行数值拟合,得到了以下成果:(1)阐述了钢纤维和PVA纤维对混杂纤维混凝土的增强、阻裂和增韧作用基本原理,考虑两种纤维的共同作用,结合SHPB实验数据,得出了不同纤维含量和不同应变率下的纤维增强因子、增韧增益指标和应变率增长因子公式。(2)钢-PVA混杂纤维混凝土同混凝土一样都具有应变率敏感性,且动态增强系数与对数应变率呈双折线关系。当对数应变率低于某个值时,动态增强系数DIF基本维持不变,但当对数应变率超过该阀值时,DIF随对数应变率增大而增大,并拟合出了此阶段的公式。(3)对钢-PVA混杂纤维混凝土的损伤因子进行了讨论,并拟合出计算损伤因子的方法。(4)考虑钢-PVA纤维的增强作用和应变率效应,提出了改进的HJC动态本构模型,为材料的数值模拟奠定基础。(5)实现了钢-PVA混杂纤维混凝土冲击响应的有限元数值模拟,模拟结果与实验结果吻合度高,说明数值模拟是可靠的,本文改进的HJC动态本构是适于本实验的。
[Abstract]:Steel-PVA hybrid fiber reinforced concrete (Steel and PVA Hybrid Fiber Concrete,) can prevent the development of initial micro-cracks in concrete, control the development speed of macroscopic cracks, improve its strength, impact resistance, crack resistance, toughness and so on. In some engineering fields where dynamic loads such as shock and explosion are applied, the mechanical properties of hybrid fiber reinforced concrete are more prominent and have a broad application prospect. Due to the random distribution of steel fiber and PVA fiber in concrete, S-PHFC is a kind of material with very complex properties. The study of its mechanical properties is not perfect, and the constitutive study of S-PHFC under dynamic load is even less. In this paper, the development history, constitutive research and numerical simulation of hybrid fiber reinforced concrete at home and abroad are summarized briefly, and the dynamic constitutive models of six kinds of common concrete materials are expounded. Each constitutive model is analyzed in detail. HJC model is a relatively mature dynamic constitutive model of concrete. However, the original HJC constitutive model is not suitable for hybrid fiber concrete with certain volume fraction of steel fiber and PVA fiber. Considering the reinforcing effect of fiber and strain rate effect, the improved HJC dynamic constitutive model is proposed in this paper. The numerical simulation results are obtained by using finite element software LS-DYNA. The following results are obtained: (1) the reinforcement of hybrid fiber concrete by steel fiber and PVA fiber is expounded. Based on the basic principle of anti-cracking and toughening, considering the joint action of the two fibers and combining with the experimental data of SHPB, the fiber reinforcement factors with different fiber contents and different strain rates are obtained. (2) Steel-PVA hybrid fiber reinforced concrete is as sensitive to strain rate as concrete, and the dynamic enhancement coefficient has a double linear relationship with logarithmic strain rate. When the logarithmic strain rate is lower than a certain value, the dynamic enhancement coefficient (DIF) remains basically unchanged, but when the logarithmic strain rate exceeds the threshold, the DIF increases with the increase of the logarithmic strain rate. The formula of this stage is fitted. (3) the damage factor of steel-PVA hybrid fiber concrete is discussed, and the method of calculating damage factor is fitted out. (4) the reinforcement and strain rate effect of steel PVA fiber are considered. An improved HJC dynamic constitutive model is proposed, which lays a foundation for the numerical simulation of the material. (5) the finite element numerical simulation of the impact response of steel PVA hybrid fiber reinforced concrete is realized. The simulation results are in good agreement with the experimental results, which shows that the numerical simulation is reliable. The improved HJC dynamic constitutive model is suitable for this experiment.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU528

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