混凝土中心裂纹巴西圆盘试件的断裂行为研究

发布时间：2018-08-13 21:22

【摘要】：混凝土是一种主要起强度作用的多相复合材料,其用途之广,用量之大,在国民生活中发挥着不可替代的作用。尽管混凝土材料应用广泛,但我们对其的认识仍有不足,如含裂纹的混凝土地基、高楼建筑、桥梁、大坝、军用防护设施等的使用评估;可能遭受诸如强昼夜温差、强压、强风、撞击、爆炸、地震等载荷作用的混凝土建筑结构的评估。因此,研究混凝土的断裂失效对于工程的建设与维护具有非常重要的意义。应力强度因子(SIF)和T应力是断裂力学中的重要参量。本文详细介绍了如何利用权函数法、超确定有限元法和相互作用积分法来求解含裂纹构件的SIF与T应力。并着重描述了基于扩展有限元法(XFEM)的相互作用积分法,该方法更具一般性且计算精度非常高,可用于求解均质材料、功能梯度材料以及含夹杂界面的非均质材料在复杂工况的下裂纹尖端的SIF和T应力。此外,本文详细介绍了Ayatollahi等人修正的最大切向应力准则(MMTS准则),其中MMTS准则是既考虑了裂纹尖端应力场中的奇异应力项(即SIF),又考虑了非奇异应力项(即Williams级数中的T应力、A3和B3项)的最大切向应力准则。利用MTS、GMTS和MMTS三种准则对四种不同类型试件(砂浆试件,小颗粒骨料混凝土试件,大颗粒骨料低强度混凝土试件,大颗粒骨料高强度混凝土试件)、不同形式裂纹(纯I型,纯II型以及I-II复合型)的混凝土中心裂纹的巴西圆盘(CCBD)试件的裂纹起裂角和断裂阻力进行了实验和理论研究。并对MTS、GMTS和MMTS准则预测混凝土CCBD试件断裂行为进行了比较分析。研究结果表明,与传统MTS、GMTS准则相比,MMTS准则能够更好地预测混凝土CCBD试件裂纹起裂角和起裂韧性,特别是针对II型载荷占主导地位的情况。采用权函数法和相互作用积分法研究了围压对CCBD试件的裂纹尖端SIF和T应力的影响。结果显示,权函数法和相互作用积分法的精度都是非常的高,两者误差很小。围压对T应力和I型的SIF有重要影响,但对II型SIF无影响,大的围压将使裂纹趋于闭合。当裂纹长径比和加载角为一定值时,随着围压的增大,I型SIF逐渐减小,而T应力逐渐增大。纯II型裂纹对应的临界加载角的大小取决于围压的大小,围压越大,临界加载角越小,随着围压系数逐渐增大到1,临界加载角逐渐减小到0。
[Abstract]:Concrete is a kind of multiphase composite material, which plays an irreplaceable role in national life because of its wide application and large dosage. Although concrete materials are widely used, we still do not know enough about them, such as the assessment of the use of cracked concrete foundations, high-rise buildings, bridges, dams, military protective devices, etc., which may be subject to strong temperature difference between day and night, strong pressure, etc. Evaluation of concrete structures subjected to strong winds, impacts, explosions, earthquakes, etc. Therefore, it is very important to study the fracture failure of concrete for the construction and maintenance of engineering. Stress intensity factor (SIF) and T stress are important parameters in fracture mechanics. This paper introduces in detail how to solve the SIF and T stresses of cracked members by using the weight function method, the superdeterministic finite element method and the interaction integration method. The interaction integration method based on extended finite element method (XFEM) is described in detail. The method is more general and accurate, and can be used to solve homogeneous materials. The SIF and T stresses at the crack tip of functionally graded materials and heterogeneous materials with inclusion interfaces under complex working conditions. In addition, In this paper, the maximum tangential stress criterion (MMTS criterion) modified by Ayatollahi et al is introduced in detail, in which the MMTS criterion considers both the singular stress term in the stress field at the crack tip (that is, SIF), and the nonsingular stress term, that is, T in Williams series). Maximum tangential stress criterion for terms A _ 3 and B _ 3). Four different types of specimens (mortar specimen, small particle aggregate concrete specimen, large granular aggregate low strength concrete specimen, large particle aggregate high strength concrete specimen) and different types of crack (pure type I) were studied by using MTS GMTS and MMTS criteria. The crack initiation angle and fracture resistance of Brazilian disc (CCBD) specimen with center crack of pure mode II and I-II composite mode are investigated experimentally and theoretically. The fracture behavior of concrete CCBD specimens predicted by MTS- GMTS and MMTS criterion was compared and analyzed. The results show that compared with the conventional MTS- GMTS criterion, the MMTS criterion can better predict the crack initiation angle and fracture toughness of concrete CCBD specimens, especially in the case of mode II load dominating. The influence of confining pressure on SIF and T stress at crack tip of CCBD specimen was studied by weight function method and interaction integration method. The results show that the precision of the weight function method and the interaction integration method are very high, and the error between them is very small. Confining pressure has important influence on T stress and mode I SIF, but it has no effect on mode II SIF. Large confining pressure will make the crack close. When the ratio of length to diameter and the loading angle are certain, the mode I SIF decreases and the T stress increases with the increase of confining pressure. The critical loading angle of the pure mode II crack depends on the confining pressure. The larger the confining pressure is, the smaller the critical loading angle is. With the confining pressure coefficient increasing to 1, the critical loading angle decreases to 0.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O346.1

【相似文献】