摘要
混凝土材料破坏过程中裂纹的演化具有随机无规律的特点,而外界条件的复杂性和混凝土自身的非线性使得裂纹的动态演化规律研究十分困难。为定量研究混凝土受力过程中裂纹及损伤的演变过程,本文在假定混凝土是由骨料、砂浆及两者之间的界面组成的三相复合材料基础上,建立了细观混凝土力学模型,提出一种基于裂纹分形维的损伤变量计算方法,对多组混凝土试件的单轴拉伸力学行为进行损伤数值研究,利用分形维对混凝土开裂全过程中的裂纹分布进行表征。研究表明:细观模拟的裂纹形态与试验结果相符;裂纹分形维能够更好地反映混凝土材料损伤的变化过程,可以定量描述材料损伤演化的特性;发现了混凝土从“均匀”损伤至局部破坏的临界点;细观模拟得到的应力-应变曲线、裂纹分形维曲线、损伤演化曲线受网格尺寸的影响很小;随着混凝土试件骨料级配数的增加,骨料颗粒和界面减少,整体耗能降低,应力峰值和裂纹分形维均减小。此外,本文建议应力峰值点后的裂纹分形维曲线的突变点为混凝土材料从“均匀”损伤进入局部破坏的临界点,是损伤和断裂的分界点,相应的损伤值约为0.8,该值可作为混凝土出现宏观裂纹的损伤阈值。本文研究加深了人们对混凝土破坏机理的认识。
The cracks evolution during the cracking process of concrete materials shows randomness.The concrete materials are nonlinearity of themselves and the external conditions are complex.These results in largely difficult study on the dynamic evolution law of concrete cracks.To quantitatively study the evolution process of cracks and damage of concrete under loading,the meso-concrete mechanics model is established assuming that the concrete is a three-phase composite composed of aggregates,mortar,and the transition zone between them.A new calculation method of damage variable is proposed based on the crack fractal di⁃mension,and the uniaxial tensile mechanical behavior of multiple groups of concrete specimens is studied in numerical simulation.The concrete damage crack distribution is characterized by fractal dimension.It shows that the results of meso-simulated crack pattern are consistent with the experimental results.The crack fractal dimension can better reflect the damage evolution process of concrete materials,and quantita⁃tively describe the damage evolution characteristics of concrete materials.It finds the critical point of con⁃crete materials from"uniform"damage to local failure.The stress-strain curve,the crack fractal dimension curve,and the damage evolution curve from meso-simulation results are all less affected by the element size.With the increase of aggregate gradation of concrete specimens,the aggregate particles and interface decrease,the overall energy consumption decreases,and the peak stress and crack fractal dimension de⁃crease.In addition,it is suggested that the mutation point of the crack fractal dimension-strain curve after the stress peak point is the critical point of the concrete materials from the"uniform"damage distribution stage to local failure stage,which is the boundary point of damage and fracture.The corresponding damage value is about 0.8,which can be used as the damage threshold for the occurrence of concrete macroscopic crack.These findings in this paper deepen the unde
作者
殷亚娟
任青文
沈雷
韩衍
YIN Yajuan;REN Qingwen;SHEN Lei;HAN Yan(College of Hydraulic Conservation and Hydropower Engineering,Hohai University,Nanjing 210098,China;Department of Engineering Mechanics,Hohai University,Nanjing 210098,China)
出处
《水利学报》
EI
CSCD
北大核心
2021年第11期1270-1280,共11页
Journal of Hydraulic Engineering
基金
国家自然科学基金项目(51739006)。
关键词
混凝土
细观
裂纹扩展
损伤演化
分形维
突变点
concrete
mesoscopic
crack propagation
damage evolution
fractal dimension
mutation point
