Research On Mechanical Properties And Dynamic Constitutive Of Foam Concrete

With the vigorous development of China's infrastructure construction,the use of various types of building materials has increased rapidly.In order to meet the needs of construction,new types of building materials with different functions have been developed and applied to actual projects.As a kind of special concrete,foam concrete is widely used in most projects for its excellent properties.In engineering practice,in addition to fire resistance and sound insulation,the mechanical properties of foamed concrete are particularly important.In addition to the existing research on its functionality and static mechanical properties,its dynamic mechanical properties are rarely involved,but its impact resistance applications are extremely extensive.Therefore,studying the dynamic mechanical properties of foamed concrete has important practical significance.Based on comprehensive consideration of its static and dynamic mechanical properties,this paper proposes an approximate dynamic constitutive model of foam concrete.This article mainly does the following work:(1)Use MTS universal testing machine system to perform quasi-static mechanical experiments on foam concrete and ordinary concrete,respectively.The static stress-strain relationship of the foamed concrete and its failure patterns are compared and analyzed.The process of crack initiation and development was analyzed from the experimental video records.At the same time,static experiments have obtained two kinds of concrete mechanical parameters such as elastic modulus and Poisson's ratio,which have laid a foundation for the establishment of foam concrete constitutive equation and the definition of mumerical simulation materials.(2)The ?50mm and ?75mm SHPB test systems were used to perform impact tests on foam concrete and ordinary concrete at different impact speeds,and the corresponding dynamic stress-strain curves and failure patterns were obtained Through the experimental results,the strain rate effect of foam concrete under impact was analyzed in detail,and the development process of internal failure and the manifestation of overall failure under different strain rates were explained.Both types of concrete are comparatively strain-sensitive materials.The dynamic stress growth factor(DIF)increases with the increase of the strain rate and maintains a good linear relationship with the increase of the strain rate.(3)Simplify the "Zhu-Wang-Tang" constitutive equation.When the physical meaning is clear,introduce the dimension E e so that the "Zhu-Wang-Tang" constitutive equation contains only E_e,A,?,?.With four parameters,an approximate equivalent constitutive model of the dynamic stress-strain relationship before the peak stress of the foam-dimensional concrete is established,and the specific parameter values of its constitutive equation are obtained by fitting the experimental data.The established dynamic constitutive equation has fewer parameters and is convenient for generalization.(4)The finite element software ANSYS?LS-DYNA was used to perform SHPB simulation on the foam concrete.In order to ensure the accuracy of the simulation and the experimental results,static and dynamic real experimental data were imported into the material model.The simulation results verify the accuracy of the dynamic experiments and provide a reliable basis for further experiments.