Numerical Analysis Of MIH (Mechanical Impedance Method)for Estimation Of Concrete Compressive Strength

Concrete is one of the most common building material in the world. Due to the advantage such as economical and been shaped easily. It is widely used in water conservancy, transportation, industrial, civil buildings and other huge national basic infrastructure, even in the national defense construction. In recent years, with the rapid development of civil engineering, the structure type become more and more complex, and also the security performance of civil engineering become more and more high. However, due to construction management or environmental factors, the defects are formed in different forms in the concrete structure, the presence of which can produce different influence on structure’s integrity, mechanical properties and durability. Therefore, it is necessary to use the nondestructive testing method to detect the strength of concrete without damaging the structure.This paper is based on the projects of percussion method of nondestructive testing technology research, the object is precast concrete and engineering components. Using theoretical analysis, data processing, model building, comparative analysis to elaborate the rebound method’s limitation which based on hardness measurement and discusses the method of deducing compressive strength by testing the mechanical impedance which is obtained by knocking the surface of the concrete in this article, and also using a sensitivity analysis on the influence of different initial velocity, the mesh density and the thickness of the concrete blocksThis paper compares the force, the differences before the time and after, the change of the acceleration of hammer between the ideal elastomer and elastomer with defects in the process of hammer knock collision by using the ABAQUS finite element software, and makes the comparative analysis of the different percussion initial speeds and density of mesh between the concrete block and the reinforced concrete block. Results show that for an ideal elastomer, percussion force waveform is symmetrical, and the action and reaction time is same; For defect elastomer, percussion force waveform is asymmetric, and the action time is greater than the reaction time,Namely in the process of knocking, part of hammer knock kinetic energy is absorbed by plastic deformation of the elastomer, while the energy of the reaction is completely transformed by elastic deformation which can be used to express the compressive strength. In addition,because of the mechanical impedance velocity dependence,the change of the initial velocity and the knocking time has little impact on the determination of the mechanical impedance after it import into the function of correspondence correction. So we can draw the conclusion that measuring the compressive strength through testing mechanical impedance of concrete is scientific and applicative.