Research Of Finite Element Method To Microwave Imaging For Reinforced Concrete Structure

This article introduces the principle and characteristic of microwave nondestructive testing technology, also details the domestic and international developping status of nondestructive testing technology. It discusses the value and feasibility of this technology. Meanwhile, the article presents a series of basic theory about electromagnetic field and educes the rule of microwave spreading in concrete and reflects when it reaches to reinforced steel bar. It reaches the principle and specialty of electromagnetic field numerical analysis. Compare with each numerical method and elicit the extrude superiority of finite element method on electromagnetic field analysis.According to the basic idea of Finite element method, this thesis combines with microwave test on reinforced concrete structure and gives idiographic solving steps. First, building mathematical model of reinforce concrete and air layer outside; Second,meshing with tetrahedron element; Third, getting high frequency electromagnetic field functional equation from Helmholtz equation; Fourth, using functional and functional variation computation on each tetrahedron element, that is Element finite element analysis; Then, field normal equation is composed that based on all element crunodes number. Also, we apply boundary condition to solve and analyze dispose on microwave reflect problems. Meanwhile, design and implementation for upper procedure with MATLAB is mentioned. And we programed specialized software for this problem.We build variable specification reinforced concrete models and make simulation on 2.5GHz and 3.0GHz microwave frequency. By this way, electric field intensity-location relation image is received. It displays steel bar distributing situation in concrete intuitively. Compare with the simulation result of ANSYS, the curves superposition degree is satisfying with small error. The results indicate that the design is right. It is feasible and convenient to realize nondestructive testing for reinforced concrete structure by using Finite element method. Compare with electromagnetic field finite element software in common use, this software saves more resource of computer, reduce calculation time, improve test efficiency, and give reliable guarantee on contradictorily problem.