Development Of Rebar Detector Based On Magnetic Measurement

In recent years,China's demand for infrastructure is increasing dramatically.It has always been a vital topic to guarantee the quality of building structures.As the most important building material,reinforced concrete is closely related to the safety of the whole project.The purpose of this project is to study the rebar detector principle and develop a low-cost detector device,which can provide scientific and accurate data for the inspection of reinforced concrete.This dissertation firstly completed analysis of requirements according to technical specifications.After that,two nondestructive testing methods based on magnetic measurement were introduced.The feasibility of detecting position,measuring the thickness of protective layer and inspecting diameter was discussed theoretically.The development of rebar detector includes hardware and software design.A mathematical model was built to study effects on the linear range and sensitivity of eddy current coils with different sizes.This dissertation also used 3D finite element analysis to study the defect of existing search heads,the influence of magnetic core and current frequency on detection performance.According to the conclusions obtained,a combined type search head was designed on the basis of existing coils.It was proved that this coil improved the remote detection performance and reduced weakness in short distance performance by simulation and analysis.Then this dissertation discussed the selection of key chips and described each module circuit amply.Sampling integral method was used in the signal conditioning part to improve the signal-to-noise ratio.Besides,the main programs of MCU were introduced.Fibonacci search algorithm was applied in the measurement program after comparing the table look-up algorithms commonly used.Analysis software on Windows was designed by Qt,whose functions including reading and writing serial port,data frame analysis,display and analysis of measurement results.In order to test functions of the rebar detector,this paper designed a test platform and scheme which conformed to the criterion after studying a number of national and industry standards.The experiment proved the detector could meet requirements for the position detection,the measurement of protective layer thickness and the diameter inspection of rebars.Analysis software realized all the functions required.