The Research In Relation To The Application Of Pulsed Eddy Current Nondustructive Testing Technology In Reinforced Concrete

In recently years,with the rapid development of China's construction industry,building bridges and other buildings collapse accidents have occurred frequently.Most of these accidents are caused by the location of the steel bars and changes in the thickness of the protective layer of reinforced concrete.To ensure the safe use of buildings,it is very important to detect the the position of the steel bar and the thickness of the protective layer.The traditional detection method is to drill holes in concrete,that is destructive testing,time-consuming and laborious.This paper chooses to use pulsed eddy current which is a new nondestructive testing technique to detect.Because of its excitation signal is a duty cycle and frequency are adjustable pulse square wave signal,rich in spectrum information,it has great advantages.In this paper,the design of the pulsed eddy current nondestructive testing system can be widely used in non-destructive testing of reinforced concrete,wall cables and plumbing pipes.The main work of this paper is as follows:(1)In-depth study of the basic principles of pulsed eddy current nondestructive testing,and this technique is applied to the detection of reinforced concrete.The COMSOL Multiphysics finite element simulation software is used to analyze the influence of the height of the lift on the surface of the tested specimen and the frequency of the excitation signal on the penetration depth of the eddy current.The simulation results show the effectiveness of the lift off effect of pulsed eddy current on the thickness detection of reinforced concrete protective layer.(2)A new algorithm which is based on the knowledge of electromagnetic induction magnetic reluctance is proposed for the relationship between the distance of separation and the impedance of the sensor coil.This algorithm can more intuitively express the relationship between them.(3)Use the STM32F407 with ARM Cortex-M4 core as the master chip,and the hardware and software of the pulse eddy current detection system for reinforced concrete are analyzed and designed in detail.For the data of ADC conversion,the median value filtering algorithm is used to improve the detection accuracy of the system.Using the STM32F407 minimum system to generate frequency and duty cycle are adjustable pulse square wave signal,this way than its 555 timer,more convenient.(4)To verify the performance of the system,use the design of the detection system for the actual detection,the experimental results for error analysis.The actual test results show that the test system designed in this paper can detect the thickness of the protective layer in a certain range,and basically realize the expected design goal.