Research On Internal Reinforcement Damage Detection Of RC Beam Based On Magnetic Memory Effect

At present,the detection of steel bars in concrete Bridges worldwide will generally damage the concrete protective layer and affect the overall structure of the bridge.Therefore,this paper is devoted to the nondestructive detection of the bridge.Magnetic memory detection is applied in the field of bridge engineering.Based on the theory of electromagnetic field and geomagnetic field,the magnetic field distribution of steel bars in reinforced concrete specimens under different damage conditions is studied by means of experimental research and numerical simulation.The main research contents of this paper are as follows:1.Conduct experimental research and test the distribution of leakage magnetic field of the specimen under different load conditions.According to the analysis of the experimental data,it can be seen that in the elastic deformation stage of internal steel reinforcement,the magnetic memory signal does not change significantly.When the internal steel reinforcement is deformed plastically,the measured normal component Hp(y)crosses the zero point,and the signal peak value appears at the maximum bending point of the steel reinforcement,and the value of the signal peak value will increase with the increase of the load,which proves that the magnitude of the load in the plastic deformation stage determines the distribution of the normal component on the steel reinforcement.2.Detect the distribution of magnetic leakage field of reinforcement under different corrosion rates.Experimental results show that magnetic memory testing under different corrosion degree of leakage magnetic field distribution on reinforcement are there is a certain rule,when the flaws of the reinforcement length,depth,different phase at the same time,found that magnetic memory testing of the tangential component of the size and the defect length values,and the numerical method to the component measured also in close proximity to an defect length values,internal steel specimen defects can pass data to determine the condition of the leakage magnetic field.It can be inferred that nondestructive magnetic memory can be applied to the early detection of Bridges.3.Finite element simulation of reinforced concrete beam with COMSOL software.The magnetic mechanism of ferromagnetic components under geomagneticeffect was verified by combining magnetic elasticity and magnetic mechanical effect.By analyzing the external magnetic field of rebar with different diameters,it was found that the external magnetic field of rebar with a diameter of 12 mm was larger than that of 8mm.Secondly,the distribution of the external magnetic field of reinforcement under different loads is analyzed,and the distribution diagram of the external magnetic field of reinforcement is extracted,and the change curves of normal component and tangential component with loads are drawn.The results show that the normal component of the leakage magnetic field crosses the zero point and the tangential component reaches the peak value,which indicates that plastic deformation of the steel bar and irreversible rearrangement of the internal magnetic domain occur.The numerical simulation well explains the feasibility of magnetic memory detection of steel reinforcement damage,and thus proves the applicability of magnetic coupling and the model.The research shows that the magnetic memory detection technology can detect the damage of the internal steel bar early on the basis of not damaging the bridge,and inspectors can easily analyze and judge the work of the detection components.Therefore,the nondestructive testing method in this paper is effective,easy to operate,the results are real and reliable,and has a good market application prospect.