Research On Defection Of Steel Strcuture Based On Electromagneti Acoustic

Steel structure has become the indispensable raw materials of all walks of life.The quality of the product will directly affect the performance and quality of the product.However,it is inevitable that there will be cracks,holes,corrosion and various defects in the welding process.The strength and the stability of the structure can be declined sharply by the existence of these defects in performance.So it is critical to detect such defects.The main research content is as follows:1.The finite element electromagnetic ultrasonic surface wave steel structure model was established by COMSOL software.The relationship between the Lorenz force and the magnetostrictive force in the steel structure is analyzed and compared.Also the effects of magnetic field intensity,excitation current amplitude,excitation current frequency and excitation current period on the amplitude of the surface wave are studied,The depth and the buried depth characteristics of the crack defects were analyzed and studied.2.The Lamb wave and SH guided wave in steel plate are simulated and analyzed.A 2D simulation model of electromagnetic ultrasonic Lamb wave was established.The change trends of Lamb wave transmission coefficient and reflection coefficient of different incident wave and different defect types and the mode conversion characteristics of Lamb wave are analyzed.Characteristics of SH wave propagation in the detection of weld defects and cracks were analyzed,The no dispersive and no mode conversion characteristics of SH guided waves in the defect detection are further explained,which provides theoretical basis for the detection of defects.3.Several common defects in the steel structure were detected by the electromagnetic ultrasonic inspection system.The feasibility of detecting the surface and near surface defects of the steel structure by electromagnetic ultrasonic surface wave is verified and the mode conversion characteristics of Lamb in the defect detection of steel structure sheet and the no mode conversion characteristics of SH wave in the detection of weld defects in steel structure.