Study On The Location Of Weld Defects In Steel Structures Under The Influence Of Eliminating Magnetic Interference

Butt welds are a typical form of weld in steel structures,and accurate detection of cracks and pores in their positions is of great significance for maintaining the steel structure.When using magnetic memory detection technology to locate welding cracks and pores,the traditional zero extreme value theory is difficult to distinguish between residual stress and magnetic signals generated by welding cracks and pores due to the influence of welding residual stress and various external random noise,Therefore,this article starts with the different mechanisms of magnetic signal generation in the regions where welding cracks,porosity defects,and residual stresses are located,taking into account various interference noises in the actual environment,and conducts research on the localization and detection of welding cracks and porosity defects in practical testing,which can cause misjudgment and omission of defect localization.The main manifestation is as follows: firstly,the mechanism of magnetic signals generated by welding residual stress and cracks and porosity defects is analyzed,and a threedimensional magnetic modulus gradient extreme value judgment method is proposed to distinguish residual stress from magnetic signals generated by cracks and porosity defects;Secondly,the finite element COMSOL simulation of welding defect is carried out,and the obtained magnetic signals are brought into the gradient extreme value characteristic formula for characterization and judgment;Once again,in order to verify the accuracy of simulation characterization judgment,manually make welded steel plates and extract three-dimensional magnetic signals for analysis;Finally,biorthogonal wavelet transform is introduced to eliminate random interference noise in the actual detection of threedimensional magnetic modulus gradient.The research results indicate that:1)The amount of magnetic charge accumulation per unit volume at welding cracks and porosity defects far exceeds the area where the residual stress is located,and the magnetic signal is spatially distributed,so this kind of magnetic signal in a single direction(such as normal or tangential)can not better characterize welding defect,but the threedimensional magnetic modulus gradient extreme value can more accurately express the spatial magnetic information.2)The results of COMSOL finite element simulation of welding defect and welding magnetic signal test show that the tangential component and normal component of magnetic memory are interfered by residual stress and external noise,and it is not obvious to distinguish welding cracks and porosity defects.However,the proposed threedimensional magnetic modulus gradient extreme value combines the three-dimensional magnetic signal component,which has good characterization characteristics for welding cracks and porosity defects,Therefore,the three-dimensional magnetic gradient modulus is used as the characteristic parameter to distinguish welding cracks and porosity defects.3)After comparing the denoising effects of multiple wavelets,it was found that the biorthogonal wavelet transform can effectively eliminate external magnetic interference,which can be used to reduce the impact of external magnetic interference on threedimensional magnetic modulus gradient detection and improve detection accuracy.