Defect Locating of Typical Steel Structure Butt Weld Considering the Influence of Residual Stress
Butt weld is a typical weld form in steel structures,and the accurate detection of cracks and porosity defects at their locations are of great significance for the maintenance of steel structure.In the case of using magnetic memory testing technology to locate weld cracks and porosity defects,the traditional zero extreme value theory will be affected by welding residual stress,and it is difficult to distinguish residual stress and magnetic signals generated by welding cracks and porosity defects.Therefore,starting from the difference in the mechanism of magnetic signal generation in the area where welding cracks and porosity defects and residual stress are located,this paper presents a research on the location detection of welding cracks and porosity defects under the influence of residual stress.Firstly,the mechanism of magnetic signals generated by welding residual stress and cracks and porosity defects is analyzed,and the 3D magnetic modulus gradient extreme value judgment method is proposed to distinguish the magnetic signals generated by welding residual stress and cracks and porosity defects.Secondly,a finite element COMSOL simulation of welding defects is carried out,and the magnetic signals obtained are brought into the gradient extreme value characteristic formula for assessment.Finally,in order to verify the accuracy of the simulation characterization assessment,the welded steel plate is artificially made,and the three-dimensional magnetic signal is extracted for analysis.The research results show that the theoretical analysis,numerical simulation and experimental results are consistent.The extreme value of three-dimensional magnetic modulus gradient can locate welding defects and quantitatively characterize the length of defects,and the three-dimensional magnetic modulus gradient value of crack and pore type is far higher than the gradient value of defect free residual stress area.
weld crackporosity defectmetal magnetic memory testingCOMSOL simulationthree-dimensional magnetic modulus gradient