Bending Test Of Steel Specimen Based On Magnetic Memory Method

In the field of building steel,the welding connection is an important connection method of structural components,but due to the complexity of the welding process,there are always some defects and stress concentration will be generated,which seriously reduce the reliability and service life of the structural components,therefore detecting these defects or hidden damage in advance is essential.As a new non-destructive testing technology,the metal magnetic memory technology utilizes the characteristics of the surface scattering field of the internal stress concentration area of the metal material under the action of the geomagnetic field.There are great potention detect the early damage of the material in the non-destructive testing application.It can not only detect the macroscopic defects that have existed,but also have a unique advantage for the regional detection of stress concentration or implicit damage,which makes it have a good prospect in the field of weld inspection.In this paper,by combining theory and experiment,on the three-point bending test of welded steel specimen based on wood was carried out,and EMS produced by Xiamen Edson Electronics Co.,Ltd.2003 type intelligent magnetic memory detector to obtain the defective surface of the leakage magnetic field normal component,In order to obtain pure signal wavelet packet method was employed to measure the magnetic signal(weak magnetic field)for noise reduction.the Analysis under different stress of magnetic memory signal changes was conducted to propose suitable for construction steel welded specimen test hidden damage method.The experimental results show that the magnetic wave signal intensity Hp(y)appears as a "peaks" or "troughs" phenomenon at the stress concentration,and decreases with the increase of the load,and then decreases after the plastic phase Large-scale law;magnetic memory signal gradient K in the stress concentration part of the "peak-peak" value changes and zero-crossing,and K value here changes the most intense;regional signal maximum and minimum value of the absolute value of the difference Hpp(y)is near the prefabricated defect.The curve of Hp(y)~F(or Hp(y)~ ?)is "inflection point" near plasticity zone.These laws show that it is effective and feasible to find the invisible damage of welded bending specimen by magnetic memory non-destructive testing method.