The Research On Mechanism Of Steel Structure Building Using Magnetic Memory Testing And The Method Of Magnetic Signal Acquisition-processing

In China, The development of the high-level-large-span structure is rapid in recentyears, its reliability has drawn people’s special attentions. Compared with theconventional nondestructive testing (NDT), Magnetic memory technology is a newNDT method that can detect the hidden damage in ferromagnetic members early andavoid members-tired damage abruptly. Firstly the article summarizes the art of state ofthe development of magnetic memory testing technology, focuses on and deepensanalysis the magnetic memory mechanism of hidden damage on steel structure from theview of an magnetic physics, mechanics of materials and so on, and provides thetheoretical basis for the application of magnetic memory testing technology in the fieldof steel structure building.Secondly, according to the principle of ferromagnetic, discusses the magneticproducing mechanism of steel members under the geomagnetic effect, studies theManicheanism of magnetic memory effect on steel structure under the effect of the jointaction of the magneto-elastic and the magnetostrictive, explains the reason of detectingthe hidden damage exactly to building using the magnetic memory technology testing.The research found that the essence of the mechanism detecting the hidden damage ofsteel structure building by magnetic memory is the result of joint action that magneticelasticity and magnetic mechanical effects, and the magnetic memory testing is one ofthe most available non-destructive testing methods which can diagnose hidden damageto steel structure building in early stage.Thirdly, tensile experiment of steel members of Q345-B without defects and threedifferent groups of artificial prefabricated defects has been carried out, obtains the law of the magnetic memory signals of a wide variety of specimens under different loading,and finds that the zero value of magnetic memory signals of members without defectshas drift phenomenon along with the change of loading, however, the zero value ofmagnetic memory signals members with artificial prefabricated defects has the identicalposition compared with defected members, uses the absolute value of magnetic fieldgradient K as the characteristic value which can determine the position of the hiddendamage more accurately. Based on the nonlinear fitting of the characteristic valueK maxon a variety of specimens, whichK maxis the maximum absolute value ofmagnetic field gradient,K maxcan be used to determine the elastic-plastic state ofmembers without defects and artificial prefabricated defects members.Finally, combining with the existing magnetic signal acquisition system, studies themagnetic signal acquisition method which can be used in steel structure building ofmagnetic memory testing instrument, improves magnetic signal acquisition system bymultichannel analog signals, obtains the magnetic signal acquisition system bymultichannel analog signals in a parallel way for steel structure building, the system canproviding method for the research and development which can be used to magneticmemory testing instrument of steel structure building. At the same time, this paper alsopoints out that the wavelet analysis method is more suitable for magnetic signalde-noising of steel structure building.