Affiliations: [a] School of Civil Engineering, Xi’an University of Architecture and Technology, Xi’an, Shaanxi, China | [b] School of Civil Engineering, Shaanxi Polytechnic Institute, Xianyang, Shaanxi, China
Correspondence:
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Corresponding authors: Sanqing Su, School of Civil Engineering, Xi'an University of Architecture and Technology, Yanta Road 13th, Beilin District, Xi'an City 710055, Shaanxi Province, China. Tel.: +86 139 0926 2233; E-mail: sussqx@xauat.edu.cn. Huan Guo, School of Civil Engineering, Xi'an University of Architecture and Technology, Yanta Road 13th, Beilin District, Xi'an City 710055, Shaanxi Province, China; and School of Civil Engineering, Shaanxi Polytechnic Institute, Wenhui Road 12th, Weicheng District, Xianyang City 712000, Shaanxi Province, China. Tel.: +86 180 8227 1661; E-mail: guohuan86@outlook.com
Abstract: Metal magnetic memory (MMM) testing is a nondestructive approach for evaluating the stress concentration and early damage of ferromagnetic components. However, research on the MMM testing of large steel structures has been limited. Thus, this study investigates the suitability of MMM technology for monitoring the damage in steel structures exposed to complex stresses. The normal components of magnetic signals Hp(y) on the beams and columns of a portal frame are obtained through pseudo-static testing. The signal increment ΔHp(y) and its absolute value |ΔHp(y)| under different loads are analyzed. The relationship between the equivalent stress and magnetic signal is investigated through numerical simulation. The results show that the ΔHp(y) curves are similar during the elastic stage but change abruptly during the plastic phase. Moreover, the differences in the magnetic signal directions caused by the varying detection directions cannot be ignored. In the elastic stage, with the increase in the load, |ΔHp(y)| curves initially increase and then decrease. The formation of the ΔHp(y) curve is similar to the distribution of the equivalent stress. The mutation of ΔHp(y) can determine whether a specimen is entering the plastic phase, and can warn against structural failure. The magnetic signal distribution qualitatively reflects the stress distribution.
Keywords: Metal magnetic memory testing, monitoring damage, normal magnetic signals, pseudo-static test, portal frame, equivalent stress
