EXPERIMENT STUDY OF THE MAGNETIC MEMORY SIGNAL CHARACTERISTICS OF BUTT WELD UNDER FATIGUE LOADS USING GRADIENT INTEGRAL

Hu Ma,∗ Zhenfeng He,∗ Jianting Zhou,∗ Leng Liao,∗∗ Yang Zou,∗ and Yue Chen∗

Keywords

Steel structure, butt weld, fatigue, metal magnetic memory, non- destructive test

Abstract

Fatigue of steel structure possesses the characteristic of invisibility and destructiveness. Thus, the early detection of the fatigue failure of steel structure has become an interesting topic among scholars. To this end, the fatigue experiment of butt weld within steel structure was carried out in this paper, and the magnetic memory signal was collected simultaneously. Then the intrinsic characteristics of the magnetic memory signal corresponding to the respective fatigue stage of the weld were investigated using gradient integral. Illustrated results show that the lift-off height of the magnetic probe has an effect on the magnetic signal. The smaller the lift-off height is, the better the magnetic memory signal indicates the state of the weld. Moreover, the magnetic memory signal varies as the number of loading loops increases. Herein, the normal component of the magnetic memory signal can better characterize the damage in the fatigue stage. In addition, the introduction of gradient integral can clearly determine the moment of the fatigue crack sprouting, which provides a benchmark for early detection of fatigue damage in welded structures based on metal magnetic memory technique.

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