（1. School of Energy and Power Engineering, Beihang University, Beijing 100091, China) (2. School of Materials Science and Engineering, Beihang University, Beijing 100091, China) (3. Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing 100091, China)
In this paper, acoustic emission technique is used to monitor the fatigue crack growth behavior of crane box beam. Acoustic emission (AE) cumulative count/amplitude vs. cycle times, cumulative count/crack growth rate vs. stress intensity factor amplitude and AE signal spectrum characteristics of Q235B standard sample and crane box beam are compared. The results show that AE cumulative count/amplitude vs. cycle times curves of the box beam and the standard sample display similar characteristics. Spectrum analysis shows that although the corresponding peak frequency distribution range of the main signals generated in the second and third stages of AE cumulative count/amplitude vs. cycles times curve is not the same relatively, the types of main signals generated in the two stages (two kinds of signals in the second stage and one kind of signals in the third stage), the number of peaks of the corresponding spectrum (single peak and bimodal peaks in the second stage and multiple peaks in the third stage) and the change between the spectral peaks of the two stages (the number of spectral peaks in the third stage is more than that of the second stage) are consistent, which indicate that there are many similarities in the fatigue mechanism between them. Therefore, to a certain extent, the fatigue mechanism of crane box beam could be mapped through the fatigue mechanism of the standard sample, which provides guidance for the design and application of large workpieces.