Study On Acoustic Emission Signal Characteristics For Q235B Plate And Box Type Component Of Crane

Crane, the large scale special equipment, is widely used in production operations and much attention has been paid to its safety, so that its regular safety examination is greatly crucial. Currently, nondestructive texting(NDT) is the main method applied to hoisting machinery safety examination, which reduces the production efficiency. Acoustic emission(AE) technology is a kind of online monitoring technology, whose feature is to monitor the examined equipment in real-time, remedying the loopholes of the regular NDT. However, the application of AE in China is still under study. In this study, researchers applies the AE method to monitor the damage process of the plate Q235 B and box type component that are commonly used in hoisting machinery, obtains the AE signal features in this process and studies the relations between size, defect types and AE signal characteristics.(1) In the process of tensile tests of plates, the higher energy acoustic emission signal appeared in the yield stage. With the length of the defect increasing, the total amplitude decreased and the share of short duration and low amplitude signal increased in total amplitude. As the increase of defect depth, the amplitude signals divided into category A and category B, the proportion of signals with amplitude over 70 dB became more. Once the defect aperture increases, the duration time of signals between 40-60 dB gradually became shorter and the signals over 60 dB gradually longer.(2) In the process of bending tests of plates, with the length of a defect increasing, amplitude signals only appear in single concentrated areas, and energy signals had two high peak energy partitioning areas at the stage of plastic deformation. Once the defect aperture changed,multiple amplitude signal concentrated areas were transformed into one area, where the high energy signals were generated.(3) With defect length changing, the high energy signals and high amplitude signals showed up in maximum load point in the process of box type component bending. As the increase of defect depth, amplitude signals in each specimen concentrated in one area in which high energy signals were generated. The deeper the defect was, the earlier the area appeared.(4) Through wavelet analysis of AE signals from plates with different types of defect in the process of plate tensile test, the result showed that wavelet decomposed AE energy concentrated in layer D4 and D3 and frequency mainly ranged from 100 kHz to 450 kHz. With defects' length, depth or aperture changed, peak frequency mainly showed up nearby 170 kHz, 140 kHz and 130 kHz respectively.