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Study of the acoustic emission characteristics of weld cracks in carbon steel pressure vessels

For the purpose of rapidly detecting and evaluating active cracks in the weld seam and the heat-affected zones of carbon steel pressure vessels, acoustic emission (AE) tests are conducted on a pressure vessel with natural cracks. The AE locations and parametric distribution characteristics
 of these cracks are investigated and presented. It is shown that surface cracks propagate and generate AE location sources at lower pressures than internal cracks. For both internal and surface cracks, more than 85% of the AE location sources are generated during the initial pressurisation
 steps. During the depressurisation steps, surface cracks may also generate AE location sources due to crack closure. Compared with the parametric distribution of hits, the peaks in the distribution graph of AE location sources in the main parametric scale shift to higher parametric values.
 In this study, the amplitude of the AE location sources is approximately 53 dBAE , the energy is around 32 eu, the rise time is in the range of 20-100 μs and the count is in the range of 1-200. The distribution of corresponding parameters of AE hits is similar for both surface
 and internal weld cracks. The AE location and parametric distribution features can be used directly to identify weld cracks.