Crack Analysis of Multi-plate Intersection Welded Structure in Port Machinery Using Finite Element Stress Calculation and Acoustic Emission Testing

Crack is the main inducement of failure accidents in welded structures of port machinery. Taking actual engineering problems occurred in a coal wharf as a case where a stacker reclaimer altered its local structure (bucket wheel changed to be chute) and then cracks appeared on the Slew deck with pylon after half a year. Using the finite element simulation combined with acoustic emission testing, the stress concentration and crack active status of the multi-plate intersection welded structure were inspected, which aimed at monitoring the development trend of the cracks and finding out reasons. Finite element stress calculation method adopts Solidworks, ANSYS and Hypermesh software co-simulation to explore the effects of mesh type and density on the stress calculation results of the Slew deck with pylon structure, and to analyze the stress distribution of the multi-plate intersection shell structures. According to the analysis results, this paper infers the reasons for crack propagation. Combined with the regular monitoring of acoustic emission testing technology on the active state of cracks and the intensity of expansion, the influences on the apparatus are deduced by the crack states of the bucket wheel reclaimer operations under different working conditions. And then put forward measures for a whole reasonable structure of the rectification and crack repair plans. The results of the research show that: 1) The maximum stress value following the change decreases slightly，which indicates that structure change is not the direct reason for cracking, instead, it is the initial structure design problems; 2) The imbalance torque produced in the boom hinge point after the change is the direct reason for causing cracks; 3) The proposed repairing scheme significantly reduces the stress at the cracks, and improves the fatigue strength. Finite element simulation combined with acoustic emission testing method provides effective means for analysis and prediction of cracks occurred in multi-plate intersection welded structure of port machinery.