The purpose and significance of structural health monitoring of casting crane is to evaluate the safety of in-service load-bearing structures, and to evaluate the safety degree or health status of the metal structure as a whole and its key parts based on on-site inspection tests, online or offline analysis of monitoring data and damage detection methods.
Therefore, it is a work of high engineering value to define the health indicators, change characteristics and their correlation with the late symptoms of structural fatigue life. It is not only instructive to the risk assessment of the accumulated strength damage history and the scrapping time point of the casting crane, but also directly verifies the accuracy of the crane fatigue life estimation technology.
According to the above engineering examples, the static stiffness, dynamic stiffness and stress intensity of the structure have obvious and interrelated changes in the middle and late stages of fatigue life estimation. The camber of the main beam decreases gradually, and the structural elasticity declines gradually. The static rigidity of the main beam is increased and the rigidity is weakened. The dynamic stiffness of the whole machine is obviously reduced, and the structure is gradually flexible. In terms of strength index, the strength weak points and stress concentration points of structural members show obvious stress growth and strength attenuation according to the order of sensitivity to external load.
In the middle and late stages of fatigue life estimation, regular and paired cracking failure occurs in the weld or base metal at the mutation of the section at the stress concentration nearest to the moving load. Especially in the late fatigue life, this kind of damage has the characteristics of not easy to check, not easy to repair, fast expansion, and recursive location.