Research On Random Fatigue Of The Metal Structures Of Ladle Crane

Ladle crane is the key equipment of the production line in iron and steel enterprises which is used to transport high-temperature liquid metal. For the working conditions of ladle crane is extremely bad, fatigue failure accidents happen frequently. Therefore it is necessary to find out the stress distribution of the ladle crane and establish the dangerous site's load spectrum in order to ensure the safe operation and extend the service life of ladle crane. According to the load spectrum and mechanical properties of materials, fatigue life of ladle crane can be estimated correctly.This paper took a 450t/80t 4-beams-6-tracks ladle crane of the second steel plant of Baosteel for subject investigated to analyze stress of it's bridge structure with the research method combining FEM with field testing. Base on it, "shell-to-solid submodel" method was used to finely analyze high stress and severe stress concentration region——welds in mid-span of the main girder to obtain stress distribution of this area. It is found that stress and deflection of the inside main girder reach the maximum. While the main hook is fully loaded at mid-span, the maximum shear stress of welds at mid-span and the end web had exceeded the fatigue limit of the material, which is the dangerous position of the ladle crane.According to the load spectrum established by the combination of field test and finite element analysis, fatigue life of the dangerous site's such as welds at mid-span of the main girder and at the end web were estimated by modified Miner theorem. The p-S-N curve of material was modified so as to bring the effect of stress cycle below the fatigue limit into consideration. It is found that fatigue life of welds at the end web are low and these areas should be checked frequently.One method used in this paper, combining FEM with field testing, applicable for not only fatigue analysis but also life estimation of the ladle crane.