Research On Fatigue For Crane's Structure Based On Finite Element Methods And Fracture Mechanics

High attention has been always paid to the safe use of crane, as one of the national special equipment. But for many reasons, the phenomena of accidents happening still exist. The common malfunctions, which are also the most important malfunction, are malfunctions characterized by cracks in metal structure of cranes. Practice has proved that the structural damages usually result from the risk of fatigue extension of the partial weld crack on the cross section. Therefore , the researches of reasons about how cracks occurred and the trends they will expand to ,for preventing the happening of the fatigue fracture and guiding the product design, manufacturing ,testing and management ,are of great importance .The metal structural intensity calculation and fatigue analysis of crane are very complicated problems among the existing various analysis ways, based on the theory of finite element method which is so far considered as a more reasonable and effective method . In this paper ,taking theE3# 75/20t×16m bridge crane for study ,which is produced by Second Steel Rolling Factory of Steel and Iron Corporation of MA AN SHAN, to analyze the reasons about how the cracks occur on the web-side of the end beam.In this paper, using large-scale finite element software ANSYS to model the finite element and analyze the statics, combining with finite element fatigue analysis software MSC.FATIGUE and fracture mechanics to assess the structural performance and fatigue life span.In this paper, first of all, operating the finite element modeling on the bridge structure of the crane, simulating the actual situation ,then we can make a specific analysis on the bridge structural static of this kind through four situations which have the finite element static analysis on the bridge structure for figuring out the main reasons on malfunctions and proposing possible improvements.Then, we can select appropriate methods of fatigue analysis according to the production date by the providers, combining with the use of MSC.FATIGUE, the full life analysis module , to analyze and design the ideal life for the bridge structural crane.The fatigue life distribution on the cloud chart under the approximate actual situation, it visually shows fatigue life of the various parts of the metallic structures, so that designers can comprehensively understand the fatigue life distributions of different parts about the bridge crane, and it proves a visional and comprehensive basis for comparing different design options or comparing advantages and disadvantages of fatigue functions in short time or improving the designs .At last, we use the linear elastic fracture mechanics methods from the aspect of practicability to assess the welding structural accumulated fatigue crack extension life span on the bridge-like crane under the random load and to calculate and draw out graphs about the extension of cracks on the web plates of end beams on cranes and cycle curve of this machine and to summarize the law of extension of cracks on the web plates of end beams on this type of cranes.We found that the results of analysis on bridge statistic performance is more reliable through comparisons with the real situation ,that is also show that the methods in this paper have important project practical sense and the suppliers repaired according to our proposals .Our analysis provide theoretical basis for the safe use and repair ways on the structures of this type of bridge crane.