Bridge Crane Metal Fatigue Damage And Remaining Life Prediction

With the rapid development of China's economic, overhead travelling crane as important tools for lifting of plants, metallurgy and transportation. The crane plays an increasingly role in national production. As the needs of production and life, cranes often work in poor conditions. Attendant, causing crane fatigue accidents occurred frequently. In these incidents, the most serious and most common type is the characterized by fatigue cracks of overhead travelling crane's bridge fatigue damage. Therefore, it's obvious important as we study the causes of fatigue cracks and cracks expansion, as well as the remaining life of crane metal structure.There have been numerous methods for the crane's fatigue fracture and residual life, but these methods either remain in the theoretical stage, either model is too simple; and in the analytical procedure, they only studied the two fatigue limit stage, the deformation stage and the damage stage, and they didn't study the reasons for the formation of these cracks and deep mechanism. So, they can't meet the safety of actual production.This topic combined the fracture mechanics and damage mechanics, studied the overhead travelling crane's fatigue cracks. First, use the finite element analysis software ANSYS, built the dimensional modal of the overhead travelling crane, to finite element analysis of the dimensional modal to the typical working conditions, and drawn the corresponding stress diagram and strain displacement diagram, and to identify the danger point. Secondly, attached the strain gauges to the risk location of the overhead travelling crane, collected the fatigue load date of the actual crane. Then use of rain flow counting method, processed the stress-time history data, obtain the fatigue load spectrum of the crane. Thirdly, analyze the fatigue mechanism of overhead travelling crane; explore the causes of fatigue cracks. Meanwhile, classify the cracks of the crane, the one is the linear elastic crack; the other is elastic-plastic crack. Analysis the stress intensity factor of the two different cracks, and discuss the stress field near the cracks. Then, according to the iterative method, obtain the stress intensity factor and the stress field in the case of multiple cracks. Finally, combined the fracture mechanics and damage mechanics, derived the fatigue life formula of overhead travelling crane under the constant amplitude loading and variable amplitude loading. Meanwhile, development the life prediction software of crane box girder, then used the prediction software on the actual crane, derived the assessment life of the overhead travelling crane.