Research On Fatigue Strength For The Structure Of Gantry Crane

The integration of the global economy and the sustained growth of the foreign trade in our country have given further impetus to the explosion of the logistics industry of harbor in our country. Therefore, our requirement for the port crane which is the most important tool of the logistics of the harbor is higher and higher. The design of cranes generally stops at static analysis in the past. When static analysis is sufficed, the crane still exists a significant security risk. Because of frequent job, many of which are random load, welding structural role in the low stress repeatedly, will have a fatigue phenomenon. When fatigue failure occurs, the structure will be a sudden brittle fracture, resulting in huge losses, and may even cause accidents. In major crane incidents, the most serious caused by fatigue. Therefore, the study of fatigue crane performance and the estimation of fatigue life, are very concerned about by technical staff at present.With the development of computer technology and finite element analysis, the fatigue analysis method gets a wide range of applications. At the product design stage, designers can compare the different options for the length of the fatigue life and check whether the fatigue life of products can meet the requirements of the design by this method. At the product experimental stage, designers can determine the risk parts of fatigue and reduce unnecessary expenses through the method. However, fatigue analysis depends on the tests which need to spend enormous human resource, material and time. Because of the great discreteness of structural fatigue and the big difficulty to carry out fatigue tests for cranes which means large-scale welded structure.This article elaborated detailedly the fatigue performance and theories of the welded struction with the combination of the characteristics of the crane metal structure. By the use of FEM software MSC.patran&MSC.nastran we can set up the finite element model of the gantry cranes. And according to the theoretical calculation of static strength, we can give static strength analysis to the gantry cranes which will lay the foundation for the Fatigue Strength Analysis of it. Starting from kinetic theory, we can use the FEM software to carry out modal analysis of the crane which can help to extract the first few stages of the natural frequencies and mode of vibration. With the combination of the two methods of fatigue analysis - stress ratio and stress amplitude method, we can utilize respectively the VB programming and fatigue analysis software MSC.fatigue to calculate the fatigue strength and evaluate the fatigue life of the crane, which will give a certain reference value for the crane's design and maintenance.