Research On Fatigue Life In Weld Of Main Beam For Lightweight Overhead Cranes

Overhead crane has been widely used in various sectors of national economy, and its output grows rapidly with the needs of the development of modernization construction in our country. However, the product structural forms of existing universal bridge crane in our country, although with many improvements, main adapt forms of the former Soviet Union in1950s, which leads to big gaps when compared with the international leading level.In the lightweight overhead cranes, advanced structure and technology have been adopted, which are mainly used for the optimization for metal structure, such as main beam, end beam and trolley frame, and reducing the structural weight and height as well as decreasing the cost of production. The main beam is the main load-bearing body in bridge crane. The application of lightweight technology in the girder metal structure has achieved weight loss under the condition of satisfying the request of strength, stiffness and stability. Therefore, the service life of the machine will be determined by the fatigue strength of light beam. While the destruction of the main beam, which is a welding box beam structure, is mostly caused by the fatigue damage of welded structure. Hence, the investigation of the fatigue life of the weld is one of the main technical of lightweight design of the overhead crane.In this paper, equivalent structural stress weld fatigue theory is used. Application finite element analysis software ANSYS request the node force and moment at weld toe of the weld tool. The VERITY module of software FE-SAFE, in which core technology is equivalent structural stress method, is used to calculate the nodal equivalent structural stress and fatigue life. Finally, ANSYS post processing module is adopt to obtain fatigue life contours of weld. In order to solve the problem of fatigue life of light beam welding, the main work is as follows:(1) The analytic method of welding fatigue by using the equivalent structural stress was investigated, and the module VERITY of software FE-SAFE weld fatigue analysis flowchart was explained in detail.(2) Finite element static analysis of light main beam was made. In condition of satisfying the prerequisites of strength design, the fatigue life of main beam and relating factors were analyzed to get the influence law. Finally, proper weld structure was proposed to meet the fatigue performance of main beam.(3) Completion of the main beam fatigue tests. In terms of the main beam fatigue test, large number of experimental data was got to verify the safety of new crane girder structure design. At the same time, valid data and design experience were accumulated for lightweight overhead crane basic design research.