Implementation And Application Of The Weld Fatigue Life Evaluation System Based On Master S-N Curve

In order to achive the national railway development targets of high-speed and heavy-duty, the railway vehicles tend lightweight design. Reducing the weight of the vehicle structure is bound to increase the structural strength requirements. The static strength of the structure can be satisfied by using reasonnable structure identified by the way of simulation and experimental methods, while the fatigue strength of the structure is not easy to predict because of some limitations of the current theory of fatigue strength at home and abroad, using them can not accurately predict the fatigue life of the structure. The vast majority of structural fatigue belongs to weld fatigue. For weld fatigue, master S-N curve method invented by Professor Pingsha Dong has a rigorous theoretical basis and large amount of experimental data supporting, which can be relatively and accurately predict the fatigue life of the weld. Therefore, the design of procedures for predicting the weld fatigue life according to the master S-N curve theory is particularly important.Firstly, used the finite element pre-processing software hypermesh to estimate a finite element model of steel by unit number shell181, and two welds along the same direction in the finite element model. Imported the finite element models into the ANSYS finite element analysis software for static strength analysis, achived rst files containing welds nodal force information. Meanwhile, exported out inp file containing the weld information from hypermeh.Secondly, respectively analyzed data structure of rst file and inp file. Used data-processing software Matlab to write procedures which can extract both weld nodal forces information from the rst file and weld information from the inp file. According to the weld fatigue life calculation process based on the master S-N curve theory, edited the graphical user interface by Matlab, inserted appropriate callback functions to achieve operability of calculating weld fatigue life, ensuring the integrity of the calculation procedure.Upon completion of the calculation procedures, sequentially read rst file and inp file of a simple finite element model, extracted data needed for calculation. At specific Fatigue conditions selected the appropriate load spectrum and the master S-N curve, calculated the stress damage ratio of all welds in the finite element model. Exported them into corresponding Excels, based on results of professional welding fatigue life software verified the correctness and reliability of the procedure.