The Study On Fatigue Performance And Its Influencing Factors Of Typical Welded Joints In Passenger Car Bogie

Welded joints are the most fatigable parts on the welded structures; therefore the welded joints should be considered more within the study of the welded structures.In this dissertation, the fatigue character of 3 kinds of welded joints, end to end welded joint, cross shaped welded joint and corner welded joint, which were provided by Chang Chun Railway Vehicle Co,. LTD was studied by p-S-N curve fatigue testing and finite elements analysis.First of all, the procedures of p-S-N curve fatigue test, data processing and p-S-N curve plotting were introduced in the paper. And then, these procedures were taken into practice on those 3 kinds of welded joints mentioned above. As the results, the mid-long fatigue life p-S-N curves of the welded joints with different fraction surviving, 50%, 90%, 95%, and the corresponding equations were gotten. Afterwards, basing on the direct prolonging method and Haibach revision method, all the mid-long fatigue life p-S-N curves were prolonged to long fatigue life regime.In order to examine the effect of the notch stress on fatigue strength of weld joints, static load was applied on the welded joints, meanwhile strain gauges were used to measure stress on weld toes and base metal to calculate the stress concentration coefficients. Whereas, finite elements simulating calculation was also borrowed to verify results gotten by the testing method and to get the stress concentration coefficients of some areas where the stress gauges were inconvenient to past on the welded joints. After this, all the results from tests and simulating calculation were analyzed.Weld defects are also very fatal actor for the fatigue strength of welded joint. In this dissertation, several kinds of common internal, external defects and irregular geometry shapes defects were simulating calculated by finite elements method. According to the result of simulation, some conclusions were drawn.