The multi-axle fatigue analysis of welded joints based on notch stress method
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Abstract:
As the existing fatigue assessment curves of welded joints are only applicable to uniaxial load, we analyzed the multi-axial fatigue of welded joints on the basis of notch stress method. Firstly, through the combination of the nominal stress data in the multi-axial fatigue test of welded joints and the notch stress concentration factor calculated by finite element method, the notch stresses of 5 kinds of welded joints in different directions were obtained. Secondly, equivalent notch stresses were respectively calculated according to 3 kinds of multi-axial fatigue criteria, i.e. Von Mises, ⅡW (International Institute of Welding) and EESH (equivalent effective stress hypothesis), and they were unified into the same coordinate system. Finally, the fatigue life curves that were applicable to the assessment of the multi-axial notch fatigue were fitted out with the least square method. Compared with the uniaxial curve recommended by ⅡW, the multi-axial fatigue curves have lower inclination and higher fatigue class. The fatigue strength value within the mid-circle range from 103 to 106 circles is obviously reduced when multi-axial is loaded, while the influence on the high circle fatigue range from 106 to 107 circles is relatively limited.
