Fatigue Strength Assessment Of Welded Joints Using Strain Energy Density Approach Based On Notch Stress Intensity Factors

The paper mainly presents a strain energy density approach based on notch stress intensity factors (NSIF) to assess the fatigue strength of welded joints. This approach simply treats welded joints asâ…¤-shaped notches. The stress field is singular close to notch tip and is only related to the notch opening angle. The stress distribution of the notch tip can be described by NSIF.In this paper, according to Williams formulation, the stress singularity exponent of a sharpâ…¤-shaped notch is derived firstly. The stress distribution close to the notch tip is analyzed by finite element model and the accuracy of NSIF has been validated. Then based on notch stress intensity factors, a research is done to the strain energy density in a sector of critical radius R. The strain energy approach has solved the problem that NSIF depend on notch opening angles and refined meshes. Despite the fact that stresses and strain energy density tend toward infinity at the point of singularity, the energy averaged in a small volume close to notch tip has a constant value and this value is thought of as the entity that can assess the fatigue strength of welded joints. Finally, according to the fatigue test data by different models, a relative curve is drawn between strain energy density and fatigue life.The approach presents in this paper independent of mesh sizes contains the effect of local welding parameters of the weld joints and can accurately describe the stress distribution in the highly stressed zones located at the weld toes. This approach has a great value in engineering to assess fatigue strength of welded joints.