Very high cycle fatigue behavior of a low strength welded joint at moderate temperature

Very high cycle fatigue (VHCF) behavior of a low strength weldment was investigated by fully reversed axial tests in air at room temperature and 370 °C. The role of non-metallic inclusions in the VHCF was addressed in terms of experimental results and finite element simulations. The higher potential for interior crack nucleation at higher temperature was ascribed to matrix softening, surface oxidation and surface compressive residual stress. A new model for interpretation of the role of inclusion in the transition of crack initiation modes was developed.

► VHCF of a low strength weld metal was investigated at different temperatures.
► Duplex S–N curve with different crack initiation sites was observed at 370 °C.
► Matrix softening, oxidation and compressive RS affect the interior initiation site.
► A new model was proposed to evaluate the transition of crack initiation modes.