Fatigue life evaluation of welded joints under combined normal and shear stress cycles

This paper discusses methods for evaluating the fatigue life when combined normal and shear stresses are applied in phase simultaneously. The conventional fatigue design procedures based on maximum principal or normal stress ranges are reviewed using published data. This indicates that the fatigue life may be under- or overestimated by the procedures, when the shear-to-normal-stress ratio range is close to 1.0. A proposed alternative procedure, based on the equivalent stress range and the fatigue life for a normal stress range, produces a much more appropriate evaluation of the fatigue life for combined stress ranges, independent of the ratio.