On mixed mode crack initiation and direction in shafts: Strain energy density factor and maximum tangential stress criteria

•An approximate method is introduced to calculate SIFs of transverse cracked shaft.•The crack initial angle is predicted by the strain energy density factor criterion.•The mixed mode of crack initiation is studied.•The comparison between SEDF and MTS criteria for mixed mode crack is investigated.

A simple method for calculating stress intensity factors of transverse cracked shaft subjected to tension, bending and shear is introduced. New formulae of the stress intensity factors in terms of the crack depth ratio are presented. The critical loads and the normalized strain energy density factors are calculated and graphically shown. As far as the mixed modes are concerned, the initial crack growth angles are determined and mixed load ratio is investigated. The initial crack growth angles and the dimensionless stress intensity factors, obtained by minimum strain energy density factor criterion and maximum tangential stress criterion, are compared.