Experimental and analytical approach of fatigue behavior of stepped CK45 shaft with adjacent key groove

Stress concentration areas such as keyways and shaft steps appear frequently used in mechanical engineering design. Areas like these are characterized by difficulties in accurately predicting part operating lifetime, often driving into premature fractures causing unplanned machine stoppages. The impact of such areas in engineering design is assessed with the aid of the “k-factors”, however, these factors cover only the effect of a single notch on the whole structural element. In mechanical engineering design it is common for multiple stress concentration areas to coexist adjacently, where the existing analytical theory cannot be used to assess the effect. The effect of adjacent step and keyway on a DIN CK45 shaft is investigated in the present paper. For this purpose, a DIN CK45 steel shaft specimen with a standardized keyway and a diameter-step has been tested under rotating bending to investigate the interaction of two distinct stress concentration areas. Analytical and numerical methods have been used to support the conclusions.