Investigation on fatigue strength of a shaft with diameter enlarged partially by combination of a Cyclic bending load with an axial compressive load

This paper investigates fatigue strength and existence of mechanical damage experimentally and analytically. In particular, first, we carry out rotary bending fatigue tests and investigate fatigue strength for smooth specimens and specimen processed using the working method. Secondly, we measure Vickers hardness value to investigate strain hardening, and observe microstructure to investigate microstructure change in the diameter-enlargement part. Finally, we simulate stress and strain distribution in the processed part during the processing, using finite element method (FEM), and calculate stress concentration rate and plastic strain. And we predict the existence of mechanical damage in the processed part during the processing experimentally and numerical-analytically. The results of the experiments and analyses indicate that the fatigue damage is not generated in the processed part during the processing in the discussed range of the diameter-enlargement rate D/D-0<1.8, through comparing with the smooth specimens.