Optimum deformation value for fatigue strength improvement by roller-working

Fatigue tests had been performed in this study to investigate the optimum value of deformation of notched specimen by roller-working using a medium plain carbon steel (JIS standards S25C). The deformation values are 0, 0.25, 0.5, 1.0 and 1.5 mm by keeping the final shapes and dimensions except for deformed value. The main results obtained are as follows: (1) The fatigue strength of notched specimen by roller-working increases with increasing the plastic deformation value when the deformation value is less than 0.5mm and reaches to the maximum value at this point. In addition. when the value exceeds 0.5mm, the result decreases. (2) The fatigue Un-Lit of D05 (roller-worked specimen by 0.5mm) is improved to 370MPa. which is about 220% of that of ND (non-roller-worked specimen). (3) There exists the optimum deformation value which is approximately 0.5mm. of notched specimen by roller-working for improving the fatigue strength.