Stress Concentration and Fatigue Strength of Notched Specimens Under Repeated Bending Moment (3rd Report)

Continued from the 2nd report, we treat the identical problems of the stress concentration and fatigue limit under repeated rotating bending of the circular shaft with circumferential groove of a circular arc. As to the stress concentration factor α_K of this type of notch, we can calculate approximately from auther's formula, which regard this notch of circular arc as an equivalent elliptical form, and then these calculated values were compared with that of photoelastically measured. We used 1.5kgm small type of endurance testing machine, whose test piece's dia. 6m/m, and repeating cycles per minute are 3,000. The obtained results of No.1 and No.2 low-carbon steel testpieces are that their notch factors 1.04～1.09,against to these stress concentration factos 1.37～1.45 caluculated. From these results we see the characteristic curve of α_K to the a/H ratio (a : minimum breadth, H : maximum breadth) agrees with the β_K characteristic to the d_0/d ratio.