Effect of Supplementary Notch on the U Notch in a Plate under Pure Bending

Abstract

The effect of supplementary notch on the reduction of stress concentration of the initial notch (Hereafter will be called 'mother notch' in this report) is widely known, and in connection with this subject many studies are reported. Most of them, however, are concerned with multiple notches of the same configuration. From this point of view, the authors investigated on the effect of supplementary notch with a different shape from that of the mother notch.
Two supplementary notches of the same shape were cut symmetrically on both sides of the mother notch, and their notch depth and root radius were varied in several steps. The effect of the root radius was small for a constant depth, but the notch depth showed a large influence, reducing the stress concentration factor of the mother notch remarkably at a little smaller depth than that of the mother notch. By finding the intersection point of two curves representing the change of stress concentration factor due to the notch depth, the optimum condition for the minimum stress concentration of the notch system was obtained at a given root radius of the supplementary notch. From the scope of the present experiment, it may be concluded that the most effective supplementary notch is that with a depth a little smaller (About 90%) and a root radius somewhat larger than those of the mother notch. In the case of the most optimum condition, the reduction of stress concentration factor showed the amount of about 11%.
The case of two equal mother notches was also examined, and the relief of stress concentration was larger, because two mother notches act mutually as a supplementary notch to each other.