Stress Concentration Produced by Holes and Fillets

Abstract In many practical cases a very high stress concentration is produced by holes, grooves, notches, and sharp variation of cross-sections. This stress concentration is particularly undesirable where materials undergo reversal of stress. Coefficients of safety as hitherto employed have been large enough to cover such weakness. The modern tendency in design is to increase working stresses, thus obtaining lighter and more economical structures, and concentration of stress is thus receiving more attention. The authors attack a number of practical problems relating to holes and fillets, and employ several methods of approach; namely, analytical method giving approximate solutions for certain simple cases; photoelastic method by means of which stress concentration can be studied if the problem is a two-dimensional one; Lueders’ Line, method, the study of certain lines appearing on the polished surfaces of a mild-steel specimen subjected to simple tension or compression, at the points of highest stress concentration; and fine extensometer measurements at points of stress concentration. Analytical and experimental methods are found by the authors to be in satisfactory agreement as far as static loads are concerned. When reversal of stress is involved, the weakening effect of stress concentration can only be established accurately on the basis of fatigue tests.