1982 Volume 68 Issue 9 Pages 1430-1436
Fatigue properties of high strength steel sheets were studied in connection with the effects of tensile strength, sheet thickness, yield ratio and tensile prestrain.
Materials examined in the present study were cold rolled and hot rolled steel sheets of conventional and low yield ratio types. Fatigue tests were carried out under the conditions of pulsative axial tension and alternative out-of-plane bending.
Principal results are as follows:
(1) Fatigue strength increased in proportion to the increase in tensile strength up to 70kgf/mm2, then it gradually leveled off above 70kgf/mm2 up to 140kgf/mm2.
(2) The thinner steel sheets had the higher fatigue strength. This tendency was more significant under out-of-plane bending condition than under axial tension condition.
(3) Low yield ratio type steel sheets in virgin state had lower fatigue strength compared with conventionl steels of the same tensile strength. However, this difference in fatigue strength almost disappered after prestraining of sheets.
(4) Empirical formulas to estimate fatigue endurance limit were proposed on the basis of a multiple regression analysis in connection with tensile strength, sheet thickness, yield ratio and elongation of steel sheet.
