EFFECT OF STRESS RATIO AND SPECIMEN THICKNESS ON FATIGUE-CRACK GROWTHOF CK45 STEEL

Presented are the effect of stress ratio and thickness on the fatigue crack growth rate of CK45 steel according to DIN 17200. Test results a re obtained for constant amplitude load in tension with three stress r atios of R = 0, 0.2 and 0.4 and three specimen thicknesses of B = 6, 1 2 and 24 mm. Microgauge crack opening values were used to calculate De lta K-eff values from which the da/dN - Delta K-eff curves are obtaine d. Crack closure can be applied to explain the influence of mean stres s and specimen thickness on the fatigue crack growth rate in the secon d regime of the two-parameter crack growth rate relation. An empirical model is chosen for calculating the normalized load ratio parameter U as a function of R, B and Delta K and, for correlating the test data. (C) 1998 Elsevier Science Ltd. All rights reserved.