Effects of Overload on Threshold Stress Intensity Factor Range Δ<I>K<SUB>th</SUB></I> of Steel

Abstract

mprovement in the threshold stress intensity factor by tensile overload in large crack was investigated. The crack retarded zone and the non-propagating crack size was validated based on the fracture surface observation. It was observed that crack propagation was retarded by the overload during the fatigue tests. The size of non-propagating cracks and the crack retarded zone corresponded well to the calculated value . Moreover, in order to evaluate the overload effects on the small crack like defect, bending fatigue tests were carried out and discussed the effect of crack size on the improvement of the ∆Kth.

Overloading effect on the fatigue threshold stress intensity factor range (ΔKth) as a function of crack length in SUS316

“…The above equation agrees reasonably with the experimental results reported by Ogawa et al (1987) and Mizukami et al (2008), and indicates that DK th slants upward at a slope of 0.28.…”

“…When the overload s ov was comparable to the yield stress s y , the plastic zone size rapidly increased, causing the large-scale yielding. Figure 6 shows a comparison between experimental data including previous data (Ogawa et al, 1987;Mizukami et al, 2008) and calculations under plane stress and plane strain, indicating that experimental data agree best with calculations assuming plane strain. Hence, the Dudgale model indicated that a tensile overload applied to a cracked material would produce a compressive residual stress field, which would contribute to improving DK th .…”

“…Ogawa et al (1987) demonstrated the effect of load history on the threshold stress intensity factor range DK th of carbon steel. Mizukami et al (2008) reported that tensile overload increased the threshold stress intensity factor range DK th of high strength steel HT540.…”

Analytical investigation of effect of stress ratio on threshold stress intensity factor range improved by overload

“…Figure 2 shows the correlation between the stress intensity factor at overloading K ov and Δ N K th,R . Figures 2(a) and (b) show the relationship for HT540 (Mizukami et al , 2010) and SUS304 (Hashikura et al , 2010), respectively. To confirm the overload effect, Δ K th,R was first measured using a standard fatigue test with no overload.…”

“…Most of the studies on overload are about an effect on a crack initiation or a behavior of crack propagation (Wheeler, 1972; Usami and Kitagawa, 1981; Wheatley et al , 1999). However, few studies regarding on an arrest of crack propagation are found (Hashikura et al , 2010; Mizukami et al , 2010).…”