EFFECT OF RIPPLE LOAD ON THE STRESS-CORROSION CRACKING IN STRUCTURAL STEELS
The presence of small ripple loading can, under certain circumstances, significantly reduce time-to-failure and threshold stress intensity for stress-corrosion cracking (SCC) of steels. A predictive framework for such ripple-loading effects (RLE) is developed from concepts and descriptors used in SCC and corrosion fatigue characterisation. The proposed framework is capable of defining critical conditions required for the occurrence of RLE and predicting time-to-failure curves. The agreement between the predicted and laboratory data is excellent.
Correlation between sustained-load and fatigue crack growth in high-strength steels
Correlation between sustained-load and fatigue crack growth in high strength steels for aggressive environment effects
Computer-Controlled Decreasing Stress Intensity Technique for Low Rate Fatigue Crack Growth Testing
An automated test system utilizing computer control was developed to obtain crack growth rate data down to the fatigue crack growth threshold with a decreasing stress intensity technique and compact type specimens. The starting stress intensity range ΔK0 was chosen to yield crack growth rates in the range of 2.54 × 10−8 m/cycle (10−6 in./cycle) and subsequent values of ΔK are controlled to the equation ΔK = ΔK0 exp [C(a − a0)] (a0 and a are the initial and instantaneous crack lengths and C is a test variable). Crack length is continuously monitored by using the elastic compliance technique, thereby enabling ΔK to be decreased continuously. Comparison crack growth data were also obtained by the more conventional constant load amplitude or K-increasing method. Excellent agreement was observed between data obtained from the two procedures for a Society of Automotive Engineers 1045 steel at load ratios R of 0.1 and 0.5, an A356-T6 sand-cast aluminum alloy at load ratios of 0.1 and 0.8, and a 2219-T851 aluminum alloy at a load ratio of 0.1.