Development and early growth of fatigue cracks from corrosion damage in high strength stainless steel

This paper investigates the influence of localised corrosion flaws caused by pitting and crevice corrosion in 15-5PH high strength stainless steel on the development and early growth of fatigue cracks. Fatigue specimens fitted with a crevice former were exposed to a 5%NaCl solution in a salt spray cabinet to produce a single flaw in the middle of the specimen and then tested in fatigue. The development and early growth of fatigue cracks were recorded using a range of techniques. After failure the shape and size of corrosion flaws where cracks initiated were measured and their largest Kt values determined by finite element analysis. Considerable variability in life response to defect Kt was found. Comparison of experimental crack growth data with fracture mechanics predictions showed evidence of a significant number of cycles occupied in transforming defects into cracks in some initiating flaws.