Effect of Corrosion Products of Crack Face by Nitric Acid on Fatigue Crack Propagation Properties

Recently, multiple fatigue life extension techniques have been proposed utilizing crack closure, while no detailed mechanisms have been discussed for them. On the other hand, the authors have proposed the assessment method on crack initiation and propagation life based on an elasto-plastic model, and that would work for better assessment with detailed mechanisms of them. In this paper, fatigue crack growth tests were carried out using SENT specimens corroded at the crack length of 3mm by 35% HNO3, and shape measurements for fractured specimens were conducted after the tests. The results show that crack growth rates are retarded due to corrosion products between crack faces (Wedge effect). Furthermore, corrosion products distribute on the crack faces with 20 to 50µm thickness, which suggests correlations between the thickness of corrosion products and the level of life extension effect. ©2023 The Society of Materials Science, Japan.