Development of a fatigue crack growth testing apparatus and its application to thin titanium foil

• Published in: Fatigue & fracture of engineering materials & structures Vol. 36; no. 11; pp. 1187 - 1198
• Main Authors: Lee, C.-W., Liu, L., Holmes, J. W.
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.11.2013; Blackwell; Wiley Subscription Services, Inc
• Subjects: Applied sciences; Crack propagation; Exact sciences and technology; Fatigue; fatigue crack growth rate; Fatigue failure; fatigue testing; finite element analysis; Foils; Foils (structural shapes); Fracture mechanics; incomplete self-similarity; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metal fatigue; Metals. Metallurgy; Paris; Stress intensity factors; Testing equipment; Titanium; Propagation velocity; fatigue crack growth rate; Growth; titanium; Mechanical properties; Fatigue; finite element analysis; Modeling; Fatigue crack; Crack propagation; Finite element method; fatigue testing; Thin sheet; Development; incomplete self-similarity; Application
• ISSN: 8756-758X; 1460-2695
• DOI: 10.1111/ffe.12086

ABSTRACT A low‐cost experimental apparatus has been developed to investigate the mode I fatigue crack growth behaviour of thin metallic foils and sheets. The apparatus utilizes magnetic coupling between a ceramic magnet and a rotating steel disc to induce cyclic tensile loads in notched rectangular specimens. To illustrate the testing apparatus, mode I fatigue crack growth in 30‐µm‐thick high‐purity titanium foils was studied. Experiments were performed at ambient temperature using a loading frequency of 2 Hz and a nominal stress ratio of 0.1. The cyclic crack growth data could be fit to a Paris relationship between crack growth rate and stress intensity range. The stress intensity factor exponent, m, in the Paris relationship was between 4 and 6, which is comparable with the relatively high values found in the literature for the tension–tension fatigue of other metallic bulk materials. Incomplete self‐similarity analysis was used to explain the observed higher m values for thin metallic foils.