Similitude: Fatigue cracking in steels

The ability to understand and predict fatigue crack growth is central to both the design and the continued operational safety of aircraft, rail, offshore structures, nuclear power plants, and many other engineering assets. However, most current crack growth models are based on the concept of similitude. This paper examines cracking in a range of steels and reveals that the similitude hypothesis is invalid in Region I, where the crack growth rate is low.