Study of the Effect of Varying R-ratio on the fatigue crack growth rate behaviour of pressure vessel steels

The Discovery of fatigue occured in the 1800s when several investigators in Europe observed that bridge and railroad components were cracking when subjected to rep-eated loading. As the century progressed and the use of metals expanded with the increasing use of machines, more and more failures of components subjected to repeated loads were recorded. By the mid 1800s A. Wohler had proposed a method by which the failure of components from repeated loads could be mitigated, and in some cases eliminated. This method resulted in the stress-life response diagram approach and the component test model approach to fatigue design.