It is well appreciated that materials act differently from one another. For example, some metals are brittle, while others are quite flexible. Even at a microscopic level, there are differences which are important. For example plastics can form long thin layers, whereas metals often have a more granular structure.
Some materials crack easily, whereas others resist cracking for a long time, until suddenly they shatter. This research is concerned with the rôle of the material in the whole fatigue process. Specifically, the material can affect the way in which cracks propagate, with such propagation dependent on a combination of external and internal material effects. In particular, some of the parameters of the model take into account such features as temperature, crack geometry and strength of grain boundary.