Fatigue of metals under nonuniform stressed state. part 2. methods of the analysis of research results

We review the currently available methods that are used to explain the difference in fatigue strength of metals and alloys under conditions of uniform and nonuniform stressed states. We discuss (i) the empirical methods, (ii) the methods allowing for the difference between nominal and effective cyclic stresses, (iii) the methods based on the notions of statistical theories of strength, and (iv) the methods assuming that responsible for fatigue failure are the averaged stresses in the surface layer. The calculated results are verified against experimental findings.