Application of a Cumulative Damage Concept to Fatigue

A general concept of the accumulation of damage is described. This concept is combined with a particular hypothesis for the accumulation of fatigue damage. Initial and failure conditions are established for use with the equation and the solution for constant stress amplitude is discussed. Simple algebraic expressions are developed in terms of the nominal stresses and cycles commonly associated with machine design and stress analysis. These expressions are compared with data from rotating bending tests of steel specimens and found to be in good agreement. Nondimensional co-ordinates are used to provide a composite plot of S-N data from a wide range of steels.