Method of Virtual Mean Stress Fatigue Curve Equation

Strength and Mechanics of Materials

The virtual mean stress has a corresponding mean strain which conditions result in biased stress/strain limits under cyclic load. It is shown that residual stress relaxation is associated with mean stress shift in stress-axis direction and mean strain shift in the strain axis direction.

Method of Virtual Mean Stress

Where:
Amplitude of normal = Amplitude of normal (shear) stress [MPa,psi]
Endurance limit at constant strength = Endurance limit at constant strength [MPa,psi]
Mean cycle stres = Mean cycle stress [MPa,psi]]
Virtual mean stress = Virtual mean stress [MPa,psi]
Haigh factor diagram narrowing = Haigh factor diagram narrowing
Coefficient; For BendingĀ  = Coefficient; For Bending  Bending formula

For shear Shear formula