Soderberg Method Fatigue Curve Equation

Strength and Mechanics of Materials

Soderberg Equation Method for Fatigue

( σa / σe ) + ( σm / Sy ) = 1

( τa / τe ) + ( τm / SYS ) = 1

Where:

σa, τa = Amplitude of normal (shear) stress [MPa, psi]

σe, τe = Endurance limit at constant strength [MPa, psi]

σm = Mean cycle stress [MPa, psi]

τm = Yield tensile strength [MPa, psi]

Sy = Yield tensile strength [MPa, psi]

SYS = Yield shear strength [MPa,psi] when SYS ≈ .577 Sy

Related:

Source:

Budynas, Richard G., and J. Keith Nisbett, Shigley's Mechanical Engineering Design, 8th ed., New York: McGraw-Hill, 2008.