R	strain ratio
ΔWp	plastic strain energy
ΔWe	elastic strain energy
σ m	mean stress
${\mathsf{\sigma }}_f^{\prime }$	fatigue strength coefficient
b	fatigue strength exponent
${\mathsf{\epsilon }}_f^{\prime }$	fatigue ductility coefficient
c	fatigue ductility exponent
E	Young’s modulus
σ a	stress amplitude
σ u	tensile limit of material
σ eq	equivalent stress amplitude
γ	material constant of Walker model
α	material constant of Kwofie model
β, n	material constant of Wang’s model
$k_{\sigma }$, $k_{\epsilon }$	material constants of proposed model
N f	experimental life
N p	predicted life
z	discrepancy of predicted life and experiment life
Sz	discrepancy level of predictions