E	Young’s modulus
G	shear modulus
Nf	fatigue failure life
N 50	logarithmic mean fatigue failure life
S	material parameter of Smith-Watson-Topper model
k	material parameter of Fatemi-Socie model
b	axial fatigue strength exponent
b 0	shear fatigue strength exponent
c	axial fatigue ductility exponent
c 0	shear fatigue ductility exponent
ξ 1	axial stress frequency
ξ 2	shear stress frequency
φ	direction of an arbitrary plane
ν’	effective Poisson Ratio
σ y	tensile yield strength
σ u	tensile ultimate strength
τ y	torsional yield strength
τ u	torsional ultimate strength
σx(t)	axial stress
σ x,a	axial stress amplitude
τxy(t)	shear stress
τ xy,a	torsion stress amplitude
σn(t)	cyclic normal stress on the plane of φ
τn(t)	cyclic shear stress on the plane of φ
σ n,max	maximum normal stress
σ n	normal stress on the plane of φ
σ n,a	normal stress amplitude on the plane of φ
τ n,a	shear stress amplitude on the plane of φ
σ n,m	mean normal stress
τna ,max	maximum shear stress amplitude
γna ,max	maximum shear strain amplitude
ε n,a	principal strain amplitude
σ’f	axial fatigue strength coefficient
τ’f	shear fatigue strength coefficient
ε’f	axial fatigue ductility coefficient
γ’f	shear fatigue ductility coefficient