critical plane	The plane that has the maximum shear strain range over a loading cycle
FSDP	Fatemi–Socie damage parameter
RS	Residual stress
D FS	The maximum FSDP on all the critical planes of a material point
(DFS)max	The maximum DFS of all material points
N f	Fatigue initiation life of a material point
(Nf)min	Minimum fatigue initiation life of all material points or fatigue initiation life of the gear surface
α	Plane orientation
α c	The orientation of the critical plane corresponding to DFS
Δγ	The maximum shear strain range on a plane over a loading cycle
σ n,max	Maximum normal stress on a plane over a cycle
σ surface	RS at the surface
σ max	Peak RS
y max	Depth of σmax
y core	Depth where RS vanishes
σ max,t	The transition value for σmax
Subscripts
opt	Values associated with the optimum RS distribution
1, 2, 3, …	Values associated with plane 1, 2, 3, …