N
Number of cycles to fracture
F1,F2,F3,…
Spring loads relative to deflections
S1,S2,S3
Fc
Calculated load given by a single disc pressed flat
s1,s2,s3,…
Deflections relative to loads
F1,F2,F3,…
h0
Formed height of unloaded single disc
I0
Overall height of unloaded single disc
L0
Length of unloaded spring stack or multiple parallel layer
t
Thickness of single disc
t’
Reduced material thickness of single disc for springs with contact surfaces
σI, σII, σIII, σIV
Calculated stresses at points I, II, III, and IV.
σ0
Calculated stress at point 0
σo
Calculated maximum stress for disc springs with dynamic loads
σu
Calculated minimum stress for disc springs with repeated dynamic loads
σu
σo-σu Working stress range relative to the
working stroke for disc springs with repeated dynamic loads
σO
Maximum stress for fatigue resistance where N≥2×106 and for
limited life where N=105 and N=5×105 cycles
σU
Minimum stress for fatigue resistance where N≥2×106 and for
limited life where N=105 and N=5×105 cycles
σH
σO-σU permissible working stress range for
fatigue resistance where N≥2×106 and for limited life where
N=105 and N=5×105 cycles
μ
Poisson ratio (0.3 for steel)
