. 2022 Jul 2;12:11217. doi: 10.1038/s41598-022-15421-1

Table 4.

Parameters of designed spring arm and corresponding planar spiral spring when thickness is in unit thickness ( $b = 1 mm$ ).

Items	Value	Items	Value
Spiral radius $r$ (mm)	15.5	Spiral pitch $υ$ (mm/rad)	7.5/π
Spiral angle $θ$ (rad)	1.5π	Width $h$ (mm)	2.71
Material	18Ni(350) Maraging Steel	Estimate of variation of effective working length of each spiral arm $\hat{Δ L}$ (mm)	8.64
Elastic modulus (MPa)	200,000	Estimate stiffness of spring $\hat{K_{s}}$ (Nmm/rad)	8393.62
Number of spring arms $n$	2	FE stiffness of spring $K_{F E_s}$ (Nmm/rad)	8302.45
Estimate of effective working lengths $\hat{L_{e}}$ (mm)	70.37	Error of spring between FE and predicted stiffness ( $\hat{K_{s}} - K_{F E_s}$ )/ $K_{F E_s}$	1.13%
Estimate stiffness of single spring arm $\hat{K_{a}}$ (Nmm/rad)	4714.09	Mean stiffness of manufactured spring $K_{s}$ (Nmm/rad)	8129.81
FE stiffness of single spring arm $K_{F E_a}$ (Nmm/rad)	4704.53	Error of spring between physical and predicted stiffness ( $\hat{K_{s}} - K_{s}$ )/ $K_{s}$	3.25%
Error of single spring arm ( $\hat{K_{a}} - K_{F E_a}$ )/ $K_{F E_a}$	0.20%