A spring having a center-to-center diameter of 20 mm (0.8 in.) is to be constructed of cold-drawn and annealed 316 stainless steel wire that is 2.5 mm (0.10 in.) in diameter; this spring design calls for eight coils.
(a) What is the maximum tensile load that may be applied such that the total spring deflection will be no more than 6.5 mm (0.26 in.)?
(b) What is the maximum tensile load that may be applied without any permanent deformation of the spring wire? Assume that the shear yield strength is 0.6 y, where y, is the yield strength in tension.