Question:-
Given that
d= diameter of spring, R = mean radius of coils
n = number of coils and G = modulus of rigidity, the stiffness of the close-coiled helical spring subject to an axial load w is equal to
Option (A)
(Gd4/64R3n)
Option (B)
(Gd3/64R3n)
Option(C)
(Gd4/32R3n)
Option(D)
(Gd4/64R2n)
Correct Option:
(A)
Question Solution:
The deflection of a close coil helical spring subjected to axial force ‘W’ is
d = R x q
Where d = Deflection of spring qc = angle of twist = (TL/GJ)
\ d= R x (TL/GJ).... (1)
Now T = W x R
L = 2p Rn
J = (p/32)d4
From equation ..... (1)

Spring constant or stiffness factor is defined as the axial force required to produced unit deflection
\ spring constant = (W/d)
\ k = (Gd4/64R3n)
question-answer-faq-3254