Torque, or the rotational force applied to a bolt, causes the bolt to stretch like a spring. As more torque is applied, the bolt continues to expand. A Belleville spring, when being torqued, acts much like a bolt, and increases the preload of the bolted joint. Solon Belleville Springs and Washers are particularly useful where vibration, differential thermal expansion, relaxation, and bolt creep/yield are problematic. Properly torqued Belleville springs and washers lead to long service-life, self-damping and efficient use of space, and can prevent compromising joint integrity.
The widely accepted formula is as follows,
T = K*F*D
K = Estimated nut friction factor
T = Bolt torque
D = Nominal bolt diameter