Torque and Chrome

how nut gets tightened while applying torque on it?

Am working in a fuel injection company . after the endurance testing i've seen a nut used in my product which is loosened which actually has a tightening torque of 25nm was turned as 5 nm . while using a wrench. is it necessary to have a loosening torque equal to that of tightening torque is that phenomenon changes with vibrations and pls explain me how does the nut gets tightened when it is applied torque

Public Comments

1. After nut tightened by applying a torque, some of its portion will be deflected, δ = F_i * L / AE This force, F_i is pre load tension, which determine nuts tightening. The force or the deflection may occur because nut(female threaded) surfaces when subjected to other(male threaded) surfaces will have friction, thus the friction make the nuts in its final position and means more tight after torque applied to it. Torque equation, T = K*F_i*d K = torque coefficient ~ 0.2, function of coeficient of friction and dimension Fi = Preload d = Nut diameter