I need to calculate torque needed to tighten the bolt.
Problem is that the bolt and the hole are not of the same material, and the thread engagement length is fixed - usually smaller than recommended.
I just want to know is this right way to do it, or at least on the right track.
L - thread engagement length
P - thread pitch
D - outer diameter of the bolt
d2 - pitch diameter
u - thread coefficient of friction
us - bolt head-surface coefficient of friction
rs - effective radius of bolt head-surface connection
T - shear strength of the weaker material - ~0.6 of tensile strength
As = 0.5*pi*L*d2 - shear area
fi = atan(u/cos(30°))
ro = atan(P/d2*pi)
F = T_hole*As - shear force
T = F*(d2/2 * tan (fi+ro)+us*rs)