Calculating elongation of bolt, at thread engagement? 1

[KMP04]

In order to ensure that the proper bolt preload is achieved, I have calculated a corresponding bolt elongation using the following formula:

Total Elongation = sum of [(PxL)/(AE)], at various cross sections of the bolt.

I found that the actual Torque value was less than what I estimated it would take to achieve the desired elongation.

In the above formula, does the entire nut thread engagement have equal tensile load through the entire nut thickness?
(consider "L" = nut thickness?)

 

[CoryPad]

When using the equation for screw stiffness, the effective nut height is assumed to be d/2, where d is the nominal screw major diameter. If you need a reference, it is on page 183 of Handbook of Bolts and Bolted Joints edited by Bickford and Nassar.

Regards,

Cory

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