Bolt Extension
Bolt Extension
(OP)
Just a quick cry for help.
I have a bolt that is subject to a load hydraulically, so in that I know precisely what the loading is on the bolt.
Once stretched, the nuts are locked and the pressure released.
Obviously, the bolt has extended slightly to retain the load. I need to double check the theoretical compared to the actual results. Could someone help in guiding me to the calcs to work the theorectical?
Thanks
I have a bolt that is subject to a load hydraulically, so in that I know precisely what the loading is on the bolt.
Once stretched, the nuts are locked and the pressure released.
Obviously, the bolt has extended slightly to retain the load. I need to double check the theoretical compared to the actual results. Could someone help in guiding me to the calcs to work the theorectical?
Thanks





RE: Bolt Extension
Bickford is also useful and gives the calculation as
L = PL*(1/Kb)
where
L= change in lengh
PL = Preload
Kb = bolt stiffness
good luck
www.priamengineering.co.uk
RE: Bolt Extension
You can estimate the amount of elongation of the bolt assuming thats what your trying to check
x= P*L/A*E
x = change in bolt length
L = original bolt length
A = area of bolt cross section (you may want to use the pitch dia to get this area)
P = known preload
E = modulus of elasticity of bolt material
desertfox
RE: Bolt Extension
RE: Bolt Extension
RE: Bolt Extension
You'll need to consider the stiffness of both the fastener assembly and the clamped structures in your analysis.
If you want to have an accurate validation of both your analytical model and your fastener installation process, you should check the strain of an installed fastener. Or better yet, a statistically relevant sample of several installed fasteners. This can be done by careful dimensional measurements of the parts, or by other methods such as ultrasound: http://www.gammatecsa.com/-bolt-tension-monitoring-
Good luck.
Terry
RE: Bolt Extension
He is not trying to analyse the joint as I see it otherwise I would agree about considering flange stiffness.
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desertfox
RE: Bolt Extension
see this link:-http://
RE: Bolt Extension
Knowing the physical parameters of the bolted connection would be interesting such as number of bolts, pattern, size and operating conditions.