[DeTomaso] Studs and stretching question
Dave
dave at damardirect.com
Fri May 1 12:36:29 EDT 2015
I am sorry. I did not think that direction. I got into a conversation about studs and remembered something about stretching, hence my question.
Here you go (be sure to read the entire article, quiz tomorrow)
IndyDave
“Bolts are normally tightened by applying torque to the head or nut, which causes bolt to stretch. The stretching results in bolt tension, known as preload, which is the force that holds a joint together. Torque meter can be used to measure bolt tension. High preload tension helps to keep bolts tight, increases the strength of a joint, and generates friction between parts to resist shear and improves the fatigue resistance of bolted connections.
Bolt Tensioning
A bolt and nut are designed to act together as the internal threaded fastener (nut) is tightened onto the externally threaded fastener (bolt). The bolt is forced to stretch and elongate. This stretching/elongation is maintained by the head of the bolt and the nut on the joint thereby maintaining the joint at the desired tension (Bolt tensioning).
As a rule, the joint will have been designed with sufficient fastener to apply the required clamp load at 65% of the fastener proof load stress figure i.e. well below the fastener’s yield point.
Yield point or yield strength
It is defined as the load that is necessary to stretch the fastener to the point where, after the load is removed, the bolt will not return to its original or previous length. It has moved from being elastic to plastic behavior.
In order for the fastener to incur a longer length part of bolt donates material. This will come from the threads, which are the weakest part of the bolt. A section of the threaded portion of the bolt wall suffers a reduction of area and will “neck out”, creating a “dog bone” appearance. The change in stress area makes the bolt considerably weaker and as the bolt is stretched even further the clamping load decreases. Additional stretching (caused by operator attempting to retighten the joint and fastener) will cause the bolt to break at its tensile point.
Clamp load
To produce clamp load, the fastener must be placed in tension. If the fastener is not stretched then there is no clamping load. Once the bolt is clamped and firmly seated in the joint bolt tension now results from the turning of the nut along the threads of the bolts. The bolts start to stretch elastically, proportional to the amount of nut advancement. As the nut is further turned the threads of the bolt and nut are forced together under enormous pressure generating friction between the mating threads and also causing tensional twisting to the body of the bolt between the clamped surfaces. The bolt is experiencing two forces simultaneously, tension and torsion.
In a bolted connection, the bolt must be stretched sufficiently to produce static preload upon the connection that is greater than the expected external load rather than the joint assembly acting upon the bolt themselves. These external loads must be known so that the proper grade, size, diameter, thread pitch and number of fasteners can be chosen to create a safe joint or fastening.
When selecting the proper grade of fastener, proof load is the most important physical property of the fastener. Proof load is the maximum safe load that can be applied to a fastener without inducing permanent deformation, as with yield. Tensile strength is the point at which the fastener will break. The fastener must be stretched far enough to produce a pre-determined amount of safe preload to the assembly without causing any permanent damage to the fastener.”
http://www.industrialaids.com/upload/Summary_of_Bolt_Tensioning.pdf
From: Bill Moore [mailto:bill at incendium.com]
Sent: Friday, May 01, 2015 12:32 PM
To: Dave; detomaso at poca.com
Subject: Re: [DeTomaso] Studs and stretching question
What ? Not going to share ?
Cheers,
Bill Moore
Incendium Supply
Calgary
-------- Original message --------
From: Dave <dave at damardirect.com<mailto:dave at damardirect.com>>
Date: 2015-05-01 9:54 AM (GMT-07:00)
To: detomaso at poca.com<mailto:detomaso at poca.com>
Subject: Re: [DeTomaso] Studs and stretching question
Never mind, found a good article.
Thanks
IndyDave
From: Dave
Sent: Friday, May 01, 2015 9:42 AM
To: 'detomaso at poca.com'
Subject: Studs and stretching question
A couple of years ago there was a discussion of the stud bolts (on rotors) stretching when torqued. Can someone tell me the technical term for the stretching please?
Thank you.
IndyDave
Never mind, found a good article.
Thanks
IndyDave
From: Dave
Sent: Friday, May 01, 2015 9:42 AM
To: 'detomaso at poca.com'
Subject: Studs and stretching question
A couple of years ago there was a discussion of the stud bolts (on
rotors) stretching when torqued. Can someone tell me the technical term
for the stretching please?
Thank you.
IndyDave
_______________________________________________
Detomaso Forum Managed by POCA
Posted emails must not exceed 1.5 Megabytes
DeTomaso mailing list
DeTomaso at poca.com<mailto:DeTomaso at poca.com>
http://poca.com/mailman/listinfo/detomaso_poca.com
To manage your subscription (change email address, unsubscribe, etc.) use the links above.
-------------- next part --------------
I am sorry. I did not think that direction. I got into a conversation
about studs and remembered something about stretching, hence my
question.
Here you go (be sure to read the entire article, quiz tomorrow)
IndyDave
"Bolts are normally tightened by applying torque to the head or nut,
which causes bolt to stretch. The stretching results in bolt tension,
known as preload, which is the force that holds a joint together.
Torque meter can be used to measure bolt tension. High preload tension
helps to keep bolts tight, increases the strength of a joint, and
generates friction between parts to resist shear and improves the
fatigue resistance of bolted connections.
Bolt Tensioning
A bolt and nut are designed to act together as the internal threaded
fastener (nut) is tightened onto the externally threaded fastener
(bolt). The bolt is forced to stretch and elongate. This
stretching/elongation is maintained by the head of the bolt and the nut
on the joint thereby maintaining the joint at the desired tension (Bolt
tensioning).
As a rule, the joint will have been designed with sufficient fastener
to apply the required clamp load at 65% of the fastener proof load
stress figure i.e. well below the fastener's yield point.
Yield point or yield strength
It is defined as the load that is necessary to stretch the fastener to
the point where, after the load is removed, the bolt will not return to
its original or previous length. It has moved from being elastic to
plastic behavior.
In order for the fastener to incur a longer length part of bolt donates
material. This will come from the threads, which are the weakest part
of the bolt. A section of the threaded portion of the bolt wall suffers
a reduction of area and will "neck out", creating a "dog bone"
appearance. The change in stress area makes the bolt considerably
weaker and as the bolt is stretched even further the clamping load
decreases. Additional stretching (caused by operator attempting to
retighten the joint and fastener) will cause the bolt to break at its
tensile point.
Clamp load
To produce clamp load, the fastener must be placed in tension. If the
fastener is not stretched then there is no clamping load. Once the bolt
is clamped and firmly seated in the joint bolt tension now results from
the turning of the nut along the threads of the bolts. The bolts start
to stretch elastically, proportional to the amount of nut advancement.
As the nut is further turned the threads of the bolt and nut are forced
together under enormous pressure generating friction between the mating
threads and also causing tensional twisting to the body of the bolt
between the clamped surfaces. The bolt is experiencing two forces
simultaneously, tension and torsion.
In a bolted connection, the bolt must be stretched sufficiently to
produce static preload upon the connection that is greater than the
expected external load rather than the joint assembly acting upon the
bolt themselves. These external loads must be known so that the proper
grade, size, diameter, thread pitch and number of fasteners can be
chosen to create a safe joint or fastening.
When selecting the proper grade of fastener, proof load is the most
important physical property of the fastener. Proof load is the maximum
safe load that can be applied to a fastener without inducing permanent
deformation, as with yield. Tensile strength is the point at which the
fastener will break. The fastener must be stretched far enough to
produce a pre-determined amount of safe preload to the assembly without
causing any permanent damage to the fastener."
[1]http://www.industrialaids.com/upload/Summary_of_Bolt_Tensioning.pdf
From: Bill Moore [mailto:bill at incendium.com]
Sent: Friday, May 01, 2015 12:32 PM
To: Dave; detomaso at poca.com
Subject: Re: [DeTomaso] Studs and stretching question
What ? Not going to share ?
Cheers,
Bill Moore
Incendium Supply
Calgary
-------- Original message --------
From: Dave <[2]dave at damardirect.com>
Date: 2015-05-01 9:54 AM (GMT-07:00)
To: [3]detomaso at poca.com
Subject: Re: [DeTomaso] Studs and stretching question
Never mind, found a good article.
Thanks
IndyDave
From: Dave
Sent: Friday, May 01, 2015 9:42 AM
To: 'detomaso at poca.com'
Subject: Studs and stretching question
A couple of years ago there was a discussion of the stud bolts (on
rotors) stretching when torqued. Can someone tell me the technical term
for the stretching please?
Thank you.
IndyDave
Never mind, found a good article.
Thanks
IndyDave
From: Dave
Sent: Friday, May 01, 2015 9:42 AM
To: 'detomaso at poca.com'
Subject: Studs and stretching question
A couple of years ago there was a discussion of the stud bolts (on
rotors) stretching when torqued. Can someone tell me the technical
term
for the stretching please?
Thank you.
IndyDave
_______________________________________________
Detomaso Forum Managed by POCA
Posted emails must not exceed 1.5 Megabytes
DeTomaso mailing list
[4]DeTomaso at poca.com
[5]http://poca.com/mailman/listinfo/detomaso_poca.com
To manage your subscription (change email address, unsubscribe, etc.)
use the links above.
References
1. http://www.industrialaids.com/upload/Summary_of_Bolt_Tensioning.pdf
2. mailto:dave at damardirect.com
3. mailto:detomaso at poca.com
4. mailto:DeTomaso at poca.com
5. http://poca.com/mailman/listinfo/detomaso_poca.com
More information about the DeTomaso
mailing list