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Tension ConnectionTension Connection A threaded fastener

connection has clearance gaps

that are used to assemble theconnection.

A connection can be loaded in

either tension/compression or

shear.

Because of the clearance gaps,dowel pins are often used for

accurately positioning of

mating parts.

Shigley, Fig. 8-12

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Proof Load & Proof StressProof Load & Proof Stress

Proof LoadProof Load : Maximum force that a fastener can withstand

without acquiring a permanent set.

Proof StressProof Stress: Proof Load divided by the tensile-stress-area

of the fastener.

The proof stress is slightly less than the yield stress

of the material due to stress concentrations in thethreads.

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Bolt PreloadBolt Preload Purpose of bolt is to clamp

two parts together.

Turning the nut on the

threads will stretch the bolt

to create a clamping force.

The clamping force will

impart a compressive force

on the mating parts.

The clamping force is called

preload or initial tension.

grip

Shigley, Fig. 8-12

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Clamped Part StiffnessClamped Part Stiffness

L1

L2

L3

333

222

111

321m

mi

LEAkLEAk

LEAk

k

1

k

1

k

1

k

1

kF

=

=

=

++=

=

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PressurePressure--Cone EquationsCone Equations

Shigley, Fig. 8-14

( )( )

( )( )

++

++

=

dDdD1.15t

dDdD1.15tln

Ed0.577k

Reference Shigley, page

339-340 for derivation

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External Load InteractionExternal Load Interaction

Preloaded ConnectionPreloaded Connection

Shigley, Fig. 8-12

mb

bb

mb

m

bmb

m

m

b

b

kk

PkP

PPP

k

kPP

k

P

k

P

+

=

+=

=

==

i

mb

mm

i

mb

bb

ibb

Fkk

PkF

Fkk

PkF

FPF

+

=

+

+

=

+=

0Fm