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Re: Bolting issues, generation II

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>Majid wrote:
>Assuming bolt axis is along a-a, shear deformation (exagereted here for 
>the sake of argument) on the bolt can only develop as shown, because
>end rotation of the bolt head and nut is restrained by the plates in
>contact on both sides.
> 
>Now, distance b-b is the bolt grip after inelsatic shear deformation
>takes place. Does not this mean additional elongation along the bolt
>length, i.e extera tension due to shear? So why tension be lost rather
>than increased?
> 
>         _________________
>         |               |
>         |               |
>       a |               | a
>         |               |
>         |               |
>         -----------------
> 
> 
>         |\
>         | \
>       b |  \
>         |   \
>         |    \
>         \     \
>          \     \
>           \     \
>            \     \
>             \     \
>              \     \
>               \     \
>                \     \
>                 \     \
>                  \     \
>                   \    |
>                    \   |
>                     \  | b
>                      \ |
>                       \|

Majid:

A pretensioned bolt is normally stressed into the plastic range during
installation. That is, the bolt stretches a little bit (scientific term)
as the pretension induced is equilibrated as a clamping force on the
joint.

As an externally applied shear load is increased toward bolt shear
failure, inelastic deformations will occur in the bolt shank. These
inelastic deformations initiate when the combined stress due to the
pretension and the externally applied shear load is sufficient to cause
yielding. But as this yielding occurs, the bolt elongates and the
pretension is lost. Subsequently, the failure of the bolt occurs by
rupture just as it would for a bolt that initially had no pretension.

Make any sense?

Charlie