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Bolt pretension unit not matching to bolt force unit.

Posted 4 févr. 2023, 14:58 UTC−5 Structural Mechanics Version 6.1 2 Replies

Y Ko
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All unit : Gravitaitoal IPS (on gloabl parameter) Bolt pretension : 1880 lbf Global evaluation, Bolt force : 422.64 lbf I expected that Bolt pretension and bolt force values have to be identical. But then, I changed Bolt force unit on globla evaluation to N, It showed me 1880.0 N. I was very confused with the result. becaue lbf value is the same as N.

So I tried SI unit All unit : SI Bolt pretension : 1880 N Global evaluation, Bolt force : 1880 N I got what I expected.

Am I missing something on here? Would anyone please explain what is happening?

Thank you

2 Replies Last Post 9 févr. 2023, 18:09 UTC−5
Henrik Sönnerlind COMSOL Employee

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Posted: 2 years ago 6 févr. 2023, 05:24 UTC−5

You have spotted an error. The expression defining the bolt force contains an explicit multiplication by 1[N]. This means that it is only correct in unit systems where the force unit is N.

The rest of the solution is correct, it is just the result variables for bolt force (and bolt shear force) that are affected.

The axial bolt force can be unit corrected by evaluating

solid.pblt1.sblt1.F_bolt*1[lbf]/1[N]

In order to get a corrected shear force, you would have to edit the defining expressions in Equation View.

This error will be corrected in version 6.1 update 2, which is due in a couple of months. Thanks for reporting.

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Henrik Sönnerlind
COMSOL
You have spotted an error. The expression defining the bolt force contains an explicit multiplication by 1\[N\]. This means that it is only correct in unit systems where the force unit is N. The rest of the solution is correct, it is just the result variables for bolt force (and bolt shear force) that are affected. The axial bolt force can be unit corrected by evaluating solid.pblt1.sblt1.F_bolt\*1\[lbf\]/1\[N\] In order to get a corrected shear force, you would have to edit the defining expressions in Equation View. This error will be corrected in version 6.1 update 2, which is due in a couple of months. Thanks for reporting.
Y Ko
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Posted: 2 years ago 9 févr. 2023, 18:09 UTC−5

Thank you so much for letting me know.

Thank you so much for letting me know.

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