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# Coefficient of friction for bolt loads

## Coefficient of friction for bolt loads

(OP)
Hi, I have a plate which is fixed. and then another plate connected by bolts to the fixed plate. I am trying to calculate the bolt load when there is lateral acceleration to the whole structure (transportation load case). I have used beam elements to model the bolt using spiders. I have also defined contact surfaces. Is it necessary to define "coefficient of friction" to have realistic loads on the bolts? or not? I found unrealistic moments when there is no "coefficient of friction". Please suggest the correct way.

### RE: Coefficient of friction for bolt loads

Hello!,
Not necessary, if you define surface-to-surface contact with no penetration + friction then a portion of transmitted load between plates goes by friction, not by the bolt, then of more conservative to consider frictionless contact, all axial & shear load goes to the bolt.

Friction with contact in general is a trick we use to stabilize the Finite Element model to avoid fatal error due to rigid body movement of a component at the very first moment of starting the analysis when contact elements are not closed, and of course, also when friction plays in the analysis an important role.

Here you have a video & post where I explain the contact between two bolted plates with active contact:
https://iberisa.wordpress.com/2020/09/11/frequency...

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog de FEMAP & NX Nastran: http://iberisa.wordpress.com/

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