# Solidwork Bolt Connector Problem

Question asked by Jasper Liu on Mar 26, 2018
Latest reply on Apr 16, 2018 by S. Y.

Hi everyone,

I started to study solidwork bolt connector and its applications recently. However, there are some doubts that I could not figure out by finding answers online by myself. I appreciate if anyone can offer me little bit help here. Please see below as my question:

1. No penetration contact: What is the function of "Friction Coefficient" under the no penetration contact properties? Imagine there is a clamp on a tube. The bolt holes on the clamp provides the clamp force or fiction to avoid the tube from slidding. In solidwork simulation, regardless of whether I check the friction option and input the friction coefficient, I get nearly 0 displacement for the tube or clamp. This would not make sense as if we did not check the friction option, friction is 0, thus the tube should slip from the clamp.

In solidworks, is there a way to test if the bolt will loose or the tube will slide away due to insufficient of friction?

2. Pretension of bolt connector: I am confused about how much torque i should put in the pretension of bolt connector. Apparently we can get this valve by either hand calculation or just grabbing it from website by googling standard bolt torque. We know that for different bolt (Grade 8.8 and grade 10.9 for example)(But size are all M8), they have different standard bolt pretension even they share same properties apart from yield strength. (I know the pretension is a function of yield strength.). Please see my confusion below:

Lets still take the clamp and tube scenario for example. if the we use M8 (Grade 8.8), standard torque to tighten the bolt is around 25 N.M. If we use Grade 10.9, the standard torque will be around 36N.M. Apparently the latter will provide more clamping force. However, they perform the same function or serve the same purpose here which is to provide the clamp force to the clamp. If 25N.M is already enough for this purpose, can we use grade 10.9 bolts with a torque as 25N.M? I check some online videos, it seems that the torque they put as pretension is pretty random. They put 500 N preload (Axial) for a M16 bolt and the result indicates that the bolt passes under the safety factor of 2. However, I would seriously doubt that if they put the standard pretension which is 213 N.M or around 72570N in axial. The plate beneath the bolt will definitely failed (because of too much axial load).

Thank you very much for everyone's help!