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Axial forces in bolts is equal to the Preload applied

I have a simple model bolted joint, I need bolt forces as per VDI2230 standard. As per VDI2230 guidelines model II I designed the model with preload in the bolts and contact interface, I modelled the bolts with PBeam element and requested ELForces at the bolt sets, the axial forces of the bolts is equal to the preload applied.

I did another iteration without preload the axial force differed.

Shouldn't it the case where due to external loads the preload should reduce or increase.

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solon

Hello,

For bolt pretension analysis, followed by service load you can refer to the example below:

https://help.altair.com/hwsolvers/os/topics/solvers/os/contacts_and_pretensioning_bolts_os_example_r.htm?zoom_highlight=bolt

Mintu

Dear Solon,
Is there any chance to

perform a linear analysis instead of non linear,

I have a simple 4 bolted joints modelled as per VDI2230, top two bolts numbering 5000 and 5001 are preload with 2000N and 1500N respectively and did 3 iteration of gravity, a vertical load of 3000N and load add of grav and vertical load (Linear static)

In all three cases my axial force is equal to preload applied.

Where as bolts without pretension show real values.

Is my procedure wrong or should i go with non-linear

solon

Hi,

Could you please share the .fem file as well? It’s difficult to fully assess the setup from the description alone. For accurate results, it would be best to run the analysis as nonlinear

Mintu

I'm using my company software and it would be a bit more complex to provide you with a .fem file.

Could you make a simple model with pretension and working load with ELForce on bolts and provide me.

I performed the pretension as per pretension tutorial.

Mintu

Thank you,

As you said I added an individual pretension case and called it in another subcase(pretens).

It worked the axial force increased.

Till now i have been using pretension with external load now external load +

subcase(pretens).

can you tell me what is the difference between these two cases and for a real life application to run a static or fatigue analysis should i be considering preload in all cases because the stress in the components is larger in pretension case rather than a simple load case without any pretension.

Mintu

@solon

Please can you suggest me anyone whose is good at bolt calculation as per VDI2230 or using FEA tool to calculate the safety factor VDI2230 or how to extract forces for VDI2230 bolt calculations