Bushing connectors in Abaqus 1

[Teru1212]

Hello,

I have a question regarding bushing connectors in Abaqus. Can you tell me how do i get the material parameters i need? I have to get the ones in the picture but i dont know what D11-D22 etc. are. Do I have to calculate them with for example the Huth equation? If so,how do I get the parameters for plastic and Damage behaviour? DO I have to calculate them as well? I have rivets out of Titanium Ti-6Al-4v. Are there data sheets for these kinds of rivets?

Thanks for your answers.

 

[GregLocock]

You can either FEA the bushing itself and get estimated rates, or get the bushing tested. I'm assuming D11 etc are just the linear rates in each direction. In my experience modeled rates can be out by 30% easily (particularly in the non linear region), and measured rates can vary by 15% between batches.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[FEA way]

If you can’t perform physical tests (which is typically the case when such questions are asked), you will have to estimate those parameters, possibly from a simulation involving a solid model of the riveted joint. Especially since, from what you said, you need not only elasticity but also plasticity and damage. However, there are other approaches to simplified rivet modeling that you can consider as well. For example, Abaqus also offers so-called mesh-independent fasteners and they can be used to model rivets as well.

 

[Teru1212]

Hello,

Thanks for the answers. Youre right, I cant perform physical tests. Isnt the Busing connector approach the same as the Mesh independent fastener method? I thought Bushing is just the section assignment for the fasteners. If I use the mesh-independent fasteners can I define the damage parameters and plasticity without physical or FE tests? Or are the rivets rigid in that case?

 

[FEA way]

Mesh-independent fasteners can be based on connectors or BEAM MPCs. But their main advantage is the ease of defining.

 

[Teru1212]

I look around a little bit in Abaqus Manual. Is Beam MPC the same as "Rigid MPC" in the fastener property module? (see Image). If so, doesnt that mean the Fastener/Rivet I Created is rigid?

 

[FEA way]

Yes, that "Rigid MPC" option refers to BEAM MPC which is rigid beam connection. But you can use connector section instead.

 

[Teru1212]

Now I understand thanks for your help. One more and hopefully last question so that i know i understood it right: If i use Connector section then I have to somehow get the Damage and plasticity parameters, with another FEA of a solid Rivet or physical tests right?

 

[FEA way]

Yes, or from the literature if you manage to find some research papers fitting your needs. Unfortunately, damage parameters are not easy to obtain since they are specific to Abaqus definition of damage and experiments would be the way to go in most cases.

 

[Teru1212]

Thank you very much, you helped me a lot!

 

[Teru1212]

Hello,

I did a crash test, where i used bushing connectors with damage and plasticity model (The parameters I got from my University). I started the Simulation and everything was fine until 2 hours into the calulation an error appeard. In the status file there is this text:

"

***ERROR: At least one *CONNECTOR ELASTICITY option has been defined such that
the current elastic stiffness is not positive definite. This often
happens when nonlinear elasticity is defined over an insufficient
range of constitutive displacements/rotations. In such cases,
expanding the range on the datalines or using EXTRAPOLATION=LINEAR
will likely resolve the issue. Please check the *CONNECTOR
ELASTICITY definitions for connector with nodes 965 and 368334.
"

What exactly does this mean? And how can I fix it?