No compression for spring element in Abaqus

[master101]

Hi,I am trying to simulate ligament as a spring element (wire). But problem is ligament has no compression. How can I apply "no compression" if I design it as a spring or I can make sure that my spring element is not taking any compression. From history output of spring element, it seems that it got some negative reaction (CTF1) force. Does it mean compressive force? If anyone know, please response.

Thanks!!

 

[Mustaine3]

You can use Connector Stop or you define a nonlinear elasticity with high values for certain displacements.

 

[IceBreakerSours]

If you are assuming linear elasticity, then there is an option in the Material selection pop-up menu that CAE offers that says 'No compression' or 'No tension'.

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[master101]

Hi Mustaine3 and IceBreakerSours, thanks to both of you.

To IceBreakerSours: I am defining the spring as "wire feature" which allows me to assign only stiffness constant. For this condition, I don't see any "no compression" option. The one you mentioned, is under Property module which does not give me to assign a material property or section to any wire (spring) element.

To Mustaine3: At present, I am defining with a linear value. Can you please tell me a little bit more how to do with a connector stop or high displacement value? Is it in CAE?

Thanks again and please help me more if possible!

 

[Mustaine3]

You can add these connector behaviors in CAE. It's possible in the Interaction-Module within the connector section definition.

With keywords it's
*Connector Elasticity
*Connector Stop

See Abaqus Users Manual 31.2.1 Connector behavior

 

[IceBreakerSours]

I have a fair amount of experience with ligaments. Why can you not use a truss element for your ligament kinematics? What's so special about a spring element?

Are you new to this forum? If so, please read these FAQ:

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[master101]

To Mustaine3: I solved assuming spring as nonlinear. There are total 4 springs. But output graph shows that all springs displacements are negative though it looks from visualization that 1 or 2 spring is probably extending. Also, surprisingly, for one of spring, when displacement is negative, it gives a small value of CTF.

Any idea why this is happening? Why all springs displacement are negative? Or is this not a problem?

To IceBreakerSours: Hi, I got the bone geometry from CT scan. Since, I have stiffness values in hand, so, I wanted to solve just assuming ligament as a spring. Can you please give some better idea that would be easier?

Thanks to both of you again!