spring pretension

[wja365]

I am searching for a way to pretension non-linear springs. I would like them to have tension in them before I apply my loading step. Does anyone have any ideas as to how I may accomplish this? Thanks.

 

[akabarten]

Hi,

If you use connector element with *CONNECTOR ELASTICITY you can introduce initial tension/compression with *CONNECTOR CONSTITUTIVE REFERENCE keyword.

Regards,
Bartosz

 

[wja365]

Thank you for that suggestion. I have tried to implement it, but the solver appears to be having a problem. I have included the code from the .inp file below. If possible, can you tell me if I am understanding it correctly? This is for a group of 11 wires, the connector type is bushing.

I have tried to set an initial length of 7 mm in the "Y" direction of the coordinate system I was required to make (3rd line in INP file below). Then I defined a non-linear force-displacement table for X, Y and Z directions, with no force exerted when the wire is compressed and bi-linear force-displacement when the wire is in tension. Do I understand this correctly?

The warning I am getting is "Solver problem. Zero pivot when processing D.O.F. 6 of 1 nodes." These nodes are on wire endpoints. Any suggestions on how to get this to work would be appreciated.



INP FILE:
*Connector Behavior, name=ALL_ConnectorSection
*Connector Constitutive Reference
0., 7., 0., 0., 0., 0.
*Connector Elasticity, nonlinear, component=1
0.,-1000.
0., 0.
1., 0.1
2., 0.2
3., 0.3
5., 0.4
7., 0.5
*Connector Elasticity, nonlinear, component=2
0.,-1000.
0., 0.
1., 0.1
2., 0.2
3., 0.3
5., 0.4
7., 0.5
*Connector Elasticity, nonlinear, component=3
0.,-1000.
0., 0.
1., 0.1
2., 0.2
3., 0.3
5., 0.4
7., 0.5

 

[akabarten]

Hi,

Your definition looks ok for me.
The error message is related to rotational degree of freedom.
Bushing connector has all 6DOFs, please try to use characteristic for components 4,5 and 6.
If you do not want to rotation at all just use some high elasticity.

**
*Connector Elasticity, component=4
1.0e+06
*Connector Elasticity, component=5
1.0e+06
*Connector Elasticity, component=6
1.0e+06
**

You can also try to use cartesian connector instead bushing.

Regards,
Bartosz