Need Help Modeling Belleville Washer in FEMAP

[Darkmann]

It looks like the only option I have is to use DOF Springs. I created a dimensionless load vs displacement function and applied to the DOF Spring. Then between End A and End B, I apply 3 of these DOF Spring elements, each representing stiffness in the three coordinate directions. Is this the proper way to do this? Do End A and End B have to be coincident? Is there a better way than using DOF Springs? Thanks.

 

[jbrackin]

In general, DOF springs should not be used unless the nodes are coincident, bad things can happen. If your nodes are not coincident, and actually even they are, I would suggest using Spring/Damper element. If you want enter a force/displacement curve, then click on the "nonlinear/freq response" button and you will be able to reference your force/displacement function.

Regards,

Joe

 

[Darkmann]

Thanks Joe. I don't like DOF Springs and always use CBUSH. I didn't see any way to input my load/displacement function. Thanks for giving me a lead.

 

[Darkmann]

Update Joe. In initially the run failed but after I put in an initial value for stiffness in the DOF Spring stiffness window, it ran. Unfortunately the results are not what I expected, and I can fix that later. My question is this: I do not believe I have the non-linear FEMAP module (I'm yet to check on that). So, by invoking the non-linear stiffness, does FEMAP ignore my L-D curve and just use that initial stiffness I provided?

 

[jbrackin]

Use of a load-displacement curve requires a nonlinear(iterative solution) analysis, so you will need a nonlinear license, and will have to use the nonlinear analysis type in the Femap analysis manager.
If you submit a linear analysis, then the nominal stiffness value on the CBUSH entry is used by the Nastran solver.

Regards,

Joe

 

[Darkmann]

That's what I thought. I'll dig into this some more. Thanks Joe.