Advise on using spring elements on compression to test stability. 1

[bgarita]

Hello All,
Between two opposing surfaces I will like to place spring elements in compression to test the stability of one surface upon the other (after some load is applied to one surface). I've been studyng proE and proMechanica to see if I can do this using this software. Has anyone tried something similar?
Thanks.

 

[JStephen]

I'm not sure I understand the question, actually.

 

[bgarita]

Basically I want to model a contact problem. For that purpose I will like to place spring elements in compression between two opposing surfaces. If a moderate load is applied to one of the surfaces, and any spring looses it's compression state then the surfaces are unstable.
Has anyone attempted something similar and is familiar with ProE Wildfire? Can this software model what I am talking about?

 

[johnhors]

Bear in mind that you should only attempt this with the faces meshed with linear shape/displacement function elements (i.e. NO mid side nodes)

Also do the opposing surfaces have matching meshes, to enable spring element creation between corresponding nodes? If not you cannot use spring elements.

How will you determine what spring stiffness to use? If the surface meshes are not regular then you should consider varying the spring stiffness with the surface area of each element face.

Finally be very cautious when using spring elements in this context, strictly speaking spring elements are incompatible with the shape functions of shell/solid elements and should thus be avoided as they will not provide a theoretical perfect interface.

Solvers like Abaqus, Lusas and Marc have developed advanced slideline routines to handle contact problems like this, I don't know about ProE Wildfire.

 

[ProbaSci]

I don't remember the ProE mechanica "add-on" having the ability to add spring elements or contact analysis. The stand alone Mechanica version might. Even if it does, I think you're going to be pushing the limits for Mechanica to do this type of work.

 

[MToft]

Hi,
I don't think ProMechanica can do this directly, especially not if there's significant sliding/friction. In Nastran we wrote macros to create the necessary array of springs (for a slightly different purpose!).

However, the contact pressure might indicate the sort of problem I guess you're looking for, and ProMech should report this from its basic (no friction) contact analysis; 0 or negative pressure indicates loss of contact ("instability"). I agree with ProbaSci it's at the limit of what the software can attempt, and worth checking a simplified version with some quick hand calcs if at all feasible.

Is there a ProMech forum where you could ask this? They might be better at the detail (certainly than me!).

Cheers,
MToft