displacement and load

[albert1981]

Dear all,

I put a field of displacements to a shell plate. Now I'm trying to put an external load to the same plate mantaining the displacements. The problem is that abaqus seems not see the last load applied.
I tried also to add it in the input file by hand but the results are quiete wird.

The only solution that I can see is to put the load and then see the displacements results so I can add all the displacements due from the load with that one that I put as input. But the procedure is quiete long.

Do you know other way?

Thanks,
Albert

 

[johnhors]

Albert

I find your description difficult to follow.

Is your field of displacemnts applied to the entire plate?

If yes, then any applied load would be ignored.

If no but your load is still applied within the field of displacements then again it will be ignored.

An applied displacement is a fixation (or support), loads cannot be applied to a support.

I apologise if I've completely misunderstood your post.

 

[corus]

I think albert is trying to add two seperate load cases, although in a confusing way. If you run once case with applied displacements and then a second case with just a load, then you can just combine the two results in Viewer for an elastic problem.

corus

 

[johnhors]

Corus,

Sorry, but that doesn't make any sense to me either !

Applied displacements represent boundary condition restraints that will not be present in a load only case, so I can not see how it would be valid to combine the two, as it is not like combining different load only cases.

 

[albert1981]

Hallo,

Sorry if I not explain myself enough clearly. The displacement are applied to the entire plate so johnhors you are right in your first post. I cannot apply displacements and load to the same element is that right?
And Cours you right as well but what I wanted to do is to compare the case you mentionaed with a case with one step simulation where everything is applied at the same time.

Thanks,
Albert1981

 

[johnhors]

Albert,

Yes, you cannot apply displacements and loads to the same NODE, it does not make any sense ! There will be an "equivalent" set of loads which would give you the same displacements you require, this can be obtained from the restraint force reactions. Thus applying an additional set of loads on top of the equivalent set of loads will produce different displacements.

 

[corus]

I was implying that the second case of load only didn't include fixed displacements (other than to obtain a solution), and hence the first case of fixed displacements (no applied load) could be added to the second case of applied load (no displacements) to give an overall case of applied load and applied displacement. What this represents in the real world I don't know.

corus

 

[albert1981]

jonhors,
I was trying to give load and displacement to the same elements but to differents nodes. I wanted to apply the external load only the a free edge of the plate while the rest of the plate has a given displacements.

corus,
I'm doing a static elastic analysis so I can do the superimposition of the two separete case(YESdisplacementNOLoad and NOdisplacementYESload). I think physically it will be alright.


thanks you all,
albert1981

 

[gurmeet2003]

I have a question that deals with slight variation of Albert's problem. I applied a displacement on one part in the assembly in the first step. The objective was to bring the parts into proper contact and eliminate rigid body motion. In the second step I applied the load on the same part (at the same reference point as it is a rigid part). ABAQUS seemed to ignore this load. I did not remove the artificial displacement applied during first step in the second step as it's magnitude was very small.
Should I have removed the displacement in the second step at the same time as I applied the load?

Thanks,
Gurmeet

 

[albert1981]

Hallo Gurmeet,

it's seems that you cannot apply at the same element a displacement and a load in the same step. I think that once you apply the displacement in a node that will fix the node at this displacement. like a boundary condition fixed so you cannot moove it further.

Once you applied a displacement you can not do anything else, if anybody know a way to applied load or further stresses to a fixed displacements please let us know.

thanks,
Albert