Abaqus Help - Static PreStress to Explicit Dynamic Transfer 1

[jham046]

Hi all,

I have just recently started using Abaqus CAE 6.12 for a project. The project requires me to model waves in a silicone slab with a prestressed area.

What I need to do is prestress an area of the silicone and then run an explicit dynamic analysis of wave propagation through the slab, with this prestressed area.
Abaqus does not allow a static step followed by a explicit dynamic step in the same model. I want the prestress to be present throughout the entire wave propagation analysis.

I have investigated using the import and restart functions, but as I am new it is difficult to understand them fully, and whether or not they can achieve what I am wanting.

Any help or advice on transferring the prestressed static model to the explicit dynamic analysis would be much appreciated.

Thanks,
James

 

[MechIrl]

You could either do a 'quasi-static' analysis with the explicit solver to apply the pre-stress and then in a second step do the wave propagation analysis. Otherwise you could use the import (not restart) option to bring the stress-state from Standard to Explicit.

 

[jham046]

Hi,

Thanks for your reply. From what I could understand I ran an analysis with just a static step in which I applied the prestress. I then created an exact copy of the model, deleted the static step and replaced it with the dynamic step. I then created a predefined field, using the output from the prestress analysis. I ran this and it performed the simulation, however as soon as the dynamic step began the prestress that was present appeared to decay away rapidly. I need the prestress to be present throughout the entire dynamic wave propagation analysis.

Have I used the right method? And the type of analysis I am trying won't achieve what I want? Or am I missing something?
Also could you explain more how to run a quasi-static analysis?

Thanks for your help, it is much appreciated.

 

[MechIrl]

If you have an elastic material and you do not maintain the loading that caused the pre-stress from the static analysis then that pre-stress will quickly decay in the explicit analysis. Is this the case for you?

To do a quasi-static analysis in explicit you just need to apply your loading/displacement relatively slowly so that the kinetic energy in the solution is a small fraction (<5%) or you internal energy. Depending on your model you may have to do something called mass scaling (check it out in the manual) to artificially increase your stable time increment to reduce computational cost to an acceptable level.