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How to specify time step of force in a nonlinear analysis

Altair Forum User

I need to implement non-linear analysis of a McKibben muscle. In the simulation, I have to apply a preload of 5N on the head of hyperelastic material tube and then applying an internal pressure of 0.25 bars that dilates the system.
What command should I use to apply before the force of 5 N and then to also apply the pressure of 0.25 bar? Thank you

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Altair Forum User

Hi @jugerman

Try this:

1) Create a NLSTAT analysis subcase with force 5N which is your preload.

2) Create a linear static subcase with 0.25bar pressure and refer the NLSTAT subcase in STATSUB(PRELOAD) entry in subcase information.

This way the stiffness added in the preload subcase will be included in the static run.

Altair Forum User

i'm working with a NLGEOM... Is possible create a subcase for the preload?

Altair Forum User

Hi,

STATSUB (PRELAOD) is useful to reference linear and Non linear STATIC subcases. So I dont think NLGEOM can work in your case. You can give it a try.

Altair Forum User

Hi,

In my model, I need to apply an initial force of 5N and after a time dt also apply an internal pressure. How do I define these two time intervals, that is how to define this condition:
- FORCE F=5N applied from the time T=0 to T=2
- PRESSURE P=0.25Mpa applied from the time T=1 to T=2