time period in explicit suitable for static problem.

[Chen1]

I want to use abaqus explicit dynamic to solve a static problem, because i could not solve that problem using abaqus standard due to material and contact non-linearity. So i decided to use Abaqus explicit. However as you know the static solution is a long term solution, which means that i need a very long time period in abaqus explicit.

Anybody know how can i overcome that problem?

Thanks.

 

[Chen1]

Any idea?

 

[Simfinite engineering]

You can use either mass or time scaling
They basically come down to the same thing (if nothing is time (strain rate) dependent).
This is just artificially decreasing the time (and amplitudes) or increase the mass.
To check if you then have a quasi-static solution you can check the relation between kinetic and internal energy.

 

[Chen1]

Hello Sdebock. I have two questions?

the first question is about the time scaling factor.

In my model the time period is 5 sec when the time scale factor was 1. Suppose i change this time scale factor to 10 that is equivalent to time period of 50. Correct?

the second question is about the ratio of the kinetic energy to internal energy ratio

what should be that ratio so the analysis is static or quasi-static?

Thanks

 

[Simfinite engineering]

See abaqus user manual 6.3.3 Explicit dynamic analysis -> Computational cost

Reducing the computational cost by speeding up the simulation

To reduce the number of increments required, n, we can speed up the simulation compared to the time of the actual process—that is, we can artificially reduce the time period of the event, T. This will introduce two possible errors. If the simulation speed is increased too much, the increased inertia forces will change the predicted response (in an extreme case the problem will exhibit wave propagation response). The only way to avoid this error is to choose a speed-up that is not too large.

The other error is that some aspects of the problem other than inertia forces—for example, material behavior—may also be rate dependent. In this case the actual time period of the event being modeled cannot be changed.


In a quasi-static analysis it is expedient to reduce the computational cost by either speeding up the simulation or by scaling the mass. In either case the kinetic energy should be monitored to ensure that the ratio of kinetic energy to internal energy does not get too large—typically less than 10%.