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# Time Handling and Creep Modelling FEMAP

Hello to all community, i have a big problem with my thesis work.

The work is about the CREEP modelling of a specimen, i want to study its behaviour in time, but i can't understand the logic of the FEMAP time Handling.

When i put the settings for the nonlinear analysis i have the following inputs:

Time Steps

Creep time Increment

What is the meaning of this terms?

To be clear I explain a typical situation:

I set, i.e., "Time Steps = 10" and "Creep T.I.=60", the meaning for me is that the simulation will compute 10 steps of 60s, so the total time of simulation will correspond to 600s. So what i aspect are 10 results, where each of them contain the "Stress (for example)" every 60s.

But is not True, as a result of the simulation i have 260 results and time spacing between 0 to 1 (you can see the results in the attachment).

How can i read this results? What is their meaning?

PieFierro

3 REPLIES

## Re: Time Handling and Creep Modelling FEMAP

I'm not sure we have information, you may need to post the material/creep inputs and the actual NLPARM entry from the .dat file. I would also suggest looking at the F06 file to see what messages are there concerning convergence etc.

This note from the QRG on NLPARM may also help:

3. The unit of DT must be consistent with the unit used on the CREEP entry that
defines the creep characteristics. Total creep time for the subcase is DT multiplied
by the value in the field NINC; i.e., DT*NINC.

Regards,

Joe

## Re: Time Handling and Creep Modelling FEMAP

Hi, thank you for the reply, i don't know what is the NLPARM but actually in the .dat file i have the following settings:

NLPARM 1 1 86400. 5 10 PW +
+ .001 .001 1.-7 3 25 4 .2 .5+
+ 5 20.

I don't understand how to handle the time simulation in the Non Linear static analysis, because the results is ever in the interval [0,1] and i can't understand why.

What are the material/creep inputs that did you asked?

Thank you

PieFierro

Solution
Solution
Accepted by topic author PieFierro
‎05-11-2017 04:26 PM

## Re: Time Handling and Creep Modelling FEMAP

I would suggest looking at the Nastran documentation, in particular the QRG under the 2 key inputs for using creep material model. These are the NLPARM and the CREEP entries. You can see how the inputs in Femap get translated to Nastran by looking for both of these entries in the .dat file that Femap writes out. The Nastran documents go into detail about the material model and the various options and inputs. The note I posted earlier points out the importance of consistent units among the various inputs in both locations.

In case you had not noticed, your Femap installation includes all of the Nastran documentation also, just go to Femap Help/NX Nastran and it will open the main pdf index of all of the Nastran documents.

Regards,

Joe