Viewing Explicit Quasi-static Analysis Result

[jae.kang]

I am having trouble viewing the result of an explicit quasi-static model. 

This model has following parameters:

Under Quasi-Static Setup 1 --> Edit

  - Duration= 1 sec

   - Number of Timestep = 2 (Time Step = 0.5sec)

Loads:

  - pressure applied on top, ramping up from 0 to 0.5 sec and remains still until 1 sec

  - pressure applied on side,  ramping up from 0.5 sec to 1 sec.

Analysis Options:

  - Explicit Quasi-Static Step, Number of Steps to 2.

When I run the analysis , the result only shows up to 0.5 second instead of 1 second. However, the output file shows that the analysis is complete to 1 second. 

Why is Nastran only showing result up to 0.5 sec instead of 1 second?

The attached is the model and .txt version of out and nas files.

PS I played around with Number of Steps and Number of Timesteps, and it seems like the result only shows up to the first increment based on Number of Steps. For example, if I set Number of Steps to 3 with total duration of 1 second, the result only shows up to 0.333 sec. How can I view the result for total duration?

[Roelof.Feijen]

Hello @jae.kang ,

According to the help the Explicit Quasi-Static Step value specifies the number of steps to use to solve an automatic quasi-static procedure. If all the loads are applied in a single linear ramp, only one step is needed. If the amplitude functions that define the loading are not linear, enough step should be taken to follow the variation in the loading. Use the minimum number of steps possible to keep the computational run time down.

So keep that setting to 1.

In your case you can keep the number of time steps 2. This should give you a total of 3 values.

At 0 sec, 0.5 sec and 1 sec.

Hopefully the video below explains it better.

[jae.kang]

@Roelof.Feijen 

Thank you very much for the detailed reply. The video really helps. 

For my analysis, I have two ramp loads, pressure applied on top ramping up from 0 to .5 second, and pressure applied on side from 0.5 to 1 second. And I would like to see them applied at the different time in the result (ie. pressure on top applied first and then pressure on side). Therefore I think it makes sense to keep the Number of Steps as 2.

I find the first analysis in your video very interesting. It seems like you have not changed any parameters (kept Number of Steps at 2) and ran the analysis, and got result up to 1 second, which I want. In my Nastran Inventor, the result only shows up until 0.5 second.  If I increase Number of Steps, I only get the result of the first step (ie. Number of Steps = 3 --> result shows up to 0.33 second ; Number of Steps = 4 --> result shows up to 0.25 second). I feel like there is a setting that I an not aware of to show result for entire duration. 

[Roelof.Feijen]

Hello @jae.kang ,

Keep the Number of Steps 2, but increase the number of Time Steps. I think 2 Time Steps is just not enough.

I also adjusted the loads in your model to see the displacement results in a better scale.

First you will see compression, secondly you will see bending.

[jae.kang]

@Roelof.Feijen 

Thank you for the suggestions. 

Unfortunately, I followed all the settings you suggested, but my Nastran is still returning result only up to 0.5 second. Good thing is that it is displaying the result of the first half correctly, with 100MPa applied on top. I think there is a problem with writing output. I think either I am missing a setting, or it is a bug particular to Nastran installed on my PC. I will try to reinstall Nastran and see if the problem disappear. 

I attached the ipt, fno, out and nas file in case anyone wants to take a look.

[Roelof.Feijen · Accepted solution]

Hello @jae.kang ,

I compared the nas files from myself en yours. According to your nas file your files are stored on an M-drive.

Is this a local drive or a network drive.

If it's a network drive copy your model to a folder on your local drive and see if that helps.

According to your out file you are running an older version of the solver.

Please install the update 2 of Inventor Nastran 2021

Below a picture of my Nastran version

Hope this helps.

[jae.kang]

@Roelof.Feijen 

Thank you for sharing your Nastran version. I will post an update once I get an analysis done with the updated version.

[jae.kang · Accepted solution]

@Roelof.Feijen 

Updating Nastran resolved the issue! Thank you for your continuous support Roelof!