pressure on the plate-FEAP code and data

[nshomali]

Dear all,
Hi,
I have a question. May I ask you please to help me to find a solution. Thanks.
I have a circular plate specimen. It is fixed in front of the tube with screws and the dynamic loading act on it. The plate specimen can not rotate or move. It is fixed. I recorded the pressure profile by means of the piezo elect. sensors, which are placed around the tube and near the specimen. I attached the pressure profile as a function of time here. As you can see here in Picture-3, we study only one-quarter of the specimen because of symmetry. I attached Picture-3, and we can see all of the boundary conditions on it. Loading in the x_3 direction axis perpendicular to the plate is shown by the "+" sign. Furthermore, the clamping surface is shown by Hatching in this picture. By the pressure profile in my experiment, which is recorded, we see a plastic deformation of the center of the plate. I am writing a code to illustrate this deformation by means of FEAP. I attached this code by this email (=I3dsh). It doesn't work and I checked many times the BC and all of the parts. Unfortunately I could not find my mistake jet. May I ask you please, to check it and help me to correct that to achieve the result?
In this code, I didn't give my recorded pressure profile. Here, only one puls loading is given.


best wishes,
Sh.Shomali

[Prof. R.L. Taylor]

The attached file now fixes all the radial displacements at r1 and r2 -- when you generate with the block command you are getting parabolas not circles, thus you need to increase the search for nodes using the gap command on the cbou commands

If you now use your pressure profile as the proportional load you will get the solution for elastic behavior.  then you need to change the element to small displacement to get plastic as the finite shell does not have any plastic model.

Your pressure data should be records of
t1 p1
t2 p2
etc.

Then replace the current prop load by

batch
  prop
end
2
t1 p1
t2 p2
....

or you can use an include file for the t/p data sets

[nshomali]

Dear Prof. Taylor,
thanks a lot for your valuable guidance.
I want to achieve a plot form my problem. There is not any error but it doesn't lead to a result.

best regards

[nshomali]

Now I wrote a new code, which I think it should work. I attached it in this reply: Idisk_2b.
Here I used only a concentrated force at the center of the plate. But I don't know how can I call my pressure profile. COuld you please help me to run it? thinks alot.

best wishes,
Shomali

[Prof. R.L. Taylor]

You need to post the data from  your pressure profile so we can see how it is collected in digital form.

You cannot use a single nodal load once the pressure is available.

[nshomali]

Dear Prof. Taylor,
thanks for your reply. I attached my data here as file test.txt .
The first column is time (in seconds). It starts from 1.05849 s and finishes at 1.07s. the recorder records each microsecond the pressure value.
The second column illustrates the pressure in bar.
They are acting on the plate.

best regrads,
shomali

[Prof. R.L. Taylor]

You have not collected the data with enough precision on the time.  There are multiple records with the same time.  Thus, there is no way to convert this to be used by feap as a pressure load.

Also, the data is collected with "," as the decimal point, feap always uses "." - this just requires replacing the "," with a "." so is not a problem.

Once then you can include in the data file by adding the commands (after the end of mesh input) a batch statement
BATCh
    PROP
END
  2
include file_name

where "file_name" is the data set with your pressure load.

You should talk with your professor or colleague about the solution of transient problems to get more help.  It is very difficult for the feap forum to give you more support when not knowing important details about the needed comparison between experiment and analysis.