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Using result of analysis in the next load step
 
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abdullah.al.amin
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Joined: 23 Oct 2014
Posts: 12

PostPosted: Tue Oct 28, 2014 2:32 pm  Reply with quote

Hello Everyone,

I am trying to solve a multiple load step problem where result of the previous load step becomes the initial condition of the next load step. I had to use birth and death technique for my analysis. But I don't get meaningful result. It is similar to the one if I apply all the loads all at once and solve it.

As LSWRITE can not be used and I had to use SOLVE one by one because of EKILL and EALIVE command, I can not figure out how to do it. Even when I try to choose the result from .rst file by going to General Postproc->Read Results->By Pick only the last step is available. Pasted below is part of my code.

I hope your valuable suggestion will help me solve the problem.

!First load step

ANTYPE

TIME,1
NLGEOM, ON
NROPT, FULL
ASEL, ....
ESLA
EKILL, ALL

!Apply load and displacement

.....
.....

ALSEL, ALL

SAVE
SOLVE

!Second load step

TIME,2

ASEL, ....
ESLA
EKILL, ALL

!Apply load and displacement

.....
.....

ALSEL, ALL

SAVE
SOLVE


Regards,
Abdullah Al Amin
Graduate Research Assistant
Case Western Reserve University
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saad.bin.aziz
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Joined: 28 Aug 2014
Posts: 19

PostPosted: Tue Oct 28, 2014 3:07 pm  Reply with quote

Dear Mr. Amin,

I am a new user in ANSYS APDL.

However, I looked at your code. I have two suggestions-

1. The syntax "alsel,all" is incorrect, it should be "allsel,all".

2. Before applying the load at different time step are you choosing the
alive element by EALIVE command? Make sure you choose the live element by
EALIVE command and apply load on them.

Thanks
Saad Aziz
Grad Student, ME Dept
Louisiana State University

On Tue, Oct 28, 2014 at 4:32 PM, abdullah.al.amin <aaa196@case.edu> wrote:

Quote:
Hello Everyone,

I am trying to solve a multiple load step problem where result of the
previous load step becomes the initial condition of the next load step. I
had to use birth and death technique for my analysis. But I don't get
meaningful result. It is similar to the one if I apply all the loads all at
once and solve it.

As LSWRITE can not be used and I had to use SOLVE one by one because of
EKILL and EALIVE command, I can not figure out how to do it. Even when I
try to choose the result from .rst file by going to General Postproc->Read
Results->By Pick only the last step is available. Pasted below is part of
my code.

I hope your valuable suggestion will help me solve the problem.

!First load step

ANTYPE

TIME,1
NLGEOM, ON
NROPT, FULL
ASEL, ....
ESLA
EKILL, ALL

!Apply load and displacement

.....
.....

ALSEL, ALL

SAVE
SOLVE

!Second load step

TIME,2

ASEL, ....
ESLA
EKILL, ALL

!Apply load and displacement

.....
.....

ALSEL, ALL

SAVE
SOLVE


Regards,
Abdullah Al Amin
Graduate Research Assistant
Case Western Reserve University






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abdullah.al.amin
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Joined: 23 Oct 2014
Posts: 12

PostPosted: Tue Oct 28, 2014 4:28 pm  Reply with quote

Dear Mr. Aziz,

Thanks for your quick reply.

1. You are right. ALSEL is a typo, I am sorry that it created confusion. In my code I am using ALLSEL

2. I am using EALIVE when necessary.

My concern is, the result is not being saved at every time step and transferring to next time step as it would if I were using LSWRITE..

Thanks for your response again


Abdullah Al Amin
GRA, Case Western Reserve University
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saad.bin.aziz
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Joined: 28 Aug 2014
Posts: 19

PostPosted: Tue Oct 28, 2014 4:49 pm  Reply with quote

Dear Mr. Amin,

Can you create a *Do loop and save your result time stepwise and then solve
all steps of the result together?

You can give me a call if you want to discuss more with me. I will try to
help you though I am not an expert user.My cell number is 225-287-0483.

Thanks
Saad Aziz
PhD Student
Grad Student, LSU

On Tue, Oct 28, 2014 at 6:28 PM, abdullah.al.amin <aaa196@case.edu> wrote:

Quote:
Dear Mr. Aziz,

Thanks for your quick reply.

1. You are right. ALSEL is a typo, I am sorry that it created confusion.
In my code I am using ALLSEL

2. I am using EALIVE when necessary.

My concern is, the result is not being saved at every time step and
transferring to next time step as it would if I were using LSWRITE..

Thanks for your response again


Abdullah Al Amin
GRA, Case Western Reserve University






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Martin Liddle
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Posts: 1274
Location: Chesterfield, UK

PostPosted: Tue Oct 28, 2014 5:38 pm  Reply with quote

On 28/10/2014 23:28, abdullah.al.amin wrote:
Quote:

1. You are right. ALSEL is a typo, I am sorry that it created confusion. In my code I am using ALLSEL

2. I am using EALIVE when necessary.

My concern is, the result is not being saved at every time step and transferring to next time step as it would if I were using LSWRITE..

At the point where your code has the comment "apply loads and
displacements" are you staying within the solution module or are you
going into the preprocessor and then back into to the solution module?
Ideally you want to stay within the solution module otherwise you will
have to use restarts.


--
Martin Liddle, Tynemouth Computer Services,
Chesterfield, Derbyshire, UK.
www.tynecomp.co.uk
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abdullah.al.amin
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Joined: 23 Oct 2014
Posts: 12

PostPosted: Tue Oct 28, 2014 6:59 pm  Reply with quote

Hello Mr. Liddle,

Good catch!

I was solving the each time step and going to the 'Post Process' from the GUI to check if the solution spit out reasonable result. So, when I came back to solve for the next time step, it all started from the beginning. :)

Thanks so much for the help.

Abdullah Al Amin
GRA
Case Western Reserve University


Martin Liddle wrote:
On 28/10/2014 23:28, abdullah.al.amin wrote:
Quote:

1. You are right. ALSEL is a typo, I am sorry that it created confusion. In my code I am using ALLSEL

2. I am using EALIVE when necessary.

My concern is, the result is not being saved at every time step and transferring to next time step as it would if I were using LSWRITE..

At the point where your code has the comment "apply loads and
displacements" are you staying within the solution module or are you
going into the preprocessor and then back into to the solution module?
Ideally you want to stay within the solution module otherwise you will
have to use restarts.


--
Martin Liddle, Tynemouth Computer Services,
Chesterfield, Derbyshire, UK.
www.tynecomp.co.uk
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abdullah.al.amin
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Joined: 23 Oct 2014
Posts: 12

PostPosted: Tue Oct 28, 2014 7:02 pm  Reply with quote

Dear Mr. Aziz,

Thanks for trying to help me out. I solved the problem according to Mr. Liddle's suggestion.

We should keep in touch with each other. Do you have any social network account? (linkedin, researchgate, academia, facebook twitter?)

Abdullah-Al-Amin
GRA
Case Western Reserve University

saad.bin.aziz wrote:
Dear Mr. Amin,

Can you create a *Do loop and save your result time stepwise and then solve
all steps of the result together?

You can give me a call if you want to discuss more with me. I will try to
help you though I am not an expert user.My cell number is 225-287-0483.

Thanks
Saad Aziz
PhD Student
Grad Student, LSU

On Tue, Oct 28, 2014 at 6:28 PM, abdullah.al.amin <aaa196@case.edu> wrote:

Quote:
Dear Mr. Aziz,

Thanks for your quick reply.

1. You are right. ALSEL is a typo, I am sorry that it created confusion.
In my code I am using ALLSEL

2. I am using EALIVE when necessary.

My concern is, the result is not being saved at every time step and
transferring to next time step as it would if I were using LSWRITE..

Thanks for your response again


Abdullah Al Amin
GRA, Case Western Reserve University






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| The Online Community for users of ANSYS, Inc. Software |
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| Send administrative requests to xansys-mod@tynecomp.co.uk |
+-------------------------------------------------------------+

+-------------------------------------------------------------+
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| The Online Community for users of ANSYS, Inc. Software |
| Hosted by PADT - www.padtinc.com |
| Send administrative requests to xansys-mod@tynecomp.co.uk |
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saad.bin.aziz
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Joined: 28 Aug 2014
Posts: 19

PostPosted: Wed Oct 29, 2014 7:23 am  Reply with quote

Dear Mr. Amin,

Good to know that you have solved your problem.

I do have account in social network(Linkedin,facebook). You can find me
there.

Regards,

Saad Aziz
PhD Student
ME Dept, Louisiana State University
BUET, ME 01

On Tue, Oct 28, 2014 at 9:02 PM, abdullah.al.amin <aaa196@case.edu> wrote:

Quote:
Dear Mr. Aziz,

Thanks for trying to help me out. I solved the problem according to Mr.
Liddle's suggestion.

We should keep in touch with each other. Do you have any social network
account? (linkedin, researchgate, academia, facebook twitter?)

Abdullah-Al-Amin
GRA
Case Western Reserve University


saad.bin.aziz wrote:
Quote:
Dear Mr. Amin,

Can you create a *Do loop and save your result time stepwise and then
solve
Quote:
all steps of the result together?

You can give me a call if you want to discuss more with me. I will try to
help you though I am not an expert user.My cell number is 225-287-0483.

Thanks
Saad Aziz
PhD Student
Grad Student, LSU

On Tue, Oct 28, 2014 at 6:28 PM, abdullah.al.amin <aaa196@case.edu>
wrote:
Quote:


Quote:
Dear Mr. Aziz,

Thanks for your quick reply.

1. You are right. ALSEL is a typo, I am sorry that it created
confusion.
Quote:
Quote:
In my code I am using ALLSEL

2. I am using EALIVE when necessary.

My concern is, the result is not being saved at every time step and
transferring to next time step as it would if I were using LSWRITE..

Thanks for your response again


Abdullah Al Amin
GRA, Case Western Reserve University






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| The Online Community for users of ANSYS, Inc. Software |
| Hosted by PADT - www.padtinc.com |
| Send administrative requests to xansys-mod@tynecomp.co.uk |
+-------------------------------------------------------------+


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hassan.jishi
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Joined: 19 Oct 2014
Posts: 4

PostPosted: Thu Oct 30, 2014 9:01 am  Reply with quote

Dear Abdullah,

Could you kindly share a sample of the code implemented in killing elements within the solution part. I am trying to do a similar thing.

Thank you
Hassan Jishi
Khalifa University
Abu Dhabi UAE
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abdullah.al.amin
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Joined: 23 Oct 2014
Posts: 12

PostPosted: Thu Oct 30, 2014 9:14 am  Reply with quote

Hello Jishi,

Killing the element is really simple. But you need to keep in mind the following things.

1. Turn on non-linear analysis using the following code
NROPT, FULL
NLGEOM, ON (whether or not you are trying to solve large deflections)

2. Select appropriate elements.Using asel, esla etc...

EKILL, ALL (kill all selected elements)

3. Before running the solution select desired dead/alive element together

ALLSEL, ALL (to select all elements)

part of your code will look like

NROPT, FULL
NLGEOM, ON ! Optional
ASEL, S, , , 5, 7 ! select area 5, 6 and 7 altogether
ESLA ! select elements that are attached to the areas 5,6 and 7
EKILL, ALL ! kill all elements that are currently selected
ALLSEL, ALL ! select all active and inactive elements (depends on your analysis type)

SAVE
SOLVE


Let me know if this clears your confusion.

Abdullah Al Amin
GRA
Case Western Reserve University


hassan.jishi wrote:
Dear Abdullah,

Could you kindly share a sample of the code implemented in killing elements within the solution part. I am trying to do a similar thing.

Thank you
Hassan Jishi
Khalifa University
Abu Dhabi UAE
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hassan.jishi
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Joined: 19 Oct 2014
Posts: 4

PostPosted: Fri Oct 31, 2014 9:43 pm  Reply with quote

Dear Abdullah,

I tried it and it works. Thanks for the help.

Would it be possible to take it one step further and kill elements while increasing the load. Basically, in the simplified version of my model I am axially compressing a solid rod by applying a displacement on the top surface, here is what i tried to input into ansys without success:

/SOLU
ASEL,S,LOC,Y,0
DA,ALL,ALL,0
NROPT,FULL,,ON
*DIM,DISPLACEMENT,TABLE,8
DISPLACEMENT(1,1)=0,-0.1,-0.2,-0.3,-0.4,-0.5,-0.6,-0.7 !DISPLACEMENT VALUES
DISPLACEMENT(1,0)=1E-6,1,2,3,4,5,6,7 !TIME VALUES
DISPLACEMENT(0,1)=1
TM_START = 1E-6
TM_END=15
TM_INCR=1
*DO,TM,TM_START,TM_END,TM_INCR
TIME=TM
ASEL,S,LOC,Y,C_HEIGHT+2*FS_THICKNESS
DA,ALL,UY,DISPLACEMENT(TM)
ALLSEL,ALL
SOLVE
/POST1
ETABLE,Y_STRAIN ,EPEL,Y
ESEL,S,ETAB,Y_STRAIN,-0.037843
/SOLU
EKILL,ALL
ESEL,ALL
SOLVE
*ENDDO

Thank you
Hassan Jishi
Khalifa University
Abu Dhabi, UAE
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Martin Liddle
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Joined: 15 Aug 2008
Posts: 1274
Location: Chesterfield, UK

PostPosted: Sat Nov 01, 2014 1:32 am  Reply with quote

On 01/11/2014 04:43, hassan.jishi wrote:

Quote:

SOLVE
/POST1
ETABLE,Y_STRAIN ,EPEL,Y
ESEL,S,ETAB,Y_STRAIN,-0.037843
/SOLU
EKILL,ALL

That clearly will not work as you are leaving the solution module and
then returning to it without a restart. Without a restart the solution
will start gain from scratch each time you enter solution. I suggest
you will find the older single frame restart easier for this sort of
application (compared to the more modern muti-frame restart). Try
reading section 3.1 Singleframe restart in the Feature Archive manual of
the ANSYS documentation.

--
Martin Liddle, Tynemouth Computer Services,
Chesterfield, Derbyshire, UK.
www.tynecomp.co.uk
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hassan.jishi
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Joined: 19 Oct 2014
Posts: 4

PostPosted: Sun Nov 02, 2014 11:20 am  Reply with quote

Dear Martin,

Thanks for clearing that up.

I did go over section 3.1 and implemented the sample restart input listing into my input file. Initially ANSYS kept returning an error regarding multiframe restart but managed to figure out how to switch from multiframe restart to the singleframe restart from an old post from david.gross.

It seems to be working now.

Thank you
Hassan Jishi
Khalifa University
Abu Dhabi, UAE
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hassan.jishi
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Joined: 19 Oct 2014
Posts: 4

PostPosted: Mon Nov 03, 2014 12:50 am  Reply with quote

The single frame restart is working fine, however, the data for the first load step are not available after the restart. How can I retain the data, I have listed sample input currently used below. Another thing, if I want to continue further with the displacement load, is there another way to perform this instead of the current method utilized below.

/SOLU
NROPT, FULL, , ON
NSUBST,50,50,50
DISPLACEMENT = -1.0
NSEL,S,LOC,Y,40
D,ALL,UY,DISPLACEMENT
ALLSEL,ALL
SOLVE
FINISH
SAVE

!CLOSE THE PROGRAM. GO THE DIRECTORY AND MOVE ALL FILES !INTO AN EMPTY FOLDER. COPY THE *.DB FILE AND *.ESAV , and
!.EMAT (I DIDNT HAVE AND EMAT FILE) INTO THE CURRENT DIRECTORY !AND CONTINUE BELOW.

/FILNAME,FILE
RESUME,FILE,DB
/POST1
ETABLE,Y_STRAIN ,EPEL,Y
ESEL,S,ETAB,Y_STRAIN,-3,-0.0258
/SOLU
ANTYPE,,REST
EKILL,ALL
ESEL,ALL
DCUM,ADD
NSEL,S,LOC,Y,40
D,ALL,UY,-0.5
ALLSEL,ALL
SOLVE
FINISH

Thank you
Hassan Jishi
PhD/TA, Khalifa University
Abu Dhabi, UAE
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danbohlen
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Joined: 18 Aug 2008
Posts: 951
Location: Evendale OH

PostPosted: Mon Nov 03, 2014 6:23 am  Reply with quote

Glad to hear we are not the only luddites still using single frame.

I've been working with multiframe some the year and it is a royal pain as far as file handling and being intuitive. I think our pleas in the desert may have been heard by the Ansys gods on this topic...

-----Original Message-----
From: Xansys [mailto:xansys-bounces@xansys.org] On Behalf Of Martin Liddle
Sent: Saturday, November 01, 2014 4:33 AM
To: xansys@xansys.org
Subject: Re: [Xansys] Using result of analysis in the next load step

On 01/11/2014 04:43, hassan.jishi wrote:

Quote:

SOLVE
/POST1
ETABLE,Y_STRAIN ,EPEL,Y
ESEL,S,ETAB,Y_STRAIN,-0.037843
/SOLU
EKILL,ALL

That clearly will not work as you are leaving the solution module and then returning to it without a restart. Without a restart the solution will start gain from scratch each time you enter solution. I suggest you will find the older single frame restart easier for this sort of application (compared to the more modern muti-frame restart). Try reading section 3.1 Singleframe restart in the Feature Archive manual of the ANSYS documentation.

--
Martin Liddle, Tynemouth Computer Services, Chesterfield, Derbyshire, UK.
www.tynecomp.co.uk
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