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Pre-stressed nonlinear transient analysis

Hi,

is there a way to apply a static load before running the nonlinear transient analysis?

I managed to do it in linear solutions by means of the STATSUB card in the CASE, but the STATSUB cannot be used into SOL129 and I cannot use SOL400 because I have external superelements which are not supported by SOL400.

What can I do?

Thank you

9 REPLIES
Solution
Solution
Accepted by topic author Olgola
‎10-02-2015 05:49 AM

Re: Pre-stressed nonlinear transient analysis

You can do this by sequencing your loads. The simple example attached here has a solution running from 0-2 sec. There are two FORCE loads that are ramped up from 0-1 in a linear fashion, then held fixed at a constant magnitude from 1-2. They act as the pre-load. The table to define the force magnitudes looks like:

 

Time             0      1      2

Magnitude     0      1      1

 

It also has a pressure load that is initially zero, then ramps up after the forces reach their steady magnitude. The pressure magnitudes look like:

 

Time             0      1      2

Magnitude     0      0      1

 

Regards,

Mark

 

Mark Lamping

Simulation Product Management

Product Engineering Software

 

Siemens Industry Sector

Siemens Product Lifecycle Management Software Inc.

 

mark.lamping@siemens.com

www.siemens.com/plm

Re: Pre-stressed nonlinear transient analysis

[ Edited ]

Hi,

thank you for your answer.

I understood how to deal with the force, but what if my dynamic loading is a forced base acceleration given using the Large Mass method? The input is given by means of a TLOAD1 card, but it is a sine sweep...should I insert in the table some zero values at the beggining? 

 

Solution
Solution
Accepted by topic author Olgola
‎09-30-2015 05:36 AM

Re: Pre-stressed nonlinear transient analysis

The initial subcase can be made a static preload subcase (no inertia or damping) by setting PARAM, TSTATIC, 1

 

This is described under "Case Control" in section 5.5 of the Basic Nonlinear Analysis User's Guide and in section 5.4 of the Advanced Dynamic Analysis User's Guide:

 

initial conditions could be a part of the nonlinear analysis by applying static analysis for the preload using PARAM, TSTATIC in the first subcase. Then the transient analysis can be performed in the ensuing subcases.

 

sltrn2.dat in the TPL contains examples of this.

 

 

Re: Pre-stressed nonlinear transient analysis

[ Edited ]

That could be exactly what I needed, where can I find the example file you talked about?

I am working on the university computer and I cannot find this TPL you talked about, maybe because nastran is not directly installed on this computer, infact I need the intranet connection to use it. 

 

Also, can I obatin the same result per forming a SOL106 and then restarting it into the SOL129?

Re: Pre-stressed nonlinear transient analysis

In the tpl folder of your NX Nastran installation (i.e. *NXN_BASE%\nxn10p2\nast\tpl)

Re: Pre-stressed nonlinear transient analysis

Just one more question, is it possible to use different MPC sets in the 2 subcases?

 

Re: Pre-stressed nonlinear transient analysis

Hi,

I tried using the TSTATIC param, but it seems it doesn't see the static force I applied in the first subcase, infact it does not write the outputs of the first subcase in the .f06 file, although I asked for SPCFORCES and NLSTRESS (I would expect to see the same results I obatined from the SOL 106 I made for comparison) and the outputs of the second subcase are all 0.0.

 

This is my set up: I am using the same SPC and the same TSTEPNL cards for both subcases, the only difference is in the applied loads (a FORCE in the first subcase and an enforced acceleration by means of the Large Mass method in the second subcase)

 

SOL 129
diag 8
CEND

$

SET 11 = 10

SET 12 = 14

SUBCASE 1
 PARAM,TSTATIC,1
 SPC = 2
 TSTEPNL = 2
 LOAD = 1
 OLOAD = 11
 SPCFORCES = 12
 NLSTRESS = ALL
$
SUBCASE 2
 PARAM,TSTATIC,-1
 SPC = 2
 TSTEPNL = 2
 DLOAD = 2
 ELFORCE = ALL
 NLSTRESS = ALL
$
BEGIN BULK

FORCE, 1, 10, -6.0+3, 1., 0., 0.

TSTEPNL, 2, 180000, 0.5E-3 

SPC1, 2, 12456, 14

Re: Pre-stressed nonlinear transient analysis

The QRG for TSTATIC states that it is only applicable when using adaptive time-stepping (see METHOD = "ADAPT" on the TSTEPNL bulk data entry). I have no experience with this. I'm just reading the QRG.

 

Regards,

Mark

Re: Pre-stressed nonlinear transient analysis

Hi,

 

for SOL129 the default method is ADAPT, that is why I have not written it in the TSTEPNL card.

 

Regards