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# Bolt preload and multiple subcases

Experimenter

Hello Community

Which seetings a have to applie for a simulation with bolt preload and multiple subcases?

I have in subcase 1 only the bolt preload, in subcase 2, 3, 4, .... the bolt preload and different forces.

Current state:

- Calculate subacse 1 (bolt preload)

- Calcualte subcase 2 forces

- Calcualte bolt preload

- Calcualte subcase 3 forces

- Calcualte bolt preload

- Calcualte subcase 4 forces

.....

Ideal state:

- Calculate subacse 1 (bolt preload)

- Calcualte subcase 2 forces

- Calcualte subcase 3 forces

- Calcualte subcase 4 forces

....

Thanks and best Regards

5 REPLIES 5

# Re: Bolt preload and multiple subcases

Siemens Phenom

Is the SID of the bolt preload the same in all 3 subcases? If it is, the preload should not be recomputed in subcases 2 & 3.

Alternatively, if you put the preload in the global case, it should only be calculated once.

# Re: Bolt preload and multiple subcases

Experimenter

Hi to everybody. Sorry for the disturb, but I'm facing the same problem and I cannot find a solution.

I have dozens of subcases to launch with SOL101, and for each subcase the preloads (6 different preloads applied to different bolt locations) are the same (subcase 1 has preloads 1 to 6, subcase 2 has preloads 1 to 6, subcase 3 has preloads 1 to 6, and so on...).

I don't want the preload analysis to be solved at each subcase, since it will double the total time of the solution.

I understand the key is to have the same SID (or boltld, as called in NX Nastran), but even if the preloads don't change amongst the subcases I get always the same message at the end of each subcase n:
"BEGIN CONTACT ITERATIONS FOR BOLT PRELOAD n+1"... and it starts solving again the bolt preload for the subcase n+1.

How can I force  NX to keep the SID of the preloads to remain the same?

I tried to change the boltld in the .dat file imposing the same number for all the subcases, but when I launch the simulation the .dat is overwritten and the boltlds are changed again to the original situation.

Any ideas?

Thanks for you time,

Alessandro.

# Re: Bolt preload and multiple subcases

Siemens Phenom

Try the following case control setup:

CEND
TITLE = Simcenter Nastran Static Analysis Set
ECHO = NONE
DISPLACEMENT(PLOT) = ALL
SPCFORCE(PLOT) = ALL
OLOAD(PLOT) = ALL
FORCE(PLOT,CORNER) = ALL
STRESS(PLOT,CORNER) = ALL
SPC = 1
BOLTLD = 1
SUBCASE 1
LOAD = 2
SUBCASE 2
LOAD = 3
SUBCASE 3
LOAD = 4
BEGIN BULK

Regards,

Joe

# Re: Bolt preload and multiple subcases

Experimenter

Thank you Joe.

I'm really close to come out of this problem, but I can't solve it yet.

When in the case control setup I insert the code you provided (by " user defined text", is this right?", see attach) and I launch the simulation, lots of errors of the series 600 (601, 611, ...) appear and the simulation is immediately aborted.

Do you have any suggestion?

Thank you in advance again,

Alessandro.

# Re: Bolt preload and multiple subcases

Siemens Phenom

Looks like you are using a version Simcenter 3D, not sure exactly how to accomplish that case control with that tool.

I use Femap and it does not require any deck editing to get this setup, the analysis set manager handles it properly:

INIT MASTER(S)
NASTRAN SYSTEM(442)=-1,SYSTEM(319)=1
ID all,Simce
SOL SESTATIC
CEND
TITLE = Simcenter Nastran Static Analysis Set
ECHO = NONE
DISPLACEMENT(PLOT) = ALL
SPCFORCE(PLOT) = ALL
OLOAD(PLOT) = ALL
FORCE(PLOT,CORNER) = ALL
STRESS(PLOT,CORNER) = ALL
SPC = 1
BOLTLD = 1
SUBCASE 1
LOAD = 2
SUBCASE 2
LOAD = 3
SUBCASE 3
LOAD = 4
BEGIN BULK
\$ ***************************************************************************
\$ Written by : Femap
\$ Version : 2019.1
\$ Translator : Simcenter Nastran
\$ From Model : D:\workdir\testing\femap_2019p1\boltpreload\multicase\all_hex20.modfem
\$ Date : Wed May 8 15:15:19 2019
\$ Output To : D:\workdir\testing\femap_2019p1\boltpreload\multicase\
\$ ***************************************************************************
\$