Normal Modes with Static Preload

Bernt Isaksen

We have a Pressure Vessel where we want to investigate different pressures and boundary conditions. I get the following error:

*** ERROR # 6503 ***
Linear subcases (Static/Frequency/Transient/Eigenvalue) cannot use
different LGDISP preloading conditions, including no preloading.

*** Run terminated because of error(s) in the input data.

My input data looks like the following:

MFLUID = 45
SUBCASE 1
LABEL Prestension Internal Pressure
ANALYSIS NLSTAT
SPC = 1
LOAD = 17
NLPARM = 22
NLADAPT = 20
CONTF(H3D,ALL) = ALL
DISPLACEMENT(H3D) = ALL
SPCFORCE(H3D) = ALL
$ STRAIN(H3D) = ALL
STRESS(H3D) = ALL
$SUBCASE 2
$ LABEL y-accel
$ANALYSIS NLSTAT
$CNTNLSUB 1
$ SPC = 1
$ LOAD = 19
$ NLPARM = 22
$ NLADAPT = 20
$ CONTF(H3D,ALL) = ALL
$ DISPLACEMENT(H3D) = ALL
$ SPCFORCE(H3D) = ALL
$ STRAIN(H3D) = ALL
$ STRESS(H3D) = ALL
$
$HMNAME LOADSTEP 3"Modes" 3
$
$SUBCASE 3
$ LABEL Modes with Inner Pressure
$ANALYSIS MODES
$ SPC = 1
$ METHOD(STRUCTURE) = 21
$ DISPLACEMENT(H3D) = ALL
$ ESE(H3D) = ALL
$
$HMNAME LOADSTEP 4"SRS" 18
$
$SUBCASE 4
$ LABEL SRS
$ANALYSIS RSPEC
$ SPC = 1
$ METHOD(STRUCTURE) = 21
$ SDAMPING(STRUCTURE) = 44
$ RSPEC = 26
$ DISPLACEMENT(H3D) = ALL
$ ESE(H3D) = ALL
$ STRESS(H3D) = ALL
$
$HMNAME LOADSTEP 5"Modes with liquid" 3
$
SUBCASE 5
LABEL Modes with liquid
ANALYSIS MODES
SPC = 1
$ MPC = 45
METHOD(STRUCTURE) = 21
STATSUB(PRELOAD) = 1
DISPLACEMENT(H3D) = ALL
$ ESE(H3D) = ALL
STRESS(H3D) = ALL
$
$HMNAME LOADSTEP 6"Sine Freq resp" 6
$
SUBCASE 6
LABEL Modal Frequency response with liquid.Excitation in X
ANALYSIS MFREQ
DISPLACEMENT(H3D) = ALL
STRESS(H3D) = ALL
DLOAD = 133
SPC = 134
FREQUENCY = 47
METHOD(STRUCTURE) = 21
$ METHOD(FLUID) = 45
SDAMPING(STRUCTURE) = 44
DISPLACEMENT(PHASE,PUNCH)=599
DISPLACEMENT(H3D) = ALL
ESE(H3D) = ALL
STRESS(H3D) = ALL

 

I appreciate any expert consideration

Adriano A. Koga

i guess you need to include your preload into your Modal FRF loadcase as well, as you have inlcuded it into your modal analysis.