Boundary Conditions for a sphere

Dear Seabass8,
You have "rigid body" movements in your model then your stiffness matrix is singular, not anougth constraints defined or a joint failed, to debug the modeling error you can include in the NASTRAN bulk data section the card "PARAM,BAILOUT,-1", re-run the linear static SOL101 analysis and animate the displacement results, you will see where the error is located, OK?.

This a typical error of either lack of cosntraints or bad use of finite elements, take a look to my blog in the following address:

http://iberisa.wordpress.com/2011/0...run-terminated-due-to-excessive-pivot-ratios/

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB: Blog de FEMAP & NX Nastran:

Hello Blas,
Many thanks for your reply.

I didn´t know the the card "PARAM,BAILOUT,-1", I have seen your blog and it is quite well explained.
I set it in NASTRAN bulk data section and re-run the analysis.
Now Patran attaches de db file and I get a solution. I have seen that node 1166 has a displacement of 1 meter.
The thing is that the structure is symmetric, node 1166 gets much displacement but its symmetric one gets a normal value.
I am thinking if it is also due to a bad element

I attach my db

Hello!,
Binary *.db file is not possible to import in FEMAP, generate your nastran input file *.dat
Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB: Blog de FEMAP & NX Nastran:

Hello Blas,

I have seen that I´ve uploaded .f04 and f06.

Many thanks

Hello!,
Please include the nastran input file that is an ASCCI file, this is the file generated by the preprocessor with the extensión *.nas, or *.dat, or *.bdf. The files you attached are the output files *.f06, that include only results, not the FE model, OK?.
Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB: Blog de FEMAP & NX Nastran:

Hello Blas,

I´ve uploaded the .bdf

Thanks again

Hello!,
A simply visual inspection rotating the model will show you that you have a member free at one end. Also you have many nodes free, with no connection with any element. And only CBAR elements exist, not any track of Shell elements for the spherical tank.



Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB: Blog de FEMAP & NX Nastran:

Hello again,

Thanks for your comments. It really helps me.
Here I have got a more accurate model. I´ve solved the problem of the free nodes and the brace
that was not well pinned.
The deformations look realistic. But looking at the .f06 some elements have a taper ratio greater than 0.5.

In my opinion the Boundary conditions are well established.

Best regards

Hello!,
The QUAD mesh of the sphere is a litle disaster, you are violating the minimum quality checks imposed by nastran:

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* * VERSION - 8.1 * *
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* * OCT 6, 2011 * *
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Welcome to NX Nastran
-------------------------

M O D E L S U M M A R Y

NUMBER OF GRID POINTS = 298

NUMBER OF CBAR ELEMENTS = 120
NUMBER OF CQUAD4 ELEMENTS = 208

*** USER INFORMATION MESSAGE 7555 (GMTSTD)
FINITE ELEMENT GEOMETRY CHECK RESULTS EXCEED TOLERANCE LEVELS FOR THE FOLLOWING ELEMENTS.
USER ACTION: USE THE GEOMCHECK (EXECUTIVE CONTROL STATEMENT) KEYWORD=VALUE TO CHANGE TOLERANCE VALUES IF DESIRED.
User information:
Element Geometry test tolerance levels and message limits can be changed by the GEOMCHECK Executive Control statement.
The following keywords are available:
Q4_SKEW - to modify the CQUAD4/CQUADR skew angle test tolerance.
Q4_TAPER - to modify the CQUAD4/CQUADR taper ratio test tolerance.
Q4_WARP - to modify the CQUAD4/CQUADR warping coefficient test tolerance.
Q4_IAMAX - to modify the CQUAD4/CQUADR maximum interior angle test tolerance.
Q4_IAMIN - to modify the CQUAD4/CQUADR minimum interior angle test tolerance.
T3_SKEW - to modify the CTRIA3/CTRIAR skew angle test tolerance.
T3_IAMAX - to modify the CTRIA3/CTRIAR maximum interior angle test tolerance.
TET_AR - to modify the CTETRA aspect ratio test tolerance.
TET_EPLR - to modify the CTETRA edge node point length ratio test tolerance.
TET_DETJ - to modify the CTETRA determinant of the Jacobian matrix test tolerance.
TET_DETG - to modify the CTETRA determinant of the vertex points Jacobian matrix test tolerance.
HEX_AR - to modify the CHEXA aspect ratio test tolerance.
HEX_EPLR - to modify the CHEXA edge node point length ratio test tolerance.
HEX_DETJ - to modify the CHEXA determinant of the Jacobian matrix test tolerance.
HEX_WARP - to modify the CHEXA face warping coefficient test tolerance.
BEAM_OFF - to modify the CBEAM offset length ratio test tolerance.
BAR_OFF - to modify the CBAR offset length ratio test tolerance.
MSGLIMIT - to limit the number of messages that are generated.
MSGTYPE - to modify the severity level of the test.
A MAXIMUM OF 100 SKEW ANGLE (SA) TOLERANCE LIMIT VIOLATIONS WILL BE IDENTIFIED AND INDICATED BY xxxx.
A MAXIMUM OF 100 MIN INT. ANGLE (IA) TOLERANCE LIMIT VIOLATIONS WILL BE IDENTIFIED AND INDICATED BY xxxx.
A MAXIMUM OF 100 MAX INT. ANGLE (IA) TOLERANCE LIMIT VIOLATIONS WILL BE IDENTIFIED AND INDICATED BY xxxx.
A MAXIMUM OF 100 WARPING FACTOR (WF) TOLERANCE LIMIT VIOLATIONS WILL BE IDENTIFIED AND INDICATED BY xxxx.
A MAXIMUM OF 100 TAPER RATIO (TR) TOLERANCE LIMIT VIOLATIONS WILL BE IDENTIFIED AND INDICATED BY xxxx.

TOLERANCE LIMITS ARE: SA = 30.00, IA(MIN) = 30.00, IA(MAX) = 150.00, WF = 0.05, TR = 0.50 (xxxx = LIMIT VIOLATED)
ELEMENT TYPE ID SKEW ANGLE MIN INT. ANGLE MAX INT. ANGLE WARPING FACTOR TAPER RATIO
QUAD4 103 63.51 44.11 118.38 0.01 0.51 xxxx
QUAD4 125 64.01 44.71 105.56 0.01 0.52 xxxx
QUAD4 173 63.41 44.12 120.10 0.01 0.51 xxxx



E L E M E N T G E O M E T R Y T E S T R E S U L T S S U M M A R Y
TOTAL NUMBER OF TIMES TOLERANCES WERE EXCEEDED
ASPECT/ MINIMUM MAXIMUM SURFACE/FACE EDGE POINT JACOBIAN
ELEMENT TYPE SKEW ANGLE TAPER RATIO INTER. ANGLE INTER. ANGLE WARP FACTOR OFFSET RATIO LENGTH RATIO DETERMINANT
BAR N/A N/A N/A N/A N/A 0 N/A N/A
QUAD4 0 3 0 0 0 N/A N/A N/A

N/A IN THE ABOVE TABLE INDICATES TESTS THAT ARE NOT APPLICABLE TO THE ELEMENT TYPE AND WERE NOT PERFORMED.
FOR ALL ELEMENTS WHERE GEOMETRY TEST RESULTS HAVE EXCEEDED TOLERANCES,

QUAD4 ELEMENT ID 125 PRODUCED LARGEST TAPER RATIO OF 0.52 (TOLERANCE = 0.50).

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB: Blog de FEMAP & NX Nastran: