Learning Forum

[fang pc]

I have some problems when using shell99 element keyopt2,3, I input A B D E F matrix, and ensure that they are positive definite, but when calculating, ansys prompts an error,

*** ERROR ***                           CP =       9.406   TIME= 10:53:01
 Input matrix of element 1 is not positive semi-definite.  Check real    
 constant table 1.                                                       

how to solve it
Here's what I wrote about apdl

/prep7
ESEL,s,elem,,       1,       1,    1600
ET,       1,99
KEYOPT,       1,2,3
R,        1,  0.10000000E+12
RMODIF,        1,2,  0.91158854E+02
RMODIF,        1,4,  0.21316282E-13
RMODIF,        1,7,  0.10000000E+11
RMODIF,        1,9,  0.26645353E-14
RMODIF,        1,12,  0.10000000E+11
RMODIF,        1,16,  0.10000000E+11
RMODIF,        1,19,  0.10000109E+11
RMODIF,        1,21,  0.10000109E+11
RMODIF,        1,22,  0.10000002E+10
RMODIF,        1,23, -0.68903426E+02
RMODIF,        1,25,  0.94291151E+02
RMODIF,        1,28,  0.99999998E+09
RMODIF,        1,30,  0.38613569E+02
RMODIF,        1,33,  0.10000000E+10
RMODIF,        1,37,  0.99999993E+09
RMODIF,        1,40,  0.99993110E+09
RMODIF,        1,42,  0.99993110E+09
RMODIF,        1,43,  0.10000000E+11
RMODIF,        1,44,  0.43756250E+02
RMODIF,        1,46,  0.52558450E+01
RMODIF,        1,49,  0.10000000E+11
RMODIF,        1,51,  0.68758909E+00
RMODIF,        1,54,  0.10000000E+11
RMODIF,        1,58,  0.10000000E+11
RMODIF,        1,61,  0.10000052E+11
RMODIF,        1,63,  0.10000052E+11
RMODIF,        1,64,  0.10000005E+10
RMODIF,        1,65, -0.19689154E+03
RMODIF,        1,67, -0.52614462E+03
RMODIF,        1,70,  0.99999994E+09
RMODIF,        1,72, -0.21546371E+03
RMODIF,        1,75,  0.10000000E+10
RMODIF,        1,79,  0.99999980E+09
RMODIF,        1,82,  0.99980311E+09
RMODIF,        1,84,  0.99980311E+09
RMODIF,        1,85,  0.10000000E+11
RMODIF,        1,86,  0.37805400E+02
RMODIF,        1,88,  0.14545551E+02
RMODIF,        1,91,  0.10000000E+11
RMODIF,        1,93,  0.19029028E+01
RMODIF,        1,96,  0.10000000E+11
RMODIF,        1,100,  0.10000000E+11
RMODIF,        1,103,  0.10000045E+11
RMODIF,        1,105,  0.10000045E+11
RMODIF,        1,125,  0.24000000E+01
EMODIF,ALL,REAL,       1
EMODIF,ALL,TYPE,       1

[Long Song]

I met the same problem.

[Ashish Khemka]

 

Hi,

Which version of Ansys are you using? SHELL99 is no longer supported in the current version.

Regards,

Ashish Khemka

 

[fang pc]

Thank you for your answer. I am using version ANSYS191. By the way, may I ask which element should be used to replace the current version

[Ashish Khemka]

You can try Shell 281.

Regards,

Ashish Khemka

[fang pc]

Thank you for your answer. If I continue to use shell99, can you solve the problem of my input matrix? Or the new version which element can input the matrix