Learning Forum

[Yonghwa Yi]

I want to rotate a sphere using ansys apdl, but the following warnings and errors occur.
How can I correct warnings and errors?

* I also uploaded my ansys apdl code.

 *** WARNING ***                         CP =       6.000   TIME= 19:12:22

 The program chosen initial timestep/load-factor is arbitrary.  It is    

 necessary for the user to supply a suitable initial                     

 timestep/load-factor through the NSUB or DELTIM command for             

 convergence and overall efficiency.                                     

 

 *** ERROR ***                           CP =       7.156   TIME= 19:12:24

 There is at least 1 small equation solver pivot term (e.g., at the UX   

 degree of freedom of node 1140).  Please check for an insufficiently    

 constrained model.     

code : 

/GO 

/COM,   

/COM,Preferences for GUI filtering have been set to display:

/COM,  Structural   

/CLEAR

/FILN,SPHERE_32_reduced

/PREP7

 

!------------ SET PARAMETERS -------------

 

*SET,ANG_VELO,20106

*SET,TEMPER,2573

*SET,RHO,8562

*SET,I,1

 

ET,1,SOLID186   

 

!------------ MATERIAL PROPERTIES ---------

 

MPTEMP,,,,,,,,  

MPTEMP,1,0  

MPDATA,EX,1,,1.03E11

MPDATA,PRXY,1,,0.38 

TB,CREE,1,1,3,10

TBTEMP,0

TBDATA,,0.264E-9,2.476,55326,,, 

MPTEMP,,,,,,,,  

MPTEMP,1,0  

MPDATA,DENS,1,,RHO

 

!------------ CREATE SPHERE ---------

 

SPH4,0,0,0.0011638  

VSBW,ALL  

LOCAL,11,0,0,0,0, ,-90, ,1,1,   

WPCSYS,-1,11,  

VSBW,ALL

LOCAL,11,0,0,0,0, , ,90,1,1,

WPCSYS,-1,11,   

VSBW,ALL

CSDELE,11, ,1,

WPCSYS,-1,0 

VGLUE,ALL

 

!----------- CREATE MESH --------------

 

ESIZE,0.0002097

 

TYPE,   1   

MAT,       1

REAL,   

ESYS,       0   

SECNUM, 

 

MSHAPE,1,3D 

MSHKEY,0

!*  

FLST,5,8,6,ORDE,7   

FITEM,5,1   

FITEM,5,-2  

FITEM,5,4   

FITEM,5,-6  

FITEM,5,8   

FITEM,5,13  

FITEM,5,-14 

CM,_Y,VOLU  

VSEL, , , ,P51X 

CM,_Y1,VOLU 

CHKMSH,'VOLU'   

CMSEL,S,_Y  

!*  

VMESH,_Y1   

!*  

CMDELE,_Y   

CMDELE,_Y1  

CMDELE,_Y2  

 

!------------- APPLY BOUNDARY CONDITIONS ---------

 

TUNIF,TEMPER

 

NSEL,S,LOC,Z,0   

D,ALL,UZ,0  

NSEL,ALL

NSEL,S,LOC,X,0  

NSEL,R,LOC,Y,0  

D,ALL,UX,0  

D,ALL,UY,0  

ALLSEL,ALL

 

!------------- INITIAL CONDITION FOR TRANSIENT ANALYSIS ---------

/SOLU

ANTYPE,TRANS

TIMINT,OFF

SOLCONTROL,1

AUTOTS,1

RESCONTRL,DEFINE,ALL,1,1

LNSRCH,0

CNVTOL,F, ,0.00005,2,0.01,

RATE,1

TIME,1

SOLVE

FINISH

[mjmiddle]

Volume elements, such as solid186, only have translational degrees of freedom (DOF), no rotations. However, the model still needs to be constrained from rotating. This is done by having some constraint in XYZ directions for at least 3 non-colinear nodes. The UZ=0 on the plane of nodes at Z=0 will prevent RX, RY rotation. However, you then restrict the node selection to all nodes along the Z axis and set, UX=0, UY=0. This still allows RZ rotation. If you set UX=0 or UY=0 on just one node not along the Z axis, you will then have a fully constrained model.

[Yonghwa Yi]

thanks for your help
What additional commands should I put in?