Learning Forum

[www.chanees777]

Hi I am doing buckling analysis on a curved panel whose schematic I have attached. I have been trying to do buckling analysis on this geometry for different cases but results dont seem to be matching with theoretical. Can someone please guide me whats wrong in my code? Lets consider this case a=b=50mm, Theta=180 degrees, E= 200MPa, t=0.5, poisson ratio=0.3. Thank you very much. /CLEAR      
/PREP7  
smrt,off
ANTYPE,STATIC  
ET,1,SHELL63,, 
R,1,0.5  
MP,EX,1,200e9 
MP,NUXY,1,0.3   
R1 = 31.38
L = 25
PI = 4*ATAN(1)
T=PI/2
THETA =T*180/PI
CSYS,1 
K,2,R1,90,L
K,3,R1,(90-THETA),L
K,5,R1,90,-L
K,6,R1,(90+THETA),L
K,7,R1,(90-THETA),-L
K,8,R1,(90+THETA),-L
l,3,2   
l,2,6   
l,3,7   
l,7,5   
l,5,8   
l,6,8
lcomb,1,2
lcomb,4,5
al,1,3,4,6
LESIZE,ALL, , ,24, ,1, , ,1,
amesh,1
lsel,s,line,,3
lsel,A,line,,6
nsll,,1
D,ALL, , , , , ,UY, , , , ,
lsel,s,line,,4
nsll,,1
D,ALL,, , , , ,, , , , ,UZ
lsel,s,line,,4
local,11,1,0,0,0,    
nsll,,1          
nrotate,all         
D,ALL, uX, , , , ,, , , , ,    
lsel,s,line,,1
local,11,1,0,0,0,    
nsll,,1          
nrotate,all        
D,ALL,, , , , ,UX, , , , ,    
F,ALL,FZ,-1/25
/sol
PSTRES,1
solve
finish
/sol
ANTYPE,1  
BUCOPT,LANB,2,0,0,CENTER
solve
finish
/post1
set,list

[www.chanees777]

Anyone please help, will be really appreciated. I have been stuck on this for over a week now.

[dlooman]

Sometimes it is good to run your input in batch mode.  It is easier to find the error messages that way.  When I do that with your input above I see the error:

*** WARNING ***                         CP =       0.109   TIME= 10:53:30
 No valid degree of freedom labels were input.  The D command is         
 ignored. 

That can be fixed like below:

! D,ALL,, , , , ,, , , , ,UZ
d,all,uz,0

 

I also saw these warnings during solution: 

*** WARNING ***                         CP =       0.266   TIME= 10:53:30
 Node 97 on element 1 is unselected.

That can be fixed with nsel,all before solution.

Your boundary condition at the vertical edges is an axial constraint.  That doesn't seem right.  Check your boundary conditions interactively with /pbc,all,1 and nplot.