buckling
buckling
(OP)
buckling
I'm doing a non-linear analysis in order to perform buckling of a strip. One extremity is clamped. The second one is free and a load is applied.
The linear buckling analysis was ok.
For the non-linear one, using S4R5 elements,
*STEP,NLGEOM,INC=500
*static,riks
...
adding an imperfection or not, the problem is that only the last row of elements at the end of the strip is folded and not all the shape is deformed. (with a picture it would be easier to understand!)
Is anyone has an explanation? I can't find what is wrong.
Thanks a lot !
I'm doing a non-linear analysis in order to perform buckling of a strip. One extremity is clamped. The second one is free and a load is applied.
The linear buckling analysis was ok.
For the non-linear one, using S4R5 elements,
*STEP,NLGEOM,INC=500
*static,riks
...
adding an imperfection or not, the problem is that only the last row of elements at the end of the strip is folded and not all the shape is deformed. (with a picture it would be easier to understand!)
Is anyone has an explanation? I can't find what is wrong.
Thanks a lot !





RE: buckling
Also check that your initial load fraction on the *static does not already exceed the buckling load. Apply about 10-20% of buckling load to start with e.g.
*STATIC
0.1,1.0
If this doesn't fix it, who knows, I'd have to take a look at the model.
regards,
gwolf.
RE: buckling
Unfortunately, I didn't solve my model. As you said, I tried it with 10% of the buckling load and I put the RIKS method off but it doesn't work.
I tried it with the stabilize option too and with a displacement control but the problem is the same.
I don't understand.
How can I join you the model in order to have a look?
Thanks a lot for your experience !
Regards,
Gwen
RE: buckling
corus
RE: buckling
I didn't specific that is a curved thin strip.
Gwen
RE: buckling
RE: buckling
But not with S9R5.
It should work with a simply S4R5 !
...
Gwen
RE: buckling
RE: buckling
*HEADING
TORSIONAL BUCKLING
*RESTART,WRITE
*parameter
R1=0.0359
L=0.6
p=0.060
PI=3.141592654
THETA=(p/R1*180/PI)/2
thickness = 0.0002
BETA=-90-THETA
BETA1=-90+THETA
node_circum=71
node_length=71
node_tot = node_circum*node_length
node_int = node_length-1
node_circum1 = node_circum+1
node_circum2 = node_circum+2
node_tmp = node_tot-node_circum+1
node_circum0 = node_circum-1
chn = node_circum*node_length-node_circum
*NODE,SYSTEM=C
10000,0,0,0
20000,0,0,<L>
1,<R1>,<BETA>,0
<node_circum>,<R1>,<BETA1>,0
<node_tmp>,<R1>,<BETA1>,<L>
<node_tot>,<R1>,<BETA>,<L>
*NGEN,LINE=C,NSET=bottom,SYSTEM=C
1,<node_circum>,1,10000,,,,0,0,1
*ncopy,new set=top,old set=bottom,shift,change number=<chn>
0,0,<L>
0,0,0,0,0,1,0
*NFILL
bottom,top,<node_int>,<node_circum>
*ELEMENT,TYPE=S4R5
1,1,2,<node_circum2>,<node_circum1>
*ELGEN,ELSET=LAME
1,<node_circum0>,1,1,<node_int>,<node_circum>,<node_circum>
*SHELL SECTION,ELSET=LAME,MATERIAL=MAT
<thickness>,
*MATERIAL,NAME=MAT
*ELASTIC
2.03E11,.3
**
*STEP,NLGEOM,INC=500
postbuckling analysis
*static,STABILIZE,FACTOR=0.0001
0.0001,1,1.E-30
*monitor,node=5006,dof=3
*BOUNDARY
5006,3,,-1
*BOUNDARY
bottom,1,6
*CONTROLS,ANALYSIS=DISCONTINUOUS
*OUTPUT,FIELD,FREQUENCY=2
*NODE OUTPUT,NSET=TOP
U,RF
*NODE OUTPUT,NSET=BOTTOM
RF,
*ELEMENT OUTPUT
S,
*OUTPUT,HISTORY,FREQUENCY=2
*NODE FILE,NSET=TOP
U,
RF,
*END STEP
RE: buckling
corus
RE: buckling
*ELEMENT,TYPE=S4R5
1,1,2,<node_circum2>,<node_circum1>
*ELGEN,ELSET=LAME
1,<node_circum0>,1,1,<node_int>,<node_circum>,<node_circum>
*SHELL SECTION,ELSET=LAME,MATERIAL=MAT
<thickness>,
*MATERIAL,NAME=MAT
*ELASTIC
2.03E11,.3
**
*STEP,NLGEOM,INC=500
postbuckling analysis
*static,STABILIZE,FACTOR=0.0001
0.0001,1,1.E-30
*monitor,node=5006,dof=3
*BOUNDARY
5006,3,,-1
*BOUNDARY
bottom,1,6
*CONTROLS,ANALYSIS=DISCONTINUOUS
*OUTPUT,FIELD,var=preselect
*OUTPUT,HISTORY,var=preselect
*END STEP
corus
RE: buckling
The shell deforms but the base of the shell is fully restrained and hence the shell buckles some distance above the fixed base.
corus
RE: buckling
Conclusion is that spaces from the beginning of lines are dangerous !?
It's exactly what I want to verify : Buckling in a bending mode because of the bending moment.
Thanks a lot !