*heading
 Input file for the linear buckling analysis.
*parameter
#
#geometric/load parameters (can be modified)
#
radius = 5.0
length = 2.0
thickness = 0.01
tot_load = 1.0
#
#elastic material properties (can be modified)
#
young = 30e+06
poisson=0.3
#
#number of buckling modes to be extractend (can be modified)
#
num_modes=20
#
#internal pressure (can be modified)
#
int_press = 0.0
#
#mesh parameters (can be modified)
#
node_circum = 240
node_length = 21
##
##dependent parameters (do not modify)
##
chn = node_circum*node_length-node_circum
node_ang = -360.0/float(node_circum)
node_tot = node_circum*node_length
node_tmp = node_tot-node_circum+1
node_int = node_length-1
node_circum1 = node_circum+1
node_circum2 = node_circum+2
node_circum0 = node_circum-1
e1 = node_circum*2
p = -tot_load/float(node_circum)
pn = tot_load/float(node_circum)
#
#end of parameter list
#
*node,system=c
1,<radius>,0.0,0.0
<node_circum>,<radius>,<node_ang>,0.0
<node_tmp>,<radius>,0.0,<length>
<node_tot>,<radius>,<node_ang>,<length>
*ngen,line=c,nset=bottom
1,<node_circum>,1,,0.0,0.0,0.0,0.0,0.0,1.0
*ncopy,new set=top,old set=bottom,shift,change number=<chn>
0.0,0.0,<length>
0.0,0.0,0.0,0.0,0.0,1.0,0.0
*nfill
bottom,top,<node_int>,<node_circum>
*element,type=s4
1,1,2,<node_circum2>,<node_circum1>
<node_circum>,<node_circum>,1,<node_circum1>,<e1>
*elgen,elset=cylinder
1,<node_circum0>,1,1,<node_int>,<node_circum>,<node_circum>
<node_circum>,1,,,<node_int>,<node_circum>,<node_circum>
*shell section, elset=cylinder, material=mat_1
<thickness>,
*material,name=mat_1
*elastic
<young>,<poisson>
*nset,nset=ends
bottom,top
*transform,type=c,nset=ends
0.0,0.0,0.0,0.0,0.0,1.0
*boundary
ends,1,2
ends,4,4
ends,6,6
1,3
**
*step,nlgeom
static preload for internal pressure
*static
1.0,1.0
*monitor,node=<node_tot>, dof=3
*dload
cylinder,p,<int_press>
*end step
*step,nlgeom
*buckle,eigensolver=lanczos
<num_modes>,
*cload 
top,3,<p>
bottom,3,<pn>
*output,field
*node output
u,
*node file,global=yes
u,
*end step