Learning Forum

[Tanmay Konnur]

How do I apply compressive and tensile intrinsic stress (on separate occasions) to a circular shell element such that it is uniform across the circular shell element. I do not want a gradient. Is INISTATE command applicable in this case?

[Bill Bulat]

Yes, INISTATE is the command to use. I found this old MAPDL input file (pasted below) in my examples directory that illustrates usage. In this example, INISTATE is applied to solid elements, but it works for shells as well. With layered shells, you can apply different initial stresses to individual layers.

 

I forget whether or not this feature is natively exposed in Mechanical. If not, you'll need to use an APDL command object to implement it.

 

fini

/cle

 

/vup,1,z

/vie,1,1,1,1

/pnu,mat,1

/num,1

/gra,full

 

/sys,del *.png

 

 

C******************************************************

C*** PARAMETERS

C******************************************************

l=1000e-6

w=100e-6

 

t_Pd=5e-6

t_Cu=5e-6

 

E_Pd=110e9

nu_Pd=0.39

 

E_Cu=117e9

nu_Cu=0.34

 

sgma_Pd=1e6

 

 

C******************************************************

C*** GEOMETRY

C******************************************************

/prep7

 

vsel,none

bloc,,l,,w,,t_Cu

vatt,2,2,2

 

vsel,none

bloc,,l,,w,t_Cu,t_Cu+t_Pd

vatt,1,1,1

 

numm,kp,1e-8,1e-8

 

 

C******************************************************

C*** ATTRIBUTES, MESH

C******************************************************

et,1,185,,2 ! PALLADIUM ATTRIBUTES

mp,ex,1,E_Pd

mp,nuxy,1,nu_Pd

 

et,2,185,,2 ! COPPER ATTRIBUTES

mp,ex,2,E_Cu

mp,nuxy,2,nu_Cu

 

alls ! MESH

vplo

vmes,all

 

 

C******************************************************

C*** BCs

C******************************************************

alls

d,node(0,0,0),all

d,node(0,w,0),ux

d,node(0,w,0),uz

d,node(0,0,t_Pd+t_Cu),ux

 

 

C******************************************************

C*** Pd INITIAL STRESS

C******************************************************

inistate,set,dtyp,,stre

 

esel,s,mat,,1

inistate,define,,,,,sgma_Pd,sgma_Pd,sgma_Pd

 

fini

 

 

C******************************************************

C*** SOLVE

C******************************************************

alls

/solu

save

solv

fini

 

 

C******************************************************

C*** POST PROCESS

C******************************************************

/post1

 

/pbc,u,1

eplo

/sho,png $eplo $/sho,close $/wait,2

 

plns,u,z

/sho,png $plns,u,z $/sho,close $/wait,2

 

plns,s,x

/sho,png $plns,s,x $/sho,close $/wait,2

 

esel,s,mat,,1

plns,s,x

/sho,png $plns,s,x $/sho,close $/wait,2

 

esel,s,mat,,2

plns,s,x

/sho,png $plns,s,x $/sho,close $/wait,2