CP/CE commands

[SKJoe]

Hi,

In my nonlinear analyse loads must be applied in two load steps. I the second load step I need to change the stiffness of one part of the model as well as boundary conditions via CP or CE command. The problem is that this can not be done sumultaneously. A change of CP can be done only in /prep7, so I have to use lswrite and lssolve commands. But lssolve do not work with mpchg, the solve command must be used instead. I realized that CE can be changed during solution via cecmod command. I have 50 nodes on line in y-direction, which I want to have the same displacement in x-direction...CP,1,UX,ALL.

So how to construct constraint equations to be consistent with CP,1,UX,ALL ?

Regards,
Lubo

 

[SKJoe]

Hi,

I have just realized that via cecmod can be changed only "constant" in constraint equation, CE can not be deleted. So it is going to be useless anyway I think...

 

[samuelecorsi]

Hi SKJoe, a question for you:
i know that is possible modify loads using load steps file. but is also possible add or modify contraints during the same analisys? and the way to modify constraints is the same for the load, so i need to create different load step and between two load steps can i modify constraints?

samuele

 

[SKJoe]

Hi samuelecorsi,

you are right, but there are two ways to do that in nonlinear analyse depends on what you want to change. In subsequent load steps (without leaving solution processor)you can modify loads, constraints, use ekill/alive and change material properties via mpchg as follows :

/sol

! 1.load step
time, 1
f,node_1,fx,10
d,node_1,,,,,,uy
ekill...
solve
! 2.load step
time, 2
fcum, add
f,node_1,fx,20
ddele,node_1,all
d,node_1,,,,,,uy,rotz
alive...
mpchg...
solve

fini
/post..

If you want to change cp/ce (it is not recomended to use cp/ce in nonlinear analyse...) you must use lswrite/lssolve instead, but you can not use ekill,alive,mpchg as follows :

save

! 1.load step

fini
/prep7
cp,1,ux,nodes_a
fini
/sol

time, 1
f,node_1,fx,10
d,node_1,,,,,,uy
lswrite,1

! 2.load step

fini
/prep7
cpdele,1,1,1,all
cp,1,UX,nodes_b
fini
/sol

time, 2
f,node_1,fx,10+20
ddele,node_1,all
d,node_1,,,,,,uy,rotz

lswrite, 2

fini
resume...
/sol

lssolve,1,2
fini
/post..

I hope it is written correctly...

Regards,
Lubo