Learning Forum

[MECHENG_153951]

Hello.

I am trying to make a transient analysis of a structure after it has settled into its static solution. Unfortunately, one cannot use initial conditions after the first load step, why I cannot apply translatory velocity to nodes:

Hi(@MECHENG_153951 ) Chris

One possible way (not sure since you use initial velocity if it will work, but it is the only way I know), is to

use transient for all, and the first part is the transient effects deactivated and in the final part add them on (TIMINT command).

/forum/discussion/29913/how-to-carry-out-a-transient-analysis-following-on-from-a-static-analysis-in-ansys-mechanical-apdl

See the above link/post that explains this flow.

Thank you

Erik

[MECHENG_153951]

When doing transient analyses it is possible to describe velocities with:
D,NODE,VEL(X/Y/Z),velocity_1,...
I tried to do this, but I am not confident in the results given. Thus I have surrendered and are now applying force-loads which gives me an equivalent of the desired speed.

[Sheldon Imaoka]

The use of the "D" command to apply velocity (D,node,VELX,value) specifies a known/given velocity that is maintained. If you want to keep/maintain that velocity, you want to use "D".
The use of the "IC" command to apply velocity (IC,node,UX,,value) specifies an initial velocity at the start of the analysis. The velocity at that node may change from "value" to a different value during the analysis, depending on what is happening to the system. Please be careful of location of "value" - the first field is the initial displacement, which you want to leave as "0", and the second value is the initial velocity.
So to clarify, if you have a boundary condition on a node where you want to maintain 10 m/s no matter what happens, then you want "D". However, if you want to specify an initial velocity of 10 m/s, then you want "IC" - in the latter case, the velocity may change, depending on the calculations (for example, an object 'thrown' in the air will have an initial velocity, not prescribed velocity, since the velocity isn't maintained forcefully).
Regards Sheldon

[MECHENG_153951]

.
Thanks for your input.
When doing the transient analysis my idea was to prescribe the velocity with 'D' for a small time step, to simulate an impulse load. My trouble was that my structure is rather flexible and is subjected to gravity, and I wanted to record its response from static equilibrium. Therefore I needed the static solution before applying initial conditions, and since 'IC' only can be used in the first time step, this was not an option.
The load case is no longer of interest to me, but your help is appreciated.
Regards Chris.