## LS Dyna

#### Explicit dynamics – submodeling

• Jendys
Subscriber

Hello everyone, can I have a question?

I am currently dealing with problem of how to get a action created at a specific time in explicit dynamics into a static structure via submodeling. In Ansys help I did not find any instructions on how to perform this operation

For example I use an image in attachment. (not mine). I would like to get moment when the cube is touched the floor to the static structural. Is it possible?

• Sandeep Medikonda
Ansys Employee

Hi,

As far as I know, I think you can only use sub modeling in only one analysis system throughout. So either Static Structural - Static Static Structural or the same way in Explicit (ANSYS LS-DYNA).

For the problem you showed, I don't think you would even need Sub-modeling and I think it can be modeled in Transient Structural or just standalone Explicit.

Regards,
Sandeep

• peteroznewman
Subscriber

Hi Jendys,

It looks like you want to do a drop test. While a physical drop test is done by releasing the object with zero velocity at time 0 from a height h, that is not how a drop test is performed in simulation.

To simulate a drop test, you go into CAD and you move the cube so the point is just touching the plate. Then in Explicit Dynamics (or Transient Dynamics), you assign the Initial Velocity, v, to the cube at time 0. Then the solver integrates the dynamic equations to show you what happens from the instant of impact onward.

Do you know how to calculate the Initial Velocity, v, from the drop height h? You may have learned this in high school Newtonian physics class. v = sqrt(2*g*h) where g is 9.8 m/s^2 and h is in meters and v is in m/s.

If you just want to know the time, t, in seconds it will take for the cube to hit the floor, t = sqrt(2*h/g).

Regards,

Peter