# Explicit dynamics simulation takes too long to solve

Hello,

I put in place a simulation where a 25mm diameter punch must go through a composite plate (10*10mm).

I put the velocity of the punch to 0.0006mm/s and the end time to 60seconds because that is how it goes in real life. The problem is that I don't know why it takes forever to solve. I am new to Ansys so maybe my settings are wrong. I am desperately seeking for help.

the composite sample is on a steel plate that is used for support which has a 32mm diameter hole in its center.

• edited December 2020 Accepted Answer

Run a series of simulations where you change the velocity and end time by a factor of 100, 1000, 10000, 100000.

Plot the Total Energy and the Kinetic Energy on each simulation.

When Kinetic Energy is a very small percentage of the Total Energy, the simulation is very close to quasi-static.

When Kinetic Energy is a significant percentage of the Total Energy, then the simulation is no longer quasi-static.

• 1) Configure the CAD so that the punch is touching the sample.

2) Speed up the velocity by 1000 times.

3) Reduce the end time by 1000 times.

4) It looks like your composite material has only 1 element through the thickness. That is unacceptable. You need tens of elements through the thickness.

• This is more like quasi-static simulations since the speed is so low and the time duration is quiet large, explicit will take a long long long time to solve it,

instead what u can try is to increase the velocity and reduce the time

I've come across this yesterday and it very helpful (sorry i don't know how to insert a hyperlink)

e

• But isn't changing the velocity and end time changing the whole simulation thus giving me the wrong results? It is normal the meshing only shows one layer but i did put some (16 of carbon and 1 Honeycomb) - I don't know why it shows one layer.

• edited December 2020 Accepted Answer

Run a series of simulations where you change the velocity and end time by a factor of 100, 1000, 10000, 100000.

Plot the Total Energy and the Kinetic Energy on each simulation.

When Kinetic Energy is a very small percentage of the Total Energy, the simulation is very close to quasi-static.

When Kinetic Energy is a significant percentage of the Total Energy, then the simulation is no longer quasi-static.