Drop Test without LS-DYNA

[huiying]

Hi,
Would like to know whether it is possible to do a drop test analysis just using Ansys Structural? Has anyone tried before? What is the limitations and how is it different from using LS-DYNA?

Thanks & Regards.

 

[Drej]

You can't use inertia relief in a drop test. Inertia relief has a specific purpose (see the irlf command in the help file) in which the applied forces and torques are balanced by inertial forces induced by an acceleration field. If you used this in a drop test, your object would not move at all! Inertia relief is used for free body simulations such as aircraft components. You probably can use ANSYS for a drop test simulation, but it is not really geared up for this sort of thing, which is why LS-DYNA was introduced. If you were to do it in ANSYS you would need to be very careful:

1/ model size massively affects your run time
2/ the implicit time integration method isn't suited to such discontinuous events with the time step becoming very, very small (since LS-DYNA is an explicit time integration code, small time steps better suit the algorithm)
3/ as with any transient analysis, you need to introduce initial conditions for the drop test, including initial displacement (u0) and initial velocity(v0) - these have to be specified.
4/ you can also use the IC command.

Be very careful!



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