Looking for a drop test benchmark

[EricatST]

I'm running a drop test simulation and getting some dubious results.

Can anyone point me at a simple benchmark example for an object dropping onto a hard surface so I can carry out a few reality checks.

Failing that if anyone can suggest a simple example where decelerations are easy to calculate I'd be very grateful.

Thanks.

 

[GBor]

Seems like something the Algor website should have readily available, but if they don't, I can give this advice:

Results are EXTREMELY sensitive to the stiffness of the impact surface.

Generally, the impact surface is an "impact wall" with a virtually infinite stiffness. This is actually not the case in real life, but it should be conservative for most appications.

The first "drop test" I did, I modeled a 2-D block and dropped it on an impact wall. I didn't constrain the edges, so round-off error led to it bouncing off to one side on the rebound. After working with that for a while, I then checked stresses...they were WAY off (but this has been several years ago...before MES).

In a real-world comparison, I dropped an object onto a load cell and got the dynamic output. When I dropped my virtual model onto an impact wall, again, stresses were no where close. When, however, I modeled the load cell as a flat plate with a spring underneath it and "tuned" the spring so that the natural frequency of the simulated load cell was comparable to the natural frequency of the real load cell, my strain results were "spot on".

Simulations aren't easy, but they are fun and can be useful so long as you know what you are looking at. If your results look dubious...they probably are! Nice catch.



Garland E. Borowski, PE
Engineering Manager
Star Aviation