Drop Tests - Impact Question

[Jackmn]

Hi all.

I am conducting some low velocity drop test experiments. The test specimen is clamped and held inside a cradle which itself is attached to a load cell. The load cell works in tension and records the force on the cradle.

I believe that the KE just before impact is dispersed in three main ways:
-Absorbed by the specimen by plastic defomation
-On the clamp that holds the specimen - this force is read by the load cell
-The residual velocity of the projectile (if any)
Plus noise and other small losses.

So, my question is, how can i get an energy value from the load cell reading? I need this to find the energy absorbed by the specimen. The load cell gives me a force v time graph. I believe the area under this curve is the impulse, but I'm unsure how I can equate this to an energy value.
Any help would be great - Thanks a lot.
Cheers

 

[Jhero]

Hi there,

Thank you for sharing your experiment with us. It sounds like an interesting and important study. To answer your question, you are correct in thinking that the area under the force versus time curve is the impulse. This impulse is equal to the change in momentum of the specimen, which can be calculated by multiplying the force by the time over which it acts.

To convert this impulse into energy, you can use the equation E = 1/2mv^2, where E is the energy, m is the mass of the specimen, and v is the velocity. This equation assumes that all of the kinetic energy is transferred to the specimen, so it may not be entirely accurate in your case. However, it can give you a rough estimate of the energy absorbed by the specimen.

Another approach you could consider is using strain gauges on the specimen to measure its deformation during the impact. This can give you a more direct measurement of the energy absorbed by the specimen.

I hope this helps. Best of luck with your experiments!