Speed from Deformation at Impact

Just to make sure: You don't know the height that the tool is dropped from? (because the velocity would be easy to calculate then)

The tool was dropped in an 8,000 ft hole through both gasses and liquids (in unknown concentrations) which were flowing up and out of the hole. That makes the velocity a bit more complicated to calculate.

Ahh, yes - that makes more sense (and more difficult )

You are on the right trck - but I believe your error is in the deformation part.

What you need to do is equate the strain energy to the kinetic energy of the part.

I guess that this stem should be modelled as a beam in bending with the properties at the hole. But I can't say without knowing more about how this tool falls/lands, and how this stem is bent. But just thinking now - would it be more accurate that the stem be modelled as a column? Or a beam-column?

For example -

http://www.roymech.co.uk/Useful_Tables/Beams/Strain_Energy.html

I am currently away from my book of "Engineering Materials 3 - Materials Failure Analysis - Case Studies and Design Implications"; by Jones

If you can track down a copy - it will have your answer.

I will also look - but it won't be until tomorrow.

It would more accurately be described as a column.

Could you show a picture of bend tool? It will allow the making of a "model" for the analysis.

Unfortunately, the guys in the field cut the bent part in order to take the tool apart. The part that was bent was a 1/2" OD rod with a 0.190 hole drilled across the diameter of the rod. The deformation turned the circular holes into ovals.

You said the mass of the item was 2.72 kilos, speed unknown. How about the mass of whatever was delivering the item to the bottom of the hole? It was 8000 foot of something..... Why not use a harder version of stainless? Does it have to have that hole cross-drilled into it? Take the thing outside and drop it until you get the same damage, then measure that. But you must have the correct mass, that's part of the formula.

I do not know which is outer diameter of the part and its length and the internal diameter of the tube but if the gap is not too large the flow in it could generate a pressure difference high enough to limit the final falling speed at contact.

I think that it will be difficult to obtain positive results only by increase of section, a new design so that the part can absorb the shock energy could offer more. In fact -if the function for which it is thought allows- the part should have a compliance big enough in order to limit the contact stress at a value lower elastic limit.

Can you send a drawing of the part and indicate what cannot be changed?

I think your model of the tool is not complete. Think about a bullet fired from a gun. You can measure its mass and its velocity. You can even square the velocity and multiply by its mass to calculate energy. But it isn't until the bullet is stopped, that you can estimate the internal stresses on it. If you fire the bullet into a tub of water or ballistic jelly, it decelerates slowly and survives its trip in almost pristine condition. If you fire it at a steel plate ------- I think you get the point---(no pun intended).

Thanks everyone. I think my best bet is going to be to work through this experimentally. I have a re-design that will make the stem stronger, and I'll probably do some very scientific expermients involving a sledge hammer to test it out.

A sledge hammer is okay, but kind of a brute force approach. With the ban on whaling, you ought to be able to get a good deal on a harpoon gun. Then you can perform some legitimate testing.

Of course it could be difficult to determine the right form only by computing but for your development it could be of interest to build up a model in order to analyse the experimental results and come to a positive result.

You need to consider the kinetic energy he tool has when it impact and how much was transferred to deform it.