energy from crush deflection(indentation)

[domtar83]

I'm trying to determine to energy absorbed by the end of a log impacting a stationary object.

by conservation of energy: Ein = Elog + Eobject +Ecrush

Ein =.5mv^2
Elog = .5mv^2 (assumed as zero, impact comes to a stop)
Eobject = .5kx^2 (spring constant determined from force on the object(cantilever beam))


How do I determine the crush energy??
The log is traveling horizontally at 300fpm, weighs 3500 lbs, and is 25inches in diameter. The estimated are of contact is maybe 3% the area of the log end.

 

[GregLocock]

Draw the mechanism of hinges in the plate or beam that is deforming plastically. Work out the enegry absorbed in each hinge as it rotates, using the moment of plasticity of the section.

If on the other hand the log is pounching a hole in the plate then it is easier, as the military know a lot about it, and more difficult becasue the beahviour of a hardened steel sheel is unlikely to be the same as a lump of wood.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[IRstuff]

As usual, you need either the impact time or the crush distance.

TTFN

FAQ731-376

 

[rb1957]

though it doesn't help any ... Ecrush would be the strin energy absorbed by the structure.

then you also have lost energy (noise ?)