Determining stress induced in a plate by impact from a sphere

[eshimek]

I am trying to take the parameters of a falling ball of ice that is impacting an A36 steel pinned sheet and theoretically determine the amount of stress experienced by the sheet. More specifically, I am trying to determine a relationship between velocity and radius of the ball that would just reach the modulus of resilience of A36 steel.

I realize I could run hundreds of simulations on LS-DYNA and zero in on the points, but there has to be a way to solve this using the formulas they are using. I'm just not sure what they are or how to find them.

Anyone have any suggestions or happen to know such a formula that could be used?

Thank you in advance.

 

[MiketheEngineer]

Impact loads have been discussed thoroughly on this site - just search for them.

Basically it is NOT simple - you have to determine how fast the ball de-accelerates - time or distance. Then F=ma.

Finding the "a" is the problem....

In the case of an ice ball - you might also have a "shrinking" M??

 

[GregLocock]

I think you'll get completely different problems to solve if you are dropping a cannonball sized ice ball onto the roof of a car, compared with a hailstone hitting a 5 inch slab of cast iron. It sounds more like the first case which is good, as the most significant stiffness is the membrane stiffness of the plate. So work out that stiffness and solve in the usual fashion.

In practice that will be an overestimate of the stresses because the ice ball will fall apart absorbing some of the enrgy.



Cheers

Greg Locock


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

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