## Plate Deflection Formula Question

## Plate Deflection Formula Question

(OP)

Hello,

I'm a hobbiest, not an engineer, and I need some help. I want to calculate some plate deflection numbers on circular plates using excel. I know there are on-line calculators that will do it, but I want to keep it in excel. So, my copy of Machinery's Handbook gives the following 2 formulas.

Stress = 0.39 * W / t^2

deflection = 0.221 * W * R^2/ E * t^3

I had no problems setting up both formulas. I can look up Poisson's ratio (0.39), and the other values are either known from the material or computed.

But I have no idea where the 0.221 comes from!! Google found me a couple of examples of the formula, and the value used in place of 0.221 varies with the plate material. Could someone tell me how to find it? Look it up - where? Calculate it - what's needed?

Thanks,

Alex

I'm a hobbiest, not an engineer, and I need some help. I want to calculate some plate deflection numbers on circular plates using excel. I know there are on-line calculators that will do it, but I want to keep it in excel. So, my copy of Machinery's Handbook gives the following 2 formulas.

Stress = 0.39 * W / t^2

deflection = 0.221 * W * R^2/ E * t^3

I had no problems setting up both formulas. I can look up Poisson's ratio (0.39), and the other values are either known from the material or computed.

But I have no idea where the 0.221 comes from!! Google found me a couple of examples of the formula, and the value used in place of 0.221 varies with the plate material. Could someone tell me how to find it? Look it up - where? Calculate it - what's needed?

Thanks,

Alex

## RE: Plate Deflection Formula Question

It's been a number of years since I did in depth DE solutions, but I seem to recall that the only plate with an exact DE solution is triangular (the bi-harmonic equation?), so any other shape will be an approximate solution, reduced to a relatively simple algebraic formula, such as what you are using.

## RE: Plate Deflection Formula Question

But my question is, where can I find this value? The MH example I had above is for steel. I found another example for lexan and the value was 0.0284. It seems there should be a table or something with this value, that's what I'm looking for.

Alex

## RE: Plate Deflection Formula Question

Alex

## RE: Plate Deflection Formula Question

So it sounds like your curiosity helped both you and them. :)

## RE: Plate Deflection Formula Question

Quando Omni Flunkus Moritati