FE Model of a cockpit door window

[giusydeno]

Hello!

Iam a stress engineer and I am modeling the cockpit door of an helicopter. I need to include the window in my model as structural. I think that the best way to connect the window surface with the main door structure is with bush elements (that can simulate the window seal). Could you give me an advice? Is that the correct way? And what value for the bush spring constants do I have to use?

Thank you very much

 

[rb1957]

why model the window pane ? is it attached to it's surround in a way that allows it to react load ? you could check later to see if the deformed shape of the surround has made the window pane contact the surround. you could apply pressure loads (if required) around the edge of the cut-out.

 

[mullins]

I agree with rb1957.

Glass is technically a liquid in the molecular level; meaning that it does not have an ordered molecular structure. So including in a FEA model can work out to be a nightmare.



Taking the science out of rocket science...One step at a time.

 

[40818]

I think it would be better to not model the glass. What are your reasons for doing so??

 

[GregLocock]

"So including in a FEA model can work out to be a nightmare.
"

Oh well, that must explain the problems we have with modelling car bodyshells, where the glass is a substantial proportion of the weight and stiffness.

Not.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[SWComposites]

Back to the OP: how is the window connected to the door structure? bolts, bond, clips, ?

If it is some sort of elastomeric joint, then you may need some test data of the joint in order to determine the correct spring stiffness; and it may be a non-linear response. Otherwise, run the FEM with a wide range of stiffness values and see what the effect is on the structure's deformation and stresses.

 

[giusydeno]

I need to consider the window structural because I have significant airloads pressure on it. The window is connected to the main structure by a rubber seal.

 

[GBor]

You don't have to consider the window. RB eluded to the method. Calculate the area of the window. Multiply times the pressure to get pounds. Divide by the perimeter of the window to gets pounds per inch and distribute that load evenly along the perimeter.

 

[rb1957]

we're focusing on the door structure. you may be more interested in the window itself (maybe it isn't qualified by the vendor so you have to substantiate it yourself).

I'd deal with the door structure as posted above; the door is going to feel the point loads around the perimeter of the window. This assumes that the window pane is effectively pinned into the frame.

The window pane would then be a flat, thick panel under pressure, with a pinned support at the perimeter, this should be a Roark solution.