Stiffness of plate arrayed with holes?
Stiffness of plate arrayed with holes?
(OP)
I'm trying to determine the stiffness of a perforated plate 25mm thick arrayed with through holes 1.7mm dia on a 4.5mm horizontal and vertical pitch. The holes are in a square array (not honeycombed.
I've found data on perforated sheet but not thick plate.
Anyone out there had a similar problem?
Justin





RE: Stiffness of plate arrayed with holes?
Just discount E (or G) by the lost volume of steel. So if you drill out 30% of the metal, drop E by 30%
Second thought: that is not a conservative solution, your square array makes things worse by defining hinge lines. Analsyse each hinge, and the intervening strip.
Sorry, that's as far as I got!
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Stiffness of plate arrayed with holes?
For your geometry, the ligament efficiency of the square pattern is η=(p-d)/p=0.622, and
E*/E=0.74
ν*=0.29
These are graphically determined on a chart, unfortunately there is no interpolating formula.
Note that the elastic modulus is somewhat smaller than what was suggested by GregLocock: his method is in fact correctly applicable to (bending) stresses, more than to stiffness.
Here TEMA may help: they define an efficiency to bending stresses as η=1-0.785d2/p2 that is exactly the solid to unperforated area ratio (the formula is for a square pattern, but for a triangular pattern another formula gives again the area ratio).
prex
http://www.xcalcs.com
Online tools for structural design
RE: Stiffness of plate arrayed with holes?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Stiffness of plate arrayed with holes?
Download the designer's handbook there is information on what you want.