Optimization Methodology

[Ing.marco.soave]

Good morning. I have a question about the Margin of Safety.

I want analyze a simple flat simply supported plate with these features:

a=b=500 mm
Unstiffened Family
Compression load provided directly by FBD tab (300 N/mm (Nx)).

I've edited a materials which has these features:

Isotropic
E = 210 GPa
G = 80.769 GPa
nu = 0.3
Allowable stresses = 100 Mpa and In-plane Fsu = 50 Mpa

I've correctly set the ultimate factor to 1.0 and i've analyzed my simple model. The margin of safety for Isotropic Strenght is 0.2396. Is there a possibility to set it to zero and check the variables by taking into account that i want this specific margin of safety? Or in other words in which particular way Hypersizer chooses the minimum positive Margin of Safety?

Maybe by improve the permutations number i can obtain a MoS nearest to zero?

Thanks a lot for any answer!

[James]

HyperSizer will optimize the plate thickness so the Minimum Margin of Safety is over the required value (by default = 0). The minimum margin of safety is evaluated from all active failure methods. So if you want to determine the plate thickness that will return a Margin of Safety near zero for material strength, activate only that analysis.

Also increasing the permutations will increase the number of candidates HyperSizer can try during an optimization, so this usually returns panel designs with margins of safety closer to zero. If you increase the permutations, make sure you are not hitting the minimum thickness bound, that is make sure the optimum candidate number > 1.

HyperSizer's optimization methodology is explained in more detail in our online help system: http://hypersizer.com/help/Content/Optimization/optimization_overview.php

There is also a section on setting the required minimum margin of safety: http://hypersizer.com/help/Content/Form-Sizing/HowTo/fail-setting_required_ms.php