Metal Grid Stiffened Plugin

[andrew.hemsley2]

When the Metal Grid Stiffened Plugin is read into a database, new user defined failure criteria are created for the stringer and skin segments. Does this mean the old failure criteria are obsolete for sizing and so should be deselected? (I’ve noticed the Margins of Safety for the old criteria are unchanged whether the single-sided or cruciform section options for the stiffener are chosen.)

[Brent]

User constants defined on components only effect the plugin criteria. If a stringer segment is assumed to be a cruciform design and the "Is cruciform?" user constant is set to "True", then the HyperSizer "old"/"native" failure criteria margins are not valid for the assumed design. Since the component is likely assigned a single sided blade concept on the dimensions tab, all of the native failure criteria will use design-to-loads computed for that component concept cross section.

We suggest to deactivate all HyperSizer native failure criteria on both the skin and stringer segment components which have the "Is cruciform?" user constant set to "True". The Metal Grid Stiffened Plugin performs its own load summation and section property calculations that feed into the failure criteria contained in that plugin.

Hope this is helps!

[andrew.hemsley2]

Thanks for your reply Brent. I have two further questions:
(I) Am I correct in assuming that the Nastran deck output by hypersizer needs to be edited to remove CBAR offsets for elements  that have “Is Cruciform?” set to True? Presumably, if using HyperFEA, this would require a script to remove offsets for selected CBARs prior to each Nastran analysis. (I am aware that there is a Backdoor option to remove all offsets, but in a model containing single sided and double sided stiffeners, the offsets need to be removed for selected elements only.)

(ii)Does the “Is Cruciform?” have to be applied to the panel components as well? If it does, then I assume all the stringer segments bounding a panel have to have the same “Is Cruciform?” setting as the panel and a mixture of blade and cruciform stiffeners in a panel would not be possible.