Using "target values" to work back the final strcuture? 1

[Averat]

From recent chat with a fellow engineer, he mentioned that some of the coolest structures (organic shapes) today are designed with the method "target values." In theory, it defines the ultimate stresses and deformation loads, then works back to the final structure. It is different from the conventional practice of using X,Y,Z load combinations and then optimize the structure.

Anyone knows where I can get more info. on this subject? Is this a method you used? May you share?

Thanks!

 

[Lion06]

I would be interested how you arrive at a "target value" for stresses and loads without first defining loading and using load combinations.

 

[GregLocock]

Yes, it is called structural optimisation. You define a max allowable stress, and the location and magnitude of each load and constraint, and the allowable envelope of material.

Model all that up in a competent FEA optimising package, press the go button, wait for the answer to pop out. The quality of the result depends largely on the quality of the analyst.

Used all the time in the automotive industry.

http://www.dta.com.tr/pdf/ford_bracket.pdf

for a very unsexy example



Cheers

Greg Locock

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

 

[msquared48]

Structural optimization programs have been around since I was in college - over 40 years. Nothing new, just a different wrapper.

Was this developed in China as a form of reverse engineering?

Mike McCann
MMC Engineering

 

[GregLocock]

There's a couple of other non computer based techniques that produce fairly organic shapes - membrane theory, in which you apply point loads to a stretched rubber sheet, which then deforms so that the loads are taken in tension rather than bending, and the old strings and weights methods used by gothic cathedral designers, and I think Gaudi.

There's also a theorem that says if you know what your loads are and you know the material properties, and a few other things, then you can work out the minimum volume of structure that is possible. That's all I know about that. It sounds like some sort of virtual work calculation.



Cheers

Greg Locock

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