tag:blogger.com,1999:blog-5791588710449126240.post3585110276534916561..comments2024-03-16T07:33:01.532+00:00Comments on Geometry Gym: Nurbs To Structural Analysis ProfileJon Mirtschinhttp://www.blogger.com/profile/09698974959593709039noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-5791588710449126240.post-37541585948182959302012-01-24T18:56:08.840+00:002012-01-24T18:56:08.840+00:00For solid sections (with or without openings) most...For solid sections (with or without openings) most FE modellers calculate the torsion constant using the Prandtl membrane analogy, i.e. solving Poisson's differential equation, and they most often calculate this using the finite difference method.<br />Might be worth taking a look at this article for some comments on the 'physical analogy':<br />http://web.mit.edu/course/3/3.11/www/modules/torsion.pdf<br /><br />For thin-walled sections it's a fair bit easier to calculate (at least approximately). In summary for solid shafts you can use membrane analogy fairly readily, for closed thin-walled sections, a shear flow analogy is most useful, but for the generic section FEM is really the only way to do it... but actually not that hard to implement and calculate I wouldn't imagine.<br /><br />And this article provides an excellent summary of dealing with torsion in structural analysis including all the theory and background with lots of good references.<br />http://people.virginia.edu/~ttb/torsion.pdfLuke Eppnoreply@blogger.comtag:blogger.com,1999:blog-5791588710449126240.post-65830837628989532862011-12-01T09:06:13.118+00:002011-12-01T09:06:13.118+00:00I had a look at http://en.wikipedia.org/wiki/Membr...I had a look at http://en.wikipedia.org/wiki/Membrane_analogy.<br />Are we looking at finding the surface for a given (constant) pressure?<br />You can approximate solutions to Airy functions using NURBS for example, would that help?Kristoffer Josefssonnoreply@blogger.comtag:blogger.com,1999:blog-5791588710449126240.post-60058278544314143952011-12-01T05:54:29.952+00:002011-12-01T05:54:29.952+00:00Hi,
Thanks for the suggestion, but we're look...Hi,<br /><br />Thanks for the suggestion, but we're looking for a soap film (inflation) surface. Google for Prandtl, something like this:<br />http://www.public.iastate.edu/~e_m.424/Prandtl%20torsion.pdfJon Mirtschinhttps://www.blogger.com/profile/09698974959593709039noreply@blogger.comtag:blogger.com,1999:blog-5791588710449126240.post-78885865879969899082011-12-01T04:21:15.528+00:002011-12-01T04:21:15.528+00:00Are you looking into methods of calculating a mini...Are you looking into methods of calculating a minimal surface for a given polygonal boundary?<br /><br />There is a nice algorithm in<br />Pinkall, Polther: Computing discrete minimal surfaces and their conjugates :<br /><br />http://projecteuclid.org/euclid.em/1062620735<br /><br />I'm not exactly sure how you get the torsional stiffnes from the actuall minimal surface though.Kristoffer Josefssonnoreply@blogger.com