XANSYS Message: 93190 [Go back to message list] [bookmark on del.icio.us]
No rating yet Subject: Re: [STRUC] Bonded contacts Author: Christiane Caouette Date: 2008-05-06 19:36:13Yup, that's exactly the feature I was interested in using. The only problem is that I need to know how Ansys calculates its glued contacts before I use them; there are enough ambiguous papers of hip stem models with "bonded contacts" as it is... I built a small model to experiment with that feature; just two beams of different mesh size connected with bonded contacts and a cohesive zone material model. It works great, but I need to be able to justify using it; which means explaining how they work. "Glued", meaning a rule of no relative slinding is enforced, I suppose.
Regards, Christiane
> Just out of courosity... Are you comparing a standard (frictional) > contact with a bonded(glued) > contact ? (or did i miss something along the way). > > Perhaps the de-bonding feature of a bonded contact element could help > you? > > Brgds O.E.Lindoe,ImencoAS > > ----- Original Message ----- From: "Christiane Caouette" > > To: "ANSYS User Discussion List" > Sent: Monday, May 05, 2008 10:00 PM > Subject: Re: [Xansys] [STRUC] Bonded contacts > > >> Hello everyone, >> >> Joseph: Yes, I did read section 14.174. It is very complete in almost >> every aspect of contact technology in Ansys (I must add release 11 is >> greatly improved compared to 10!). The only missing info in there is >> about contact surface behavior (bonded, standard, rough...): they only >> say that "contact points are attached" for bonded contact, whatever that >> means... >> >> Martin: You're absolutely right; I did all that testing during my >> master's... :-) . To simulate primary stability (the implant's just >> been put in, no cellular reaction yet), standard contacts did a fine job >> as long as FKN and FKT where properly set. But if I use bonded contacts >> (with penalty algorithm and same FKN/FKT), micromotions (contact sliding >> distance) drop to almost nothing. That is the behavior I need to explain >> mathematically. >> >> Paris: I had no idea LSDyna could do that sort of stuff, I will look >> into it, because damage control/induced is exactly what I need. As for >> papers on this subject, most of them focus on primary stability and try >> to reproduce lab experiments with composite femurs; there's no >> osseointegration, it's simple classic contact mechanics, so they do it >> with contact elements, most of the time not saying what values they used >> as parameters. You'll find those all over the place (just type something >> like "hip stem model"...), but primary stability is the easy part. >> >> I found only a couple of papers dealing with osseointegrated implants: >> the most interesting is a series of paper by Moreo and Doblaré. They use >> what they call an "interface element", but I think they programmed it >> themselves, it has little to do with Ansys inter20X elements. It's based >> on the same principles, but they use the damage variable d as a bonding >> degree, with their own behavior law (I can only use bilinear or >> exponential models in Ansys). >> >> So, to summarize: Paris seems to have the key to my problem, I'll go >> look in LS-Dyna, and give the list an update when I know more... >> probably a couple weeks from now! >> >> Thanks everyone! >> Christiane Caouette >> PhD Student at École de Technologie Supérieure >> >>> Hi Christiane, >>> If ANSYS is not an option due to limitations of its contact >>> algorithms you may want to try LsDyna that has different contact >>> types that account for separation under controlled situations. The >>> LSDyna may be an overkill but the types of contact algorithms it >>> offers are more appropriate for your type of problem. You want >>> erosion-type or damaged-induced/controlled contact resolutions that >>> I know LsDyna can help. It appears that your problem is not >>> centered in the contact interface per se but more so in its the >>> existence or absense and the effect it has to the parts at the >>> interface. >>> >>> Having said all that, I know that pretty soon I'll run into a >>> paper/work by someone in your field for the very similar problem >>> that was done in ANSYS. >>> >>> Incidentally, what is the literature search showing as far as >>> handling problems like yours ?? What other codes engineers in your >>> field use for similar problems ??? >>> >>> Regards, >>> Paris Altidis >>> Belcan Corp. >>> 630-786-0008 >>> >>> >>> >> ^-------------------------------------------------------- >> | XANSYS - www.xansys.org | >> | The Discussion List for users of ANSYS, Inc. Software | >> | Hosted by PADT - www.padtinc.com | >> ^-------------------------------------------------------- > > >
--
Christiane Caouette, ing. jr
/Doctorat Génie Biomédical/
/École de Technologie Supérieure/
/Institut des Matériaux Industriels - CNRC/
(450)641-5807
_Christiane.Caouette___at_cnrc-nrc.gc.ca_
^-------------------------------------------------------- | XANSYS - www.xansys.org | | The Discussion List for users of ANSYS, Inc. Software | | Hosted by PADT - www.padtinc.com | ^--------------------------------------------------------