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No rating yet Subject: Re: [STRUC] Bonded contacts Author: Paris Altidis Date: 2008-05-05 02:01:52Hi 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
-----Original Message----- From: xansys-bounces_at_xansys.org on behalf of Christiane Caouette Sent: Sat 5/3/2008 5:47 PM To: ANSYS User Discussion List Subject: Re: [Xansys] [STRUC] Bonded contacts
Hello Bram,
I've been through it already; it doesn't say how exactly the contacts remain bonded, regardless of the algorithm I choose. I'll give you a little more context, you'll see my real problem. I'll be modeling hip implants in my thesis, which means there will be bone-implant or bone-cement interfaces. These interfaces change with time (osseointegration occurs, securing the implant, or ostelysis, which loosens it), and these changes can be approximated with damage mechanics: hence, bonded contacts with a cohesive zone material. The only problem with that technique is that interface micromotions (contact sliding distance) are a key parameter in determining what happens at the interface, so I can't afford to use bonded contacts as a black box, I need to know what they do.
The other contact parameters I will have to use are: penalty or Augmented Lagrangian (they give the same results on my models) with user-defined stiffness. MPCs are out of the question, I need friction in there.
So, the trouble is not how to use them so much as how do I justify using them if I don't know what they do...
Thanks for trying! Christiane
PhD Student at Ecole de Technologie Superieure
Weisman, Bram wrote: > I don't know how much help this will be, but I would recommend you read > the on-line documentation "Contact Technology Guide" in it's entirety. > Along the way you should find some clues. Be aware that there are > several algorithms to choose from when doing bonded contact, some are > stiffness and/or penalty function based, and others are constraint > equation based (MPC). > > Best regards, > > Bram Weisman, P.E. > Overcoming ANSYS deficiencies since 1998. > > > SBM Atlantia > Suite 400 > 1255 Enclave Parkway > Houston, TX 77077-1608 > > This message is not provided as an SBMA employee. > > > "The reasonable man adapts himself to the world; > the unreasonable one persists in trying to adapt > the world to himself. Therefore all progress > depends on the unreasonable man." > - George Bernard Shaw > > > > -----Original Message----- > From: xansys-bounces_at_xansys.org [mailto:xansys-bounces_at_xansys.org] On > Behalf Of Christiane Caouette > Sent: Friday, May 02, 2008 2:02 PM > To: xansys_at_xansys.org > Subject: [Xansys] [STRUC] Bonded contacts > > > Hello everyone, > This is my first post; I hope I have done everything properly... > My question is about bonded contacts: I have looked everywhere I > could > think of (ansys help, google, library...), but I haven't been able to > find the mathematical description of these elements, only that of > standard contact elements. So what does Ansys do to keep those bonded > elements from opening? Is it a restriction on allowed nodal > displacement? Like, they can't move out of the pinball region, or > can't > move relative to one another (target nodes vs contact nodes)? > If anyone has any suggestions (or references I could check) to shed > some light on this... thanks! > Christiane Caouette, jr eng. > PhD Student at Ecole de Technologie Superieure > > > ^-------------------------------------------------------- > | XANSYS - www.xansys.org | > | The Discussion List for users of ANSYS, Inc. Software | > | Hosted by PADT - www.padtinc.com | > ^-------------------------------------------------------- > > ^-------------------------------------------------------- | XANSYS - www.xansys.org | | The Discussion List for users of ANSYS, Inc. Software | | Hosted by PADT - www.padtinc.com | ^--------------------------------------------------------
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