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Subject: Re: [STRUCT] Contact_ A hollow semi-sphere pressed on to
Author: Paris Altidis
Date: 2008-04-09 16:58:51

Hi Mehmet,
The FKN is an artifact in the whole contact resolution. We (all ANSYS users) spend an ungodly amount of time messing w/ FKN and the other parameters to get the models to converge. It is a step that we all dread but must take.
You mentioned that the contact pressure at the interface is not too good. To get an exact (or close to) value you need a very fine mesh in the tip area.
The pure lagrange algorithm that you use guarantees a zero penetration and in the process does not need the FKN. Instead, it requires chattering control parameters, FTOLN and TNOP, as well as the maximum allowable elastic slip parameter SLTO. See the Documentation for Keyopt(2) settings.

I noticed that you constrained all the nodes of the workpiece in 5 directions but the line D, ALL, ALL, 0 says differently. The documentation mentions that the the contact nodes should not be constrained. See TFM for this note (under specifics for Keyopt(2):
""When using these options, be careful not to overconstrain the model. The model is overconstrained when a contact node has prescribed boundary conditions, CE and CP equations. ANSYS usually detects and eliminates the overconstraints. However, there is no guarantee that the program will eliminate all the cases of overconstraint. You should always verify your model carefully to address this issue."

Regards,
Paris Altidis
BELCAN Engineering Group
Adv. Engineering & Technology Division
630-786-0008
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-----Original Message-----
From: xansys-bounces_at_xansys.org [mailto:xansys-bounces_at_xansys.org] On Behalf Of Mehmet
Posts possibly associated with message #92762AuthorDateScore
92753Re: [STRUCT] Contact_ A hollow semi-sphere pressed on to theDan Bohlen2008/04/09 
92760Re: [STRUCT] Contact_ A hollow semi-sphere pressed on to the=?ISO-8859-1?Q?Mehmet_=D6te?= 2008/04/09 
92762Re: [STRUCT] Contact_ A hollow semi-sphere pressed on toParis Altidis2008/04/09 
92763Re: [STRUCT] Contact_ A hollow semi-sphere pressed on to=?ISO-8859-1?Q?Mehmet_=D6te?= 2008/04/09 
92764Re: [STRUCT] Contact_ A hollow semi-sphere pressed on toParis Altidis2008/04/09 
92765Re: [STRUCT] Contact_ A hollow semi-sphere pressed on toFernand Thomassy2008/04/09 
92769Re: [STRUCT] Contact_ A hollow semi-sphere pressed on to=?ISO-8859-1?Q?Mehmet_=D6te?= 2008/04/09