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The problem I'm doing invovles electro-mechanical coupling. I have another thread which describes the problem in a little detail: http://www.eng-tips.com/viewthread.cfm?qid=137630&page=3

Thank you for all the discussions! My problem is that the finite element program will converge, however, to the wrong solution if I use the nonlinear tangent matrix. If I use the linear matrix, the program will converge to correct solution. So the problem has to be with my tangent formulation...

Thanks, EricZhao! I now think it may not be the nonsymmetric problem. It may be the numerical error that cause the results to be incorrect. I doubt that globally the solution converges though locally the error stacks. Don't know what to do now. Sigh!

Hi all, I am doing some nonlinear analysis using consistent tangent matrix. I did uniform traction tests found that the results are not homogeneous even though the finite element solution (global solution) converges very well. However, if I do not use the linear stiffness matrix instead of...

I'm developing finite element program myself for the research. We used the skyline storage for the system matrix. Now the new stiffness matrix is unsymmetric and all the solver I can find is for symmetric matrix. Could anyone tell me where I can find the program with skyline storage scheme to...

Sorry. The greek characters can not be displayed. I have to make changes and post it again. The consitutive relationships are plasticity like: sigma=C:(eps-epsr)-h:(D-Pr) (1) E=-h:(eps-epsr)+b:(D-Pr) (2) sigma-stress...

Thank you EricZhao! I will try to demonstrate the problem. I hope I can make it clear. The consitutive relationships are plasticity like: ?=C:(?-?r)-h:(D-Pr) (1) E=-h:(?-?r)+?:(D-Pr) (2) ?-stress, E-electric field...

I am developing a nonlinear finite element program for the response of ferroelectric materials. Due to the electro-mechanical coupling, the nonlinearity is material nonlinear. I derived the consistent tangent stiffness matrix and are trying to test it. Three tests were carried out on a...