FEAP User Forum

FEAP => Programming => Topic started by: OrangeDays on July 20, 2014, 08:36:51 AM

Title: How to define a Lagrange multiplier in FEAP
Post by: OrangeDays on July 20, 2014, 08:36:51 AM

Dear all,
I am now dealing with a problem in which an additional boundary condition is imposed.
To solve that I turn to use Augmented Lagrange method described in Theory manual page 97(ver 8.4).

It would be very kind if any of you can answer my questions:
1). are there predefined Lagrange multipliers, which I can use directly without adding explicitly additional degree of freedom in my user element?
2). If yes, can I define different interpolation of the Lagrange multiplier? Or, how is the multiplier is defined? Like displacements at each node?
3). If no. Since in this method an inverse of a symmetric matrix K^lambda[nel,nel] is calculated, I am not sure if there is an algorithm already implemented in FEAP so that I do not have to do the inverse of the matrix myself.

I hope I have described the problem clearly. :)

Thank you very much and best regards,
Ying

Title: Re: How to define a Lagrange multiplier in FEAP
Post by: OrangeDays on July 21, 2014, 03:28:21 AM

For the question 3), I have found the small subroutine: invert.f :)
But I am still not sure about the Lagrange multiplier...