Projection to nodes

[tseeriksson]

Hello!

I am looking for a simple way of projecting a vector which I have at every quadrature point to the nodes (for post processing). Is there a straight-forward way of doing that in FEAP 8.3?

Thank you!
Thomas

[luc]

You can use the STRE,NODE command to project quantities from gauss points to the nodes.
If you program an element then you need to provide the element computation of the lumped mass matrix and the integral of the quantities to be projected when FEAP calls the element subroutine with isw.eq.8

For all purposes, you should read the programmer manual p.50!

Best,
Luc

[Prof. R.L. Taylor]

There are several ways to project, generally for stress we use a very simple "lumped mass" type least squares projection.  It is simple but not fully accurate near the boundary.  A better way is a local least squares.  Do least squares on each element to get values to element nodes, then average.  See paper in CMAME, vol 213-216, pp 84, 2012.  We have not test on vectors, but it should give reasonable performance for each component.  If you have a constraint such as vectors being unit there will be an error.

To implement in feap you can use an element option not currently used (see attached files for simple example on how to loop over elements -- check that arguments on routine are same number as in your version).  Note files are not complete but give an idea on where to do things in the element routine.