sfepy/sfepy — Issue #49: stress recovery
Author: rc
Created: 2012-01-30 10:24:50+00:00
State: open

Implement stress (or any other quantity computed in quadrature points)
extrapolation into mesh nodes. Useful e.g. for boundary integrals.

see Introduction to FEM
(http://www.colorado.edu/engineering/CAS/courses.d/IFEM.d/), chapter 29

Migrated from http://code.google.com/p/sfepy/issues/detail?id=45

earlier comments

robert.cimrman said, at 2010-04-20T09:15:02.000Z:

This could be, in fact, easily achieved by defining a custom integral with quadrature
points coinciding with the mesh nodes:

from sfepy.fem.geometry_element import geometry_data
gdata = geometry_data['3_8']
nc = len(gdata.coors)

integrals = {
'ivn' : ('v', 'custom', gdata.coors, [gdata.volume / nc] * nc),
}

...

and then evaluate:

stress = problem.evaluate('dq_cauchy_stress.ivn.Omega( m.D, u )', state)

Then you can choose whether to average somehow the stresses in each node, or not.

This example needs the current github repo version, as it uses short syntax for
custom integrals, and the volume attribute of geometry_data. Of course, you can use
long syntax, and provide your own coordinates and weights.

If the example above resolves the issue, close it, please.