[MBDyn-users] Beam strain gauge

Pierangelo Masarati masarati at aero.polimi.it
Sat Mar 22 11:58:58 CET 2008

Alessandro Fumagalli wrote:

> can anybody show an example of how to use a beam strain gauge parameter node?
> The manual gives only the definition, does it need to be "binded" in some
> way? Or it just needs to be defined?

In fact, the documentation seems to be quite incomplete for this type of 
parameter.  You need to:

- define a parameter node of type "beam strain gage", with the y and z 
coordinates of the point in the beam's section with respect to the 
reference system of the beam's constitutive properties.  As a 
consequence of this, the (axial) strain will be computed as

	epsilon = nu_x - y * kappa_z + z * kappa_y

where nu_x is the axial strain of the beam and k_y and k_z are the 
bending curvatures about the y and z axes respectively.  For example:

begin: nodes;
	# other nodes...
         parameter: STRAIN, beam strain gage, .01, .02;
end: nodes;

- define the beam element

- after the beam element, bind it to the parameter node, indicating 
whether the strains should be evaluated in the first or in the second 
evaluation point (the collocation points) if dealing with a 3 node beam. 
  For example:

         bind: BEAM, beam, STRAIN, 1;

I'm attaching a full example.  I'm also updating the documentation to 
reflect this; please report in case of problems.

Ciao, p.

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