4. B modeling#
4.1. Numerical and experimental models#
The models are identical to the case of modeling A.
4.2. Expansion base#
The expansion base is obtained with the MODE_STATIQUE operator. Theoretically, it is necessary to create the deformations associated with the experimental degrees of freedom, i.e. choose the nodes placed at the level of the measurement points.
Here, the measurement points do not correspond to nodes defined on the numerical model. Two solutions are proposed:
Short node list: for each experimental node, we chose a node from the numerical model that is closest; the correspondence between the nodes of the two models in the calculation report of PROJ_MESU_MODAL,
In the same way, a long list is defined, which contains all the nodes located near the measurement nodes; the static modes from this list are however redundant for solving the opposite problem: in this case, the opposite problem is incorrectly posed, and it is necessary to regularize it, using the keywords EPS, REGUL and COEF_PONDER in MACRO_EXPANS; by default, the list is in comment.
4.3. Tested sizes and results#
Some differences should be noted between the results of modeling A and B. The expansion base is the basis for static modes. It should be noted that these are defined (with the operator MECA_STATIQUE) on a stiffness matrix for which the degrees of freedom corresponding to the static readings are embedded. It is therefore not the same NUME_DDL as for digital modes: we cannot therefore compare extended modes and numerical modes by MAC criteria (the latter are therefore not even calculated). A comparison of the experimental modes with respect to the extended/reprojected modes is therefore carried out.
The static expansion base is not of very good quality, the orthogonality of the extended modes is not achieved. It is not tested here.
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Matrix obtained by MAC_MODES |
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We check that the MAC diagonal between extended modes and digital modes is close to 1.
For each of the terms of the diagonal (21 modes in all), the following test is carried out:
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Matrix obtained by MAC_MODES |
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