Many thanks for the kind advice. I checked the results from facetshell solver, its results match with comercial software.
Do you know how can use the facet shell for harmonic analysis? I used the attached sif file trying to analysis an plate under harmonic forces (applied through loads), but the results are all zero.
mika wrote: ↑27 Aug 2020, 17:25 There exists an old and undocumented facet shell solver (FacetShellSolve) which utilizes drilling DOFs. While it's known that the facet shell elements may generally be unreliable (no convergence to solutions which a proper shell theory predicts, which gave a motivation to write a new shell solver), in the case of geometries consisting of just planar patches good results might however be possible (convergence failure needs a curved mid-surface).
I checked the first eigenvalues of a beam which has an L-shaped cross section and which is fixed at one end by using a facet shell model
facet-L.png
and a 3D solid model
solid-L.png
The solid model gives
EigenSolve: Computed 10 Eigen Values
EigenSolve: --------------------------------
EigenSolve: 1: 1.319919E+03 0.000000E+00
EigenSolve: 2: 4.496784E+03 0.000000E+00
EigenSolve: 3: 5.081996E+04 0.000000E+00
EigenSolve: 4: 5.499638E+04 0.000000E+00
EigenSolve: 5: 1.509114E+05 0.000000E+00
EigenSolve: 6: 3.854250E+05 0.000000E+00
EigenSolve: 7: 5.035877E+05 0.000000E+00
EigenSolve: 8: 8.492267E+05 0.000000E+00
EigenSolve: 9: 1.406722E+06 0.000000E+00
EigenSolve: 10: 1.531419E+06 0.000000E+00
EigenSolve: --------------------------------
while the facet shell solver outputs
EigenSolve: Computed 10 Eigen Values
EigenSolve: --------------------------------
EigenSolve: 1: 1.216743E+03 0.000000E+00
EigenSolve: 2: 4.464833E+03 0.000000E+00
EigenSolve: 3: 4.679074E+04 0.000000E+00
EigenSolve: 4: 5.240912E+04 0.000000E+00
EigenSolve: 5: 1.466158E+05 0.000000E+00
EigenSolve: 6: 3.541928E+05 0.000000E+00
EigenSolve: 7: 4.769901E+05 0.000000E+00
EigenSolve: 8: 8.113645E+05 0.000000E+00
EigenSolve: 9: 1.278976E+06 0.000000E+00
EigenSolve: 10: 1.411605E+06 0.000000E+00
EigenSolve: --------------------------------
There seems to be quite good agreement of the eigenvalues, so perhaps you could try a facet model for a box. For an example case in the tests directory see the test FacetShell2.
-- Mika