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# NASTRAN: Restart from sol 106 into sol 103

 NicolaPalettaPhD (Aeronautics) (OP) 16 Mar 12 9:17
 Could someone explain me how can I do a restart from sol 106 into sol 103? The purpose is to calculate normal modes by using differential stiffness matrix from sol 106 but by changing buoundary conditions.In other words, I have to calculate free-free normal modes with sol 103 by using the differential stiffness matrix from sol 106. This last procedure has been used to calculate a non linear static solution with a self-balanced load condition (aerodynamic + inertial + propulsive loads) by restraining the FE model grid representative of the whole airplane center of gravity.Thanks for you help!
 BlasMolero (Mechanical) 17 Mar 12 14:08
 Hello!,With FEMAP & NX NASTRAN SOL 106 you have an easy way to perform modal analysis with pre-load. The key is to put the METHOD command in the case control and put an eigenvalue card, such as EIRGL, in the bulk data session. Also, param LGDISP needs to be specified to compute the differential stiffness, and NMLOOP should be a value not equal to zero so that the normal modes are computed based on the updated non-linear stiffness.Here is an example: Normal Mode Analysis with Preload - Solution 106$Note that LGDISP = 1 is set to get differential stiffness matrix$ case control METHOD = 10 calls eigenvalue module$SOL 106$CEND$TITLE = Normal Modes with PreloadSUBCASE 1 NLPARM = 1 LOAD = 1 METHOD = 10 SPC = 100 DISPLACEMENT = ALL$BEGIN BULK$$------8-------8-------8-------8-------8-------8-------8-------8-------8-------8$$  Param Cards$PARAM WTMASS 0.00259PARAM COUPMASS 1PARAM POST -2$$NodesGRID 1 0 0. 0. 0.GRID 2 0 10. 0. 0.GRID 3 0 20. 0. 0.GRID 4 0 30. 0. 0.GRID 5 0 40. 0. 0.GRID 6 0 50. 0. 0.GRID 7 0 60. 0. 0.GRID 8 0 70. 0. 0.GRID 9 0 80. 0. 0.GRID 10 0 90. 0. 0.GRID 11 0 100. 0. 0.$$ Bar Elements$CBAR           1      11       1       2      0.      1.      0.CBAR           2      11       2       3      0.      1.      0.CBAR           3      11       3       4      0.      1.      0.CBAR           4      11       4       5      0.      1.      0.CBAR           5      11       5       6      0.      1.      0.CBAR           6      11       6       7      0.      1.      0.CBAR           7      11       7       8      0.      1.      0.CBAR           8      11       8       9      0.      1.      0.CBAR           9      11       9      10      0.      1.      0.CBAR          10      11      10      11      0.      1.      0.$$Bar PropertiesPBARL 11 12 I ++ 2. 1. 1. .1 .1 .1$$ Material Properties$MAT1 12 1.0E+7 .33 .101$$RestraintsSPC1 100 345 1 THRU 11SPC1 100 1234 1SPC1 100 234 11$$------8-------8-------8-------8-------8-------8-------8-------8-------8-------8$$EIGRL Card for Eigenvalue SpecificationEIGRL 10 3$$ PARAM Cards: LGDISP & NMLOOP$PARAM      LGDISP       1PARAM      NMLOOP       5$$NLPARM CardNLPARM 1 5 AUTO 5 25 PW NO++ 0.001 1.0E-7$$  FORCE Card$FORCE 1 11 0 500. 1. 0. 0.$               \$ENDDATABest regards,Blas. ~~~~~~~~~~~~~~~~~~~~~~Blas Molero HidalgoIngeniero IndustrialDirector IBERISA48011 BILBAO (SPAIN)WEB: http://www.iberisa.comBlog de FEMAP & NX Nastran: http://iberisa.wordpress.com/
 NicolaPalettaPhD (Aeronautics) (OP) 19 Mar 12 4:23
 Thank you for the answer Blas.I did as you suggest in the first time, but the problem is that this approach does not let me change the boundary conditions. More in details, I have to remove the constraint used for running the sol 106. I need to calculate normal modes for an unrestrained condition.thank you again.Best regardsNicola

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