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MSC.Nastran 2004 New Features in Dynamics

MSC.Nastran 2004 New Features in Dynamics. Mike Reymond. Summary of New Features in Dynamics. Initial conditions in linear transient analysis Restarts in linear transient analysis Residual Vectors Enforced Motion Modal Strain and Kinetic Strain Energies Modal Contribution Fractions

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MSC.Nastran 2004 New Features in Dynamics

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  1. MSC.Nastran 2004 New Features in Dynamics Mike Reymond

  2. Summary of New Features in Dynamics • Initial conditions in linear transient analysis • Restarts in linear transient analysis • Residual Vectors • Enforced Motion • Modal Strain and Kinetic Strain Energies • Modal Contribution Fractions • Fast MAX/MIN Search of Output results in linear transient analysis • Alternative time delay and phase angle specification

  3. Summary of New Features in Dynamics • Improved Mode Selection in Modal Forced Response Analysis • Random Response Analysis • Miscellaneous • SSSAlter Migration

  4. Initial Conditions in Linear Transient • Initial conditions in linear transient analysis (SOLs 109 and 112) is enhanced to include: • User-specified initial conditions • Initial conditions may be specified either in physical coordinates or in modal coordinates • Computed initial conditions • Computed static solution can be used as the initial condition in linear transient analysis for both direct and modal solutions

  5. Initial Conditions in Linear Transient The following example uses the static solution from Subcase 100 as initial condition including the effect of differential stiffness SUBCASE 100 LOAD = 1000 $ SUBCASE 200 IC(STATSUB,DIFFK) = 100

  6. Restarts in Linear Transient Analysis • In V2001, restarts in linear transient analysis (SOLs 109 and 112) can only be done using SSSAlters • dtranra – direct transient • mtranra – modal transient • In V2004, you may restart to continue a linear transient analysis execution from • Last time step of a previous execution • Any earlier output time step of the previous execution • Similar to SOL 129 restart

  7. Restarts in Linear Transient Analysis • How to use in MSC.Nastran 2004: • In cold start run save database with scr=no on command line • In restart run: • Insert “PARAM,STIME,x” in restart run, where x is the time the run will continue • No model or boundary condition changes in restart run • Modifications to the DLOAD and TSTEP entries are allowed • Use the “/” command to delete unwanted items from the cold start run

  8. Residual Vectors • Residual Vectors in V2004 • Are the default in V2004 except for system modes in SOL 103 • Inertia relief with Auto Support is included by default in other words, no SUPORT entry is required for free-free models • More efficient and more reliable • Controlled by new RESVEC Case Control command • Residual vectors can come from the following sources • Inertial forces due to rigid body motion • Applied loads • Structural, viscous, and inertial forces due to enforced motion • Forces at user specified discrete degrees of freedom (RVDOFi entries) • Discrete damping forces due to viscous elements (CDAMPi and CVISC entries)

  9. Residual Vectors • Residual vectors can be controlled with new RESVEC Case Control command: INRLOD/NOINRL residual vector due to inertia relief APPLOD/NOAPPL residual vector from applied load DMPLOD/NODMP residual vector due to viscous damping RVDOF/NORVDO residual vector using RVDOFi • A separate RESVEC command may be specified for both system and component modes

  10. RVDOF G1 C1 G2 C2 G3 C3 G4 C4 RVDOF1 C G1 G2 G3 G4 G5 G6 G7 Residual Vectors • Residual vectors generated with unit load in MSC.Nastran 2001 • Use USETi,U6 and SEUSETi,U6 • Separate entries required for each SE • These vectors are not necessarily passed downstream • Residual vectors generated with unit load in MSC.Nastran 2004 • Use RVDOF and RVDOF1 entries • Separate entries not needed for each SE. • These vectors are passed downstream

  11. Enforced Motion • Enhancement of enforced motion (SPC/SPCD method) • Revised formulation, the base motion is removed from the equation of motion and then computed w.r.t. relative motion • For the output results (DISP, VELO, etc.), the user can choose results based on the relative or absolute motion with PARAM, ENFMOTN, REL or ABS (default) • Residual vectors are recommended but less critical than in V2001 • The revised formulation gives more accurate results: • When modal damping is present • For SPCForces, MPCForces, and element forces at low frequencies • When the enforced motion of the base is very large compared to the motion relative to the base

  12. Modal Strain and Kinetic Energy • Modal strain energy and modal kinetic energy in modal frequency and modal transient analysis (SOLs 111 and 112) • Calculates the strain energy coming from each mode in the response • Supports both modal transient and frequency response analyses • MODALSE Case control command for modal strain energy • MODALKE Case control command for kinetic strain energy • Output is stored on SNRGYPLT and KNRGYPLT tables

  13. Modal Strain and Kinetic Energy • Example of modal energies in modal frequency analysis (SOL 111) SET 10 = 1.0 SET 20 = 1 MODALSE (SORT1, THRESH=0.0, FREQ=10) = ALL MODALKE (SORT2, ESORT=DESCEND, THRESH=0.0) = 20 FREQUENCY = 1.000000E+00 M O D A L S T R A I N E N E R G Y MODE NUMBER ACTUAL NORMALIZED FRACTIONAL 1 2.415431E-02 1.000000E+00 7.359713E-01 2 3.425556E-04 1.418196E-02 1.043752E-02 3 1.639720E-04 6.788520E-03 4.996156E-03 4 8.846080E-06 3.662319E-04 2.695362E-04 5 6.052715E-03 2.505853E-01 1.844236E-01 MODE NUMBER = 1 M O D A L K I N E T I C E N E R G Y FREQUENCY ACTUAL NORMALIZED FRACTIONAL 1.000000E+00 8.147641E-04 1.000000E+00 9.924864E-01 2.000000E+00 4.066131E-03 1.000000E+00 9.936854E-01 3.000000E+00 1.411670E-02 1.000000E+00 9.955438E-01 4.000000E+00 5.744822E-02 1.000000E+00 9.977741E-01 5.000000E+00 7.744190E-01 1.000000E+00 9.996839E-01

  14. Modal Contribution Fractions • Modal participation (contribution) factors • Identify the important modes that contribute the most to the total response due to the forced response analysis for both modal frequency and modal transient (SOLs 111 and 112) • In V2001, SSSAlter modconta is used to compute modal contribution factors; difficulties: • No way to control filtering or sorting of the data • Alter contains different output options, each output requires separate run • Time consuming to gather all the data necessary

  15. Modal Contribution Fractions • Modal participation (contribution) factors in V2004 • MCFRACTION Case Control command has been added to compute modal contribution factors in SOLs 110, 111, and 112 • Advantages over SSSAlter modconta : • More control over the amount of output produced ( control filtering and sorting of the data) • Reduced the computer-processing time • Should only be used for the displacement response of a selective set of grid points; I.e., MCFRACTION=ALL is not recommended • Calculations are limited by the amount of memory available to store the physical response recovery matrix • Output is stored on OMCFRAC table suitable for op2 post-processing • Available in residual-structure only

  16. Modal Contribution Fractions • Modal participation (contribution) factors • Sample modal frequency response solution SET 5 = 1.0 SET 10 = 101/T3 MCFRACTION ( SOLUTION = 5 ) = 10 M O D A L C O N T R I B U T I O N F R A C T I O N S GRID POINT = 101/T3, TOTAL RESPONSE (R/I) = -1.69227E+00 / 3.65119E-03, (M/P) = 1.69227E+00 / 179.88 LOAD FREQUENCY = 1.00000E+00, (SUBCASE 1, DLOAD = 15) MAXIMUM MODAL RESP = 1.69002E+00 FOR MODE ID = 2, SORTKEY = FRACTION, SORT = ABS VALUE ASCENDING, FILTER = 1.00000E-03     MODE     NATURAL    MODAL RESPONSE                      MODAL RESPONSE       PROJECTION REL.      MODAL       SCALED RESPONSE ID FREQ (HZ) REAL IMAGINARY                MAGNITUDE PHASE            MAGNITUDE    PHASE      FRACTION        MAGNITUDE 3 3.17429E+01 1.42610E-02 -8.99426E-06 1.42610E-02 359.96        -1.42610E-02 180.09 -8.42712E-03 -8.43836E-03 7 7.63429E+01 -1.65163E-02 4.32763E-06 1.65163E-02 179.98 1.65163E-02      0.11 9.75984E-03 9.77286E-03 2 9.35245E+00 -1.69001E+00 3.65586E-03      1.69002E+00    179.88 1.69002E+00      0.00 9.98667E-01      1.00000E+00

  17. Fast MAX/MIN Search of Output Results • Monitor maximums and minimums in output results (DISP, STRESS, etc.) quickly and efficiently • Only a single MSC.Nastran job execution is requiredand no intermediate storage of results • New user interface for specifying data recovery maximum/minimum monitor and output parameters • MAXMIN(DEF) Case Control Command • Defines parameters for monitoring maximums and minimums • Supports both GRIDs and Elements quantities • MAXMIN Case Control Command to request summary output • Output is stored on OMM2 table suitable for op2 file postprocessing • Available in linear transient analysis only

  18. Fast MAX/MIN Search of Output Results • Sample input data for MAX/MIN MAXMIN(DEF) DISP T1 T2 T3 MAX=4 CID=201 MAXMIN(DEF) DISP MAGT MAGR ABS=3 RMS MAXMIN(DEF) VELO (T1 T2 T3) CID=201 MAXMIN(DEF) STRESS (QUAD4 TRIA3) SX SY SXY , MAX=30 MIN=3 RMS $ SET 20 = 3 4 7 8 10 $ GRID POINT IDS SET 30 = 101 142 157 $ ELEMENT IDS MAXMIN(ELEM)=30 SUBCASE 1001 MAXMIN(GRID)=20 SUBCASE 1002 MAXMIN=NONE SUBCASE 1003 MAXMIN(GRID,NOPRINT)=ALL

  19. TLOAD1 DELAY 10 5 15 16 5 3 LOAD 0.3 100 Alternative Time Delay and Phase Angle Specification • In MSC.Nastran 2001 and prior versions • DELAY and DPHASE fields on the RLOADi, TLOADi, and ACSRCE point to the corresponding DELAY or DPHASE entry • Actual values are then specified on the DELAY or DPHASE entry. • An example of a transient load applied at grid point 16, in direction 3, with a 0.3 second delayed is shown below • DELAY and DPHASE entries are only allowed in the residual structure

  20. TLOAD1 10 15 0.3 LOAD 100 Alternative Time Delay and Phase Angle Specification • In MSC.Nastran 2004 • You can specify actual delay and phase angle values directly on the RLOADi, TLOADi, and ACSRCE entries • The same example of a transient load applied at grid point 16, in direction 3, with a 0.3 second delayed is shown below • This new method also allows the specification of the delay and phase angles on both the residual structure and superelements

  21. Improved Mode Selection in Modal Forced Response Analysis • By default all modes calculated are included in the response analysis • In V2001 only the following user parameters are available for excluding “bottom” or “top” modes only • PARAM,LFREQ,value--modes below frequency “value” are not included • PARAM,HFREQ,value--modes above frequency “value” are not included • PARAM,LMODES,number—only the lowest “number” modes are included • Similar set of parameters are available for fluid modes

  22. Improved Mode Selection in Modal Forced Response Analysis • In V2001, no standard way of deleting selective mode (e.g., unwanted local modes) except with delmodea.vxx from the SSSalter library • In V2004--MODESELECT Case Control command • Use to either: • Include a selective set of modes or • Excludes a selective set of modes

  23. Improved Mode Selection in Modal Forced Response Analysis • Note that unselected modes will not participate in the response which may lead to incorrect results if the wrong modes are deleted Examples: 1. Select all 10 modes excluding modes 6 and 7. SET 100 = 1 THRU 10 EXCEPT 6,7 MODESELECT = 100 or SET 200 = 6,7 MODESELECT = -200

  24. Improved Mode Selection in Modal Forced Response Analysis 2. Select mode 5 only. SET 100 = 5 MODESELECT = 100 or MODESELECT = 5 (No SET 5 defined) 3. Select all modes except for mode 6. SET 100 = 6 MODESELECT = -100 or MODESELECT = -6 $ (No SET 6 defined)

  25. Random Response Analysis • In MSC.Nastran 2001 and prior versions: • Auto-PSDF, auto correlation functions, and N0 (# of positive crossings) are available using the XYPLOT/XYPEAK/XYPUNCH options • In MSC.Nastran 2004: • Auto-PSDF, auto correlation functions, N0, and CRMS (cumulative root mean square) print and punch output are available on the standard Case Control commands • Available for ACCE, DISP, VELOCITY, FORCE, OLOAD, SPCF, MPCF, STRESS, and STRAIN output, using the RPRINT and RPUNCH options Format for DISP:

  26. Random Response Analysis Format for DISP (cont.): where PSDF—request output for auto power spectral density function ATOC—request output for auto correlation function CRMS—request output for cumulative root mean square RALL—request output for psdf, atoc, and crms RPRINT—request printed output in the f06 file RPUNCH—request punch output NORPRINT—none of the above output • Log-Log option available when computing RMS, N0, and CRMS • PARAM,RMSINT,LOG-LOG

  27. Random Response Analysis • Additional Output are available in MSC.Nastran 2004 • Cross power spectral • Cross-correlation functions • RCROSS (and RANDOM) Case Control commands where PSDF—request output for cross power spectral density function CROF—request output for cross correlation function RALL—request output for both psdf and crof RCROSS (and RANDPS) Bulk Data Entries

  28. Miscellaneous Enhancements • Real Eigenvalue • When Lanczos finds “spurious modes”, UWM 5407 is issued but job continues to run • SYSTEM(317)=1 will fatal job when this situation occurs • GIV and HOU use sparse Cholesky factor resulting in performance improvement • Fast Direct Frequency Response • Activated with SYSTEM(387) = –1 • Perform more executions of FBS and less of DCMP • More effective with solid model and small modal density • Only supports FREQ and FREQ1 entries

  29. Miscellaneous Enhancements • Complex Eigenvalue Analysis • QZHESS method • The mathematical residuals are only calculated if SYSTEM(108)=8. • Only positive square roots of l2 are printed. To request both positive and negative roots, add SYSTEM(108)=4194304 • Only the ND eigenvalues requested on the EIGC entry are printed • Option to request purely real or imaginary roots • SYSTEM(108)=524288—real roots only • SYSTEM(108)=1048576—imaginary roots only

  30. Miscellaneous Enhancements • Dynamic modal matrix generation (GKAM Module) • Modal matrices are now generated in machine precision instead of single precision • In MSC.Nastran 2001, GKAM module always generate an output eigenvector matrix. • This output eigenvector matrix is different from the input eigenvector matrix if: • A selective set of modes are requested (e.g, MODESELECT, PARAM,HFREQ, etc.) or • There are extra points in the model • In MSC.Nastran 2004, this output matrix is generated only if it is needed—substantial disk space savings for large model

  31. Miscellaneous Enhancements • Massless Mechanism Check • Rigid body modes are automatically discarded before massless mechanisms are detected. • Three new parameters have been added: • MMFIL Default=1.E-10 To distinguish rigid body modes from massless mechanism. A smaller value may discard rigid body modes • NLMAX Default=60 Limits the number of trial massless mechanism (max) • NLMIN Default=10 Limits the number of trial massless mechanism (min)

  32. Miscellaneous Enhancements • Multiplying DMIG matrices by scalar factors • Allow each matrix to have a different scalar factor • Scalar factors may be real or imaginary or both • X2GG and X2PP Case Control commands were extended to allow for scalar factors • Examples K2GG = 1.5*K1,2.3*K2 $ Multiplying by real numbers K2GG = (3.0,2.1)*K1, (1.0,1.2)*K2 $ Multiplying by complex numbers • Energy Flow Method (EFM), not published • Implementing the Energy Flow Method for mid-frequency calculations (SOL 103 only) to calculate the Coupling Loss Factors (CLFs) to be used in Statistic Energy Analysis (SEA)

  33. Miscellaneous Enhancements • A new SubDMAP called ONORM is available for orthogonalizing vectors (including complex vectors) • Extends the selective orthogonalization capability that is performed on real vectors using the ORTHOG module • ONORM is not called by any standard solution

  34. Miscellaneous Enhancements • Allow multiple structural damping for shell elements (CQUAD4, CQUADR, CQUAD8, CTRIA3, CTRIAR and CTRIA6) • Allow shell elements to have a different structural damping for MID1, MID2, MID3 and MID4 on PSHELL Bulk Data entry • Turn on with PARAM, SHLDAMP, SAME or DIFF • Default is SAME

  35. Miscellaneous Enhancements • Allow multiple structural damping for • BUSH element • Allow a different structural damping (GE) for each direction on the PBUSH Bulk Data entry with associated frequency dependency

  36. Miscellaneous Enhancements • Non-structural mass for shell elements • Allows the definition of a non-structural mass, either distributed or lumped • Values are added to the NSM value of the selected PSHELL id • Case Control Command • NSM Selects non-structural mass Bulk Data entries • NSM = 10 • Bulk Data Entries • New Bulk Data entries for selecting non-structural mass distribution • NSM Non-structural mass entry by ID, VALUE • NSM1 Nonstructural mass entry by VALUE and list of IDs • NSMADD Non-structural mass as sum of the listed sets • NSML Lumped non-structural mass entry by ID, VALUE • NSML1 Lumped non-structural mass entry by VALUE and list of IDs

  37. Miscellaneous Enhancements • Non-structural mass • NSM Bulk Data entry • Defines a set of non-structural masses • Non-structural mass entry by ID, VALUE • ID is a PSHELL id if TYPE=PSHELL or a CQUAD4 id if TYPE=ELEMID • VALUE is added to the NSM value of the PSHELL entry

  38. SSSAlter Migration

  39. SSSAlter Migration

  40. SSSAlter Migration

  41. Thank you!

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