Adams-to-Nastran. Jose L Ortiz, PhD. Adams User Meeting Munich - May 19, 2011

Transcription

1 Adams-to-Nastran Jose L Ortiz, PhD. Adams User Meeting Munich - May 19, 2011

2 Agenda Overview Manual and Scripted Translation Theoretical Background Implementation Details Example Q&A 5/26/2011 2

3 Agenda Overview Introducing Adams-to-Nastran Manual and Scripted Translation Theoretical Background Implementation Details Example Q&A 5/26/2011 3

4 Overview There is a need for model translation from Adams to FEA Multibody Dynamics System model Adams Finite Element Analysis model FEA 5/26/2011 4

5 Overview Introducing Adams-to-Nastran Performs an automatic model translation (export) from Adams to FEA Available for the past 2 releases As of today, an MD license and a LINEAR license are required Available only in the Adams/Solver C++ 5/26/2011 5

6 Overview Introducing Adams-to-Nastran (cont.) The export process creates a set of fully editable *.bdf files Old black box option still available Minor limitations in the type or complexity of the Adams model Models with non holonomic constraints Tool can be used from shell and from Adams/View 5/26/2011 6

7 Overview Introducing Adams-to-Nastran (cont.) There is no need to modify the Adams model There is no need to change your processes Export job can be triggered at any operating point Export job is a high fidelity translation Accurate kinematics Matching eigenvalues (static cases only) 5/26/2011 7

8 Overview Introducing Adams-to-Nastran (cont.) Users can use an optional configuration file to fine tune translation Current release exports to linear FEA codes 5/26/2011 8

9 Overview Example CAE process Create Adams model Adams NVH Optimization FEA Motion analysis translation 5/26/2011 9

10 Agenda Overview Manual and Scripted Translation Problems Limitations Theoretical Background Implementation Details Example Q&A 5/26/

11 Manual and Scripted Translation Manual translation Error prone Time consuming (300 man hours for chassis prototype) Inaccurate 5/26/

12 Manual and Scripted Translation Manual translation Error prone Time consuming (300 man hours for chassis prototype) Inaccurate Scripted (user-written script) Limitations. Cumbersome Inaccurate 5/26/

13 Manual and Scripted Translation Why inaccurate? Kinematic configuration is hard to reproduce 5/26/

14 Manual and Scripted Translation Why inaccurate? Kinematic configuration is hard to reproduce Eigenvalues computed by FEA code do not match eigenvalues computed by Adams MBD FEA 5/26/

15 Manual and Scripted Translation Why inaccurate? Kinematic configuration is hard to reproduce Eigenvalues computed by FEA code do not match eigenvalues computed by Adams Structural coupling can be compromised 5/26/

16 Manual and Scripted Translation Why inaccurate? A thorough theoretical study showed that (1) High fidelity translations require mathematical information not available to users 5/26/

17 Manual and Scripted Translation Why inaccurate? A thorough theoretical study showed that (1) High fidelity translations require mathematical information not available to users Example: MOTION/1, JOINT=2, FU=DX(7,8)-DZ(11,23) 5/26/

18 Manual and Scripted Translation Why inaccurate? A thorough theoretical study showed that (1) High fidelity translations require mathematical information not available to users (2) Linear FEA codes use linear constraint equations 5/26/

19 Agenda Overview Manual and Scripted Translation Theoretical Background Overview Governing equations in Adams Governing equations in Nastran Example Implementation Details Example Q&A 5/26/

20 Theoretical Background Overview Automatic. The translation is another simulation job 5/26/

21 Theoretical Background Overview Automatic. The translation is another simulation job Command: SIMULATE/DYN, END=1.0, STEP=10 LINEAR/EXPORT, TYPE=WHITEBOX, FILE=abc.nas 5/26/

22 Theoretical Background Overview Automatic. The translation is another simulation job Adams/View: 5/26/

23 Theoretical Background Overview Automatic. The translation is another simulation job Adams/View: 5/26/

24 Theoretical Background Overview Automatic. The translation is another simulation job Accurate. Exact kinematics 5/26/

25 Theoretical Background Overview Automatic. The translation is another simulation job Accurate. Exact kinematics Overcomes FEA limitations 5/26/

26 Theoretical Background Overview Automatic. The translation is another simulation job Accurate. Exact kinematics Overcomes FEA limitations Matching eigenvalues guaranteed for static cases 5/26/

27 Theoretical Background Basic idea Linearize the Adams model at the operating point 5/26/

28 Theoretical Background Basic idea Linearize the Adams model at the operating point Linearize the Adams model using Nastran coordinates 5/26/

29 Theoretical Background Basic idea Linearize the Adams model at the operating point Linearize the Adams model using Nastran coordinates Identify inertia elements, constraint equations and forces 5/26/

30 Theoretical Background Basic idea Linearize the Adams model at the operating point Linearize the Adams model using Nastran coordinates Identify inertia elements, constraint equations and forces Will the equations assembled by Nastran match? 5/26/

31 Theoretical Background Basic idea Linearize the Adams model at the operating point Linearize the Adams model using Nastran coordinates Identify inertia elements, constraint equations and forces Will the equations assembled by Nastran match? Need to examine the equations of motion in more detail 5/26/

32 Theoretical Background Governing equations in Adams Simplified version Nastran coordinates used! Non linear equations! 5/26/

33 Theoretical Background Governing equations in Adams (cont.) Simplified version Partitioning 5/26/

34 Theoretical Background Governing equations in Adams (cont.) Simplified version Partitioning Defining P This P is non linear! 5/26/

35 Theoretical Background Governing equations in Adams (cont.) Eliminating Lagrange multipliers Non linear equations! 5/26/

36 Theoretical Background Governing equations in Adams (cont.) Eliminating Lagrange multipliers Differentiating constraints Non linear equations! 5/26/

37 Theoretical Background Governing equations in Adams (cont.) Eliminating Lagrange multipliers Differentiating constraints Dependent accelerations 5/26/

38 Theoretical Background Governing equations in Adams (cont.) Reduced ODE First and second derivatives of dependent states can be found from constraint equations Linearization done in terms of Nastran coordinates 5/26/

39 Theoretical Background Governing equations in Adams (cont.) Reduced ODE First and second derivatives of dependent states can be found from constraint equations Linearization done in terms of Nastran coordinates Exact linearization of ODE. In variational form Linearized equations! 5/26/

40 Theoretical Background Governing equations in Nastran Partitioned equations of motion (linear) 5/26/

41 Theoretical Background Governing equations in Nastran (cont.) Partitioned equations of motion (linear) Constraints (linear) 5/26/

42 Theoretical Background Governing equations in Nastran (cont.) Partitioned equations of motion (linear) Constraints (linear) Defining P (this P is a constant) This P is a constant! 5/26/

43 Theoretical Background Governing equations in Nastran (cont.) Dependent accelerations 5/26/

44 Theoretical Background Governing equations in Nastran (cont.) Dependent accelerations Reduced ODE 5/26/

45 Theoretical Background Governing equations in Nastran (cont.) Dependent accelerations Reduced ODE Final form 5/26/

46 Theoretical Background Adams and Nastran equations This P is non linear! Adams Nastran This P is a constant! 5/26/

47 Theoretical Background Linearized Adams and Nastran equations 5/26/ Adams Nastran u u v T T T T f f f M M v M M M M v M M M M P P P P P P P P P P P δ δ δ δ δ δ + + = Ψ ) ) (( ) ( ) ( u v T T f f v M M M M δ δ δ P P P P P + = ( 2 ) P is now a constant!

48 Theoretical Background Linearized Adams and Nastran equations (cont.) 5/26/ Adams Nastran u v T T f f v M M M M δ δ δ P P P P P + = ( 2 ) u u v T T T T f f f M M v M M M M v M M M M P P P P P P P P P P P δ δ δ δ δ δ + + = Ψ ) ) (( ) ( ) (

49 Theoretical Background Eigensolutions will match only in static cases 5/26/ Adams u u v T T T T f f f M M v M M M M v M M M M P P P P P P P P P P P δ δ δ δ δ δ + + = Ψ ) ) (( ) ( ) ( Zero in static configuration Exported as DMIG

50 Theoretical Background Example Windmill Model provided by NREL Blades 63.5 m radius 5/26/

51 Theoretical Background Example Windmill (cont.) Model provided by NREL Blades 63.5 m radius Static simulation followed by eigensolution Model exported to Nastran 5/26/

52 Theoretical Background Example Windmill (cont.) Exported model imported into Patran Run SOL 107 5/26/

53 Theoretical Background Eigenvalue comparison 5/26/

54 Theoretical Background Eigenvalue comparison (cont.) 5/26/

55 Agenda Overview Manual and Scripted Translation Theoretical Background Implementation Details Inertial elements Force elements Constraints Configuration file Example Q&A 5/26/

56 Implementation Details Miscellaneous issues By default, exports model for SOL 107 $ Force = N (newton) $ Time = s (second) $ UCF = 1000 $ Export type: Whitebox $ Configuration file used: a2n_config.txt $ $ SOL 107 CEND TITLE = ADAMS2NASTRAN Export Utility SUBTITLE = Adams operating point at time t= e+000 ECHO = NONE CMETHOD = 101 5/26/

57 Implementation Details Miscellaneous issues (cont.) Files are organized using three optional styles and included in main exported file $ $ $ Model $ INCLUDE 'results/a2n_01_w.bdf.nas INCLUDE 'results/a2n_01_w.bdf_dmigs.bdf INCLUDE 'results/a2n_01_w.bdf_graphics.bdf $ ENDDATA 5/26/

58 Implementation Details Miscellaneous issues (cont.) Every MARKER is exported as a GRID and a CORD2R: PART/2 MARKER/3 Several numbering conventions $ PART_2.MARKER_3 CORD2R* D D+02 * D D D D+00 * D D D-14 $ PART_2.MARKER_3 GRID* E E+00 * E /26/

59 Implementation Details Miscellaneous issues (cont.) GRIDs are RBE2 d to the CM of the corresponding PART: $ PART_2 RBE /26/

60 Implementation Details Inertial elements Adams model is linearized without constraint equations. This makes easier to identify the inertia properties of all elements M 1 M 2 M 3 5/26/

61 Implementation Details Inertial elements (cont.) PART and POINT_MASS are translated as CONM2 $PART_1 GRID* E E-01 * E-16 $ $PART_1 CONM2* E+00 * * E E E E-32 * E E+00 5/26/

62 Implementation Details Inertial elements (cont.) FLEX_BODY are translated as SPOINT and three DMIG (M, K, and B) $ FLEXIBLE_BEAM SPOINT 9999 THRU $ $ FLEXIBLE_BEAM DMIG MGMYFLX DMIG* MGMYFLX * D+00 DMIG* MGMYFLX * D+00 DMIG* MGMYFLX * D+00 5/26/

63 Implementation Details Force elements All forcing elements (GFORCE, VFORCE, SPRING, etc.) are translated as CBUSH, PBUSH cards plus a residual DMIG VFORCE CBUSH + DMIG δ f + Pδ f + δ P v u f u 5/26/

64 Implementation Details Force elements (cont.) PBUSH properties and residual DMIG computation F = K U u Adams linearization K u Matrix is full and not symmetric! (damping not shown for clarity) 5/26/

65 Implementation Details Force elements (cont.) PBUSH properties and residual DMIG computation Standard FEA transformation Ku U = R T K p R U? Desired PBUSH property must be diagonal 5/26/

66 Implementation Details Force elements (cont.) PBUSH properties and residual DMIG computation T R KuR = K p + D r Exported PBUSH property. Diagonal matrix Residual DMIG. Residual DMIG could be zero! 5/26/

67 Implementation Details Force elements (cont.) Typical output (residual DMIG not shown) $ I: PART_1.MARKER_4, J: PART_9.MARKER_8 $ Grid coincident with marker I but located on PART_9 GRID* E E+00 * E RBE $ $SPRING_1 PBUSH* K E E-14* * E E E E+00* * B E E+00* * E E E E+00 $ CORD2R* D D-01 * D D D D+01 * D D D-16 $ I: PART_1.MARKER_4 CBUSH /26/

68 Implementation Details Force elements (cont.) Residual DMIG can be split into a symmetric and a non symmetric parts Without splitting SET 1 = KGt00001 K2GG = 1 With splitting Symmetric residual SET 1 = KGt00001 SET 2 = KPt00001 K2GG = 1 K2PP = 2 Non symmetric residual 5/26/

69 Implementation Details Force elements (cont.) Residual non symmetric DMIG can be manually removed from exported files Removal of non symmetric DMIG allows running SOL 103 and other solutions requiring symmetric matrices only 5/26/

70 Implementation Details Constraint elements Whenever possible, JOINT and JPRIM are exported using RJOINT $ TrnJnt $ $JOINT_3000 $ I: PART_3000.MARKER_3001, J:PART_9000.MARKER_9003 GRID* E E+00 * E $JOINT_3000 RJOINT* $ $ FxdJnt $ $JOINT_1000 $ I: PART_1000.MK_REF1, J:PART_9000.MARKER_9001 RJOINT* /26/

71 Implementation Details Constraint elements (cont.) Whenever possible, JOINT and JPRIM are exported using RJOINT UNIVERSAL and HOOKE are exported as combination of RJOINT Other constraints (GCON, MOTION, etc.) are exported as MPC cards 5/26/

72 Implementation Details Constraint elements (cont.) Constraint MPC are obtained by computing Matrix is exported as MPC 5/26/

73 Implementation Details Differential elements DIFF, LSE, GSE, and TFSISO are exported as SPOINT and DMIG Given M q + Φ T q λ = Φ( q) = z = f ( q, z) 0 h( z, q, t) DIFF, LSE, GSE TFSISO 5/26/

74 Implementation Details Differential elements (cont.) Linearization finds 05/15/11 74 Exported as DMIG = z q q A A A A Q P I z q q

75 Implementation Details Graphic elements Alpha version CONM2, DMIG, GRID, SPOINT 5/26/

76 Implementation Details Graphic elements (cont.) Current version 5/26/

77 Implementation Details Graphic elements (cont.) All GRAPHIC elements are exported as constrained CQUAD4 or CTRIA3 elements with zero mass 5/26/

78 Implementation Details Graphic elements (cont.) All GRAPHIC elements are exported as constrained CQUAD4 or CTRIA3 elements with zero mass FLEX_BODY graphics are exported fixed in space (to be enhanced) All exported graphics can be removed before starting Nastran solutions Debugging tool. Does not affect results. 5/26/

79 Implementation Details Configuration file (cont.) An optional configuration file can be supplied LINEAR/EXPORT, TYPE=WHITEBOX, FILE=abc.nas, CONFIG=myconfig.txt Configuration file is a plain text file with directives Allow fine tuning the export process 5/26/

80 Implementation Details Configuration file (cont.) Users may: Modify numbering schemes, choose solution number, modify defaults, create channels for FRF solution in Nastran, remove damping, etc. Easy to add new directives 5/26/

81 Implementation Details Configuration file (cont.) Example configuration $ Setting FRF analysis for SOL 108 actuator_swept_sine { phase_angle = 90 magnitude = 77 name = test01 } Comments force_input_channel { name = f1 marker_id = 3001 dof = ry actuator_name = test01 } displacement_output_channel { name = d1 marker_name = model.part_1000.mk_ref1 } 05/15/11 81

82 Implementation Details Configuration file (cont.) Example configuration (cont.) frequency_response_subcase { number = 101 input_channel_names = f1 output_channel_names = d1 } export_all_markers = no mpc_set = 77 grid_offset = 1 spoint_offset = 9999 solution_number = 108 forces_dmig_name = ADMS1 differentials_dmig_name = ZZ3 matrix_entry_zero_tolerance = 1.e-8 05/15/11 82

83 Agenda Overview Manual and Scripted Translation Theoretical Background Implementation Details Example Q&A Full chassis model 5/26/

84 Example Chassis model prototype (courtesy of BMW Group) 5/26/

85 Example Exported model loaded in SimXpert 5/26/

86 Example Eigenvalues comparison Chassis - Frequency error vs. Mode number % Error Mode number 5/26/

87 Example Observations Matching eigenvalues for static cases only FEA model has exactly the same kinematic configuration as in Adams 5/26/

88 Agenda Overview Manual and Scripted Translation Theoretical Background Implementation Details Examples Q&A Acknowledgments Q&A 5/26/

89 Q&A Acknowledgments MSC.Software Italy Dr. Daniel Heiserer (BMW Group) MSC.Software Germany 5/26/