MSC NASTRAN 2013 SOL400 Adams MNF Export: Accurate representation of Preloaded Flexible Components in Multi-body system.

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1 MSC NASTRAN 2013 SOL400 Adams MNF Export: Accurate representation of Preloaded Flexible Components in Multi-body system Sukhpreet Sandhu

2 Background Adams represents deformation in flexible bodies through CB modes MNF files consists of these modes (besides other information ) CB modes respect BC s and have the richness of vibration modes Critical in forming joints: Capture exact motion of interface points (a-set) MNF can be exported in either: Undeformed configuration Deformed / loaded configuration (includes prestressing effects)

3 Why, SOL 400 MNF? Leverage SOL 400 s advanced modelling capabilities: Advanced elements: Material nonlinearity, large deformation Nonlinear offsets Complex physical phenomenon: Contact Large displacement RBEs One step procedure to generate MNF with nonlinear preload SOL 103 requires restart from SOL 106/SOL 129 to generate MNF with nonlinear preload Better representation of Flex/bodies More accurate multi-body simulations

4 Work Flow / Typical Analysis NASTRAN SOL 400 Nonlinear static step: To get to the deformed configuration Modal step: NASTRAN transforms Nodal DOFs to CB Modal Coords Export MNF ADAMS Import MNF into the MBS to represent the Flexbody: Define the loads and Joints on the Flexbody Conduct the Simulation Tip Displacement Helicopter Rotor Blade Model Windshield Wiper Model

5 Typical SOL 400 Input File for MNF Export $ Exec. Control Section SOL 400 CEND $ Case Control Section ADAMSMNF flexbody=yes, psetid=all, outgstrs=yes, outgstrn=yes SUBCASE 1 $ Preload STEP 10 $ Static load and support for preload SUBTITLE = PRELOAD ANALYSIS = NLSTATICS NLSTEP = 110 LOAD = 120 SPC = 130 BCONTACT = 140 SPCF = ALL $ Generate stress and strain grid shapes STRESS(PLOT) = ALL STRAIN(PLOT) = ALL GPSTRESS(PLOT) = ALL GPSTRAIN(PLOT) = ALL Helicopter Rotor Blade Model $ Modal loading and MNF Output step STEP 20 ANALYSIS = MODES $ Select real Eigen Value Parameters METHOD = 300 $ Turn residual vectors on RESVEC = COMPONENT... $ Bulk section BEGIN BULK GRID... CHEXA... SPC1... FORCE1... NLSTEP... EIGR, 300, LAN,,,, 20 $ SPOINT are required in Main bulk SPOINT,100001,THRU, $ ADAMS REQUIRES DTI, UNITS DTI, UNITS, 1, LBM, LBF, IN, SEC $ If Required, turn on gridpoint weight generator PARAM, GRDPNT, 0 $ If Required, use WTMASS, Default value = 1.0 PARAM, WTMASS, $ FLEXBODY Bulk section BEGIN BULK FLXBDY=10 $ Attachment point and component mode (A-SET) selection ASET1,123456,1,11,111,121 QSET1,0,100001,THRU, Windshield Wiper Model

6 Some Guidelines The ASET and QSET, must only, appear in the FLXBDY bulk data section For contact, friction option should be turned on: $ Select bilinear Coulomb friction for all subcases BCPARA, 0, FTYPE, 6 In ANALYSIS=MODES STEP, the SPC constraint should be removed During preload the structure should be statically supported and follower loading must be applied as a self equilibrating load set

7 Simple Example: Plate Model Plate model with geometric nonlinearities. Step 1, nonlinear static step: Preloads the plate under simple tension Step 2, modal step: MNF is exported. Validation SOL 103 Restarted from SOL 106 SOL

8 Helicopter Rotor Blade System

9 Helicopter Rotor Blade System Generation of Sol 400 MNF: Step 1, the blade is preloaded: Self Weight Axial tensile loading of 4.224e+5 N (centrifugal loading at 2000 deg/s) Step 2, modal step: MNF is exported Rayleigh damping included (Parameters a1 = 2508 and a2=-1.276e-5) Cantilevered modes of Blade: Unloaded SOL 103 Model: Hz and Hz Preloaded SOL 400 Model: Hz and Hz

10 Helicopter Rotor Blade System Three blades attached to the rotor head through fixed joints Rotor shaft speed linearly ramped to 2000 deg/s at t = 25s Impulsive load applied at t = 26s: F = 1.0e+5 N in z-direction, Dt = 0.01s

11 Helicopter Rotor Blade System Translational Deformation (+z) at Blade Tip

12 Helicopter Rotor Blade System Von Mises Stress at t = s

13 Concluding Remarks A new capability of exporting MNF in NASTRAN SOL 400 has been added The capability leverages SOL 400 s advanced modeling capabilities to enable better representation of flexible bodies in ADAMS

14 References Quick Reference Guide MSC Nastran 2013 Quick Reference Guide: See ADAMSMNF case control command documentation Release Guide MSC Nastran 2013 Release Guide: See Section 4, Support for Export of Adams MNF file in SOL 400