1re Runion Technologique Europe du Sud

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1ère Réunion Technologique Europe du Sud
ANALYSIS OF AERONAUTICAL STRUCTURES WITH
MSC/NASTRAN ABOUT SPECIFICITY OF FORMULATION FOR
ELEMENTS AND D.O.F RELATIONS J. Chaix AMB -
Toulouse
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CONTENTS
1- Introduction 2- Generation of NASTRAN
model 2.1 Numbering convention 2.2
Automatic assembly of Sub-structures 2.3 Model
Characteristics 3 - Comparison of results
3.1 Methodology systematic comparisons of
results 3.2 Analysis of significant
differences 4 - CBEAM limitations 5
- Conclusions
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INTRODUCTION (1)
? NASTRAN software is commonly used at
Aerospatiale Matra Airbus (AMB), as Finite
Elements Software Reference since end 1997 for
new aircrafts (A340-500/600 , A3XX) ? Now
we have a new challenge ? To use NASTRAN
Software for in_service aircrafts (maintenance
activity) (A300/310 family, A320/321/319 family,
A340/330 family) ? To use NASTRAN Software for
derivated aircrafts (The first application is
the A318, derivated aircrafts from Single
Body program)
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INTRODUCTION (2)
? For these two news activities AMB should
manage TWO references ? Old stress
dossier including Aself results (in-house F.E
software) ? New complementary results
obtained with Nastran (for current
studies) ? The two modelisations (Aself and
Nastran) must provide very similar results
It s essential to check and to valid Nastran
results / Aself Nastran Comparison of
displacements, forces and stresses differences
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INTRODUCTION (3)
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Airbus A318-A319-A320-A321Standard Bodies
Nombre de passagers 185 - 220 Rayon daction
3 000 nm
Nombre de passagers 150 - 180 Rayon daction
3 000 nm
Nombre de passagers 124 - 145 Rayon daction
3 500 nm
Nombre de passagers 107 - 129 Rayon daction
gt 2 700 nm
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Airbus A320 Components
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Generation of NASTRAN model
Goal To build a Complete Nastran model according
to the Aself schematization (behavior of finite
elements, sub-structures assembly rules)
? To find easily the correspondance
(Node/element number and location) between Aself
and Nastran models ? To generate automatically a
separated Bulk Data file for each primary
sub-structure (component) ? To generate
automatically an unique Bulk Data file of
assembly Datas Link between interface grids
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Numbering rules
Primary sub-structure (component)
Primary Aself sub-structures are identified by
cc number as  Left component models  CC 1
(TR11) -? 49 Right component models   CC51
(TR12) -? 99 Coordinate System Refence of
component  CC GRIDs, ELEMENTs,PROPERTIES
(except PCOMP) MATERIALS CC xxx xxx Internals
CORDxx, FORCE, MOMENT,SPC,LOAD, PCOMP,
MAT8 CC xxx
Assembly datas
Global aircraft coordinate system 100
000 MPCADD, SPCADD 100 000 Interfaces GRID
numbers 100 001 ? 299 999 Assembly RBE2
100 001 ? 299 999
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Identification of differents components
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Automatic assembly of components
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Complete Nastran Model
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CHARACTERISTICS OF NASTRAN MODEL
? LOADCASE Pressure 2DP1194MB F crochet 1450
daN ? Control of all applied loads resultants
(component by component) --gt Component
location OK --gt Changes of coordinate
system (component location) OK ? Model
characteristics Cbeam 17870, Crod 12854, Skin
17650, genel 1240 Grids 21031, CORD2R
581, DOF 79126 Maxratio 1,26 108
(Recommended Value 1, 107) Epsilon 1,00
10-12 (Recommended Value 1, 10-6)
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A319-na Displacements Results
Pressure loadcase
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Systematic comparison of results
? Sytematic comparison of displacements, internal
forces and stresses ? Development of a specific
tool which manage ? numbering
correspondance ? CD coordinate system
? mcsid definition for cquad4, ctria3
elements and provide ? results
differences tables and files for graphic
visualization
Example Displacements
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Nose fuselage component displacements
differences(maxi 1.1 mm) - Pressure loadcase
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Nose fuselage component GPFORCES differences
(zoom - maxi 3 E4 N) - Pressure loadcase
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Nose fuselage component Differences of Bending
Moments in CBEAM(maxi 2.7 E5 N.mm) - Pressure
loadcase
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Nose fuselage component Differences of Normal
Force in CBEAM(maxi 4 400 N) - Pressure loadcase
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Nose fuselage component Differences of Shear
Force in CBEAM(maxi 6 100 N) - Pressure loadcase
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Nose fuselage component Differences of Von
Mises(maxi 3.3 hb) - Pressure loadcase
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Centre Fuselage Component displacements
differences(maxi 0.1 mm) - Loadcase C80882
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Centre Fuselage Component Von Mises
differences(maxi 1.6hb) - Loadcase C80882
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Centre Fuselage Component Bending Moments in
CBEAM Visualisation of differences - Loadcase
C80882
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Centre Fuselage Component Von Mises
differences(maxi 1.6 hb) - CAS C80882
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Centre Fuselage Component STIFFNERS
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Centre Fuselage Component STIFFNERS
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CBEAM element Description
I1 073 521 mm4
I6 140mm4
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CBEAM Element Description
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CBEAM element Results
Type5 standard Aself Aself Beam Element (
10 integration points) Type5 SC moyen  SC1
and SC2 are calculated with Kmoy(SC1SC2)/(SN1SN
2) CBEAM Element Element with properties at
end A and B Type 5 3 Integration points.
Integration scheme with 3 Gauss points Type47 -
I variation f(S . D2) with d1
, d2
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CBEAM Element Conclusions
Resultats aself (attention aux unites Aself
daN, m.daN ---------------
Nastran N, mm.N
T Y P E 5 - POUTRE FLEX. EFF. TRANCH. ET
NORMAL NO MAT
POINTS INERTIE Hz Sc Sn Dz
Vz MFy Tz N SIGma (hbar)
TAUz ELEM (cm4)
(mm) (mm2) (mm2) (mm) (mm) (m.daN)
(daN) (daN) (Vz) (Vz-Hz) (hbar) 20503
1 503 107.35 76.0 323.
911. 0.0 58.3 -23.85 345. -3286.
-2.31 -4.00 1.60 L(mm) 182.
523 0.61 6.7 30. 1641. 0.0
3.4 38.94 345. -3286. -23.25 19.24
17.26 Resultats Nastran

-----------------
20503 SANS SECTIONS
INTERMEDIAIRES -----------------------
----- 5000503 0.000
-1.685864E05 -1.557755E-04 -3.649409E03
-4.556301E-07 -3.293288E04 0.0
0.0 5000523 1.000 4.952224E05
-7.289871E-05 -3.649409E03 -4.556301E-07
-3.293288E04 0.0 0.0 20503
AVEC SECTIONS INTERMEDIAIRES
----------------------------
5000503 0.000 -2.378005E05 -1.562443E-04
-3.474485E03 -4.637687E-07 -3.291005E04 0.0
0.0 5000523 1.000
3.941906E05 -7.188715E-05 -3.474485E03
-4.637687E-07 -3.291005E04 0.0
0.0 D'OU PAR COMPARAISON DIRECTE -------------
-------------- TRI PAR MODULE DECROISSANT
DES DIFFERENCES DE M N T POUTRE (module) ELT
ASELF ! M ase M nas ! N ase
N nas ! T ase T nas !
Mod (ase-nas) ! Mod/Mod SANS 20503
-238460. -168586. 29. -32859.
-32933. 0. 3452. -3649. 6.
699121. 31. AVEC 20503 -238460.
-237801. 0. -32859. -32910. 0.
3452. -3474. -1. 688.
0. SANS Sans sections intermediaires --gt
calcul initial AVEC Avec sections intermediaires
--gt calcul avec prise en comte correcte de la
forte evolution des inerties
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CBEAM Element Conclusions
NASTRAN CBEAM ELEMENT USE AN INTEGRATION SCHEME
WITH 3 GAUSS POINTS FOR LARGE VARIATION OF
INERTIA (MORE THAN gt 1/10) BETWEEN ENDs A AND
B INTEGRATION SCHEME NEEDS TO USE MORE THAN 3
GAUSS POINTS. gt USER MUST PUT 2 ADDITIONALS
SECTIONS IN PBEAM DATA (AT X/XB 0,8
and 0,9 OR X/XB0,1 and 0,2) near the END with
small inertia WARNING THE USE OF
INTERMEDIATE STATIONS IN PBEAM (ONLY TO OBTAIN
FORCES OR STRESSES RECOVERY) WILL MODIFIY THE
BEAM OVERALL STIFFNESS!!
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Global comparison synthesis
ST815 C80882
ST811 pressure
ST811 C86722
ST821 C80882
dDep
90 lt 0,1 mm
dGpforces
90 lt 2500 N
dVmises panneau
96 lt 7,5 Mpa
dM Poutre
99 lt 10 m.daN
dN Poutre
97 lt 1000 N
96 lt 500 N 99 lt 1000 N
dT Poutre
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Global comparison synthesis (suite)
? Results correlations are satisfactoring for
most nodes/elements ? More significant
differences can appear locally for following
reasons - Warped cquad4 elements
(--gt The corrective method which take into
account the warping of cquad4 is based on an
implementation of auxiliary forces.
What are physical significations of theses
correctives forces?) - Ctria3 elements in
bending behavior (thick element) - Very
stretched Ctria3 elements - Trapezoidal cquad4
element in flexion - CBEAM element with very
large variation of inertia ? AMB needs to know
very well the NASTRAN element formulations
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Conclusion
? AMB uses NASTRAN Software for new aircarfts
(A340-500/600 program). ? AMB would like to use
NASTRAN Software for in-service aircrafts
(maintenance activity) and derivated
aircrafts ? AMB uses NASTRAN Results Displaceme
nts, internal forces, Gpforces, Stresses Theses
results must be reliable for All elements
type All load capabilities (Applied Forces,
thermal load, ..) ? AMB post-processing tools
use extensively the Nastran GPFORCES More than
100 000 times a year Many sub-contrators