Automated Strength Analysis Processes for Aircraft Structures

Transcription

1 Automated Strength Analysis Processes for Aircraft Structures Automatisierte Festigkeitsanalyseprozesse für Flugzeugstrukturen Univ.-Prof. Dr. Martin Schagerl

2 Overview Structure Build-Up Structure Design Structure Analysis Structure Validation Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 2

3 Structure Build-Up Airbus Family A380 fuselage diameter > 5 m wide body aircrafts A340 A350 A330 A320 Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 3

4 Structure Build-Up Fuselage Sections skin seat rail stringer frame Redundant Structures stiffened panel (longitudinal direction) frame (circumferential direction) floor (cross direction) cross beam floor support strut longitudinal beam Special Structures window area door surrounding inter costal A380 Section 13 Side Shell door corner Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 4

5 Structure Build-Up Wing Cover ribs front spar center spar rear spar skin underside stringers Rib skin Spar Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 5

6 Structure Build-Up Frame Structures A330 / A340 circular fuselage th January 2009, Hamburg Finkenwerder, Etihad Airways A X approximate data, do not reference! frame pitch 530 mm Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 6

7 Structure Build-Up Frame Structures A380 high side shell frame frame pitch 635 mm A380 B747 approximate data, do not reference! Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 7

8 Structure Build-Up Frame Structures A400M high multi-girder frame R 2820 R 2620 massive main frame R 1000 floor 264 R 6600 preliminary data, do not reference! Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 8

9 Structure Build-Up Frame Structures frame CFRP pre-preg material [30 /90 /-30 ] with 0 reinforcement plies clip PPS thermoplastic material quasi-isotropic lay-up stringer co-bonded to skin preliminary data, do not reference! Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 9

10 Structure Design Disciplines Results of Group Dominance in Aircraft Design aerodynamics group stress group manufacturing group Niu, Airframe Stress Analyses and Sizing, 1999 Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 10

11 Structure Design Integrated Tools Material DB Other DB Flight physics CAD parts Technical Data Norm data Design data Loads Masses Material data Rivet data Profile data A/C Project Data Management Stress Model Repairs support Manufacturing Stress Dossier ACD Structural Design Certification reports Documentation GFEM generation Global FEM Linear / Stresses for Strength and Fatigue Global buckling GFEM analysis Local analysis Metallic Static Strength Composites Stiffened Static panel Strength analysis Fatigue & Frame Damage analysis Tolerance Cross-beam analysis Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 11

12 Structure Analysis Applied Loading Global FE Model rough global stiffness discretization stringer ROD, skin QUAD, frame BEAM, etc nodes and elements undeformed A HGW Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 12

13 Structure Analysis Applied Loading Combined Load Case Study 200 different load cases considered taxing, maneuver, landing, braking, one engine out, etc. undeformed deformed (scale factor 10) Load Case 516 = symmetric landing Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 13

14 Structure Analysis Applied Loading Applied Loads e.g. frame bending moment e.g. skin longitudinal stress M B -40 MPa 80 MPa x,skin F N 200 MPa e.g. frame normal force fictitious data, do not reference! Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 14

15 Structure Analysis Reserve Factors Applied Loading for each load case Allowable Loading for each design objective Discipline Design Objective Load Case Criteria Parameters Static Strength Ultimate Strength Ultimate Loads failure Deformation Limit Loads detrimental deformation fracture, instability barely visible impact damage plasticity, instability barely visible impact damage Fatigue & Damage Tolerance Fatigue Life, Durability Operational Loads crack initiation design service goal Crack Growth Residual Strength & Damage Capability Operational Loads Limit Loads critical crack length failure inspection threshold & intervals no growth policies barely visible impact damage two bay crack visible impact damage Reserve Factor for each load case and each design objective RF design allowable design load design factor safety factor MS RF 1 Margin of Safety Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 15

16 Structure Analysis Allowable Loading Static Strength Analysis Frame Sizing Criteria normal strength failure shear strength failure local instability Effects on cross-sectional loading material homogeneity local instability lateral instability plasticity y frame M B,n neutral axis F N stringer shear tie Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 16

17 Structure Analysis Allowable Loading Static Strength Analysis Stiffened Panel Sizing Criteria general instability in-plane strength failure post-buckling failure stringer forced crippling compression/shear 1 shear ratio / pure 0,8 skin failure shear 0,6 0,4 panel column failure compression 0, ,2 0,4 0,6 0,8 1 compression ratio / pure Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 17

18 Structure Analysis Stress Dossier Stress Model Load case Failure mode Reserve factor Minimum Reserve Factor Plot e.g. stiffened panel analysis A Section 16 skin in-plane strength skin shear strength stringer forced crippling panel column buckling fictitious data, do not reference! Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 18

19 Structure Validation Requirements Authority Requirements European Aviation Safety Agency Certification Standard 25 for Large Aeroplanes CS Proof of structure Structural analysis may be used only if the structure conforms to those for which experience has shown this method to be reliable. In other cases, substantiating load tests must be made. Bruhn, Analysis and design of flight vehicle structures, 1973 Local level Validation of Component Structure and Design Allowables by component tests by nonlinear FE analyses Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 19

20 Structure Validation Component Tests Stiffened Panel under Shear / Compression Loads Component test rig Validation regarding loads Nonlinear FE model shear ratio / pure compression ratio / pure Validation regarding deformation Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 20

21 Structure Validation Full Scale Test Global level Validation of Aircraft Structure and Global FE Analysis by ES ( Cellule d Essai Statique ) by EF ( Cellule d Essai Fatigue ) A380 ES Wing Bending Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 21

22 Thank you for your attention! Automated Strength Analysis Processes for Aircraft Structures - M. Schagerl 16/06/2011 Page 22