Project Scope. Perform a major step forward in Airbus Virtual Testing (VT) capability of structures. Project launch Design Certification

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1 Presented by Michel MAHÉ Prepared by Michel MAHÉ, Jean-François IMBERT, Christophe BRAND Aircraft Virtual Structural Testing: Challenges for Structure Analysis Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR Project Scope Perform a major step forward in Airbus Virtual Testing (VT) capability of structures Provide an alternative to tests for Whole A/C life cycle: Validate technology integration/ potential Parametric modelling tools to support design or verify new design concepts Evaluate design solutions and mitigate design risk Alternative to certification tests from major component to full scale tests Project launch Design Certification Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 2 In service investigations

2 Project Scope Perform a major step forward in Airbus Virtual Testing (VT) capability of structures Provide an alternative to tests for All validation pyramid levels A/C full scale tests Coupons Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 3 Project Scope Objective Reduce Validation & Verification (V&V) costs Improve A/C performance Improve A/C maturity Reduce time to market Get the full benefit of new technologies Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 4

3 Project Scope What is Virtual Testing (VT) of structures? Numerical analysis technology for A/C Structure strength assessment: Capability to predict structure failure From metallic to composite structures From quasi -static to dynamic phenomenon Including determination of structure environment like thermal Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 5 Today design process Materials Design 3D Mock up Architectural concept + e3 l2 e2 l1 e1 Loads Stress l3 Global FEM generation Optimisation Local tools Stress dossier Verification: Detail/component analysis/tests Major component test (rarely analysis) Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 6

4 Outline As is is Customer expectations Business expectations Context Restraining factors on on VT VT developments Conclusion Vision // What to to do do // Where to to go? Conclusion Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 7 Customer expectations Programmes Centre of Excellence Airlines Airworthiness Authorities AA Product performance Reduce V&V / test costs product maturity Increase confidence in new design solutions Mitigate design risks Robust / validated / reliable means of compliance Maintenance free Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 8

5 Business expectations: Indirect savings Costs of a modification vs. product development cycle Impact / cost 0 EIS time To reduce industrial / financial risk, it is needed to validate design solutions/concepts as early as possible But physical tests appear to be: - expensive - time consuming Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 9 Business expectations: Direct savings Huge savings from numerical validation compared to test Cost of a test (including manufacturing): X Cost of simulation: X/8 to X/14 15 tests saved for A380 Test Virtual test rig Virtual Test Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 10

6 Context Past experience STATIC A certification Support to design Risk mitigation Support to certification Replace A/C test by component test 0,0% Calculation Test STRAIN (%) -0,4% -0,8% Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 11-1,2% 0,0 0,5 1,0 1,5 LOAD (CL) 1 st modelling phase: 9 man*months 1 st attempt to large scale virtual testing (2000) It has clearly demonstrated capabilities & way forward Context Past experience STATIC A340 Mid front spar buckling Correlation between analysis and test Analysis model TEST SIMULATION Buckling: Analysis ~ 60% LL Test ~ 50-60% LL Failure: Analysis ~ 160% LL Test ~ 156% LL Validation of M&T Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 12

7 Context Past experience Bird strike on A380 cockpit Support to design Support to certification TRANSIENT DYNAMICS SIMULATION TEST Strain level correlation SIMULATION TEST Titanium replaced by aluminium for 1st time Certification performed through analysis only, using validated M&T Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 13 Context Past experience Fatigue & DT A300 Frame 47 crack analysis Understand and model crack growth under compressive loads Fr47 Fr48 Fr49 Fr46 Rear of aircraft Fr45 STGR 22 CWB upper panel Crack location CWB side CWB lower panel Outer wing side STGR 37 Forward of aircraft From global FEM to local FEM FR47 FRONT face CRACK LH SIDE A Tool validated through comparison with tests Tool used to support in-service aircrafts Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 14

8 Context Past experience Thermal 80.0 Pylon transient thermal model validation against FT TRENT 500 pylon/engine/nacelle model Temperature ( C) simulation 20.0 test Time (s) Good agreement on overall trends Acceptable agreement on maximum temperature Time (s) Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 15 Temperature ( C) simulation test Context internal Airbus Challenge on Costs / Quality / Maturity in service for A/C in development Future A/C projects Challenge on performance Composite fuselage/wing A/C architecture Common Virtual Bird project Project initiative towards full simulated A/C Complete integration of analysis tools Ongoing projects Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 16

9 Context External Airbus Airbus competitors Military A/C Automotive Virtual crash testing now common place Car and marine engines Hardware performance evolutions From this paper, no evidence of achievements and no strategy Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 17 Context External Airbus Number of processors Performance (GFlop) Processors Processor performance Impressive & constant hardware performances evolution Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page

10 Regulations & Interpretations Proof of Structure (NPA 25C-290) The following statements are taken directly from NPA 25C-290: Every reasonable effort should be made to prevent separation (failure) of elements (components) from the aeroplane All elements (components) should be subjected to some form of stress checking The consequences of failure of a particular component should be taken into account when determining the need for & extent of testing The application of methods such as FEM is considered reliable only when validated by full scale tests (ground and/or flight tests). The applicants experience in the utilisation of such methods should be considered The confidence that can be attached to the applicants overall experience in analysing, designing and testing should be considered in deciding the extent of testing The need for & extent of testing depends on The classification of the structure The consequences of failure of the structure in terms of overall integrity of the aeroplane This NPA provides constraints on the ES V&V Strategy by the traditional/conservative approach adopted but could also provide opportunities Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 19 Context: conclusion VT is already part of structure analysis culture Significant achievements already performed Continuous improvement of Hardware & Software performances Short & mid term benefits can be cashed in a stepwise approach Reliability to be demonstrated & confidence to be increased Improve performance: lead time & costs Improve detail and fundamental simulation and modelling methods / techniques for each skill area (material behaviour, failure criteria) Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 20

11 Context: conclusion VT technology available today But developments still required and in particular with respect to practical modelling solutions for full exploitation of this technology Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 21 Outline As is is Vision // What to to do do // Where to to go? Vision Improve confidence in in Virtual Testing Improve overall process performance Improve skill skill capabilities Conclusion Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 22

12 Vision Full scale A/C: 1 Static test 1 Fatigue test A/C Certification test VT Full scale A/C: 1 Analysis model 1 Multi-purpose test Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 23 Vision Combined static & fatigue tests so as to provide some validation to overall A/C Virtual Test Model Develop modelling methods separating intrinsic material & technology characteristics from geometrical data Will allow understanding and modelling of composite / laminate damage Fatigue analysis of complex assemblies Enable information to be exchanged between skills/disciplines to allow A/C architecture optimisation Afford virtual implementation of new technologies for performance trade-off, maturity assessment, Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 24

13 Vision - Short to mid term In a short term vision, it is intended to Replace large component test by lower level tests, Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 25 Vision - Road map simulation maturity Maturity/Validation/ Confidence demonstrated 100 Full scale component Certification Full scale A/C 50 Depends on technology/domain Full scale component Risk mitigation When not fully validated, it is already possible to get a benefit from these methods for risk mitigation Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 26 Years

14 What to do - Outlook 3 main areas for improvement 1. Improve confidence in Virtual Testing 2. Improve overall process performance 3. Improve skill capabilities Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 27 Improve Confidence in Virtual Testing It takes many years to build up confidence in simulation internally and externally. It can quickly disappear if simulation is used incorrectly in only a few cases Development of Virtual testing must go hand in hand with Quality assurance following the right first time principle Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 28

15 Improve Confidence in Virtual Testing 1. Improve day to day reliability SW quality Assurance Working procedures Training of users and competences follow up Use of SW under controlled Partnership with S/C: Quality/efficiency 2. Demonstrate reliability: Do systematically pre-test analysis, published Record pre/post test correlations (measure performance) Develop Robust analysis 3. Communicate on the performance Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 29 Improve overall process performance Get CAD All the process has to be improved!!! Simplify CAD Meshing & CAE inputs Solver Postprocessing Test/ simulation correlation Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 30

16 Improve overall process performance 1. Improve access to CAD data The link between visualisation and the import in CAD environment. 2. Improve exploitation of CAD data in CAE environment Import CAD definition into CAE environment is still a tricky path. Get CAD Simplify CAD Meshing & CAE inputs Postprocessing Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 31 Solver get CAD Test/ simulation correlation Improve overall process performance Shell modelling Get CAD Simplify CAD Meshing & CAE inputs Simplify CAD Solver Postprocessing Test/ simulation correlation Improve automation: Capabilities being developed (COTS or Research centers) NL-FE SW intend to provide the capability through pre-processor Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 32

17 Improve overall process performance 1. Automation on mid-plane surface for meshing has to be performed (shell modelling) 2. Solid element modelling to challenge shell modelling Get CAD Simplify CAD Meshing & CAE inputs Meshing & CAE inputs Solver Postprocessing Test/ simulation correlation 3. Information to be read from CAD and automatically linked to the relevant surface (Thickness, offset, stacking sequence, ) 4. Engineering modelling principles to be written Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 33 Improve overall process performance Performance of NL FE analysis depends on: Get CAD Simplify CAD Meshing & CAE inputs Solver Software performance: Partnership to ensure improvements Solver Postprocessing Test/ simulation correlation Hardware performance: Natural improvement process Collaboration between HW & SW vendors Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 34

18 Improve overall process performance Ensure that the relevant information is not missed? Automated search based on criteria Get CAD Simplify CAD Meshing & CAE inputs Post-processing Solver Postprocessing Test/ simulation correlation Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 35 Improve overall process performance 1. Modelling test rig for boundary conditions!!!!!! Get CAD 2. Define customer-oriented link with global/local structural FEM to provide information back Simplify CAD Meshing & CAE inputs Test/ simulation correlation Solver Postprocessing Test/ simulation correlation 3. Enlarge the use of sophisticated experimental stressing methods like 2D strain/displacement measurement to provide data for correlations Test evolution: Less tests but more sophisticated test means Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 36

19 Improve overall process performance Conclusion Get CAD Simplify CAD Meshing & CAE inputs 1. By Improving the overall process performance, it will become increasingly possible to use simulation earlier in the verification process It will be all the more used as costs of one calculation will be significantly reduced Solver Postprocessing 2. Intrinsic performance of each step has to be improved, but integration is also a key factor for success 3. A simulation data management system is compulsory to keep records and provide assistance to decision making 4. The above improvement requirements are currently taken into account in Route06 Lean8 ISAMI project Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 37 Test/ simulation correlation Improve skill capabilities Unfortunately, all skills have shortcomings and have to improve the maturity of their analysis method to reach a validation / confidence level allowing the use for certification General skills Static Fatigue Composites Thermal Vulnerability Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 38

20 Improve skill capabilities Multi-scale analysis approach Large-scale FE models (Major component level or full-scale) Medium-scale FE models Philosophy At the full-scale or major component levels it is today and in the near future not possible to have enough detail to capture all structural failure modes accurately. Detail FE models (Details like individual fasteners and accurate material failure predictions) (Sub-component level) Small-scale FE models (Joints and structural details) More detail is therefore introduced gradually until reliable and accurate methods (approximate or absolute) are available for prediction of fastener, material and buckling type failures. For this sub-modelling and sub-structure analysis techniques are used. Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 39 Improve skill capabilities Failure prediction methods Explicit methods where likely failure regions are modelled in DETAIL using solid elements (low scale) With high quality NL FEA models it is today possible to capture highly non-linear structure deformation behaviour very accurately but acceptable failure predictions are still subject to research and must be improved to make Virtual Testing possible. Equivalent (homogenisation approach) methods where design allowable values are derived in relation to FE detail/tests used. Approximate failure criteria could avoid explicit modelling of fastener holes. Individual fasteners could be modelled using simplified fastener models that would enable an assessment of shear, tension and bearing failure types and inter-fastener failure mechanisms. Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 40

21 Improve skill capabilities Robust analysis with reliability analysis methods The level of conservatism should take into account accuracy of analysis prediction (failure, ) Influence of scattering of input data has to be assessed Material properties, thickness, Sensitivities are then available to: Understand key parameters Built a robust design Better understand test and analysis correlations Not only a result is expected! The level of confidence has to be given as well Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 41 Improve skill capabilities Major areas where scientific contribution is needed Reaching the target will require technology breakthrough in Composite damage mechanism modelling Metallic failure modelling Joint/fastener failure modelling Multi-scale approach with parallel computing Develop robust analysis methodology Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 42

22 Conclusion: Project objectives Get the acceptance of Airbus numerical technology for A/C Structure strength assessment enabling to Reduce lead time development, thus time to market Reduce V&V costs, Improve A/C maturity Get 100% of the potential of structure technologies Improve A/C performances Project road map: 1 full scale A/C major test for certification Long term: 6-10 years* Further reduce level of A/C major component test for certification Secure day to day & A/C major component modelling for risk mitigation * Depending on the technology introduced Medium term:3-8 years* Short term: Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page years* Conclusion: Added value of the project Address overall concept of VT, and provide a global approach ensuring consistency and integration of the proposed solutions, in line with Engineering & Stress analysis strategies Will federate internal & external Advanced Numerical Analysis capabilities and expertises VT will benefit Airbus whilst being developed, and have high Return On Investment Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 44

23 Conclusion: Key success factors Strategic partnerships with research institutes Strategic partnerships with preferred hardware and software suppliers Nurture key competences Enhancements from research / Process improvement implemented into new industrial stress environment Strong effort must be made to make use of future structural tests to validate analysis methods and IT solutions Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 45 This document and all information contained herein is the sole property of AIRBUS S.A.S. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document shall not be reproduced or disclosed to a third party without the express written consent of AIRBUS S.A.S. This document and its content shall not be used for any purpose other than that for which it is supplied. The statements made herein do not constitute an offer. They are based on the mentioned assumptions and are expressed in good faith. Where the supporting grounds for these statements are not shown, AIRBUS S.A.S. will be pleased to explain the basis thereof. AN EADS JOINT COMPANY WITH BAE SYSTEMS Aircraft Virtual Structural Testing: Challenges for Structural Analysis - ESA - Ref. PR April 8, 2005 Page 46