1. Structure sizing optimization capabilities at AIRBUS
5/23/2017
Structure sizing optimization capabilities at AIRBUS
WCSMO12 – 5th to 9th of June - Braunschweig
30/05/ Stéphane GRIHON – AIRBUS ESCADT
Expert Structure Optimization – Development of Structure Optimization capabilities
NAFEMS Optimization by Simulation 30th of May - Paris

2. A spectacular growth in less than 50 years
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5/23/2017
Airbus in 2 figures
A spectacular growth in less than 50 years
A worldwide
footprint
NAFEMS Optimization by Simulation 30th of May - Paris

3. Structure optimization at AIRBUS: an overview
5/23/2017
Introduction
Structure optimization at AIRBUS: an overview
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4. Structure Optimization: A multi-step CAD-CAE process
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5/23/2017
Structure Optimization: A multi-step CAD-CAE process
Addressing different levels of design variables:
Topology
Sizing
Shape
Involving design & stress constraints
supported by numerical simulation (FEA)
driven by weight minimization
(cost: engineering judgement)
A380 leading edge rib full numerical design
NAFEMS Optimization by Simulation 30th of May - Paris

5. Structure optimization: Airbus vision
5/23/2017
Structure optimization: Airbus vision
OUR VISION
An optimisation driven stress and design process that will change the way we design airframe structures
Inspire structures innovation
Accelerate concept & detailed definition
Deliver cost savings & performance enhancements
Support all development stages
NAFEMS Optimization by Simulation 30th of May - Paris

6. Major technologies and their purposes
Topology Optimisation
Laminates?
Stacking ?
Rapid-Sizing
Material distribution optimisation to predict optimum design concepts
How does tomorrows structure look ?
Materials?
Stiffening Concepts?
Prelim Sizing?
Structural Layout?
Global sizing and selection of optimum materials, stiffening concepts & layout
Global detailed sizing for stress, design and manufacturing
Detailed sizing?
Laminate definition?
Interfaces definition?
Fibre steer?
Ply-by-ply?
Effect of design principles?
Manufacturable?
Pre-Sizing
Local detailed sizing and shape definition for parts / specific areas
Detailed-Sizing

7. Structural Sizing: A specific stress process
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5/23/2017
Structural Sizing: A specific stress process
Geometry
FEMIX (CATIA/SimX)
Modelling
External loads
NASTRAN
ISAMI (CAESAM)
Sizing properties
Global Finite Element Model
Internal Loads
Static linear analysis 
Strength analysis tools 
Reserve
Factors
Transverse dimensions:
skin thickness, laminates;
Stiffener profiles, laminates
Ratios between structural responses and
allowables (linked to material / geometry) :
RF  1 : structure feasible
RF< 1 : structure not feasible
Structural sizing: To determine transverse dimensions for minimum weight (with manufacturing constraints) and stress feasibility.
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8. Structure Optimization Capabilities: COTS or Developments ?
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5/23/2017
Structure Optimization Capabilities: COTS or Developments ?
Topology optimization – Detailed sizing and shape optimization for parts - fully FE-based  COTS(*)
Two reasons for developing structure optimization capabilities
Specificity of our internal stress processes including our in-house tools (ISAMI)  Global sizing tools – PRESTO / ACO-AMO
Needs of process integration for lead time reduction  GDE MyShape
MSC Software - NASTRAN SOL200
ALTAIR - OptiStruct
Dassault - Generative Design Explorer
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9. Specific developments
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Specific developments
PRESTO: rapid sizing stage.
Simplified fully discrete optimization approach for early trade-off studies and weight estimation at airframe or component level
ACO/AMO: pre-sizing stage
Standard optimization solution for later design stages with weight savings purposes and quick handover to design
MyShape: Automated process for numerical design of parts
Two reasons for developing structure optimization capabilities
Specificity of our internal stress processes including our in-house tools (ISAMI)  Global sizing tools – PRESTO / ACO-AMO
Needs of process integration for lead time reduction  GDE MyShape
Discrete sorting algorithm using catalogues and ISAMI databases
Based on CAESAM Samtech-Siemens
Gradient-based optimization with sensitivity chain-ruling
Based on Dassault – 3D Experience
NAFEMS Optimization by Simulation 30th of May - Paris
Numerical Design of Parts

10. PRESTO
A tool for trade-off studies and quick strength analysis

11. Definition: What is rapid (structural) sizing ?
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Definition: What is rapid (structural) sizing ?
A structure sizing process whose speed is compatible with the reactivity required in early airframe design milestones
For each architecture:
 best design principles to be selected
 sizing to be performed
Laminates
stackings
metallic
Al2024, Al-Li
sized FEM
FEMIX
composite
IMAM21E,
T800_M21_268
Geometries & Architectures
Sizing & weights
Stringer type:
J,I,riveted,bonded
Stringer height
Stringer width
Maintenance, margin policy
Weight breakdown
10 airframe architectures X
102 structure trade-offs =
103 sizings to be run
Rapid sizing requires a much quicker process compared with standard optimization approaches
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12. Distributed computing
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PRESTO principles
PRESTO has been therefore developed according to the following objectives:
The quickest possible sizing solution while being compatible with
ISAMI (AIRBUS standard strength
Design & manufacturing constraints
PRESTO principles:
All strength analyses (ISAMI calculations) are made upfront based
on pre-defined design catalogues:
RF Databases
The sizing algorithm is local and enumerative for easy decomposition/parallelisation and to mix sizing and trade-off studies
Laminate catalogue
Sizing algorithm
Distributed computing
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13. Optimum sizing (stackings, profiles) Detailed properties for ISAMI
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PRESTO process
Catalogues (stackings, profiles)
Internal loads update
Strength analysis
Sizing
Satellite process:
Creation of RF Databases
NASTRAN
Enumeration
Property update
RF Database
Core process:
Rapid sizing
and structure trade-offs
Optimum sizing (stackings, profiles)
Updated GFEM,
Detailed properties for ISAMI
Initial GFEM
PRESTO: two processes in one. Satellite process to build sizing knowledge, core process to perform sizing
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14. PRESTO applied to covers of all airframe structural components
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Achievements
A Fuselage
A , A380 NEO HTP
Tens of trade-off studies performed to support major design choices for composite fuselage – significant weight savings
FEMIX
PRESTO
Rapid sizing performed with improved composite stringer sections and skin laminates - significant weight savings
Tens of trade-off studies performed to support major design choices for metallic fuselage – significant weight savings
Tens of trade-off studies performed on various metallic/composite wings for single aisle and long range aircraft (MDAACE, FLEXWING, ARTEMIS,WoTF)
Fuselage research
Wing research
PRESTO applied to covers of all airframe structural components
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15. PRESTO current developments
Core solution developed but under extension to other structural elements
Main work is in integration in wider processes
Especially automated link to FEMIX alive in MDAACE process for trade-offs:

16. On-going developments
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On-going developments
PRESTO satellite process is being extended to a range of data exploitation services in a Big Data mindset
PRESTO is becoming a Big Data service around ISAMI databases for the whole engineering
Trade Campaign Data Base
Creation of catalogues
ISAMI
Failure envelopes
Surrogate models
PRESTO
(Satellite Process)
MACROS(*)
(gaussian processes)
APIs
Local sizer
RFDB extract under xls format
Local strength analysis with sensitivities
(for gradient optimizers)
(*) MACROS is a Datadvance COTS
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17. ACO-AMO
Advanced structural sizing optimization

18. ACO/AMO: a Concurrent Engineering Process
5/23/2017
ACO/AMO: a Concurrent Engineering Process
MOTIVATION: Integrated global pre-sizing process aims for fewer loops and associated time/weight savings
Upstream implementation of design/manufacturing requirements
PROCESS
MOTIVATION: True global pre-sizing process for stress, design and manufacturing allows design process with fewer loops and associated time/weight savings.
The way to achieve this is through upstream implementation of design/manufacturing requirements
ACO extends the scope of Pre-sizing to full skin/spar (excl high load areas with some level of interface analysis/sizing
Full skin/spar (excl high load areas)
Initial interface analysis/sizing
SCOPE
5/23/2017
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19. 5/23/2017
5/23/2017
ACO Pre-Sizing – Multiple Design Fidelities as an Enabler for a Concurrent Pre-Sizing Process
ACO objective: Solving a global optimisation problem while capturing local details
Different
model descriptions required even within a single discipline field
Skill Tools -
Detailed stress
analysis
Manufacturing/
Design rules
Key element: automatic mapping between idealizations
Finite Element
Analysis
Solving a global optimisation problem while capturing local details is a key ACO objective.
For such an optimisation problem we need be able to move from global geometry idealizations to very specific stress analysis idealizations, GFEM idealizations or very detailed representations that capture local detail (skin ramps, stringer growouts, etc), all in a single loop.
We thus easily find that Different model descriptions are required even within a single discipline field
Thus, the ability to automatically map between different idealizations is key component for numerical optimisation.
Detailed Stacking
Sequence
Lamination
Parameters
Layup
COMPOSITE
IDEALIZATION
Optimisation
Geometry
idealizations
Design Enriched
All modules included in the optimization loop
with chain ruling with SOL200 sensitivities
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20. Stress Analysis integration for a full box capability
5/23/2017
5/23/2017
Integration of standard ISAMI stress modules Multiple stress modules integrated for different components O(106)/O(107) stress constrains considered, multiple load cases. Set up of a full box optimisation run is a true logistics problem. Optimization algorithms: NLP++ library (INUTECH) SCP (MMA and SCP) NLPQLB – SQP with very many constraints NLPQLP NLP miSQP Open source: IPOPT Others: GCMMA, SNOPT
Stress Analysis integration for a full box capability
Filled Hole module (rib to cover interface)
Super stiffener module
(covers)
Spar web and cap module
Integration of standard ISAMI stress modules for consistency of sizing policy and code commonality
Multiple stress tools have been integrated for different components.
We must note however that the complexity is growing significantly requiring both a significant effort to properly setup the analysis and substantial knowledge in sizing processes for multiple components.
Overhang/spar land module
Manhole surrogate model (ACO development)
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21. Manufacturability measures
5/23/2017
5/23/2017
Manufacturability measures
Laminate manufacturability accounted for directly during initial pre-sizing Controls volume variation, ply drop-off and continuity to target layup time reduction Technique demonstrated on A350 upper cover and bottom cover Key ingredient to constraining laminate evolution Manufacturability measures in use for current A350 runs
Constant-Region skin thickness distribution
Initial starting design – from COMBOX
Optimal solution with manufacturing constraints
Optimal solution without manufacturing constraints
Optimal solution – with mfg constraints
Optimal solution – without mfg constraints
An extreme case – A350 TC, panel-by-panel regions:
Laminate manufacturability measures are accounted for directly during initial pre-sizing
Manufacturability measures target layup time reduction by controlling ply drops, ply continuity and volume variation.
The technique has been demonstrated on A350 upper cover and bottom cover
Manufacturability measures are an essential ingredient to constraining laminate evolution
Manufacturability measures are in use for current A350 runs
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22. Ply-by-ply optimisation for global covers
5/23/2017
Ply-by-ply optimisation for global covers
Representative applications: Ply-by-ply optimisations for A350
Optimisation scenarios:
Plies “sliced” from a continuous optimisation run
“Fast mode” - laminate design constraints only
“Comprehensive mode” – laminate design constraints and integrated stress analysis
101 layers created
2898 design rules
best solution after 184 iterations
Use of Ant Colony Optimization

23. Sizing optimisation through large-scale simulation
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Achievements
ACO applied to A wing box: covers and spars
Pre-sizing performed up to full ply definition
for covers and spars
Significant weight savings demonstrated
ACO adapted to metallic materials with a specific
sizing process defined for fatigue and damage tolerance
 AMO
AMO applied to A330 NEO wing box
ACO/AMO:
Sizing optimisation through large-scale simulation

24. SOFIA
A synthesis of PRESTO and ACO/AMO between discrete and continuous optimization

25. Why not a single structural sizing optimization tool ?
Continuous approximations are tedious for small numbers of plies
Optimization problems are sometimes not well-posed requiring catalogues not necessarily easy to interpolate
Criteria can be non-differentiable
It is difficult to address mixed variable optimization with a good level of performance when large number of variables
From Engopt 2008 (Rio de Janeiro): Structure and Multidisciplinary Optimisation at AIRBUS State of the art and trends for the future

26. An attempt in Research
Difficulty lies in the inherent combinatorial nature of really discrete variables (categorial)
Several ideas under investigation:
Multi-level or multi-step approaches:
- use of Lagrange multipliers:
Mono-level approaches: evolutionary approaches
- evolutionary like CMA-ES
Mixed approaches explored at AIRBUS in early 2000s: Annealed Feasible Directions
PhD Thesis at IRT Saint-Exupéry (MDA-MDO platform)
Paper: 351 Mixed variable Structural optimization: toward an efficient hybrid algorithm
Pierre-Jean Barjhoux, Youssef Diouane, Stephane Grihon, Dimitri Bettebghor, Joseph Morlier

27. A preliminary approach
Linkage of PRESTO and SOL200 in a loose coupling bi-level approach
(finite differences)
Already validated for a composite wing use-case
NASTRAN SOL200 to be further replaced by ACO-AMO

28. Next industrial step: SOFIA – Sizing Optimization Framework in Airbus
Optimization tool box
Sizing (automation)
Catalogues, RFDB, Surrogate Models, constraints
Pre/post-processing, constraints
Knowledge databases
Structural optimization
Catalogues, RFDB, Surrogate Models, constraints
ISAMI
(with potential adaptations)
A single toolbox merging both approaches and supporting sizing optimization in all design stages

29. Conclusion
Towards MDO and Big Data

30. MDO and Big Data
After several experiences of MDO projects around NASTRAN SOL200, a project of aeroelastic tailoring is planned around ACO/AMO to include load sensitivities in optimization
To perform passive load alleviation by taking best benefit of structure flexibility and exploiting aeroelastic tailoring (specific wing cover lay-up definition for increased flexibility effects)
(In cooperation with Airbus D&S and their experience built around LAGRANGE tool)
PRESTO experiences with databases and surrogate models will be commuted to a Big Data approach in the frame of the AIRBUS digitalization strategy
To take benefit from the massive amount of computational results from current and past programmes to reduce overall computational times and perform sensitivity/uncertainty analysis
PhD CIFRE at AIRBUS started last year

31. Acknowledgement Lucian Iorga (Structure Optimization R&T)
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5/23/2017
Acknowledgement
Lucian Iorga (Structure Optimization R&T)
Lars Krog (Struture Optimization leader)
For their contribution to this presentation
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