1) The document discusses using topology optimization to design an improved engine pylon concept for an aircraft. It aims to reduce mass, part count, and assembly time compared to the current design. 2) Topology optimization was performed on the engine pylon and aft pylon fairing using Altair OptiStruct to minimize compliance. This provided optimized structural designs with up to 200kg mass savings per plane. 3) Preliminary analysis shows the optimized design could reduce the part count from over 650 parts to just 14 parts, and assembly time from over 2600 fixes to around 350 fixes.

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September 2015
8th European Altair Technology Conference, Paris
Abdelkader SALIM
Engineer
Innovation Department
SOGECLAIR aerospace
A New Engine Pylon Concept
Topology optimisation of a large aeronautic structure

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Introduction : SOGECLAIR aerospace
Location : Europe (France, Spain, United Kingdom, Germany)
North Africa (Tunisia )
North America (Canada)
Aerostructures
Systems
Installation
Equipment
Configuration
Management
Manufacturing
Engineering
Aircraft Interiors
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Topology optimisation of a large aeronautic structure
Content
Objectives
Engine pylon location
Main considerations
Engine pylon architecture
• Main components
• Primary structure interfaces
Topology optimisation setup
• Design & non-design zones
• Boundary conditions & loads
• Material & dimensions
• Topology optimisation results
• Geometry reconstruction
Current & optimised pylon comparison
Summary & conclusion
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Topology optimisation of a large aeronautic structure
Demonstrate the feasibility of topology optimisation of a large, complex structure.
Demonstrate the functions and parts integration ability.
Compare current design against optimised design using ALTAIR Optistruct : mass,
number of parts, time.
Uncover innovative architectures.
Explore the methodology for numerical simulation of large systems and the associated
computing facilities.
Project objectives
Assert our ALM & engine pylon expertise.
Stimulate the ALM technological advances (size, simulation, integration ...).
Identify the future "technological roadblocks".
Technical objectives
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Topology optimisation of a large aeronautic structure
Engine pylon location
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Topology optimisation of a large aeronautic structure
The structure must be dimensioned to support the ultimate loads.
Only the main circuits (hydraulic, fuel, air) are considered.
The optimised structure is covered by custom-made cowls for the aerodynamic
purpose.
The wing and engine interfaces are kept as such.
Thoughtful Fail-Safe design at the wing-pylon & engine-pylon interfaces,
The installation constraints of the main equipment are taken into account
(extinguishers, heat exchanger, etc.).
Main considerations
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Topology optimisation of a large aeronautic structure
Engine Pylon
Goal  a "one-part" engine pylon design from “Inconel 718” integrating structures (PS, FSS,
APF) and systems.
Special feature  the rear secondary structure is not taken into account due to its
demountability requirement for maintenance.
Forward Secondary Structure (FSS)
Primary Structure (PS)
Rear Secondary
Structure (RSS)
Aft Pylon Fairing (APF)
Main components
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Topology optimisation of a large aeronautic structure
Primary Structure interfaces
All geometric features are retained at the interfaces.
Front wing attachment
Rear wing attachment
Rear engine lower fastening points
Front engine lower fastening points
Front pylon-FSS interfaces
APF Interface Fittings
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Source: Engine pylon for aircraft
US2011204179(A1)
Ribs
Rear Secondary
Structure (RSS)

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Topology optimisation of a large aeronautic structure
Design & Non-Design Spaces
Non-Design Space
Engine CoG APF Resultant RSS
Resultant
Design Space
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Topology optimisation of a large aeronautic structure
Hydraulic and fuel pipes : double skin concept
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Hydraulic
pipes
Fuel pipe
The smooth flow paths allow to reduce the
pressure drops : friction and minor losses.
Design freedom of the flow paths.

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Topology optimisation of a large aeronautic structure
Boundary Conditions & Loads
Engine CoG APF Resultant RSS
Resultant
Static Loads Inertial Loads
(gx, gy, gz)
Single Point Constraints
(SPC)
Engine Pylon without Aft Pylon Fairing (APF)
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Topology optimisation of a large aeronautic structure
Aft Pylon Fairing (APF)
Boundary Conditions & Loads
RSS
Resultant
SPC
Static Loads
Aerodynamic
pressures
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Topology optimisation of a large aeronautic structure
Material & Dimensions
Engine Pylon : ~9 108 mm3
APF : ~6.7 107 mm3
Volume to be optimised
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Inconel 718
Density : 8.15 10-9 t/mm3
Material
The mechanical properties at 580°C are used for the numerical simulations
Engine pylon dimensions
Length > 5 m
Width > 0.7 m
Height > 1.5 m

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Topology optimisation of a large aeronautic structure
Topology optimisation results
The topology Optimisation objective is to minimise the compliance parameter in OptiStruct
as the loads (forces & pressures ) are applied to the structure
 maximise the structure stiffness.
Optimisation parameters :
Symmetry in XZ plan
Tensile strength (Ftu) = 1082 MPa
Member size = 12 mm
MinDim = 36 mm
VolFrac = 0.02
Engine pylon without APF
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Topology optimisation of a large aeronautic structure
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Topology optimisation results

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Topology optimisation of a large aeronautic structure
Optimisation parameters :
Symmetry in XZ plan
Tensile strength (Ftu) = 1082 MPa
Member size = 12 mm
MinDim = 36 mm
VolFrac = 0.02
Localized over-stresses may be due to the model discretizations.
Engine pylon without APF
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Topology optimisation results

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Topology optimisation of a large aeronautic structure
Optimisation parameters :
Symmetry in XZ plan
Tensile strength (Ftu) = 1082 MPa
Member size = 5 mm
MinDim = 25 mm
VolFrac = 0.02
Aft Pylon Fairing
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Topology optimisation results

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Topology optimisation of a large aeronautic structure
Optimisation parameters :
Symmetry in XZ plan
Tensile strength (Ftu) = 1082 MPa
Member size = 5 mm
MinDim = 25 mm
VolFrac = 0.02
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Topology optimisation results
Aft Pylon Fairing

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Topology optimisation of a large aeronautic structure
Geometric reconstruction
The resulting design is refined with a CAD tool and then numerically verified with OptiStruct.
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Topology optimisation of a large aeronautic structure
1/8 scale model manufacturing in plastic material
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The optimised structure is covered by custom-made cowls for the
aerodynamic purpose.

21. Sous titreEstimated gains
Topology optimisation of a large aeronautic structure
Up to 200 kg saved per plane
450 kg
350 kg
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654
parts
14 parts
2600 Fixs
350 Fixs
Hundred hours of assembly saved

22. Sous titreSummary & conclusion
Topology optimisation of a large aeronautic structure
This study therefore demonstrate a strong interest in topology optimisation, for
Additive Layer Manufacturing, of large-scale parts across the whole aircraft.
By taking advantage of ALM technology, opportunities exist for the aerospace industry
to achieve considerable weight and cost savings.
If the simulation facilities, as OptiStruct, allow to optimise a complex large structure, a
close relation to the manufacturing process needs to be improved.
Efforts on the manufacturability of large-scale structures, via the additive layer
manufacturing process, are needed.
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Topology optimisation of a large aeronautic structure
Design & Calculation
Computing Software
3D Printing
Thank you for your attention
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