optimization of structural components for ariane 5me upper stage
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Optimization of structural components for Ariane 5ME upper stageAndreas Reim, Astrium ST Bremen, TEB11 – mechanical engineering –Gerrit Quappen, Astrium ST Bremen, TEB11 – mechanical engineering –
11.05.2011 Page 2
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Andreas Reim (TEB11)
Overview� Introduction
� Astrium company overview
� Objective of the presented work
� Established optimization process
� Analysis problem description
� Optimization problem definition
� Derivation of optimization procedure
� Application of the method in the frame of A5ME
� Conclusion
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Andreas Reim (TEB11)
Astrium: part of EADS, a global leader in aerospace and defense
Eurocopter Astrium Cassidian
EADS
AirbusAirbus Military
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Andreas Reim (TEB11)
Astrium’s activities are based in three key areas
Astrium Services
AstriumSatellites
Astrium Space Transportation
The European
prime contractor
for civil and
military space
transportation
and manned
space activities
A world leader
in the design
and
manufacture of
satellite
systems
At the forefront of
satellite services
in the secure
communications,
Earth
observation and
navigation fields
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Andreas Reim (TEB11)
Objective of the presented work�Optimization method for
structural optimization of bare tank structures in order to
reduce mass
�Consideration of special
requirements in the analysis of structures in cryogenic environment
� demonstrate feasibility of optimization process by
application on preliminary
design of A5ME upper stage
bare tank components (Y-rings)
Y-rings
Credits: ESA / CNES / Arianespace / Photo Optique vidéo du CSG
Photo available under www.esa.int
Concept for new A5ME upper stage
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Andreas Reim (TEB11)
>250K<100K
<100K
Loads to be considered for preliminary design
�General loads
� inertia and aerodynamic loads
� engine loads
�Pressure loads
� internal gas pressure
� hydrostatic pressure
� quasi static hydrodynamic
pressure
�Thermal mapping (see also /1/)
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Andreas Reim (TEB11)
Developing methods� Methods for calculation of the mechanic characteristics (see also /2/)
� Handbook calculation
� Simplified analytical methods
� Finite Element analyses
� Optimization strategies (see also /3/)
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Andreas Reim (TEB11)
Definition of the optimization problemOptimization problem contains (see also /4/)
� system parameters� Geometrical parameters
� optimization objective � Minimization of mass
� Simultaneously keeping the design in the constraints limits
� optimization constraints� Maximum von Mises stress
� Maximum Shear stress (for weld dimensioning)
� Manufacturing constraints
� system function� Finite element analysis
The system function is also influenced additional parameters
� Finite element mesh definition
� linear vs. nonlinear calculation of the finite element results
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Andreas Reim (TEB11)
Derived optimization procedure1. Free shape optimization (see also /5/)
� Shape modification performed by the optimization algorithm
� Generation of engineering information
� Main steps:� NASTRAN *.bdf File preprocessing
� Integration of optimization constraints and objective
� Perform Optimization using linear FEM
� used commercial software: Altair OptiStruct
2. Shape optimization� Predefined shapes are scaled and superposed
leading to a mass minimum
� Main Steps:� NASTRAN *.bdf File preprocessing
� Integration of optimization constraints and objective
� Perform Optimization using nonlinear FEM
� used commercial software: Altair HyperStudy in combination with MSC NASTRAN
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Andreas Reim (TEB11)
Free Shape Optimization
Preprocessing of FE Modell� Generate temperature based element sets
� Derive material properties for different temperatures within the material
� Connect the element sets to the corresponding material properties
� Set the maximum von Mises and shear stress considering the temperature in the element sets and set it as a constraint
Advantage of the free shape optimization� Shape generated without input from human
� Common understanding about how the structure can be modified
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Andreas Reim (TEB11)
Free Shape Optimization�Output considers
� Information about desired shape of
the component
� Indicator for mass reduction
potential
�Output does not consider
� Geometrical restrictions in weld area
� Nonlinear effects on stress
distribution
Possible optimized shape after
Free Shape optimization
Distribution of linear
stress to deal with
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Andreas Reim (TEB11)
Shape OptimizationPreprocessing of FE Model
� Derivation of shape variables from the free shape
analysis results
� Integrate the shapes derived from the
FSO into the FE model
� Add mass calculation into NASTRAN deck
� Define elements for which constraints will be
calculated
� Model the optimization problem using HyperStudy
Advantage of the shape optimization
� Minimization of structural weight
� Optimized shape considers manufacturing aspects
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Andreas Reim (TEB11)
Application of the method in the frame of A5ME
�Analysis of a simplified FE
model for the A5ME bare tank (rotational symmetric model)
� Loads considered:
� general loads
� pressure loads
� thermal mapping
�Margin of safety policy
respected
�Critical yield/ultimate load
cases modeled (4 in total)
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Andreas Reim (TEB11)
Resulting shape: Free Shape Optimization
Lower Y-Ring Upper Y-Ring
-6% -6%Computational time ~15h
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Andreas Reim (TEB11)
Shape derivation for shape optimization
No thickness changein clamping area
Translation of radius in order to reduce stress peaks
Shoulder definition (see also /6/)(straight lines)
Radius modification in order to reduce stress peaks
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Andreas Reim (TEB11)
Resulting shape: Shape Optimization
Lower Y-Ring Upper Y-Ring
Shape Optimization
Free Shape Optimization
Initial design
-7% -5%Computational time ~12d
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Andreas Reim (TEB11)
Summary1. Generation of a reference design
� Defines the topology under investigation
� Design may violated single constraints
2. „Free Shape“ optimization
� derivation of mass reduction potential
� Information about advantageous shapes
3. „Shape“ optimization
� Derivation of components mass
� All requirements are met
4. Optimal structural design
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Andreas Reim (TEB11)
Conclusion� Positive influence of nonlinear FEM:
� The peak stresses within the linear FEM results overestimate the more realistic nonlinear stresses.
� nonlinear FEM can consider these effects
� Negative influence of predefined shapes
� The shape optimization is limited to a number of predefined geometric shapes. This restricts the possible mass reduction.
� The implemented optimization method efficiently improves the mass budget of the given structures.
� For the components under consideration, a 9% mass reduction seems to be achievable, if the influence of the design change is also considered in the adjacent structures.
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Andreas Reim (TEB11)
Literature/1/ Frey, B. (2010):
Thermalkonzept der Kryogenen Oberstufe von ARIANE 5 Midlife Evolution, 60. Deutscher Luft- und Raumfahrtkongress 2011, Bremen
/2/ ESA Requirements and Standards Division ESTEC (2010): Space engineering - Buckling of structures, Noordwijk
/3/ Schumacher, A. (2005):Optimierung mechanischer Strukturen: Grundlagen und industrielleAnwendungen, Berlin, Heidelberg: Springer
/4/ Lawden, D, F. (2006):Analytical Methods of Optimization, Mineola: Dover Publications
/5/ Thue, R. B. et al (2010):Application of Structural Optimization Technologies and Methods to Reduce Design Time and Improve Structural Robustness, in proceedings of AIAA SPACE 2010 Conference & Exposition, AIAA
/6/ Öry, H. (1991): Structural Design of Aerospace Vehicles I, SPACE COURSE, Institut fürLeichtbau, RWTH Aachen, Proceedings, 1991