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For typical satellites, tertiary structure, i.e. supports for antennas, sensors and connectors, can represent up to 20-30kg. The introduction of new manufacturing processes like Additive Manufacturing combined with the topology optimisation capabilities of Optistruct allow to envisage mass savings of around 30%. The presentation shows the results of a topology optimisation performed by RUAG Space on an Antenna Support of the Sentinel-1 Spacecraft. It also shows how RUAG Space intend to implement this methodology combined with Additive Manufacturing in the development of future satellite structures.
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Topology Optimisation of
Tertiary Structures and Mass
Savings for Satellite Structures
Mouriaux Franck
Senior Manager Engineering & Development
RUAG Schweiz AG
RUAG Space
Münich, 26.06.2014
Content
02.07.2014 │RUAG Space│ 2
Objective
Bracket
Work
Optimisation Setup
Model Size
Geometry Generation
Comparison
Summary
Improvement
Objective
02.07.2014 │RUAG Space│ 3
Design space,Loads and
ConstraintsPrinting
Designevaluation
StructuralAnalysis
Construction ManufacturingDesign space,
Loads and Constraints
Optimization
Compare current design against optimised design using ALTAIR
Optistruct
Time
Mass
Stress
Bracket
02.07.2014 │RUAG Space│ 4
Upper S-Band Antenna Support of the Sentinel-1 Satellite
Material Aluminium
Mass-Bracket 1.626kg
Mass-Antenna 0.783kg
Dimensions 385x345x115 mm
1.Eigenfrequency >70Hz
Static Load 20g / 25g
Allowable Stress 163MPa
Outer dimensions of the existing
bracket => Design space
Antenna represented as a
concentrated mass and
connected with RBE3.
Provision for attachment bolts
accessibility
02.07.2014 5 │RUAG Space│
Bracket
First optimization setup
Objective
Minimize Massfrac
Constraints
First eigenfreq. > 70Hz
v.M. stress < 163MPa
Problem
Very low and unrealistic eigenfrequencies
=> no feasible design
02.07.2014 6 │RUAG Space│
Optimisation Setup
Second optimization setup
Objective
Minimize compliance
Constraints
First eigenfreq. > 70Hz
Mass fraction < 0.4…0.05
Note
Running the optimization with different mass fraction constraints will
lead to different stress levels.
=> Multiple runs are needed to find a suitable stress level.
02.07.2014 7 │RUAG Space│
Optimisation Setup
02.07.2014 │RUAG Space│ 8
Full design space: 11.6kg.
Mass fraction: 0.09
Element size: 3mm
Model Size: 300’000 nodes.
No thin membranes possible
Model Size
Two optimization loops
02/07/2014 │RUAG Space│ 9
Meshing the
whole design
space
Loop #1
Target mass
of 4.5kg
Delete
unnecessary
elements and
remesh with
smaller
elements
Loop #2
Target mass
of 1.2kg
Model Size
02.07.2014 10 │RUAG Space│
Optimised Model
First automatic geometry generation (OSSmooth)
Further manual cleaning needed (ATOS, Geomagic)
02.07.2014 │RUAG Space│ 11
Before cleaning After cleaning
Geometry Generation
02/07/2014 │RUAG Space│ 12
Thin bridges Unnecessary parts
Geometry Generation
Geometry
02/07/2014 │RUAG Space│ 13
Comparison
Current Design Optimised Design
Time 3-4 Days 4-5 Days
Mass 1.6 kg 1.0 kg
Eigenfrequency 89 Hz 140 Hz
v.M. Stress 75 MPa ~90 MPa
02.07.2014 │RUAG Space│ 14
Summary
Mass reduced by 35%
Key Problems
Compromise between acceptable model size and element size
Effort for cleaning the geometry
Need for interpretation and manual work
02.07.2014 │RUAG Space│ 15
Improvement
Better smoothing of «big steps» by OSSmooth
Checking of unnecessary parts by OSSmooth
Automatic mesh refinement
02.07.2014 │RUAG Space│ 16
Thank you for your attention!
02.07.2014 │RUAG Space│ 17