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

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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

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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

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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.

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Optimisation Setup

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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

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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

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Optimised Model

First automatic geometry generation (OSSmooth)

Further manual cleaning needed (ATOS, Geomagic)

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Before cleaning After cleaning

Geometry Generation

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Thin bridges Unnecessary parts

Geometry Generation

Geometry

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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

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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

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Improvement

Better smoothing of «big steps» by OSSmooth

Checking of unnecessary parts by OSSmooth

Automatic mesh refinement

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Thank you for your attention!

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