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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 1 ( 21 )
Topology Optimization of Engine Mount Brackets
Dr. Dirk SprengelFord Werke GmbH
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 2 ( 21 )
EMS Bracket Funktion
EMS: Engine Mount System
Link between engine and body EMS bracket assembled with:
Cylinder Head Engine mount
Alternator (Cover)
Durability crash, extreme driving conditions NVH, driving comfort no transfer, amplification of engine vibrations,
no eigenmodes in driving range
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 3 ( 21 )
Problem Definition, Task
Conventional bracket design:
EMS involved into several engine eigenmodes
Local EMS frequency below target of 500 Hz(example: 420, 470 Hz)
Run Topology Optimization to
Improve modal behaviour of bracket ( fi > 500 Hz )
( Ensure durability )
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 4 ( 21 )
Define Optimization Volumes and Design Rules
Draw directions Obstacles
~ 200.000 elementsregular voxel mesh
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 5 ( 21 )
Optimization Submodel, Boundarys, Loads
Static: loads Fbolt 50 kN+ Fh 10 kN+ Fh - 10 kN+ Fv 10 kN+ Fv - 10 kN
+ Fl 10 kN
Dynamic: max. Eigenfreq.: Alternator horz. + EMS
EMS local (>500Hz) Alternator vert.
5x
Cylinder Head
Engine Block
Alternator
EMS Ring
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 6 ( 21 )
Optimization Run Design Recommendation
Iteration 19Density >= 0.3Color: casting constraints
Run OptiStruct Min. Compliance @ Static Loads 5x
Max. Eigenfrequencies No. 1,2,3
Volume: 30% of design space(~ old bracket volume)
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 7 ( 21 )
Robustness Check of Optimization Run
The optimization seems to be robust, the final design was useful.
Base features have been recommended for new CAD geometry.
Not used (model size)Other OptiStruct features (maxmb)
Not checked:Change of draw directions
Not checkedChange of boundary conditions or loads
20% results in weaker design with same design features
Influence of Volumefrac target :
20% instead of 30%
Changed weight factor: 10x
small design changes
Check balance between:
Min. compliance ( static )
Max. Eigenfrequencies ( modal)
Main features with small design changes
Single Optimization Frequency(w/o static loads)
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 8 ( 21 )
Opti CAD Geometry FE check
Modal analysis of complete P/Train: Reduced participation of EMS
1. Local EMS Mode from 470 Hz to 681 Hz
No check of stress distribution
new partCAD / FE
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 9 ( 21 )
Next Task: Changed Engine Installation Angle, Position
Prototype (449 Hz, local stress concentrations) improve it!
Changed bolt position resultsin a deep hole ( cast draw ) Stress concentration
Changed bolt position resultsin a sharp corner near a thread Stress concentration
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 10 ( 21 )
Bracket II Optimization Task
Dynamic: 500 Hz
Static : Min. compliance
+ Stress reduction
TopologyOptimization
OptiStruct + Engineering Judgement !!
The definition of design space + draw rules should lead
to an optimization result with feasible stress distribution.
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 11 ( 21 )
Bracket II Optimization Model: Single / Split Draw
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 12 ( 21 )
Optimization Model: Final Cut
Design space Cut out to avoid stress concentration or to reduce mass concentration
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 13 ( 21 )
Bracket II Optimization Run CAD
CAD Added features
( lifting eye, cover flange,)
OptiStruct
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 14 ( 21 )
Dynamic Performance
Modal behaviour CAD FEM remeshed, complete P/Train
EMS 1. Mode: 538 Hz(Prototype: 449Hz, Target: 500Hz)
general: reduced modal EMS participation
Stress distribution
No direct optimization task,driven by model features
see next pictures
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 15 ( 21 )
Stress Analysis: Bolt foces 50 kN + EMS vertical 10 kN
Prototype Design Final Design
Critical
high tensionat corner
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 16 ( 21 )
Stress Analysis: Bolt foces 50 kN + EMS vertical 10 kN
Stress Analysis Bolt foces 50 kN + vertical EMS load 10 kN
Prototype Design Final Design
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 17 ( 21 )
Successful EMS Evolution
High improvement of part functionality Bracket I
Modal 681 Hz Robustness study (optimization model, loads, parameters)
Bracket II : Modal 538 Hz Stress distribution durable
Based on bracket I model, experience Well prepared for stress reduction
Lecture What structure do we really need?
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 18 ( 21 )
Start Product Development with Optimized Design
Base design features
byOptimization
First in Chain!
Short time reactionwith
Optimization tool+
Concept Job 1Product Development
Cost of changes
Design changesTar
getsetting
Time
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 19 ( 21 )
Education
Process Management
Opti CAD CAE First in Chain!
CAE: Optimization
Take the lecture! What structure do we really need?
Improve process
Persuade people
All Update Engineering Judgement No Design by Rules Design by Need
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 20 ( 21 )
Final Message
Optimize !
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Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 21 ( 21 )
Thank You!
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