NVH, driving comfort no transfer, amplification of engine vibrations, ... Define
Optimization Volumes and Design Rules ... Opti → CAD Geometry → FE check.
Topology Optimization of Engine Mount Brackets
Dr. Dirk Sprengel Ford Werke GmbH
Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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EMS Bracket Funktion
EMS: Engine Mount System
Link between engine and body EMS bracket assembled with: • Cylinder Head • Engine mount • Alternator • (Cover)
Durability NVH, driving comfort
Dr. D. Sprengel
6/2007
crash, extreme driving conditions no transfer, amplification of engine vibrations, no eigenmodes in driving range Topology Optimization of EMS Bracket
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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 )
Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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Define Optimization Volumes and Design Rules • Draw directions • Obstacles • ~ 200.000 elements regular voxel mesh
Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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Optimization Submodel, Boundarys, Loads Cylinder Head
Alternator
Static: loads • Fbolt 50 kN + Fh 10 kN + Fh - 10 kN + Fv 10 kN + Fv - 10 kN 10 kN + Fl
Engine Block
Dr. D. Sprengel
EMS Ring
6/2007
5x
Dynamic: max. Eigenfreq.: • Alternator horz. + EMS • EMS local (>500Hz) • Alternator vert.
Topology Optimization of EMS Bracket
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Optimization Run Design Recommendation
Run OptiStruct
• Min. Compliance @ Static Loads 5x • Max. Eigenfrequencies No. 1,2,3 • Volume: 30% of design space (~ old bracket volume)
Iteration 19 Density >= 0.3 Color: casting constraints
Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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Robustness Check of Optimization Run Single Optimization Frequency (w/o static loads)
Main features with small design changes
Check balance between: Min. compliance ( static ) Max. Eigenfrequencies ( modal)
Changed weight factor: 10x small design changes
Influence of Volumefrac target : 20% instead of 30%
20% results in weaker design with same design features
Change of boundary conditions or loads
Not checked
Change of draw directions
Not checked:
Other OptiStruct features (maxmb)
Not used (model size)
The optimization seems to be robust, the final design was useful. Base features have been recommended for new CAD geometry.
Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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Opti CAD Geometry FE check
new part CAD / FE
• Modal analysis of complete P/Train: • Reduced participation of EMS • „1. Local“ EMS Mode from 470 Hz to • No check of stress distribution Dr. D. Sprengel
6/2007
681 Hz
Topology Optimization of EMS Bracket
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Next Task: Changed Engine Installation Angle, Position Prototype (449 Hz, local stress concentrations) improve it!
Changed bolt position results in a sharp corner near a thread Stress concentration
Dr. D. Sprengel
6/2007
Changed bolt position results in a deep hole ( cast draw ) Stress concentration
Topology Optimization of EMS Bracket
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Bracket II
Dynamic: Static :
Optimization Task
500 Hz Min. compliance
Topology Optimization
+ Stress reduction
OptiStruct
+
Engineering Judgement !!
The definition of design space + draw rules should lead to an optimization result with feasible stress distribution.
Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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Bracket II
Dr. D. Sprengel
6/2007
Optimization Model: Single / Split Draw
Topology Optimization of EMS Bracket
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Optimization Model: ‚Final Cut‘
Design space ‚Cut out‘ • to avoid stress concentration
Dr. D. Sprengel
6/2007
or
to reduce mass concentration
Topology Optimization of EMS Bracket
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Bracket II Optimization Run CAD
OptiStruct Dr. D. Sprengel
6/2007
CAD
Added features ( lifting eye, cover flange,…)
Topology Optimization of EMS Bracket
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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
Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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Stress Analysis: Bolt foces 50 kN + EMS vertical 10 kN
Prototype Design
Final Design
Critical high tension at corner
Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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Stress Analysis: Bolt foces 50 kN + EMS vertical 10 kN
Prototype Design
Final Design
Stress Analysis Bolt foces 50 kN + vertical EMS load 10 kN
Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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‚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
Dr. D. Sprengel
‚What structure do we really need?‘
6/2007
Topology Optimization of EMS Bracket
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Start Product Development with Optimized Design
Target setting
Cost of changes
Design changes Time
Concept
Product Development
Base design features by Optimization „First in Chain!“
Dr. D. Sprengel
6/2007
+
Job 1
Short time reaction with Optimization tool
Topology Optimization of EMS Bracket
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Education
Process Management • Opti CAD CAE
First in Chain!
CAE: Optimization • Take the lecture! • Improve process • Persuade people
What structure do we really need?
• • No ‚Design by Rules‘ • ‚Design by Need‘
Update ‚Engineering Judgement‘
All
Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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Final Message
Optimize ! Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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Thank You!
Dr. D. Sprengel
6/2007
Topology Optimization of EMS Bracket
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