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8/11/2019 Sprengel Ford

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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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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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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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Define Optimization Volumes and Design Rules

Draw directions Obstacles

~ 200.000 elementsregular voxel mesh


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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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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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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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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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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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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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Bracket II Optimization Model: Single / Split Draw


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Optimization Model: Final Cut

Design space Cut out to avoid stress concentration or to reduce mass concentration


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Bracket II Optimization Run CAD

CAD Added features

( lifting eye, cover flange,)

OptiStruct


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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


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Stress Analysis: Bolt foces 50 kN + EMS vertical 10 kN

Prototype Design Final Design

Critical

high tensionat corner


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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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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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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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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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Final Message

Optimize !


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Thank You!

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