Optimization in Consideration of Fatigue Results Shown by...

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Optimization in Consideration of Fatigue ResultsShown by the Example of an Aircraft Landing Gear System


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History

FEMFAT


• Cab Development• Chassis Development• Prototype Build• Vehicle Testing

• Cab Development• Chassis Development• Prototype Build• Vehicle Testing

• Gearboxes, CVT’s• Manual and automated

transaxles• Transfer Cases• Axle Drives• Planetary Wheel Hubs• Beam Axles

• Gearboxes, CVT’s• Manual and automated

transaxles• Transfer Cases• Axle Drives• Planetary Wheel Hubs• Beam Axles

• CAD/CAM/PDM/PLM Technology• Electrics• Electronics• ECS Software Products

• CAD/CAM/PDM/PLM Technology• Electrics• Electronics• ECS Software Products

• Structural Analysis• Vehicle Simulation• Strength / Fatigue Test Lab• Measurement Engineering• Acoustics and Vibration

Diagnostics

• Structural Analysis• Vehicle Simulation• Strength / Fatigue Test Lab• Measurement Engineering• Acoustics and Vibration

Diagnostics

• Engine Development• Engine Components

Development• Electronics• Injection Systems• Engine Integration• Marine Engines

• Engine Development• Engine Components

Development• Electronics• Injection Systems• Engine Integration• Marine Engines

• Product Definition• Optimization• Validation• Functional Development• Acoustics• Product Cost Optimization• Production Integration

• Product Definition• Optimization• Validation• Functional Development• Acoustics• Product Cost Optimization• Production Integration

Drivetrain & Axle Engineering

Commercial Truck Engineering

Engine Engineering

Simulation & Testing Services

Software & SupportFEMFAT

Production In Low Volumes

System Integration

Engineering Center STEYR – Range of Services


� Stress Tensors

� Material Properties

� Stress Gradient

� Mean Stress Influence

� MultiAXial Load

� Technological Influences

� Size Influence

� Temperature Influence

� PLASTic Deformations

� SPOT Joints s

� Anisotropical Behaviourof Arc WELDs

� etc.

S/N1 modifiedby FEMFAT

Load Cycles

Str

ess A

mplit

ude

S/N materialfrom specimen tests

Application of specimen data to components

• Finally : Component S/N curve including all influences

FEMFEMFATFAT – Local Stress Concept Crack Initiation


Notch Influence(Stress Gradient)

Surface TreatmentSurface Roughness

Mean Stress

Technological Size

Statistic

Thermo Mechanical Temperature

Tempering(for Tempering

Steel only) Cast MicroStructure

EffectivePlastic Strain

Boundary Layer

Isothermal Temperature

Plastic Fiber Orientation

FEMFEMFATFAT - Influence Factors


Fatigue Based OptimizationFatigue Based Optimization

FEMFEM

EnhancedEnhanced OptimizationOptimization byby using Fatigue Resultsusing Fatigue Results

optimal topology using only 30% of the design space‘s volume

Steel

FLP FLP BasedBased

OptimizationOptimization

Gray Cast Iron

ClassicClassic Stress / Stress / StrainStrain basedbased

OptimizationOptimization


Optimization regarding fatigue

Start

FE-ModelOptistruct

Stop condition

fulfilled?

Hyperstudy

New DesignYes

Adapted

FE-Model

No

Processcontrolled by theoptimzation tool

Life SolverDamage,

Safety Factor

Material


Multi axial fatigue analysis based on modal approach

FEMFAT-MAX

EnduranceSafety Factors

FE-Model

frequencydomain

Optistruct(linear)

Optistruct

Mode Stresses(real)

Mode ParticipationFactors (complex)

Inverse FourierTransformation

Static Behavior(Mean Stress)

Dynamic Loads

timedomain


� FEA Model

� Design Variables (Shape Optimization)

� Stress Based Optimization

� Fatigue Based Optimization

� Conclusion

Optimization regarding fatigue Landing Gear


FEA Model


Baseline

Design / Shape Variable

Design Variables


FEM FEM

Hyper Mesh / OptistructHyper Mesh / Optistruct

Hyper StudyHyper Study

EnhancedEnhanced OptimizationOptimization Loop By Loop By

Using HyperStudy (Stress Based)Using HyperStudy (Stress Based)

Shape optimization Minimize maximum stress value in critical area

Optimization StudyOptimization Study

(Stress Results) (Stress Results)


EnhancedEnhanced OptimizationOptimization By By


Objective definition: Minimize stress values (max. stress value from the critical node group)

Adaptive Response Surface method (HyperOpt)




Result design variables:



Stress Based Optimization (LC Braking)

BaselineNode 102153

v. Mises Stress: 762 MPA

Node 102153

Safety Factor:0.44


Stress Based Optimization (LC Braking)

Run 17 Node 102153

v. Mises Stress: 653 MPa

Node 102153

Safety Factor:0.48


FEM FEM

Hyper Mesh / OptistructHyper Mesh / Optistruct

Hyper StudyHyper Study


Using HyperStudy (Fatigue Based)Using HyperStudy (Fatigue Based)

Shape optimization Minimize maximum stress value in critical area

Optimization StudyOptimization Study

(Fatigue Results (Fatigue Results –– Safety Factor) Safety Factor)


Objective definition: Maximize safety factor

(min. safety factor value from the critical node group)








Result design variables:


Fatigue Based Optimization (LC Braking)

Baseline v. Mises Stress: 762 MPa

Safety Factor: 0.44


Fatigue Based Optimization (LC Braking)

Run 16 v. Mises Stress: 640 MPa

Safety Factor: 0.5


Summary

Fatigue based

Safety factor : 0.5 + 13%v. Mises stress : 640 MPa

Mass : 133.45 kg

Safety Factor : 0.48 + 9%v. Mises stress : 653 MPa

Mass : 133.67 kg

Stress based

Baseline

Safety factor : 0.44v. Mises stress : 762 MPa

Mass : 133.00 kg


yes noNew design

Basic FEM-model

Convergence criteria reached

Controller

AdaptedFEM-model

Life-Solver

Optistruct

Enhanced Optimization Loop

Including dynamic effects:Including dynamic effects:

Outlook

Motionsolve

yes noConvergence criteria reached

Optistruct

Life-Solver

Controller

AdaptedFEM-model

New design

Basic FEM-model


EigenfrequencyAnalysis

Frequency Response

Stress-distribution

Fatigue(FEMFAT)

Total life time

Attachment part

Damping 2%≤≤≤≤

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0

freqency [Hz]

acce

l er a

tio

[g]

ac

ce

lera

tio

n[g

]

frequency [Hz]

Representative Collective

Impact Analysis

Transient Response

(Quasi) Static Stress distribution(Load at CG, component depending)

Fatigue(FEMFAT)

Damping 6%

-3

-2

-1

0

1

2

3

4

5

6

0 0.1 0.2 0.3 0.4 0.5 0.6

time [s]

accel

er a

tion

[g]

≥≥≥≥

ac

ce

lera

tio

n[g

]

time [s]

RepresentativeCollective

Manual Approach


0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

5,0

0 5 10 15 20 25 30 35

Frequency [Hz]

Ac

ce

lera

tio

n [

g]

Beschl. x [g]

Beschl. y [g]Beschll. z [g]

Up to 2% modal damping stress combinationof different modes at the Eigenfrequencies is not necessary

30 279

21

324

0

50

100

150

200

250

300

350

1 2 3 4 6Mode

Mis

es

Ve

rgle

ich

sp

an

nu

ng

[N

/mm

2]

1st Mode is dominant

Maximum Stress

acceleration at frame: 0,18mm (harmonic, vertical)response: 3,2g (bracket outside)

Stress component for each Eigen-frequency:

Vo

n M

ises

Str

ess

Manual Approach: Spare wheel carrier (ξξξξ=1%)


Summary / Conclusion

Integration of FEMFAT leads to improved optimization

results:

Topology optimization leads to

global design

Shape optimization leads to

local design improvement

- adequate interpretation of static and dynamic loads

- consideration of load histories

- consideration of material properties

- many other influence factors can be considered


Summary / Conclusion

+ enables consideration of complex loads

Last-Zeitverlauf

-8000

-6000

-4000

-2000

0

2000

4000

6000

8000

1

12

23

34

45

56

67

78

89

10

0

11

1

12

2

13

3

14

4

15

5

16

6

17

7

18

8

19

9

Zeitschritt [0,2s]

Kra

ft [

N]

Längskraft F x Seitenkraft F y Aufstandskraft F z

+ enables consideration of material properties

NEndu

σσσσEndu

σσσσUlt

R =

0

R = -

8

1

2, 3

4

5

6, 78

9

Rp 0,2 Rmσm

σa

+ enables proper cosideration of static and dynamic load portion

+ allows consideration of durability, endurance and over loads

+ provides consideration ofmany other influences e.g. welds, spot welds

- needs additional CPU-time

Optimization in Consideration of Fatigue Results Shown by...

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