© Fraunhofer LBF

13th Users Conference on BiAxial Fatigue Testing

November 08th, 2017

Max Keilbach B. Eng. Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF www.lbf.fraunhofer.de

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LBF approach for testing rear axle hubs with loads up to 16 t

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CONTENT

Background information & motivation

Basic Idea

Strategy

Experimental stress analysis (ESA)

Load file adaption

Testing

Summary

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CONTENT

Background information & motivation

Basic Idea

Strategy

Experimental stress analysis (ESA)

Load file adaption

Testing

Summary

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LBF history on high rear axle loads & motivation

LBF ZWARPs can maintain rear axle loads up to 13 t

More requests from customers to test hubs with high axle loads

Higher axle loads more problems

Test rig

Premature bearing damages

Wear and tear of wheels and tires

High axle loads = up to 16 t

Motivation?

Implement a appropriate strategy to run tests more reliable

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CONTENT

Background information & motivation

Basic Idea

Strategy

Experimental stress analysis (ESA)

Load file adaption

Testing

Summary

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Basic Idea

Intentional removal of stiffness-relevant attachment-parts from the wheel end provokes a change of the stiffness ratio

Introduce higher stress amplitudes into the component

Reduce the forces and loads for the test rig

Smoother test run

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Stiffness-relevant parts

Attachment-parts next to the

flange area

Hub reduction casing

Drum brake

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CONTENT

Background information & motivation

Basic Idea

Strategy

Experimental stress analysis (ESA)

Load file adaption

Testing

Summary

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Experimental Stress Analysis | ESA

Target axle load is 16 t

Three ESAs were carried out

ESA I: 16.0 t original setup

ESA II: 16.0 t w/o stiffness relevant parts I

ESA III: 16.0 t w/o stiffness relevant parts II

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Experimental Stress Analysis Wheel end assembly ESA I

2x Wheels

Drum brake

Hub reduction casing

exemplary cross section hub

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Experimental Stress Analysis Wheel end assembly ESA II

2x Wheels

Substitute drum brake

exemplary cross section hub

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Experimental Stress Analysis Wheel end assembly ESA III

2x Wheels

exemplary cross section hub

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Experimental Stress Analysis | ESA Strain gauge positions

24 SG on hub

5 on radius behind wheel bolt head

7 on casting skin

10 on radius wheel centering

2 on casting skin

Test object and sampling

Axle: Rear – tandem axle

Tire: 325/95 R24

Wheel: 8.5 x 24” OS164

Hub: Cast iron EN-GJS 500-7

exemplary cross section hub

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Experimental Stress Analysis | ESA Results (I)

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

1,60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

RFS

val

ues

no

rmal

ized

Strain gauge no.

ESA I

ESA II

ESA III

de

fect

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Experimental Stress Analysis | ESA Results (II)

Increase of RFS values between 20-40%

42%36%

100%

51%

40%

104%

0%

20%

40%

60%

80%

100%

120%

6 14 23

Incr

ease

of

RFS

val

ue

com

par

ed t

o E

SA I

Strain gauge no.

ESA II ESA III

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Experimental Stress Analysis | ESA Results (III)

No effect for SG further away from flange area

2%

3%

0%

1%

1%

2%

2%

3%

3%

4%

16

Incr

ease

of

RFS

val

ue

com

par

ed t

o E

SA I

Strain gauge no.

ESA II ESA III

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CONTENT

Background information & motivation

Basic Idea

Strategy

Experimental stress analysis (ESA)

Load file adaption

Testing

Summary

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Load file adaption Procedure

With the load file adaption we ensure, that the correct loads are

reproduced on the ZWARP

Instrumented hub will be built into the ZWARP

Target is to reach the same stress amplitudes as on the ESA flat track

Multiple measurements are necessary to match load file to hub

The test rig loads were reduced about 20%

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Load file adaption Final load file

0

0,2

0,4

0,6

0,8

1

1,2

6 14 16 23

No

rmal

ized

RFS

val

ues

Strain gauge no.

Design spectra

Final load file

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CONTENT

Background information & motivation

Basic Idea

Strategy

Experimental stress analysis (ESA)

Load file adaption

Testing

Summary

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ZWARP Testing Results (I)

3 Test (1x 150%, 2x 100%)

Steady test run

No issues test rig

No premature bearing damages

Less wear & tear of wheels and tires

50% less tires & wheels were necessary

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CONTENT

Background information & motivation

Basic Idea

Strategy

Experimental stress analysis (ESA)

Load file adaption

Testing

Summary

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Summary

20-40% increase of RFS values are possible for this hub design, but not

every hub behaves same

Hub design is a major factor

The strategy works!

+ Projects w/ axle loads up 16 t can be executed at LBF

+ no failure of test rig

+ less wear and tear of wheels, tires and bearings

+ faster testing

+ same effects are possible for front axle hubs

It is solid strategy for the near future high load test rig planned

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Thank you for your attention!

… we will keep your wheels/hubs running

www.zwarp.de

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Contact

Fraunhofer Institute for Structural Durability and System Reliability LBF

Group Validation Wheel Related Components

Bartningstrasse 47, 64289 Darmstadt, Germany

Telefon: +49 6151 705-0, Fax: +49 6151 705-214

www.lbf.fraunhofer.de, www.zwarp.de

Max Keilbach B. Eng.

Project manager

Max.keilbach@lbf.fraunhofer.de,