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Durability Assessments ofMotorcycle Handlebars

Ken-Yuan Lin, Jung-Ming Chang, Jui-Hung Wu, Chih-Huang Chang

Automotive Research and Testing Center

Shun-Hui Chang, Jiun-Ren Hwang

National Central University

Chin-Ping Fung

Chung Cheng Institute of Technology

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CONTENT

Introduction

Objective

Theory

Methods

Results and Discussion

Conclusion

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INTRODUCTION

Motorcycle Industry is one of

the most important industries in

Taiwan.

Fatigue Cracks of motorcycle

structures are sometimes foundto initiate at welded regions

during structural development.

It is necessary to understand

what fatigue analysis approachis suitable for this product.

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OBJECTIVE

The purpose of this study is

to characterize fatigue

behavior of the motorcycle

handlebar, and develop asuitable durability

analysis approach for it.

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THEORY

Influence of Fatigue Life of the Welded Joint :

Geometric Shape, Material Property, Residual Stresses

and Weld Defects.

BS 5400 : Part 10 Standard

Nine Classes : Load Type, Weld Geometry and

Location of Potential Crack Initiation.

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THEORY

When Nf 107, the correlation between fatigue life and nominal

stress is:

where

Nf: fatigue life,

K : constant relating to the mean-line of the statistical analysis

results,

z : number of standard deviations below the mean-line,

s : standard deviation of Log Nf,

m : inverse slope of mean-line log S Log Nfcurve,

Sn

: nominal stress.

nf SLogmzKLogNLog =

BS 5400 :

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THEORY

When Nf> 107, the equation is:

Gurney modified equation was to consider thickness effect.

The modified equations are as follows:

When Nf 107,

When Nf> 107,

t : thickness (mm)

25.022)(t

nf

SLogmzKLogNLog =

25.022

)(

)2(

t

nf

SLogmzKLogNLog +=

nf SLogmzKLogNLog )2( +=

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4. Road Simulation

METHODS

1. Target Component and Target Track

2. Stress Analysis

3. Data Acquisition of Field Test

5. Durability Tests

6. Evaluation of Fatigue Life

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The motorcycle handlebar

The vehicle used in this

study was a 150c.c. scooter

type of motorcycle.

We selected motorcycle

handlebar as the targetcomponent.

1. Target Component and Target Track

METHODS

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The Belgium (Pave) road

The target track is the

Belgium (Pave) road of the

proving ground in ARTC(Automotive Research and

Testing Center in Taiwan).

1. Target Component and Target Track

METHODS

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2. Stress Analysis

The MSC.Nastran finite

element software was adoptedto carry out the stress and

strain analysis and to find out

possible failure locations.

METHODS

Stress distribution of the motorcycle

handlebar (loading angle 26o)

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3. Data Acquisition of Field Test

The Field Strain : Measurement

from the Belgium road Speed : 30 km/hr

Sampling Rate : 1 kHz

Data Recorder: IMC-CRONOS Field test on the Belgium (Pave) road

METHODS

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4. Road Simulation

To obtain the load history

in the durability test.

Strain - remote parameter

control (RPC) technique

Controller - IST-8800

Software - RS-SPiDAR

Motorcycle Handlebar

Servo Hydraulic Actuator

Force input of the durability test

METHODS

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Setup of the durability test

5. Durability Tests

(1x) Strain History : up to 800 hours

(3x, 3.5x, 4x and 4.5x) : within 48

hours

Durability Test : Single Actuator

Periodical Inspection : Crack

Initiation

METHODS

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METHODS

6. Evaluation of Fatigue Life

S-N Approach : EstimatedStress-Life Curves

BS 5400 Approach : the class,

thickness, probable failure ofwelded joint

BS 5400 standard with the

Gurney thickness modification

approach Rainflow cycle counting

Miners damage accumulation

Rainflow cycle counting

Life cycles

Stressrange(MPa)

Estimated stresslife curve of

JIS S25C steel

Stresslife curve of BS 5400

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When the force downward at

an angle of 26o from the

horizontal, the crack was

produced in the weldedregion (area A), where the

handle was welded to the main

pipe.

Stress distribution of the motorcycle handlebar

(loading angle 26o)

1. Analysis of Loading Angle and

Failure Location

26

A

Failure location of motorcycle handlebar in

durability test (loading angle 26o)

RESULTS AND DISCUSSION

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If the angle of force input was

increased to 36o from the

horizontal, The actual cracks

would initiate at the welded

region - area B.

Stress distribution of the motorcycle handlebar(loading angle 36o)

36

B

Failure location of motorcycle handlebar in

durability test (loading angle 36o)

1. Analysis of Loading Angle andFailure Location

RESULTS AND DISCUSSION

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Failure location of the handlebar

in the full vehicle durability test

1. Analysis of Loading Angle andFailure Location

In conclusion, the loading

direction of the servo hydraulicactuator for the follow-up

durability tests was defined at

26 from the horizontal.

RESULTS AND DISCUSSION

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Response strain history in the

durability test (3x magnification)

A portion of original and reproduced

strain histories (3x magnification)

reproduced by remote parameter control

technique

2. Evaluation of Fatigue Life

RESULTS AND DISCUSSION

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Number of Magnification of

Strain History

R.M.S. of OriginalStrain

( g )

R.M.S. of ReproducedStrain

( g )

Error

(%)

3 279.2 275.6 1.29

3.5 325.7 321.3 1.35

4 372.2 366.9 1.42

4.5 418.8 412.5 1.50

Note: R.M.S. (root mean square)

Results of road simulation

2. Evaluation of Fatigue Life

RESULTS AND DISCUSSION

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The failure location at welded region and the G class of BS 5400 standard

2. Evaluation of Fatigue Life

RESULTS AND DISCUSSION

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Specimen No.Ultimate Strength

(MPa)Yield Strength

(MPa)Elongation (%)

1 537.9 506.8 14.8

2 532.5 507.4 17.0

3 548.2 521.7 15.8

Average 539.5 512.0 15.9

Results of tensile tests for motorcycle handlebar are: ultimate strength

= 539.5 MPa, yield strength = 512.0 MPa, elongation = 15.9%.

2. Evaluation of Fatigue Life

RESULTS AND DISCUSSION

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RESULTS AND DISCUSSION

Fatigue Life (blocks)Strain History

(Number ofMagnification) Experiment Traditional S-NApproach

BS 5400

Standard BS 5400 with

Gurney Thickness

Modification

1 56612300 3426 19374

2 424982 389 2126 3 1418 51703 115 625

3.5 756 24616 72.8 396 4 395 13120 48.6 265

4.5 129 8625 48.3 263

2. Evaluation of Fatigue Life

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CONCLUSION

By the CAE analysis and experimental results, the loadingdirection of the servo hydraulic actuator for the

durability test was defined at 26 from the horizontal.

? BS 5400 standard with the Gurney thicknessmodification approach? is suitable to assess the

durability of motorcycle handlebars, the difference

between experiment and prediction is within 2.5 times.

In the future, this approach could be applied to thedurability assessment for weldments of automobiles.

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Thanks for YourThanks for Your

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