cae analysis of an intake valve for bike application · ref comp conservati rding to the by the...

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EASC 20094th European Automotive Simulation Conference

Munich, Germany6-7 July 2009

Copyright ANSYS, Inc.

Figure 2 2. TH The sim

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2.1. THThe FE

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E SIMULAT

mulation proFEM analys

o the

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fatigue anao thero mec

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ed, as show

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TION PROC

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NALYSES as included

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s been the foute the folloe field withi

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Figure 3. The simulation procedure. The FEM analyses. The FEM model. Structural continuity across the interfaces has been assumed and modelled by forming a new part inside Design Modeler. 2.1.1. The calculation of the temperature field The dependence on the temperature of the thermal conductivity has been taken from Piaggio standards. 2.1.1.1. Steady-state conditions The temperature at the position P(x,y,z) within the valve has been defined as TS(x,y,z). 2.1.1.2. Transient conditions The maximum engine speed condition has been taken into account, because it is associated with the maximum forces acting on the valve. 60 engine cycles have been simulated, the duration of each being defined as Δ. The temperature at the position P(x,y,z) within the valve at the time t has been defined as TT(t,x,y,z). 2.1.2. The calculation of the stress field induced by the temperature The analysis has been carried out for [ ]∈ Δ Δt 59 ;60 (see par. 2.1.1.2). The stress tensor at the position P(x,y,z) and time t has been defined as Φ(t,x,y,z). 2.1.3. The calculation of the load/stress transfer functions Each transfer function Ψi(x,y,z) has been computed applying an unit load without constraining the system and exploiting the Ansys/Workbench Inertia Relief feature. 2.2. THE FATIGUE ANALYSES The valve is made of ET8 nitrided steel. The dependence on the temperature of its ultimate tensile stress (before nitriding) has been taken into account according to Piaggio standards, as shown in the following figure:




Figure 4 As for tuniformconditioeffect hUTS anlayer is 1990 MThe ET8The harfigure [2

Figure 5 Since thbeen asIt has beThe meGoodma

4. The simu

the steel's ly equal to

ons. TREF haas been ta

nd the surfaprescribedPa. 8 steel's fatrdness/temp2]:

5. The simu

he hardnesssumed thaeen assumeean stress an method.

ulation proce

UTS (beforo a referenas been chken into acace hardne to have a

tigue ratio hperature rel

ulation proce

ss does nott the nitridined that the effect on

edure. The

re nitriding)nce value hosen in a

ccount accoss inducedhardness o

has been aslationship fo

edure. The

t decreaseng effect remendurance the fatigue

fatigue ana

, the valve'TREF compconservati

ording to the by the nitr

of HV 600,

ssumed to bor a steel si

fatigue ana

when the tmains the slimit increa

e resistance

alyses. UTS

's temperatputed by thive way (see DIN 50 15riding proceaccording t

be 0.55 [1].imilar to the

alyses. Hard

temperaturesame irrespeases by 15%e has bee

S/temperatu

ture has behe FEM anee par. 4.150 standardess. Since to the DIN s

e ET8 is sho

dness/temp

e is lower tective of the

% due to then taken in

re curve.

een assumenalysis in t.1.1). The

d, which relthe valve's standard its

own in the f

erature cur

than 900 °Ce temperatue nitriding [3nto account

ed to be transient nitriding ates the nitrided

s UTS is

following

rve.

C, it has ure. 3]. t by the




The strethe FKMMultiaximethod 2.2.1. TThe anaas input 2.2.2. A single 3. TH 3.1. TH 3.1.1. TA zero-compon

Figure tempera A constand valv

Figure tempera Convecfigure:

ess gradienM recommeal stress st [5].

Thermal faalysis has bt.

Mechanicae engine cyc

E INITIAL A

HE FEM AN

The calcula-heat flow nent's symm

6. The initiature field. Z

tant and unve/seat inte

7. The initiature field. T

ction bound

nt effect on tndations [4tates have b

atigue been carried

al fatigue cle has bee

AND BOUN

NALYSES

ation of thecondition

metry:

ial and bouZero-heat fl

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ial and bouTemperatur

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en taken into

NDARY CO

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undary conre boundary

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resistance

ed to an eq

[ ]Δ Δ59 ;60 .

o account.

NDITIONS

ture field applied to

ditions. The

on.

undary cond

ditions. They conditions

been applied

has been ta

quivalent un

Φ(t,x,y,z) (s

o the follow

e FEM ana

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e FEM anas.

d to the su

aken into ac

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see par. 2.1

wing surfac

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een applied

alyses. The

urfaces show

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e calculation

wn in the f

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een used

odel the

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ve/guide

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Figure tempera CFD antempera

Figure tempera The filmconstan 3.1.1.1.At the reto be eq 3.1.1.2.With rTT(0,x,yhave be 3.1.2. TWith rethermal 3.1.3. TA unit lo

8. The initiature field. C

nalyses haature at the

9. The initiature field. T

m coefficiennt during the

Steady-staegions A anqual to the a

Transient reference y,z)=TS(x,y,zeen applied

The calculaeference to load.

The calculaoad, paralle

ial and bouConvection

ave been cA and B re

ial and bouThe film coe

nt and the e engine cy

ate conditiond B, the filaverage val

conditions to paragraz). Variableat regions

ation of theparagraph

ation of theel to the valv

undary conboundary c

carried out egions (see

undary conefficient and

ambient tcle.

ons m coefficienlues of the c

aphs 2.1.1e film coeffiA and B ac

e stress fieh 2.1.1.2, th

e load/streve axis, has

ditions. Theconditions.

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ditions. Thed the ambie

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nt and the acurves show

1.1 and 2icient and a

ccording to F

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ss transfers been appli

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te the film

e FEM ana

ent tempera

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2.1.1.2, it ambient temFigure 9.

d by the temature field

r functionsied to each

alyses. The

coefficient

alyses. Theture.

egion C ha

mperature h9.

has beemperature b

mperature TT(t,x,y,z) h

s of the follow

e calculation

t and the

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ave been a

have been a

en assumeboundary co

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wing region

n of the

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n of the

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used as

ns:




Figure 10. The initial and boundary conditions. The FEM analyses. The calculation of the load/stress transfer functions. Unit loads. 3.2. THE FATIGUE ANALYSES 3.2.1. Mechanical fatigue With reference to Figure 10, the variations of Fi during the engine cycle have been evaluated with a dynamic analysis, whose result has been the following:

Figure 11. The initial and boundary conditions. The fatigue analyses. The mechanical loads acting on the valve. Let θ be the engine angle. The stress tensor Ψ(x,y,z,θ) has been evaluated as

( ) ( ) ( )ii, x,y,z F x,y,zθ = θ∑ iΨ Ψ (see paragraph 2.1.3).

4. THE RESULTS 4.1. THE FEM ANALYSES 4.1.1. The calculation of the temperature field




4.1.1.1. Transient conditions The temperature field at the time t=50Δ and t=60Δ (see paragraph 2.1.1.2) has turned out to be the following:

Figure 12. The results. the FEM analyses. The calculation of the temperature field. Transient conditions. The temperature field. The temperature field at the time t=50Δ and t=60Δ (see paragraph 2.1.1.2) has turned out to be the following at the critical region (see Figure 2):

Figure 13. The results. The FEM analyses. The calculation of the temperature field. Transient conditions. The temperature field at the critical region. Comparing Figure 12 and Figure 13, at t=60Δ a temperature difference γ=40°C can be observed between the hottest point of the whole valve and the hottest point of the critical region. The same difference exists at t=50Δ. So it has been assumed that γ≠γ(t). Let ( ) { }Tx,y,z

T t max T (t,x,y,z)≡)

(see paragraph 2.1.1.2) for t 50 ;60∈ Δ Δ⎡ ⎤⎣ ⎦. Its time variation has

turned out to be the following:




Figure 1conditio ( )T t

)'s r

followin

Figure 1conditio Figure 1been usconditio

14. The resons. Maximu

relative mag figure:

15. The resons. Maximu

14 shows thsed to esti

ons:

ults. The FEum tempera

xima have

ults. The FEum tempera

hat at t=60Δmate the v

EM analyseature.

been interp

EM analyseature.

Δ the valve valve's max

es. The calc

polated by m

es. The calc

has not reximum tem

culation of th

means of a

culation of th

ached statiperature on

he tempera

function Γ(

he tempera

onary condnce it has

ture field. T

(t), as show

ture field. T

ditions yet. reached st

Transient

wn in the

Transient

Γ(t) has tationary




Figure 1conditio So the 492°C. critical strength(see pa 4.1.2. TThe Vofollowin

Figure 1tempera In the fregion is

16. The resons. Station

hottest poGiven the aregion in

h's computaragraph 2.2

The calculan Mises strg:

17. The resature. Von M

following figs shown:

sults. the FEary conditio

oint's maximassumptionstationary

ation, the wh2).

ation of theress distribu

sults. The FMises stres

gure the Vo

EM analyseons estimati

mum tempe about γ (secondition hole critical

e stress fieution at t=60

FEM analyses distributio

on Mises s

s. The calcion.

erature oveee above), tis (492-40) region has

eld induced0Δ (see pa

es. The calon.

tress variat

ulation of th

er time in sthe maximu)°C=452°C.s been assu

d by the temragraph 2.1

culation of

tion vs. tim

he temperat

stationary cum tempera. As for thumed to be

mperature 1.1.2) has tu

the stress f

me at two p

ture field. T

conditions iature attainehe ultimateat that tem

urned out to

field induce

points of the

Transient

is about ed at the e tensile perature

o be the

d by the

e critical




Figure 1tempera Figure 1 4.2. TH 4.2.1. TThe saffollowin

Figure 1 Figure 1 4.2.2. The saffollowin

18. The resature Von M

18 shows th

HE FATIGU

Thermal fafety factor g:

19. The res

19 shows th

Mechanicafety factor g:

sults. The FMises stress

hat the valve

UE ANALYS

atigue distribution

ults. The fa

hat the therm

al fatigue distribution

FEM analyses variation v

e is subject

SES

n at t=60Δ

tigue analy

mal stress f

n at t=60Δ

es. The calvs. time.

t to non-pro

(see parag

yses. Therm

field has ne

(see parag

culation of

portional fa

graph 2.1.1

mal fatigue. S

gligible fatig

graph 2.1.1

the stress f

tigue.

.2) has tur

Safety facto

gue effects.

.2) has tur

field induce

rned out to

or distributio

.

rned out to

d by the

o be the

on.

o be the




Figure 20. The results. The fatigue analyses. Mechanical fatigue. Safety factor distribution. The minimum allowable safety factor is lower than the minimum shown in Figure 20, so the valve has turned to be free of design flaws that can induce the failure under investigation, thus allowing the project team to focus on other possible causes. 5. CONCLUSIONS

• Ansys/WB has been used to assess the fatigue performance of an intake valve for a high-performance motorbike engine in the presence of bench-test failures.

• WB GUI has allowed to: o Easily carry out transient thermal analyses and feed their output to

subsequent structural ones; o Easily apply fairly complex thermal boundary condition

• The valve has turned to have been soundly designed, thus allowing the project team to focus on other possible cause for the failures.

6. REFERENCES

1. P.P. Milella – Progettazione a fatica – Consorzio TCN, 2003 2. Metals Handbook, Volume 1, Tenth Edition, Properties and Selection: Irons, Steels,

and High-Performance Alloys, Elevated-Temperature Properties of Stainless Steels, 1990, ASM International

3. Centro di informazioni del nickel S.p.A. – Acciai Tipizzati – Milano, 1962 4. FKM Richtlinie - Rechnerischer Festigkeitsnachweis für Maschinenbauteile - 4.,

erweiterte Ausgabe 2002, VDMA Verlag 5. W.N. Findley – Modified theories of fatigue failure under combined stress –

Proceedings of the society of experimental stress analysis, Vol. 14, No. 1, 1956




cae analysis of an intake valve for bike application · ref comp conservati rding to the by the...

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