Research Article Evaluation of Ultrasonic Nonlinear

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2013 Article ID 407846 6 pageshttpdxdoiorg1011552013407846

Research ArticleEvaluation of Ultrasonic Nonlinear Characteristics inHeat-Treated Aluminum Alloy (Al-Mg-Si-Cu)

JongBeom Kim1 and Kyung-Young Jhang2

1 Graduate School of Mechanical Engineering Hanyang University Seoul 133-791 Republic of Korea2 School of Mechanical Engineering Hanyang University Seoul 133-791 Republic of Korea

Correspondence should be addressed to Kyung-Young Jhang kyjhanghanyangackr

Received 19 July 2013 Revised 7 October 2013 Accepted 21 October 2013

Academic Editor Young Soo Choi

Copyright copy 2013 J Kim and K-Y Jhang This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The nonlinear ultrasonic technique has been known to be more sensitive to minute variation of elastic properties in material thanthe conventional linear ultrasonic method In this study the ultrasonic nonlinear characteristics in the heat-treated aluminumalloy (Al-Mg-Si-Cu) have been evaluated For this the specimens were heat treated for various heating period up to 50 hoursat three different heating temperatures 250∘C 300∘C and 350∘C The ultrasonic nonlinear characteristics of each specimen wereevaluated bymeasuring the ultrasonic nonlinear parameter 120573 from the amplitudes of fundamental and second harmonic frequencycomponents in the transmitted ultrasonic wave After the ultrasonic test tensile strengths and elongations were obtained by thetensile test to compare with the parameter 120573 The heating time showing a peak in the parameter 120573 was identical to that showingcritical change in the tensile strength and elongation and such peak appeared at the earlier heating time in the higher heatingtemperature These results suggest that the ultrasonic nonlinear parameter 120573 can be used for monitoring the variations in elasticproperties of aluminum alloys according to the heat treatment

1 Introduction

To evaluate material degradation destructive tests such astensile test impact test and bending test are commonlyused However the destructive tests require preparation ofspecimens separately from the operating structures and thespecimens cannot be reused after test Therefore in order tosave time and cost the nondestructive evaluation techniqueis preferred

Ultrasonic method is a common nondestructive methodto evaluate the material degradation since the propagationcharacteristics of ultrasonic wave is very closely associatedwith the elastic properties of material [1] Generally whenthe material is degraded the elastic property of materialwill be changed so that if we can monitor the change ofelastic properties then the degradation can be evaluatedFor this purpose most of ultrasonic methods measure thesound velocity or attenuation of amplitude the linear elasticconstant can be estimated by measuring the longitudinalwave velocity and the shear wave velocity [2] Also the

correlation between the attenuation of ultrasonic wave andthe microstructural change such as phase transformationor grain size growth has been reported [3] And resonantfrequency is dependent on the elastic properties of materialas well So the linear elastic constant also can be estimated byusing resonant frequency method [4]

Nevertheless those techniques are still less sensitive to theminute degradation affected by precipitation or dislocation[5] Thus those conventional ultrasonic methods will not beable to evaluate the degradation induced by heat treatment inaluminum alloy effectively since the thermal degradation inaluminum alloy by heat treatment is generally known to berelated to the behavior of precipitation [6]

On the other hand the nonlinear ultrasonic techniquehas been considered as a potential method since it hashigher sensitivity to the minute degradation [7 8] When anultrasonic wave is transmitted in a material the waveformis distorted by the nonlinear elastic property of material andthe harmonic waves are generated The nonlinear ultrasonictechnique uses this nonlinear ultrasonic effect to evaluate

2 Advances in Materials Science and Engineering

Oscilloscope(lecroy WS452)

Pulser receiver(panametrics PR500)

Pulse generation

Trigger

RITEC RAM-5000

Receiving echo signal

Transmitter

Receiver

100 mm

20 mm

Figure 1 Experimental system to measure the ultrasonic nonlinear parameter

0 2 4 6 8 10 120

01

02

03

04

05

06

07

08

Frequency (MHz)

Mag

nitu

de

A1

A2

FFT result

(a)

008 009 01 011 012 013 014 015 016 0172

25

3

35

4

45

5

55times10minus3

A21

A2

120573998400 =A2

A21

(b)

Figure 2 (a) Magnitude spectrum of the received signal and (b) experimental result to show the dependency of the second-harmonicamplitude on the power of fundamental frequency component

1111213141516171819

0 10 20 30 40 50

Nor

mal

ized

ultr

ason

icno

nlin

ear p

aram

eter

Heat hour (h)

250300350

Figure 3 The ultrasonic nonlinear parameter obtained from threeheating temperatures (250∘C 300∘C and 350∘C) where the data wasnormalized by the value of ultrasonic nonlinear parameter obtainedfrom no heat-treated specimen

changes in elastic property of material which measures theultrasonic nonlinear parameter 120573 defined by the ratio of thesecond-order harmonic amplitude and the power of funda-mental frequency component [7 9]The ultrasonic nonlinearparameter is related to the nonlinear elastic constants [1011] which is expected to be more sensitive to the minutedegradation of material than the linear elastic constant

This paper is to demonstrate the effectiveness of ultra-sonic nonlinear parameter for the evaluation of thermaldegradation in the heat treated aluminum alloy (Al-Mg-Si-Cu) For this purpose the specimens were heat treated forvarious heating periods up to 50 hours (1 2 5 10 20 and50) at three different heating temperatures 250∘C 300∘Cand 350∘C 5MHz tone burst longitudinal wave was used tomeasure the ultrasonic nonlinear parameter The amplitudesof 5MHz and 10MHz components of the received signal wereestimated by using (fast Fourier transform) FFT to obtainthe ultrasonic nonlinear parameter After the ultrasonic test

Advances in Materials Science and Engineering 3

0 05 1 150

50

100

150

200

250

Strain ()

Stre

ss (M

Pa)

50 h

20 h0sim

(a)

05 1 150

0

50

100

150

200

250

Strain ()

Stre

ss (M

Pa)

0sim2 h

5sim50 h

(b)

05 1 150

0

50

100

150

200

250

Strain ()

Stre

ss (M

Pa)

0 h1 h2 h5 h

10 h20 h50 h

0 h

50 h1sim

(c)

Figure 4 Stress-strain curve obtained from the tensile test for three heating temperatures (a) 250∘C (b) 300∘C and (c) 350∘C

tensile strengths and elongations were obtained by the tensiletest to be compared with the parameter 120573

2 Ultrasonic Nonlinear Parameter

To evaluate the ultrasonic nonlinear characteristics a single-frequency ultrasonic wave is launched into the specimenand the signal of the ultrasonic wave transmitted throughthe material is received In this process the single-frequencyultrasonicwave is distorted due to the elastic nonlinearity andthe second harmonic wave is generated Thus the receivedsignal is composed of not only the fundamental frequencywave but also the second harmonic wave The measurementof harmonic generation for microstructural characterizationis typically aimed at determining the value of ultrasonicnonlinear parameter 120573 defined as follows

120573 =81198602

11986021

1198962

119909 (1)

where1198601and119860

2are the amplitudes of fundamentalwave and

the secondharmonicwave respectively119896 is thewave numberand 119909 is the wave propagation distance In our experimentssince k and x are constants the quantity 1205731015840 is measured asfollows [12]

120573 prop 1205731015840 =1198602

11986021

(2)

3 Experimental Procedure

The material of specimen is aluminum casting alloy and itschemical proportion is shown in Table 1


0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)

250∘C yield strength and elongation

(a)

0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)


(b)

0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)

Yield strengthElongation


(c)

Figure 5 Yield strength and elongation obtained from the result of the tensile test for three heating temperatures (a) 250∘C (b) 300∘C and(c) 350∘C

Table 1 Chemical proportion of aluminum alloy (in wt)

Al Si Ni Cu Zn Mg FeChemicalproportion () 770 138 111 369 314 090 036

The size of specimen is 100mm times 100mm times 20mm Weprepared 18 specimens heattreated in 18 different heating con-ditions three different heating temperatures (250∘C 300∘Cand 350∘C) and six different heating period (1H 2H 5H10H 20H and 50H) at each heating temperature This heattreatment is a kind of accelerated reliability test condition togenerate degradation in the tensile properties Including anintact specimen without heat treatment the total number ofspecimen is 19

In experiment a measurement system with contacttransducers was constructed as shown in Figure 1 Signalcontrol is mainly based on the high power pulser (RAM5000 RITEC USA) that drives a transmitter Transmittingfrequency was set to 5MHz so that a 5MHz narrowbandtransducer is used as the transmitter The receiver detectsthe ultrasonic wave transmitting the specimen A 10MHznarrowband transducer was used as the receiver to detectsecond harmonic wave sensitively

In order to measure the parameter 1205731015840 the amplitudeof the fundamental frequency component and the second-harmonic amplitude were obtained by FFT of the receivedsignal as shown in Figure 2(a) Figure 2(b) shows the relation-ship between 1198602

1

and1198602 which is obtained by increasing the

input power for the intact specimenbefore the heat treatmentWe can see clearly the linear relationship satisfying (2) andthen the ultrasonic nonlinear parameter 1205731015840 is determined


8081828384858687888990

0 10 20 30 40 50Heat hour (h)

250300350

Youn

grsquos m

odul

us (G

Pa)

Figure 6 Youngrsquos modulus obtained by ultrasonic measurement oflongitudinal wave velocity and shear wave velocity for three heatingtemperatures (a) 250∘C (b) 300∘C and (c) 350∘C

from the slope of the fitted line For all specimens wemeasured the ultrasonic nonlinear parameters in this way

4 Results

Figure 3 shows the ultrasonic nonlinear parameter obtainedfor all specimens Three curves are corresponding to threeheating temperatures (250∘C 300∘C and 350∘C) where thedata was normalized by the value of ultrasonic nonlinearparameter obtained from the intact specimen Maximumfluctuation in the repetition of measurement was less than3 Results showed that a typical peak appeared that isat 250∘C heating temperature the peak appeared at 20-hourheat (485 increase as compared with intact specimen) andin 300∘C heating temperature the peak appeared at 5-hoursheat (543 increase as compared with intact specimen)From these results it is expected that the peak appearedearlier in the higher heating temperature At 350∘C heatingtemperature however we could not see a peak earlier than 5-hours heat We can predict only that the peak of ultrasonicnonlinear parameter might occur earlier than 1-hour heatThedata shown in dotted line in the figure is just hypothetical

Figure 4 shows the stress-strain curves obtained from thetensile test We can see a dramatic change at some heat-treatment hoursThat is at 250∘C and 300∘C heating temper-atures the stress-strain curves were dramatically changed atheat treatment time between 20 and 50 hours (165 increaseof elongation 322 decrease of yield strength) and between2 and 5 hours (117 increase of elongation 310 decreaseof yield strength) respectively These results showed that theheat treatment time causing drastic change of curvature inthe stress-strain curve is very similar to the heat treatmenttime showing a peak in the ultrasonic nonlinear parameter At350∘C heating temperature such dramatic change appearedat heat treatment time between 0 and 1 hour (387 increase

of elongation 721 decrease of yield strength) which meansthat the critical microstructural change already happenedprior to 1 hour heat This result proves our hypothesis thatthe first peak of ultrasonic nonlinear parametermay occurredearlier than 1-hour heat at 350∘C heating temperature Fromthese we can conclude that the first peak in the ultrasonicnonlinear parameter is strongly correlated with the drasticchange of curvature in the stress-strain curve

Figure 5 shows the changes in elongation and yieldstrength according to the heat treatment time which wereobtained from the tensile test The increment of elongationand the decrement of yield strength are bigger at the higherheating temperature Also at the heating hours specificallymentioned perviously the elongation drastically increasedand the yield strength rapidly decreased

Physically the ultrasonic nonlinear parameter is relatedto the thrid order nonlinear elastic constant and this non-linear elastic constant is very sensitive to the change incomposition of material The aluminum alloy tested in thisstudy is the casting alloy (Al-Mg-Si-Cu) Generally this alloyis thermally aged when exposed to high-temperature envi-ronment and the precipitations (such as Al

2Cu Mg

2Si) are

created and transformed which is reduced to the change ofelastic property Resultantly the curvature in the stress-straincurve varies The ultrasonic nonlinear parameter detectedwell such variation Contrarily the linear elastic constantobtained from the conventional ultrasonic method based onthe sound velocity measurement did not show any typicalchange according to the heat-treatment time and the heatingtemperature Figure 6 shows the measurement result of thelinear elastic constant (Youngrsquos modulus)

5 Conclusions

The ultrasonic nonlinear parameters in the heat-treatedaluminum alloy (Al-Mg-Si-Cu) specimens have been mea-sured and its effectiveness to evaluate the critical changein the elastic properties due to the thermal aging at hightemperature was demonstrated Specimens were heat treatedat three different heating temperatures (250∘C 300∘C and350∘C) with six different heat treatment periods (1H 2H5H 10H 20H and 50H) After the ultrasonic test tensilestrengths and elongations were obtained by the tensile test tocompare with the ultrasonic nonlinear parameter

A typical peak appeared in the measured ultrasonic non-linear parameter according to the heating time at each heatingtemperature and this peak appeared earlier in the higherheating temperature That is in 250∘C the peak appeared at20-hours heat and in 300∘C the peak appeared at 5-hour heatIn 350∘C such peak was expected to occur earlier than 1-hour heating From the tensile tests these heating periodswere found to be identical to those when the curvatures ofstress-strain curve were dramatically changed with the rapidincrement of elongation and the sharp decrement of yieldstrength

From these we can conclude that the first peak inthe ultrasonic nonlinear parameter is strongly correlatedwith the drastic change of curvature in the stress-strain


curve and that the nonlinear ultrasonic method is useful toevaluate the critical change of elastic property by thermaldegradation in heat treated aluminum alloys Note that thelinear elastic constant measured by conventional ultrasonicmethod based on the sound velocity measurement did notshow any critical change according to the heating time andthe heating temperature

Acknowledgment

Thisworkwas financially supported by theNational ResearchFoundation of Korea (NRF) Grant funded by the Koreangovernment (NRF-2013M2A2A9043241)

References

[1] S H Baek T H Lee C S Kim and K Y Jhang ldquoUltrasonicnonlinearity measurement in heat treated SA508 alloy influ-ences of grains and precipitatesrdquo Journal of the Korean Societyfor Nondestructive Testing vol 30 no 5 pp 451ndash457 2010

[2] M Kikuchi M Takahashi and O Okuno ldquoElastic moduli ofcast Ti-Au Ti-Ag and Ti-Cu alloysrdquo Dental Materials vol 22no 7 pp 641ndash646 2006

[3] A Badidi Bouda S Lebaili and A Benchaala ldquoGrain sizeinfluence on ultrasonic velocities and attenuationrdquo NDT amp EInternational vol 36 no 1 pp 1ndash5 2003

[4] MAGNAFLUX Magnaflux Quasar 4000 Quality Test Systems2013 httpwwwquasarintlcomndt-products

[5] U S Park I K Park and C S Kim ldquoA study on the evaluationof material degradation for 225Cr-1Mo steel by ultrasonicmeasurementsrdquo Transactions of the Korea Society of MachineTool Engineer vol 10 no 3 pp 61ndash67 2001

[6] P Palanichamy M D Mathew S Latha et al ldquoAssessingmicrostructural changes in alloy 625 using ultrasonic waves andcorrelation with tensile propertiesrdquo Scripta Materialia vol 45no 9 pp 1025ndash1030 2001

[7] K-Y Jhang ldquoApplications of nonlinear ultrasonics to the NDEof material degradationrdquo IEEE Transactions on UltrasonicsFerroelectrics and Frequency Control vol 47 no 3 pp 540ndash5482000

[8] G E Dace P B Thompson and L J H Brash ldquoNonlinearacoustics a technique to determine microstructural changes inmaterialrdquo in Review of Progress in Quantitative NondestructiveEvaluation vol 10 pp 1685ndash1692 Plenum Press New York NYUSA 1991

[9] J K Na J H Cantrell and W T Yost ldquoLinear and nonlinearultrasonic properties of fatigues 410Cb stainless steelrdquo inReviewof Progress inQuantitativeNondestructive Evaluation vol 15 pp1347ndash1351 Plenum Press 1996

[10] T KunduUltrasonic and Electromagnetic NDE for Structure andMaterial Characterization-Engineering and Biomedical Applica-tion CRC Press 2012

[11] J-Y Kim L J Jacobs J Qu and J W Littles ldquoExperimentalcharacterization of fatigue damage in a nickel-base superalloyusing nonlinear ultrasonic wavesrdquo Journal of the AcousticalSociety of America vol 120 no 3 pp 1266ndash1273 2006

[12] I H Choi T H Lee and K Y Jhang ldquoEvaluation of fatiguedegradation using nonlinear ultrasonicsrdquo Review of Progress inQuantitative Nondestructive Evaluation vol 29 pp 1433ndash14382011

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Oscilloscope(lecroy WS452)

Pulser receiver(panametrics PR500)

Pulse generation

Trigger

RITEC RAM-5000

Receiving echo signal

Transmitter

Receiver

100 mm

20 mm

Figure 1 Experimental system to measure the ultrasonic nonlinear parameter

0 2 4 6 8 10 120

01

02

03

04

05

06

07

08

Frequency (MHz)

Mag

nitu

de

A1

A2

FFT result

(a)

008 009 01 011 012 013 014 015 016 0172

25

3

35

4

45

5

55times10minus3

A21

A2

120573998400 =A2

A21

(b)

Figure 2 (a) Magnitude spectrum of the received signal and (b) experimental result to show the dependency of the second-harmonicamplitude on the power of fundamental frequency component

1111213141516171819

0 10 20 30 40 50

Nor

mal

ized

ultr

ason

icno

nlin

ear p

aram

eter

Heat hour (h)

250300350

Figure 3 The ultrasonic nonlinear parameter obtained from threeheating temperatures (250∘C 300∘C and 350∘C) where the data wasnormalized by the value of ultrasonic nonlinear parameter obtainedfrom no heat-treated specimen

changes in elastic property of material which measures theultrasonic nonlinear parameter 120573 defined by the ratio of thesecond-order harmonic amplitude and the power of funda-mental frequency component [7 9]The ultrasonic nonlinearparameter is related to the nonlinear elastic constants [1011] which is expected to be more sensitive to the minutedegradation of material than the linear elastic constant

This paper is to demonstrate the effectiveness of ultra-sonic nonlinear parameter for the evaluation of thermaldegradation in the heat treated aluminum alloy (Al-Mg-Si-Cu) For this purpose the specimens were heat treated forvarious heating periods up to 50 hours (1 2 5 10 20 and50) at three different heating temperatures 250∘C 300∘Cand 350∘C 5MHz tone burst longitudinal wave was used tomeasure the ultrasonic nonlinear parameter The amplitudesof 5MHz and 10MHz components of the received signal wereestimated by using (fast Fourier transform) FFT to obtainthe ultrasonic nonlinear parameter After the ultrasonic test


0 05 1 150

50

100

150

200

250

Strain ()

Stre

ss (M

Pa)

50 h

20 h0sim

(a)

05 1 150

0

50

100

150

200

250

Strain ()

Stre

ss (M

Pa)

0sim2 h

5sim50 h

(b)

05 1 150

0

50

100

150

200

250

Strain ()

Stre

ss (M

Pa)

0 h1 h2 h5 h

10 h20 h50 h

0 h

50 h1sim

(c)





120573 =81198602

11986021

1198962

119909 (1)

where1198601and119860



120573 prop 1205731015840 =1198602

11986021

(2)




0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)


(a)

0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)


(b)

0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)



(c)







1




8081828384858687888990

0 10 20 30 40 50Heat hour (h)

250300350

Youn

grsquos m

odul

us (G

Pa)



4 Results






2Cu Mg

2Si) are


5 Conclusions






Acknowledgment


References




















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 05 1 150

50

100

150

200

250

Strain ()

Stre

ss (M

Pa)

50 h

20 h0sim

(a)

05 1 150

0

50

100

150

200

250

Strain ()

Stre

ss (M

Pa)

0sim2 h

5sim50 h

(b)

05 1 150

0

50

100

150

200

250

Strain ()

Stre

ss (M

Pa)

0 h1 h2 h5 h

10 h20 h50 h

0 h

50 h1sim

(c)





120573 =81198602

11986021

1198962

119909 (1)

where1198601and119860



120573 prop 1205731015840 =1198602

11986021

(2)




0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)


(a)

0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)


(b)

0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)



(c)







1




8081828384858687888990

0 10 20 30 40 50Heat hour (h)

250300350

Youn

grsquos m

odul

us (G

Pa)



4 Results






2Cu Mg

2Si) are


5 Conclusions






Acknowledgment


References




















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)


(a)

0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)


(b)

0 5 10 20100

150

200

250

300

Heat hour (h)

Yiel

d str

engt

h (M

Pa)

5005

075

1

125

15

Elon

gatio

n (

)



(c)







1




8081828384858687888990

0 10 20 30 40 50Heat hour (h)

250300350

Youn

grsquos m

odul

us (G

Pa)



4 Results






2Cu Mg

2Si) are


5 Conclusions






Acknowledgment


References




















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




8081828384858687888990

0 10 20 30 40 50Heat hour (h)

250300350

Youn

grsquos m

odul

us (G

Pa)



4 Results






2Cu Mg

2Si) are


5 Conclusions






Acknowledgment


References




















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Acknowledgment


References




















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article Evaluation of Ultrasonic Nonlinear