tssN 1411- 947',1 Volume8 Nomor 3, Sepfember2008
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JURNA L TEKNIK MESIN ISSN l4l 1 - 947I,TERAKREDITASINomor: 43iDIKTIlKep/2008 Juntal Teknik Mesin terbit tiga kuli setallun patla bulan Jattuari, Mei tlart Septenber. Berisi nlisan yang cliangkat tlari husil pe nelitfun dart kajiart urnliti.s kriris di bidang Tchik Mesin
PenyuntingPelaksana Prof.Dr. Ir. Sutardi,M.Eng MT. Ir. SudjudDarsopuspito, ST. MT. Dr. BambangSudarmanta, Is BunyaminSuryo.ST. WahyuWijanarko.ST. Yohannes,STM. Khoirul Effendi.ST.
Ketua Penyunting Dr. lng. HermanSasongko Wakil Penyunting Prof. Dr. Ir.WajanBerata,DEA
Prof.Ir. Djati Nursuhud,MSME. Prof. Ir. I NyomanSutantra,MSc..PhD. Prof.Dr. Ir. TriyogiYuwono,DEA. Ir. BamtransDarvantoW.. MSME.. PhD.
PenyuntingAhli Mesin-MesinKont,ersiEnergi - Jurusan TeknikMesin ITS Aulomoti'e- JuntsurtTeknikMesin ITS hlekuika&Mesin Fluida - JurusanTehtik Mesin ITS Vibrusi.&SistemDinanis - Jurusan TeknikMesin ITS
SistentMcuu4fttktur&Onnnsi hldustri - .luntsort Tekrtik Mesin ITS Ir. Sudiyono Kromodihardjo. MSc., PhD. PErpinthhan Panus&Ternuxlincmtika Terapan - JLtrusanTeknik Mesin ITS Ir. Budi Utomo KukuhW, ME. Metalurgi - Jurusart Teknik Mesirt ITS Dr. Ir. AbdullahShahab,MSc. Perpinrlahan Panas&Ternutdirtrunika Teraprut ' Junrsan Tehtik Mesin ITS Dr. Eng.Ir. Prabowo.M.Eng. Mekcnika Benda Patkrt - Junrsurt Teknik Mesin ITS Dr. Ir. Agus Sigit Pramono,DEA Metrologi&Kalibrasi Dinensi - JuruscrrtTeknik Mesirt ITS Prof. Dr. Ing. I Made Londen Batan. ME. Departenlen Metalurgi durt Malerial -UI Prof. Dr. Ir. Johny Wahyuadi Soedarsono,DEA Perpindalnn Parns - Jurustrn Teknik MesinUCM Dr. Ir. Suhanan.DEA. Pe rltirrtlctltattPcrrtas&M asso - J u nt satt Teht ik M es irtU N D I P Dr. L'. Berkah FajarT, Dipl.lng. P rakt i si I rttlust ri. A ltl i Aexlt ttut it t Dr. [r. Iwan Kusmarwanto Tekrik Penbakaran - Jurustul Teknik MesinUGM Dr. Ing. Harwin Saptoadi. MSc.
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VolumeI Nomor 3, Sepfember 2A0g ISSN 1411 -9471, TERAKREDITASI
Nomor : a3lDlKiyKep/2008
Pembuatan Perangkat penjejak KerasManipulator Lengan Mekanis Dengan GDerajat Kebebasan EagusArthaya,Ali Sadiyoko, WiraSatria FiresafetyProperties of rropicarwoodsin conecarorimeter Test YuliantoSulistyoNugroho
halaman151- 161 hahman162_ l\l
Karakteristik AliranFluida di DalamDiffuser Dindino Datardengan AreaRatio 2]4
Bambang AripD., Sutardi, Suwarmin
halaman 172- IBl
Pengaruh Parameter danElemen Tensio-Aktif terhadap Morforogi Kolam penqelasan LasanpadaProses Tungsten InertGas AbdullahShahab hataman lg2_ lgg Experimental Method fortheDetermination of Stress ccncentratron Faetors of stepped-shafts of circular-to-square crosssection underpureTorsion Jamiatuf Akmal& AsnawiLubis halaman 1g4 - 200 A Detection of theDevelopment of cracksina Metallic structure UsingR - curveMethod (Acomparison withtheshifting Frequency r Method) WibowoHarsoNugroho & prantasiHarmiTjahjanti halariran 201_207 FormulasiEmpirls produkprosesMulli Akurasi Dimensi Material Freeform Fabri catio n Sus/oAdiWidyanto
pTOGenerafor Pengaru.h Penggunaan penggerak sebagai Mesin Pendingin penggerak terhadap sFocMotor Kapar riidisionat Mohammad AbuJami'in, Ekolutiiito
lll
halaman208- 217
halaman 2lg- 226
Jurnal Teknik Mesin, Volume 8, Nontor 3, September 2008
KATA PENGANTAR Pada penerbitan kali ini, JTM berhasil memuat artikel selain dalam jumlah yang banyak, juga dari beragam lingkup studi dan asal peneliti. Deltpan artikel yang berhasil diproses secaramerata tersebardalam tiga kelompok lingkup studi, yaitu: materiaVmetalurgi, desain, manufaktur, dan konversi energi. Dari delapan artikel. dua berasal dari peneliti dalam ITS dan selebihnya berasal dari peneliti luar ITS (Universitas Katolik Parahyangan,Universitas Indonesia Depok, Universitas Lampung,
universitas
Muhammadiyah sidoarjo,
universitas
Diponegoro,
Politeknik PerkapalanNegeri Surabaya). Dewan penyunting mengucapkan terima kasih kepada pa.mpengirim artikel dan penyunting ahli yang telah memberi sumbanganpada kualitasjurnal ini. Kami juga berterima kasih kepada seluruh pelanggan kami yang telah memanfaatkan JTM sebagaibahanrujukan dan inspirasi dalam penelitiannya. Kami mengajak para peneliti dan praktisi bidang Teknik Mesin untuk menulis artikel.pada Jurnal Teknik Mesin ini iterbit setiap Januari, Mei; dan September). Anikel anda akan dirujuk oleh pelanggan kami dari seluruh penjuru Indonesia. Akhirnya kami berharap semoga artikel-artikel berkualitas dalam jumal ini dapat bermanfaat bagi pembaca dan memberikan inspirasi dalam pengembangan teknologi di bidang rekayasamesin.
Dewan Penyunting
A Detection of the Develnpment of Cracks in a Metallic Structure Using R - Curve Method (A Comparison With the Shifting Frequency Method) Wibowo Harso Nugroho BPFT Lab.ol Hydrodinamics Indonesia WT-BPPH Surabaya, E-mail:
[email protected] Prantasi Hami Tjahjanti Kopeds VII (East of Java) Dpk: Department of Mechanical Engineering, University of Muhammadiyah Sidoarjo (UMSIDA) JI. Raya Gclam 250 Candi, Sidoq.o,61217 Phone: (031) 8921938, Fax: (031) 8949333
E-mail: pran
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Received January 23', 2008; correction received Juny 06'. 2008: approved October 30". 2008 Abstract This numerical study addresses the use of a nansferfincrior! techniquefor the detectwn of a crack in a metallic component. It will be shown that an array of piezoceramics (PZT) semr/achmror is best suited for this application This paper will also present a comparison with another method of detection which used a shifiing p e d frequency to approximately locate the position of the crack. The development ofcracks can be detected more accurately using R-curve method thanfrequency shiftingpkenomena. Keywords: piezoceramics (PZT), sensor - actuator, transfer function (TF), crack and crack detection.
Large stmctures such as bridges, pipelines, airplanes, ships and trains need to be kept healthy in order to serve the community. A shucture can be classified as damaged when a fault is present and is developing. Many things can cause this daniage but a common cause in metallic s t ~ c t u r e sdue to fatigue crack growrh. Thus detection of this damage at an early stage is critical. This detection can be carried out by continuously monitoring the structure using an automated system. The application of a smart stmcture concept is an appropriate tool for this monitoring purpose since the human interaction with the StNCIUre can thus be minimised. This situation, where a risk of human error is greatly reduced, will increase the accuracy Of the data acquisition that is required for assessing the damage in the StlU~turC.
Smart structure systems involve, the synergism of materials with embedded or surface mounted sertsors u.husi information is controlled and processed by intelligent system, which controls the actuator to perform the corrective action [I]. Thc conccpt of a smart stmcture is basically to combine sensor acbiator pairs into a host structure [2] (Fig. 1). An actuator excites a point or location of the host structure and the response from another selected point location is received by a sensor. Any change in the condition of the hmt sh'ucture will result in a change in the response. However, successful detection relies on the method that is used to analyse the data received from the sensor. By applying the correct and reliable method the engineer can make the right decision to prevent total failure of the structure.
202 J u m l TehikMesin, Volume 8. Nomor 3, September ZlMR Many investigations in the smart structure field have been conducted to develop methods for damage detection. Most of these methods are based on modal analysis. This analysis relies on changes in modal kequency because of the decreasing stiffness of the system. The major disadvantage of this hhnique is the difficulty of detecting the small crack because damage is a local phenomenon and modal information relates to the global response of the structure. Reports from ref. 1, 2 and 3 shown that the modal analysis lacks accuracy for detecting cracks with aspect ratio, ah < 0.1. 'This study will outline the limitation of this shifting frequency phenomenon (modal analysis) to detect small cracks but on the other hand to propose an alternative method to detect cracks in a better accuracy. The proposed method is called an R-curve method, This method works by:
1. Calculating the area under the frequency spectrum of the transfer function (TF)from a pair actuator and sensor
2. The frequency range for data analysis is restricted below the occurrence of the 1'' mode (avoid any difficulty arise from the modal analysis).
ne TF is obtained by acquiring the vibration in a certain range of broad band frequency from the PZT patches that attached on the surface of the structure. The PZT patches are distributed as mays. of actuators and sensors where they will be used lo generate and measure the vibration signature. This system is independent of the sensing
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& modal information from the structure since the detection and characterisation of damage only relies on the local inpudoutput signals of the piezoceramics. By manipulating the vibration spectrum of a particular pair of sensor and actuator, one can produce the TF of this actuator - sensor pair. The arrays of the PZT patches can also be used to locate the general area of the damage in the structure andlor degradation of a particular sensor - actuator pair. If the TF of a particular sensor-aetuator pair shows an anomaly, the region of the damageor degradation can be easily identified.
R-CURVE METHOD [3,4] R-curve methode have been applicated on the use of transfer function method lo detect the development craeks in a metallic structure [3] and monitoring of the severity of a cracked sthcture using discrete point measurements [4]. This seetion describes the basie equations and underlying assumptions that are used in both the numerical and experimental work to calculate the R - c w e . When the mounted P'A patch is actuated using an electrical field, it produces strain. This strain is also experienced by the host strueture. The in-plane actuation or sensing strain E of the PZT is proportional to the mechanical and elechici coupling coefficient d 3 ~of the ceramic and an applied fie'd ", and can be expressed as: E
=d3,V
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Flgure 1 Smart strucme concept.
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Nugroho. A Dew etion of zhe D e v e l o p k t of Cracks in a Mefdlic
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203
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If the bonding layers are thin and stiff, the strain of the PZX patch aeting as an actuator is equal to the strain of the corresponding area of the plate below. This is also true for the patch that acs as a sensor. Tlis situation is called a perfectly bonded actuator or sensor. Tne strain equation can then he written as.
?be PZT patch has three directional motions. Since the PZT patch that is used in this investigation is thin, the motion through the thickness direction is insignificant wmpared lo the others and can be, ignored. Hence, the relationship of the strain-displacement for small deformation and pure extension is:
peaks of amplitude so it is difficult to analyse the changes in the signal pattern To overcome this problem the changes in the signal pattern of the amplitude can be represented by the changes in the area under the TF frequency spectrum. This area under the TF frequency spectrum, R-curve, in a certain frequency range fD and fn is calculated by his following formula:
where , ATF is the amplitude of the 'iF frequency spectrum.
APPLICATIONS where: dL. = induced length of PZT patch under force or voltage excitation. On any actuator-sensor pair, a broadband input voltage is applied to the actuator and the sensor detecw the shuctural response to his input. The transfer funetion between the pair is then computed using equation (4):
where: Vb = vibration spectrum from the sensor, VkMt = vibration specfrom the actuator. The vibration spectrum V is defined as: Vk(a)= A, (o)eiek ("' ,
(5)
where: w = frequency, = phase angle, At = amplitude. In the experimental investigation, this vibration spechum is measured by the frequency analyser. However, in the numerieal investigation, the TF can he calculated using equation (1) to (4). The main purpose of this study is to analyse the changes in the signal pattern of the amplitude that is obtained by equation (4) in every achmtor-scnsor pair for every damage condition of the structure. how eve^, this vibration spectrum has many
Figure 2 shows a thin aluminium plate that is 200 x 400 x 2 m3, which is clamped on the shorter edges. A finite element plate model was made for the numerieal investigation to represent the clamped plate in the experimental investigation. The anxys of actuators and sensors ate bonded on the surface of the plate. The transfer function is measured from each actuator - sensor pair that iiscallad a direct TF measurement i.e. AnBn (n =1 ... 11). The pairs are numbered from the left side the right (Fig. 2). In rhis AnBn combination, row A is an array of sensors while row B is an army of actuators. Four different damage conditions in the smchlre we? made. First, the condilion that was called " nodamage". Then, a specific length of a crack was ma& on thc ccnm of the plate between row A and B. The TF measurement was calculated for every condition of the plate i.e. nodamage, damage1 (10mm crack, aspect ratio = 0.05), damage2 (20mm craek aspect ratio = 0.1). and damage3 (30mm crack, aspect ratio = 0.15) in order to identify changes in the R - curve of the TF.
RESULTS 'Ibis section presents the numerical results for the area where the sensor-actuator pair is able to detect the crack The number of pairs to be analysed in this numerical
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The results ul Fig. 8 shown that thc R-valuc decreasing appropriately with increasing crack sizes. So, wc can cxplain that two pairs, A4B4 and A585 that be detected by frrquency shining nhenomcoe there ate no sienificaut shift & & i n g for them. But when they detect using R-curve, show that for thc 20 nun, 30 mm crack case as the crack has gown closer to the pair A4B4 the area under the frequency spectrum appears to decrease with increasing crack lengths.
Figure 2. A Uun atunumum plate c ~ a m an p thc 2 sho&r edres with dislributed PZT a c m o t and
simulation can be greatly teduccd because of the symmetry. For the purpose of this study the pairs AnBn (n = 4, 5, 6) under the four damage conditions no damage, and 10 mm, 20 mm, 30 nun cracks are presented below. The results are initially presented as frequency s p e c h u h (Figs. 3, 4, and 5). It can be seen from Figure 3 there is no significant shift wcwting for the pair A4B4. A similar situation also occurs for pair A5B5 in Fig. 4. In Fig. 5 a shift appears to occur only at 30 mm crack. These results substantiates why modal analysis can only be used lo monitor cracks when the aspect ratio is greater than 01. The spectrums were subsequently manipulated to yield the Rcurve (using eq. 6). In Ag. 6, for the 20 mm. 30 mm crack case as the crack has growncloser to the pair A4B4 the area under the frequency specUum appear. to decrease with increasing crack lengths. In Fig. 7, as the 10 mm crack grew towards the pair ,4585 the R-value starts to decrease. As the crack increase and pass thc pair ASBS, for 20 mm and 30 rnm length. the area under the frequency 'spechum appears to decrease with further increase in crack length.
CONCLUSIONS From the results above, it is clear Illat the development of cracks can be detected more accurately using R-curve method than frequency shifting phenomena. REFERMCES
.
[I] Asundi,A., 1996 ''~ol&etric Sensors for Strain Mauremcnt and Damage Detection, Sman Stnrctures, Materials and MEMS: Bangalore, India [Z] Spillman Jr W.B., Skkis J.S., & Gardiner P.T.. 1996," Smart Material and Shuctures: What ate They ?" Sman Muter. Sfrucr. Vol5 pp 247-254. [3] Wibowo, H.N., 2001, "On the usc of Transfer Function Method to Detect the Development Cracks in a Metallic '- Shucture (an experimental study)", Conference of Marina Technology 20l.011 30-31 October 2001 at Johor, Malaysia. (41 Wibowo, H.N. 8: Chiu, W.K., 1998, "Monitoring of the severity of a cracked structure using discrete point measurements: ' A Numerical Study", COMADEMProceedings, pp. 905-917.
Nugroho. A Detection of the Development of C r m b in a Metnllic 205
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Figure 3 Transfer funcr~onof A484 in elery damage coqd~hon A585 T F Amplllude
Figure 4. Transfer function of A5B5 in every damage condition.
206
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Figure 5. Transfer function df A6B6 in every damage condition.
Rgure 6 R-curve of A4B4 m every damage con&tion.
Nugrolm, A Delection of rhe Developmeni of Crackr in a Metallic 207
Camparison ol A r e a Un&r Amplitude of a 5 8 5
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Figure 8. R - w e of A6B6 in cvevdamage condition.
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