Investigation of the pseudoelastic behaviour in two commercial NiTi alloys: experiments and modelling

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1 Proc. Etonian Acad. Sci. Phy. ath., 2007, 56, 2, Invetigation of the peudoelatic behaviour in two commercial NiTi alloy: experiment and modelling Caper van der Eijk a, Jim Stian Olen b, and Zhiliang Z. L. Zhang b a SINTEF aterial and Chemitry, Alfred Getz vei 2, 7465 Trondheim, Norway; caper.eijk@intef.no b Department of Structural Engineering, Norwegian Univerity of Science and Technology, 7491 Trondheim, Norway; zhiliang.zhang@ntnu.no Received 15 January 2007 Abtract. The purpoe of the work i to tet the uitability of commercially available NiTi alloy for application a eimic protection material. Two different NiTi alloy are characterized mechanically. One of thee alloy i fully autenitic at room temperature, while the other ha an autenite tart temperature above room temperature, but a martenite tart temperature below room temperature. The two alloy how only a mall temperature region with peudoelatic behaviour. odelling wa performed to invetigate whether combining two different material in one damper configuration provide a damper with a broad range of temperature with good damping characteritic. Key word: hape memory alloy, damping, peudoelaticity. 1. INTRODUCTION Although hape memory alloy (SA) have been known for decade, they have not been widely ued in the civil tructure. Due to their high damping capacity, there ha been a recent interet in application of SA to eimic damping [ 1 5 ]. Shape memory alloy are motly known for their ability to revert to their initial hape upon heating. Thi i called the hape memory effect. Another important phenomenon i the o-called peudoelaticity or uperelaticity in which the phae tranformation from autenite to martenite occur merely by increaing the external tre. The alloy undergoe the revere tranformation to the autenite tate automatically by unloading the tre. The tre train curve for the peudoelaticity how a ditinctive plateau and a hyterei. Thi peudo- 197

2 elatic behaviour exhibit good damping capacity becaue of the neceary energy for the phae tranformation. The objective of the work i to characterize two commercially available NiTi alloy and invetigate their uitability for application a eimic protection material. 2. EXPERIENTAL 2.1. aterial Two different NiTi alloy deignated and AF30 were purchaed from Grikin (China). The wire had a diameter of 2 mm. The chemical analye of the two alloy are lited in Table 1. The tranformation temperature (A = autenite tart, A f = autenite finih, = martenite tart, and A f = martenite finih) of material are lited in Table 2. The tranformation temperature of the alloy are expected to be lower than the tranformation temperature of the AF30 alloy, ince the preence of a higher Ni content generally decreae the tranformation temperature [ 6 ]. ore detail about the material are available in [ 7 ] odelling The mechanical behaviour of NiTi material wa modelled uing Brinon [ 8 ] model and programmed uing ATLAB. Detail of the modelling work are reported in Olen [ 9 ]. The material parameter neceary for the Brinon model are calculated from tre train curve at variou temperature. Thee are a follow: elaticity modulu for the autenitic phae ( D A), elaticity modulu for the tre-induced martenite phae ( D ), ' critical tre for tranformation tart at T < ( σ S ), ' critical tre for tranformation ending at T < ( σ ), f Table 1. Chemical compoition of the two NiTi alloy, % Ni Ti C AF Table 2. Phae tranformation temperature of NiTi material, C. A = autenite tart, A f = autenite finih, = martenite tart, A f = martenite finih A A f f AF

3 lope of the critical tranformation tre temperature curve for forward tranformation ( C ), lope of the critical tranformation tre temperature curve for revere tranformation ( C A), imum reidual train ( ε L ) echanical characterization Tenile tet were performed uing a Dartec 1000RK ervo hydraulic tenile teting machine connected to an Intron 8800 Digital Controller. A heat chamber with a temperature range between 150 C and 250 C wa ued to control the pecimen temperature. The diplacement wa regitered uing an extenometer. The temperature of the pecimen urface wa meaured uing a thermocouple. The length of the wire pecimen wa 200 mm. 3. RESULTS AND DISCUSSION The material i a NiTi alloy with an A f temperature of 4 C (ee Table 2). The tre train curve for the material are hown in Fig. 1. The teted material exhibit a wide hyterei and a mall temperature range for peudoelaticity. A more elaborate dicuion and reult of fatigue teting of thi material are reported in [ 7 ]. Although the material ha obviouly it limitation when ued a a eimic damping material, it i ued to provide the parameter neceary for the modelling. At temperature below the the critical tre, ' σ S, i nearly contant, a hown in Fig. 1a c. From Fig. 1b it can be found ' that σ ' S = 72.7 Pa and σ f = Pa. The only tre train curve with ditinct linear deformation of tre-induced martenite i found at 20 C, thu the elaticity modulu for tre-induced martenite, D, i obtained from Fig. 1d. From the ame figure the imum reidual tre, ε L, i obtained. At T = 10 C the material i completely in the autenitic phae and the elaticity modulu for autenite, D, i meaured from A Fig. 1h. When T >, the critical tranformation tre, σ, increae with temperature. A imilar behaviour can be oberved for σ A when T A. Figure 2 how the critical tree veru temperature. A linear regreion wa ued to determine the parameter C and C A. The repective value are 8.0 Pa/ C and 7.3 Pa/ C. The AF30 material i a NiTi alloy with an autenite finih temperature, A f, of 41 C (ee Table 2). Figure 3 how the tre train curve for thi material. ' At temperature T the critical tre, σ, i nearly contant a hown ' in Fig. 3a c. The value of the critical tree, σ ' and σ f, can be obtained from thee figure. The elaticity modulu for the tre-induced martenite, D, and imum reidual train, ε L, are obtained from the curve at T = 53 C (Fig. 3c). The elaticity modulu for autenite, D A, i meaured 199

4 Fig. 1. Tenile teting reult of the material at variou temperature. Fig. 2. Critical tranformation tree for forward and revere tranformation a a function of temperature for the material. 200

5 Fig. 3. Tenile teting reult of the AF30 material at variou temperature. at T = 46 C (Fig. 3g), when the material i completely in the autenitic phae. A Similar to the material, the critical tranformation tre, σ, increae with temperature when T >. The ame i valid for σ A when T A. Figure 4 how thee critical tree plotted againt temperature. The lope of the linear regreion line are ued to determine the C and C A. The critical tre value at 53 C can be included in the interpolation, ince it i taken at the of AF30 [ 8 ]. The material how ome degree of uperelaticity at temperature above A, making it poible to obtain material data needed to perform paive damper imulation baed on Brinon model. In Table 3 an overview of the material data i given. 201

6 Fig. 4. Critical tranformation tree for forward and revere tranformation a a function of temperature for the AF30 material. Table 3. Parameter meaured from the tre train curve for the Brinon model. For explanation of ymbol ee ection 2.2. aterial D, Pa D A, Pa C, Pa/ C C A, Pa/ C σ ', Pa ' f σ Pa AF , ε L 4. DAPER DESIGN The objective of the imulation i to predict the behaviour of eimic damper with elected compoite wire. The damper are compoed of the and AF30 material. Each wire ha a length of 200 mm and a radiu of 1 mm. Spring, dahpot, and pring dahpot combination are ued to repreent uperelaticity (SE), the hape memory effect (SE), and the SE SE combination, repectively. The SE i ued to decribe the apparent platic deformation in the wire. Each damper ytem conit of three parallel coupled wire. A deformation controlled load-cycle i employed in the imulation a hown chematically in Fig. 5. Four damper ytem were tudied. Baed on the temperature-dependent behaviour of the wire, i.e. SE and SE, three working temperature were conidered. Since the temperature in the imulation i never below, the wire are all aumed to be 100% autenitic. At temperature below the A f of both and AF30, the wire experience SE and partial SE; when the temperature i above the A of but below the A of AF30, both SE and f f 202

7 Fig. 5. Deformation controlled load cycle exerted on a eimic damper during imulation. SE are preent; when the temperature i above the A f of both and AF30, all wire exhibit SE. Table 4 chematically how the four damper ytem. Three deformation level were conidered for each damper. The deformation length, d, for each cycle wa choen according to the martenite fraction of the wire. The martenite control value for imulation are ξ = 0.5, ξ = 0.75, and ξ = 1. They repreent the martenite fraction value reached before unloading. artenite fraction in the AF30 wire differ from the control value due to a horter tranformation length ε L. Table 4. Sytem and working temperature conidered in the tudy 3 x 3 x AF30 2 x 1 x 1 x AF30 2 x AF30 203

8 The primary tak of a eimic damper i to diipate energy during eimic activity. The energy diipation capacitie of the four damper conidered in thi tudy are compared in Fig 6 and 7. Figure 6 how the diipated energy veru temperature, while Fig. 7 how the diipated energy veru ξ and d. Figure 6 indicate that the damper containing homogeneou wire material experience imum diipation when the temperature lie between A and A f. Within thi temperature range, however, reidual diplacement will be preent, reducing the re-centring capabilitie of the damper. It i therefore deirable to ue material that experience uperelaticity when ubjected to load in the damper working temperature. It hould be noted that if the temperature i much higher than f, undeired effect. A the level of diipated energy decreae noticeably, which i an Fig. 6. Comparion of the diipated energy veru temperature curve. Fig. 7. Diipated energy veru ξ ξ for all damper configuration. 204

9 Figure 6 how that a damper containing only the AF30 material exhibit the highet diipation capacity. But ince A f = 41 C for thi material, re-centring will not occur at room temperature. By adding wire of material, recentring will occur at all temperature above 4 C, which i the A f for the material. The temperature dependence of the damper i lowet when one AF30 wire i combined with two wire. Figure 7 how how the diipated energy varie with ξ and d. The energy level reache it imum in the range 0.8 < ξ < 0.9, which indicate that it i not optimal to let the wire be deformed until complete martenite tranformation ha occurred. 5. CONCLUSIONS In thi work, two commercial NiTi alloy were characterized and their mechanical behaviour in variou damper configuration wa modelled. The two alloy how only a mall temperature region with peudoelatic behaviour. The damping capacity of the material i at it imum jut below A f. Combination of different material in the ame damper configuration reult in a broader temperature range with good damping characteritic. REFERENCES 1. Saadat, S., Salich, J., Noori,., Hou, Z., Davoodi, H., Bar-on, I., Suzuki, Y. and auda, A. An overview of vibration and eimic application of NiTi hape memory alloy. Smart at. Struct., 2002, 11, van der Eijk, C., Zhang, Z. L. and Akelen, O.. Seimic damper baed on hape memory alloy: metallurgical background and modeling. In Proceeding of Third European Conference on Structural Control, 3ECSC, Vienna, Autria, July 2004 (Flech, R. et al., ed). Vienna Univerity of Technology, 2005, Song, G., a, N. and Li, H.-N. Application of hape memory alloy in civil tructure. Eng. Struct., 2006, 28, Janke, L., Czaderki, C., otavalli,. and Ruth, J. Application of hape memory alloy in civil engineering tructure overview, limit and new idea. at. Struct., 2005, 38, Dolce,. and Cardone, D. echanical behaviour of hape memory alloy for eimic application; 2. Autenite NiTi wire ubjected to tenion. Int. J. ech. Sci., 2001, 43, Otuka, K. and Ren, X. Phyical metallurgy of Ti-Ni-baed hape memory alloy. Progre at. Sci., 2005, 50, van der Eijk, C., Olen, J. S. and Zhang, Z. L. Fitne for purpoe evaluation of two NiTi alloy for eimic damping. In Proceeding of Fourth World Conference on Structural Control and onitoring (4WCSC), July 2006, San Diego, California, U.S.A. (to appear). 8. Brinon, L. C. One-dimenional contitutive behaviour of hape memory alloy: thermomechanical derivation with non-contant material function and redefined martenite internal variable. J. Intell. at. Sytem Struc., 1993, 4, Olen, J. S. Seimic Damper with Compoite NiTi-Wire A New Damper Sytem..Sc. thei, Norwegian Univerity of Science and Technology (NTNU), Trondheim, Norway

10 Kahe töötuliku NiTi ulami peudoelate käitumie uurimine: kated ja modelleerimine Caper van der Eijk, Jim Stian Olen ja Zhiliang Z. L. Zhang On katetatud töötulikke NiTi ulameid eimilie kaitematerjalina. On määratud kahe erineva NiTi ulami mehaanilied omadued. Ük neit ulamitet on toatemperatuuril täielikult auteniitne, amal ajal kui teie auteniitne faa algab toatemperatuurit kõrgemal temperatuuril, aga marteniite faai algutemperatuur jääb toatemperatuurit allapoole. Neid kaht ulamit ieloomutab peudoelatne käitumine kita temperatuurivahemiku. odelleerimiel on uuritud, ka kahe erineva materjali kautamine ühe amortiaatori võimaldab luua amortiaatorit laia temperatuurivahemiku jaok ja tagada eejuure head amortieerivad omadued. 206