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Lu, Xionggang; Cai, Wei; Zhao, Liancheng

doi:10.1023/a:1025445832316

Cited by 13 publications

(3 citation statements)

References 10 publications

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“…However, NiTi alloys show a relatively narrow temperature hysteresis and, thus, they are hard to store in ambient temperature when A s is relatively low, or they possibly lose residual stress when M s is relatively high. NiTiNb alloys, in which Nb is niobium, were introduced and studied to overcome this problem [18][19][20][21]. The hysteresis of NiTiNb alloys is larger than that of NiTi alloys when measured without applying any external stress.…”

Section: Introductionmentioning

confidence: 99%

Recovery and residual stress of SMA wires and applications for concrete structures

Choi

Cho

et al. 2010

Smart Mater. Struct.

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In general, NiTi shape memory alloys are used for applications in civil structures. NiTi SMAs show good superelasticity and shape memory effect properties. However, for application of the shape memory effect, it is desirable for SMAs to show a wide temperature hysteresis, especially for civil structures which are exposed to severe environmental conditions. NiTiNb SMAs, in general, show a wider temperature hysteresis than NiTi SMAs and are more applicable for civil structures. This study examines the temperature hysteresis of NiTiNb and NiTi SMAs, and their recovery and residual stress are investigated. In addition, the tensile behaviors of SMA wires under residual stress are evaluated. This study explains the possible applications for concrete structures with the shape memory effect and illustrates two experimental results of concrete cylinders and reinforced concrete columns. For both tests, SMA wires of NiTiNb and NiTi are used to confine concrete using residual stress. The SMA wire jackets on the concrete cylinders increase the peak strength and the ductility compared to the plain concrete cylinders. In addition, the SMA wire jackets on reinforced concrete columns increase the ductility greatly without flexural strength degradation.

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Section: Introductionmentioning

confidence: 99%

Recovery and residual stress of SMA wires and applications for concrete structures

Choi

Cho

et al. 2010

Smart Mater. Struct.

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“…The large damping capacity of the EA sample is due to heat treatment who is efficient to liberate blocking regions and dislocations. According to the literature, Ni-Ti-based alloys have a high damping capacity during phase transformation and in the martensitic phase, whereas their austenitic phase shows a much lower energy dissipation [31]. The high damping capacity of the martensite phase is related to the hysteretic movement of interfaces (martensite variant interface and twin boundaries) [32,33].…”

Section: Dma Analysismentioning

confidence: 99%

Behaviors of Thermoelastic Properties in Ni-Ti Based Shape Memory Alloys, Processed by Metal Forming Techniques

Tenório Luna da Silva,

Virgolino,

Silva

et al. 2023

IIUMEJ

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In this work, the thermoelastic properties of Ni-Ti shape memory alloys (SMA) processed by conventional rolling and equal channel angular extrusion (ECAE) were investigated. SMAs have two phases: Austenite (at high temperature) and Martensite (at low temperature). The samples were compared under five different thermal and processing conditions: homogenized, rolled, rolled-annealed, extruded, and extruded-annealed. The homogenized sample served as a reference. The samples were analyzed by differential scanning calorimetry (DSC) to determine the thermoelastic transformation temperatures. Images were taken using scanning electronic microscopy (SEM) in conjunction with energy dispersive spectroscopy (EDS). The dynamic area was completed for two tests: under constant load bending (simulation of the memory effect to determine the reversible thermoelastic strain) and dynamic mechanical analysis (DMA). The results showed that the plastic forming processes alter the properties, especially for samples exposed to the ECAE, which can block the martensitic phase. However, R-phase (a rhombohedral phase), that can appear at low temperatures before the martensitic phase, emerges totally when the extruded sample suffers annealing. The images of SEM, confirmed by EDS, show that any type of forming process and the presence of precipitates have a significant influence on the behavior of the elastic property. It was found that extrusion has a greater effect on the restoring properties of the alloys than rolling. This analysis is of great importance for the use of SMA in applications requiring high mechanical strength combined with the functional properties of shape recovery through martensitic phase transformations. ABSTRAK: Kajian ini adalah berkaitan sifat-sifat bentuk aloi ingatan (SMA) termoelastik Ni-Ti yang diproses melalui penggelek konvensional dan penyemperitan sudut saluran sama (ECAE). SMA mempunyai dua peringkat: Austenit (pada suhu tinggi) dan Martensit (pada suhu rendah). Sampel dibandingkan pada lima tahap kepanasan dan proses iaitu: percampuran, penggulungan, penggulungan-rataan, perataan dan penyemperitan-rataan. Sampel campuran yang dihomogenkan dijadikan sebagai sampel rujukan. Sampel dianalisis dengan pengimbas kalorimetri pembezaan (DSC) bagi menentukan suhu transformasi termoelastik. Imej diambil menggunakan pengimbas mikroskop elektronik (SEM) bersama spektroskopi penyebaran tenaga (EDS). Kawasan dinamik diuji dengan dua ujian: di bawah lenturan beban malar (simulasi kesan memori bagi menentukan terikan termoelastik boleh balik) dan analisis mekanik dinamik (DMA). Dapatan kajian menunjukkan bahawa proses pembentukan plastik telah mengubah sifat, terutama pada sampel yang terdedah kepada penyemperitan sudut saluran sama ECAE, yang boleh menyekat fasa martensit. Walau bagaimanapun, fasa-R (fasa rombohedral) yang boleh muncul pada suhu rendah sebelum fasa martensitik, muncul sepenuhnya apabila sampel tersemperit mengalami penyepuhlindapan (penyemperitan-rataan). Imej pengimbasan mikroskop elektron, seperti yang dibuktikan dengan spektroskopi penyebaran tenaga (EDS), menunjukkan bahawa apa-apa jenis proses pembentukan dan kehadiran mendakan mempunyai pengaruh kuat terhadap sifat elastik. Dapatan kajian juga mendapati bahawa penyemperitan mempunyai kesan yang lebih besar terhadap sifat pemulihan aloi berbanding proses penggulungan. Analisis ini sangat penting bagi penggunaan bentuk aloi ingatan (SMA) dalam aplikasi yang memerlukan kekuatan mekanikal yang tinggi bersama sifat pemulihan bentuk melalui transformasi fasa martensit.

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“…However, NiTi alloys show relatively narrow temperature hysteresis and, thus, they are hard to be stored in ambient temperature when A s is relatively low or they remain relatively small recovery stress when M s is relatively high. NiTiNb alloys were introduced and studied to overcome this problem [3][4][5][6]. NiTiNb alloys show relatively wide temperature hysteresis and, thus, they can be stored safely and leave relatively large recovery stress at ambient temperature.…”

Section: Introductionmentioning

confidence: 99%

Seismic retrofit for RC columns by NiTi and NiTiNb SMA wires

Choi

Yang²,

Tae³

et al. 2009

ESOMAT 2009 - 8th European Symposium on Martensitic Transformations

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Abstract. This paper conducted several flexural tests of RC (reinforced concrete) columns retrofitted by SMA (shape memory alloy) wires. The RC columns with lap spliced reinforcements at the base show less ductile behaviour than those with continuous reinforcements. SMA wire jackets can increase the ductility of the RC columns with lap spliced reinforcements and thus this study used the two kinds of SMA wires to retrofit such RC columns; the first one is NiTi SMA wire that remains in martensite at room temperature and the other is NiTiNb SMA wire that is austenite at room temperature. Both the SMA wires show shape memory effect and provide active confinement for concrete. The SMA wires were prestrained to 7% strain and released. At the state, some residual strain remained and can be recovered by heating. The prestrained SMA wires were wrapped around the plastic hinge region of the RC columns and then the temperature of the wires raised by heating. Then, the SMA wires induced an active confinement on the RC columns. Each wire was measured for recovery and residual stress to obtain the information of active confinement. This active confinement and the resistance of the SMA wires increased the ductile behaviour of the RC columns in lateral direction. The parameters in this study are the kinds of SMA and the pitch of the wires. All types of the specimens retrofitted the SMA wires showed good ductile behaviour without degrading the flexural strength.

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Cited by 13 publications

References 10 publications

Recovery and residual stress of SMA wires and applications for concrete structures

Recovery and residual stress of SMA wires and applications for concrete structures

Behaviors of Thermoelastic Properties in Ni-Ti Based Shape Memory Alloys, Processed by Metal Forming Techniques

Seismic retrofit for RC columns by NiTi and NiTiNb SMA wires

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