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

Choi, Eunsoo; Cho, Sung-Chul; Hu, Jong Wan; Park, Taehyo; Chung, Yoo Seung

doi:10.1088/0964-1726/19/9/094013

Cited by 48 publications

(34 citation statements)

References 26 publications

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“…The shape memory effect of NiTiNb SMAs has been utilized to actively confine concrete elements [18][19][20][21][22][23][24][25]. NiTiNb SMA spirals were wrapped around concrete cylinders and columns, then heated to activate the shape memory effect.…”

Section: Introductionmentioning

confidence: 99%

Bond behavior of NiTiNb SMA wires embedded in CFRP composites

El-Tahan¹,

Dawood

2017

Polymer Composites

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This article summarizes the details of an experimental and analytical program that was conducted to study the bond behavior between nickel‐titanium‐niobium shape memory alloy wires and fiber reinforced polymer composites. Understanding this bond behavior will facilitate the design of composite systems that are fabricated using both materials and which would exhibit unique properties that cannot be achieved using either material separately. A total of nine pull‐out specimens were fabricated and tested. A digital image correlation (DIC) noncontact measurement system was used to identify the onset and propagation of the debonding. The experimental results indicated that the interfacial bond transfer consists of two components: cohesion (before the onset of debonding) and friction (after the onset of debonding). A 3‐D nonlinear finite element analysis (FEA) was conducted to investigate the debonding mechanism of the pull‐out specimens. A trilinear cohesive zone model was used to model the interface taking into account the cohesive and friction components of the stress transfer at the interface. The debonding mechanism predicted by the FEA matches the experimental observations that were obtained using conventional instruments and the DIC system, well. POLYM. COMPOS., 39:3780–3791, 2018. © 2017 Society of Plastics Engineers

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Section: Introductionmentioning

confidence: 99%

Bond behavior of NiTiNb SMA wires embedded in CFRP composites

El-Tahan¹,

Dawood

2017

Polymer Composites

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“…The developed or remaining recovery stress depends on the temperature of the wire and becomes zero when the temperature decreases to M s , where the martensite starts. Furthermore, the recovery and residual stresses depend on the alloy types, such as NiTi or NiTiNb, and the temperature window of the SMA alloys [2,3]. The recovery stress can be used to provide external confinement for reinforced concrete columns [3] or prestress in reinforced concrete beams [4].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the recovery and residual stresses depend on the alloy types, such as NiTi or NiTiNb, and the temperature window of the SMA alloys [2,3]. The recovery stress can be used to provide external confinement for reinforced concrete columns [3] or prestress in reinforced concrete beams [4]. Several previous studies showed that SMA wires were very effective in providing external confinement for concrete [5,6].…”

Section: Introductionmentioning

confidence: 99%

Behavior of NiTiNb SMA wires under recovery stress or prestressing

et al. 2012

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The recovery stress of martensitic shape-memory alloy [SMA] wires can be used to confine concrete, and the confining effectiveness of the SMA wires was previously proved through experimental tests. However, the behavior of SMA wires under recovery stress has not been seriously investigated. Thus, this study conducted a series of tests of NiTiNb martensitic SMA wires under recovery stress with varying degrees of prestrain on the wires and compared the behavior under recovery stress with that under prestressing of the wires. The remaining stress was reduced by the procedure of additional strain loading and unloading. More additional strains reduced more remaining stresses. When the SMA wires were heated up to the transformation temperature under prestress, the stress on the wires increased due to the state transformation. Furthermore, the stress decreased with a decreasing temperature of the wires down to room temperature. The stress of the NiTiNb wires was higher than the prestress, and the developed stress seemed to depend on the composition of the SMAs. When an additional strain was subsequently loaded and unloaded on the prestressed SMA wires, the remaining stress decreased. Finally, the remaining stress becomes zero when loading and unloading a specific large strain.

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“…As illustrated in Figure 6, the cold-drawn NiTi SMAs show stress-relaxation with decreasing temperature after inducing recovery stress with high temperature (Choi et al, 2010b). For crack-repairing, the high recovery stress would work to close a crack, and, then, after the repairing, the stress would decrease.…”

Section: Discussion and Applicationsmentioning

confidence: 99%

“…Pre-elongated martensitic SMAs with deformation-restraint induce recovery stress by heating up above transformation temperature but lose some level of stress by cooling (see Figure 1(b)); the remaining stress can be used for post-tensioning or prestressing forces. The recover and residual stress highly depends on the alloy composition, manufacturing process, and strain of pre-elongation (Shin & Andrawes, 2010;Choi et al, 2010b;Saleeb et al, 2015a;Saleeb et al, 2015b).…”

Section: Sma Fibers Without End-hooksmentioning

confidence: 99%

New SMA Short Fibers for Cement Composites Manufactured by Cold Drawing

Choi¹,

Kim²,

Jeon³

et al. 2016

JMSR

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This study suggests new shape memory alloy reinforcing fibers manufactured by cold drawing method. This study prepares NiTi shape memory alloy (SMA) wires with diameter of 1.0 mm. Then, the wires are elongated by cold drawing and, thus, the diameters are reduced to 0.93 or 0.965 mm, respectively. This procedure introduces prestrain into the wires. When elongated SMA wires are heated, the shape memory effect is activated; this process recovers the deformed length as well as the reduced diameter due to Poisson's effect. Cold drawn wires with diameters of 0.93 and 0.965 mm recover diameters of 0.018 and 0.024 mm, respectively, with heating. The bulging of the SMA fiber in the radial direction inside cement composites induces confining pressure around the fiber and increases bond strength. When an SMA fiber is heated at the both ends, the heated parts bulge and the fiber shape looks like a dog-bone. Such a dog-bone shaped fiber can provide a geometrical anchoring action that also increases the bond resistance of the fiber. This study conducts pullout tests of SMA fibers to understand their pullout behavior and assess bond stress. The heated fibers and dog-bone shaped fibers increase pullout force compared to those of as-received and cold-drawn fibers. When dog-bone shaped fibers are heated, they show twice the pullout force of dog-bone shaped fibers without heating because geometric anchoring action as well as additional frictional resistance due to confining pressure are activated.

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

Cited by 48 publications

References 26 publications

Bond behavior of NiTiNb SMA wires embedded in CFRP composites

Bond behavior of NiTiNb SMA wires embedded in CFRP composites

Behavior of NiTiNb SMA wires under recovery stress or prestressing

New SMA Short Fibers for Cement Composites Manufactured by Cold Drawing

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