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Behavior of NiTiNb SMA wires under recovery stress or prestressing.

Choi E, Nam TH, Chung YS, Kim YW, Lee SY - Nanoscale Res Lett (2012)

Bottom Line: 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.More additional strains reduced more remaining stresses.Furthermore, the stress decreased with a decreasing temperature of the wires down to room temperature.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Civil Engineering, Hongik University, Seoul, 121-791, South Korea. eunsoochoi@hongik.ac.kr.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Cyclic curves of NiTiNb SMA wires under residual stress.
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Figure 2: Cyclic curves of NiTiNb SMA wires under residual stress.

Mentions: The loading for prestrain and unloading curve and the subsequent hysteretic curves in the NiTiNb SMA wires are shown in Figure 2. The reloading slopes from the initial residual stress appeared to be equal to the slopes of the unloading stiffness from the prestrains. The reloading curves crossed the plateau-stress line, and the maximum stress of the reloading seemed to be equal to the plateau stress: Figure 2e shows this almost perfectly. The residual stress decreased with an increasing reloading strain when the wire was unloaded. When the reloading strain reached the prestrain, the residual stress became zero with subsequent unloading. The reloading beyond the prestrain and the subsequent unloading remained a residual strain.


Behavior of NiTiNb SMA wires under recovery stress or prestressing.

Choi E, Nam TH, Chung YS, Kim YW, Lee SY - Nanoscale Res Lett (2012)

Cyclic curves of NiTiNb SMA wires under residual stress.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3278361&req=5

Figure 2: Cyclic curves of NiTiNb SMA wires under residual stress.
Mentions: The loading for prestrain and unloading curve and the subsequent hysteretic curves in the NiTiNb SMA wires are shown in Figure 2. The reloading slopes from the initial residual stress appeared to be equal to the slopes of the unloading stiffness from the prestrains. The reloading curves crossed the plateau-stress line, and the maximum stress of the reloading seemed to be equal to the plateau stress: Figure 2e shows this almost perfectly. The residual stress decreased with an increasing reloading strain when the wire was unloaded. When the reloading strain reached the prestrain, the residual stress became zero with subsequent unloading. The reloading beyond the prestrain and the subsequent unloading remained a residual strain.

Bottom Line: 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.More additional strains reduced more remaining stresses.Furthermore, the stress decreased with a decreasing temperature of the wires down to room temperature.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Civil Engineering, Hongik University, Seoul, 121-791, South Korea. eunsoochoi@hongik.ac.kr.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus