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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

Hysteretic behavior of NiTiNb and NiTi SMA wires under prestress.
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Figure 5: Hysteretic behavior of NiTiNb and NiTi SMA wires under prestress.

Mentions: The NiTiNb SMA wires were prestrained up to 3%, 5%, or 7% and had constrained deformation. The wires were then heated to 200°C and cooled to room temperature. This process produced recovery and residual stresses as shown in Figure 5. After that, the wires were elongated cyclically with increasing strains; the maximum stress was larger than the plateau stress developed during the monotonic loading. The maximum developed stress due to reloading was larger than the plateau stress: for a 7% prestrain, the maximum developed stress was approximately 325 MPa, which was larger by 28.5% than the plateau stress of 253 MPa. Therefore, the procedure can provide more confining pressures or prestresses than in the case of the residual stress in Figure 2.


Behavior of NiTiNb SMA wires under recovery stress or prestressing.

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

Hysteretic behavior of NiTiNb and NiTi SMA wires under prestress.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Hysteretic behavior of NiTiNb and NiTi SMA wires under prestress.
Mentions: The NiTiNb SMA wires were prestrained up to 3%, 5%, or 7% and had constrained deformation. The wires were then heated to 200°C and cooled to room temperature. This process produced recovery and residual stresses as shown in Figure 5. After that, the wires were elongated cyclically with increasing strains; the maximum stress was larger than the plateau stress developed during the monotonic loading. The maximum developed stress due to reloading was larger than the plateau stress: for a 7% prestrain, the maximum developed stress was approximately 325 MPa, which was larger by 28.5% than the plateau stress of 253 MPa. Therefore, the procedure can provide more confining pressures or prestresses than in the case of the residual stress in Figure 2.

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