Fatigue Properties of Cast TiNi Shape-Memory Alloy Brain Spatula

In order to develop a brain spatula or a brain retractor made of a shape memory alloy (SMA), the bending characteristics of the brain spatula of TiNi SMA made by the precision casting were discussed based on the tensile deformation properties of the existing copper and the TiNi rolled-SMA. The fatigue properties of both materials were also investigated by the plane-bending fatigue test. The results obtained can be summarized as follows. (1) The modulus of elasticity and the yield stress for the cast and rolled SMAs are lower than those for the copper. Therefore, the conventional rolled-SMA spatula and the new cast-SMA spatula can be bent easily compared to the existing copper-brain spatula. (2) With respect to the alternating- and pulsating-plane bending fatigue, the fatigue life of both the copper and the SMAs in the region of low-cycle fatigue is expressed by a power function of the maximum bending strain. The fatigue life of the conventional rolled SMA and the new cast SMA is longer than that of the existing copper. The fatigue life of the new cast and rolled SMAs in the pulsating-plane bending is longer than that in the alternating-plane bending. (3) The fatigue life of the rolled-SMA and the cast SMA for alternating- and pulsating-plane bendings can be expressed by the unified relationship with a power function of the dissipated work.

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Laser Welding of Ti-Ni Shape Memory Alloy Wire and its Fatigue Properties

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.183-187.1309 ◽

2000 ◽

Vol 183-187 ◽

pp. 1309-1314 ◽

Cited By ~ 2

Author(s):

Y.S. Kim ◽

J.D. Kim

Keyword(s):

Shape Memory Alloy ◽

Laser Welding ◽

Shape Memory ◽

Fatigue Properties ◽

Shape Memory Alloy Wire ◽

Alloy Wire

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Fatigue properties of a TiNi shape-memory alloy wire subjected to bending with various strain ratios

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/146442070321700201 ◽

2003 ◽

Vol 217 (2) ◽

pp. 93-99 ◽

Cited By ~ 1

Author(s):

Y Furuichi ◽

H Tobushi ◽

T Ikawa ◽

R Matsui

Keyword(s):

Fatigue Life ◽

Shape Memory Alloy ◽

Shape Memory ◽

Strain Ratio ◽

Fatigue Properties ◽

Test Machine ◽

Shape Memory Alloy Wire ◽

Alloy Wire ◽

Rotating Bending ◽

Alternating Bending

A fatigue-test machine for alternating bending of a wire under strain-controlled conditions was developed. Bending-fatigue tests on a TiNi shape-memory alloy wire were then performed for various strain ratios. The results obtained can be summarized as: (1) the fatigue life curves under alternating bending and pulsating bending, as expressed by the relationship between maximum strain and the number of cycles to failure, systematically follow the order of strain ratio; (2) the larger the strain ratio, the longer the fatigue life; (3) the fatigue life under rotating bending is shorter than that under alternating bending; (4) the increase in temperature during cyclic bending becomes larger in the order: rotating bending, alternating bending, pulsating bending. The fatigue life decreases in proportion to the increase in temperature; and (5) the fatigue limit of strain for alternating bending, pulsating bending and rotating bending is in the region of R-phase transformation.

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Comparison of Bending Fatigue of NiTi and CuAlMn Shape Memory Alloy Bars

Advances in Materials Science and Engineering ◽

10.1155/2020/8024803 ◽

2020 ◽

Vol 2020 ◽

pp. 1-9 ◽

Cited By ~ 3

Author(s):

Haoyu Huang ◽

Yuan-Zhi Zhu ◽

Wen-Shao Chang

Keyword(s):

Fatigue Life ◽

Shape Memory Alloy ◽

Shape Memory ◽

Damping Ratio ◽

Strain Curve ◽

Fatigue Properties ◽

Functional Fatigue ◽

Cyclic Bending ◽

Structural Fatigue ◽

Secant Stiffness

The behaviour under cyclic bending and in particular the fatigue properties of shape memory alloy (SMA) bars are important for civil engineering applications. In this paper, structural and functional fatigue is studied for both NiTi- and copper-based shape memory alloys. The results are presented from cyclic bending tests on 7 mm diameter NiTi and 12 mm diameter CuAlMn SMA bars targeted at 100,000 cycles. During the tests, dynamic loading at 1 Hz, 5 Hz, and 8 Hz was applied for different strain levels (0.5%, 1%, 2%, and 6%). The stress-strain curve, damping ratio, and secant stiffness were analysed for material characterisation, and the evolution of these parameters was studied to assess functional fatigue. The fatigue life is extended dramatically when the strain is below 1%, and the structural fatigue life of CuAlMn is shown to be better than that of NiTi and to depend on the loading rate. However, decay in stiffness can be found in the CuAlMn SMA, which is considered to be caused particularly by its long grain boundary.

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