Superelastic cellular NiTi tube-based materials: Fabrication, experiments and modeling

Abstract

The authors wish to acknowledge the financial support of the French ANR research program ANiM: Architectured NiTi Material (N.2010 BLAN 90201)International audienceThe aim of this paper is to present an experimental and modeling study as the first step towards designing and optimizing architectured materials constituted of NiTi tubes. The idea is to combine the intrinsic and novel properties of nickel–titanium shape memory alloys with purposely engineered topologies. By joining thin-wall superelastic tubes via electrical resistance welding, we create regular cellular material demonstrators. The superelastic behavior of two simple architectured materials based on identical tubes, but with two topologies, are experimentally characterized and modeled using finite element approaches. The predicted behaviors are compared by simulating complex loading, exploring the influence of the constitutive material behavior on the effective mechanical properties of cellular materials. The parameters of the constitutive equations are identified on tensile tests performed on small dog-bone shaped specimens, machined from the tubes by spark cutting. The modeling results are finally compared with compression tests performed on these simple architectured NiTi materials. As a further validation of the proposed study, two large cell structures (square and hexagonal stacking) were modeled to gain greater insight into the role of different architectures

The Elastocaloric Effect: A Way to Cool Efficiently

“…Different geometries (wires, tubes, and foams) [32][33][34] would in general be possible with different loading techniques (tension, compression, bending, and twisting), but a special focus should be put on assuring a homogenous strain and therefore eCE over the entire regenerator (as in the case of wire or plate under tension as applied in this work) which is crucial for an effi cient cooling device. Different geometries (wires, tubes, and foams) [32][33][34] would in general be possible with different loading techniques (tension, compression, bending, and twisting), but a special focus should be put on assuring a homogenous strain and therefore eCE over the entire regenerator (as in the case of wire or plate under tension as applied in this work) which is crucial for an effi cient cooling device.…”

“…Especially applying smaller strains can increase the fatigue life, but also reduces the elastocaloric effect and the cooling power of the device, which will have to be evaluated in the future. Different geometries (wires, tubes, and foams) would in general be possible with different loading techniques (tension, compression, bending, and twisting), but a special focus should be put on assuring a homogenous strain and therefore eCE over the entire regenerator (as in the case of wire or plate under tension as applied in this work) which is crucial for an efficient cooling device. However, as shown in this work the future of the elastocaloric cooling is very promising with a great potential for further development.…”

A Multiscale Analysis on the Superelasticity Behavior of Architected Shape Memory Alloy Materials

“…To investigate the behavior of architected cellular SMAs, rare, but valuable works have been proposed (Machado et al [ 26 ]; Ravari et al [ 27 ]; Ashrafi et al [ 28 ]). Machado et al [ 26 ] proposed an experimental and modeling study on the cellular NiTi tube-based materials.…”

“…To investigate the behavior of architected cellular SMAs, rare, but valuable works have been proposed (Machado et al [ 26 ]; Ravari et al [ 27 ]; Ashrafi et al [ 28 ]). Machado et al [ 26 ] proposed an experimental and modeling study on the cellular NiTi tube-based materials. In order to design and optimize the architected SMA tube materials, the authors studied the effective behavior of the thin-walled NiTi cellular materials by carrying out a study based on experiment and numerical simulation.…”

Tensile and fatigue behavior of superelastic shape memory rods

“…The second effect relates to the materials ability to recover from large elastic strains (up to 8%) as is termed superelasticity effect (SE). The early work on shape memory alloys focused on getting a fundamental understanding of the thermodynamics and mechanism of the phase transformations involved [3] in the SME and SE effects [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. A number of researchers have investigated the feasibility of incorporating superelastic shape memory alloys into smart structures for seismic resistance or damage tolerant structures [19][20][21][22][23].…”