Plastic and transformation interactions of pores in shape memory alloy plates

Zhu, Pingping; Stebner, Aaron P.; Brinson, L. Catherine

doi:10.1088/0964-1726/23/10/104008

Cited by 13 publications

(10 citation statements)

References 26 publications

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“…The geometry of these unit cells defines the stiffness of the assembly. Some studies are performed on the importance of porosity morphology, the size, and number and distribution of pores (Van Bael et al, 2012;Zhu et al, 2014). As one of the many possible configurations, Figure 1(a) shows a unit cell that consists of three orthogonal struts that intersect at the mid-point and Figure 1(b) shows the portion of the unit cell that is utilized for the FE analysis.…”

Section: Modelingmentioning

confidence: 99%

Achieving biocompatible stiffness in NiTi through additive manufacturing

Andani

Haberland

Walker

et al. 2016

Journal of Intelligent Material Systems and Structures

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This article seeks to reduce the stiffness of NiTi parts from a nonporous state to that of human bone by introducing porosity. Compact bone stiffness is between 12 and 20 GPa while the currently used bone implant materials are several times stiffer. While very stiff implants and/or fixation hardware can temporarily immobilize healing bone, it also causes stress shielding of the surrounding bone and commonly results in stress concentrations at the implant or immobilization hardware’s fixation site(s). Together these processes can lead to implant or fixation hardware and/or the surrounding bone’s failure. Porous NiTi can be used to reduce the stiffness of metallic implants while also providing necessary stabilization or immobilization of the patient’s reconstructed anatomy. In this work, mechanical behavior of porous NiTi with different levels of porosity is simulated to show the relation between the stiffness and porosity level. Then porous structures are fabricated through additive manufacturing to validate the simulation results. The results indicate that stiffness can be reduced from the bulk value of 69 GPa to as low as 20.5 GPa for 58% porosity. The simulation shows that it is possible to achieve a wide range of desired stiffness by adjusting the level of porosity.

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Section: Modelingmentioning

confidence: 99%

Achieving biocompatible stiffness in NiTi through additive manufacturing

Andani

Haberland

Walker

et al. 2016

Journal of Intelligent Material Systems and Structures

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show abstract

“…According to Figure 5, it can be seen that for both cavity distances, the maximum stress decreases as the number of cavities in the sheet increases which is in agreement with. 23 Moreover, the maximum stresses in the two-cavity sheet for 10 and 7.5 mm spacings are 775 and 764 MPa, respectively. Similarly, for three-cavity sheet, maximum stresses are 751 and 654 MPa, respectively.…”

Section: Resultsmentioning

confidence: 96%

Stress concentration in shape memory alloy sheets with circular cavities: Effects of transformation, saturation, and plasticity

Hosseini

Ashrafi

2022

The Journal of Strain Analysis for Engineering Design

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The analysis of stress concentration in geometrically heterogeneous smart structures is of great importance. In this study, by utilizing a recent constitutive model which considered both transformation and plasticity of shape memory alloys (SMAs), the stress concentration factor (SCF) in plates with circular cavities is investigated and the effect of phase transformation, saturation, and plasticity which may occur locally is studied. The results show that the conversion of the austenitic phase to the martensite leads to a reduction in SCF. After saturation of phase transformation at the stress concentration point, the SCF increases until the entire sheet enters the martensite phase. In the example under study, the SCF reaches 5.8 which is greatly higher than the elastic SCF. By entering the plastic region locally, the SCF reduces. Also, the modeling of sheets with more than one cavity has been done. It is concluded that extra hole, as a stress relief method, has a stronger effect on decreasing maximum stress concentration of shape memory alloys (considering transformation and plasticity) compared to purely elastic stress concentration studies.

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“…Also, the effects of hydrostatic pressure, asymmetry of the constitutive response between tension and compression, are included in the model presented in [17]. Numerical modeling of SMAs, based on the phenomenological constitutive relation are reported in the literature [18][19][20][21][22][23]. Other mesoscopic/ microscopic models for porous NiTi include those reported in [24,25], and some of them are developed from phase-field theory [26,27].…”

Section: Introductionmentioning

confidence: 99%

Atomistic simulation of shape memory effect (SME) and superelasticity (SE) in nano-porous NiTi shape memory alloy (SMA)

Gur

Frantziskonis

Muralidharan

2018

Computational Materials Science

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Porosity can play an important role in altering the phase transformation characteristics of NiTi shape memory alloys (SMA), thus changing its shape memory as well as its superelasticity properties. This work, based on atomistic simulations of binary NiTi SMA, documents the effects of porosity at the nanometer length scale on phase fraction evolution kinetics, transformation temperatures, and stress-strain response. Classical molecular dynamics simulations are performed using a well-examined and verified Finnis-Sinclair type embeddedatom method interatomic potential. Simulation results for the nano-porous NiTi with various porosity configurations are compared to non-porous NiTi. The martensite phase fraction and transformation temperatures increase noticeably with increasing porosity, and the stress-strain response shows noticeable variation with porosity. The residual strain and hysteretic energy dissipation capacity increase significantly with increasing porosity.

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Plastic and transformation interactions of pores in shape memory alloy plates

Cited by 13 publications

References 26 publications

Achieving biocompatible stiffness in NiTi through additive manufacturing

Achieving biocompatible stiffness in NiTi through additive manufacturing

Stress concentration in shape memory alloy sheets with circular cavities: Effects of transformation, saturation, and plasticity

Atomistic simulation of shape memory effect (SME) and superelasticity (SE) in nano-porous NiTi shape memory alloy (SMA)

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