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Dijital Arşivi

Experimental analysis and modeling of porous NiTi shape memory alloys

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dc.contributor Ph.D. Program in Mechanical Engineering.
dc.contributor.advisor Anlaş, Günay.
dc.contributor.advisor Moumni, Ziad.
dc.contributor.author Özerim, Gülcan.
dc.date.accessioned 2024-03-12T14:58:07Z
dc.date.available 2024-03-12T14:58:07Z
dc.date.issued 2022
dc.identifier.other ME 2022 O84 PhD
dc.identifier.uri http://digitalarchive.boun.edu.tr/handle/123456789/21474
dc.description.abstract Porosity brings new features to NiTi SMAs, and raises its potential for biomedical applications. Although different techniques are provided in the literature for manufacturing porous NiTi samples, the subject is still open to further investigation to achieve superior shape memory characteristics. Based on this, the aim of the thesis is to analyze and model the mechanical behavior of porous NiTi SMAs. First, NiTi compacts were produced using spark plasma sintering. After sintering, because the samples did not show the expected pseudoelastic behavior, they were systematically subjected to heat treatment. The transformation behavior and the phase composition were analyzed using DSC and XRD. These characterization gave an insight to the micro-structure after heat treatment. Then, instrumented micro-indentation was carried out to measure the hardness that was altered by aging. Selected samples that were tested under uniaxial compression showed an enhancement in the pseudoelasticity of the SPSed NiTi that was heat-treated. In the modeling part, a macro-scale phenomenological model is proposed for the mechanical behavior of the porous NiTi by using poromechanics. The model considers the porous medium as a skeleton that consists of a solid matrix and connected porous space. The porosity is included as an internal state variable. Both the pseudoelastic and plastic deformations were considered. The phenomenological model was implemented into Abaqus through a UMAT, and validated using experimental results available in the literature, as well as the numerical results obtained from the unit cell (UC) technique used in this study. The model proposed in this thesis represents the mechanical behavior of porous SMAs with reasonable accuracy with a significant reduction in numerical cost when compared to the UC approach. The model can be especially useful in possible biomedical applications.
dc.format.extent 111:001:PDF:b2795476:038323:0:0:0:0:0:0tFull text electronic versionvn
dc.publisher Thesis (Ph.D.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022.
dc.subject.lcsh Nickel-titanium alloys.
dc.subject.lcsh Shape memory alloys.
dc.title Experimental analysis and modeling of porous NiTi shape memory alloys
dc.format.pages xvii, 121 leaves


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