Pub Date : 2022-05-16DOI: 10.31399/asm.cp.smst2022p0039
J. Weaver, K. Aycock, G. Sena, S. Sivan, T. Woods, Charlie Yongpravat, F. Donaldson, B. Berg, A. Roiko, Anthony Bauer, W. Falk
The use of superelastic Nitinol in implants continues to grow as physicians, scientists, and engineers design more novel medical devices to utilize its unique characteristics. As many of these devices are expected to be long-term implants, it becomes critically important to increase our understanding of Nitinol fatigue mechanisms beyond 107 cycles. In this study, the fatigue behavior of Nitinol wire in rotary bend testing was characterized by experimental methods and computational modeling. Fractures occurred in high strain regions as predicted by computational modeling. Furthermore, fractures beyond 107 or 108 cycles were observed and seem to have been initiated by nonmetallic inclusions.
{"title":"Experimental and Computational Rotary Bend Fatigue to Characterize Very High Cycle Fatigue of Nitinol","authors":"J. Weaver, K. Aycock, G. Sena, S. Sivan, T. Woods, Charlie Yongpravat, F. Donaldson, B. Berg, A. Roiko, Anthony Bauer, W. Falk","doi":"10.31399/asm.cp.smst2022p0039","DOIUrl":"https://doi.org/10.31399/asm.cp.smst2022p0039","url":null,"abstract":"\u0000 The use of superelastic Nitinol in implants continues to grow as physicians, scientists, and engineers design more novel medical devices to utilize its unique characteristics. As many of these devices are expected to be long-term implants, it becomes critically important to increase our understanding of Nitinol fatigue mechanisms beyond 107 cycles. In this study, the fatigue behavior of Nitinol wire in rotary bend testing was characterized by experimental methods and computational modeling. Fractures occurred in high strain regions as predicted by computational modeling. Furthermore, fractures beyond 107 or 108 cycles were observed and seem to have been initiated by nonmetallic inclusions.","PeriodicalId":119283,"journal":{"name":"SMST 2022: Extended Abstracts from the International Conference on Shape Memory and Superelastic Technologies","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125124049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-16DOI: 10.31399/asm.cp.smst2022p0073
G. Baigonakova, E. Marchenko, F. Yasenchuk Yu, M. Kovaleva
TiNi-based alloys belong to the class of materials with shape memory effects and superelasticity, which are currently being actively studied and successfully used in engineering and medicine. In these alloys, their natural ability to undergo large inelastic deformations and return to their original shape by increasing temperature or relieving stress takes place. The key characteristic of these phenomena is thermoelastic martensitic transformations (MT). The problem of biocompatibility of implants is relevant, as the number of operations using implants in various fields of medicine is growing rapidly. Currently, several studies are underway on the deformation behavior of biological tissues and various implant materials. Wires made of TiNi are one of the most important metal biomedical materials used in endovascular surgery, orthodontics, soft tissue plastics in the form of stents, catheters, orthodontic archwires, metal-knitted materials. Textile implants should be singled out from a wide range of structures made of thin TiNi wire, with the help of which complex surgical problems are solved. A variety of mesh structures made of titanium nickelide are characterized by a particular complexity of deformation characteristics, the manifestation of which in the implant-bio-tissue interface is difficult to predict. To create the appropriate mechanical behavior of an implant in the form of mesh structures, it is necessary to study their deformation behavior. Therefore, to describe the functioning of a superelastic implant in the interface with a biological tissue, the aim of this work is to study the deformation behavior of wire samples 40, 60, and 90 µm thick from the TiNi alloy and metal knit made from them by the method of uniaxial tension. TiNi wires exhibit the effect of superelasticity at a relative strain of 4-6%. Under uniaxial tension of knitted mesh made of these wires, the effect of superelasticity was not detected. It has been found that the cyclic tension diagrams of knitted mesh show behavior inherent in hyperelastic materials. The total tensile load is unevenly distributed in the knitwear, in contrast to the uniformly distributed load when testing the wire.
{"title":"Hyperelastic Behavior of Knitted TiNi Mesh under Uniaxial Tension","authors":"G. Baigonakova, E. Marchenko, F. Yasenchuk Yu, M. Kovaleva","doi":"10.31399/asm.cp.smst2022p0073","DOIUrl":"https://doi.org/10.31399/asm.cp.smst2022p0073","url":null,"abstract":"\u0000 TiNi-based alloys belong to the class of materials with shape memory effects and superelasticity, which are currently being actively studied and successfully used in engineering and medicine. In these alloys, their natural ability to undergo large inelastic deformations and return to their original shape by increasing temperature or relieving stress takes place. The key characteristic of these phenomena is thermoelastic martensitic transformations (MT). The problem of biocompatibility of implants is relevant, as the number of operations using implants in various fields of medicine is growing rapidly. Currently, several studies are underway on the deformation behavior of biological tissues and various implant materials. Wires made of TiNi are one of the most important metal biomedical materials used in endovascular surgery, orthodontics, soft tissue plastics in the form of stents, catheters, orthodontic archwires, metal-knitted materials. Textile implants should be singled out from a wide range of structures made of thin TiNi wire, with the help of which complex surgical problems are solved. A variety of mesh structures made of titanium nickelide are characterized by a particular complexity of deformation characteristics, the manifestation of which in the implant-bio-tissue interface is difficult to predict. To create the appropriate mechanical behavior of an implant in the form of mesh structures, it is necessary to study their deformation behavior. Therefore, to describe the functioning of a superelastic implant in the interface with a biological tissue, the aim of this work is to study the deformation behavior of wire samples 40, 60, and 90 µm thick from the TiNi alloy and metal knit made from them by the method of uniaxial tension. TiNi wires exhibit the effect of superelasticity at a relative strain of 4-6%. Under uniaxial tension of knitted mesh made of these wires, the effect of superelasticity was not detected. It has been found that the cyclic tension diagrams of knitted mesh show behavior inherent in hyperelastic materials. The total tensile load is unevenly distributed in the knitwear, in contrast to the uniformly distributed load when testing the wire.","PeriodicalId":119283,"journal":{"name":"SMST 2022: Extended Abstracts from the International Conference on Shape Memory and Superelastic Technologies","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129296343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-16DOI: 10.31399/asm.cp.smst2022p0077
P. Šittner, O. Molnárová, X. Bian, L. Heller, H. Seiner
When deformed in martensite state, NiTi undergoes pseudoplastic deformation taking place via motion of intervariant interfaces (called martensite reorientation or detwinning), followed by plastic deformation of the B19' monoclinic martensite. The state of the art view is that: (i) the martensite reorientation proceeds via detwinning of <011> type-II twin laminates created by the martensitic transformation upon cooling and (ii) the reoriented martensite deforms plastically via dislocation slip. Although this view might be correct for single crystals and large grain size polycrystals, doubts existed whether it applies also for nanocrystalline NiTi which displays (001) compound twinned microstructures after stress free cooling from the austenite. The authors performed systematic experimental investigations of martensitic microstructures (postmortem TEM) and textures (in-situ HEXRD) evolving during tensile tests on nanocrystalline NiTi wires until fracture. The results indicate that the widespread view of the martensite reorientation as "detwinning" is incorrect. Plastic deformation of martensite proceeds via peculiar deformation mechanism involving (20-1) and (100) deformation twinning assisted by [100]/(011) dislocation slip. It enables the nanocrystalline NiTi wire to deform plastically at ~1 GPa engineering stress up to very large plastic strains ~50% and refines the austenitic microstructure down to nanoscale. Upon unloading and heating, reverse martensitic transformation takes place leaving large recoverable as well as unrecovered strains and high density of {114} austenite twins in the microstructure.
{"title":"Tensile Deformation of B19‘ Monoclinic Martensite in Nanocrystalline NiTi Wires","authors":"P. Šittner, O. Molnárová, X. Bian, L. Heller, H. Seiner","doi":"10.31399/asm.cp.smst2022p0077","DOIUrl":"https://doi.org/10.31399/asm.cp.smst2022p0077","url":null,"abstract":"\u0000 When deformed in martensite state, NiTi undergoes pseudoplastic deformation taking place via motion of intervariant interfaces (called martensite reorientation or detwinning), followed by plastic deformation of the B19' monoclinic martensite. The state of the art view is that: (i) the martensite reorientation proceeds via detwinning of <011> type-II twin laminates created by the martensitic transformation upon cooling and (ii) the reoriented martensite deforms plastically via dislocation slip. Although this view might be correct for single crystals and large grain size polycrystals, doubts existed whether it applies also for nanocrystalline NiTi which displays (001) compound twinned microstructures after stress free cooling from the austenite. The authors performed systematic experimental investigations of martensitic microstructures (postmortem TEM) and textures (in-situ HEXRD) evolving during tensile tests on nanocrystalline NiTi wires until fracture. The results indicate that the widespread view of the martensite reorientation as \"detwinning\" is incorrect. Plastic deformation of martensite proceeds via peculiar deformation mechanism involving (20-1) and (100) deformation twinning assisted by [100]/(011) dislocation slip. It enables the nanocrystalline NiTi wire to deform plastically at ~1 GPa engineering stress up to very large plastic strains ~50% and refines the austenitic microstructure down to nanoscale. Upon unloading and heating, reverse martensitic transformation takes place leaving large recoverable as well as unrecovered strains and high density of {114} austenite twins in the microstructure.","PeriodicalId":119283,"journal":{"name":"SMST 2022: Extended Abstracts from the International Conference on Shape Memory and Superelastic Technologies","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131084433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-16DOI: 10.31399/asm.cp.smst2022p0099
A. S. King, D. Lipke, R. D. Dempsey, D. Lipke
Achieving stringent chemistry standards is necessary for additive manufacturing of Nitinol shape memory alloys. This work describes an elevated temperature gas-solid reaction processing technique that can be used to precisely regulate the chemistry and phase transformation behaviors of Nitinol components. The technique, Shape memory alloys via Halide-Activated Pack Equilibration (SHAPE), employs established principles of chemical vapor transport to equilibrate a substrate against reactive pack mixtures designed to regulate the chemical potentials of nickel and titanium in accordance with Gibbs' phase rule as means to precisely control substrate phase and elemental composition. The results suggest that SHAPE may find crosscutting potential especially when paired with additive manufacturing or fusion welding of Nitinol to improve product quality. Notwithstanding future applications, SHAPE is limited by solid-state diffusion that, in turn, limits the practical thickness of suitable components to about 1 mm. Opportunities for continued development have been identified for application to other compositions, and to further refine microstructure control.
{"title":"SHAPE: Shape Memory Alloys via Halide-Activated Pack Eqilibration","authors":"A. S. King, D. Lipke, R. D. Dempsey, D. Lipke","doi":"10.31399/asm.cp.smst2022p0099","DOIUrl":"https://doi.org/10.31399/asm.cp.smst2022p0099","url":null,"abstract":"\u0000 Achieving stringent chemistry standards is necessary for additive manufacturing of Nitinol shape memory alloys. This work describes an elevated temperature gas-solid reaction processing technique that can be used to precisely regulate the chemistry and phase transformation behaviors of Nitinol components. The technique, Shape memory alloys via Halide-Activated Pack Equilibration (SHAPE), employs established principles of chemical vapor transport to equilibrate a substrate against reactive pack mixtures designed to regulate the chemical potentials of nickel and titanium in accordance with Gibbs' phase rule as means to precisely control substrate phase and elemental composition. The results suggest that SHAPE may find crosscutting potential especially when paired with additive manufacturing or fusion welding of Nitinol to improve product quality. Notwithstanding future applications, SHAPE is limited by solid-state diffusion that, in turn, limits the practical thickness of suitable components to about 1 mm. Opportunities for continued development have been identified for application to other compositions, and to further refine microstructure control.","PeriodicalId":119283,"journal":{"name":"SMST 2022: Extended Abstracts from the International Conference on Shape Memory and Superelastic Technologies","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126557989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-16DOI: 10.31399/asm.cp.smst2022p0051
M. Bernini, A. Lucchetti, C. Dunlop, R. Hellmuth, W. Ronan, T. Vaughan
Self-expanding Nitinol stents are the preferred treatment for atherosclerotic diseases in femoral arteries. However, adverse clinical outcomes are recorded and mostly attributed to altered flow dynamics caused by the device, which can lead to in-stent restenosis in 15% to 32% of stented segments within 9 to 15 months post-intervention. Spiral laminar flow (SLF) technology consists of a helical ridge on the inner surface of the device, which recovers the natural helical blood flow downstream and reduces flow disturbance and turbulence caused by stenting, thus preventing disease progression. This study presents the manufacturing process developed to obtain the SLF technology on self-expanding Nitinol devices, either laser-cut or braided, and addresses the optimal manufacturing parameters to ensure mechanical performance (radial strength, crush load resistance) and physical characteristics (phase transition temperature, surface finishing) appropriate for endovascular applications.
{"title":"Spiral Laminal Flow™ Technology in a Self-Expanding Nitinol Stent: Investigation on the Manufacturing Process","authors":"M. Bernini, A. Lucchetti, C. Dunlop, R. Hellmuth, W. Ronan, T. Vaughan","doi":"10.31399/asm.cp.smst2022p0051","DOIUrl":"https://doi.org/10.31399/asm.cp.smst2022p0051","url":null,"abstract":"\u0000 Self-expanding Nitinol stents are the preferred treatment for atherosclerotic diseases in femoral arteries. However, adverse clinical outcomes are recorded and mostly attributed to altered flow dynamics caused by the device, which can lead to in-stent restenosis in 15% to 32% of stented segments within 9 to 15 months post-intervention. Spiral laminar flow (SLF) technology consists of a helical ridge on the inner surface of the device, which recovers the natural helical blood flow downstream and reduces flow disturbance and turbulence caused by stenting, thus preventing disease progression. This study presents the manufacturing process developed to obtain the SLF technology on self-expanding Nitinol devices, either laser-cut or braided, and addresses the optimal manufacturing parameters to ensure mechanical performance (radial strength, crush load resistance) and physical characteristics (phase transition temperature, surface finishing) appropriate for endovascular applications.","PeriodicalId":119283,"journal":{"name":"SMST 2022: Extended Abstracts from the International Conference on Shape Memory and Superelastic Technologies","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128794192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-16DOI: 10.31399/asm.cp.smst2022p0093
B. Schelnberger, R. Krieg, R. Theiss, P. Dültgen
Alloys based on CuAl have been a promising option for high-temperature SMAs (HTSMA) because of their procedural and cost advantages over NiTi-based high-temperature SMAs. Despite their excellent shape memory as well as phase stability at temperatures up to 250°C, their brittle behavior and the degradation of the shape memory effect under cyclic stress have provided obstacles to widespread application. While multiple remelting processes are often applied to avoid inhomogeneities in the production of these alloys, single step inductive melting is preferable in terms of productivity, especially for small alloy batches. The goal of this and consecutive work is to characterize, and reduce, the variation of material properties and microstructure in materials prepared by vacuum-induction melting of pure elements and tilt-casting. To this end, castings from pure metals with 5 target chemical compositions from Cu12.5wt.%Al4wt.%Ni to Cu13.2wt.%Al4wt.%Ni were prepared and characterized in terms of transformation temperatures and occurrence of martensitic phases. Samples taken from different positions in the casting were compared. Changes in microstructure with increased aluminum content of the alloy could be assessed in both metallographic and calorimetric analysis. Considerable consistency of transformation temperatures and phase composition in each individual casting, as well as between castings with identical parameters, could be achieved. This points to the high degree of homogenization that can be achieved, even with a single melting cycling and subsequent casting, using suitable induction melting parameters. The absence of oxide and carbide inclusions, despite potential reactions between nickel and the graphite of the crucible, is promising for future casting processes.
基于CuAl的合金与基于niti的高温sma相比，由于其工艺和成本优势，已经成为高温sma (HTSMA)的一个很有前途的选择。尽管它们在高达250°C的温度下具有优异的形状记忆和相稳定性，但它们的脆性行为和循环应力下形状记忆效应的退化为其广泛应用提供了障碍。虽然在这些合金的生产中经常采用多次重熔工艺来避免不均匀性，但就生产率而言，单步感应熔化是优选的，特别是对于小批量的合金。本工作和后续工作的目标是表征和减少纯元素真空感应熔炼和倾斜铸造制备的材料的材料性能和显微组织的变化。为此，用Cu12.5wt.%Al4wt的5种目标化学成分的纯金属铸造。%Ni to Cu13.2wt.%Al4wt。制备了%Ni，并对相变温度和马氏体相的出现进行了表征。从铸件的不同位置采集的样品进行了比较。随着铝含量的增加，合金组织的变化可以通过金相分析和量热分析来评估。每个铸件以及具有相同参数的铸件之间的相变温度和相组成具有相当大的一致性。这表明，即使使用合适的感应熔化参数，通过单次熔化循环和随后的铸造，也可以实现高度的均匀化。尽管镍和坩埚的石墨之间存在潜在的反应，但没有氧化物和碳化物夹杂物，这对未来的铸造工艺很有希望。
{"title":"Variation of Material Properties in Tilt-Cast Cu-Al-Ni Alloy","authors":"B. Schelnberger, R. Krieg, R. Theiss, P. Dültgen","doi":"10.31399/asm.cp.smst2022p0093","DOIUrl":"https://doi.org/10.31399/asm.cp.smst2022p0093","url":null,"abstract":"\u0000 Alloys based on CuAl have been a promising option for high-temperature SMAs (HTSMA) because of their procedural and cost advantages over NiTi-based high-temperature SMAs. Despite their excellent shape memory as well as phase stability at temperatures up to 250°C, their brittle behavior and the degradation of the shape memory effect under cyclic stress have provided obstacles to widespread application. While multiple remelting processes are often applied to avoid inhomogeneities in the production of these alloys, single step inductive melting is preferable in terms of productivity, especially for small alloy batches. The goal of this and consecutive work is to characterize, and reduce, the variation of material properties and microstructure in materials prepared by vacuum-induction melting of pure elements and tilt-casting. To this end, castings from pure metals with 5 target chemical compositions from Cu12.5wt.%Al4wt.%Ni to Cu13.2wt.%Al4wt.%Ni were prepared and characterized in terms of transformation temperatures and occurrence of martensitic phases. Samples taken from different positions in the casting were compared. Changes in microstructure with increased aluminum content of the alloy could be assessed in both metallographic and calorimetric analysis. Considerable consistency of transformation temperatures and phase composition in each individual casting, as well as between castings with identical parameters, could be achieved. This points to the high degree of homogenization that can be achieved, even with a single melting cycling and subsequent casting, using suitable induction melting parameters. The absence of oxide and carbide inclusions, despite potential reactions between nickel and the graphite of the crucible, is promising for future casting processes.","PeriodicalId":119283,"journal":{"name":"SMST 2022: Extended Abstracts from the International Conference on Shape Memory and Superelastic Technologies","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131781177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-16DOI: 10.31399/asm.cp.smst2022p0036
A. Demblon, J. Mabe, I. Karaman
NiTiHf high temperature shape memory alloys (HTSMAs) are being used in an ever-growing array of applications, specifically in the aerospace and automotive industries. One of the difficulties facing further implementation is ensuring the actuation fatigue lifetime is sufficiently long as to prevent the HTSMA components from being a limiting factor to the mean time between failures of a system. Another potential problem for widespread use is the deterioration of actuation stroke during lifetime, which can be problematic when attempting to have a high-fidelity repeatable design. One way of solving these issues is to optimize the microstructure through careful control of composition, processing, and heat treatments. Current research shows composition of large-scale productions is incredibly difficult to control, and small deviations in composition (~0.1 at.% Ni) can result in changes in transformation temperature by 50?C or more. Four NiTiHf compositions were investigated. The initial goal to simply extend the actuation fatigue lifetime and provide a stable actuation response morphed into determining material factors that influence the actuation response of partially cycled samples.
{"title":"Extending the Fatigue Life of NiTiHf High Temperature Shape Memory Alloys through Partial Thermal Cycling","authors":"A. Demblon, J. Mabe, I. Karaman","doi":"10.31399/asm.cp.smst2022p0036","DOIUrl":"https://doi.org/10.31399/asm.cp.smst2022p0036","url":null,"abstract":"\u0000 NiTiHf high temperature shape memory alloys (HTSMAs) are being used in an ever-growing array of applications, specifically in the aerospace and automotive industries. One of the difficulties facing further implementation is ensuring the actuation fatigue lifetime is sufficiently long as to prevent the HTSMA components from being a limiting factor to the mean time between failures of a system. Another potential problem for widespread use is the deterioration of actuation stroke during lifetime, which can be problematic when attempting to have a high-fidelity repeatable design. One way of solving these issues is to optimize the microstructure through careful control of composition, processing, and heat treatments. Current research shows composition of large-scale productions is incredibly difficult to control, and small deviations in composition (~0.1 at.% Ni) can result in changes in transformation temperature by 50?C or more. Four NiTiHf compositions were investigated. The initial goal to simply extend the actuation fatigue lifetime and provide a stable actuation response morphed into determining material factors that influence the actuation response of partially cycled samples.","PeriodicalId":119283,"journal":{"name":"SMST 2022: Extended Abstracts from the International Conference on Shape Memory and Superelastic Technologies","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124232170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-16DOI: 10.31399/asm.cp.smst2022p0032
Siyuan Cheng, Xueshi Li, Jiongjiong Zhang, Guoan Zhou, Yuxiang Zhu, S. Yao, Q. Sun
Elastocaloric refrigeration using superelastic NiTi shape memory alloys (SMAs) has attracted much attention recently because it has a large energy saving potential, no environmental effects, and a low cost. Achieving the continuous operating of elastocaloric devices, i.e., separating the cold and hot areas on the NiTi alloys physically, helps the efficient release and absorption of heat and avoid the reciprocal parts and intervals of outputs in the system. In this paper, an analytical model and proof-of-concept experiments for continuous operating (elasto)caloric devices are presented. The experimental concept was developed based on a set of rotating NiTi sheets with which the copper heat sink and heat source contact cyclically.
{"title":"Continuous Operating Elastocaloric Device: Model and Experiments","authors":"Siyuan Cheng, Xueshi Li, Jiongjiong Zhang, Guoan Zhou, Yuxiang Zhu, S. Yao, Q. Sun","doi":"10.31399/asm.cp.smst2022p0032","DOIUrl":"https://doi.org/10.31399/asm.cp.smst2022p0032","url":null,"abstract":"\u0000 Elastocaloric refrigeration using superelastic NiTi shape memory alloys (SMAs) has attracted much attention recently because it has a large energy saving potential, no environmental effects, and a low cost. Achieving the continuous operating of elastocaloric devices, i.e., separating the cold and hot areas on the NiTi alloys physically, helps the efficient release and absorption of heat and avoid the reciprocal parts and intervals of outputs in the system. In this paper, an analytical model and proof-of-concept experiments for continuous operating (elasto)caloric devices are presented. The experimental concept was developed based on a set of rotating NiTi sheets with which the copper heat sink and heat source contact cyclically.","PeriodicalId":119283,"journal":{"name":"SMST 2022: Extended Abstracts from the International Conference on Shape Memory and Superelastic Technologies","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129017300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-16DOI: 10.31399/asm.cp.smst2022p0103
R. Pipes, S. Nagaraja, A. Pelton, P. Hempel, Adna Yazici, Danyal A Siddiqui
Although improvements in fatigue performance with increasing Nitinol microstructural purity have been previously characterized, there is limited information on whether corrosion resistance is impacted by reductions in inclusion size and distribution. The objective of this study is to characterize the surface oxide for different Nitinol microstructural purities and determine its influence on corrosion susceptibility. To assess the surface oxide, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) were performed on Nitinol heart valve frames with a variety of purities and surface finishes.
{"title":"Surface Characterization and Corrosion Resistance of Generation I-III Nitinol with Various Surface Finishes","authors":"R. Pipes, S. Nagaraja, A. Pelton, P. Hempel, Adna Yazici, Danyal A Siddiqui","doi":"10.31399/asm.cp.smst2022p0103","DOIUrl":"https://doi.org/10.31399/asm.cp.smst2022p0103","url":null,"abstract":"\u0000 Although improvements in fatigue performance with increasing Nitinol microstructural purity have been previously characterized, there is limited information on whether corrosion resistance is impacted by reductions in inclusion size and distribution. The objective of this study is to characterize the surface oxide for different Nitinol microstructural purities and determine its influence on corrosion susceptibility. To assess the surface oxide, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) were performed on Nitinol heart valve frames with a variety of purities and surface finishes.","PeriodicalId":119283,"journal":{"name":"SMST 2022: Extended Abstracts from the International Conference on Shape Memory and Superelastic Technologies","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116867415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-16DOI: 10.31399/asm.cp.smst2022p0061
S. Tripathy, Koray Senol, H. Cao, Doug Dominick, M. Wu
Strain-based criteria is most often used for characterizing the fatigue reliability of Nitinol cardiovascular devices. Fatigue testing of Nitinol specimens has also relied on finite element analysis (FEA) to compute cyclic strain amplitudes and mean strains. Recently, the digital image correlation (DIC) technique has been shown to have high resolution to experimentally determine the local material strains of Nitinol fatigue specimens. In this study, the authors explored the feasibility of alignment between DIC strain measurement, and the strain calculated by the continuum mechanics approach used in the FEA technique. The agreements and discrepancies are discussed with their implications on fatigue reliability assessment of Nitinol cardiovascular devices.
{"title":"Fatigue Strain Verification for Cardiovascular Implantable Nitinol Devices","authors":"S. Tripathy, Koray Senol, H. Cao, Doug Dominick, M. Wu","doi":"10.31399/asm.cp.smst2022p0061","DOIUrl":"https://doi.org/10.31399/asm.cp.smst2022p0061","url":null,"abstract":"\u0000 Strain-based criteria is most often used for characterizing the fatigue reliability of Nitinol cardiovascular devices. Fatigue testing of Nitinol specimens has also relied on finite element analysis (FEA) to compute cyclic strain amplitudes and mean strains. Recently, the digital image correlation (DIC) technique has been shown to have high resolution to experimentally determine the local material strains of Nitinol fatigue specimens. In this study, the authors explored the feasibility of alignment between DIC strain measurement, and the strain calculated by the continuum mechanics approach used in the FEA technique. The agreements and discrepancies are discussed with their implications on fatigue reliability assessment of Nitinol cardiovascular devices.","PeriodicalId":119283,"journal":{"name":"SMST 2022: Extended Abstracts from the International Conference on Shape Memory and Superelastic Technologies","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114090313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：