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Mechanical Behavior of Shape Memory Alloys: 2022
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Mechanical Behavior of Shape Memory Alloys: 2022

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Metals and Alloys".

Deadline for manuscript submissions: closed (20 November 2022) | Viewed by 37080

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Dr. Salvatore Saputo

E-Mail Website
Guest Editor
Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
Interests: CDM; delamination; dynamic analysis

Special Issue Information

Dear Colleagues,

Over recent years, interest in shape material alloys has continuously increased in several fields, such as aerospace, automotive, naval, civil, and biology. The features that make shape memory alloys attractive are the ability to recover a deformation after heating and the pseudoelastic stress–strain behavior for large deformations, as well as the biocompatibility that makes these alloys extremely interesting for the bioengineering application. To effectively use shape memory alloys, an accurate description of certain characteristics such as the critical transformation temperature and stress values is mandatory. All researchers working on shape memory materials are invited to contribute their work to this Special Issue on the “Mechanical Behavior of Shape Memory Alloys: 2021”, which will cover different topics concerning the behavior of shape memory materials from an analytical, experimental, and numerical perspective. Contributions on manufacturing processes with shape memory materials and smart structures are welcome.

The following topics will be covered in this Special Issue, among others:

  • Smart materials;
  • Smart structure and devices;
  • Piezoelectric materials;
  • Shape memory alloys (SMAs);
  • Shape memory effect (SME);
  • Analytical and numerical smart materials models;
  • Smart materials properties and characterizations;
  • Self-recovering materials;
  • SMA manufacturing, testing, and design;
  • SMA thermomechanical behavior;
  • SMA thermoelectric behavior.

Dr. Salvatore Saputo
Guest Editor

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Keywords

  • shape memory alloy (SMAs)
  • shape memory effect (SME)
  • superelasticity
  • smart materials
  • constitutive models
  • simulation and modeling
  • smart devices

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Published Papers (16 papers)

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Research

16 pages, 11407 KiB  
Article
Structure and Mechanical Properties of the NiTi Wire Joined by Laser Welding
by Tomasz Goryczka, Karol Gryń, Adrian Barylski and Barbara Szaraniec
Materials 2023, 16(7), 2543; https://doi.org/10.3390/ma16072543 - 23 Mar 2023
Cited by 1 | Viewed by 1675
Abstract
Joining wires made of NiTi alloys with shape memory effect and pseudoelasticity causes many technical and structural problems. They result from unwanted phase interactions that occur in high temperatures and negatively affect the characteristics of these materials. Such obstacles are challenging in terms [...] Read more.
Joining wires made of NiTi alloys with shape memory effect and pseudoelasticity causes many technical and structural problems. They result from unwanted phase interactions that occur in high temperatures and negatively affect the characteristics of these materials. Such obstacles are challenging in terms of welding. Hence, an attempt was made to join NiTi wires via an economical and reliable basic laser welding technique which does not require complicated equipment and gas protection. The parameters such as spot diameter and pulse time were constant and only the laser power, calculated as a percentage of the total power, was optimized. The wires were parallelly connected with overlapping seam welds 10 mm long. The welds were examined regarding their microstructure, chemical and phase composition, reversible martensitic transformation, microhardness, and pseudoelasticity. The obtained results showed that the joint was completed at the 12–14% power. The weld revealed good quality with no voids or pores. As the laser power increased, the microhardness rose from 282 (for 4%) to 321 (for 14%). The joint withstood the stress-inducing reversible martensitic transformation. As the transformation was repeated cyclically, the stress value decreased from 587 MPa (initial wire) to 507 MPa (for the 14% power welded wire). Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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11 pages, 7046 KiB  
Article
An SMA Transducer for Sensing Tactile Sensation Focusing on Stroking Motion
by Ryusei Oya and Hideyuki Sawada
Materials 2023, 16(3), 1016; https://doi.org/10.3390/ma16031016 - 22 Jan 2023
Cited by 2 | Viewed by 2031
Abstract
The authors have developed a micro-vibration actuator using filiform SMA wire electrically driven by periodic electric current. While applying the SMA actuators to tactile displays, we discovered a phenomenon that the deformation caused by a given stress to an SMA wire generated a [...] Read more.
The authors have developed a micro-vibration actuator using filiform SMA wire electrically driven by periodic electric current. While applying the SMA actuators to tactile displays, we discovered a phenomenon that the deformation caused by a given stress to an SMA wire generated a change in the electrical resistance. With this characteristic, the SMA wire works as a micro-force sensor with high sensitivity, while generating micro-vibration. In this paper, the micro-force sensing ability of an SMA transducer is described and discussed. Experiments are conducted by sliding the SMA sensor on the surface of different objects with different speeds, and the sensing ability is evaluated to be related with human tactile sensation. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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12 pages, 5016 KiB  
Article
Production, Mechanical and Functional Properties of Long-Length TiNiHf Rods with High-Temperature Shape Memory Effect
by Roman Karelin, Victor Komarov, Vladimir Cherkasov, Vladimir Yusupov, Sergey Prokoshkin and Vladimir Andreev
Materials 2023, 16(2), 615; https://doi.org/10.3390/ma16020615 - 9 Jan 2023
Cited by 1 | Viewed by 1369
Abstract
In the present work, the possibility of manufacturing long-length TiNiHf rods with a lowered Hf content and a high-temperature shape memory effect in the range of 120–160 °C was studied. Initial ingots with 1.5, 3.0 and 5.0 at.% Hf were obtained by electron [...] Read more.
In the present work, the possibility of manufacturing long-length TiNiHf rods with a lowered Hf content and a high-temperature shape memory effect in the range of 120–160 °C was studied. Initial ingots with 1.5, 3.0 and 5.0 at.% Hf were obtained by electron beam melting in a copper water-cooled stream-type mold. The obtained ingots were rotary forged at the temperature of 950 °C, with the relative strain from 5 to 10% per one pass. The obtained results revealed that the ingots with 3.0 and 5.0 at.% Hf demonstrated insufficient technological plasticity, presumably because of the excess precipitation of (Ti,Hf)2Ni-type particles. The premature destruction of ingots during the deformation process does not allow obtaining high-quality long-length rods. A long-length rod with a diameter of 3.5 mm and a length of 870 mm was produced by rotary forging from the ingot with 1.5 at.% Hf. The obtained TiNiHf rod had relatively high values of mechanical properties (a dislocation yield stress σy of 800 MPa, ultimate tensile strength σB of 1000 MPa, and elongation to fracture δ of 24%), functional properties (a completely recoverable strain of 5%), and a required finishing temperature of shape recovery of 125 °C in the as-forged state and of 155 °C after post-deformation annealing at 550 °C for 2 h. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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9 pages, 2420 KiB  
Article
Evolution of Structure and Properties of Nickel-Enriched NiTi Shape Memory Alloy Subjected to Bi-Axial Deformation
by Victor Komarov, Roman Karelin, Irina Khmelevskaya, Vladimir Cherkasov, Vladimir Yusupov, Grzegorz Korpala, Rudolf Kawalla, Ulrich Prahl and Sergey Prokoshkin
Materials 2023, 16(2), 511; https://doi.org/10.3390/ma16020511 - 5 Jan 2023
Cited by 2 | Viewed by 1650
Abstract
The effect of a promising method of performing a thermomechanical treatment which provides the nanocrystalline structure formation in bulk NiTi shape memory alloy samples and a corresponding improvement to their properties was studied in the present work. The bi-axial severe plastic deformation of [...] Read more.
The effect of a promising method of performing a thermomechanical treatment which provides the nanocrystalline structure formation in bulk NiTi shape memory alloy samples and a corresponding improvement to their properties was studied in the present work. The bi-axial severe plastic deformation of Ti-50.7at.%Ni alloy was carried out on the MaxStrain module of the Gleeble system at 350 and 330 °C with accumulated true strains of e = 6.6–9.5. The obtained structure and its mechanical and functional properties and martensitic transformations were studied using DSC, X-ray diffractometry, and TEM. A nanocrystalline structure with a grain/subgrain size of below 80 nm was formed in bulk nickel-enriched NiTi alloy after the MaxStrain deformation at 330 °C with e = 9.5. The application of MaxStrain leads to the formation of a nanocrystalline structure that is characterized by the appearance of a nano-sized grains and subgrains with equiaxed and elongated shapes and a high free dislocation density. After the MaxStrain deformation at 330 °C with e = 9.5 was performed, the completely nanocrystalline structure with the grain/subgrain size of below 80 nm was formed in bulk nickel-enriched NiTi alloy for the first time. The resulting structure provides a total recoverable strain of 12%, which exceeds the highest values that have been reported for bulk nickel-enriched NiTi samples. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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17 pages, 18699 KiB  
Article
Effect of Severe Plastic Deformation and Post-Deformation Heat Treatment on the Microstructure and Superelastic Properties of Ti-50.8 at.% Ni Alloy
by Tae-Jin Lee and Woo-Jin Kim
Materials 2022, 15(21), 7822; https://doi.org/10.3390/ma15217822 - 5 Nov 2022
Cited by 6 | Viewed by 1888
Abstract
Severe plastic deformation via high-ratio differential speed rolling (HRDSR) was applied to the Ni-rich Ti-50.8Ni alloy. Application of HRDSR and a short annealing time of 5 min at 873 K leads to the production of a partially recrystallized microstructure with a small grain [...] Read more.
Severe plastic deformation via high-ratio differential speed rolling (HRDSR) was applied to the Ni-rich Ti-50.8Ni alloy. Application of HRDSR and a short annealing time of 5 min at 873 K leads to the production of a partially recrystallized microstructure with a small grain size of 5.1 μm. During the aging process for the annealed HRDSR sample at 523 K for 16 h, a high density of Ni3Ti4 particles was uniformly precipitated over the matrix, resulting in the formation of an R phase as the major phase at room temperature. The aged HRDSR sample exhibits excellent superelasticity and superelastic cyclability. This achievement can be attributed to an increase in strength through effective grain refinement and particle strengthening by Ni3Ti4 and a decrease in the critical stress for stress-induced martensite (B19′) due to the presence of the R-phase instead of B2 as a major phase at room temperature. The currently proposed method for using HRDSR and post-deformation heat treatment allows for the production of Ni-rich NiTi alloys with excellent superelasticity in sheet form. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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18 pages, 6060 KiB  
Article
Thermal–Optical Evaluation of an Optimized Trough Solar Concentrator for an Advanced Solar-Tracking Application Using Shape Memory Alloy
by Nasir Ghazi Hariri, Kamal Mohamed Nayel, Emad Khalid Alyoubi, Ibrahim Khalil Almadani, Ibrahim Sufian Osman and Badr Ahmed Al-Qahtani
Materials 2022, 15(20), 7110; https://doi.org/10.3390/ma15207110 - 13 Oct 2022
Cited by 4 | Viewed by 3193
Abstract
One of the modern methods for enhancing the efficiency of photovoltaic (PV) systems is implementing a solar tracking mechanism in order to redirect PV modules toward the sun throughout the day. However, the use of solar trackers increases the system’s electrical consumption, hindering [...] Read more.
One of the modern methods for enhancing the efficiency of photovoltaic (PV) systems is implementing a solar tracking mechanism in order to redirect PV modules toward the sun throughout the day. However, the use of solar trackers increases the system’s electrical consumption, hindering its net generated energy. In this study, a novel self-tracking solar-driven PV system is proposed. The smart solar-driven thermomechanical actuator takes advantage of a solar heat collector (SHC) device, in the form of a parabolic trough solar concentrator (PTC), and smart shape memory alloy (SMA) to produce effective mechanical energy for solar tracking applications from sun rays. Furthermore, a thermal–optical analysis is presented to evaluate the performance of the solar concentrator for the simulated weather condition of Dammam City, Saudi Arabia. The numerical results of the thermal and optical analyses show the promising feasibility of the proposed system in which SMA springs with an activation temperature between 31.09 °C and 45.15 °C can be utilized for the self-tracking operations. The work presented adds to the body of knowledge an advanced SMA-based SHC device for solar-based self-actuation systems, which enables further expansions within modern and advanced solar thermal applications. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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21 pages, 10653 KiB  
Article
A State-of-the-Art Self-Cleaning System Using Thermomechanical Effect in Shape Memory Alloy for Smart Photovoltaic Applications
by Nasir Ghazi Hariri, Ibrahim Khalil Almadani and Ibrahim Sufian Osman
Materials 2022, 15(16), 5704; https://doi.org/10.3390/ma15165704 - 18 Aug 2022
Cited by 8 | Viewed by 2535
Abstract
This research aims to present a state-of-the-art cleaning technology solution that effectively overcomes the dust accumulation issue for conventional photovoltaic systems. Although continuous innovations and advanced developments within renewable energy technologies have shown steady improvements over the past years, the dust accumulation issue [...] Read more.
This research aims to present a state-of-the-art cleaning technology solution that effectively overcomes the dust accumulation issue for conventional photovoltaic systems. Although continuous innovations and advanced developments within renewable energy technologies have shown steady improvements over the past years, the dust accumulation issue remains one of the main factors hindering their efficiency and degradation rate. By harvesting abundant solar thermal energy, the presented self-cleaning system uses a unique thermomechanical property of Shape Memory Alloys to operate a solar-based thermomechanical actuator. Therefore, this study carries out different numerical and experimental validation tests to highlight the promising practicability of the developed self-cleaning system from thermal and mechanical perspectives. The results showed that the system has a life expectancy of over 20 years, which is closely equivalent to the life expectancy of conventional photovoltaic modules while operating under actual weather conditions in Dammam city. Additionally, the thermal to mechanical energy conversion efficiency reached 19.15% while providing average cleaning effectiveness of about 95%. The presented outcomes of this study add to the body of knowledge an innovative methodology for a unique solar-based self-cleaning system aimed toward smart and modern photovoltaic applications. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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13 pages, 3954 KiB  
Article
Microwave versus Conventional Sintering of NiTi Alloys Processed by Mechanical Alloying
by Rodolfo da Silva Teixeira, Rebeca Vieira de Oliveira, Patrícia Freitas Rodrigues, João Mascarenhas, Filipe Carlos Figueiredo Pereira Neves and Andersan dos Santos Paula
Materials 2022, 15(16), 5506; https://doi.org/10.3390/ma15165506 - 11 Aug 2022
Cited by 6 | Viewed by 1991
Abstract
The present study shows a comparison between two sintering processes, microwave and conventional sintering, for the manufacture of NiTi porous specimens starting from powder mixtures of nickel and titanium hydrogenation–dehydrogenation (HDH) milled by mechanical alloying for a short time (25 min). The samples [...] Read more.
The present study shows a comparison between two sintering processes, microwave and conventional sintering, for the manufacture of NiTi porous specimens starting from powder mixtures of nickel and titanium hydrogenation–dehydrogenation (HDH) milled by mechanical alloying for a short time (25 min). The samples were sintered at 850 °C for 15 min and 120 min, respectively. Both samples exhibited porosity, and the pore size results are within the range of the human bone. The NiTi intermetallic compound (B2, R-phase, and B19′) was detected in both sintered samples through X-ray diffraction (XRD) and electron backscattering diffraction (EBSD) on scanning electron microscopic (SEM). Two-step phase transformation occurred in both sintering processes with cooling and heating, the latter occurring with an overlap of the peaks, according to the differential scanning calorimetry (DSC) results. From scanning electron microscopy/electron backscatter diffraction, the R-phase and B2/B19′ were detected in microwave and conventional sintering, respectively. The instrumented ultramicrohardness results show the highest elastic work values for the conventionally sintered sample. It was observed throughout this investigation that using mechanical alloying (MA) powders enabled, in both sintering processes, good results, such as intermetallic formation and densification in the range for biomedical applications. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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10 pages, 3385 KiB  
Article
The Study of New NiTi Actuators to Reinforce the Wing Movement of Aircraft Systems
by Rafael Braga, Patrícia Freitas Rodrigues, Hélder Cordeiro, Pedro Carreira and Maria Teresa Vieira
Materials 2022, 15(14), 4787; https://doi.org/10.3390/ma15144787 - 8 Jul 2022
Cited by 4 | Viewed by 1838
Abstract
Actuators using Shape Memory Alloy (SMA) springs could operate in different mechanical systems requiring geometric flexibility and high performance. The aim of the present study is to highlight the potential of these actuators, using their dimensional variations resulting from the phase transformations of [...] Read more.
Actuators using Shape Memory Alloy (SMA) springs could operate in different mechanical systems requiring geometric flexibility and high performance. The aim of the present study is to highlight the potential of these actuators, using their dimensional variations resulting from the phase transformations of NiTi springs (SMA) to make the movements of the system’s mobile components reversible. This reversibility is due to thermal-induced martensitic transformation of NiTi springs. The transformation promotes the extended and retracted of the springs as the phase changing (martensite–austenite) creates movement in part of the system. Therefore, the phase transition temperatures of NiTi, evaluated by differential scanning calorimetry (DSC), are required to control the dimensional variation of the spring. The influence of the number of springs in the system, as well as how impacts on the reaction time were evaluated. The different numbers of springs (two, four, and six) and the interspaces between them made it possible to control the time and the final angle attained in the mobile part of the system. Mechanical resistance, maximum angle, and the system’s reaction time using different NiTi springs highlight the role of the actuators. Fused Deposition Modelling (FDM)/Material Extrusion (MEX) or Selective Laser Sintering (SLS) was selected for shaping the composite matrix system. A new prototype was designed and developed to conduct tests that established the relationship between the recoverable deformation of the matrix suitable for the application as well as the number and distribution of the actuators. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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9 pages, 28886 KiB  
Article
In Situ Observation of Thermoelastic Martensitic Transformation of Cu-Al-Mn Cryogenic Shape Memory Alloy with Compressive Stress
by Zhenyu Bian, Jian Song, Pingping Liu, Farong Wan, Yu Lei, Qicong Wang, Shanwu Yang, Qian Zhan, Liubiao Chen and Junjie Wang
Materials 2022, 15(11), 3794; https://doi.org/10.3390/ma15113794 - 26 May 2022
Cited by 4 | Viewed by 1950
Abstract
The thermoelastic martensitic transformation and its reverse transformation of the Cu-Al-Mn cryogenic shape memory alloy, both with and without compressive stress, has been dynamically in situ observed. During the process of thermoelastic martensitic transformation, martensite nucleates and gradually grow up as they cool, [...] Read more.
The thermoelastic martensitic transformation and its reverse transformation of the Cu-Al-Mn cryogenic shape memory alloy, both with and without compressive stress, has been dynamically in situ observed. During the process of thermoelastic martensitic transformation, martensite nucleates and gradually grow up as they cool, and shrink to disappearance as they heat. The order of martensite disappearance is just opposite to that of their formation. Observations of the self-accommodation of martensite variants, which were carried out by using a low temperature metallographic in situ observation apparatus, showed that the variants could interact with each other. The results of in situ synchrotron radiation X-ray and metallographic observation also suggested there were some residual austenites, even if the temperature was below Mf, which means the martensitic transformation could not be 100% accomplished. The external compressive stress would promote the preferential formation of martensite with some orientation, and also hinder the formation of martensite with other nonequivalent directions. The possible mechanism of the martensitic reverse transformation is discussed. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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9 pages, 5503 KiB  
Article
The Effect of Heat Treatment on Damping Capacity and Mechanical Properties of CuAlNi Shape Memory Alloy
by Ivana Ivanić, Stjepan Kožuh, Tamara Holjevac Grgurić, Ladislav Vrsalović and Mirko Gojić
Materials 2022, 15(5), 1825; https://doi.org/10.3390/ma15051825 - 28 Feb 2022
Cited by 10 | Viewed by 2185
Abstract
This paper discusses the effect of different heat treatment procedures on the microstructural characteristics, damping capacities, and mechanical properties of CuAlNi shape memory alloys (SMA). The investigation was performed on samples in the as-cast state and heat treated states (solution annealing at 885 [...] Read more.
This paper discusses the effect of different heat treatment procedures on the microstructural characteristics, damping capacities, and mechanical properties of CuAlNi shape memory alloys (SMA). The investigation was performed on samples in the as-cast state and heat treated states (solution annealing at 885 °C/60′/H2O and after tempering at 300 °C/60′/H2O). The microstructure of the samples was examined by light microscopy (LM) and scanning electron microscopy (SEM) equipped with a device for energy dispersive spectrometry (EDS) analysis. Light and scanning electron microscopy showed martensitic microstructure in all investigated samples. However, the changes in microstructure due to heat treatment by the presence of two types of martensite phases (β1′ and γ1′) influenced alloy damping and mechanical properties by enhancing alloy damping characteristics. Heat treatment procedure reduced the alloys’ mechanical properties and increased hardness of the alloy. Fractographic analysis of the alloy showed a transgranular type of fracture in samples after casting. After solution annealing, two types of fracture mechanisms can be noticed, transgranular and intergranular, while in tempered samples, mostly an intergranular type of fracture exists. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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20 pages, 3484 KiB  
Article
Optimized Neural Network Prediction Model of Shape Memory Alloy and Its Application for Structural Vibration Control
by Meng Zhan, Junsheng Liu, Deli Wang, Xiuyun Chen, Lizhen Zhang and Sheliang Wang
Materials 2021, 14(21), 6593; https://doi.org/10.3390/ma14216593 - 2 Nov 2021
Cited by 9 | Viewed by 1872
Abstract
The traditional mathematical model of shape memory alloy (SMA) is complicated and difficult to program in numerical analysis. The artificial neural network is a nonlinear modeling method which does not depend on the mathematical model and avoids the inevitable error in the traditional [...] Read more.
The traditional mathematical model of shape memory alloy (SMA) is complicated and difficult to program in numerical analysis. The artificial neural network is a nonlinear modeling method which does not depend on the mathematical model and avoids the inevitable error in the traditional modeling method. In this paper, an optimized neural network prediction model of shape memory alloy and its application for structural vibration control are discussed. The superelastic properties of austenitic SMA wires were tested by experiments. The material property test data were taken as the training samples of the BP neural network, and a prediction model optimized by the genetic algorithm was established. By using the improved genetic algorithm, the position and quantity of the SMA wires were optimized in a three-storey spatial structure, and the dynamic response analysis of the optimal arrangement was carried out. The results show that, compared with the unoptimized neural network prediction model of SMA, the optimized prediction model is in better agreement with the test curve and has higher stability, it can well reflect the effect of loading rate on the superelastic properties of SMA, and is a high precision rate-dependent dynamic prediction model. Moreover, the BP network constitutive model is simple to use and convenient for dynamic simulation analysis of an SMA passive control structure. The controlled structure with optimized SMA wires can inhibit the structural seismic responses more effectively. However, it is not the case that the more SMA wires, the better the shock absorption effect. When SMA wires exceed a certain number, the vibration reduction effect gradually decreases. Therefore, the seismic effect can be reduced economically and effectively only when the number and location of SMA wires are properly configured. When four SMA wires are arranged, the acceptable shock absorption effect is obtained, and the sum of the structural storey drift can be reduced by 44.51%. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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15 pages, 5858 KiB  
Article
Modelling of SMA Vibration Systems in an AVA Example
by Waldemar Rączka, Jarosław Konieczny and Marek Sibielak
Materials 2021, 14(19), 5905; https://doi.org/10.3390/ma14195905 - 8 Oct 2021
Cited by 1 | Viewed by 1803
Abstract
Vibration suppression, as well as its generation, is a common subject of scientific investigations. More and more often, but still rarely, shape memory alloys (SMAs) are used in vibrating systems, despite the fact that SMA springs have many advantages. This is due to [...] Read more.
Vibration suppression, as well as its generation, is a common subject of scientific investigations. More and more often, but still rarely, shape memory alloys (SMAs) are used in vibrating systems, despite the fact that SMA springs have many advantages. This is due to the difficulty of the mathematical description and the considerable effortfulness of analysing and synthesising vibrating systems. The article shows the analysis of vibrating systems in which spring elements made of SMAs are used. The modelling and analysis method of vibrating systems is shown in the example of a vibrating system with a dynamic vibration absorber (DVA), which uses springs made of a shape memory alloy. The formulated mathematical model of a 2-DOF system with a controlled spring, mounted in DVA suspension, uses the viscoelastic model of the SMA spring. For the object, a control system was synthesised. Finally, model tests with and without a controller were carried out. The characteristics of the vibrations’ transmissibility functions for both systems were determined. It was shown that the developed DVA can tune to frequency excitation changes of up to ±10%. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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13 pages, 3302 KiB  
Article
Investigations of Effects of Intermetallic Compound on the Mechanical Properties and Shape Memory Effect of Ti–Au–Ta Biomaterials
by Wan-Ting Chiu, Kota Fuchiwaki, Akira Umise, Masaki Tahara, Tomonari Inamura and Hideki Hosoda
Materials 2021, 14(19), 5810; https://doi.org/10.3390/ma14195810 - 4 Oct 2021
Cited by 10 | Viewed by 1979
Abstract
Owing to the world population aging, biomedical materials, such as shape memory alloys (SMAs) have attracted much attention. The biocompatible Ti–Au–Ta SMAs, which also possess high X–ray contrast for the applications like guidewire utilized in surgery, were studied in this work. The alloys [...] Read more.
Owing to the world population aging, biomedical materials, such as shape memory alloys (SMAs) have attracted much attention. The biocompatible Ti–Au–Ta SMAs, which also possess high X–ray contrast for the applications like guidewire utilized in surgery, were studied in this work. The alloys were successfully prepared by physical metallurgy techniques and the phase constituents, microstructures, chemical compositions, shape memory effect (SME), and superelasticity (SE) of the Ti–Au–Ta SMAs were also examined. The functionalities, such as SME, were revealed by the introduction of the third element Ta; in addition, obvious improvements of the alloy performances of the ternary Ti–Au–Ta alloys were confirmed while compared with that of the binary Ti–Au alloy. The Ti3Au intermetallic compound was both found crystallographically and metallographically in the Ti–4 at.% Au–30 at.% Ta alloy. The strength of the alloy was promoted by the precipitates of the Ti3Au intermetallic compound. The effects of the Ti3Au precipitates on the mechanical properties, SME, and SE were also investigated in this work. Slight shape recovery was found in the Ti–4 at.% Au–20 at.% Ta alloy during unloading of an externally applied stress. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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15 pages, 7004 KiB  
Article
Strain Rate Effect upon Mechanical Behaviour of Hydrogen-Charged Cycled NiTi Shape Memory Alloy
by Fehmi Gamaoun
Materials 2021, 14(16), 4772; https://doi.org/10.3390/ma14164772 - 23 Aug 2021
Cited by 3 | Viewed by 2278
Abstract
The rate dependence of thermo-mechanical responses of superelastic NiTi with different imposed strain rates after cycling from 1 to 50 cycles under applied 10−5s−1, 10−4s−1 and 10−3s−1 strain rates, immersion for 3 h [...] Read more.
The rate dependence of thermo-mechanical responses of superelastic NiTi with different imposed strain rates after cycling from 1 to 50 cycles under applied 10−5s−1, 10−4s−1 and 10−3s−1 strain rates, immersion for 3 h and ageing has been investigated. The loaded and unloaded as-received NiTi alloy under an imposed strain of 7.1% have shown an increase in the residual deformation at zero stress with an increase in strain rates. It has been found that after 13 cycles and hydrogen charging, the amount of absorbed hydrogen (291 mass ppm) was sufficient to cause the embrittlement of the tensile loaded NiTi alloy with 10−5s−1. However, no premature fracture has been detected for the imposed strain rates of 10−4s−1 and 10−3s−1. Nevertheless, after 18 cycles and immersion for 3 h, the fracture has occurred in the plateau of the austenite martensite transformation during loading with 10−4s−1. Despite the higher quantity of absorbed hydrogen, the loaded specimen with a higher imposed strain rate of 10−3s−1 has kept its superelasticity behaviour, even after 20 cycles. We attribute such a behaviour to the interaction between the travelling distance during the growth of the martensitic domains while introducing the martensite phase and the amount of diffused hydrogen. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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13 pages, 3256 KiB  
Communication
On the Decrease in Transformation Stress in a Bicrystal Cu-Al-Mn Shape-Memory Alloy during Cyclic Compressive Deformation
by Tung-Huan Su, Nian-Hu Lu, Chih-Hsuan Chen and Chuin-Shan Chen
Materials 2021, 14(16), 4439; https://doi.org/10.3390/ma14164439 - 8 Aug 2021
Cited by 7 | Viewed by 2694
Abstract
The evolution of the inhomogeneous distribution of the transformation stress (σs) and strain fields with an increasing number of cycles in two differently orientated grains is investigated for the first time using a combined technique of digital image correlation and [...] Read more.
The evolution of the inhomogeneous distribution of the transformation stress (σs) and strain fields with an increasing number of cycles in two differently orientated grains is investigated for the first time using a combined technique of digital image correlation and data-driven identification. The theoretical transformation strains (εT) of these two grains with crystal orientations [5 3 26]β and [6 5 11]β along the loading direction are 10.1% and 7.1%, respectively. The grain with lower εT has a higher σs initially and a faster decrease in σs compared with the grain with higher εT. The results show that the grains with higher σs might trigger more dislocations during the martensite transformation, and thus result in greater residual strain and a larger decrease in σs during subsequent cycles. Grain boundary kinking in bicrystal induces an additional decrease in transformation stress. We conclude that a grain with crystal orientation that has high transformation strain and low transformation stress (with respect to loading direction) will exhibit stable transformation stress, and thus lead to higher functional performance in Cu-based shape memory alloys. Full article
(This article belongs to the Special Issue Mechanical Behavior of Shape Memory Alloys: 2022)
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