scholarly journals Functional Behavior of Pseudoelastic NiTi Alloy Under Variable Amplitude Loading

2020 ◽  
Vol 14 (3) ◽  
pp. 154-160
Author(s):  
Volodymyr Iasnii ◽  
Petro Yasniy ◽  
Yuri Lapusta ◽  
Oleg Yasniy ◽  
Oleksandr Dyvdyk
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Residual Strain ◽  
Niti Alloy ◽  
Strain Curve ◽  
Niti Shape Memory Alloy ◽  
Dissipation Energy ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Lower Amplitude

Abstract Cyclic loading of superelastic NiTi shape memory alloy (SMA) causes forward and reverse austenite–martensіte transformations, and also increases the volume of stabilized martensite. This appears in the change of stress-strain curve form, the decrease of dissipation energy, and increase of residual strain, that is, named transformation ratcheting. In real structures, the SMA components in most cases are under the action of variable amplitude loading. Therefore, it is obvious that the loading history will influence the functional fatigue. In the present work, the effect of stress ratio on the functional properties of superelastic NiTi shape memory alloy under variable amplitude loading sequence with two blocks was investigated. The studies were carried out under the uniaxial tension of cylindrical specimens under load-full unload and load-part unload. The change of residual strain, strain range, dissipation, and cumulative dissipation energy density of NiTi alloy related to load sequences are discussed. Under both stress ratios, the residual strain in NiTi alloy is increased depending on the number of loading cycles on the high loading block that is similar to the tests at constant stress or strain amplitude. An unusual effect of NiTi alloy residual strain reduction with the number cycles is found at a lower block loading. There was revealed the effect of residual strain reduction of NiTi alloy on the number of loading cycles on the lower amplitude block. The amount of decrement of the residual strain during a low loading block is approximately equal to the reversible part of the residual strain due to the stabilized martensite. The decrease of the residual strain during the low loading block is approximately equal to the reversible part of residual strain due to the stabilized martensite. A good correlation of the effective Young’s modulus for both load blocks with residual strain, which is a measure of the volume of irreversible martensite, is observed.

scholarly journals Key Properties of a Bioactive Ag-SiO2/TiO2 Coating on NiTi Shape Memory Alloy as Necessary at the Development of a New Class of Biomedical Materials

2021 ◽  
Vol 22 (2) ◽  
pp. 507
Author(s):  
Mateusz Dulski ◽  
Robert Gawecki ◽  
Sławomir Sułowicz ◽  
Michal Cichomski ◽  
Alicja Kazek-Kęsik ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Dermal Fibroblast ◽  
Niti Alloy ◽  
Bacterial Biofilm ◽  
Niti Shape Memory Alloy ◽  
Normal Human Dermal Fibroblast ◽  
Water Contact ◽  
Nano Coating

Recent years have seen the dynamic development of methods for functionalizing the surface of implants using biomaterials that can mimic the physical and mechanical nature of native tissue, prevent the formation of bacterial biofilm, promote osteoconduction, and have the ability to sustain cell proliferation. One of the concepts for achieving this goal, which is presented in this work, is to functionalize the surface of NiTi shape memory alloy by an atypical glass-like nanocomposite that consists of SiO2-TiO2 with silver nanoparticles. However, determining the potential medical uses of bio(nano)coating prepared in this way requires an analysis of its surface roughness, tribology, or wettability, especially in the context of the commonly used reference coat-forming hydroxyapatite (HAp). According to our results, the surface roughness ranged between (112 ± 3) nm (Ag-SiO2)—(141 ± 5) nm (HAp), the water contact angle was in the range (74.8 ± 1.6)° (Ag-SiO2)—(70.6 ± 1.2)° (HAp), while the surface free energy was in the range of 45.4 mJ/m2 (Ag-SiO2)—46.8 mJ/m2 (HAp). The adhesive force and friction coefficient were determined to be 1.04 (Ag-SiO2)—1.14 (HAp) and 0.247 ± 0.012 (Ag-SiO2) and 0.397 ± 0.034 (HAp), respectively. The chemical data showed that the release of the metal, mainly Ni from the covered NiTi substrate or Ag from Ag-SiO2 coating had a negligible effect. It was revealed that the NiTi alloy that was coated with Ag-SiO2 did not favor the formation of E. coli or S. aureus biofilm compared to the HAp-coated alloy. Moreover, both approaches to surface functionalization indicated good viability of the normal human dermal fibroblast and osteoblast cells and confirmed the high osteoconductive features of the biomaterial. The similarities of both types of coat-forming materials indicate an excellent potential of the silver-silica composite as a new material for the functionalization of the surface of a biomaterial and the development of a new type of functionalized implants.

Rate-Dependent Damping Capacity of NiTi Shape Memory Alloy

2011 ◽  
Vol 172-174 ◽  
pp. 37-42 ◽  
Author(s):  
Yong Jun He ◽  
Qing Ping Sun
Keyword(s):  
Shape Memory Alloy ◽  
Strain Rate ◽  
Shape Memory ◽  
Strain Curve ◽  
Tensile Loading ◽  
Niti Shape Memory Alloy ◽  
Damping Capacity ◽  
Environmental Condition ◽  
Mechanical Coupling ◽  
Rate Dependent

High damping capacity is one of the prominent properties of NiTi shape memory alloy (SMA), having applications in many engineering devices to reduce unwanted vibrations. Recent experiments demonstrated that, the hysteresis loop of the stress-strain curve of a NiTi strip/wire under a tensile loading-unloading cycle changed non-monotonically with the loading rate, i.e., a maximum damping capacity was obtained at an intermediate strain rate (ε.critical). This rate dependence is due to the coupling between the temperature dependence of material’s transformation stresses, latent-heat release/absorption in the forward/reverse phase transition and the associated heat exchange between the specimen and the environment. In this paper, a simple analytical model was developed to quantify these thermo-mechanical coupling effects on the damping capacity of the NiTi strips/wires under the tensile loading-unloading cycle. We found that, besides the material thermal/mechanical properties and specimen geometry, environmental condition also affects the damping capacity; and the critical strain rate ε.criticalfor achieving a maximum damping capacity can be changed by varying the environmental condition. The theoretical predictions agree quantitatively with the experiments.

EFFECTS OF PARTICLE SIZE AND SINTERING TEMPERATURE ON SUPERELASTICITY BEHAVIOR OF NiTi SHAPE MEMORY ALLOY USING NANOINDENTATION

2021 ◽  
pp. 2150024
Author(s):  
C. VELMURUGAN ◽  
V. SENTHILKUMAR
Keyword(s):  
Particle Size ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Sintering Temperature ◽  
Niti Alloy ◽  
Indentation Load ◽  
Niti Shape Memory Alloy ◽  
Recovery Ratio ◽  
Work Recovery ◽  
Niti Sma

The present study investigates the superelasticity properties of spark plasma sintered (SPS) nickel titanium shape memory alloy (NiTi SMA) with the influence of sintering temperature and particle size. The nanoindentation is conducted on the surface of the NiTi SMA at various loads such as 100, 300 and 500[Formula: see text]mN. The nanoindentation technique determines the quantitative results of elasto-plastic properties such as depth recovery in the form of superelasticity, stiffness, hardness and work recovery ratio from load–depth ([Formula: see text]–[Formula: see text]) data during loading and unloading of the indenter. Experimental findings show that the depth and work recovery ratio increases with the decrease of indentation load and particle size. In contrast, increasing the sintering temperature exhibited a better depth and work recovery due to the removal of pores which could enhance the reverse transformation. The contact stiffness is influenced by [Formula: see text] which leads to attain a maximum stiffness at the highest load (500[Formula: see text]mN) and particle size (45[Formula: see text][Formula: see text]m) along with the lowest sintering temperature (700∘C). NiTi alloy exhibited a maximum hardness of 9.46[Formula: see text]GPa when subjected to indent at the lowest load and particle size sintered at 800∘C. The present study reveals a better superelastic behavior in NiTi SMA by reducing the particle size and indentation load associated with the enhancement of sintering temperature.

Corrosion Kinetics of Laser Treated NiTi Shape Memory Alloy Biomaterials

1996 ◽  
Vol 459 ◽  
Author(s):  
F. Villermaux ◽  
I. Nakatsugawa ◽  
M. Tabrizian ◽  
D. L. Piron ◽  
M. Meunier ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Laser Treatment ◽  
Niti Alloy ◽  
Niti Shape Memory Alloy ◽  
Surgical Implants ◽  
Hank’S Solution ◽  
Kinetics Of ◽  
Human Fluids

ABSTRACTNiTi shape memory alloy presents interesting mechanical properties as surgical implants. However, due to its high amount of Ni which may dissolve and release toxic ions in human fluids, the medical use of this material is a great concern. We have developed a laser treatment which modifies the oxide layer and enhances uniform and localised corrosion resistance of NiTi alloy.In this paper we further analysed the effect of this treatment with potentiostatic and AC impedance measurements in physiological Hank's solution. We conclude that the laser treatment creates a stable passive film which results in improved corrosion resistance of this alloy.

scholarly journals Experimental Analysis of NiTi Alloy during Strain-Controlled Low-Cycle Fatigue

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4455
Author(s):  
Pedro Cunha Lima ◽  
Patrícia Freitas Rodrigues ◽  
Ana Sofia Ramos ◽  
José D. M. da Costa ◽  
Francisco Manuel Braz Fernandes ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Low Cycle Fatigue ◽  
Niti Alloy ◽  
Niti Shape Memory Alloy ◽  
Cycle Fatigue ◽  
Maximum Deformation ◽  
Transmission Electron ◽  
Before And After

The interaction between the stress-induced martensitic transformation and resistivity behavior of superelastic NiTi shape memory alloy (SMA) was studied. Strain-controlled low-cycle fatigue up to 6% was monitored by in situ electrical resistivity measurements. The experimental results show that a great motion of martensite fronts results in a significant accumulation of defects, as evidenced by transmission electron microscopy (TEM), before and after the tensile cycles. This gives rise to an overall increase of the resistivity values up to the maximum deformation. Therefore, the research suggests that shape memory alloy wire has great potential as a stress sensor inside bulk materials.

A uniaxial constitutive model for NiTi shape memory alloy bars considering the effect of residual strain

2019 ◽  
Vol 30 (8) ◽  
pp. 1163-1177
Author(s):  
Canjun Li ◽  
Zhen Zhou ◽  
Yazhi Zhu
Keyword(s):  
Shape Memory Alloy ◽  
Constitutive Model ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Residual Strain ◽  
Hysteretic Behavior ◽  
Niti Shape Memory Alloy ◽  
Strain Effect ◽  
Proposed Model ◽  
Residual Strains

Super-elastic shape memory alloys are widely used in structural engineering fields due to their encouraging super-elasticity and energy dissipation capability. Large-size shape memory alloy bars often present significant residual strains after unloading, which emphasizes the necessity of developing a residual strain effect–coupled constitutive model to predict well the performance of shape memory alloy–based structures. First, this article experimentally studies the hysteretic behavior of NiTi shape memory alloy bars under quasi-static loading conditions and investigates the effects of cyclic numbers and strain amplitudes on residual strain. Second, a concept of cumulative transformation strain is preliminarily introduced into a phenomenological Lagoudas model. A uniaxial constitutive model for shape memory alloy bars including the residual strain is proposed. By using OpenSees platform, numerical simulations of shape memory alloy bars are conducted—the results of which indicate that the proposed model can accurately capture the hysteretic behavior of shape memory alloys. The predicted residual strains show a good agreement to experimental results, which demonstrates the desirable efficiency of the proposed model.

Damping Characteristics of Biomedical Porous NiTi Shape Memory Alloy

2010 ◽  
Vol 97-101 ◽  
pp. 1083-1086
Author(s):  
Hai Chang Jiang ◽  
Shu Wei Liu ◽  
Xiu Yan Li ◽  
Li Jian Rong
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Strain Amplitude ◽  
Niti Alloy ◽  
Small Strain ◽  
Cooling Curve ◽  
Niti Shape Memory Alloy ◽  
Internal Friction Peak ◽  
Porous Niti ◽  
Tan Δ

One internal friction peak associated with the B2↔B19’ transformation appears on the cooling curve of porous NiTi shape memory alloy and the dense NiTi alloy shows the maximum peak. The tan δ value increased with the increasing of strain amplitude and the decreasing of frequency. Tan δ value of porous alloy mainly comes from the energy absorbing of the matrix at the small strain amplitude, however, if the strain amplitude is large, the tan δ value comes from the energy consumption that overcomes the friction between folds and the plastic contribution.

Stress Analysis and Sealing Performance of Pipe Flange Connections With NiTi Shape Memory Alloy Gasket

2007 ◽  
Author(s):  
Yoshio Takagi ◽  
Teruhisa Tatsuoka ◽  
Naoki Kawasaki ◽  
Toshiyuki Sawa
Keyword(s):  
Thermal Expansion ◽  
Elastic Modulus ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Niti Alloy ◽  
Fem Analysis ◽  
Effect Of Temperature ◽  
Niti Shape Memory Alloy ◽  
3D Fem ◽  
Sealing Performance

Due to the long-term durability and the excellent resistance to aging degradation, metal gaskets are expected to give a longer life compared to conventional polymer gaskets. However, the nature of high elastic modulus of the metal reduces the sealing performance at interface. Nickel-Titanium shape memory alloy (NiTi alloy) shows an excellent elasticity and is expected to be applicable as a gasket. The authors have already evaluated the sealing performance of the pipe flange connections with NiTi gaskets. The results revealed that NiTi alloy showed a superior sealing performance to the conventional aluminum gasket. However, the sealing performance of the connection depended on the ambient temperature due to the change in physical properties like the elastic modulus and the thermal expansion coefficient of NiTi alloy. In this paper, the stress distribution was analyzed with 3D FEM and the effect of temperature in the sealing performance was evaluated. In the analysis, the particular element code was adopted for analyzing the deformation behavior of NiTi alloy gasket. The elements worked well in the analysis and helped to evaluate the sealing behavior of the flange connections. According to the analysis, the gasket contact stress decreased as increasing the temperature because of the lower thermal expansion of NiTi alloy than that of austenitic stainless steel of which the flange and bolt material were made. On the other hand, the FEM analysis suggested that the increment of elastic modulus of NiTi alloy compensate the reduction of compression strain of the gasket due to the difference of thermal expansion between gasket and flange. As a result of the ex-experimental study and FE analysis, the recommendable assembling process for NiTi alloy gasket was proposed.

Study on Measurement of Group Velocity of Lamb Waves in Shape Memory Alloy Sheets

2014 ◽  
Vol 1065-1069 ◽  
pp. 2021-2024
Author(s):  
Kai Sheng Wang ◽  
Wei Chun Zhang
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Group Velocity ◽  
Lamb Waves ◽  
Niti Alloy ◽  
Effective Means ◽  
Niti Shape Memory Alloy ◽  
Time Frequency ◽  
Different Temperatures

This paper describes the nondestructive evaluation of microstructure using laser-excited Lamb waves to detect the phase transformation in NiTi shape memory alloy sheets. Lamb waves were applied in the NiTi sheet using a pulse laser beam. Piezoelectricity transducers were used to receive the Lamb waves, the group velocities of which were measured using a time-frequency analysis method at different temperatures. Results show that a marked variation in the group velocity occurs during the phase transformation in the NiTi alloy. The dependence of group velocity on temperature provides a effective means of inspecting microstructure transformation in NiTi alloys.

Application of EIS to Study the Corrosion Resistance of Passivated NiTi Shape Memory Alloy in Simulated Body Fluid

2011 ◽  
Vol 183 ◽  
pp. 57-64 ◽  
Author(s):  
Marlena Freitag ◽  
B. Łosiewicz ◽  
Tomasz Goryczka ◽  
Józef Lelątko
Keyword(s):  
Corrosion Resistance ◽  
Shape Memory Alloy ◽  
Simulated Body Fluid ◽  
Shape Memory ◽  
Pitting Corrosion ◽  
Body Fluid ◽  
Niti Alloy ◽  
Amorphous State ◽  
Open Circuit ◽  
Niti Shape Memory Alloy

The NiTi shape memory alloy passivated for 90 min by autoclaving has been studied towards corrosion performance in the Tyrode’s simulated body fluid using open circuit potential and EIS measurements. The surface morphology and thickness of the oxide layer was determined by XRR. The HREM was used to observe the cross-section of the thin foil and to confirm the amorphous state of the TiO2 layer and its thickness. Electrochemical measurements revealed a good corrosion resistance at the beginning of long-term (20 days) immersion. It was found that with the increase of immersion time, the corrosion resistance of the surface deteriorated after nearly 1 day of immersion due to occurence of pitting corrosion. The EIS method was used to detailed study on the electrolyte | passive layer interfacial properties. Equivalent electrical circuit for the pitting corrosion on the passivated NiTi alloy has been applied.

Sign in / Sign up

Export Citation Format

Share Document