共查询到20条相似文献,搜索用时 15 毫秒
1.
《International Journal of Solids and Structures》2007,44(1):1-17
Dimensional analysis and the finite element method are applied in this paper to study spherical indentation of superelastic shape memory alloys. The scaling relationships derived from dimensional analysis bridge the indentation response and the mechanical properties of a superelastic shape memory alloy. Several key variables of a superelastic indentation curve are revealed and examined. We prove that the bifurcation force in a superelastic indentation curve only relies on the forward transformation stress and the elastic properties of the initial austenite; and the return force in a superelastic indentation curve only relies on the reverse transformation stress and the elastic properties of the initial austenite. Furthermore, the dimensionless functions to determine the bifurcation force and the return force are proved to be identical. These results not only enhance our understanding of spherical indentation of superelastic shape memory alloys, but also provide the theoretical basis for developing a practicable method to calibrate the mechanical properties of a superelastic material from the spherical indentation test. 相似文献
2.
This paper describes an expeirmental investigation which was carried out to determine the fatigue life of two aluminum alloys (2024-T3 and 6061-T6). They were subjected to both constant-strain-amplitude sinusoidal and narrow-band random-strain-amplitude fatigue loadings. The fatigue-life values obtained from the narrow-band random testing were compared with theoretical predictions based on Miner's linear accumulation of damage hypothesis. Cantilever-beam-test specimens fabricated from the aluminum alloys were subjected to either a constant-strain-amplitude sinusoidal or a narrow-band random base excitation by means of an electromagnetic vibrations exciter. It was found that the ε-N curves for both alloys could be approximated by three straight-line segments in the low-, intermediate- and high-cycle fatigue-life ranges. Miner's hypothesis was used to predict the narrow-band random fatigue lives of materials with this type of ε-N behavior. These fatigue-life predictions were found to consistently overestimate the acutal fatigue lives by a factor of 2 or 3. However, the shape of the predicted fatigue-life curves and the high-cycle fatigue behavior of both materials were found to be in good agreement with the experimental results. 相似文献
3.
形状记忆合金热力学行为的模拟 总被引:3,自引:1,他引:3
基于塑性流动法则和马氏体相变动力学 ,引入马氏体体积分数和相变应力间的关系 ,对形状记忆合金的热力学行为进行了模拟 ,算例表明本文提出的形状记忆合金本构模型与实验结果比较吻合 ,且实施起来简单易行 ;最后还用该本构模型进行了有限元分析 相似文献
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Michaël Peigney 《Journal of the mechanics and physics of solids》2008,56(2):360-375
New upper bounds are proposed for a generic problem of geometric compatibility, which covers the problem of bounding the effective recoverable strains in composite shape memory alloys (SMAs), such as polycrystalline SMAs or rigidly reinforced SMAs. Both the finite deformation and infinitesimal strain frameworks are considered. The methodology employed is a generalization of a homogenization approach introduced by Milton and Serkov [2000. Bounding the current in nonlinear conducting composites. J. Mech. Phys. Solids 48, 1295-1324] for nonlinear composites in infinitesimal strains. Some analytical and numerical examples are given to illustrate the method. 相似文献
6.
《International Journal of Solids and Structures》2014,51(23-24):4015-4025
In this paper, a gradient-enhanced 3-D phenomenological model for shape memory alloys using the non-local theory is developed based on a 1-D constitutive model. The method utilizes a non-local field variable in its constitutive framework with an implicit gradient formulation in order to achieve results independent of the finite element discretization. An efficient numerical approach to implement the non-local gradient-enhanced model in finite element codes is proposed. The model is used to simulate stress drop at the onset of transformation, and its performance is evaluated using different experimental data. The potential of the presented numerical approach for behavior of shape memory alloys in eliminating mesh-dependent simulations is validated by conducting various localization problems. The numerical results show that the developed model can simulate the observed unstable behaviors such as stress drop and deviation of local strain from global strain during nucleation and propagation of martensitic phase. 相似文献
7.
Superelastic polycrystalline NiTi shape memory alloys under tensile loading accompany the strain localization and propagation phenomena. Experiments showed that the number of moving phase fronts and the mechanical behavior are very sensitive to the loading rate due to the release/absorption of latent heat and the material’s inherent temperature sensitivity of the transformation stress. In this paper, the moving heat source method based on the heat diffusion equation is used to study the temperature evolution of one-dimensional superelastic NiTi specimen under different loading rates and boundary conditions with moving heat sources or a uniform heat source. Comparisons of temperature variations with different boundary conditions show that the heat exchange at the boundaries plays a major role in the nonuniform temperature profile that directly relates to the localized deformation. Analytical relation between the front temperature of a single phase front, the inherent Clausius–Clapeyron relation (sensitivity of the material’s transformation stress with temperature), heat transfer boundary conditions and the loading rate is established to analyze the nucleation of new phase fronts. Finally, the rate-dependent stress hysteresis is also simply discussed by using the results of temperature analyses. 相似文献
8.
Martensitic transformations (MTs) are the key phenomena responsible for the remarkable properties of Shape Memory Alloys (SMAs). Recent Density Functional Theory (DFT) electronic structure calculations have revealed that the austenite structure of many SMAs is a saddle-point of the material's potential energy landscape. Correspondingly, the austenite is unstable and thus unobservable at zero temperature. Thus, the observable high temperature austenite structure in many SMAs is entropically stabilized by nonlinear dynamic effects. 相似文献
9.
A NEW MODEL OF SHAPE MEMORY ALLOYS 总被引:1,自引:0,他引:1
A new constitutive model of shape memory alloys ( SMAs) based on Tanaka ' s martensite fraction exponential expression is produced. This new model can present recoverable shape memory strain during different phase transformation, and reflect the action of martensite reorientation . Also it can overcome the defect of Tanaka ' s Model when the SMAs ' microstructure is fully martensite . The model is very simple and suitable for using , and the correct behavior of the model is proved by test. 相似文献
10.
In this study the mesoscopic behavior of porous shape memory alloys has been simulated with particular attention to the mechanical response under cyclic loading conditions. A recently developed constitutive law, accounting for full martensite reorientation as well as phase transformation, was implemented into the commercial finite element code ABAQUS. Due to stress concentrations in a porous microstructure, the constitutive law was enhanced to account for the development of permanent inelasticity in the shape memory matrix. With this simulation method, the complex interaction between porosity, local phase transformation and macroscale response has been evaluated. The results have implications for use of porous SMAs in biomedical and structural applications. 相似文献
11.
This paper deals with the large deflection and stability behaviour of inextensible spherical air-supported membranes subjected to an accumulating ponding fluid. It is assumed that ponding fluid is available to fill an initial axi-symmetric deformation around the apex and that due to such accumulation deflections increase until under certain conditions collapse of the structure occurs.The problem is reduced to a set of differential equations which are solved numerically to determine the parameters defining the deflected wrinkled shape of the membrane. A simple expression for use in design of such structures is obtained and the results presented in non-dimensional graphic form. 相似文献
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In this work, a general inelastic framework for the derivation of general three-dimensional thermomechanical constitutive laws for materials undergoing phase transformations is proposed. The proposed framework is based on the generalized plasticity theory and on some basic elements from the theory of continuum damage mechanics. More specifically, a new elaborate formulation of generalized plasticity theory capable of accommodating the multiple and interacting loading mechanisms, which occur during the phase transformations, is developed. Furthermore, the stiffness variations occurring during phase transformations are taken into account by the proposed framework. For this purpose, the free energy is decomposed into elastic and inelastic parts, not in a conventional way, but in one which resembles the elastic-damage cases. Also, a rate-dependent version of the theory is provided. The concepts presented are applied for the derivation of a three-dimensional thermomechanical constitutive model for Shape Memory Alloy materials. Numerical simulations to show qualitatively the ability of the model to capture the behavior of the shape memory alloys are also presented. Furthermore, the model has been fitted to actual experimental results from the literature. 相似文献
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Modeling the dynamic behavior of shape memory alloys 总被引:4,自引:0,他引:4
Stefan Seelecke 《International Journal of Non》2002,37(8):837-1374
The paper studies the single degree of freedom vibration of a rigid mass suspended by a thin-walled shape memory alloy tube under torsional loading. The behavior is analyzed for the cases of quasiplasticity (low temperatures) and pseudoelasticity (high temperatures) on the basis of an improved version of the Müller–Achenbach model. To illustrate the strong hysteresis-induced damping capacity and the non-linear vibration characteristics, both, free and forced vibrations are considered in the first part of the paper. This is done on the basis of an isothermal version of the model, while the second part of the paper focuses on the effect of non-constant temperature caused by the rate-dependent release and absorption of latent heats. 相似文献
16.
Based on the microstructure-based constitutive model established in Part I, a detailed numerical investigation on the role
of each microstructure parameter in the kinematical and kinetic evolution of polycrystalline SMA under axisymmetrical tension
loading is performed. Some macroscopic constitutive features of stress-induced martensite transformation are discussed.
The subject supported by the Research Grant Committee (RGC) of Hong Kong SAR, the National Natural Science Foundation of China
and the Provincial Natural Science Foundation of Jiangxi Province of China 相似文献
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H. Tobushi H. Iwanaga K. Tanaka T. Hori T. Sawada 《Continuum Mechanics and Thermodynamics》1991,3(2):79-93
Experiments with cyclic loading-unloading and experiments with heatingcooling under constant stress of TiNi shape memory alloys were carried out. This paper shows that, during the thermomechanical cycles, the transformation stresses of the martensitic transformation and the reverse transformation decrease, but the transformation temperatures increase. The cyclic recovery strain is represented by a relation between the heating temperature, the cooling temperature, the transformation lines in the stress-temperature plane and the transformation strain. 相似文献
19.
Sergio A. Oliveira Marcelo A. Savi Alexander L. Kalamkarov 《Archive of Applied Mechanics (Ingenieur Archiv)》2010,80(10):1163-1175
Shape memory alloys (SMAs) are materials that, among other characteristics, have the ability to present high deformation levels
when subjected to mechanical loading, returning to their original form after a temperature change. Literature presents numerous
constitutive models that describe the phenomenological features of the thermomechanical behavior of SMAs. The present paper
introduces a novel three-dimensional constitutive model that describes the martensitic phase transformations within the scope
of standard generalized materials. The model is capable of describing the main features of the thermomechanical behavior of
SMAs by considering four macroscopic phases associated with austenitic phase and three variants of martensite. A numerical
procedure is proposed to deal with the nonlinearities of the model. Numerical simulations are carried out dealing with uniaxial
and multiaxial single-point tests showing the capability of the introduced model to describe the general behavior of SMAs.
Specifically, uniaxial tests show pseudoelasticity, shape memory effect, phase transformation due to temperature change and
internal subloops due to incomplete phase transformations. Concerning multiaxial tests, the pure shear stress and hydrostatic
tests are discussed showing qualitatively coherent results. Moreover, other tensile–shear tests are conducted modeling the
general three-dimensional behavior of SMAs. It is shown that the multiaxial results are qualitative coherent with the related
data presented in the literature. 相似文献
20.
Reza Mehrabi Mahmoud Kadkhodaei Mohammad Elahinia 《International Journal of Solids and Structures》2014
In microplane theory, it is assumed that a macroscopic stress tensor is projected to the microplane stresses. It is also assumed that 1D constitutive laws are defined for associated stress and strain components on all microplanes passing through a material point. The macroscopic strain tensor is obtained by strain integration on microplanes of all orientations at a point by using a homogenization process. Traditionally, microplane formulation has been based on the Volumetric–Deviatoric–Tangential split and macroscopic strain tensor was derived using the principle of complementary virtual work. It has been shown that this formulation could violate the second law of thermodynamics in some loading conditions. The present paper focuses on modeling of shape memory alloys using microplane formulation in a thermodynamically-consistent framework. To this end, a free energy potential is defined at the microplane level. Integrating this potential over all orientations provides the macroscopic free energy. Based on this free energy, a new formulation based on Volumetric–Deviatoric split is proposed. This formulation in a thermodynamic-consistent framework captures the behavior of shape memory alloys. Using experimental results for various loading conditions, the validity of the model has been verified. 相似文献