共查询到7条相似文献,搜索用时 2 毫秒
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A constitutive modeling approach for shape memory alloy (SMA) wire by taking into account the microstructural phase inhomogeneity
and the associated solid–solid phase transformation kinetics is reported in this paper. The approach is applicable to general
thermomechanical loading. Characterization of various scales in the non-local rate sensitive kinetics is the main focus of
this paper. Design of SMA materials and actuators not only involve an optimal exploitation of the hysteresis loops during
loading–unloading, but also accounts for fatigue and training cycle identifications. For a successful design of SMA integrated
actuator systems, it is essential to include the microstructural inhomogeneity effects and the loading rate dependence of
the martensitic evolution, since these factors play predominant role in fatigue. In the proposed formulation, the evolution
of new phase is assumed according to Weibull distribution. Fourier transformation and finite difference methods are applied
to arrive at the analytical form of two important scaling parameters. The ratio of these scaling parameters is of the order
of 106 for stress-free temperature-induced transformation and 104 for stress-induced transformation. These scaling parameters are used in order to study the effect of microstructural variation
on the thermo-mechanical force and interface driving force. It is observed that the interface driving force is significant
during the evolution. Increase in the slopes of the transformation start and end regions in the stress–strain hysteresis loop
is observed for mechanical loading with higher rates.
相似文献
3.
P. Feng 《Journal of the mechanics and physics of solids》2006,54(8):1568-1603
This paper reports the experimental results on macroscopic deformation instability and domain morphology evolution during stress-induced austenite → martensite (A→M) phase transformation in superelastic NiTi polycrystalline shape memory alloy microtubes. High-speed data and image acquisition techniques were used to investigate the dynamic and quasi-static events which took place in a displacement-controlled quasi-static tensile loading/unloading process of the tube. These events include dynamic formation, self-merging, topology transition, convoluted front motion and front instability of a macroscopic deformation domain. The reported phenomena brought up several fundamental issues regarding the roles of macroscopic domain wall energy and kinetics as well as their interplay with the bulk strain energy of the tube in the observed morphology instability and pattern evolution under a mechanical force. These issues are believed to be essential elements in the theoretical modeling of macroscopic deformation patterns in polycrystals and need systematic examination in the future. 相似文献
4.
《International Journal of Solids and Structures》2014,51(25-26):4386-4405
In this paper, a crystal plasticity based constitutive model (Yu et al., 2013) is extended to describe the rate-dependent cyclic deformation of super-elastic NiTi shape memory alloy by considering the internal heat production. Two sources of internal heat productions are included in the proposed model, i.e., the mechanical dissipations of inelastic deformation and the transformation latent heat in the NiTi shape memory alloy. With an assumption of uniform temperature field in the alloy specimen, a simplified evolution law of temperature field is obtained by the first law of thermodynamics and the heat boundary conditions. An explicit scale-transition rule is adopted to extend the proposed single crystal model to the polycrystalline version. The capability of the extended polycrystalline model to describe the rate-dependent cyclic deformation of super-elastic NiTi shape memory alloy is verified by comparing the predictions with the corresponding experimental ones. The comparison demonstrates that the proposed constitutive model considering the internal heat production predicts the rate-dependent cyclic deformation of super-elastic NiTi shape memory alloy fairly well. 相似文献
5.
L.Catherine Brinson Ina Schmidt 《Journal of the mechanics and physics of solids》2004,52(7):1549-1571
An experimental investigation of the micro and macromechanical transformation behavior of polycrystalline NiTi shape memory alloys was undertaken. Special attention was paid to macroscopic banding, variant microstructure, effects of cyclic loading, strain rate and temperature effects. Use of an interference filter on the microscope enabled observation of grain boundaries and martensitic plate formation and growth without recourse to etching or other chemical surface preparation. Key results of the experiments on the NiTi include observation of localized plastic deformation after only a few cycles, excellent temperature and stress relaxation correlation, a refined definition of “full transformation” for polycrystalline materials, and strain rate dependent effects. Several of these findings have critical implications for understanding and modeling of shape memory alloy behavior. 相似文献
6.
泡沫铝铜合金静态压缩力学行为和吸能性能的实验研究 总被引:1,自引:0,他引:1
通过静态压缩实验研究一种新型闭孔泡沫铝材料泡沫铝铜合金的静态压缩力学行为和吸能性能。对实验得到的一定密度范围内的材料的弹性模量E和平台应力pl关于相对密度进行曲线拟合,发现将Gibson等给出的开孔泡沫理论公式中的幂次常数修正为由实验确定的常数,可以给出一定密度范围的闭孔泡沫铝铜合金材料的弹性模量和平台应力与相对密度之间关系的一个较好的估计。采用比能-应力或比能-应变曲线,可以对不同密度的泡沫铝铜合金材料的吸能情况进行较为直观的比较和分析。该曲线对工程设计具有较好的指导意义。 相似文献
7.
We study theoretically and computationally the incompressible, non-conducting, micropolar, biomagnetic (blood) flow and heat
transfer through a two-dimensional square porous medium in an (x,y) coordinate system, bound by impermeable walls. The magnetic field acting on the fluid is generated by an electrical current
flowing normal to the x–y plane, at a distance l beneath the base side of the square. The flow regime is affected by the magnetization B
0 and a linear relation is used to define the relationship between magnetization and magnetic field intensity. The steady governing
equations for x-direction translational (linear) momentum, y-direction translational (linear) momentum, angular momentum (micro-rotation) and energy (heat) conservation are presented.
The energy equation incorporates a special term designating the thermal power per unit volume due to the magnetocaloric effect.
The governing equations are non-dimensionalized into a dimensionless (ξ,η) coordinate system using a set of similarity transformations. The resulting two point boundary value problem is shown to
be represented by five dependent non-dimensional variables, f
ξ
(velocity), f
η
(velocity), g (micro-rotation), E (magnetic field intensity) and θ (temperature) with appropriate boundary conditions at the walls. The thermophysical parameters controlling the flow are the
micropolar parameter (R), biomagnetic parameter (N
H
), Darcy number (Da), Forchheimer (Fs), magnetic field strength parameter (Mn), Eckert number (Ec) and Prandtl number (Pr). Numerical solutions are obtained using the finite element method and also the finite difference method for Ec=2.476×10−6 and Prandtl number Pr=20, which represent realistic biomagnetic hemodynamic and heat transfer scenarios. Temperatures are shown to be considerably
increased with Mn values but depressed by a rise in biomagnetic parameter (N
H
) and also a rise in micropolarity (R). Translational velocity components are found to decrease substantially with micropolarity (R), a trend consistent with Newtonian blood flows. Micro-rotation values are shown to increase considerably with a rise in
R values but are reduced with a rise in biomagnetic parameter (N
H
). Both translational velocities are boosted with a rise in Darcy number as is micro-rotation. Forchheimer number is also
shown to decrease translational velocities but increase micro-rotation. Excellent agreement is demonstrated between both numerical
solutions. The mathematical model finds applications in blood flow control devices, hemodynamics in porous biomaterials and
also biomagnetic flows in highly perfused skeletal tissue.
Dedicated to Professor Y.C. Fung (1919-), Emeritus Professor of Biomechanics, Bioengineering Department, University of California
at San Diego, USA for his seminal contributions to biomechanics and physiological fluid mechanics over four decades and his
excellent encouragement to the authors, in particular OAB, with computational biofluid dynamics research. 相似文献