Thermal-induced interfacial behavior of a thin one-dimensional hexagonal quasicrystal film

In this paper,we investigate the interfacial behavior of a thin one-dimensional(1D)hexagonal quasicrystal(QC)film bonded on an elastic substrate subjected to a mismatch strain due to thermal variation.The contact interface is assumed to be nonslipping,with both perfectly bonded and debonded boundary conditions.The Fourier transform technique is adopted to establish the integral equations in terms of interfacial shear stress,which are solved as a linear algebraic system by approximating the unknown phonon interfacial shear stress via the series expansion of the Chebyshev polynomials.The expressions are explicitly obtained for the phonon interfacial shear stress,internal normal stress,and stress intensity factors(SIFs).Finally,based on numerical calculations,we briefly discuss the effects of the material mismatch,the geometry of the QC film,and the debonded length and location on stresses and SIFs.

A coupled Legendre-Laguerre polynomial method with analytical integration for the Rayleigh waves in a quasicrystal layered half-space with an imperfect interface

The Laguerre polynomial method has been successfully used to investigate the dynamic responses of a half-space.However,it fails to obtain the correct stress at the interfaces in a layered half-space,especially when there are significant differences in material properties.Therefore,a coupled Legendre-Laguerre polynomial method with analytical integration is proposed.The Rayleigh waves in a one-dimensional(1D)hexagonal quasicrystal(QC)layered half-space with an imperfect interface are investigated.The correctness is validated by comparison with available results.Its computation efficiency is analyzed.The dispersion curves of the phase velocity,displacement distributions,and stress distributions are illustrated.The effects of the phonon-phason coupling and imperfect interface coefficients on the wave characteristics are investigated.Some novel findings reveal that the proposed method is highly efficient for addressing the Rayleigh waves in a QC layered half-space.It can save over 99%of the computation time.This method can be expanded to investigate waves in various layered half-spaces,including earth-layered media and surface acoustic wave(SAW)devices.

Study on the effective elastic performance of composites containing decagonal symmetric two-dimensional quasicrystal coatings

On account of the Mori-Tanaka approach,the effective elastic performance of composites containing decagonal symmetric two-dimensional(2D)quasicrystal(QC)coatings is studied.Explicit expressions for the effective elastic constants of rare-earth QC reinforced magnesium-based composites are provided.Detailed discussion is presented on the effects of the volume fraction of the inclusions,the aspect ratio of the inclusions,the coating thickness,and the coating material parameters on the effective elastic constants of the composites.The results indicate that considering the coating increases the effective elastic constants of the composites to some extent.

Analytic solution of quasicrystal microsphere considering the thermoelectric effect and surface effect in the elastic matrix

The incorporation of the quasicrystalline phase into the metal matrix offers a wide range of potential applications in particle-reinforced metal-matrix composites.The analytic solution of the piezoelectric quasicrystal(QC)microsphere considering the thermoelectric effect and surface effect contained in the elastic matrix is presented in this study.The governing equations for the QC microsphere in the matrix subject to the external electric loading are derived based on the nonlocal elastic theory,electro-elastic interface theory,and eigenvalue method.A comparison between the existing results and the finite-element simulation validates the present approach.Numerical examples reveal the effects of temperature variation,nonlocal parameters,surface properties,elastic coefficients,and phason coefficients on the phonon,phason,and electric fields.The results indicate that the QC microsphere enhances the mechanical properties of the matrix.The results are useful for the design and understanding of the characterization of QCs in micro-structures.

A Dugdale-Barenblatt model for elliptical orifice problem with asymmetric cracks in one-dimensional orthorhombic quasicrystals

By means of Muskhelishvili’s method and the technique of generalized conformal mapping,the physical plane problems are transformed into regular mathematical problems in quasicrystals(QCs).The analytical solution to an elliptical orifice problem with asymmetric cracks in one-dimensional(1D)orthorhombic QCs is obtained.By using the Dugdale-Barenblatt model,the plastic simulation at the crack tip of the elliptical orifice with asymmetric cracks in 1D orthorhombic QCs is performed.Finally,the size of the atomic cohesive force zone is determined precisely,and the size of the atomic cohesive force zone around the crack tip of an elliptical orifice with a single crack or two symmetric cracks is obtained.

General solutions of plane problem in one-dimensional quasicrystal piezoelectric materials and its application on fracture mechanics

Based on the fundamental equations of piezoelasticity of quasicrystals （QCs）, with the symmetry operations of point groups, the plane piezoelasticity theory of one- dimensional （1D） QCs with all point groups is investigated systematically. The gov- erning equations of the piezoelasticity problem for 1D QCs including monoclinic QCs, orthorhombic QCs, tetragonal QCs, and hexagonal QCs are deduced rigorously. The general solutions of the piezoelasticity problem for these QCs are derived by the opera- tor method and the complex variable function method. As an application, an antiplane crack problem is further considered by the semi-inverse method, and the closed-form so- lutions of the phonon, phason, and electric fields near the crack tip are obtained. The path-independent integral derived from the conservation integral equals the energy release rate.

Static deformation of a multilayered one-dimensional hexagonal quasicrystal plate with piezoelectric effect

Quasicrystals （QCs） are sensitive to the piezoelectric （PE） effect. This paper studies static deformation of a multilayered one-dimensional （1D） hexagonal QC plate with the PE effect. The exact closed-form solutions of the extended displacement and traction for a homogeneous piezoelectric quasicrystal （PQC）plate are derived from an eigensystem. The general solutions for multilayered PQC plates are then obtained using the propagator matrix method when mechanical and electrical loads are applied on the top surface of the plate. Numerical examples for several sandwich plates made up of PQC, PE, and QC materials are provided to show the effect of stacking sequence on phonon, phason, and electric fields under mechanical and electrical loads, which is useful in designing new composites for engineering structures.

Nonlocal vibration and buckling of two-dimensional layered quasicrystal nanoplates embedded in an elastic medium

A mathematical model for nonlocal vibration and buckling of embedded two-dimensional(2 D) decagonal quasicrystal(QC) layered nanoplates is proposed. The Pasternak-type foundation is used to simulate the interaction between the nanoplates and the elastic medium. The exact solutions of the nonlocal vibration frequency and buckling critical load of the 2 D decagonal QC layered nanoplates are obtained by solving the eigensystem and using the propagator matrix method. The present three-dimensional(3 D) exact solution can predict correctly the nature frequencies and critical loads of the nanoplates as compared with previous thin-plate and medium-thick-plate theories.Numerical examples are provided to display the effects of the quasiperiodic direction,length-to-width ratio, thickness of the nanoplates, nonlocal parameter, stacking sequence,and medium elasticity on the vibration frequency and critical buckling load of the 2 D decagonal QC nanoplates. The results show that the effects of the quasiperiodic direction on the vibration frequency and critical buckling load depend on the length-to-width ratio of the nanoplates. The thickness of the nanoplate and the elasticity of the surrounding medium can be adjusted for optimal frequency and critical buckling load of the nanoplate.This feature is useful since the frequency and critical buckling load of the 2 D decagonal QCs as coating materials of plate structures can now be tuned as one desire.

胶片特性曲线在QA、QC中作用的探讨

本文利用胶片特性曲线对X线胶片感光特性及显定影配方的主要性能进行测量从而根据胶片及配方在特定环境下所反应的特性，制定与之相适应的摄影条件，指导X线摄影。作者认为：该方法是提高照片影像质量，在放射科实行有效的质量保证和质量控制的重要方法之一。

Bending and vibration of two-dimensional decagonal quasicrystal nanoplates via modified couple-stress theory

Based on the modified couple-stress theory,the three-dimensional(3D)bending deformation and vibration responses of simply-supported and multilayered twodimensional(2D)decagonal quasicrystal(QC)nanoplates are investigated.The surface loading is assumed to be applied on the top surface in the bending analysis,the tractionfree boundary conditions on both the top and bottom surfaces of the nanoplates are used in the free vibration analysis,and a harmonic concentrated point loading is applied on the top surfaces of the nanoplates in the harmonic response analysis.The general solutions of the extended displacement and traction vectors for the homogeneous QC nanoplates are derived by solving the eigenvalue problem reduced from the final governing equations of motion with the modified couple-stress effect.By utilizing the propagator matrix method,the analytical solutions of the displacements of bending deformation for the phonon and phason fields,the natural frequency of free vibration,and the displacements of the harmonic responses of the phonon and phason fields are obtained.Numerical examples are illustrated to show the effects of the quasiperiodic direction,the material length scale parameter,and the the stacking sequence of the nanoplates on the bending deformation and vibration responses of two sandwich nanoplates made of QC and crystal materials.

Fundamental solutions of critical wedge angles for one-dimensional piezoelectric quasicrystal wedge

Two problems of a one-dimensional(1D)piezoelectric quasicrystal(QC)wedge are investigated,i.e.,the two sides of the wedge subject to uniform tractions and the wedge apex subject to the concentrated force.By virtue of the Stroh formalism and Barnett-Lothe matrices,the analytical expressions of the displacements and stresses are derived,and the generalized solutions for the critical wedge angles are discussed.Numerical examples are given to present the mechanical behaviors of the wedge in each field.The results indicate that the effects of the uniform tractions and the concentrated force on the phonon field displacement are larger than those on the phason field.

Static response of functionally graded multilayered two-dimensional quasicrystal plates with mixed boundary conditions

The unusual properties of quasicrystals(QCs)have attracted tremendous attention from researchers.In this paper,a semi-analytical solution is presented for the static response of a functionally graded(FG)multilayered two-dimensional(2 D)decagonal QC rectangular plate with mixed boundary conditions.Based on the elastic theory of FG 2 D QCs,the state-space method is used to derive the state equations composed of partial differential along the thickness direction.Besides,the Fourier series expansion and the differential quadrature technique are utilized to simulate the simply supported boundary conditions and the mixed boundary conditions,respectively.Then,the propagator matrix which connects the field variables at the upper interface to those at the lower interface of any homogeneous layer can be derived based on the state equations.Combined with the interface continuity condition,the static response can be obtained by imposing the sinusoidal load on the top surfaces of laminates.Finally,the numerical examples are presented to verify the effectiveness of this method,and the results are very useful for the design and understanding of the characterization of FG QC materials in their applications to multilayered systems.

Three-dimensional interfacial fracture analysis of a one-dimensional hexagonal quasicrystal coating

In this paper, the three-dimensional(3D) interfacial fracture is analyzed in a one-dimensional(1D) hexagonal quasicrystal(QC) coating structure under mechanical loading. A planar interface crack with arbitrary shape is studied by a displacement discontinuity method. Fundamental solutions of interfacial concentrated displacement discontinuities are obtained by the Hankel transform technique, and the corresponding boundary integral-differential equations are constructed with the superposition principle.Green’s functions of constant interfacial displacement discontinuities within a rectangular element are derived, and a boundary element method is proposed for numerical simulation.The singularity of stresses near the crack front is investigated, and the stress intensity factors(SIFs) as well as energy release rates(ERRs) are determined. Finally, relevant influencing factors on the fracture behavior are discussed.

Al-Cu-Fe准晶薄膜/涂层的研究进展

综述了目前制备Al-Cu-Fe准晶薄膜/涂层的方法,并分析了其影响因素。重点评述了Al-Cu-Fe准晶薄膜/涂层的组织及其转变,介绍了Al-Cu-Fe准晶薄膜/涂层的性能及其应用,并指出了其今后研究趋势。

二氧化铈对准晶真空蒸镀薄膜的影响

采用DMD-450真空镀膜仪将Al65Cu20Fe15准晶粉末沉积在Q235钢表面制备薄膜。研究了二氧化铈对薄膜的组织和结构的影响。采用透射电镜（TEM）、扫描电镜（SEM）、X射线衍射仪（XRD）等分析了薄膜的组织结构和表面形貌。利用纳米压痕仪（MTS）测试了薄膜的显微硬度和弹性模量。结果表明：通过准晶粉末真空蒸镀可以形成准晶薄膜。其组成相有CuAl2，A1Cu3 and I（Al65Cu20Fe15）相等。薄膜的成分取决于制备工艺。二氧化铈对薄膜的结构没有产生明显的影响。但是薄膜的显微硬度和弹性模量随二氧化铈添加量的增加而提高。当二氧化铈添加量为5％（质量分数）时，薄膜的显微硬度达到9．0GPa，弹性模量最高达到190GPa。此外，二氧化铈的添加明显增加了薄膜的耐蚀性能。

Al基准晶薄膜/涂层研究进展

准晶材料固有脆性限制其作为结构性材料的应用,广泛用于表面薄膜/涂层,而得到高纯度准晶相与控制准晶相变仍是应用难点。围绕Al基准晶在表面薄膜/涂层应用方面,介绍真空蒸镀、溅射镀膜、热喷涂、激光熔覆等常用制备工艺,总结各工艺的特点。分析准晶薄膜/涂层的成分、冷却速度、热处理对准晶相变的影响,合理的制备工艺和适当的后续热处理对薄膜/涂层中形成高纯度准晶有显著提升。讨论相变对薄膜/涂层的力学性能、疏水性、摩擦性、耐腐蚀性和抗氧化性的影响,分析准晶薄膜/涂层在减磨耐磨涂层、热障涂层、太阳能选择性吸收薄膜等领域的应用前景。综述了近30年准晶薄膜/涂层的制备技术及改性研究的重要结果和研究现状,提出了准晶薄膜/涂层应用方面存在的问题并进行了展望。

涂层和薄膜态准晶材料的研究现状及展望

准晶材料兼具硬度高、摩擦系数小、耐磨损、耐腐蚀、表面能低等特性,有着十分广阔的应用前景。但受限于本征脆性,准晶材料不能作为结构件单独使用,涂层和薄膜形态成为研究热点。综述了准晶涂层和薄膜的几种制备工艺,主要介绍了热喷涂技术、激光熔覆技术、电子束沉积技术、真空蒸镀技术、磁控溅射技术,并对这几种镀膜技术的特点进行了归纳、对比、总结。详细概述了制备过程中涂层和薄膜的生长过程、生长机理,为之后相关研究工作奠定了良好的基础。对结构和性能的研究现状及在界面结合、组织转变、后续热处理工艺中面临的问题进行了讨论,性能方面主要包括准晶涂层和薄膜优良的抗氧化、耐腐蚀、耐磨损性能及其优异的不粘性,并对存在的相关问题提出了一些可能的解决方案。最后对准晶涂层和薄膜更先进的制备方法以及准晶材料在热障涂层、不粘涂层和固体润滑剂等方面的应用前景进行了展望。

Diurnal cooling for continuous thermal sources under direct subtropical sunlight produced by quasi-Cantor structure

In this paper, an optical radiative cooler with quasi-Cantor structure is theoretically proposed and analyzed. This simple and symmetrically designed optical structure operates upon continuous thermal sources in diurnal subtropical conditions, and its efficiency is much higher than natural cooling, for instance, when operating upon a typical 323.15 K continuous thermal source with a wind speed at 3 m·s^-1, it can generate a net cooling power of 363.68 W·m^-2, which is 18.26% higher than that of non-radiative heat exchange （natural cooling） under the same conditions. Additionally, several aspects are considered in its design to ensure a low cost in application, which is of great economical and environmental significance.

Structure and reflective properties of Al-Cu-Fe quasicrystalline thin film prepared by laser induced arc method

Al-Cu-Fe thin films were prepared by laser induced arc (laser-arc) method from a single source-Al63Cu25Fe12 alloy, which was proved to consist of quasicrystalline phase together with approximant phase. The composition of the deposited films meets the requirement for formation of icosahedral symmetry phase. Quasicrystalline phase was obtained after annealing the amorphous as-deposit film samples. The optical properties of the samples were investigated. Thin film samples of Al, Cu and Fe deposited under the same condition were employed for comparison. The results showed specific reflective properties of Al-Cu-Fe quasicrystal thin film in some wavelength range. The optical conductivity of the films exhibited a negative peak, centered about 440 nm in range of 190to 800 nm. The Al-Cu-Fe quasicrystal thin films could absorb almost all the ray in the wavelength range from 420nm to 450 nm. The ratio of absorption was greater than 99%.

Singularities of Three-Dimensional Cubic Piezoelectric Quasicrystal Composite Wedges and Spaces

In this paper,the planar problems of three-dimensional(3D)cubic piezoelectric quasicrystal composite wedges and spaces are investigated.The study focuses on the singular behaviors of interface corner and interface crack of composite wedges and spaces.To research the stress singularities,the stress function is assumed to have the exponential form.Based on the Stroh formalism and Barnett–Lothe matrices,we derive a crucial matrix concerned with material properties and wedge angle and obtain the transcendental equation determining the singular orders by simple multiplication of the crucial matrix.Numerical examples of the singular orders are given for some general cases including single,bi-material,and tri-material wedges and spaces under different boundary conditions.The correctness of numerical results is verified by comparison with the existing results of piezoelectric material.Numerical results show that the phonon field,phason field,electric field,material properties,and boundary conditions have great influences on singularities.