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A flexible Ti/Cr/Ti multilayer strain gauge have been successfully developed based on polyimide substrate. The pure Ti metal strain gauge have shown the hysteresis phenomenon at the relationship between resistance and strain during tensile test. The experimental results of multilayer strain gauge show that adding Cr interlayer can improve the recovery and stability of the sensing electrode. When the interlayer Cr thickness was increased from 0 to 70 nm, the resistance decreased from 27 to 8.8 kΩ. The gauge factor (GF) value also decreased from 4.24 to 2.31 with the increase in the thickness of Cr interlayer from 30 to 70 nm, and the hysteresis phenomenon disappeared gradually. The multilayer Ti/Cr/Ti film has feasible application for strain sensor.

In this study, we prepared metal oxide-metal-metal oxide (OMO) multilayer transparent electrodes based on indium tin oxide (ITO) and ZnO, viz., ITO/Ag/ITO (IAI) and ZnO/Ag/ZnO (ZAZ) by sputtering and investigated the influence of the thickness of the silver layer as well as the thickness and surface roughness of the metal oxide layers on the optoelectronic performance of the electrodes. The surface roughness of the metal oxide layers affect the critical thickness required to transform the low-conductivity semi-continuous silver films into high-conductivity continuous ones. The thicknesses of the metal oxide layers over and underneath the Ag layer can be modulated not only to enhance the transmittance of the electrodes but also to adjust the position of the maximum transmittance. Optimization of the thicknesses of the metal oxide and Ag layers allows the fabrication of high-quality transparent electrodes. The sheet resistance for the best ZAZ sample was 4.16 Ω/sq while the average transmittance (including glass) was 73.09% in the visible region. For IAI electrodes, the sheet resistance and the average transmittance in the visible region were 5.85 Ω/sq and 82.12%, respectively. The Haacke index indicated that for applications with high optical demands, the Ag film thickness should be 8.5 nm and 13.0 nm for ITO and ZnO systems, respectively. Moreover, semi-continuous Ag layers are bluish due to surface plasmon resonance. This study defines a criterion for determining the optimal thickness of Ag layers in OMO films.

In this study, Ag nanowire (AgNW) was used to fabricate ITO/AgNW/ITO (IAI) and ZnO/AgNW/ZnO (ZAZ) hybrid transparent electrodes. The covered area ratio of AgNW showed that when AgNW concentration n AgNW ≥ 2.0 mg/mL, AgNW easily agglomerated during the spin-coating. Meanwhile, Haacke index and haziness measurements also indicated that for application with high optical demands, the AgNW concentration should be ≤2.0 mg/mL for both ZnO or ITO systems. In this study, when n AgNW = 2.0 mg/mL, the sheet resistant of ZAZ electrodes was 10.5 Ω/sq while the transmittance (including glass) was 72.7% in the visible region. For IAI electrodes, the sheet resistant was 18.8 Ω/sq and transmittance (including glass) was 78.2% in the visible region. Further analysis implied that the sheet resistance of hybrid electrodes could be as low as 10 Ω/sq by optimizing AgNW distribution as well as using suitable annealing techniques.

In this study, indium-zinc oxide (IZO)/silver (Ag)/IZO (ZAZ) flexible transparent electrodes were prepared on polyethylene terephthalate substrate using radio frequency sputtering technique. Experimental results showed that when the Ag film transited from semi-continuous state to continuous state, the ZAZ electrode exhibited high optoelectronic performance. The best ZAZ sample had a quite wide range of high transmittance and an average transmittance of 78.9% in visible light region, and sheet resistance of [Formula: see text]/sq and a Haacke Index of [Formula: see text]. The bending test revealed that the [Formula: see text] (change in sheet resistance) of ZAZ electrodes after 1000 bends was still less than 25% while the electrical properties of IZO films deteriorated after only 100 bending tests.

This study presents three hybrid processing models for cutting a glass substrate, and compares their cutting speeds. The three models are (I) thermal fracture cutting technology (TFCT)-assisted laser ablation, (II) ultrasonic-assisted laser ablation, and (III) ultrasonic and TFCT-assisted laser ablation. In the experiment, a 12 W 355 nm Nd:YVO 4 laser system, a 40 W CO 2 laser and an ultrasonic transducer were used to cut 3 mm thick soda-lime glasses. Lasers and ultrasonic transducers were used as heat sources and vibration sources, respectively. Results show that the surface morphology of the soda-lime glass sheet depends on the processing models. After cutting, the surface and cross-sectional morphology of glass substrate were observed using a portable digital microscope and residual stresses were also evaluated thanks to a photoelasticity instrument.

In this work, ITO/silver nanowire (AgNW)/ITO (IAWI) and IZO/AgNW/IZO (ZAWZ) hybrid electrodes were prepared on polyethylene terephthalate (PET) substrates at low temperature. The physical properties of the flexible electrodes were studied using X-ray diffraction, spectrophotometer, field-emission scanning electron microscope, Hall, and four-point probe resistivity measurements. The Haacke index shows that an electrode has the best optoelectronic properties at an AgNW concentration of 2.0 mg/mL. At this concentration, the sheet resistances of the IAWI and ZAWZ electrodes are 18.6 [Formula: see text]/sq and 16.0 [Formula: see text]/sq, respectively. The bending test results show that the electrical properties of both ITO and IZO films became poor only after 100 bending tests. In contrast, the sheet resistances of the IAWI and ZAWZ electrodes show no obvious change after 1000 bending tests, confirming their excellent flexibility. A hyperspectral technique is developed to characterize the damages within the electrodes caused by the bending test.

In this study, a three dimensional transversely isotropic piezoelectric layered half-space subjected to concentrated loading and electric charge was analyzed. This paper provides an effective analytical methodology to obtain the explicit full-field solutions for this problem. Due to the dissimilar structures of the solutions, the applied loadings are separated into axis-symmetric loadings and non-symmetric loadings. By using the double Fourier transformation technique in conjunction with series expansion, the explicit closed-from solutions for displacements, stresses, and the electric field in the layered half-space are obtained. The analytical solutions are valid for loadings applied either in the interior or at the surface of the structure. It can be seen that the complete solutions obtained by the method used in this study comprise only the fundamental solutions of an infinite space with a concentrated loading. One of the fundamental solutions is the Green's function of an infinite space and the others are solutions induced to satisfy the boundary and interface conditions. The mathematical meaning of the method used in the study is in fact the image method or Mindlin's superposition method. Instead of finding image singularities manually, the intensity and locations of the image singularities are determined automatically from the mathematical technique used in this paper. Taking PZT materials as an example, the numerical computation for the full-field distributions of the displacement and electric field in the layered half-space medium subjected to a point force and a point charge was discussed.

An interior spray method is proposed for enhancing the heat transfer performance of a compact rhombus-pitch shell-and-tube spray evaporator. The experimental results show that the shell-side heat transfer coefficient obtained using the proposed spray method is significantly higher than that achieved in a conventional flooded-type evaporator. Four different spray axis incident angles (0°, 45°, 60° and 75°) are tested in order to investigate the effect of the spray inclination angle on the heat transfer performance of the spray evaporator system. It is shown that the optimal heat transfer performance is obtained using a spray axis incident angle of 60°.

Based on the theory of linear piezoelectricity, this study presents an exact solution for a two dimensional indentation on a piezoelectric ceramic half-plane with different contact conditions. The flat-ended indenters are assumed to be rigid. Besides, they can either be insulating or conducting. In addition, different contact conditions, including frictionless, frictional, and adhesive punches are investigated. Lekhnitskii's formulism and Fourier transforms are used to obtain the Green's function of a piezoelectric ceramic half-plane subjected to a point loading. Utilizing Green's half-plane function, we obtain the three integral equations by connecting generalized displacement gradients at the surface and surface loading. Both uncoupled and coupled integral equations can be transformed into a Fredholm integral equation. The analytical closed form solutions of the contact forces and the electric charges under the indenter can be derived by solving the Fredholm integral equations. Once the distributions of...

The two dimensional punch problem for planar anisotropic elastic half-plane is revisited using the Lekhnitskii's formulation with aid of the Fourier transform and boundary integral equation. Four different conditions of contact problem for the rigid punch are analyzed in this study. From the combination of surface Green's function of half-plane and Hooke's law of anisotropic material, a set of Fredholm integral equations are obtained for mixed boundary value problems. After solving the integral equation according to specified contact condition, the explicit distributions of surface traction under the punch are obtained in closed-form. From the surface traction and Green's function of anisotropic half-plane, the full-field solutions of stresses are constructed. Numerical calculations of surface traction under the rigid punch are presented base on the analysis and are discussed in detail.

The degeneration of image singularities from an anisotropic material to an isotropic material for a half-plane is discussed in this study. The Green’s functions for anisotropic and isotropic half-planes with traction free boundary subjected to concentrated forces and dislocations have been obtained by many authors. It was commonly accepted that the solution of isotropic problem cannot be derived from anisotropic solutions. However, we believe that this possibility exists as we will demonstrate in this paper. Anisotropic materials include only image singularities of order O(1/r) (i.e., forces and dislocations) existing on image points. There are many image points for anisotropic materials and the locations of these image points depend on the material constants. However, isotropic materials have only one image point with higher order image singularities (O(1/r2), O(1/r3)). From the analysis provided in this study, it is found that the higher order image singularities for an isotropic half-plane are generated by combining the concentrated forces and dislocations when an anisotropic material degenerates to an isotropic material. The solutions of higher order image singularities for isotropic material are dependent. Therefore, these image singularities can be combined to form only three or four simpler image singularities acting on an image point of the isotropic material.

This study presents explicit analytical solutions of heat conduction problems for isotropic media with finite dimensions. The geometry configurations considered in this study include composite layer, wedge and circular media. The boundary conditions are assumed to be either thermal isolation or isothermal. The full field analytical solutions of temperature and heat fluxes for the composite layered media subjected to an embedded heat source are derived first by Fourier transform technique in conjunction with the image method. The corresponding problems of composite wedge and circular media are constructed by conformal mapping and the solutions of composite layer media. The explicit full field solutions are expressed in simple closed-forms which can be easily used in engineering applications. The numerical calculations of the temperature and heat fluxes distributions are provided in full field configuration base on the available analytic solutions.

By using the Mellin transform technique in conjunction with the image method, the two-dimensional full-field solutions of dissimilar isotropic composite annular wedges subjected to anti-plane concentrated forces and screw dislocations are presented in explicit forms. The composite wedges consist of two materials that have equal apex angle and are bonded together along an interface. The explicit full-field solutions are presented in series forms for combinations of traction and displacement boundary conditions. For the special case of composite sharp wedges with finite radius or infinite extent, the solutions with functional forms are obtained and only consist of simple trigonometric functions. Explicit solutions of the stress intensity factors are obtained for a semi-infinite interface crack and a circular composite disk with an interface crack. With the aid of the Peach–Koehler equation, the explicit forms of the image forces exerted on screw dislocations are easily derived from the full-field solutions of stresses. Numerical results of full-field stress distributions and image forces exerted on screw dislocations are presented and discussed in detail.

The problem of a planar anisotropic elastic layered halfplane subjected to concentrated forces and edge dislocations applied either in the layer or in the halfplane is analysed. One of the objectiv...

Green’s functions for isotropic materials in the two-dimensional problem for elastic bimaterials with perfectly bonded interface are reexamined in the present study. Although the Green’s function for an isotropic elastic bimaterial subjected to a line force or a line dislocation has been discussed by many authors, the physical meaning and the structure of the solution are not clear. In this investigation, the Green’s function for an elastic bimaterial is shown to consist of eight Green’s functions for a homogeneous infinite plane. One of the novel features is that Green’s functions for bimaterials can be expressed directly by knowing Green’s functions for the infinite plane. If the applied load is located in material 1, the solution for the half-plane of material 1 is constructed with the help of five Green’s functions corresponding to the infinite plane. However, the solution for the half-plane of material 2 only consists of three Green’s functions for the infinite plane. One of the five Green’s functions of material 1 and all the three Green’s functions of material 2 have their singularities located in the half-plane where the load is applied, and the other four image singularities of material 1 are located outside the half-plane at the same distance from the interface as that of the applied load. The nature and magnitude of the image singularities for both materials are presented explicitly from the principle of superposition, and classified according to different loads. It is known that for the problem of anisotropic bimaterials subjected to concentrated forces and dislocations, the image singularities are simply concentrated forces and dislocations with the stress singularity of order O(1/r). However, higher orders (O(1/r2) and O(1/r3)) of stress singularities are found to exist in this study for isotropic bimaterials. The highest order of the stress singularity is O(1/r3) for the image singularities of material 1, and is O(1/r2) for material 2. Using the present solution, Green’s functions associated with the problems of elastic half-plane with free and rigidly fixed boundaries, for homogeneous isotropic elastic solid, are obtained as special cases.

Although the Green's function for an isotropic elastic half-space subjected to a line force or a line dislocation is well-known, the physical meaning of the solution is not clear. Green's functions for twodimensional plane-strain and plane-stress problems of an isotropic elastic half-space with a free or rigidly fixed surface subjected to line forces and line dislocations are reexamined in this study. The results are more explicit when compared with existing solutions in the literature. The Green's function for a half-space consists of four or five Green's functions for an infinite space, the number depending on the boundary condition at the half-space surface and the applied loading. One of the Green's functions in the infinite space has its singularity located in the half-space where the load is applied, and the other image singularities are located outside the half-space with the same distance from the surface as that of the applied load. The nature and magnitude of image singularities have been derived from the principle of superposition and classified according to different loads. The image singularities are found to possess some interesting properties. It is found that the fundamental solutions required to construct all the image singularities of applied forces and dislocations for the half-space are only forces and dislocations and their differentiations in the infinite space. Furthermore, the limiting case of the applied force or dislocation approaching the surface is also discussed in this study.

Green’s functions for anisotropic elastic multilayered media subjected to antiplane shear deformation are presented in this study. The antiplane shear deformation due to a concentrated shear force and screw dislocation in an arbitrary layer was investigated in detail. A linear coordinate transformation is introduced in this study to simplify the problem. The linear coordinate transformation reduces the anisotropic multilayered problem to an equivalent isotropic problem without complicating the geometry of the problem. Explicit analytical solutions were derived using the Fourier transform and the series expansion technique. The complete solutions for the multilayered problem consist only of the simplest solutions obtained from an infinite homogeneous medium with concentrated loadings. Numerical results for the full-field stress distribution in multilayered media subjected to a point body force are presented. These numerical results were compared with the solutions obtained by considering the multilayered medium as one layer with effective elastic constants determined from the averaged material constants of the multilayered medium. It is found that the shear stress τyz of the homogeneous one layer solution is a very good approximation of the result for the multilayered medium; however, the shear stress τxz in these two solutions has a large discrepancy due to the fact that τxz is discontinuous at the interfaces of the multilayered medium. [S0021-8936(00)01703-7]