Effect Of Geometrical Shape Research Articles

Effects of In-Plane Geometric Shapes on Thermal Shock Resistance of Ultra-High Temperature Ceramic Components

In thermal structural engineering, ceramic components can have various shapes and be constrained. It is traditionally known that the thermal shock resistance (TSR) of ceramic components (with conduction occurring in the thickness direction), such as disk, oval plate and rectangular plate, is independent of the in-plane geometric shapes. The present study shows that this is valid for ceramic components that are free, but when the components are constrained, the in-plane geometric shapes can have significant effects on the TSR of ceramics. Three types of components, with the edges of the lower surfaces clamped are studied. Under the second or third type thermal boundary conditions, the TSR of the disk is the best; that of the oval plate decreases as the ellipticity increases; and that of the rectangular plate is approximately equal to that of the oval plate with ellipticity of 1.2. This is because that the asymmetry of the in-plane geometric shapes, as well as the asymmetry of the mechanical boundary conditions, can worsen the TSR of the ceramics when the components are constrained. This is very important for the design and application of ceramics in the thermal structural engineering.

The Effects of Nonuniform Illumination on the Electrical Performance of a Single Conventional Photovoltaic Cell

Photovoltaic (PV) concentrators are a promising approach for lowering PV electricity costs in the near future. However, most of the concentrators that are currently used for PV applications yield nonuniform flux profiles on the surface of a PV module which in turn reduces its electrical performance if the cells are serially connected. One way of overcoming this effect is the use of PV modules with isolated cells so that each cell generates current that is proportional to the energy flux absorbed. However, there are some cases where nonuniform illumination also exists in a single cell in an isolated cells PV module. This paper systematically studied the effect of nonuniform illumination on various cell performance parameters of a single monocrystalline standard PV cell at low and medium energy concentration ratios. Furthermore, the effect of orientation, size, and geometrical shapes of nonuniform illumination was also investigated. It was found that the effect of nonuniform illumination on various PV cell performance parameters of a single standard PV cell becomes noticeable at medium energy flux concentration whilst the location, size, and geometrical shape of nonuniform illumination have no effect on the performance parameters of the cell.

Effects of short fiber tip geometry and inhomogeneous interphase on the stress distribution of rubber matrix sealing composites

ABSTRACTThe normal and interfacial shear stress distributions with flat fiber tip of short‐fiber‐reinforced rubber matrix sealing composites (SFRC) compared with the shear lag model were investigated by using the finite element method (FEM). The results indicate that stress values do not agree with those calculated by the shear lag model. The effect of different geometrical shapes of fiber tip on the stress distributions of SFRC was also investigated. The geometrical shapes of fiber tip under present investigation are flat, semi‐elliptical, hemispherical, and circular cone, respectively. The results show that the hemispherical fiber tip transfers the load with less stress concentration and is contributed to controlling the interface debonding failure more effectively than other shapes of fiber tip. Further study on the effect of the inhomogeneous interphase properties on the normal and interfacial shear stresses of hemispherical fiber tip was also conducted. The results indicate that the normal stress increases with the increase of the interphase thickness and interfacial shear stress remains unchanged, and the normal stress values of SFRC with interphase are higher than those without interphase. The interphase elastic modulus has no influence on the stress distributions along the direction to the fiber axis. The stress distributions along the radial direction in the interphase end are largely dependent on the interphase elastic modulus, and the interfacial shear stress is larger than the normal stress, which reveals that a significant part of the external load is transferred from the fiber to the matrix through shear stresses within the interphase. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41638.

MINIMIZATION OF INDOOR TEMPERATURES AND TOTAL SOLAR INSOLATION BY OPTIMIZING THE BUILDING ORIENTATION IN HOT CLIMATE

In order to reduce the energy load, understanding the overall architectural design features and optimizing building orientation are important. They are guided by natural elements like sunlight and its intensity, direction of the wind, seasons of the year and temperature variations. The main aim of presented analysis is to give solutions for architects to design standard and low energy buildings in a proper way. The orientation effect of a non-air-conditioned building on its thermal performance has been analyzed in terms of direct solar gain and temperature index for hot-dry climates. This paper aims at introducing an improved methodology for the dynamic modeling of buildings by the thermal nodal method. The study is carried out using computer simulation. This study examines also the effect of geometric shapes on the total solar insolation received by a real building. As a result, the influence of orientation changing depends on the floors and exterior walls construction materials, the insulation levels and application of the inseparable rules of the bioclimatic design. Solar radiation is the most major contributor to heat gain in buildings.

Nonlinear buckling of higher deformable S-FGM thick circular cylindrical shells with metal–ceramic–metal layers surrounded on elastic foundations in thermal environment

An analytical approach on the nonlinear response of thick functionally graded circular cylindrical shells with temperature independent material property surrounded on elastic foundations subjected to mechanical and thermal loads is presented. Material properties are graded in the thickness direction according to a Sigmoid power law distribution in terms of the volume fractions of constituents (S-FGM). The formulations are based on the third order shear deformation shell theory taking into account von Karman nonlinearity, initial geometrical imperfection and Pasternak type elastic foundation. By applying Galerkin method and using stress function, explicit relations of thermal load–deflection curves of the S-FGM shells are determined. Detailed parametric studies are carried out to investigate effects of volume fraction index, material properties and geometrical shapes, axial compressions and thermal load, foundation stiffness and imperfection on nonlinear buckling behaviors of S-FGM thick circular cylindrical shells. The present analysis is validated by comparing results with other publications.

Numerical and analytical study of the impinging and bouncing phenomena of droplets on superhydrophobic surfaces with microtextured structures.

The dynamics of droplets impinging on different microtextured superhydrophobic surfaces are modeled with CFD combined with VOF (Volume of Fluid) technique. The method is validated by experimental data and an analytical model (AM) that is used to predict the penetrating depth and the maximum spreading diameter of an impinging droplet. The effects of geometrical shapes and operating conditions on the spreading and bouncing behaviors of impinging droplets are investigated. Six surfaces with different shapes of pillars are considered, namely, triangular prism, square pillar, pentagonal prism, cylindrical pillar, and crisscross pillar surfaces. The bouncing ability of an impinging droplet on textured surfaces can be illustrated from three aspects, namely, the contact time, the ranges of velocities for rebound and the penetrating depth of liquid in the maximum spreading stage. The surface with crisscross pillars exhibits the best ability to rebound, which can be attributed to its large capillary pressure (PC) and its special structures that can capture air in the gaps during the impinging process.

Isogeometric locking-free plate element: A simple first order shear deformation theory for functionally graded plates

An effective, simple, robust and locking-free plate formulation is proposed to analyze the static bending, buckling, and free vibration of homogeneous and functionally graded plates. The simple first-order shear deformation theory (S-FSDT), which was recently presented in Thai and Choi (2013) [11], is naturally free from shear-locking and captures the physics of the shear-deformation effect present in the original FSDT, whilst also being less computationally expensive due to having fewer unknowns. The S-FSDT requires C1-continuity that is simple to satisfy with the inherent high-order continuity of the non-uniform rational B-spline (NURBS) basis functions, which we use in the framework of isogeometric analysis (IGA). Numerical examples are solved and the results are compared with reference solutions to confirm the accuracy of the proposed method. Furthermore, the effects of boundary conditions, gradient index, and geometric shape on the mechanical response of functionally graded plates are investigated.

Basic solution of two 3D rectangular cracks in an orthotropic elastic media

By using the generalized Almansi's theorem and the Schmidt method, the solution of two 3D rectangular cracks in an orthotropic elastic media is investigated. The problems are solved through 2D Fourier transform as three pairs of dual integral equations, in which the unknown variables are the displacement jumps across the crack surfaces. To solve the dual integral equations, the displacement jumps across the crack surfaces are directly expanded as a series of Jacobi polynomials. The effects of the geometric shape of the rectangular crack and the distance between two rectangular cracks on the stress intensity factors (SIFs) in an orthotropic elastic media are concluded.

Numerical analysis of added mass for open flat membrane vibrating in still air using the boundary element method

Added mass has significant effect on the vibration of membrane structures, which cannot be ignored during vibration analysis. Actually, the added mass of typical objects, such as cylinders and spheres, moving in fluid with acceleration have been widely investigated. However, research on the added mass of flexible structures is still limited. Although several numerical methods had been developed to investigate the added mass of flexible structures, the efficiency of the numerical methods is not verified by experiment tests. In this study, a framework to numerically analysis the added mass of open flat membranes has been established by using the Boundary Element Method (BEM). In order to evaluate hypersingular integral, the Stokes formula converting the surface integral to the curvilinear integral is used. Two added mass models are discussed, one only considering the effect of the membrane geometric shape, and another considering the effect of the geometric shape and the mode shape of membranes. Based on comparative analysis between numerical results and experimental results, it is shown that the added mass only considering the effect of geometric shape can agree well with the test results in low-order modes, however, the error will be increased as the order of vibration modes increasing. The added mass considering the effect of the geometric shape and the mode shape can have much better conformity with the test results both in low-order modes and high-order modes. The Modal Assurance Criterion (MAC) is used to compare the mode shapes of membranes vibrating in vacuum and in air. MAC values indicate that for uniform mass distribution of the membrane, there is little difference between the mode shapes of the membrane vibrating in vacuum and in air, while for nonuniform mass distribution of the membrane, the difference between the mode shapes of the membrane vibrating in vacuum and in air is little in low modes and is large in high modes.

Effects of Geometrical Shapes and Orientations of Metal Foams Subjected to Impact Loading

The effects of geometrical shapes are believed to play significant role in the deformation of metal foams under impact loading. This research was carried out to investigate the deformation behaviour of a single cellular cell of metal foam with different geometrical shapes. The simulation analyses were done on various two dimensional shapes with the consideration of the material properties. Two parameter values had been studied to determine the dynamic deformation behaviour of various geometrical shapes i.e. the internal energy and kinetic energy. It is found that, the geometrical shapes have shown significant effects on the dynamic deformation of single metal foam cell. It is hoped that this study could contribute significant result to the research of the metal foams especially in analyzing the shape effects to the behaviour of the metal foam under impact loading.

Numerical Investigation of the Effect of Stenosis Geometry on the Coronary Diagnostic Parameters

The present study deals with the functional severity of a coronary artery stenosis assessed by the fractional flow reserve (FFR). The effects of different geometrical shapes of lesion on the diagnostic parameters are unknown. In this study, 3D computational simulation of blood flow in three different geometrical shapes of stenosis (triangular, elliptical, and trapezium) is considered in steady and transient conditions for 70% (moderate), 80% (intermediate), and 90% (severe) area stenosis (AS). For a given percentage AS, the variation of diagnostic parameters which are derived from pressure drop across the stenosis was found in three different geometrical shapes of stenosis and it was observed that FFR is higher in triangular shape and lower in trapezium shape. The pressure drop coefficient (CDP) was higher in trapezium shape and lower in triangular model whereas the LFC shows opposite trend. From the clinical perspective, the relationship between percentage AS and FFR is linear and inversely related in all the three models. A cut-off value of 0.75 for FFR was observed at 76.5% AS in trapezium model, 79.5% in elliptical model, and 82.7% AS for the triangular shaped model. The misinterpretation of the functional severity of the stenosis is in the region of 76.5%-82.7 % AS from different shapes of stenosis models.

Optimization of Beam Mode for High Efficiency Laser Thermal Forming within Metallurgical Constraints

In the laser forming (LF) process, laser induced temperature distribution within the work-piece is of paramount importance. Through control of process parameters and depending on work-piece geometry, the temperature distribution can be altered to achieve either localized plastic compressive strains or elastic-plastic buckling. Conventionally, three process parameters are manipulated in order to control the temperature distribution within the work-piece; traverse speed, average power and spot size. Additionally, the intensity distribution and geometrical shape of the beam incident on the work-piece surface can be manipulated. The latter has the potential to be useful in maintaining bend angle per pass whilst working within strict metallurgical constraints. In this paper, the effect of beam intensity distribution and geometrical shape on the LF of automotive grade high strength DP 1000 steel sheet is investigated numerically and experimentally, with particular emphasis on optimization for minimal micro-structural transformation.

An investigation on the effect of geometric shape of streams on stream/ground water interactions and ground water flow

Ground water should be used efficiently and improved for sustainable water management plans. For this purpose, comprehensive ground water flow models are developed incorporating surface/ground water interactions. Typically, these models require a significant amount of hydrological parameters and the sensitivities of these parameters on interaction mechanisms need to be clarified. Therefore, in this study, the role of the geometric shape of the stream on stream/ground water interactions is investigated. First, an analytical solution for two-dimensional ground water flow is developed with sloping stream boundary in an isotropic and homogeneous aquifer. Then, ground water head distribution and hyporheic exchange flow between stream and aquifer are obtained by conducting sensitivity analyses with prototype models developed using Visual MODular Finite-Difference FLOW in order to observe individual effects of each stream property. Finally, by incorporating the highest possible stream/ground water interaction conditions into a conceptual stream-aquifer model, the combined effects of different stream shapes are interpreted. Results show that slope, abrupt slope change, and flow path of stream affect the interactions significantly. Moreover, interaction flow rates increase further under the combined effects of these stream properties. The outputs of this work will ultimately be used in site investigations and in forecasting ground water hydrology.

Origin of the low piezoelectric coefficient of metal core 0.3Pb(Zn1/3Nb2/3)O3–0.7Pb(Zr,Ti)O3 piezoelectric fibers

The piezoelectric properties of 0.3Pb(Zn1/3Nb2/3)O3–0.7Pb(Zr,Ti)O3 metal-core piezoelectric fibers (0.3PZN–0.7PZT MPFs) (k31=0.253, d31=−120pC/N) are lower than those of bulk ceramic counterpart (k31=0.375, d31=−195pC/N). In order to investigate the origin of this discrepancy, geometrical shape effect and polarization were studied. The effect of geometrical shape is a main cause of the decreased piezoelectric properties of the MPF. However, even though the effect of geometrical shape being considered, the piezoelectric properties of the MPF are much lower than expected. After considering the polarization effect, there is excellent agreement between the expected and experimental measurements. The effect of geometrical shape and polarization are the cause of the decreased properties of the MPFs.

Threshold fracture energy in solid particle erosion

The effect of geometrical shape of eroding absolutely rigid particles on the threshold rate of failure has been studied. The Shtaerman–Kilchevsky theory of quasi-static blunt impact, which generalizes the Hertzs classical impact theory, is used for modelling the frictionless contact interaction of an axially-symmetric particle with an elastic half-space. The incubation time fracture criterion is applied for predicting surface fracture. It is shown that there exists a critical value of the particle shape parameter such that for all its lower values, the fracture energy possesses a non-zero minimal value.

Numerical analysis of welding residual stress and distortion in laser+GMAW hybrid welding of aluminum alloy T-joint

A 3-D finite element model is developed to predict the temperature field and thermally induced residual stress and distortion in laser+GMAW hybrid welding of 6061-T6 aluminum alloy T-joint. And the characteristics of residual stress distribution and deformation are numerically investigated. In the simulation, the heat source model takes into account the effect of joint geometric shape and welding torch slant on the heat flux distribution and a sequentially coupled thermo-mechanical method is used. The calculated results show that higher residual stress is distributed in and surround the weld zone. Its peak value is very close to the yield strength of base metal. Besides, a large deformation appears in the middle and rear part of the weldment.

A buckling verification approach for monolithic and laminated glass elements under combined in-plane compression and bending

Glass elements are widely used in modern buildings as structural columns, beams, stiffeners. Nevertheless, due to accidental eccentricities, additional loads, boundary conditions or imperfection factors, glass beam–columns are frequently subjected to in-plane compressive actions combined with bending moments. Because of this reason, the paper focuses on the buckling resistance of glass elements subjected to eccentric compressive loads. Based on large experimental numerical results available in literature for monolithic and laminated glass columns or beams in out-of plane bending, verification criteria for these simple loading conditions are firstly recalled from previous contributions. Subsequently, numerical static incremental simulations are performed with a finite-element model able to predict the buckling strength of imperfect glass elements eccentrically compressed. In it, also the effects of various geometrical imperfection shapes are deeply investigated. Finally, an analytical interaction curve is proposed for a conservative and rational buckling verification of monolithic and laminated structural elements.

Plasmon properties of silver spherical nanoparticles and films

The effects of the geometrical shape of silver nanoparticles and the electronic configurations of Ag atom in the ground and excited states on the plasmon characteristics of nanoparticles are considered. A relationship between the static polarizability of silver and gold atoms and the plasmon energies of nanoparticles is found. The ΔE excitation energy of a silver atom that corresponds to the 4d105s(2S1/2) → 4d105p(2P1/2 and 2P3/2) transition is shown to determine the plasmon energy of thin silver films. In the case of spherical silver nanoparticles in aqueous solution, the size effect—namely, the correlation between λpl wavelengths of plasmon transitions and d diameters of nanoparticles—is discovered. With the increase in the diameter of nanoparticles, the plasmon transition peaks are red shifted. In the range of d = 9–120 nm, λpl values are shown to change from 370 to 440 nm. The resonance splitting of plasmon bands determined by the mixed valence states of silver atoms is predicted.

Look Out, There is a Triangle behind You! The Effect of Primitive Geometric Shapes on Perceived Facial Dominance

Previous research has shown that perceived facial valence is biased toward background valence. Here, we examine whether background dominance also affects perceived facial dominance. In particular, we hypothesized that downward-pointing triangles, which are known to convey threat, would affect perceived facial dominance. Participants judged perceived facial dominance of neutral faces presented overlaid on downward- or upward-pointing background triangles. Our results show that neutral faces are indeed judged more dominant when seen with a downward-pointing triangle in the background. The fact that simple geometric background shapes can affect facial judgments may have important implications for the design and experience of our daily environment and multimedia content.

Stress‐assisted formation of surface gratings on polymer films

AbstractThe effect of biaxial‐residual–compressive surface stress on the surface modulation of solid films is analyzed. The results show that the biaxial compressive stress can create surface modulation with the orientation being 45° (135°) to the principal directions of the stresses. Using uniaxial tension, a complementary set of nonsymmetrical polymer ripple gratings is formed on the fracture surface of a polymer film that is sandwiched between two relatively glass slides. The effect of geometrical shape and boundary confinement is examined on the surface modulation. The orientation of the polymer ripple gratings is found to be 45° to the longitudinal direction of the films for long‐rectangular polymer thin films in accord with the analysis. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers