Papers by Keyword: Anisotropic

Abstract: In this work, the total potential energy of an anisotropic plate subjected to uniformly distributed lateral forces was developed using a complete three-dimensional constitutive relation. The kinematics equations were developed based on the Alternative II Refined plate theory. Variation of the total potential energy with respect to displacement and rotations gave the governing equation and compatibility equations respectively. By solving the governing and compatibility equations, a polynomial displacement function was obtained which by satisfying the boundary conditions gave the peculiar displacement function for any specific case. The stiffness coefficients for an anisotropic plate were then obtained using the displacement function. Thereafter, using the stiffness coefficients and the displacement functions, the equations for the in-plane normal and shear stresses as well as the transverse normal and shear stresses were determined. Also, the equations for the lateral displacement and the in-plane displacements were determined. The numerical values of the in-plane and out-of-plane stresses parameters as well as the displacement parameters were determined for a square plate for span to thickness ratios of 5, 10, 20 and 100 at angle of fiber orientations of 08, 308, 458, 608 and 908. It was observed that the variations in the stresses and displacements are only significant for span to thickness ratio of 20 and less. This signifies that the theory which considers shear deformation is suitable for thick plate analysis. The results from this work are compared with the works of previous researchers using simple percentage difference and the values are reasonable as the maximum percentage difference is 19.49%.

Abstract: In this work, the creep analysis of thick-walled rotating cylinder made of Aluminum Silicon Carbide under internal pressure has been investigated taking some assumptions, viz. no change in the volume of the cylinder, cylinder material is anisotropic, principal axes coincides with the axes of anisotropy, effective stress is dependent upon effective strain rate, and there is zero strain in the axial direction (Z direction in polar coordinate). Sherby’s law has been used to calculate the creep rate. After finding the formulas for radial, tangential and axial stresses for anisotropic cylinder, the findings have been validated by checking the values and comparing the graphs for an isotropic cylinder case with one of the already published research for isotropic cylinders with similar conditions. The graphs plotted in cases of anisotropic cylinder, enables us to conclude that despite large stress values in the radial and tangential directions, the creep rates in such cylinders were found to be approximately zero. This led to deduce that anisotropy is very helpful in designing long-lasting cylinders. In corollary, anisotropy helps in minimizing creep behaviour in radial and tangential directions.

Abstract: Through the patented process of hybrid forming [1], it is possible to produce a bonded metal-plastic-hybrid component in one process step with the help of an edge-sealed pressing tool. Such a component exhibits an enormous energy absorption potential. To use this complete potential, a reliable FE-Modelling is necessary, that can exactly replicate the complex material layup consisting of an isotropic metal, a very thin bonding layer, and an anisotropic glass mat reinforced thermoplastic (GMT) for crash load case. A methodology is proposed to numerically predict the behavior of the metal GMT aluminum components. And finally, the experimental results of Hybrid components are validated for three-point bending and axial crash load cases.

Abstract: This study introduces a sucrose acetate isobutyrate (SAIB) as an additive of magnetorheological elastomers (MREs) to be added in silicone rubber matrix and carbonyl iron particles (CIPs) as their filler. The CIPs were fixed at 60 wt% and two types of MREs sample were fabricated which are isotropic and anisotropic. Rheological properties related to shear storage modulus were measured using a rheometer (MCR 302, Anton Paar). The experimental results demonstrated that the magnetorheological (MR) effect of anisotropic MREs-based Silicone/SAIB was 126 % as compared to isotropic MREs-based Silicone/SAIB, 64%. The fabricated MREs samples were frequency and strain dependent. The relative MR effect for both samples showed decreasing trend with the increment of strain amplitude and excitation frequency.

Abstract: This paper aims to investigate the damping properties of plate-like carbonyl iron particle (CIP) magnetorheological elastomer (MRE). The damping properties of MRE is mainly dependent on the strength of magnetic field. Anisotropic MRE was fabricated under various magnetic fields strength (70, 210, 345, and 482 mT) and its damping property prior to frequency-dependent was measured using a rheometer. Firstly, the plate-like CIP was first synthesized from spherical CIP using a ball-milling method. The microstructure of plate-like CIP was observed using low vacuum scanning electron microscope. Subsequently, two types of MREs which are isotropic and anisotropic were fabricated using 70 weight percent (wt.%) of plate-like CIP. The experimental results showed that the anisotropic MRE has lower damping factor than isotropic MRE. Meanwhile, the damping factor increases with the increase of frequency.

Abstract: Heat removal is a fundamental issue for continuous progress in the electronic industry and for the thermal management in electronic devices. Materials with high thermal conductivity may help in the elimination of excess heat more efficiently which is necessary for improving the device performance. Phosphorene is a 2D material that has been recently exfoliated mechanically. Using density functional theory, we presented the electronic, lattice dynamic, thermal and dielectric properties of phosphorene. It is found that sound velocity is larger along the zigzag direction signifying anisotropic thermal behaviour. The macroscopic dielectric constant calculated is also found to be anisotropic in nature. Finally, the variation of entropy and specific heat with temperature is obtained.

Abstract: The material replacement of component is often used procedure, which helps to reduce production costs, simplify manufacturing, improve functional properties of component and bring another benefits. In the last years, more and more metal parts are converted to plastic, also in the cases of mechanically loaded parts. For these special applications, the fibre reinforced composite plastics are successfully used. However, the mechanical properties of composite plastic are strongly dependent on the fibres orientation and following anisotropic behaviour. Moreover, the orientation of fibres is influenced by the conditions of the part production. Due to the number of these dependencies, the material conversion becomes a complex task which cannot be solved with analytical approach. Especially in case of complicated part geometry. In this study, the connection of two different numerical solvers was used for material conversion of a part from automotive industry. First, the new geometry of analyzed part was designed in order to compensate lower mechanical properties of plastic in comparison to metal. Next, the new part manufacturing was simulated and this way obtained anisotropic properties of composite plastic were described. Finally, the structural analyses of original metal and new composite plastic part with real anisotropic properties were performed to verify achievement of material conversion. The aim of this study is to demonstrate, how numerical analyses can help to predict an unexpected result.

Abstract: Optimum n-drift region of a 4H-SiC Junction Barrier Schottky Diode (JBS) was analyzed by simulation with consideration of the anisotropic impact ionization. According to the detailed simulations using SRIM and Sentaurus, model parameters of empirical equations were obtained through fitting, which showed that the anisotropic avalanche model (2D-ANISO) differs significantly from the 1-dimensional empirical model (1D-Cooper) and the old isotropic avalanche model (2D-ISO). These initial results suggested that the JFET resistance and anisotropic impact ionization should be taken into account during the optimization of a 4H-SiC JBS in which field crowding at the corner of p-grid causes higher reverse leakage current.

Abstract: The preparation of size- and shape- controlled metallic nanoparticles using biological methodologies is a noticeably stimulating research field due to their unique physicochemical properties. In this paper, biosynthesis of anisotropic AuNPs using Ampelopsis grossedentata extract and the effects of halide ions on the formation of AuNPs has been demonstrated. The sizes and morphologies of AuNPs were characterized by UV-vis-NIR spectrophotometer and Transmission Electron Microscopy (TEM). It showed that the shape, size and optical properties of AuNPs can be fine-tuned by varying the dosage of the vine tea extract. The presence of halogen ions has significantly influence the morphology of AuNPs during the synthesis process. Both of Br- and Cl- could produced nanoplates, whereas I- distorted the triangle nanoparticles to induce the formation of aggregated spherical ones.

Abstract: We investigate the effect of surface texturing on the light trapping properties of Silicon wafers as a function of reflection reduction and surface morphology. This was achieved by structuring a random square-based pyramids pattern on the surface of Silicon substrate using anisotropy etching. The light trapping effect was optimized for silicon solar cells by investigating the dependence of the silicon surface texturing on the process parameters such as etchant concentration, etching time and temperature. We study the surface morphology by analyzing the surface behaviour of the textured substrate using the atomic force microscope and scanning electron microscope. The results of roughness and optical reflection were obtained using the surface profiler and the UV/VIS the spectrometer respectively. In addition, an analytical modelling method was developed to determine the angles of incidence of light rays with each of the facets of the pyramids and the coordinate of the reflected light rays. The method used here is based on 3-D vector geometry of the pyramidal facets. The optimum parameters are found to be 40min, a temperature of 80^oC and with KOH/IPA/DI in the ratio [2:4:46] by volume, yielding a surface roughness over 600 nm and a relative optical reflectance in the visible spectrum less than 10%, using polished Si as reference. The results and analysis of both the modelled and measured reflectance, suggest that the performance of the light trapping technique has a big potential in silicon solar cells application.