Nonlinear static response of laminated composite plates by discrete singular convolution method

In this paper, large deflection analysis of laminated composite plates is analysed. Nonlinear governing equation for bending based on first-order shear deformation theory (FSDT) in the von Karman sense is presented. These equations have been solved by the method of discrete singular convolution (DSC). Regularized Shannon’s delta (RSD) kernel and Lagrange delta sequence (LDS) kernel are selected as singular convolution to illustrate the present algorithm. The effects of plate aspect ratio, fiber orientation, boundary conditions, thickness-to-side ratio, and applied load on the nonlinear static response of the laminated plate are investigated.     

Properties of geopolymer from circulating fluidized bed combustion coal bottom ash

Compressive strength, atomic ratios and microstructure of geopolymer mortars (GM) made from circulating fluidized bed combustion (CFBC) coal bottom ash (CBA) were investigated to observe the effect of air curing at ambient temperature (AC) at 20 °C and 90% RH, dry curing (DC) at 80 °C and 40% RH for 20 h. The 28-d compressive strength of GM exposed to AC (GM-AC) and DC (GM-DC) were 26.23 and 24.14 MPa, respectively. The Si/Na atomic ratio of the main reaction product (N-A-S-H gel) was close to 1. Geopolymer gel (apparently crystalline) having low Si/Na ratio (0.5) may correspond to a more advanced or developed stage of the aluminosilicate gel. It was observed that the geopolymerization was completed before the N-A-S-H gel formed when Si/Na ratio of GM is close to 2. The color of the GM changed from pink to grey and the structure became denser with almost no pores, when the temperature increased from 400 to 800 °C. The N-A-S-H gel became more amorphous due to the sintering reactions attaining Si/Al and Si/Na ratios of 4.54 and 0.98, respectively.     

Mechanical Properties of BSCCO Superconductor by Oliver–Pharr Method and Work of Indentation Approach

Polycrystalline superconducting Bi–Pb–Gd–Sr–Ca–Cu–O bulk samples with nominal composition Bi_1.7Pb_0.3?x Gd _x Sr₂Ca₃Cu₄O_12+y (x=0.00,0.01,0.05) were produced by the melt quenching method. The mechanical properties of the samples were characterized by depth sensing indentation technique under different peak loads ranging from 200 to 1800 mN. The experimental data were comparatively analyzed by the Oliver–Pharr method and a work of indentation approach. It was found that the work of indentation approach gave more reliable results because of the reducing pile-up effect. The results implied that both microhardness and reduced elastic modulus increased with increasing Gd substitution.     

Electrical characteristics of Al/polyindole Schottky barrier diodes. I. Temperature dependence

In this study, the forward and reverse bias current–voltage (I–V), capacitance–voltage (C–V), and conductance–voltage (G/ω–V) characteristics of Al/polyindole (Al/PIN) Schottky barrier diodes (SBDs) were studied over a wide temperature range of 140–400 K. Zero‐bias barrier height Φ_B0(I–V), ideality factor (n), ac electrical conductivity (σ_ac), and activation energy (E_a), determined by using thermionic emission (TE) theory, were shown fairly large temperature dispersion especially at lower temperatures due to surface states and series resistance of Al/PIN SBD. I–V characteristics of the Al/PIN SBDs showed an almost rectification behavior, but the reverse bias saturation current (I₀) and n were observed to be high. This high value of n has been attributed to the particular distribution of barrier heights due to barrier height inhomogeneities and interface states that present at the Al/PIN interface. The conductivity data obtained from G/ωV measurements over a wide temperature range were fitted to the Arrhenius and Mott equations and observed linear behaviors for σ_ac vs. 1/T and ln σ_ac vs. 1/T^1/4 graphs, respectively. The Mott parameters of T₀ and K₀ values were determined from the slope and intercept of the straight line as 3.8 × 10⁷ and 1.08 × 10⁷ Scm^?1K^1/2, respectively. Assuming a value of 6 × 10¹² s^?1 for ν₀, the decay length α^?1 and the density states at the Fermi energy level, N(E_F) are estimated to be 8.74 Å and 1.27 × 10²⁰ eV^?1cm^?3, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Gilbert Damping Constant of Quaternary Co2MnAl1?x Sn x Heusler Alloy Thin Films

Polycrystalline quaternary Co₂MnAl_1?x Sn _x films with x=0.25, 0.5, 0.75,?1 were prepared at room temperature using magnetron sputtering technique on SiO₂ substrates and post-annealed at various temperatures. We investigated the crystal structures, magnetic properties, and magnetic damping constants (??) of the prepared films. Out-of-plane angular dependences of the resonance field and the linewidth of the ferromagnetic resonance spectra were measured and analyzed using the Landau?CLifshitz?CGilbert equation to determine the magnetic properties and damping constant. Co₂MnAl_0.75Sn_0.25 and Co₂MnSn films had A2 ordered crystal structure while Co₂MnAl_0.25Sn_0.75 and Co₂MnAl_0.5Sn_0.5 films had A2 ordering up to 400?°C and 300?°C annealing temperature, respectively, and they had B2 ordering for the remaining temperatures. Also the crystal structure deteriorated at 600?°C for all of the film systems. The saturation magnetization, M _S , of films increased with annealing temperature till 400?°C except Co₂MnAl_0.5Sn_0.5 in which M _S increased till 500?°C, which is consistent with the structural analysis. The effective magnetization was obtained from the FMR spectra and it was found that it decreased with increasing Sn-concentration and reached a minimum value at Co₂MnAl_0.25Sn_0.75 composition. Lastly, Co₂MnAl_1?x Sn _x films annealed at 500?°C showed the best crystal ordering. The lowest ?? value was 0.008 and obtained from Co₂MnAl_0.5Sn_0.5 films annealed at 500?°C.     

Evaluation of gas nitriding process with in-process variation of nitriding potential for AISI H13 tool steel

Gas nitriding under controlled nitriding potential represents one of the important factors in enhancing the service life of dies used in the industry for hot aluminum extrusion. In the present study, AISI H13, a typical material used for hot extrusion dies, is gas nitrided using automated two-stage controlled nitriding process. Prior heat treatment on the material was carried out under the same controlled environment as used for hot extrusion dies to avoid any decarburization. The nitrided layer has been characterized using different techniques including optical microscopy, SEM, XRD, EDS, and microhardness analysis. It was found that controlled nitriding with in-process variation of nitriding potential can efficiently be used to control the morphology of compound layer and diffusion zone, effective case depth, case hardness, and quality of nitrided layer at sharp edges for better die performance. All the results were found in close agreement with established specifications required for improved die performance.     

Novel Type of Metal-Containing Polyimides for the Heck and Suzuki–Miyaura Cross-Coupling Reactions as Highly Active Catalysts

Novel palladium (II)-containing polyimides with exceptional catalytic properties for the Heck and Suzuki–Miyaura cross-coupling reactions were prepared from Pd(II)--bis(imine) complex and the corresponding dianhyrides. The glass transition temperatures (T _g ) of the polymers ranged from 169 to 241°C. The temperatures at which 10% weight loss occurred in air ranged from 415 to 579°C. Polyimides based on the palladium (II) complex were tested for catalytic activity in the Heck coupling reaction between styrene and several aryl halides and the Suzuki coupling reaction between phenylboronic acid and several aryl halides. The negative effects (e.g., expense, low reaction rates, air-sensitivity) experienced by using phosphines, particularly electron-rich phosphines, as catalysts in large scale applications is overcome by using polymer supported catalysis.     

A Study of Laser Melting and Rapid Solidification of an NbAl3 Alloy

The present study examines the laser rapid solidification of NbAl₃ alloy. The heat transfer process that occurs during heating, melting and solidification is studied theoretically, and the computed cooling rate corresponding to laser pulse is used to control the solidification process. Cross-sections of the solidified zones are examined using an SEM technique. Laser melting is carried out under different pressures of oxygen. The laser melting is shown to improve the ductility of the substrate through the change of dual phase structure of NbAl₃ to a three phase structure.