Analysis of the Fretting Conditions in a Contact Between an Epoxy Thermoset and a Glass Counterface

The fretting conditions in a contact between an epoxy thermoset and a glass counterface have been investigated using a specific device which allows in situ observation of the contact area. The critical displacement for transition from partial slip to gross slip conditions was investigated by the in situ detection of the micro-displacements and by the analysis of the fretting loops. Experimental results were in good relation with the theoretical predictions derived from Mindlin's approach of incipient sliding. Depending on the loading conditions, a progressive change from gross slip to partial slip conditions was found to occur during the early stages of the fretting loading, i.e., before the appearance of any macroscopic damage such as cracking or particle detachment. These fretting conditions were synthesized in a fretting map giving the boundary between various fretting regimes as a function of the normal load, the imposed displacement and the number of cycles.     

Comparative Study of Corrosion Inhibition on Mild Steel in HCl Medium by Three Green Compounds: Argania spinosa Press Cake, Kernels and Hulls Extracts

Argania spinosa press cake, kernels and hulls extracts are excellent corrosion inhibitors for steel. In this work electrochemical methods are used to study the inhibition of corrosion on steel in 1 M HCl. It has shown that Argan press cake, kernels and hulls extracts suppress both the anodic and cathodic process and they behave as mixed-type inhibitors. The inhibition efficiency was found to increase with inhibitors content. Data obtained from EIS measurements, were analyzed to model the corrosion inhibition process through appropriate equivalent circuit model; a constant phase element has been used. The values of the inhibition efficiency calculated from these techniques are in reasonably good agreement. The adsorption isotherm of natural compounds on the steel surface was found to obey Langmuir’s adsorption isotherm.     

Thermodynamic effect on the bending response of elastic foundation FG plate by using a novel four variable refined plate theory

This article deals with the study of the thermodynamic behavior of functionally graded material plates resting on two-parameter elastic foundation. An analytical solution based on a new shear refined deformation theory is presented. The displacement field used in the present refined theory contains undetermined integral forms and involves only four unknowns to derive. The plate is assumed simply supported and subjected to two different temperatures fields across its thickness. The mechanical characteristics of the plate are assumed to be varied across the thickness according to a simple exponential law distribution. The governing equations and boundary conditions are derived using the principle of virtual displacements and Navier solution technique is adopted to derive analytical solutions. A detailed numerical study of the present new refined theory is carried out to examine the influence of the time’s parameter, foundation’s parameters and deflection on the bending response of the FG plate.     

Thermal buckling analysis of functionally graded sandwich plates

Thermal buckling of functionally graded sandwich plates are presented in this article. Two common types of FGM sandwich plates, namely, homogeneous face layers with FGM core and FGM face layers with homogeneous core are considered. Material properties and thermal expansion coe?cient of FGM layers are assumed to vary continuously through-the-thickness according to a simple power-law distribution in terms of the volume fractions of the constituents. Equilibrium and stability equations of FGM sandwich plate with simply supported boundary conditions are derived using the higher-order shear deformation plate theory. The influence of the plate aspect ratio, the relative thickness, the gradient index, and the thermal loading conditions on the critical buckling temperature of FGM sandwich plates are investigated. The thermal loads are assumed to be uniform, linear, and nonlinear distribution through-the-thickness. A new simple solution for thermal buckling of FGM sandwich plates under nonlinear temperature rise is presented.     

Experimental Investigation of a Bubbly Two-Phase Flow in an Open Capillary Channel under Microgravity Conditions

The study of a bubbly laminar two-phase flow in an open capillary channel under microgravity conditions was conducted aboard the sounding rocket, Texus-45. The channel geometry, the liquid (FC-72) and the experimental conditions were chosen based on an analysis for application toward liquid management in space. The channel consists of two parallel plates that were b = 25 mm wide and separated by a distance of a = 10 mm. The flow along the length l = 80 mm is bounded by a free surface on one side and a plate on the opposite side. Bubbles are injected at the inlet of the capillary channel via six capillary tubes. The features of the gas injection were chosen with regard to the required bubble size, the injection frequency, and the gas and liquid flow rates. Different liquid and gas flow rates were tested leading to a volumetric quality ranging between 0.07 and 0.11. The experimental results show the interaction among bubbles and with the liquid free surface.     

Graphical determination of network limits for wind power integration

A graphical method is presented for determining the capability of individual system nodes to accommodate wind power generation. The method is based upon constructing a capability chart for each node at which a wind farm is to be connected. The capability chart defines the domain of allowable power injections at the candidate node, subject to constraints imposed by voltage limits, voltage stability and equipment capability limits being satisfied. The chart is first derived for a two-bus model, before being extended to a multi-node power system. The graphical method is employed to derive the chart for a two-node system, as well as its application to a multi-node power system, considering the IEEE 30-bus test system as a case study. Although the proposed method is derived with the intention of determining the wind farm capacity to be connected at a specific node, it can be used for the analysis of a PQ bus loading as well as generation.     

A theoretical investigation on the properties of the new poly(N‐vinylcarbazole)‐3‐methylthiophene (PVK‐3MeT) synthesized graft copolymer

In this article, we present quantum chemical calculations, based on density functional theory (DFT), performed to investigate the geometries and the opto‐electronic properties of a new synthesized graft copolymer based on poly(N‐vinylcarbazole) (PVK) and poly(3‐methylthiophene) (PMeT) named PVK‐3MeT. First, we have theoretically computed and compared the structural, optical, and vibrational parameters of both neutral and doped states. In addition, the excited state was theoretically obtained by the ab initio RCIS/STO‐3G method. To assign the absorption and emission peaks observed experimentally, we computed the energies of the lowest singlet excited state with the time‐dependent density functional theory (TD‐DFT) method. Electronic parameters such as the HOMO‐LUMO band gap, the ionization potential (IP), and electron affinity (EA) are extracted. Calculations show that the PVK‐3MeT copolymer is nonplanar in its ground neutral state. Meanwhile, upon doping or photoexcitation, an enhancement of the planarity is observed, resulting on a decrease of the inter‐ring torsion angle between 3‐methylthiophene units. Such modifications in the geometric parameters induce a dramatic change on the HOMO and LUMO orbitals in the doped or excited states. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Highly Conductive,Scalable, and Machine Washable Graphene‐Based E‐Textiles for Multifunctional Wearable Electronic Applications

Graphene‐based textiles show promise for next‐generation wearable electronic applications due to their advantages over metal‐based technologies. However, current reduced graphene oxide (rGO)‐based electronic textiles (e‐textiles) suffer from poor electrical conductivity and higher power consumption. Here, highly conductive, ultraflexible, and machine washable graphene‐based wearable e‐textiles are reported. A simple and scalable pad?dry?cure method with subsequent roller compression and a fine encapsulation of graphene flakes is used. The graphene‐based wearable e‐textiles thus produced provide lowest sheet resistance (≈11.9 Ω sq^?1) ever reported on graphene e‐textiles, and highly conductive even after 10 home laundry washing cycles. Moreover, it exhibits extremely high flexibility, bendability, and compressibility as it shows repeatable response in both forward and backward directions before and after home laundry washing cycles. The scalability and multifunctional applications of such highly conductive graphene‐based wearable e‐textiles are demonstrated as ultraflexible supercapacitor and skin‐mounted strain sensors.     

Analysis of the Dynamic Behavior of Magnetorheological Elastomer Composite: Elaboration and Identification of Rheological Properties

Silicon - The present work is devoted to experimental analysis of the magnetorheological elastomer composite behavior under dynamic loading. The elastomer is charged to 40% of ferromagnetic...