Modified membrane finite element formulation for sheet metal forming analysis of planar anisotropic materials

A finite element formulation is derived for sheet metal forming analysis of planar anisotropic materials. The formulation incorporates membrane elements whereas it takes the bending effect into account explicitly. The strain energy term in the formulation is decomposed into the membrane energy term for mean stretching and the bending energy term for pure bending. This procedure needs careful evaluation for the orientation of the anisotropic axes. The formulation is then combined with an effective algorithm to calculate distribution of the blank holding force in each step according to the thickness in the flange region. The calculation employs a special relation between the thickness and the blank holding force. The simulation examples demonstrate the validity and versatility of the developed computer code by showing that the thickness variation in the flange region redistributes the blank holding force during the deformation. The present algorithm can predict accurate deformed shapes and thickness strain distribution with the anisotropy of materials and the variable blank holding force.     

Indoor UAV Control Using Multi-Camera Visual Feedback

This paper presents the control of an indoor unmanned aerial vehicle (UAV) using multi-camera visual feedback. For the autonomous flight of the indoor UAV, instead of using onboard sensor information, visual feedback concept is employed by the development of an indoor flight test-bed. The indoor test-bed consists of four major components: the multi-camera system, ground computer, onboard color marker set, and quad-rotor UAV. Since the onboard markers are attached to the pre-defined location, position and attitude of the UAV can be estimated by marker detection algorithm and triangulation method. Additionally, this study introduces a filter algorithm to obtain the full 6-degree of freedom (DOF) pose estimation including velocities and angular rates. The filter algorithm also enhances the performance of the vision system by making up for the weakness of low cost cameras such as poor resolution and large noise. Moreover, for the pose estimation of multiple vehicles, data association algorithm using the geometric relation between cameras is proposed in this paper. The control system is designed based on the classical proportional-integral-derivative (PID) control, which uses the position, velocity and attitude from the vision system and the angular rate from the rate gyro sensor. This paper concludes with both ground and flight test results illustrating the performance and properties of the proposed indoor flight test-bed and the control system using the multi-camera visual feedback.     

Characterizations of polybenzimidazole based electrochemical hydrogen pumps with various Pt loadings for H2/CO2 gas separation

Carbon capture and storage (CCS) technologies have been intensively researched and developed to cope with climate change, by reducing atmospheric CO₂ concentration. The electrochemical hydrogen pumps with phosphoric acid doped polybenzimidazole (PBI) membrane are evaluated as a process to concentrate CO₂ and produce pure H₂ from anode outlet gases (H₂/CO₂ mixture) of molten carbonate fuel cells (MCFC). The PBI-based hydrogen pump without humidification (160 °C) can provide higher hydrogen separation performances than the cells with perfluorosulfonic-acid membranes at a relative humidity of 43% (80 °C), suggesting that the pre-treatment steps can be decreased for PBI-based systems. With the H₂/CO₂ mixture feed, the current efficiency for the hydrogen separation is very high, but the cell voltage increase, compared to the pure hydrogen operation, mainly due to the larger polarization resistance at electrodes, as confirmed by electrochemical impedance spectroscopy (EIS). The performance evaluation with various Pt loadings indicates that the hydrogen oxidation reaction at anodes is rate determining, and therefore the Pt loading at cathodes can be decreased from 1.1 mg/cm² to 0.2 mg/cm² without significant performance decay. The EIS analysis also confirms that the polarization resistances are largely dependent on the Pt loading in anodes.     

Mechanical properties and morphology of the modified HDPE/starch reactive blend

We investigated the effect of reactive blending on the mechanical properties and morphology of high‐density polyethylene (HDPE)/plasticized starch blends. HDPE was chemically modified to enhance the compatibility with the plasticized starch. The modified HDPE, HDPE‐g‐glycidyl methacrylate (GMA), was synthesized by melt reaction of HDPE in the presence of dicumyl peroxide (DCP). A finer dispersion of starch in the HDPE matrix was achieved compared to that in the unmodified HDPE. The amount of GMA groups in the modified HDPE enhanced the miscibility of HDPE/starch blends. We also observed that the amount of glycerin improves the mechanical properties of blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3313–3320, 2001     

Measurements and correlation of hydrogen-bonding vapor sorption equilibrium data of binary polymer solutions

Vapor sorption equilibrium data of ten binary polymer/solvent systems were measured using sorption equilibrium cell equipped with a vacuum electromicrobalance. Tested solvents were water, methanol, ethanol and npropanol and polymer solutes were poly(ethylene glycol), poly(propylene glycol), poly(tetramethylene glycol) and poly(ethylene oxide). The measured sorption obtained in the present work, were compared with existing literature data and the degree of reliability of the measured data was discussed. Vapor sorption equilibrium data obtained in the present study were correlated by UNIQUAC model and the multi-fluid non-random lattice fluid hydrogen bonding equation of state (MF-NLF-HB EOS) recently proposed by the present authors.     

Synthesis,characterization, and comparative study of conducting polyaniline/lead titanate and polyaniline–dodecylbenzenesulfonic acid/lead titanate composites

To study the effect of a surfactant on the properties of polyaniline (PANI)/metal oxide composites, PANI/lead titanate (PbTiO₃) composites were synthesized with different weight percentages (10, 20, 30, 40, and 50 wt %) of PbTiO₃ in both the absence and presence of dodecylbenzenesulfonic acid (DBSA) by the polymerization of aniline with ammonium persulfate as an initiator. The structural characteristics and stability, surface characteristics, and electric properties of PANI/PbTiO₃ and PANI–DBSA/PbTiO₃ were studied and compared. The interfacial interactions and thermal stability of these composites were characterized with X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermogravimetry techniques. The results indicate significant changes in the physicochemical properties of the composites with the incorporation of DBSA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mode II interlaminar fracture behavior of carbon bead‐filled epoxy/glass fiber hybrid composite

To investigate the effect of including carbon beads on the mechanical properties of epoxy resin, the fracture toughness of carbon bead‐filled epoxy was earlier evaluated using a CT (compact tension) specimens and Mode I fracture toughness was observed. Based on those results, in this study, the Mode II interlaminar fracture toughness of carbon bead filled epoxy/glass fiber hybrid composites was evaluated using end notch flexure (ENF) specimens. The hybrid composites showed increased Mode II interlaminar fracture toughness. The optimal bead volume fraction was around 15%.     

Characterization and DC electrical conductivity of the composite films containing polyaniline‐carboxymethyl cellulose

New polymer composites containing polyaniline‐carboxymethyl cellulose (PANI‐CMC) were prepared via the polymerization of aniline hydrochloride using different concentration (wt%) of sodium CMC using ammonium persulfate as an oxidant. The thermal stability and embedded crystallinity of the composites were investigated using thermogravimetric and X‐ray diffraction analysis method, respectively. The electrical properties of the composites were examined using temperature‐dependent DC conductivity within 300–500 K. As compared to pure polyaniline the composites with increasing CMC in the PANI‐CMC composites shows the enhancement in the higher crystallinity and thermal stability, and higher electrical conductivities under equivalent conditions. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers