Wear behavior of a crankshaft journal bearing manufactured by powder spraying

A new crankshaft bearing material that can be an alternative to the traditional material has been improved and its wear behavior studied experimentally. Crankshaft main bearings are subjected to various stresses. A new material supposed to be adapted these operating conditions was designed composing of Pb–Sn–Cu–ZrO₂ and manufactured by HVOF spraying technique. Wear behavior of the bearing was tested with the simulation of real operating conditions. An original bearing was used for comparison. After a trial of 500 h, the weight losses were measured. SEM micrographs of both original and new bearings were examined. The effect of microhardness was discussed. The new composition was seen as promising as a bearing material for automotive engines.     

New organic semiconductor materials: electrical conductivity,thermal properties and application of voltage‐controlled negative resistance device of poly[(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐co‐(maleic acid)]

BACKGROUND: Electrical conductivity, photoconductivity, voltage‐controlled negative resistance and thermal properties of copolymers of 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid and maleic acid were investigated in order to obtain new organic semiconductors. RESULTS: The room temperature conductivity of three different copolymers was found to be in the range 1.28 × 10^?8 ? 1.20 × 10^?7 S cm^?1. The dark‐ and photo‐current‐voltage characteristics indicate that the copolymers exhibit voltage‐controlled differential negative resistance behaviour. The electrical conductivity of the polymers increases by photo‐illumination, suggesting that the polymers exhibit photoconductivity. The width of the exponential tail in the forbidden band gap of the three polymers was determined via the transient photocurrent technique and E₀ values were in the range 34.4–36.49 meV. CONCLUSION: The results suggest that the copolymers could be used as organic semiconductor materials. Copyright © 2007 Society of Chemical Industry     

Effects of the aluminum filler content on moisture diffusion into epoxy adhesives in distilled water and sea water

Epoxies are the most common of high‐performance structural adhesives, especially in automotive and aircraft manufacturing. In a variety of industrial applications, epoxy adhesives are required to have enhanced thermal conductivity. The normal method of changing this property is to add to the epoxy a filler of higher conductivity than the continuous phase. Although the improvement in the thermal properties of adhesives by the addition of metal fillers is obvious, their influence on water sorption characteristics of adhesives is not clear. It was the objective of this study to shed light on these aspects, which are lacking in the literature. The emphasis was placed on determining the moisture sorption behavior of aluminum‐powder‐filled epoxy adhesives under complete immersion in distilled water and sea water. Moisture diffusion tests show that the addition of aluminum filler into epoxy decreases the total amount of water intake at saturation in both fluids. However, there appears to be no significant effect of the aluminum filler content on the moisture diffusivity in epoxy adhesive specimens in either distilled water or seawater. It has also been determined that the adhesives adsorb a larger amount of water upon exposure to distilled water than when exposed to seawater, whereas the moisture diffusion rate in the adhesive immersed in seawater is higher than that in distilled water. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1165–1171, 2005     

Numerical prediction of three-dimensional fiber orientation in Hele-Shaw flows

A numerical technique is developed to determine the three-dimensional fiber orientation in complex flows. The fiber orientation state is specified in terms of orientation tensors, which are used in several constitutive models. This method is applied to quasi-steady state Hele-Shaw flows in order to predict the flow-induced fiber orientation during injection molding at zero volume fraction limit. At the inlet, a number of fibers are introduced at a specified rate into the flow and each fiber location is traced during the mold filling. Along these determined paths, the independent components of fourth order orientation tensors are solved, describing the orientation state. The numerical grid generation technique, which is suitable for complex mold shapes, is employed for the flow solution. Orientation ellipsoids are calculated from the second order tensors and are used to present the fiber orientation results. The numerical solutions are obtained for channel and converging flows. Planar, longitudinal, and transverse orientation results are generated from the orthogonal projections of the orientation ellipsoids.     

Surface Characterization of Mild Steel During Atmospheric Corrosion After Being Treated by Sodium Dihydrogen Orthophosphate

Protection of Metals and Physical Chemistry of Surfaces - The objective of this study was to characterize the surfaces of the steel products produced locally during their exposure to the industrial...     

Preparation and characterization of thermally conductive thermoplastic polyurethane/h‐BN nanocomposites

Polyurethane nanocomposites are versatile engineering polymers with unique properties. In this study, nano hexagonal boron nitride containing thermoplastic polyurethane elastomers were prepared via melt blending and hot‐pressing techniques. The nanocomposites were characterized using Fourier transform infrared, differential scanning calorimetry, thermal gravimetric analysis, tensile tests, and thermal conductivity measurements. The surface morphology of the TPU/h‐BN composites was characterized by scanning electron microscopy. The optical properties of the composites were determined by UV transmittance measurements and as the amount of h‐BN increased, optical transparencies decreased dramatically. Nanocomposites displayed higher E‐modulus values and lower elongation at break values than the pure TPU elastomer. Char yields of TPUs increased with increasing h‐BN percentage. Moreover, thermal conductivity of the composite materials improved with the incorporation of h‐BN. POLYM. COMPOS., 35:530–538, 2014. © 2013 Society of Plastics Engineers     

Studies on a terephthalic acid and dihydroxydiphenyl sulfone liquid crystalline copolymer and its composites with different thermoplastics

A liquid crystalline polymer (LCP) was synthesized by an interfacial polycondensation reaction at room temperature from terephthaloyl chloride and p,p′-dihydroxydiphenyl sulfone. The LCP synthesized was so stable and molecularly rigid that it did not show any phase transition until it degraded at about 320°C. Composites of the LCP with polycarbonate (PC), polystyrene (PS), and sulfonated polystyrene (SPS) were formed by compression molding at a temperature at which the thermoplastic matrix was in the melt state. They were thermally analyzed by differential scanning calorimetry. Tensile specimens were cut from the compression-molded plates, and mechanical tests were performed. The morphology of the material systems was studied by performing scanning electron microscopy analysis on cryogenically fractured specimens. For LCP/PS and LCP/SPS systems, a sharp two-phase morphology was formed, which suggested poor interfacial adhesion. The tensile strength of both systems decreased with LCP addition. The LCP/PC system also revealed a two-phase morphology; however, the interfaces between the LCP domains and the PC matrix were not so well defined, showing better interfacial adhesion than the two previous systems studied. Stronger bonding between the LCP and PC resulted in a significant improvement in the mechanical behavior of PC by LCP addition. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 645–652, 1997     

Numerical and experimental investigation of melting of ice involving natural convection

Two‐dimensional transient melting of ice in a rectangular enclosure was numerically and experimentally investigated. Natural convection in the liquid phase due to the temperature dependency of water density was considered in the numerical model. The implicit finite difference method with fixed staggered grid approach was utilized. The SIMPLER algorithm was followed for the solution of pressure and velocity fields in the liquid phase. The prediction of the model was found to be satisfactory through preliminary experimentation. Copyright © 2002 John Wiley & Sons, Ltd.     

Slurry analysis of cadmium and copper collected on 11-mercaptoundecanoic acid modified TiO2 core-Au shell nanoparticles by flame atomic absorption spectrometry

Separation/preconcentration of copper and cadmium using TiO(2) core-Au shell nanoparticles modified with 11-mercaptoundecanoic acid and their slurry analysis by flame atomic absorption spectrometry were described. For this purpose, at first, titanium dioxide nanoparticles were coated with gold shell by reducing the chloroauric acid with sodium borohydride and then modified with 11-mercaptoundecanoic acid. The characterization of modified nanoparticles was performed using ultra-violet spectroscopy and dynamic light scattering. Copper and cadmium were then collected on the prepared sorbent by batch method. The solid phase loaded with the analytes was separated by centrifugation and the supernatant was removed. Finally, the precipitate was slurried and directly aspirated into the flame for the determination of analytes. Thus, elution step and its all drawbacks were eliminated. The effects of pH, amount of sorbent, slurry volume, sample volume and diverse ions on the recovery were investigated. After optimization of experimental parameters, the analytes in different certified reference materials and spiked water samples were quantitatively recovered with 5% RSD. The analytes were enriched up to 20-fold. Limits of detection (N=10, 3σ) for copper and cadmium were 0.28 and 0.15 ng mL(-1), respectively.     

Multiple-toughening behaviour in SiC platelet-reinforced TZP/Al2O3 ceramic composites

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.