Metallurgical and tribological investigations of aluminium bronze bushes made by a novel centrifugal casting technique

Aluminium bronzes have been used as high strength, corrosion and wear resistance alloys for many decades. However, the alloy has a narrow solidification range and a complex nature which has confined its use to a limited field of applications. Published data on the wear characteristics and the metallurgical nature of the alloy system is limited, leaving wide possibilities for research. In the work described in this paper a study has been made of the metallurgical and tribological characteristics of aluminium bronzes conforming to BS 1400 AB2 specification. A novel centrifugal casting technique using a bonded sand lining integrated into a standard rotating die was adapted to cast a series of test bushes. Mechanical and microscopic aspects are studied and an attempt is made to correlate the physical properties with the tribological behaviour of the bushes. The results show that the test behaviour of the test bush was in some respects better than that of commercially produced bushes made by forging techniques. Detrimental embrittlement, due to ‘self annealing’ is significantly reduced by the adoption of the novel centrifugal casting technique referred to above.     

Drinking tastes of Chinese rice wine under different heating temperatures analyzed by gas chromatography–mass spectrometry and tribology tests

Drinking tastes and lubrication properties of Chinese rice wine (CRW) under different heating temperatures were studied by tribology tests, gas chromatography–mass spectrometry (GC–MS) and sensory evaluations. CRW's drinking tastes were evaluated by taste panelists. Flavor compounds were detected by GC–MS. Lubrication properties of CRW were measured by tribometer. Drinking tastes changed under different heating temperatures and were the best at 60°C assessed by panelists. Four key compounds, furfural, benzaldehyde, butanedioic acid diethyl ester, and phenylethyl alcohol, were determined by GC–MS affecting drinking tastes of CRW. Their variation trends were consistent with the changes of CRW's tastes. The variation of CRW's lubrication properties had a positive correlation with that of CRW's taste, especially astringency. The lowest friction coefficient implied the best lubrication performance and taste at 60°C. Therefore, it was possible to rapidly evaluate drinking tastes of CRW using tribology technology based on the results. Reasons for temperatures influencing CRW's lubrication properties and drinking tastes were also analyzed in this study.     

Commercial white paint as back surface reflector for thin-film solar cells

In this work, commercially available white paint is applied as a pigmented diffuse reflector (PDR) on the rear surface of thin-film crystalline silicon (c-Si) solar cells with a silicon thickness in the 1–2 μm range. We show that white paint increases the short-circuit current density of the solar cells enormously, with a boost of 41% observed for very thin planar solar cells illuminated with the global AM1.5 solar spectrum. We also show that white paint is a better back surface reflector (BSR) than aluminium, air, a transparent conductive oxide (TCO)/aluminium stack, and even a detached aluminium mirror. While previous studies have investigated the influence of PDRs on silicon solar cells with thicknesses of over 27 μm, this work closes the gap that has existed for much thinner cells.     

Nanometer Scale Chemomechanical Characterization of Antiwear Films

We report the first nanometer scale chemical and mechanical (chemomechanical) characterization of selected features of a tribologically derived zinc dialkyl-dithiophosphate (ZDDP) antiwear film. AFM permits identification of the features responsible for preventing wear. These features are identified by nearby microscale fiducial marks, and their mechanical properties are determined by imaging nanoindentation. The same features are then studied by X-ray photoelectron emission microscopy (X-PEEM), which provides both elemental and chemical information at 200 nm spatial resolution. The mechanical properties are then determined for the same features, which are formed of a polyphosphate glass. This information provides new insights into the mechanisms by which ZDDP antiwears films are effective at inhibiting asperity contact between two metal surfaces     

Torsion Tribological Behavior of Polytetrafluoroethylene Composites under Dynamic Normal Load: Effect of Dynamic Normal Load Amplitude

The torsion tribological behavior of polytetrafluoroethylene (PTFE) composites was investigated under different dynamic normal loads. The difference between the shapes of T–θ curves under static and dynamic normal loads indicates that the torsion regime was affected by the dynamic normal loads. Dynamic loads not only produced new frequency components but also enhanced the amplitude of frequency components produced by the static load. The biaxial dynamic stress and transformation of the torsion regime under dynamic loads produce higher wear than that of a static load. The wear mechanisms under static and dynamic loads are abrasive wear and adhesive and fatigue wear, respectively.     

Modified falex testing: A tool for understanding the compound layer capabilities

The usefulness of Falex testing in assessing the scuffing resistance of nitrocarburized steel was established by carrying out tests on treated medium-carbon and hot-working steel specimens. Though the test could be employed as a quality control measure for the compound layer thickness, it was found inadequate in bringing out the subtle variations in the compound layer characteristics of specimens of different steels. By a modified form of Falex testing, the heat resisting ability of the compound layer of different steels could be distinctly brought out.     

Fractal characterization of wear-erosion surfaces

Wear erosion is a complex phenomenon resulting in highly distorted and deformed surface morphologies. Most wear surface features have been described only qualitatively. In this study wear surfaces features were quantified using fractal analysis. The ability to assign numerical values to wear-erosion surfaces makes possible mathematical expressions that will enable wear mechanisms to be predicted and understood. Surface characterization came from wear-erosion experiments that included varying the erosive materials, the impact velocity, and the impact angle. Seven fractal analytical techniques were applied to micrograph images of wear-erosion surfaces. Fourier analysis was the most promising. Fractal values obtained were consistent with visual observations and provided a unique wear-erosion parameter unrelated to wear rate.     

Effect of experimental parameters on the high-stress abrasive wear behavior of steels and a software package for its prediction

The effect of different experimental factors on the high-stress abrasive wear properties of steels has been studied. A correlation among the factors has been established by linear regression analysis. A computer software in Microsoft Basic language utilizing linear regression analysis has been developed with the capability of predicting the wear response of steels from the experimental factors.