Abstract: Presently in rules for fatigue assessment of structures subjected to intensive alternating service loading the Stress-Life (S-N) criteria are recommended in versions of the Nominal stress approach, Hot-spot stress and Notch-stress approach based on using the stress range a representative of the current damage. The criteria and approaches provide assessment of fatigue properties of structures accompanied with a series of approximations and uncertainties. A physically and mechanically more correct procedures might be provided by the Strain-life and Inelastic strain energy criteria for fatigue failure and approaches, although specific with intrinsic sources of approximations. The nature of approximations in the approaches is briefly commented and feasible means of improvement the fatigue assessment procedures and applications are presented.
Abstract: In the paper were reviewed mechanical and chemical properties of the modern refractories applied in the metallurgical industry and was provided their classification for the goal of optimal selection of refractories kind for specific technological conditions, reducing costs and solving the environmental issues. For various applications in the steel industry, in the furnace linings for iron and steel making, metal and slag transport, heat treatment furnaces and the flues for the hot gas conduction, refractories are widely used. The refractories can also be classified according to the raw materials, which are used in the preparation and to the predominant minerals after production. Nowadays, hardly any standard bricks are used and there is a trend towards using monolithic refractories. Due to the improvement in the service life and highly productive modern steel making processes, the consumption of refractories is reduced.
Abstract: In this paper, the microstructural evolution of the composite formed by fibre laser deposition of Ti-6Al-4V wire and WC-W2C powder was investigated and reported. Nine single tracks were deposited using combinations of four laser processing parameters (laser power, traverse speed, wire feed rate and powder feed rate) with each having three levels based on Taguchi design of experiments. The samples of the deposited composites were subjected to microstructural examinations using scanning electron microscopy with energy dispersive spectroscopy and X-ray Diffractometry, and microhardness tests. The resultant microstructure is characterised by uniform distribution of the reinforcement particles (WC-W2C) and dispersion of in-situ synthesised TiC and W solid solution precipitates in a β-stabilised Ti matrix. The TiC precipitates have blocky and fine eutectic morphologies, while the W solid solution precipitates have blocky and leaf-like equiaxed morphologies. The retained W composition in the β-Ti was found to range from 7.5-9 at%, and it helped to β-stabilise the matrix which was considered beneficial for the composite matrix to retain its ductility. Increasing laser power was found to decrease the amount of W retained in the Ti matrix which resulted in a lower cooling rate, favourable for the nucleation of W solid solution. The uniform dispersion of the TiC and W solid solutions in the β-Ti matrix phase has significantly enhanced its hardness which ranged from 455-543 HV0.3. It is anticipated that the composite formed will possess excellent wear resistance and contact deformation characteristics.
Abstract: The present work investigates a hybrid nano-coating based on permanganate/fluoride/glycerol conversion coating solution on aluminium alloy, AA6061. From gravimetric studies, the nano-coatings formed on aluminium alloy by immersion procedures developed rapidly at a rate which decreased with time of treatment and was about 5 gm-2 after a period of three minutes. The morphology of the coating from scanning electron microscopic (SEM) examinations revealed randomly shaped coating materials with mud cracking patterns, characteristics of dried out coatings derived from gel-like materials. Analyses of the coating with the energy dispersive analysis of X-ray spectroscopy (EDS) attachment in the SEM revealed the composition as compounds of aluminium, oxygen and manganese, probably hydrated. The corrosion resistance of the coating out-performed ‘bare’ aluminium alloy specimens exposed to both natural and 3.5% sodium chloride solution environments. The coating improved the paint adhesion characteristics of the substrate aluminium alloy. Macro and micro features developed on the substrate aluminium are anchor points which improved the adhesion of subsequently applied lacquer.
Abstract: Magnetite’s abilities rely on the quantitative phases present in the sample. Magnetite quality can strongly influence several physical properties, such as magnetism, catalytic performance, and Verwey transition. However, differentiation of magnetite and maghemite through the conventional X-ray diffractogram comparison are not relevant for the intermediate phases. In this study, the deviation from the ideal stoichiometric magnetite and the relative quantification of both phases were mathematically achievable through a new XRD technique. Various synthesis conditions were applied to obtain different crystallite sizes, in the range of 9 to 30 nm. Generally, the stoichiometric deviation and maghemite content would be significantly influenced by the final size, whereas system conditions (temperature of solution, agitation rate, and pH of solution) would only have minor significance. In this study, iron oxide nanoparticles prepared using the co-precipitation method was calculated to contain 100% magnetite for particles of 30.26 nm in size, while 100% maghemite was calculated for particles at 9.64 nm.
Abstract: In the present work, 2% and 6% carbon nanotubes (CNT) were reinforced in chromium oxide powder and were deposited on T22 steel using high velocity oxy-fuel spraying process. The effect of CNT reinforcement on hardness and porosity was investigated. The hardness was observed to be highest for coating reinforced with 6%CNT and hardness was found to increase with decrease in porosity. The coating microstructure and elements were characterised using field emission scanning electron microscopy (FE-SEM) with energy dispersive spectroscope (EDS), Elemental point analysis and X-ray mapping analysis. The constituents of the coating were identified using X-ray diffractometer. It was found that the CNT were uniformly distributed throughout Cr2O3 matrix. The CNT were found to be chemically inert during the spraying process.
Abstract: Electrospinning has become the most popular nanofibers production technique that many scientists around the world were intrigued by. It is based on electrostatic forces stretching a polymer solution that undergoes bending instability and eventually results in number of fine nanoscaled filaments. The study reports of four processing parameters effect on electrospun polyethylene oxide (PEO) fibers diameter and pores area. Fibers diameter increase results from the increase of time, volume flow rate and tip to collector distance with a critical value of the first two parameters. The pores area showed both decrease and increase after a critical value of the electrical voltage at 19 kV, while the mean pores area decreased with the time increase. Irregular trends of increasing and decreasing trends of the means pores area were noticed with the change of the volume flow rate and tip to collector distance..
Abstract: In this article we have used new anticorrosion investigating techniques and studied new polarization resistance aspects of anticorrosion mechanism of cucurbit [n] urils and thioglycolurils based inhibitors in aggressive acid and alkaline containing chloride mediums. Results suggest that the active complex of inhibitor with iron is non-soluble and stable in aggressive mediums.
Abstract: The purpose of this investigation is to clarify the behavior of exit keyhole diameter during switch off (cutting arc) period in case of Plasma keyhole arc welding (PKAW). During switch off period, the keyhole and weld pool are visualized from backside via a high speed video camera (HSVC). The result showed that keyhole diameter on the backside is unstable. The keyhole size is much changed in X-axis. Firstly, it is increased and then it is decreased to a stationary value at t = 0.05 s after cutting arc. Meanwhile, the size in Y-axis is not changed approximately from t = 0.01 s after cutting arc. The results can be considered to control this process more efficiency.