Papers by Keyword: Wear

Abstract: Consequences of the wear processes at screws and barrels of injection machines and extruders for processing of plastics reinforced with short glass fibers, arise after a longer time (10,000 cycles). Because of this they are working that through appropriate modeling attempts on the profits to be obtained in a short time as much information relating to both the mechanisms of wear and its size, so that the effect can be easily confuted in practice. Starting from the idea that the greatest pressure and velocity of composite melted is in the die nozzle, was an experimental nozzle with wear samples of sizes and weights which can be measured with precision as good. For a larger accuracy of measurements, we used a method for radiometric measuring, extremely accurate. Different nitriding steels have been studied as nitriding treatments, as well as some special steels and alloyed steels. Besides these, there have been preliminary attempts made to describe and checking corrosive action of termoplastelor on metals. This was another way of checking the wear testing of the samples semi-cylindrical wear samples, which served to simulate the wear of the top layer of the barrel and screw. The first results showed that wear increases depending on the increased pressure. One of the findings is that in similar conditions of injection, with the same content of glass fiber, polyamide 6.6 produces a wear greater than polycarbonate. It was also found that increasing the concentration of glass fibres increase the surfaces wear of barrels and screws.

Abstract: In the deep and ultra deep well casing wear is serious. The decrease of strength leads to casing damage, affects the follow-up well test and completion. In order to analyze the influence of the contact force, rotating speed, steel grade and muds on casing wear, determine the optimized level collocation scheme which makes casing wear minimum, optimize drilling parameters and casing programs, reduce casing wear, four factors and three levels orthogonal experiment of casing wear was carried out, and the range analysis of the experiment results is made. The results show that the best match of factors is A1B1C1D3, namely when the contact force is 200 N(A1), rotating speed 60 r/min (B1), steel grade N80(C1), oil-based mud (D3) casing wear is minimal. The influence of muds on casing wear is the largest, the next is casing steel grade, and then rotating speed, the effect of the contact force minimal. The improvement of mud performance is best method to reduce casing wear.

Abstract: This paper present new result for experimental analysis of air flow velocity and pressure distributions between two ducts bend: (1) 90° duct bend with a single turning vane having 0.03m radius and (2) 90° duct bend with double turning vane, in 0.06 × 0.06 m duct cross section. The experiment used five different Reynolds numbers chosen between the ranges 1 ×104 and 6×104. Each experiment has four point measurements: (1) point 1 and point 2 at cross section A-A and (2) point 3 and point 4 at cross section B-B. The first experimental study used single turning vane radius 0.03m with inlet air velocity from 2.5m/s to 12.2m/s. And for the second experiment that used square turning vane with 0.03m radius. In experiment 2, the inlet air velocity also start from 2.5m/s to 12.2m/s. From analysis results, the pressure drop in experiment 1 is higher than experiment 2. As example the maximum pressure drop at 7.5m/s inlet air velocity between point 1 and 3 was found to be 71.6203 Pa in experiment 1 as compared to 61.8093 Pa in experiment 2. The velocity after duct bend is greater when using double turning vane compare used single turning vane as maximum velocity at point 3 in experiment 2 compare to velocity at point 3 in experiment 1 that is 55.677× 10-4 m/s and 54.221× 10-4 m/s. The velocity at duct wall is equal to zero. When increase the value of Reynolds number or inlet velocity, the maximum velocity and total pressure also increase. For example in experiment 1 at point 1, the velocity is 48.785 × 10-4 m/s at Reynolds number 1 ×104 and velocity 65.115×10-4 m/s at Reynolds number 12.2 ×104 . Velocity flow in duct section are lower than inlet velocity. In experiment 1, the inlet velocity is 2.5m/s meanwhile the maximum velocity in the duct section at point 2 is 73.075×10-4 m/s that is much more lower than inlet velocity.

Abstract: A deep understanding of the mould flux effect on the wear mechanisms of Al₂O₃-C nozzles (AG) is relevant to avoid premature damage and to decrease the cost of black refractories in the industry. In this paper, a post mortem study on a nozzle was carried out to identify the causes of the wear mechanisms during the continuous casting of billets. Physical properties such as viscosity and surface tension of the mould fluxes were determined at operation temperature (1550oC), in order to correlate with microstructural results obtained by light and scanning electron microscopy (SEM). Also dihedral angle φ measurements were carried out at high magnification by SEM. Applying EDS analysis the infiltrated mould flux chemical composition was determined. The study was completed by EBSD. The EBSD technique contributed to increase the knowledge on wear mechanisms because of the possibility of identifying and localizing phases together with crystalline condition. The phases, the grain orientations and the properties of grain boundaries, have a large influence on the corrosion behaviour. Therefore, it is essential to have a characterization technique that can provide information such as: grain size, orientation, misorientation angle and the present phases. In this context, EBSD can provide relevant information on crystallographic and structural analysis of AG nozzle including the insert of ZrO₂-C.

Abstract: Copper-carbon composites are very promising functional materials used as electrical contact devices due to their high electrical conductivity, thermal conductivity and excellent wear resistance. In the present study the influence of carbon forms (including carbon nanotubes, graphite nanopowder and graphene) on the properties of copper matrix composites was examined. The composites were fabricated using the powder metallurgy method. The optimal parameters of the hot-pressing process in vacuum were fixed as follows: the temperature of 525°C, the pressure of 600 MPa and the time of 10 min. The wear tests were performed in dry conditions using an SRV (Schwingungs Reibung und Verschleiss) friction and wear tester in a reciprocating motion. The friction and wear behaviour of copper with 3 vol.% of carbon were investigated. Scanning electron microscopy (SEM) was used to analyse the worn surfaces and debris, and finally the wear mechanism was discussed.

Abstract: The influence of fullerenes on anti-friction, anti-wear, and scoring-resistance properties of lubricants is studied.

Abstract: The paper presents some aspects regarding tribological characteristics of composite tops of the electrodes for spot welding. The solution aims to improve the resistance to deformation and high intensity electric current conductibility without loses and excessive local heating. The composite material was obtained by mechanical alloying process, from a mixture of tungsten carbide, chromium, CuNiAl alloy and cooper powder which has been heated in furnace at 1100°C. The embedding process aims to avoid the toxic effects of metallic elements such as Be and Zr, which are usually introduced in cupper alloys for improving the mechanical characteristics. The tribological characteristics and microhardness of the melted zone were measured in order to estimate the strengthening effect obtained by the tungsten carbide presence for different mixture recipe.

Abstract: The characteristics, structure and applications of polyetheretherketone (PEEK) composites are introduced briefly. The research progress of friction and wear resistance properties of PEEK composites, modified by carbon fiber, other nanometer and micro-particles, are summarized. Suggestions for further research are put forward.

Abstract: The effects of micro-arc oxidation (MAO) voltage (370V, 400V, 420V) on the surface morphology, adhesion of film/substrate, corrosion resistance and fretting friction and wear properties after micro-arc oxidation and heat-treatment for 48h of TiNi alloy were investigated. The results show that, as the voltage gradually increases: (1) micro-arc oxidation coatings form, when the voltage increase to 420V, the coating shows a significant micro-arc oxidized porous characteristics; (2) the Ca/P ratio in the coatings also increases, so the Ca/P ratio can be controlled by adjusting the voltage of micro-arc oxidation; (3) the corrosion resistance of MAO coatings can be significantly improved by increasing the output voltage, the corrosion rate and the corrosion potential of 420V are smaller two magnitude than 370V’s; (4) the coating of 420V shows lower friction coefficient with higher resistance, narrower wear scar width; (5) the MAO coatings have formed different types of hydroxyapatite crystals (HA) after immersed in high temperature and pressure reactor for 48h, and the phase composition of the coating are mainly apatite.

Abstract: The titanium alloy (Ti-6Al-4V) coated with commercially pure (CP) Ti particles was fabricated by the laser cladding process. Coating quality was investigated by scanning electron microscopy and X-ray diffraction, while wear resistance of the alloys was evaluated on a ball-on-flat dry sliding wear tester at room temperature under a load of 25 N, frequency of 5 Hz and stroke length of 2 mm using three counterface materials (302 SS, Brass and WC). Mass loss of the laser cladded samples as well as the wear rate of each counterface material was calculated. SEM images revealed growth of acicular widmanstätten α, also known as α′ martensite, embedded in a prior β matrix at the coating-substrate interface. Smearing of Ti from the cladded samples was observed on the worn surfaces of the counterface materials except for brass which showed high material removal.