Papers by Keyword: Coefficient of Friction

Abstract: The article pesents the drawing process of the circular cross-section rod. The mechanical model of plastic deformation in the process of wire drawing is represented by the regularities of yielding of metal at the level of forward flow during the rolling based on theoretical solutions proposed by A. I. Tselikov. The method for determination of drawing forces was probed about by decomposing it into two problems of planar deformation and the superposition of these solutions. The results of the theoretical solution of wire drawing task were used to determine the coefficient of friction during the deformation of low carbon steel in diameter 5.5 mm by means of comparison with the known experimental results of the wire drawing efforts. Satisfactory results were obtained for evaluation of frictional forces during deformation under high plastic deformation zone conditions. The obtained values of friction coefficients can be used to solve the wire drawing tasks and under conditions of a high hearth of plastic deformation as well.

Abstract: A major challenge in the manufacture of films for polymeric packaging is the definition and setting of the friction coefficient (FCO) for the film surfaces. The FCO values are established with the incorporation of additives during the processing of the polymeric films. But, the homogenization of these additives in the polymeric matrix is very difficult. The additives have different polarity that the matrix polymeric and not are mixable. So, these additives migrate for the surface of the polymeric films easily. Several molecules are used as sliding additives, but among the most efficient are the amides molecules, highlighting the erucamide. This molecule promotes the decrease of the FOC but due its quick migration for the polymeric film surface provides numerous problems for the manufacture of the polymeric packaging and during its application as the product. In this work a nanocomposite (MMT-ERU) was obtained by an intercalation process to improve the compatibility between the polymeric materials and the erucamide molecules. The results shown in this work refers to the studies about the intercalation processes of the erucamide molecules into nanoclays (montmorillonite) to obtain the nanocomposite MMT-ERU. The effect of the temperature and the percentage of the nanoclay in the intercalation processes were studied. The results of x-ray diffraction and differential scanning calorimetry shown that erucamide molecules were intercalated in the nanoclay structures and that intercalation efficiency depends positively of the temperature and percentage amount of the nanoclay in the reaction medium.

Abstract: In tribological analysis of machine elements (such as gears, ball/roller bearings etc.), surface roughness plays very important role, ultimately it affects the friction coefficient, wear, rolling contact fatigue (micro pitting) and other failure mechanisms. Surface geometry and topography changes with time (number of cycles) during rolling/sliding motion of contacting surfaces. So, it is important to show the variation of surface topography parameter during wear process. This work presents the evolution of roughness parameters, wear and friction coefficient during pin-on-disc tribotesting under dry condition. The test is performed using pin on disc apparatus under room temperature condition. The pin (25mm long, 6mm diameter) is made of medium carbon steel (AISI 1038) whereas the disc (165mm diameter, 8mm thickness) is made of high carbon steel (SAE 52100). This works demonstrates the potential of Artificial Neural Network (ANN) for prediction of roughness parameters, friction coefficient and wear coefficient. Experimental results obtained from wear testing are compared with those obtained using artificial neural network (ANN) analysis. A very good agreement in results suggests that a well trained neural network is capable to predict the parameters in wear process.

Abstract: This study examined the optimal abrasive wear performance of kenaf-reinforced polymer composite under different sliding conditions. Three different fiber loadings i.e. 43.05, 49.30 and 55.33 vol.% of kenaf fiber was reinforced into a polyester resin using the pultrusion technique. Optimal responses of wear rate and average coefficient of friction (COF) for kenaf fiber-reinforced polyester composites, based on different levels of control factors (fiber loading, applied load, counterface roughness and sliding speed) were determined by the Taguchi Design of experiment (DOE) with L₉ (3⁴) orthogonal array and Analysis of variance (ANOVA) methods. The wear behaviour of kenaf fiber-reinforced composites were investigated using DUCOM pin-on-disc tester with three levels of applied loads (10-30 N), sliding speeds (0.42-1.3 m/s) against different grit sizes of silicon carbide abrasive papers (average grain size~2.2-25.2 μm) under dry sliding condition. The optimization of S/N ratio and degree of significance of the control variables to minimize the wear rate and average COF of kenaf fiber-reinforced polyester composites was carry out. The results showed that the counterface roughness is the most significant factor in affecting the wear rate, followed by applied load, sliding speed, and fiber loading. For average COF, the fiber loading is the most significant factor followed by applied load, sliding speed and counterface roughness.

Abstract: This paper introduces new damage criteria for cutting process analyses based on the Coulomb-Mohr theory. When the accumulated damage reaches a certain critical level, brittle fracture occurs close to the tool tip, which is affected by the hydrostatic pressure and the location of conventional failure plane. The position of this plane is determined by the geometry of the cutting tool and the angle of friction. Numerical validation of the proposed criteria was made by FE-method in the Deform 2D using user routine usrdmg (User defined damage models).

Abstract: The present research paper covers statistical analysis of the major tribological factors affecting the dry sliding wear behavior of Tungsten Carbide (WC) and Chromium Carbide (Cr-C) coatings on plain carbon P/M steel substrate using High Velocity Oxy Flame (HVOF) Coating Technique. Experiments were conducted on pin-on-disc wear testing equipment. The various parameters related to wear such as wear rate, Coefficientof Friction of the coated Disc, Hardness and Surface Roughness were measured.In comparison, WC and Cr-C coating, WC coating has comparably good effect.

Abstract: Hot stamping process has been developed to produce the steel automobile parts with an ultra-high-strength of 1500 MPa. The effect of scale thickness on the formability in hot stamping was investigated by a hot deep drawing test in our previous research. The draw-in lengths of flange increased with decreasing the scale thickness. It is supposed that thin scale thickness resulted in low coefficient of friction at the flange area. The other reason is the temperature of wall zone would become low according to decreasing the scale thickness or increasing of the thermal transfer coefficient and it slightly inhibits local deformation at the wall area. It is difficult to separate these phenomena. To quantify the effect of scale thickness on the friction at the flange area during hot deep drawing, the coefficient of friction was directly measured. The coefficient of friction decreases with decreasing scale thickness.

Abstract: The wearing of bush made of brass in various applications is a cause for major concern. This study aims to analysing the various causes, mechanisms, environmental effects that influence the wearing and reduction in efficiency of the brass-steel sliding pair. The anti-friction and anti-wear properties are analysed under various conditions using a multitude of approaches. The particulate size of the dispersed lubricant (graphite and nanographite) and the temperature under which the experiment is being conducted is directly responsible for the sliding and wear properties of the brass specimen. The current studies and observations involved the use of a pin on disc apparatus, where the test specimen as the pin and slid against the steel plate (EN-31) at various speeds, loads, levels of lubrication and temperatures. The depth of wear under the different loading and sliding speeds are determined individually by means of an LVDT measurement.

Abstract: In recent years, both industrial and academic world are focussing their attention towards the development of sustainable composites, reinforced with fibres. In particular, among the fibres that can be used as reinforcement, the uniaxial glass fiber ones represent the most interesting for their properties. The aim of this work is to illustrate the results of friction and wear behaviour of uniaxial glass fibers with silicon carbide, aluminium oxide and graphite as the fillers. Moreover, its main manufacturing technologies have been described. The major component of these hybrid composite is uniaxial glass fibre with Epoxy LY556 (Resin). Hardener HY951 is used for hardening and support. Resin + Hardener are mixed in the ratio 10:1 and the mixture made up is called Matrix. Test materials of glass Fibre with varying compositions of 15% Al₂O₃ + SiC and glass fibre with varying compositions of 15% Graphite + SiC have been prepared by applying the matrix on glass cloth which is wrapped around the mandrel. The samples were tested in a pin-on-disc machine to determine the friction and wear losses. Further, the samples were tested on a pin-on-disc machine and frictional characteristics were monitored by varying speed and loads. Thus, the friction and wear characteristics have also been found out for the two specimens. From the experimental test results, it is observed that Al₂O₃ +Sic exihibits lower wear loss than SiC + Graphite under dry sliding conditions. Based on the observations, this hybrid composite are recommended to the manufacturing of the aircraft structures.

Abstract: Chrome nitride (CrN) and CrN/Cr thin films were grown on EN ISO HS6-5-2 tool steel, which has been used as a substrate material. It is a high-speed Mo-W steel with high toughness. Chrome nitride thin films were deposited using a RF PA CVD/Magnetron Sputtering (MS) system at a gas flow ratio of 15/13 sccm of Ar/N₂. During the deposition process the pressure in the vacuum chamber was 0.9 Pa, the deposition Ubias and deposition time were different. The parameters of the process influence properties of the thin films were microstructure, hardness and adhesion to the substrate, etc. Optimal selection of process parameters is needed to achieve particular property combinations. The basis of the tribological measurements was the “ball-on-disc” testing method. Tribological testing (EN1071-13:2010) was conducted using a ball made from Si₃N₄ with a diameter of 6.350 mm, with a constant load of 3N at room temperature and humidity of 40±2 %. A Zeiss AXIO Imager M2 light optical microscope and a Dektak XT TM mechanical profilometer were used to evaluate the wear of the friction pairs at a load of 6mg and the size of the measured area of 200x1000 μm. The basis of the tribological measurements is the “ball-on-disc” testing method. Tribological testing (EN1071-13:2010) was conducted using a ball made from Si₃N₄ with a diameter of 6.350 mm, with a constant load of 3N at room temperature and humidity of 40±2 %. A Zeiss AXIO Imager M2 light optical microscope and a Dektak XT TM mechanical profilometer were used to evaluate the wear of the friction pairs at a load of 6mg and the size of the measured area of 200x1000 μm.