Wear
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The combination of indentation, inclined-plane sliding, and wear tests provides useful and unique way to investigate ceramic wear and wear transition mechanisms. The experimental results show that wear mechanisms of ceramics are predominantly dependent on the tribological contact stresses. At low contact stress, the removal of material is controlled by plastic deformation induced microfracture on...
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Variable feed machining has recently been proposed as a significant method to improve cutting tool life particularly for hard and diffucult to machine materials. This method, which is easy to apply in industry, has been shown to improve tool life in the order of 40% in certain cases. This paper presents a reliability model for the quantitative study of the effect of feed variation on tool wear and...
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The 2024 aluminum alloy reinforced with 15 vol.% SiC whisker and 15 vol.% molybdenum powder was fabricated using the powder metallurgy method. The pure alloy and composite pins were run against a 440C disk in a Falex-6 multispecimen friction and wear test machine at a sliding speed of 0.75 m s - 1 (600 rev min - 1 ) and applied loads of 100-800 N (5.73-45.80 MPa). When lubricated...
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Since spalling in ball bearings seriously degrades operating conditions in machine systems, in-process methods for predicting spalling are needed to keep the systems running properly. In this paper, the discrete wavelet transform (DWT) is applied to vibration signals to predict the occurrence of spalling in ball bearings. The DWT yields information on both the time and frequency characteristics of...
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Dry sliding wear tests were carried out on an unreinforced Al-12%Si alloy and on composites of the same alloy reinforced with 5, 8, or 12 vol.% short alumina fibres by means of a block-on-ring (bearing steel) wear test machine. The worn surfaces and cross-sections through the surfaces were examined by optical microscopy and by scanning electron microscopy. It was found that above a critical applied...
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The contact problem between two solid bodies has been studied, considering the existence of a third thin body separating the two bodies, with a viscoplastic behaviour law of Norton-Hoff type. The limit problem corresponding to the first order solution of the asymptotic problem is investigated, from the mathematical point of view. Several equivalent variational formulations of the model are derived...
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The effect of varying the workpiece diameter on the cutting tool effective clearance angle has been investigated. Theoretical analysis of the relationship between the workpiece diameter and the cutting tool clearance angle is presented. To simulate this relationship experimentally, the cutting tool working normal clearance angle was kept constant, while varying the workpiece diameter, cutting speed...
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The friction and wear behavior of Al 2 O 3 /TiB 2 composite sliding against cemented carbide both in air and nitrogen atmospheres at temperatures ranging from 25°C to 800°C was studied. The friction coefficient and wear rate were examined in relation to the TiB 2 content. Results showed that the friction coefficient decreased with increasing TiB 2 content. The...
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The purpose of this report is to develop the new bonding resin for fixing 3-41 μm SiC abrasives in grinding stone that generates the ultra precision surface on high-purity aluminium alloy. An aluminium disk substrate is processed by a double-sided lapping machine on which the grinding stone is mounted. The developed grinding stone is a resin bond type, composed of a mixture of PVA resin, melamine...
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In recent years there has been considerable growth in the use of optical methods for evaluating surfaces. Conventional stylus techniques, though powerful, have their own limitations. These include the resolution of the stylus, and the damage caused by the moving diamond stylus when tracing profiles on soft materials. Hence non-contact methods of measuring surface finish of often required. One approach...
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Composite specimens of 2024 aluminum alloy reinforced with 15 vol.% SiC whiskers and 15 vol.% molybdenum powder were fabricated using powder metallurgy (PM). The composite pins were run against a 440C disk in a Falex-6 multi specimen friction and wear testing machine. Paraffin oil containing 3 wt.% tricresyl phosphate (TCP), chlorinated paraffin (CP) or zinc dialkyldithiophosphate (ZDDP) additives...
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The SiC particle reinforced Al-Cu aluminum matrix composites were dry sliding against 4Cr13, W 1 8 Cr 4 V Steel and Si 3 N 4 ceramics on a reciprocal sliding wear testing machine at ambient conditions. Experiments were performed within a normal load range of 20 to 175 N and a sliding velocity of 0.075 to 1.2 m s - 1 . It was found that there was a big...
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The endurance of MoS 2 sputter-coated steel balls was measured in continuous and stop-start sliding tests in a four-ball wear tester. Test variables were counterface materials, uncoated steel and two ceramics (Co-bonded tungsten carbide and sapphire), and gaseous atmospheres, dry Ar and dry air. In continuous tests, coating endurance increased from 14 to 80 min; combinations were ranked as...
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Wear and wear transitions are the major concerns regarding the tribological application of ceramic materials. The objective of this study is to understand wear and wear transition mechanisms of ceramics with emphasis on wear and wear transition prediction. There are four new findings from this research. First, the critical external damage stress (σ D ) from a fracture mechanics model was modified...
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This work is concerned with the evaluation of the friction coefficient in an EHD roller-inner ring contact, in a roller bearing for a jet engine application, considering a non-Newtonian behaviour of the lubricant.In order to simplify the analysis, of this complex problem, the elastohydrodynamic contact is simulated by a dry Hertzian contact, whose surfaces are separated by a thin lubricant film. The...
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There are several processes in textile finishing to improve fabric touch: one of them is sanding (emerizing). There is no current control system for this process. This study describes a tribological method for the quantization of sanding. Textile fabric is rubbed with a probe; the signal obtained is studied in the frequency domain. The calculated autospectrum shows a peak (or several peaks with the...
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An equation has been proposed to describe sliding wear caused by microfracture in polycrystalline alumina ceramics. The wear equation has been simplified, and grain size dependence for dry sliding wear data by Wu et al. has been shown to agree with this equation. For lubricated sliding in a ball-on-flat configuration, modification of the equation is necessary. A concept of equivalent 'real' contact...
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The development of wear maps has enhanced a new approach to the wear behaviour of materials as it is a precise description of the mechanical loading (local stress and strain fields).This paper studies crack nucleation using fatigue criteria in the case of an elastically loaded dry contact. Fretting behaviour is analysed for partial slip conditions which have been identified experimentally and theoretically...
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A deformation-processed Cu 15vol.%Cr in situ composite was made by consumable are melting and casting followed by extensive deformation. A superior combination of mechanical strength and electrical/thermal conductivity was achieved with the composite since Cr filaments existed in the nearly pure copper matrix. The effects of sliding speed and normal pressure on sliding wear behavior and microstructure...
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To improve the wear resistance of the piston ring and cylinder liner for the automobiles in desert area applications, an experimental study has been made for Ni-based composite coatings deposited on traditional cast substrates by plasma spraying with laser post-treatment. Three Ni-WC composite coatings with varied contents of WC particles were tested. Tribological experiments were carried out under...
