Advanced Materials and Processes Research Institute
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Dry sliding wear behaviour of an aluminium alloy–granite particle composite
No full textIn the present study, the effect of granite reinforcement on the dry sliding wear behaviour of an aluminium–silicon alloy (BS:LM6) was investigated using a pin-on-disc machine. The composite was prepared using liquid metallurgy technique wherein 10 wt.% granite particles were incorporated in the matrix alloy. Sliding wear tests were conducted at applied loads in the range 0.2–1.6 MPa and speeds of 1.89, 3.96 and 5.55 m/s. The matrix alloy was also prepared and tested under identical conditions in order to see the influence of the dispersoid phase on wear behaviour. It was observed that the composite exhibited lower wear rate than that of the matrix alloy. Increasing applied load increased the wear rate. In the case of the composite, the wear rate decreased with speed except at higher pressures at the maximum speed; the trend reversed in the latter case. On the contrary, the matrix alloy exhibited minimum wear rate at the intermediate test speed. Seizure pressure of the composite was significantly higher than that of the matrix alloy, while temperature rise near the contacting surfaces and the coefficient of friction followed an opposite trend. SEM examination of the worn surfaces, subsurface regions and debris enabled to understand the operating wear mechanisms
Correlation of abrasive wear with microstructure and mechanical properties of pressure die-cast aluminum hard-particle composite.
No full textAluminum hard particle composites were synthesized by the solidification processing technique and the composite melt was solidified using gravity and pressure die castings. An aluminum-silicon alloy (A 332.1) has been used as the matrix and silicon carbide particles (quantity: 10 wt pct, and size: 50 to 80 µm) have been used as reinforcement for synthesis of the composite. The microstructure of the pressure die cast composite is found to be finer than those of the gravity cast ones. Additionally, the distribution of SiC particles in the Al alloy matrix is found to be more uniform in the pressure die-cast composites compared to the gravity die-cast ones. The mechanical properties such as ultimate tensile strength, hardness, and ductility are observed to be superior in the case of pressure die-cast composites compared to the gravity-cast one. The two-body abrasive wear resistance of the Al-composite is also noted to be greater in the pressure die-cast composite than in the gravity-cast one. The effects of injection pressure on the mechanical properties and wear resistance of the pressure die-cast composites are examined. It is observed that the wear resistance (inverse of wear rate), hardness, and strength of the Al-SiC composites increase with the increase in injection pressure during pressure die casting. This may be due to the finer microstructure, the absence of casting defects, and the stronger interfacial bonding between the matrix and hard dispersoid in pressure die-cast composites. The wear rate of the alloys and composites is studied as a function of their hardness, strength, and Young’s modulus. It is noted that the wear rate is primarily controlled by hardness even though other mechanical properties influence the wear behavior of the materials to some extent. An attempt is made to establish an empirical relation to correlate the wear rate of material with the mechanical properties such as hardness, ultimate tensile strength, and elongation
Dynamic mechanical behavior of LCP fiber/glass fiber-reinforced LLDPE composites.
No full textLiquid crystalline polymer (LCP) fibers and glass fibers have been used to rein force linear low density polyethylene (LLDPE) by using an elastic melt extruder and the compression molding technique. The impact behavior of hybrid composites of different composition is compared and is explained on the basis of the volume frac tion of the fibers. Addition of glass fibers decreases the Izod impact strength LLDPE. The impact strength of the composites increases when glass fibers are placed by LCP fibers. Dynamic mechanical α and β relaxations are studied and effect of variation of fiber composition on these relaxations is reported in the tem perature range from −50 to 150°C at 1 Hz frequency, a relaxation shifts toward higher temperatures with addition of fibers in LLDPE. Addition of fibers increases the storage modulus of LLDPE
Sliding wear of PP/UHMWPE blends: effect of blend composition.
No full textIn the present investigation, a wear resistant polymer, ultra high molecular weight polyethylene (UHMWPE) was melt blended with isotactic polypropylene (PP) in different proportions. Sliding wear tests were conducted by using Cameron Plint pin-on-disc apparatus. Polymer samples in the form of the pin were tested against EN-24 steel disc at different pressures and sliding speeds. The wear volume of PP reduces significantly on the addition of UHMWPE. At 0.28 m/s sliding speed, wear rate of PP was 15×10−12 m3/m which reduces to 0.28×10−12 m3/m on addition of 15 wt.% of UHMWPE. At 1.09 m/s sliding speed, PP deforms, while 15 wt.% of UHMWPE sample does not show significant deformation. Wear loss of 15 wt.% UHMWPE filled PP blend significantly low as compared to PP. Reduction in wear loss of UHMWPE filled PP blend has been attributed to the reduction in temperature of contact surface. Worn surface of the test sample showed two distinct morphological regions
Development in the understanding of South African styles SAG mills.
No full textThe South African style SAG (RoM) mills operate in a window that is almost exclusive from the operation of the Australian and North American mills that have been used for the development of SAG mill models. Combining good quality, test data from the RoM mills is extending and improving these models, and assisting in a practical manner in improving our understanding of SAG/AG milling. Data from high mill loads, both in absolute filling and ball loading, have been used to extend and improve the JK SAG mill model. This improved understanding has been successfully applied to increasing the throughput of a mill by 8%. Data is presented on relationships between power and load for high mill loading. Slurry pooling is common in closed-circuit RoM mills, and the detrimental effect of this has been dramatically demonstrated at ALCOA with a mill throughput increase of over 20%. Techniques for calculating the effects of slurry pooling have been developed and a new pulp lifter system designed to give optimal slurry discharge. The influence of mill speed in shifting the product size distribution has also been measured. (C) 2001 Elsevier Science Ltd. All rights reserved
Effects of Some Material and Experimental Variables on the Slurry Wear Characteristics of Zinc-Aluminium Alloys
No full textWear Characteristics of a Zinc-Based Alloy Compared with a Conventional Bearing Bronze under Mixed Lubrication Condition: Effects of Material and Test Parameters
No full textThis study discusses the sliding wear response of a zinc-based alloy (conforming to ZA 27) in mixed lubrication conditions at different sliding pressures and speeds. A conventional bearing bronze (conforming to SAE 660) was also tested under identical test conditions for comparison purposes. Wear rate increased with speed and pressure. Further, the zinc-based alloy attained superior wear\ud
response (less wear rate and frictional heating) than the bronze at all test speeds except prior to seizure (occurring at 7.0 MPa) at the speed of 4.60 m/s. The trend reversed in the latter case. Wear rate of the specimens also agreed with the degree of frictional heating experienced by them. A higher wear rate corresponded to larger frictional heating and vice versa. Wear behaviour of the samples improved considerably in the present study due to the presence of the oil lubricant as compared to the study in dry conditions.\ud
Wear behaviour of the samples has been discussed in terms of the nature and response of their various microconstituents and the effects produced by varying test speeds and pressures under mixed lubrication conditions. Features of wear surfaces, subsurface regions and debris particles generated during the testing of the specimens further substantiated the observed wear behaviour of the samples and were helpful in understanding the operating wear mechanisms
Adsorption of cyanide from aqueous solutions at\ud pyrophyllite surface.
No full textThe adsorption of cyanide from aqueous solutions at pyrophyllite mineral surface has been studied by investigating\ud
the effect of initial concentration of adsorbate, amount of adsorbent, pH and temperature of test solutions. The\ud
adsorption efficiency is observed to be 99% in dilute solutions but decreases down to 40% with increase in cyanide\ud
concentration to 10 ppm. The adsorption is observed to be maximum from neutral solutions and is observed to\ud
increase with increase in temperature. The adsorption data have been fitted in Langmuir and Freundlich isotherms\ud
and the adsorption has been found to be endothermic in nature in the temperature range 30–60°
Mechanisms of material removal under high stress abrasive wear conditions under varying experimental conditions.
No full textAn attempt has been made to understand the mechanism of material removal during two-body abrasive wear of Al-alloy (LM13)-SiC composite under varying experimental conditions through the wear surface and subsurface examination. It has been noted that the mechanisms of material removal during the wear process are primarily cutting and plowing, which lead to formation of continuous wear grooves. In the composite, SiC particles act as protrusions over the surface and protect the matrix from wear. But at higher applied load, coarser abrasive size, and larger sliding distances, some of the SiC particles get fractured into fine particles and scooped off from the wear surface leading to a higher wear rate. The subsurface studies show severe plastic deformation and finally formation of a mechanically mixed layer (MML) over the plastically deformed zone. The MML gets fractured during the wear process and finally removed by the formation of lateral and transverse cracking. The cracks are generally initiated at the interface of MML and the plastically deformed zone and propagate along the weaker region in MML. The material removal mechanism has been schematically presented in order to have a better understanding
Effect of interlamellar spacing on the mechanical properties of 0.65% C steel.
No full textThe mechanical properties of a steel containing a nearly fully pearlitic structure have been examined as a function of the interlamellar spacing. The steel had been heat-treated at different austenitization temperatures in order to obtain varying interlamellar spacings. It was observed that hardness and yield strength follow a Hall–Petch type of relationship with respect to the interlamellar spacing but the ultimate tensile strength (UTS), percent elongation and impact toughness did not do so. It was noted that, below a critical size of interlamellar spacing, the UTS, impact toughness and ductility remained invariant to the interlamellar spacing. The results have been explained on the basis of a microstructure–thermal residual stress relationship