Atul Gaur | Rajasthan Technical University (original) (raw)
Papers by Atul Gaur
Wear, Jan 1, 1995
The machinability of a DURALCAN® aluminium metal matrix composite (A359/SiC/20p) has been studied... more The machinability of a DURALCAN® aluminium metal matrix composite (A359/SiC/20p) has been studied in this paper. Continuous turning of round composite bars using tools with 25 mm polycrystalline diamond (PCD) inserts has been selected as the test method. The matrix of test conditions included cutting speeds of 300, 500 and 700 m min−1 and feed rates of 0.1, 0.2 and 0.4 mm rev−1 while the depth of cut has been kept constant at 0.5 mm.The performance of the tools is based on development of 0.25 mm maximum flank wear, which has been monitored by optical and scanning electron microscopy. The tool life data have been analyzed using regression techniques and a general form of the Taylor equation has been developed to describe the tool performance on this composite. The time required to reach the tool wear limit decreased with increases of speed and feed. However, the volume of material removed before reaching the wear limit actually increases with the higher feed rate. These phenomena have been reconciled by rewriting the Taylor equation in a modified form. Practical implications of this deviation are discussed and comments are made on the effects of cutting parameters on surface finish and chip formation.
Journal of Materials Processing Technology, Jan 1, 2003
This paper presents a study of the influence of cutting conditions (cutting velocity and feed) an... more This paper presents a study of the influence of cutting conditions (cutting velocity and feed) and cutting time on turning metal matrix composites (MMCs). A plan of experiments, based on the techniques of Taguchi, was performed machining with cutting conditions prefixed in workpieces. An orthogonal array and the analysis of variance (ANOVA) are employed to investigate the cutting characteristics of MMC (A356/20/SiCp-T6) using PCD cutting tools. The objective was to establish a correlation between cutting velocity, feed and the cutting time with the tool wear, the power required to perform the machining operation and the surface roughness in workpiece. These correlations were obtained by multiple linear regression. Finally, confirmation tests were performed to make a comparison between the experimental results foreseen from the mentioned correlations.
A theory describing the strain, ultimate strength, and work during uniform strain to ultimate loa... more A theory describing the strain, ultimate strength, and work during uniform strain to ultimate loading of metal-matrix composites deformed in tension parallel to the reinforcement is presented. These quantities may be calculated for composites of arbitrary volume fraction using only the component stress-strain curves. The theory is based on the systematic application of a macroscopic principle commonly used to predict the ultimate strength of ductile monolithic materials—namely, that necking occurs when the load borne by the material is maximized. For brittle reinforcing elements, the results are identical to those of previous workers. For ductile reinforcing elements, necking strains intermediate between those of the components and ultimate strengths increasing smoothly with volume fraction from that of the matrix to that of the reinforcement are predicted. The theory can be used to predict the variation of composite ultimate properties with any parameter of interest. In this paper the variation with volume fraction and yield strength of the matrix are studied, with both exact solutions and useful approximations being derived.
Journal of The Mechanics and Physics of Solids, Jan 1, 1998
A micromechanical model is developed to simulate the mechanical response in tension of particle-r... more A micromechanical model is developed to simulate the mechanical response in tension of particle-reinforced metal-matrix composites. The microstructure of the composite is represented as a three-dimensional array of hexagonal prisms with one reinforcement at the centre of each prism. The shape, volume fraction and state (either intact or broken) of the reinforcement is independent for each cell, so the interaction among all these factors could be studied. The tensile response of the composite is determined from the behaviour of the intact and damaged cells, the fraction of damaged cells being calculated on the assumption that the reinforcement strength follows the Weibull statistics. The model is used to determine the microstructural factors which provide optimum behaviour from the point of view of the tensile strength and ductility. The analyses included the effect of the matrix and reinforcement properties, the reinforcement volume fraction, the interaction between reinforcements of different shape and the heterogeneous distribution of the reinforcements within the composite.
Composites Science and Technology, Jan 1, 2005
Over the past two decades – a period coinciding with publication of Composites Science and Techno... more Over the past two decades – a period coinciding with publication of Composites Science and Technology – metal matrix composites (MMCs) have been transformed from a topic of scientific and intellectual interest to a material of broad technological and commercial significance. The worldwide MMC markets in 1999 accounted for 2500 metric tons valued at over $100M. Important MMC applications in the ground transportation (auto and rail), thermal management, aerospace, industrial, recreational and infrastructure industries have been enabled by functional properties that include high structural efficiency, excellent wear resistance, and attractive thermal and electrical characteristics. A suite of challenging technical issues has been overcome, including affordable primary and secondary processing, material design and development methodologies, and characterization and control of interfacial properties. This article describes the technological features that characterize the MMC industry. Matrix/reinforcement systems and primary and secondary processes of commercial significance will be broadly described. Several metrics that underscore the growing maturity of the MMC industry will be discussed, including the emergence of a second tier support industry and the growth of standardized materials and methods. MMC applications in the major markets of ground transportation, thermal management, aerospace, industrial, recreational and infrastructure will be described. Successful commercialization strategies will be discussed and insights for achieving expanded MMC applications will be given. A forward look at candidate approaches for the next generation of MMCs will be provided, including projections of new MMC paradigms.
Journal of Materials Processing Technology, Jan 1, 2000
The production methods and properties of metal matrix composite materials reinforced with dispers... more The production methods and properties of metal matrix composite materials reinforced with dispersion particles, platelets, non-continuous (short) and continuous (long) fibres are discussed in this paper. The most widely applied methods for the production of composite materials and composite parts are based on casting techniques such as the squeeze casting of porous ceramic preforms with liquid metal alloys and powder metallurgy methods. On account of the excellent physical, mechanical and development properties of composite materials, they are applied widely in aircraft technology and electronic engineering, and recently in passenger-car technology also.
Journal of Materials Processing Technology, Jan 1, 1999
Combining high specific strength with good corrosion resistance, metal matrix composites (MMCs) a... more Combining high specific strength with good corrosion resistance, metal matrix composites (MMCs) are materials that are attractive for a large range of engineering applications. Given the factors of reinforcement type, form, and quantity, which can be varied, in addition to matrix characteristics, the composites have a huge potential for being tailored for particular applications. One factor that, to date, has restricted the widespread use of MMCs has been their relatively high cost. This is mostly related to the expensive processing techniques used currently to produce high quality composites. In this paper, the relatively low cost stir casting technique is evaluated for use in the production of silicon carbide/aluminium alloy MMCs. The technical difficulties associated with attaining a uniform distribution of reinforcement, good wettability between substances, and a low porosity material are presented and discussed.
Materials Science & Engineering R-reports, Jan 1, 2000
During the past decade, considerable research effort has been directed towards the development of... more During the past decade, considerable research effort has been directed towards the development of in situ metal matrix composites (MMCs), in which the reinforcements are formed in situ by exothermal reactions between elements or between elements and compounds. Using this approach, MMCs with a wide range of matrix materials (including aluminum, titanium, copper, nickel and iron), and second-phase particles (including borides, carbides, nitrides, oxides and their mixtures) have been produced. Because of the formation of ultrafine and stable ceramic reinforcements, the in situ MMCs are found to exhibit excellent mechanical properties. In this review article, current development on the fabrication, microstructure and mechanical properties of the composites reinforced with in situ ceramic phases will be addressed. Particular attention is paid to the mechanisms responsible for the formation of in situ reinforcements, and for creep failure of the aluminum-based matrix composites.
Journal of Materials Science, Jan 1, 1991
The physical and mechanical properties that can be obtained with metal matrix composites (MMCs) h... more The physical and mechanical properties that can be obtained with metal matrix composites (MMCs) have made them attractive candidate materials for aerospace, automotive and numerous other applications. More recently, particulate reinforced MMCs have attracted considerable attention as a result of their relatively low costs and characteristic isotropic properties. Reinforcement materials include carbides, nitrides and oxides. In an effort to optimize the structure and properties of particulate reinforced MMCs various processing techniques have evolved over the last 20 years. The processing methods utilized to manufacture particulate reinforced MMCs can be grouped depending on the temperature of the metallic matrix during processing. Accordingly, the processes can be classified into three categories: (a) liquid phase processes, (b) solid state processes, and (c) two phase (solid-liquid) processes. Regarding physical properties, strengthening in metal matrix composites has been related to dislocations of a very high density in the matrix originating from differential thermal contraction, geometrical constraints and plastic deformation during processing.
Wear, Jan 1, 1995
The machinability of a DURALCAN® aluminium metal matrix composite (A359/SiC/20p) has been studied... more The machinability of a DURALCAN® aluminium metal matrix composite (A359/SiC/20p) has been studied in this paper. Continuous turning of round composite bars using tools with 25 mm polycrystalline diamond (PCD) inserts has been selected as the test method. The matrix of test conditions included cutting speeds of 300, 500 and 700 m min−1 and feed rates of 0.1, 0.2 and 0.4 mm rev−1 while the depth of cut has been kept constant at 0.5 mm.The performance of the tools is based on development of 0.25 mm maximum flank wear, which has been monitored by optical and scanning electron microscopy. The tool life data have been analyzed using regression techniques and a general form of the Taylor equation has been developed to describe the tool performance on this composite. The time required to reach the tool wear limit decreased with increases of speed and feed. However, the volume of material removed before reaching the wear limit actually increases with the higher feed rate. These phenomena have been reconciled by rewriting the Taylor equation in a modified form. Practical implications of this deviation are discussed and comments are made on the effects of cutting parameters on surface finish and chip formation.
Journal of Materials Processing Technology, Jan 1, 2003
This paper presents a study of the influence of cutting conditions (cutting velocity and feed) an... more This paper presents a study of the influence of cutting conditions (cutting velocity and feed) and cutting time on turning metal matrix composites (MMCs). A plan of experiments, based on the techniques of Taguchi, was performed machining with cutting conditions prefixed in workpieces. An orthogonal array and the analysis of variance (ANOVA) are employed to investigate the cutting characteristics of MMC (A356/20/SiCp-T6) using PCD cutting tools. The objective was to establish a correlation between cutting velocity, feed and the cutting time with the tool wear, the power required to perform the machining operation and the surface roughness in workpiece. These correlations were obtained by multiple linear regression. Finally, confirmation tests were performed to make a comparison between the experimental results foreseen from the mentioned correlations.
A theory describing the strain, ultimate strength, and work during uniform strain to ultimate loa... more A theory describing the strain, ultimate strength, and work during uniform strain to ultimate loading of metal-matrix composites deformed in tension parallel to the reinforcement is presented. These quantities may be calculated for composites of arbitrary volume fraction using only the component stress-strain curves. The theory is based on the systematic application of a macroscopic principle commonly used to predict the ultimate strength of ductile monolithic materials—namely, that necking occurs when the load borne by the material is maximized. For brittle reinforcing elements, the results are identical to those of previous workers. For ductile reinforcing elements, necking strains intermediate between those of the components and ultimate strengths increasing smoothly with volume fraction from that of the matrix to that of the reinforcement are predicted. The theory can be used to predict the variation of composite ultimate properties with any parameter of interest. In this paper the variation with volume fraction and yield strength of the matrix are studied, with both exact solutions and useful approximations being derived.
Journal of The Mechanics and Physics of Solids, Jan 1, 1998
A micromechanical model is developed to simulate the mechanical response in tension of particle-r... more A micromechanical model is developed to simulate the mechanical response in tension of particle-reinforced metal-matrix composites. The microstructure of the composite is represented as a three-dimensional array of hexagonal prisms with one reinforcement at the centre of each prism. The shape, volume fraction and state (either intact or broken) of the reinforcement is independent for each cell, so the interaction among all these factors could be studied. The tensile response of the composite is determined from the behaviour of the intact and damaged cells, the fraction of damaged cells being calculated on the assumption that the reinforcement strength follows the Weibull statistics. The model is used to determine the microstructural factors which provide optimum behaviour from the point of view of the tensile strength and ductility. The analyses included the effect of the matrix and reinforcement properties, the reinforcement volume fraction, the interaction between reinforcements of different shape and the heterogeneous distribution of the reinforcements within the composite.
Composites Science and Technology, Jan 1, 2005
Over the past two decades – a period coinciding with publication of Composites Science and Techno... more Over the past two decades – a period coinciding with publication of Composites Science and Technology – metal matrix composites (MMCs) have been transformed from a topic of scientific and intellectual interest to a material of broad technological and commercial significance. The worldwide MMC markets in 1999 accounted for 2500 metric tons valued at over $100M. Important MMC applications in the ground transportation (auto and rail), thermal management, aerospace, industrial, recreational and infrastructure industries have been enabled by functional properties that include high structural efficiency, excellent wear resistance, and attractive thermal and electrical characteristics. A suite of challenging technical issues has been overcome, including affordable primary and secondary processing, material design and development methodologies, and characterization and control of interfacial properties. This article describes the technological features that characterize the MMC industry. Matrix/reinforcement systems and primary and secondary processes of commercial significance will be broadly described. Several metrics that underscore the growing maturity of the MMC industry will be discussed, including the emergence of a second tier support industry and the growth of standardized materials and methods. MMC applications in the major markets of ground transportation, thermal management, aerospace, industrial, recreational and infrastructure will be described. Successful commercialization strategies will be discussed and insights for achieving expanded MMC applications will be given. A forward look at candidate approaches for the next generation of MMCs will be provided, including projections of new MMC paradigms.
Journal of Materials Processing Technology, Jan 1, 2000
The production methods and properties of metal matrix composite materials reinforced with dispers... more The production methods and properties of metal matrix composite materials reinforced with dispersion particles, platelets, non-continuous (short) and continuous (long) fibres are discussed in this paper. The most widely applied methods for the production of composite materials and composite parts are based on casting techniques such as the squeeze casting of porous ceramic preforms with liquid metal alloys and powder metallurgy methods. On account of the excellent physical, mechanical and development properties of composite materials, they are applied widely in aircraft technology and electronic engineering, and recently in passenger-car technology also.
Journal of Materials Processing Technology, Jan 1, 1999
Combining high specific strength with good corrosion resistance, metal matrix composites (MMCs) a... more Combining high specific strength with good corrosion resistance, metal matrix composites (MMCs) are materials that are attractive for a large range of engineering applications. Given the factors of reinforcement type, form, and quantity, which can be varied, in addition to matrix characteristics, the composites have a huge potential for being tailored for particular applications. One factor that, to date, has restricted the widespread use of MMCs has been their relatively high cost. This is mostly related to the expensive processing techniques used currently to produce high quality composites. In this paper, the relatively low cost stir casting technique is evaluated for use in the production of silicon carbide/aluminium alloy MMCs. The technical difficulties associated with attaining a uniform distribution of reinforcement, good wettability between substances, and a low porosity material are presented and discussed.
Materials Science & Engineering R-reports, Jan 1, 2000
During the past decade, considerable research effort has been directed towards the development of... more During the past decade, considerable research effort has been directed towards the development of in situ metal matrix composites (MMCs), in which the reinforcements are formed in situ by exothermal reactions between elements or between elements and compounds. Using this approach, MMCs with a wide range of matrix materials (including aluminum, titanium, copper, nickel and iron), and second-phase particles (including borides, carbides, nitrides, oxides and their mixtures) have been produced. Because of the formation of ultrafine and stable ceramic reinforcements, the in situ MMCs are found to exhibit excellent mechanical properties. In this review article, current development on the fabrication, microstructure and mechanical properties of the composites reinforced with in situ ceramic phases will be addressed. Particular attention is paid to the mechanisms responsible for the formation of in situ reinforcements, and for creep failure of the aluminum-based matrix composites.
Journal of Materials Science, Jan 1, 1991
The physical and mechanical properties that can be obtained with metal matrix composites (MMCs) h... more The physical and mechanical properties that can be obtained with metal matrix composites (MMCs) have made them attractive candidate materials for aerospace, automotive and numerous other applications. More recently, particulate reinforced MMCs have attracted considerable attention as a result of their relatively low costs and characteristic isotropic properties. Reinforcement materials include carbides, nitrides and oxides. In an effort to optimize the structure and properties of particulate reinforced MMCs various processing techniques have evolved over the last 20 years. The processing methods utilized to manufacture particulate reinforced MMCs can be grouped depending on the temperature of the metallic matrix during processing. Accordingly, the processes can be classified into three categories: (a) liquid phase processes, (b) solid state processes, and (c) two phase (solid-liquid) processes. Regarding physical properties, strengthening in metal matrix composites has been related to dislocations of a very high density in the matrix originating from differential thermal contraction, geometrical constraints and plastic deformation during processing.