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Natural stone production in open mining is carried out in the form of cutting the natural stone from the bedrock with different methods and reducing it to the desired dimensions. Owing to its high hardness, high sharpness, good wear resistance, good high-temperature resistance and good chemical inertness, synthetic diamond has been commonly used as abrasives of grinding or cutting tools. The segments of diamond cutting tools are composed of diamond grain and different metal powders, and the segments are usually produced via powder metallurgy process. The aim of the study is to improve the mechanical properties of the metal matrix with the addition of aluminum 7075 alloy and to improve the performance of diamond cutting tools by reducing the wear rates of the segments with increasing diamond concentration. While characterization studies were carried out with SEM and XRD for microstructure analysis, density measurement, hardness measurement, compression test and abrasion test were performed to determine the mechanical properties. The cutting performance of the samples was also evaluated by on-site field tests on an industrial scale. After the field tests, the diamonds were investigated by SEM. According to the results, the precipitation hardening occurred with the addition of Al7075 alloy. There were coaxial grains with different grain sizes on the surface of the samples. An increase in the mechanical properties of the samples was observed with precipitation hardening. In addition, the cutting performance and service life of diamond tools increased thanks to the increased diamond concentration. [ABSTRACT FROM AUTHOR]

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The cutting efficiency in underground excavations relies on the optimum parameters of the cutting tool and the cutting process. However, the optimization of the cutting tool design and the cutting process is a challenge and requires knowledge about the tool-rock interaction. This paper aims to investigate the tool-rock interaction using a rock cutting mathematical model. The confining pressure was considered in the rock cutting model with conical cutters and the discrete element method was adopted to calculate the dynamics of the rock breakage of this model. Graded particle assemblies were created, calibrated, and compressed in the horizontal direction with a certain confining pressure. Afterwards, the initiation and propagation of cracks during the rock cutting processes were recorded. A series of small-scale rock cutting tests were also carried out to verify the numerical model. The analysis results demonstrate that: 1) the confining pressure induced larger cutting force than that in the unconfined condition; 2) with increase of the confining pressure, the rock failure mode experienced predominantly brittle to predominantly ductile failure; and 3) there was a critical confining pressure/compressive strength ratio of 0.53 when the transition of failure mode occurred.

A noise effect arising in the rock cutting process is gaining a large attention as to the identification and optimization of the cuttingprocess. The sense experience acquired during the experiments in the process of rotary rock drilling related to the determination of rock typeor to the optimal drilling regime determination is formed due to sense perception, mainly hearing, and its further evaluation by the humanbrain from the information exempted from the environment.

This paper reports the results of scratch tests on three rocks (Bonne Terre Dolomite, Alabama Marble and Dunnville Sandstone) conducted at depths of cut ranging from 0.2 mm to 2.6 mm. The experiments were performed on slabs of thickness slightly smaller than the cutter width, with a camera recording the entire cutting process. The test results reveal the existence of three cutting regimes: ductile, fragmentation, and brittle with increasing depth of cut. The regimes differ by the failure mode, the dependence of the specific energy ϵ on the depth of cut d , and the fragment shapes. In the ductile regime, ϵ ∼ d 0 and the fragments are constitutive grains of the rock or powder as a result of intense shearing. In the fragmentation regime, ϵ ∼ d − 1 / 2 and the fragments is a mix of ductile-type particles and flake-like chips also the product of shear failure. Finally, the brittle regime is characterized by ϵ ∼ d − 1 and is essentially associated with chip-like fragments that come in two varieties depending on whether they are created by shear or by tension. The d − 1 -dependence of the specific energy can only be observed if the rock is sufficiently homogeneous at the scale of the experiment. The distinction between different modes of failure is based on evidence from video recording and fractography with a Scanning Electron Microscope. It is shown that the dominance of tensile over shear fracture is intimately related to the existence of a crushed zone, which acts as a wedge to initiate a tensile macrocrack in a compressive stress field. Finally, an analysis of the energy partitioning in the brittle regime indicates that the energy dissipated in creating new surfaces with a tensile crack is actually negligible compared to the energy expended in the formation of the wedge. This result indicates that the mode I toughness cannot be determined from the specific energy in the brittle regime, on the basis of a model of a crack parallel to the free surface, in contradiction with published claims to that effect. Finally, this experimental investigation clarifies some confusion in the literature, rooted on assuming the existence of only two modes of failure, ductile and brittle. • Scratch tests on rock slabs reveal ductile, fragmentation, and brittle regimes. • The scaling of the specific energy with depth of cut depends on the cutting regime. • Flake-like chips produced in the fragmentation regime are created by shear. • The crushed zone acts as a wedge to initiate tensile cracks in brittle regime. • The energy dissipated in the propagation of a tensile crack is negligible. [ABSTRACT FROM AUTHOR]

Diamond is a suitable material for cutting applications of rocks due to its outstanding properties like high hardness, great toughness, high thermal conductivity, low friction and high wear resistance. It is therefore used as the reinforcing agent in diamond cutting tools in which diamond is dispersed in a metal matrix. As rocks may exhibit different abrasiveness due to their inherent properties in the cutting operations, composition of the metal matrix should be carefully selected based on hardness and abrasivity of rocks. One of the main criteria in this selection is to ensure that diamond and metal matrix wear are as close as possible to each other, and thus to improve the service performance of the tool during cutting. The objective of this study is therefore to enhance the cutting performance of diamond tools by determining a suitable matrix composition according to hardness and abrasiveness of the rocks. For this purpose, two metal matrix compositions of Co- and Fe-based were selected and their microstructures, mechanical properties and wear properties were comparatively investigated. Micro structural, physical and mechanical characterizations were performed by SEM-EDS, XRD, density measurement, hardness measurement, compression tests and wear tests. The cutting performance of the samples was also evaluated by on-site field tests. Results showed that the mechanical properties of different matrix composition, hardness and wear resistance of Co-based matrixes are higher than those of Fe- based matrixes. On-site field tests revealed that Fe-based matrix is more suitable for cutting marble, while Co-based matrix is more suitable for cutting granite. • The objective of this study is to enhance the cutting performance of diamond tools by determining a suitable matrix composition according to hardness and abrasiveness of the rocks. • Two metal matrix compositions of Co- and Fe-based were selected and their microstructures, mechanical properties and wear properties were comparatively investigated. • The mechanical properties of different matrix composition, hardness and wear resistance of Co-based matrixes are higher than those of Fe- based matrixes. • On-site field tests revealed that Fe-based matrix is more suitable for cutting marble, while Co-based matrix is more suitable for cutting granite. [ABSTRACT FROM AUTHOR]