Carlos A. Anjinho

Characterisation of solar-synthesised TiCx (x=0.50, 0.625, 0.75, 0.85, 0.90 and 1.0) by X-ray diffraction, density and Vickers microhardness

Abstract Homogeneous single-phase hypo-stoichiometric carbide TiC x of titanium with known stoichiometric ratio x (0.50, 0.625, 0.75, 0.85, 0.90 and 1.0) was prepared from mixed powders of Ti metal and graphite through 30xa0min solar heating in inert Ar atmosphere and characterised by X-ray diffraction (XRD), density ρ and Vickers microhardness Hv. In spite of short radiation period at relatively low temperature (no higher than 1600xa0°C), formed TiC x specimens were all with relatively high degree of crystallinity judging from good separation between Kα1 and Kα2 peaks of XRD patterns at high ( hxa0kxa0l ) index. Measured density of prepared TiC x powders was practically identical to the calculated value from the measured lattice parameter for respective x implying that f.c.c. (face centred cubic) Ti lattice was with no defect and 100 x % of the O-sites (octahedral interstitial sites) were filled with C atoms leaving the rest 100(1− x )% of O-sites vacant. Reflecting polycrystalline nature of the prepared TiC x compact, measured Hv scattered over range of ±400 around 1100. Application of 50xa0h heat treatment at 600xa0°C appeared to realise C atoms ordering re-configuration over O-sites leading to slight extent of tetragonal distortion for TiC x specimens with x =0.50 and 0.625.

Fracture toughness of solar-sintered WC with Co additive

A tungsten carbide (WC) cylinder specimen containing 10 mass% Co sintering aid was prepared under concentrated solar radiation (measured maximum temperature no higher than 1500 °C) in dynamic primary vacuum and its fracture toughness was evaluated by Vickers indentation method. In spite of very fast rates of heating and cooling applied in the solar-sintering process, fracture toughness of the prepared WC cylinder specimen was comparable to that of WC sintered piece prepared through a conventional industrial process in electric furnace under a slow heating and cooling condition. Present results together with the previously reported results for solar-sintered alumina ceramic disk appear to suggest the promising possibility of using solar radiation heating for manufacturing sintered ceramic components.

Effect of Paraffin Oil Used as a Lubricant in Tensile Tests of Carbon Fibre Bundles

The failure of carbon fibre bundles of Tenax 5131 HTA with 6000 filaments is characterised using the European Standard EN 1007-5. It is shown that the addition of liquid paraffin to the bundle causes a global change of the load-displacement curve and the effects of the presence of a liquid lubricant are discussed.

Evaluation of the Relationship between Diamond Tool Wear Performance and the Mechanical Properties of the Individual Metallic Binders

A test methodology is employed to investigate the cutting behaviour of five different diamond impregnated tools for cutting hard materials, such as rocks. A set of parameters, which characterise the tool wear (specific wear loss in the tool), and its relationship with the cutting force of the examined tools, are established to evaluate the tool wear performance. The procedure established in this work describes the specifications of the equipment used to carry out the tests, the different cutting conditions, the format of the output parameters and the characterisation of the different materials used (binders and rocks), hence allowing to discuss the overall cutting wear behaviour of the tools. The methodology presented indicates a universally applicable procedure for measuring the wear performance of the diamond tools as, at the same time, it establishes a relationship between wear and the mechanical parameters of the different metallic binder materials used to manufacture the correspondent tools. The procedure is proven to be an indispensable instrument for correctly carrying out wear performance tests and for reliably interpreting the wear mechanisms of the tool.

A New Laboratory Methodology for Assessing the Cutting Behaviour of Gangsawing Blades

The objective of this work is to present a new laboratory testing methodology suitable for estimate the forces generated during multiple blade gangsawing employed on marble and limestone. This methodology allows analysing the tool behaviour aiming to contribute for developing new products and/or optimize the working conditions for processing different classes of stones. In the present research, 3 different diamond linear blades were tested against 2 types of stones (limestone and marble), studying the effect of two working parameters. The linear blades differ in the characteristics of the segments: size of diamond grit and type of metallic binders used to embed the diamond. The classification equipment used in this work consists in a special bridge cutting machine incorporating a tailored instrumentation / sensing system to control the working conditions while all the necessary cutting outputs are monitored and stored by special software. Taking into account the output parameters measured to evaluate the tool behaviour (vertical and horizontal forces, electric energy consumption, vibrations measured by accelerometers and tool wear); it is possible to classify and select tools with relation to the efficacy of the cut.

Finite Element Analysis of the Thermal Residual Stresses of Diamond Cutting Tools in the Sintering Process

The main objective of the present work is to present and discuss the effects of the residual stresses generated in the matrix. Both, elastic and elastic-plastic models using explicit finite element code Abaqus were developed to investigate the thermal residual stresses generated around a diamond particle embedded in a metal matrix (a binder) during the sintering process for obtaining a diamond tool. The first part of the work consists in examining the thermal residual stress field generated by using three sintering temperatures from which the bodies are cooled from (T1=800°C, T2=700°C and T3=600°C) and two diamond shapes modelled with 2D axisymmetric elements, one from a circle the other from an octagon, respectively. In this case only one type of binder showing typical elastic behaviour is considered. The second part of this work consists in comparing the finite element solutions using binders with different tensile behaviour (elastic vs. elastic-plastic behaviour). This last study has used a particle shape generated from the octagon, since this shape allows, in a great number of real situations, the simulation of a particle with a larger number of facets, in line with what it is observed when looking at a conventional diamond tool.

Statistical Evaluation of the Adequacy of a Mixture of Two Weibull Distributions to Model Strength and Fracture-Strain of Carbon Fibres

Based on data generated by the European Standard EN 1007-5 used for the characterization of the tensile behaviour at room temperature of multifilament tows made of continuous ceramic filaments this paper describes an adjustment of mixture of two Weibull distributions to the fibresx92 fracture data. The statistical modelling is illustrated with data on a large range of stress and strain values. Parameter estimates are obtained using maximum likelihood method implemented at R software (version 1.6.2, 2003-01-10) from Free Software Foundationx92s GNU General Public License.

3D-FEM Simulation and Design Optimization of the Diamond Cutting Tools under Various Loading Conditions

The objective of this work is to develop analysis methods based on 3D-FEM simulations for optimum design of the diamond cutting tools under various loading conditions, considering the sintering process of diamond–metal matrix to originate residual stresses. The work concerns the use of finite element simulation for modelling of thermal residual stresses generated during the sintering process of metal matrix diamond tools normally employed by the industry. Stress distribution fields were determined for the diamond shape using a 4-node, reduced integration ABAQUS solid element type C3D4. The residual stress fields in the nearby region of a diamond particle are examined to study the effects of the sintering temperatures, the stress–strain behaviour of the metal matrix and the compression pressure on the upper surface of the metal matrix. Through the simulations of the cutting forces on the diamond, it is demonstrated that the diamond retention capacity induced by the metal matrix (important for extending the life of a diamond tool) is principally dependent on the sintering process. Optimum design of the diamond cutting tools can be achieved by selecting the appropriate sintering temperatures, the stress–strain behaviour of the metal matrix and the compression pressure on the upper surface of the metal matrix during the sintering process.