Micro-Indentation of Metal Matrix Composites: A 3D Finite Element Analysis

This paper investigates the inhomogeneous behavior of MMCs subjected to microindentation by a spherical indenter using 3D finite element analysis. This includes the effects on hardness of volume percentage of reinforced particles and indenter-to-particle diameter-ratio. It was found that the increase of volume percentage of reinforced particles and indenter-to-particle diameterratio increases the resistance to deformation of an MMC. The hardness varies in a complex way with the changes of load, volume percentage of particles and indenter-to-particle diameter-ratio

Comparative study between wear of uncoated and TiAlN-coated carbide tools in milling of Ti6Al4V

As is recognized widely, tool wear is a major problem in the machining of difficult-to-cut titanium alloys. Therefore, it is of significant interest and importance to understand and determine quantitatively and qualitatively tool wear evolution and the underlying wear mechanisms. The main aim of this paper is to investigate and analyse wear, wear mechanisms and surface and chip generation of uncoated and TiAlN-coated carbide tools in a dry milling of Ti6Al4V alloys. The quantitative flank wear and roughness were measured and recorded. Optical and scanning electron microscopy (SEM) observations of the tool cutting edge, machined surface and chips were conducted. The results show that the TiAlN-coated tool exhibits an approximately 44% longer tool life than the uncoated tool at a cutting distance of 16 m. A more regular progressive abrasion between the flank face of the tool and the workpiece is found to be the underlying wear mechanism. The TiAlN-coated tool generates a smooth machined surface with 31% lower roughness than the uncoated tool. As is expected, both tools generate serrated chips. However, the burnt chips with blue color are noticed for the uncoated tool as the cutting continues further. The results are shown to be consistent with observation of other researchers, and further imply that coated tools with appropriate combinations of cutting parameters would be able to increase the tool life in cutting of titanium alloys

Mechanism of Force Generation in Cutting Metal Matrix Composites

This paper presents a mechanics model for predicting the forces of cutting aluminum-based SiC/Al2O3 particle reinforced MMCs. The force generation mechanism was considered to be due to three factors: (a) the chip formation force, (b) the ploughing force, and (c) the particle fracture force. The chip formation force was obtained by using the Merchant’s analysis but those due to matrix ploughing deformation and particle fracture were formulated, respectively, with the aid of the slip line field theory of plasticity and the Griffith theory of fracture. A comparison of the model predictions with the experimental results published in the literature showed that the theoretical model developed has captured the major material removal/deformation mechanisms in MMCs and describes very well the experimental measurements

Micro-indentation of metal matrix composites: a 3D finite element analysis

This paper investigates the inhomogeneous behaviour of metal matrix composites subjected to micro-indentation by a spherical indenter, using 3D finite element analysis. This includes the effects on hardness of volume fraction of reinforced particles and (indenter):(particle diameter) ratio. It was found that increasing the volume fraction of reinforced particles and the (indenter):(particle diameter) ratio increases the resistance to deformation of the composite. The hardness varies in a complex way with the changes of load, volume percentage of particles and (indenter):(particle diameter) ratio

Machining of particulate-reinforced metal matrix composites

The presence of hard reinforce particles in two phases materials, such as metal matrix composites (MMCs), introduces additional effects, such as tool–particle interactions, localised plastic deformation of matrix material, possible crack generation in the shear plane etc., over the monolithic material during machining. These change the force, residual stress, machined surface profile generation, chip formation and tool wear mechanisms. Additional plastic deformation in the matrix material causes compressive residual stress in the machined surface, brittle chips and improved chip disposability. Possible crack formation in the shear plane is responsible for low machining force and strength and higher chip disposability. Tool–particle interactions are responsible for higher tool wear and voids/cavities in the machined surface. This chapter presents the effects of reinforcement particles on surface integrity and chip formation in MMCs. The modelling of cutting is also discussed. Finally, tool wear mechanisms are described

Micro–indentation of metal matrix composites – an FEM investigation

Micro-indentation has been widely used to evaluate the mechanical properties of materials. It has also been considered to be an important measure in the study of machinability of difficult-to-machine materials such as metal matrix composites (MMCs). Because of the complexity of deformation of an MMC and the interaction in the vicinity of contact zone between the indenter and work material, an analytical or experimental method is unable to predict the detailed deformation process. The present paper uses the finite element method to investigate the behaviour of MMCs subjected to micro-indentation by a spherical indenter including the development of stress and strain fields in the MMCs during loading/unloading. Particle fracture, debonding and displacement, and inhomogeneous deformation of matrix material were explored and compared with the experimental results reported in the literature. The analysis also provides an insight for understanding the formation of residual stresses in machined MMC components

Surface integrity characteristics of machined MMCs

Abstract not available

Nanomechanical and tribological characterization of silk and silk-titanate composite coatings

This paper investigates the tribological and mechanical properties of silk-based nanocomposite coatings which are finding applications in optics, biomedicine and dentistry, thanks to the exceptional mechanical/optical properties and associated biocompatibility of silk. Three different nanocomposite formulations were synthesized, and thin films were prepared by spin coating at different thicknesses and with different post-deposition annealing processes. Ellipsometry, FTIR spectroscopy, AFM, nanoindentation, scratch testing, continuous/reciprocating wear testing, confocal microscopy and SEM were used to characterize the coatings. The results reveal that their hardness and elastic modulus are in the range 0.56\u20131.30 GPa and 23.6\u201355.4 GPa, respectively, which are much higher than those reported for other silk films in literature. Incorporation of titanate nanosheets also improved coatings\u2019 scratch resistance

Nanomechanical and tribological characterization of silk and silk-titanate composite coatings

This paper investigates the tribological and mechanical properties of silk-based nanocomposite coatings which are finding applications in optics, biomedicine and dentistry, thanks to the exceptional mechanical/optical properties and associated biocompatibility of silk. Three different nanocomposite formulations were synthesized, and thin films were prepared by spin coating at different thicknesses and with different post-deposition annealing processes. Ellipsometry, FTIR spectroscopy, AFM, nanoindentation, scratch testing, continuous/reciprocating wear testing, confocal microscopy and SEM were used to characterize the coatings. The results reveal that their hardness and elastic modulus are in the range 0.561.30 GPa and 23.655.4 GPa, respectively, which are much higher than those reported for other silk films in literature. Incorporation of titanate nanosheets also improved coatings scratch resistance