Prediction of cutting forces in machining of Metal Matrix Composites

This paper presents a mechanics model for predicting the forces of cutting aluminium-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 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 authors’ experimental results and those 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

An FEM investigation into the behaviour of metal matrix composites: tool–particle interaction during orthogonal cutting

An analytical or experimental method is often unable to explore the behavior of a metal matrix composite (MMC) during machining due to the complex deformation and interactions among particles, tool and matrix. This paper investigates the matrix deformation and tool–particle interactions during machining using the finite element method. Based on the geometrical orientations, the interaction between tool and particle reinforcements was categorized into three scenarios: particles along, above and below the cutting path. The development of stress and strain fields in the MMC was analyzed and physical phenomena such as tool wear, particle debonding, displacements and inhomogeneous deformation of matrix material were explored. It was found that tool–particle interaction and stress/strain distributions in the particles/matrix are responsible for particle debonding, surface damage and tool wear during machining of MMC

Deformation mechanisms of MMCs under indentation

This paper investigates the deformation mechanisms of MMCs subjected to micro-indentation by a spherical indenter using a three-dimensional finite element modeling. It was found that deformation behavior, hardness and work hardening of MMCs were highly dependant on the location of indentation relative to particles, volume percentage of the particle, and the size ratio of indenter to particle. The hardness of an MMC varied in a complex manner depending on the restriction on the matrix flow by reinforced particles and work hardening of the matrix material. Hardness increased with the increase of volume percentage of reinforced particles and decrease of the size ratio of indenter to particle. Matrix flow due to indentation was highly non-uniform which generated an inhomogeneous strain filed in an MMC. These pose a question that the conventional definition of micro-hardness is not very appropriate for characterizing MMCs

Machining of metal matrix composites: effect of ceramic particles on residual stress, surface roughness and chip formation

Machining forces, chip formation, surface integrity and shear and friction angles are important factors to understand the machinability of metal matrix composites (MMCs). However, because of the complexity of the reinforcement mechanisms of the ceramic particles, a fair assessment of the machinability of MMCs is still a difficult issue. This paper investigates experimentally the effects of reinforcement particles on the machining of MMCs. The major findings are: (1) the surface residual stresses on the machined MMC are compressive; (2) the surface roughness is controlled by feed; (3) particle pull-out influences the roughness when feed is low; (4) particles facilitate chip breaking and affect the generation of residual stresses; and (5) the shear and friction angles depend significantly on feed but are almost independent of speed. These results reveal the roles of the reinforcement particles on the machinability of MMCs and provide a useful guide for a better control of their machining processes

Development of a ripple Ice cream using sour sop (Annona muricata L.)

Sour sop (Annona muricata L.) is an underutilized fruit crop in some countries like Sri Lanka although in some other countries like Mexico, Venezuela and Peru, it is being cultivated in at commercial levels and is used to develop comminute products. The awareness on this fruit and its functional properties among Sri Lankan consumers is very low, especially in urban areas, but it grows in several areas up to 460 m elevations. Today studies have been initiated on Soursop as it is found to have medicinal and therapeutic values. A study was carried out to develop Soursop based ice cream for commercial applications. Therefore, a Soursop ripple ice cream was developed, using soursop as a new fruit to the food processing industry as well as a new choice for consumers. The present study involved the selection of good quality fruits, preparing soursop puree and preserving it and preparing a fruit sauce for the ice cream. Moreover the product was subjected to several sensory evaluations, chemical analyses, microbiological assessments and storage. Significant amount of crude fibre 0.13 (%w/w) is obtained for the ripple ice cream. This ripple ice cream was successful in acceptability and keeping quality. Good melting quality with acceptable definite melting was obtained for the ice cream. The ice cream satisfied the SLS standards Ice cream (SLS 223:1989). This study was expected to popularize the sour sop as a potential ingredient for manufacturing value added products. The fruit content is about 20% in this ice cream product

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

Tribology of Medical Devices

Importance of tribology in a number of medical devices and surgical instruments is reviewed, including artificial joints, artificial teeth, dental implants and orthodontic appliances, cardiovascular devices, contact lenses, artificial limbs and surgical instruments. The current focus and future developments of these medical devices are highlighted from a tribological point of view, together with the underlying mechanisms