Analysis of chip formation mechanism in machining of Al/SiCp metal matrix composites

Al/SiCp composites are known to cause a significant wear of cutting tools. But, with the use of PCD/CBN tools, machining can be continued over longer time duration. Nevertheless, the problem associated with the quality of machined surfaces such as pit marks and particle pull-out still persists. The quality of surface generated during machining can be easily related to the types of chips formed during machining of Al/SiCp composites as a function of processing conditions and composition of constituents in composites. It is observed from the Taguchi method-based experimentation using L(27) (3(13)) orthogonal array, that in machining of coarser reinforcement composites complete gross fracture takes place causing smaller segments of chips and higher shear plane angle. However, in finer reinforcement composites, secondary crack formation is evident at inner surfaces of the chips formed. Conceptual models illustrating these effects have been arrived at. (C) 200

Modeling of chip-tool interface friction to predict cutting forces in machining of Al/SiCp composites

In Al/SiCp metal matrix composites, in addition to machine, tool and process-related parameters, a change in composition (size and volume fraction of reinforcement) has a influence on machining force components. In the analytical models in the literature, the effect of abrasive reinforcement particles, which affects the coefficient of friction and consequently the friction angle, has not been considered while predicting cutting forces in machining of MMCs. In this paper, chip-tool interface friction in machining of Al/SiCp composites has been considered to involve two-body abrasion and three-body rolling caused due to presence of reinforcements in composites. The model evaluates resulting coefficient of friction to predict the cutting forces during machining of Al/SiCp composites using theory of oblique cutting. Further, the model considers various frictional forces on the wiper geometry on the cutting edge that has been found to improve the integrity of machined surface on composites. The predicted cutting force values were found to agree well with the corresponding experimental values for finer reinforcements composites with the assumption that 40% of the reinforcement particles contribute to the abrasion at chip-tool interface. However, for the coarser reinforcement composites, assumption that the 60% of the particles contribute to the abrasion yields better results. (C) 200

CUTTING FORCES AND SURFACE ROUGHNESS IN MACHINING Al/SiCp COMPOSITES OF VARYING COMPOSITION

Knowing that the machined surface roughness of Al/SiCp composites is linked to its performance, this paper presents an elaborative experimentation using Taguchi methods on four composites to analyze the effects of size (15m and 65m) and volume fraction (20% and 30%) of reinforcements in the composites on machining forces and machined surface roughness. The independent variables in the experiment were: tool nose radius, cutting edge geometry, feed rate, cutting speed and depth of cut. The results show that, of the three machining force components, only radial force shows significant dependence on composition of composites. The machined surface roughness was found to be more sensitive to a change in size than to volume fraction of reinforcement in composites. However, all the independent variables, except the cutting speed, cause a statistically significant effect on the machined surface roughness for all composites. An analytical model giving a correlation between the machined surface roughness and the ratio of cutting forces [image omitted] was formulated based on the geometry of work-tool contact. The predicted surface roughness using the model was found to agree well with the experimental values, especially when the tool nose radius is less than the depth of cut

CUTTING FORCES AND SURFACE ROUGHNESS IN MACHINING Al/SiCp COMPOSITES OF VARYING COMPOSITION

Knowing that the machined surface roughness of Al/SiCp composites is linked to its performance, this paper presents an elaborative experimentation using Taguchi methods on four composites to analyze the effects of size (15m and 65m) and volume fraction (20% and 30%) of reinforcements in the composites on machining forces and machined surface roughness. The independent variables in the experiment were: tool nose radius, cutting edge geometry, feed rate, cutting speed and depth of cut. The results show that, of the three machining force components, only radial force shows significant dependence on composition of composites. The machined surface roughness was found to be more sensitive to a change in size than to volume fraction of reinforcement in composites. However, all the independent variables, except the cutting speed, cause a statistically significant effect on the machined surface roughness for all composites. An analytical model giving a correlation between the machined surface roughness and the ratio of cutting forces [image omitted] was formulated based on the geometry of work-tool contact. The predicted surface roughness using the model was found to agree well with the experimental values, especially when the tool nose radius is less than the depth of cut

Surface finish and integrity of machined surfaces on AI/SiCp composites

The increasing applications of metal matrix composites (MMCs) for structural and wear resistant components in aerospace, automotive and recreational fields necessitated an in-depth analysis of quality of machined surfaces, which determines the ability of the material to withstand severe conditions of stress, temperature, corrosion, and controls its longevity and reliability. The introduction of compressive residual stresses in machined surface is known to alleviate the surface damage to some extent and help ensure better surface integrity. Based on this premise, this experimental work was carried out using CBN inserts with and without wiper on cutting edge and also by varying the other process parameters. During the experiments, cutting forces from the machining zone were monitored and after machining, surface finish, microstructure of the surface and the residual stresses in machined surfaces were measured. It was observed that the wiper geometry on the inserts reduces the surface damage and lowers the cutting forces. (C) 2007 Elsevier B.V. All rights reserved

Optimum Parameters for Machining Metal Matrix Composite

The need for optimum machining parameters has always been of paramount importance for metal cutting. The economics of the process largely depends on selecting the best machining parameters. However, the additional challenge of being environmentally friendly in production while still being cost effective is now imperative. Machining conditions are not always conducive in reducing the carbon footprint when cutting material with a low machinability rating. This is particularly pertinent when aerospace material such as Boron Carbide Particle Reinforced Aluminium Alloy (AMC220bc) is machined. This material falls under the category of a particulate reinforced Metal Matrix Composite (MMC), where the ceramic fibers disrupt the flow of electrons. The result is a decrease in thermal conductivity causing the tool interface temperature to increase, reducing tool life. This research will determine the optimum economic and sustainable machining parameters for this material