Advances in Materials Processing Technologies, 2006

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Authors: D. Moulin, O. Raymond, P. Chevrier, Paul Lipiński, Thierry Barre
Abstract: Machining of modern materials requires high performance tools. More than 60% of metal cutting tools used are coated to limit abrasive wear. As the harder material known to man, diamond and consequently Chemical Vapour Deposited (CVD) diamond coatings allow to increase performances of tungsten carbide tools, i.e. tool life, machined surface quality, and to decrease costs. However, CVD diamond coated tools quality is very dependent on the surface preparation as much as the fabrication process parameters. This paper aims to discuss the influence of pretreatments before deposition, and thermal stresses induced by the cooling operation. Diamond deposition process is described emphasizing the role of every step and its function. Some numerical simulations of the residual stresses at the interface are presented, enlightening that tool geometry is an important factor while using a coating, and that tools must be designed for the diamond coating.
Authors: E. Alegre, Joaquín Barreiro, H. Cáceres, L.K. Hernández, R.A. Fernández, M. Castejón
Abstract: Wear level of tool inserts in automated processes is tried using techniques of artificial vision. An application has been developed in Matlab that allows the acquisition of images with different resolutions and later on to process them. It is explained how the vision system used has been designed and implemented. The method for acquiring tool insert images and their treatment in the pre-processing, segmentation and post-processing is commented. First results are also presented using diverse texture descriptors. These first results must be corroborated carrying out new experiments with a bigger number of images.
Authors: Jose Antonio Sánchez, Luis Norberto López de Lacalle, Aitzol Lamikiz
Abstract: The use of Electrical Discharge Machining (EDM) for the manufacturing of moulds and dies is generally accomplished by using different cutting regimens, from roughing to finishing, until the specified surface finish and dimensional tolerances are met. Multistage planetary EDM can be used to simplify the production process. Benefits such as the reduction of machining time, the need for less electrodes, electrode wear minimization and the improvement of the final surface finish of the component can be obtained. Design of multistage planetary EDM strategies requires a sound knowledge of the optimum radius for each orbit that assures surface roughness and dimensional accuracy together with a minimum machining time. Therefore, it is necessary to know the “exact” value of the gap at each stage. In this paper the influence of different process variables on the design of multistage planetary EDM strategies is analyzed.
Authors: M. Sánchez Carrilero, Miguel Álvarez, E. Ares, J.R. Astorga, M.J. Cano, Mariano Marcos Bárcena
Abstract: Carbon Fiber (CF)/Metallic Alloy (MA) laminar structures, also known as Fiber Metal Laminates (FML) allow diminishing the airship weight. Because of that the use of these materials is growing continuously in the aerospace industry. These composites materials need to be drilled because of the assembly requirements in the different airship elements. The most common problems that can appeared when those structures are machined are related with the interaction of the tool with dissimilar materials, which need different cutting parameters for the optimized machining process. This work reports on the results about a study of the dry drilling processes of hybrid composites Carbon Fiber/aluminum alloy, and especially CF/AA2024.
Authors: S.H. Yeo, M. Murali, S. Balakrishnan
Abstract: Micro electro discharge machining is an important unconventional metal micromachining technology. The performance of micro EDM depends on the combination of the tool and work materials used. In the absence of a comprehensive theoretical model to predict the effect of electrode materials on the performance of EDM, experimental investigations as described in this paper become useful. The work materials studied include ferrous, non-ferrous and exotic material (XW42, Ti6Al4V, WC) and the tool electrode materials include the commonly used EDM tool materials namely tungsten, copper and graphite. It is found that in the microgroove machining by micro EDM using foil electrodes, graphite consistently provides higher material removal rate than tungsten and copper tool electrodes and hence it is useful for the rough machining. On the other hand tungsten tool electrode is preferable for finish machining as it provides the least surface roughness.
Authors: L. Castro, P. Viéville, Paul Lipiński
Abstract: This paper proposes an experimental method for obtaining the Frequency Response Function (FRF) between a dynamic force and the signals emitted by a piezoelectric dynamometer. This function is known as Transmissibility. In the FRF obtaining stage, different configurations of mounting and excitation have been compared to improve the function quality. The method has been developed with a three components dynamometer fixed on a milling machine. The FRF has two principal applications: it is used to evaluate the measurement system accuracy and to correct the measurements, if necessary. The method has been developed with the purpose of studying the cutting forces in machining process. Furthermore, it has been identified the influence of the parts of the measurement chain in the measuring system response.
Authors: C. Vallellano, C. Guzman, J. Garcia Lomas
Abstract: The present work analyses experimentally and numerically the failure limit of a 2024-T3 aluminium alloy sheet subjected to stretching. The capability of a number of ductile fracture criteria to predict sheet failure is examined and compared with experimental results. The influence of the hydrostatic pressure in the Freudenthal’s, the Cockcroft and Latham’s and the Bressan and Williams’ criterion is analyzed. The effect of the normal stress on the fracture plane in the Bressan and Williams’ criterion is also discussed.
Authors: D. Rodríguez Salgado, I. Cambero, F.J. Alonso
Abstract: The aim of the present work is to develop a tool condition monitoring system (TCMS) using sensor fusion and artificial neural networks. Particular attention is paid to the manner in which the most correlated features with tool wear are selected. Experimental results show that the proposed system can reliably detect tool condition in turning operations and is viable for industrial applications. This study leads to the conclusion that the vibration in the feed direction and the motor current signals are best suited for the development of a TCMS than the sound signal, which should be used as an additional signal.
Authors: J. Perez, R. Hunter, J.C. Hernandez, Antonio Vizan Idoipe
Abstract: Nowadays, the inspection process is an essential part of the manufacturing process, where a product is subjected to verification of the geometric features, dimensions and tolerance specifications with respect to the product design specifications. One of the most interesting topics in the automation of the inspection process is the right fixture design. In the fixture design process we have used the information provided by the part design and manufacturing process. However, the lack of integration and structuring of this information results in one of the most important problems, producing an increase in the time and cost implied in the development of the fixture design and its implementation. For this reason, this work presents a knowledge model for the inspection fixture design process for a Coordinate Measuring Machine (CMM), which allows the automation of the inspection fixture design process to be made easier, reducing time and cost associated to the inspection process and to the manufacturing process in general.
Authors: S. Mridha
Abstract: In gas nitriding the thickness of the case depth is reported to increase parabolically with processing time and ammonia content in the NH3/H2 gas mixture which consequently increases the thickness of undesirable surface iron-nitride (white layer). In this investigation two commercial grade low alloy steels were nitrided in gas atmospheres containing 10 to 80% ammonia at 4700, 5200 and 5700C for 6 to 96 h. A metallographic technique was used to reveal different zones of the nitrided surface and the thickness of the diffusion zone was recorded using microscope. The growth kinetics of the diffusion layer of these two steels were analyzed and compared with that of 3% chromium (En40B) steel from literature. The results of the investigation conclusively suggest that the growth rate of the nitrided layer for both steels reached to a maximum with the increase of ammonia content in the gas mixture up to an optimum level where the thickness of the white layer is a minimum. However, the growth rates of the nitrided case are different for different steels.

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