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Effect of cutting parameters on chip formation in orthogonal cutting

Ben Salem S, Bayraktar E., Boujelbene M., Katundi D.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 50, nr 1

7--17

EN

Purpose: of this paper is to study the chip formation to obtain the optimal cutting conditions and to observe the different chip formation mechanisms. Analysis of machining of a hardened alloy, X160CrMoV12-1 (cold work steel: AISI D2 with a ferritic and cementite matrix and coarse primary carbides), showed that there are relationships between the chip geometry, cutting conditions and the different micrographs under different metallurgical states. Design/methodology/approach: Machining of hardened alloys has some metallurgical and mechanical difficulties even if many successful processes have been increasingly developed. A lot of study has been carried out on this subject, however only with modest progress showing specific results concerning the real efficiency of chip formation. Hence, some crucial questions remain unanswered: the evolution of white layers produced during progressive tool flank wear in dry hard turning and to correlate this with the surface integrity of the machined surface. For the experimental study here, various cutting speeds and feed rates have been applied on the work material. Findings: The “saw-tooth type chips” geometry has been examined and a specific attention was given to the chip samples that were metallographically processed and observed under scanning electronic microscope (SEM) to determine if white layers are present. Research limitations/implications: This research will be followed by a detail modelling and need more experimental results for a given a good prediction of the results occurred on the damage related to the microstructure by using the cutting parameters. Practical implications: A special detail was given to the mechanism of chip formation resulting from hard machining process and behaviour of steel at different metallurgical states on the material during the case of annealing and or the case of quench operations. Originality/value: For the sake of simplicity, ANOVA (Analysis of Variance) was used to determine the influence of cutting parameters. It gives a practical and useful tool for the machining in the industrial operations.

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Prediction of surface roughness by experimental design methodology in Electrical Discharge Machining (EDM)

Ben Salem S., Tebni W., Bayraktar E.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 49, nr 2

150--157

EN

Purpose: This work models the Ra parameter as a function of current intensity (I), the electrode material and the work material. The surface is directly related to the average intensity (I) during machining. If the intensity is increased to 25 A, the roughness of the room rises dramatically to 15 microns. Design/methodology/approach: Machining with a copper tool produces a better surface than can be achieved by a graphite tool. Copper tool machining has been performed in an efficient way, eliminating the necessity of a large number of experiments. The statistical processing of the results enabled development of a mathematical model to calculate the machined surface quality according to the parameters of the cut used. Findings: The mathematical model, which precisely determines surface roughness, is a tool for cutting parameters and has been obtained by the experimental design method. It enables a high quality range in analysing experiments and achieving optimal exact values. A relatively small number of designed experiments are required to generate useful information and thus develop the predictive equations for surface roughness. Depending on the surface roughness data provided by the experimental design, a first-order predicting equation has been developed. Practical implications: The experimental design was proposed for predicting the relative importance of various factors (composition of the steels and electrical discharge machining (EDM) processing conditions) to obtain efficient pieces. This model gives detailed information on the effect of parameters of cut on the surface roughness. Originality/value: Experimental data was compared with modelling data to verify the adequacy of the model prediction. As shown in this work, the factor of intensity has the most important influence on the surface roughness.

3

Influence of machining parameters on the surface integrity in electrical discharge machining

Boujelbene M., Bayraktar E., Tebni W., Ben Salem S.

Archives of Materials Science and Engineering

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2009

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Vol. 37, nr 2

110-116

EN

Purpose: The aim of this research is to make a study of the influence of machining parameters on the surface integrity in electrical discharge machining. The material used for this study is the X200Cr15 and 50CrV4 steel for dies and moulds, dies castings, forging dies etc. Design/methodology/approach: The methodology consists of the analysis and determination of the white layer thickness WLT, the material removal rate MRR, the electrode wear ratio EWR and the micro hardness of each pulse discharge energy and parameters of electrical discharge machining. Findings: The Results of the tests undertaken in this study show that increasing energy discharge increase instability and therefore, the quality of the workpiece surface becomes rougher and the white layer thickness increases. This is due to more melting and recasting of material.With the increase of the discharge energy, the amount of particles in the gap becomes too large and can form electrically conducting paths between the tool electrode and the workpiece, causing unwanted discharges, which become electric arcs (arcing). these electric arcs damage the electrodes surfaces (tool and workpiece surfaces) and can occur microcracks. Research limitations/implications: A possible future work would be the development of a general the phenomenal of the residual stress of the wire electrical discharge machining in titanium alloys. The behavior is of the residual stress studies are planed in the future. Practical implications: The relationship found between the total energy of discharge pulses, composition of the steels and the type of machining on the surface integrity (the surface texture, the metallurgical surface aspect, the microhardness in the heat affected zone, HAZ) of different workpiece materials has an important practical implication since it allows selecting the best cutting condition combination from the points of view both the security and the economy for the established requirements in each case. Results are of great importance for aerospace and automotive industry. Originality/value: The paper is original since the bibliographical review has allowed testing that, although works about these themes exist, none approaches the problem like it has been made in this work. The paper could be an interesting source of information for engineers and researchers who work with machining dies and also significant complex parts in aeronautics.

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Effect of the cutting speed on the chip morphology and the cutting forces

Daymi A., Boujelbene M., Ben Salem S., Hadj Sassi B., Torbaty S.

Archives of Computational Materials Science and Surface Engineering

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2009

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Vol. 1, nr 2

77-83

EN

Purpose: The aim of this research is to make a first experimental analysis of the effect of the cutting speed on the chip morphology, and of the cutting forces in the orthogonal turning process of the titanium alloys Ti-6Al-4V. Design/methodology/approach: The methodology has consisted of proving a series of parameters combinations: f, feed rate, Vc, cutting speeds are explored in a range from 50 to 250 m/min, and is analyzing the different types of chips and the evolution cutting forces appeared during each one them, and determined the analytical model of plastic deformation ratio. Findings: Tests achieved have shown three main types of chips: Continuous chip at 50 m/min, Flow chip for speeds ranging around 100 m/min, and Shear localized chip starting from the transition speed of 125 m/min and above. The modification of the mechanism of chip formation is associated with the appearance of shearing instability. Chip segmentation by shear localisation is an important process which is observed within a certain range of cutting speeds. This phenomenon might be desirable in reducing the level of the cutting forces by improving chip's evacuation. Research limitations/implications: A possible future work would be the development of a general the phenomenal of the thermo mechanical of the cutting high speed machining. The behavior is of the thermo - visco - plastic studies are planed in the future. Practical implications: The relationship found between high speed machining and chip morphology and the cutting forces and work piece surface finish has an important practical implication since it allows selecting the best cutting condition combination from the points of view both the security and the economy for the established requirements in each case. Results are of great importance in for aerospace, biomedical and automotive industry. Originality/value: The paper is original since the bibliographical review has allowed testing that, although works about these themes exist, none approaches the problem like it has been made in work.