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1

Effect of laser cutting parameters on surface quality of low carbon steel (S235)

Zaied M, Bayraktar E., Katundi D., Boujelbene M., Miraoui I

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 54, nr 1

128--134

EN

Purpose: This work analysis surface roughness parameters as a function of Laser power and cutting speed. The surface roughness parameters are determined after statistical analysis (ANOVA) and propose a simple mathematical model. Design/methodology/approach: Machining were carried out by Laser cutting (CO2) of sheet metal (low carbon steel, S235) produces different surface quality. The statistical processing of the experimental results enabled development of a mathematical model to calculate the cut surface quality according to the cutting parameters used in the present work. Findings: The prediction of surface roughness values according to the mathematical model are very precisely analysis and determining of surface roughness values is a very practical tool by the experimental design method. It enables a high quality range in analysing experiments and achieving optimal exact values. A rather small experimental data are required to generate useful information and thus develop the predictive equations for surface roughness values as Ra, Rt and Rz. Depending on the surface roughness data provided by the experimental design, a first-order predicting equation has been developed in this paper. Practical implications: A simple and practical tool was proposed with the experimental design for predicting the surface roughness values as a function of variables of Laser power and cutting speed for a low carbon steel (S235). This type of analysis gives detailed information on the effect of Laser cutting parameters 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 cutting speed the most important influence on the surface roughness.

2

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.

3

A mathematical model to choose effective cutting parameters in electroerosion, EDM

Medfai A., Boujelbene M., Bayraktar E.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 47, nr 1

97--102

EN

Purpose: Machining by electroerosion is a process of removal of material by fusion, vaporization and erosion, reserved essentially for conductor and semiconductor materials. It can be used to machine metals and alloys, the tempered steels, different type of ceramic alloys, other metallic carbides and even for harder materials such as polycrystalline diamond etc. The aim of this paper is to develop a mathematical model for the effect of cutting parameters on the machining by electro discharge machining used widely in industrial applications. Design/methodology/approach: It is about a study and detail analyzes effect of the cutting conditions in machining by electroerosion of steel 42CD4-42CrMo4 on the surface quality of the parts. The statistical method of the analysis of variance “ANOVA” makes it possible to release the considerable effects of the parameters of cut on the criteria of performance of machining by electroerosion, EDM. Findings: The result of the study shows that the nature of the electrode used and the different grades of the materials machined by Electro Discharge Machining, EDM, influence considerably the volume of the removal of material and the surface quality of the produced parts. However, more the resistivity of the electrode increases, more relative wear of the electrode will be important and more the volume of removal of material decreases. Research limitations/implications: This study needs more experimental results for evaluation of the cutting parameters in detail and introduce in the model developed here. Practical implications: This model developed based on the experimental study gives very simple choice of cutting parameters depending on the materials. Originality/value: A very simple model has been develop here after a comprehensive study and this model contains an experimental design, and application ANOVA analysis as a function of experimental results and allows to obtain a smooth surface and high quality machined pieces and can decrease at cost price of the pieces in the manufacturing engineering.

4

Influence of workpiece inclination angle on the surface roughness in ball end milling of the titanium alloy Ti-6Al-4V

Daymi A., Boujelbene M., Linares J. M., Bayraktar E., Ben Amara A.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 35, nr 1

79-86

EN

Purpose: The aim of this work is to provide an in-depth understanding of the surface texture produced by various workpiece inclination angles using high speed finish ball end-milling of the titanium alloy Ti-6Al-4V. Design/methodology/approach: This paper presents an approach to develop a mathematical model of surface roughness in end-milling by the experimental design methodology. Machining variables such as cutting speed, feed and radial depth of cut, which are easily controllable, are considered in building the model. The influence of the workpiece inclination angle on the surface roughness of the machined workpiece was also investigated. Findings: According to the mathematical model, an increase in either the feed or the radial depth of cut increases the surface roughness, whilst an increase in cutting speed decreases it. The radial depth of cut ae is the most significant parameter in the model. Results analysis of the 2D/3D surface roughness parameters of the machined parts shows the improvement of the surface roughness quality when it is machined with a workpiece inclination angle of 25°. Research limitations/implications: As perspectives of this work, we can study the influence of the different machining strategies on the surface integrity of this titanium alloy, including the study of the residual stress. Practical implications: We propose to study the improvement of the surface quality of the orthopedic prostheses, which is an influencing parameter in their lifetime, by implementing the high speed cutting technique. The mathematical model of the surface roughness is a very important result of this work. In fact, it allows selecting the best cutting conditions to obtain a better workpiece surface quality. Originality/value: In this work, three dimensional surface roughness parameters were studied: the 3D surface topographies were obtained using a 3D measurement station and the mathematical model of Sa. The arithmetic mean deviation of the surface was established in order to minimize the experimental works and to have an idea about the surface roughness evolution as a function of cutting parameters.

5

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.

6

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.

7

Study of the milling strategy on the tool life and the surface quality for knee prostheses

Boujelbene M., Abellard P., Bayraktar E., Torbaty S.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 31, nr 2

610-615

EN

Purpose: The aim of this research is to make a study about the influence of the tool trajectory's generation on its tool life and the improvement of the surface quality in multi-axis milling at high speed machining of the knee prostheses. The material used for this study is the titanium alloy Ti-6Al-4V ELI (TA6V ELI) for implant. Design/methodology/approach: The methodology has consisted on proving a serie of parameters combinations with various machining configurations and various programs of the tool trajectory's generation in three and five axes (the axis of the tool is maintained normal on the machined surface by rotation around Y axis; the axis of the tool is maintained according to axis Z; the axis of the tool is tilted around the Y axis). And determined the influence of the machining strategy over of the tool life. Findings: The knee prostheses are constructed with important mechanical resistance materials with complex form, which require high performance cutting tools and high cost. The good generation's trajectory of the cutting tool in multi-axes milling permits to minimize flank wear. High speed Machining offers a considerable profit in the capacity of surface quality, duration of the machining and polishing operations and consequently in improvement productivity. But the choice of the cutting speed must be recommended by the couple tool-materials. Research limitations/implications: A possible future work would be the development of a general the phenomenal of the residual stress of various machining configurations and various programs of the tool trajectory's generation and the knee protheses life. The behaviour of the residual stress studies are planed in the future. Practical implications: The relationship found between the milling strategy on the tool life and surface quality work piece has an important practical implication since it allows selecting the best cutting condition for knee prostheses. Results are of great importance in the quality of articulation surface so the cartilage in medicine 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. This paper could be an interesting source of information for engineers and researchers who work with machining knee prostheses.

8

Variation cutting speed on the five axis milling

Boujelbene M., Moisan A., Bouzid W., Torbaty S.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 21, nr 2

7-14

EN

Purpose: The aim of this research is to make a study of the effective cutting speed variation in milling with a ball end tool. Then an experimental study of the effect of finishing strategies on surface texture, roughness is described. The material of a specific HB 300 pre-hardened mould steel Super Plast (SP 300). Design/methodology/approach: The methodology has consisted to determine cutting speed of each mode of tilt tool in five axes machining, and of proving a series of configurations and parameters combinations: cutting speed Vc, feed rate Vf, and tilt tool in multi-axis milling. Findings: This paper has investigated the effect of the tool orientation on the variation effective cutting speed, on the surface texture, while multi-axis milling. Experimental results have shown that disadvantages of three axes machining results from the existence of very low cutting speeds, even null when the tool axis is normal to the machined surface. This mode of machining generates a bad surface quality. Surfaces have a poor topography and important anisotropy. A suitable slope of the cutting tool by the means of the fifth machine tool axis, improves considerably work piece machined surface quality; Good micro-geometrical surface topography and lower surface roughness. Research limitations/implications: A possible future work would be the development of a general the phenomenal of the residual stress of the cutting on the five axis machining. The behavior of the residual stress studies are planed in the future. Practical implications: The relationship found between the effective cutting speed and surface texture work piece 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 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.