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1

Elastomeric matrix composites: effect of processing conditions on the physical, mechanical and viscoelastic properties

Zaimova D, Bayraktar E., Katundi D., Dishovsky N

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 50, nr 2

81--91

EN

Purpose: The aim of this study is to investigate the influence of accelerator-vulcanizing agent system and the vulcanization temperature on the properties of vulcanizates based on Natural rubber/Polybutadiene rubber (NR/ BR) compounds. This preliminary study will allow optimizing the composition for improving the mechanical properties and understanding the damage behaviour. Design/methodology/approach: NR/BR based composites with different vulcanization temperatures and curing systems were characterized in respect of their curing characteristics (for 140°C and 160°C) and mechanical properties. The cure characteristics of the rubber compounds were studied by using the Monsanto MDR 2000 rheometer. The mechanical properties were investigated- tensile strength, elongation at break, tensile modulus at 100% (M100) and at 300% (M300) deformation. The hardness (Shore A) and molecular mass of the samples were also determined. Scanning electron microscopy was used to study the microstructure of the fracture surfaces. Findings: The processing, physical, mechanical and viscoelastic properties and chemical structure of the mixture of Natural rubber/Polybutadiene rubber (NR/BR) compounds have been evaluated in detail for the compounds of D1 and D2 (140/160). Research limitations/implications limitations/implications: Some critical point, control of the temperature during vulcanization in press, can introduce some restrictions; these measurements can play on the final vulcanizates and in the course of processing. Practical implications: In practical way, mechanical test results (tensile and shore A) give very useful information about the damage behaviour of the elastomeric matrix composites. Originality/valut: Natural rubber/Polybutadiene rubber (NR/BR) compounds were mixed by additions of some certain elements to improve physical, mechanical and viscoelastic properties and damage behaviours of these compounds produced under certain conditions.

2

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.

3

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.

4

Toughness of welded stainless steels sheets for automotive industry

Bayraktar E., Katundi D., Yilbas B S, Claeys J

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 44, nr 1

35--41

EN

Purpose: In the automotive industry, more and more it is compulsory to develop new grades of stainless steels, such as high resistant Martensitic Stainless Steels (MA-SS) and Ferritic Stainless Steels (FSS) in order to realise certain or many complex deep drawn pieces. For these grades, resistance spot welding (RSW) is the most widespread process used largely for many parts of the car body in the automotive industry. This paper aims to characterise mechanical behaviour (toughness) of the different steel grades under dynamic test conditions. Design/methodology/approach: A special crash test device is used in different temperatures and the simulated crash tests are performed at a constant speed of 5.52 m/s. Findings: The specimen is submitted to impact tensile test at different temperatures. According to testing temperature, fracture mode varies: At low temperatures, brittle fracture occurs: due to stress concentration, fracture always occurs in the notched section. At high temperatures, the specimen fails by ductile fracture. Toughness of the steel sheets (base metals, BM or welded parts) is well compared at different materials and test conditions. Research limitations/implications: Evaluation of welded thin sheets submitted to the dynamic loading in order to correlate in real service conditions in order to realize a useful correlation between the transition temperature and deep drawability can be used for evaluating of the welding conditions and also of the material characteristics. For detail study, this type of the test needs a standard formulation. Practical implications: This is a new conception of specimen and of the impact/crash machine. It is widely used in automotive industry for practical and economic reason to give rapid answers to designer and also steel makers for ranking the materials. Originality/value: New developed test called impact crash test for evaluating the toughness of thin welded joints (tailored blanks) / mechanical assemblies in high formability steel sheets for stamping submitted to dynamic loads such as experienced in real crash tests.

5

Damage analysis of the ceramic reinforced steel matrix composites sheets: experimental and numerical study

Bayraktar E., Ayari F., Katundi D., Chevalier J.-P., Bonnet F.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 49, nr 1

53--61

EN

Purpose: of this paper reports damage analysis of TiB2 (ceramic particles) reinforced steel matrix composite sheets. This new steel composite receives much attention as potential structural materials due to their high specific strength and stiffness. The goal of the research described in this paper is to study the usage of this new steel family in the manufacture of light structures. Design/methodology/approach: therefore in this study is focused to the titanium diboride TiB2 reinforced steel matrix composite sheets that they were characterized by optical and scanning electron microscopes after the mechanical tests carried out on the base metal and welded specimens under dynamic and static test conditions. Findings: The non homogeneity of the structure in this type of composites makes deeply complexity of their numerical and analytical modelling to predict their damage during the loading. For example, the interfaces essentially play a key role in determining mechanical and physical properties. For this reason, a Finite Element (FEM) analysis is used for modelling to simulate the macroscopic behaviour of this material, taking into account the relevant microscopic scales. Practical implications: defined in this research is based on the impact dynamic behaviour of this steel sheets by using a special impact tensile test developed formerly that all details were published in this journal. This type of test gives more comprehensible information about special steel sheets (welded or base metal) in case of dynamic crash conditions. Originality/value: The present research gives detail information on the new steel matrix composite sheets reinforced TiB2 ceramic particles. This new composite was developed by ARCELOR research group and impact dynamic behaviour and weldability of the welded parts and base metals from this composite steel are discussed here in order to give practical and useful solution for industrial applications.

6

Development of a new aluminium matrix composite reinforced with iron oxide (Fe3O4)

Bayraktar E., Katundi D.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 38, nr 1

7-14

EN

Purpose: of this paper is to develop new aluminium matrix (intermetallic) composites reinforced with iron oxide (Fe3O4) that will be used in aeronautical engineering or in electronic industry. Different parameters such as sintering time and temperature, reinforcement, compact pressure were evaluated. The final purpose of this project is going on to improve conductivity and magnetic permeability of this new composite. Design/methodology/approach: In this paper, a new alternative materials “aluminium–iron oxide (Fe3O4, naturally as the mineral magnetite) powder composite” has been developed by using a microwave (in the laboratory scale) sintering programme with various aspect ratios, that iron oxide (Fe3O4) particle sizes and aluminium powders together were prepared. This paper contains partially preliminary results of our going-on research project. Findings: Green density increased regularly depending on the compact pressure and percentage of the iron oxide (Fe3O4). Micro and macro porosity was not found due to very clean microwave sintering. Density after microwave sintering was higher than that of traditional sintering in an electrical oven. Research limitations/implications: This project is going on and magnetic permeability and conductivity of this composite will be improved. Practical implications: This composite is new and clean and thanks to the new microwave sintering basically will be used in aeronautical engineering. Microwave heating results in lower energy costs and decreased processing times for many industrial processes. Originality/value: Originality of this paper is to use a new reinforcement in the aluminium matrix composite; Fe3O4-iron oxide. A new method - microwave sintering- has been carried out on this composite.

7

Corrosion behaviour of the welded steel sheets used in automotive industry

Katundi D., Tosun-Bayraktar A., Bayraktar E., Toueix D.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 38, nr 2

146-153

EN

Purpose: of this paper is to characterise the corrosion resistance in the steel sheets (Hot dip galvanizing of steel sheets) used in automotive industry. In fact, corrosion of automotive components by road salt is a widely known problem. The different parts under the car body and the interior surface of body panels suffer easily from the corrosive products deposited on roads and used mainly to melt snow. A comparison in a chemical investigation of the corrosion rate for base metals (without welding) and welded steel is required. Therefore, conformity will be accomplished between the corrosion phenomena in simulated corrosion tests and those in actual cars. Design/methodology/approach: Simulated corrosion tests, wet/humidity test and hot dust/dry cycle talk test carried on in laboratory conditions was investigated quantitatively. Dynamic behaviour of the corroded specimens have been tested dynamically to simulate under the crash test conditions. Findings: Studies carried out on the vast corroded samples have shown that the pitting corrosion damage and crack initiation sites have began and propagated generally in the HAZ in the welded steel sheets (Tailored welded blanks - TWB). Research limitations/implications: This paper contains partially results of a common research project. Some limitations exist in application of hot dust/dry cycle talk to the real open air test conditions. All of these results were carried out in the laboratory conditions. Practical implications: The problem is of extreme importance to all academic, scientific, manufacturing, maintenance and industrial societies. The outcome of the proposed study will contribute to the industrial application of ARCELOR-MITTAL. The proposed study will be benefit not only for the car industry and steel makers, but also important for the other industrial applications. The proposed research can be employed in a broad range of applications in oil and natural gas industries. This project will promote multidisciplinary research and cooperation between university and industry. Originality/value: An effective corrosion test proposed by Volvo was applied to the welded sheets (TWB) in an enclosed climatic chamber. This test is a practical and inexpensive test. Impact tensile-crash test makes it possible to analyse the corrosion damage of sheet metals under the dynamic rupture.