M. KHALFALLAH Fares

The objective of this experimental study is to utilize rotary friction welding (FW) for assembling similar polyamide materials. The application of the SVM approach enables the development of a predictive model for estimating mechanical properties in RFW processes. Furthermore, the optimization of RFW parameters through GA proves pivotal in selecting optimal welding conditions, providing a variety of choices. The welding parameters considered in this study included rotation speed at five levels and traverse speed at three levels. The strength of the welded samples was characterized by a tensile test. Additionally, temperature measurements were taken to determine the maximum temperature in the joint area. The results demonstrated the dependence of tensile strength and maximum temperature on the rotation speed. Maximum tensile strength is achieved at an optimal rotation speed. Moreover, analysis of variance (ANOVA) indicates that rotation speed is the parameter most influenced by tensile strength.

In this work, we carried out a numerical study of the stationary laminar flow by mixed convection in a ventilated two-dimensional cavity containing a cold cylinder in the center of the latter. The cavity is filled with different hybrid nano-fluids, (Water/Ag-TiO2) and (Water/Al2O3-TiO2)). The cavity containing two gates (Orifices) of entry and exit of the flow, for a Reynolds number (Re) fixed so that the Richardson number takes the values: Ri = 0.1, 1, 10 and 100, and a volume fraction of the nanoparticles comprised between (0% and 8%). The square cavity is heated isothermally by the surface of the lower wall by a heat source (The source is to maintain the lower wall at constant temperature), the other walls are maintained adiabatic. The equations, which govern the flow, have been solved numerically using the finite volume method. The results obtained show that the heat transfer increases with the increase in the volume fraction and the Richardson number. Thus the heat transfer rate (Nu) increases with the increase in Ri.

This experimental work aims to study the effect of variations of rotary friction welding
parameters on the thermal behavior and mechanical properties of dissimilar joints stainless
steel/copper. To achieve this objective, a rotary friction welding process of AISI 316L stainless
steel rods with copper rods was carried out, using a milling machine as the friction welding
machine, with changing the rotational speed, and measuring the temperature changes of the
joints during the welding process. After welding, the joints were subjected to tensile tests to
evaluate their mechanical strength. The experimental results showed a strong relationship
between the rotational speed and the thermal behavior of the joints, and the strength of the
joints is also affected by the changes of the rotational speed.

Dans l’industrie moderne, les métaux et les céramiques sont parmi les matériaux les plus utilisables. Les métaux, qui se devisent en deux grandes familles, ferreux et non ferreux, ont des propriétés particulières telles que la bonne malléabilité, la grande ductilité et la conductivité électrique et thermique élevée. Les céramiques, et en particulier le céramiques techniques, possèdent certaines propriétés supérieures à celles des métaux, comme la dureté élevée, la résistance à l'usure, la bonne résistance mécanique et chimique, mais malgré ça leur usage est limité à cause de la fragilité et la faible résistance aux chocs.
Pour éviter cette limitation d’usage, des joints dissimilaires métal/céramique on été développé a fin de combiner les caractéristiques des métaux et celles des céramiques.

This experimental study aims to determine the effect of rotational speed on the properties of friction welded joints of mild steel and AA1100 aluminum alloy. The welding process was developed by a continuous drive friction welding machine and the effect of the rotational speed was investigated through temperature measurements in the aluminum part, strength tests and microhardness measurements. The results show that the properties of the seals are affected by variations in rotational speed. The thermal analysis helped to understand the relationship between the maximum temperatures reached during the welding process and the mechanical properties of the joints.

Le but de ce travail est d’obtenir des joints dissimilaires acier/céramique en utilisant le soudage par friction
rotative. Dans cette étude, le soudage par friction des tiges en acier doux avec des tiges en alumine (Al2O3) a été
réalisé en utilisant un alliage d'aluminium 1100 comme une couche intermédiaire d'épaisseur de 3 mm. Le
processus de soudage a été effectué en deux phases. Tout d'abord, les tiges d'acier et les tiges d'aluminium ont
été soudées par friction, et les joints résultants ont été usinés pour former la couche intermédiaire. Ensuite, ces
joints ont été soudés par friction aux tiges d’alumine. Dans la première phase, les paramètres de soudage par
friction acier doux/aluminium 1100 ont été optimisés à l'aide de la méthode des surfaces de réponse (MSR) pour
atteindre une résistance maximale des joints. Selon cette approche, des joints acier doux/aluminium AA1100 et
acier doux / alumine ont été développés avec succès par un procédé de soudage par friction rotative et ont été
évalués par des essais mécaniques, tel que l’essai de traction, l’essai de flexion à trois points et les mesures de
microdureté Vickers. La microstructure des joints résultants a été observée par microscopie optique (MO) et
microscopie électronique à balayage (MEB), en particulier à la zone d’interface. Les joints ont également été
examinés par spectroscopie par dispersion d'énergie (EDS). Sur la base des résultats du MSR, une relation
empirique a été établie pour prédire les propriétés mécaniques des joints acier doux/aluminium 1100 soudés par
friction. Les résultats expérimentaux ont montré que la résistance et la microstructure des joints acier
doux/aluminium 1100 et acier doux/alumine dépendent largement des paramètres du procédé de soudage par
friction.

This paper is a contribution to the study of weld ability of AA2014 aluminum alloy by using thermal cycle simulation. It presents the microstructures obtained after thermal cycle simulation of welding by rapid heating and cooling treatments in a specific simulation equipment. Optical microscopy, X-ray diffraction, and micro hardness measurements were used as characterization techniques. Micro structural and mechanical details of the heat affected zone of the real welded joint realized by TIG welding process were compared to the simulated heat affected zone by the thermal cycle simulation in specific equipment.

The objective of this work is to investigate the rotary friction welding of AA1100 aluminum alloy with mild steel, and to optimize the welding parameters of these dissimilar materials, such as friction pressure/time, forging pressure/time and rotational speed. The optimization of the welding parameters was deduced by applying Response Surface Methodology (RSM). An empirical relationship was also applied to predict the welding parameters. Tensile test and micro-hardness measurements were used to determine the mechanical properties of the welded joints. Some joints were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) in order to investigate the formation of intermetallic compound (IMC) layer at the weld interface. Experimentally, the tensile strength of the weld increases with increasing the forging pressure/time, while the low level of forging pressure/time allows the formation of an IMC layer which reduces the tensile strength of the weld.

The friction welding technique has been widely used in modern manufacturing processes, due to its significant advantages like material saving, short production time and high quality of welded joints. There are several friction welding processes, rotary, linear, angular and orbital. In the rotary friction welding (RFW) process, one of the workpieces was axially pressed against the other which is turned. The generated heat, by the friction between the workpieces faces, leads to the plasticization of the surfaces in contact. When the surfaces are sufficiently plastics, the rotation halted and the axial pressure increased to forge and consolidate the formed joints. In the present work, an experimental device has been designed and mounted to perform a dissimilar friction welded joints copper/aluminum. The experiments were conducted in order to study the effect of rotational speed, as the variable welding parameter, on the mechanical properties and the thermal behavior of joints. The mechanical properties of the joints were evaluated by the three point bending test and microhardness measurements. In addition, temperature measurements were done to determine the peak temperature in the area nearly the weld. The results showed the strong dependence between the rotational speed and the properties of welded joints.

In recent years, the joining of aluminum and steel has received considerable attention in the automotive industry with the aim of reducing the vehicle weight, energy saving and environmental protection by exploiting the advantages of steel, such as good mechanical properties, and those of aluminum, such as low weight and good corrosion resistance. The rotary friction welding (RFW) is one of the most suitable processes for joining aluminum to steel. It is a solid state joining process that generates heat through mechanical friction between a moving and a stationary work piece. A several parameters affect the quality of welds, such as welding time, pressure and rotational speed. In this study, the effect of friction time on the properties of AA1100 aluminum alloy-mild steel joints to obtained by rotary friction welding was investigated. The welding process was developed by a continuous drive friction welding machine. A series of experimental tests, such as microhardness measurements, strength tests and temperature measurements were performed in conjunction with a thermal modeling to predict the temporal variation of temperature in the aluminum part. The numerical simulation was developed by Finite Element Analysis (COMSOL) software, and the numerical predictions were compared with thermocouple data recorded from real welds conducted under identical conditions. The results show that the properties of joints are affected by the friction time variations. Thermal analysis also helped to understand the relationship between the maximum temperatures reached and the mechanical properties of the joints as well as the quality of the weld. From the simulation results, the predicted and measured temperature values are in fair agreement.

Dissimilar metal joining offers the potential to utilize the advantages of different materials often providing unique solutions to engineering requirements. The main reasons for dissimilar joining are due to the combination of good mechanical properties of one material and either low specific weight or good corrosion resistance or good electrical properties of second material. Consequently, joining processes for dissimilar materials have received considerable attention in the recent years. Much of this activity has focused on the transportation industries such as aerospace, aviation, shipbuilding, railway transportation. This is especially in the automotive industry due to the potential weight reduction of both vehicle components and structures. Friction welding is a joining technique used to joint various materials in manufacturing process. The method has widespread use since 1950, it is a solid state joining process that generates heat through mechanical friction between a moving work piece and a stationary component.
This paper presents a numerical simulation on thermal analysis of friction welded ceramic/aluminum joint by Finite Element Analysis (COMSOL) software. The selected materials are AA1100 aluminum alloy and Alumina as a ceramic. The considered geometry for simulation is rods of 12 mm diameter and 60 mm length. In order to validate the numerical model, a similar experimental work was developed by a direct friction welding machine. Just the effect of rotational speed on temperatures variation was investigated, which means that the other welding parameters were kept constants, and only the results of temperature measurements at aluminum interface were done.
Using the numerical heat generation, the predicted temperatures matched closely to the experimental data. Moreover, the experimental results show a maximum interfacial temperature of ~ 350 °C below the melting point of aluminum (650°C).
The ceramic-aluminum bond is strongly present in industrial tools, due to the need to combine the properties of metals, such as ductility, thermal and electrical conductivity, with ceramic properties like high hardness, corrosion and wear resistance. In recent years, some joining techniques have been developed to achieve a good bonding between these materials such as brazing, diffusion bonding, ultrasonic joining and friction welding.

The ceramic-Aluminum contact has strongly existed in modern tools, due to the particular combination of metal properties such as ductility, high electrical and thermal conductivity and the ceramics properties like the high hardness, the corrosion and the wear resistance. In recent years, a several techniques have been developed to achieve good contact or total bonding between these materials such as diffusion bonding, brazing, ultrasonic joining and friction welding.
In this experimental work, AA1100 aluminum alloy rods was friction welded to Alumina 99.9 wt% ceramic rods, and the effect of friction time on mechanical and structural properties of welded joints are investigated. The welding process was carried out by a direct friction welding machine. The welding specimens were rotated at a constant rotational speed of 900 rpm, a friction pressure of 20 MPa, a forging force of 18 MPa and a forging time of 3 sec. Three different friction times were applied 4, 5 and 6 seconds. Three point bending test and Vickers microhardness measurements are used to evaluate the strength of joints and study the mechanical properties in weld region. The microstructures of joints and fracture surface of the joint interface were examined by optical microscopy, SEM and EDS.
The experimental results show that bending strength increases with increasing friction time. The SEM observation shows that the increase in friction time led to the appearance of cracks in the microstructure of the interface area, which means that the long heating rate influenced the microstructure of the weld.

The aim of this experimental work is the joining of similar materials of High Density Polyethylene (HDPE) using the friction stir welding process. A Full-factorial design was used as a statistical approach to analyze the effect of processing parameters on mechanical behavior of welded joint. The welding parameters considered in this study were rotational speed in five levels and traverse speeds in three levels. The strength of welded samples was characterized by tensile test. In addition, temperature measurements were carried out to determine the peak temperature in the joining zone. The results have showed the dependence of tensile strength and peak temperature on rotational speed. A maximum tensile strength was achieved at optimum rotational speed value. Moreover, the analysis of variance (ANOVA) indicates that rotational speed is the most influenced parameter in strength of joints.

Reinforced concrete beams must have an adequate safety margin against bending and shear forces. Therefore, it will perform effectively during its service life. The aim of this work is to optimize the parameters of strength reinforced concrete beam, such as strength concrete, of stirrup spacing, and stirrup inclined presenting the techniques of characterization. An optimization of the reinforced concrete beam parameters was developed using the Response Surface Methodology (RSM). A flexural test was performed on reinforced concrete beam, and an empirical relationship was developed and used to predict the optimized strength reinforced concrete beam parameters.