Papers by Keyword: Friction Stir Welding (FSW)

Abstract: In recent years, due to its extraordinary qualities, friction stir welding process FSW has found its utility in more and more industrial applications in fields such as: aerospace, aeronautics, naval, automotive and railway. The paper summarizes several achievements in the FSW joining of couples of similar and dissimilar materials used in the automotive industry. There are presented aspects regarding the welding of ferrous metal materials (DD13), couples of non-ferrous metallic materials (Al Cu range) and steels with aluminum. The behavior of FSW of material couples in terms of analysis of microstructural improvements and mechanical characteristics is analyzed. The preliminary results obtained have shown that the FSW process can be successfully applied to the joining of the approached material couples, but with the use of optimized welding tools and technologies.

Abstract: There are various base metals that might be subjected to friction stir welding (FSW). They have different yield strength, ultimate tensile strength and other mechanical characteristics that influence the complex phenomena of the FSW process. The nature, mechanical characteristic and other properties of the base metals introduce also certain requirements for the FSW equipment, because FSW is a mechanical process.Experimental data of the FSW of the following materials are presented and compared:- similar overlapped sheets of aluminium alloy EN AW 5754, having the thickness 1.0 mm; - dissimilar overlapped sheets of 3 - 6 mm thickness of the base metal couples: aluminium alloy EN AW 1200 / copper Cu 99 ET, aluminium alloy EN AW 5754 / copper Cu 99, aluminium alloy EN AW 6082 / copper Cu 99 ET;- sheets of nickel alloy, inconel 718, thickness 8 - 10 mm, by friction stir processing. The characteristics of the FSW tool are described and the main technology parameters are mentioned: overlap, rotational speed of the FSW tool, rotational direction, travel speed, thrust force, as well as electric current of the motor for the rotating motion of the tool.Other important factors are also taken into account: sizes and positioning of the sheets (up or down), rolling direction of the sheets, room temperature, temperature of the sheets, material and temperature of the support plate.The linear energy of the FSW process is the main parameter. This is an indirect parameter, because it must be calculated, based on the previous mentioned parameters. According to the definition, the linear energy depends directly on the mechanical power developed during the stirring process, respectively it depends indirectly on the travel speed.On the other hand, the heat input is directly proportional to the linear energy and the thermal efficiency of the transfer of the heat produced by the friction of the shoulder and pin, to the nugget zone, where the weld metal is produced. These quantities are also analysed.For these materials the power developed by the motor for the rotational movement is determined, as well as the mechanical torque applied to the FSW tool. All these data are important for the design of the FSW equipment, in order to realize its main technical characteristics, depending on the base metals.Conclusions on the results are exposed, with important consequences for the industrial applications of the FSW process.

Abstract: Friction stir welding (FSW) is a solid-state metal fusion process that is characterized by several benefits over comparable processes such as a reduction in energy input and low part distortion. This process has been shown to hold great potential in the fusion of dissimilar metals, a technology highly sought after in the aerospace and automotive industries for its promising weight-reduction capabilities. Furthermore, electrically-assisted FSW (EAFSW) is the supplementation of the FSW process with an electrical current. This modification has been shown to improve many parameters; however, the current literature related to this subject is scarce. Herein, the fusion of Al 6061-T651 to mild steel is performed using EAFSW methods. A novel tool constructed a proprietary ceramic, XSYTIN-1, is also tested in this application. It was found that EAFSW improved material flow between the constituent materials; however, was unable to increase the joint strength of the weld. Additionally, it was found that the XSYTIN-1 tool did not exhibit any significant differences when compared to a conventional steel tool.

Abstract: Curved surfaces have been widely used in engineering applications such as friction stir welding (FSW), 5 axis CNC machining, and other processes. Therefore, the development of the finite element modelling of the complicated geometries has created a need to determine efficient tool paths. Previous finite element models modelled the single point movement of the tool. However, in industrial applications such as aerospace, mould and die, etc. the movement of the tool is complex. Proper determination of the tool path can lead to substantial savings of the process time, improvement of the workpiece surface quality and the improvement of the tool life, thereby leading to overall cost reduction and higher productivity. This paper presents a new approach for the determination of efficient tool paths in finite element modelling by using ABAQUS^® software. VDISP user defined subroutine is used in order to define the complex curved movement of the tool. The results indicate that the method is appropriate for modelling of the tool path, and the tool always has a perpendicular position to the surface. Therefore, the method can be suitable for increasing the application of the finite element modelling in various industries.

Abstract: During Friction Stir Welding (FSW) process materials to be joined will be subject of intense mechanical and thermal processes, characteristic to this solid state welding process. As a result, the welded materials will suffer quick heating and cooling cycles that will be overlapping on large plastic deformation/flow of the materials, which will produce their phase and structural transformation as well as modification of their properties. The paper investigates the structural transformation of the materials and will analyse the influence between the FSW process and these transformations.

Abstract: The paper presents the results of a mathematical model of the material flow during Friction Stir Welding (FSW) of aluminium alloys using a Finite Element Analysis. The authors presented their work on a two-dimensional visco-plastic model, using User Define Functions (UDF) in a commercial CFD code (FLUENT). The model developed was validated by microstructural investigations on experimental FSW joints and by a comparative analysis of temperature distribution field of the experimental FSW joint and numerical simulated model. The results confirmed that the mathematical model describes with a good precision the material flow and temperature field during FSW process.

Abstract: Coating of steel with aluminium alloy is needed for the execution of a functional layer for corrosion protection. Some experiments have been performed on square-section tubes (50 mm x 50 mm) of S235 steel, according to EN 10 025, to be coated with 1 mm thick sheets of EN AW 5754 aluminium alloy that have been previously bended as U shaped profiles. A new experimental model of specialized equipment has been used for certain experiments to make these functional layers of aluminium alloy on steel. Firstly, friction drilling and threading by form tapping, followed by screws-mounting without nuts have been used to make such joints. Several holes have been executed by a Ø4.3 friction drilling tool, then an M5 form tap was used for threading. For friction drilling, tools with 90% tungsten carbide content and 1 micron grain size were applied. By threading, TiN coated form taps have been used. Secondly, overlap friction stir welding (FSW) has been applied, to make a functional layer of aluminium alloy on a 50 mm x 50 mm S235 steel tube. The wings of the U profiles were overlapped. A quenched FSW tool, own-made of C 45 grade steel, EN 10083, has been used for these joining tests. The joining parameters are mentioned for each process. The run of each joining process is described and the joint test samples are presented. The appearance of the screw-mounted functional layers is appropriate. The metallographic analysis has revealed adequate form of the burr formed below the hole. The burr height is 2.5 – 3.2 mm. The pattern of the M5 thread is appropriate. No defects have been detected on the holes and threads. The appearance of the FSW functional layers is adequate. Metallographic analysis shows that FSW joints of the overlapped aluminium alloy sheets are adequate, because there is no gap between these sheets. There is only a narrow gap between the aluminium alloy bottom sheet and the wall of the steel tube, which proves an appropriate positioning of the two metals. No defects were detected, except for a weld flaw, as a small and isolated cavity, with a section less than 0.1 mm², considered within the acceptance limit, according to EN 25239-5. The U shaped sheets of aluminium alloy are firmly fixed on the square steel tube, for both coating types. The mentioned processes are proposed to increase productivity in industrial technologies for series production. The processes addressed in this paper are more rapid than conventional processes. Adequate preparation of the parts to be welded, mechanization and automation allow repeatability and quality. The target applications are coated structure elements for devices, appliances, tools, welded structures or automobiles. The involved industrial areas of the applications are: manufacturing, electro-technique, construction and automotive industries. The presented processes are ecological, because they do not need lubricants or other toxic substances and do not produce chips or harmfull substances.

Abstract: In the paper are presented some preliminary results regarding the possibilities of using of the friction stir welding process (FSW) and FSW assisted with TIG (FSW – TIG) welding for joining of the electrical components in the automotive industry. Couples of dissimilar materials approached in experiments were Aluminium EN AW 1200 and Copper Cu99, with thicknesses in conformity with real cases in the production process. The results obtained for butt welding an overlap welding of different thicknesses of materials (aluminium thickness s1 = 2mm and copper thickness s2 = 5mm) are presented. There are some general conclusions regarding the possibilities of joining the two materials under the specified conditions.

Abstract: The paper presents new techniques for joining of materials, proposed for development by ISIM Timisoara. It shows the general considerations and preliminary results regarding two new methods of joining by riveting, methods based on friction processes: - a joining process by riveting with hybrid effect, that means mechanical grip - friction stir welding - a joining process by friction riveting. Experiments for joining by riveting were carried out for couples of metallic materials (rivet and base materials) similar and dissimilar (aluminum alloys, steel, copper). There are presented conditions and requirements for the joining processes, how to form the riveted joint, positive results and limits of the application. Primary technical data on process principle, data on technological parameters, rivet configuration and influence factors were obtained.

Abstract: Friction Stir Welding, abbreviated FSW is an innovative joining process. The FSW is a solid-state welding process with a lot of advantages comparing to the traditional arc welding, such as the following: it uses a non-consumable tool, it results of good mechanical properties, it can use dissimilar materials and it have a low environmental impact. First of all, the FSW process was developed to join similar aluminum plates, and now, the technology was developed and the FSW process is used to weld large types of materials, similar or dissimilar. In this paper it is presented an experimental study and the results of it, which includes the welding of three dissimilar aluminum alloy, with different chemical and mechanical properties. This three materials are: AA2024, AA6061 and AA7075. The welding joints and the welding process were analyzed considering: process temperature, micro-hardness, macrostructure and microstructure.