Papers by Keyword: Friction Stir Welding (FSW)

Abstract: In previous research conducted by the authors, a new vibration-damping steel sheet was developed using a new method employing friction stir forming (FSF) to create a laminated composite sheet in which steel sheets and superplastic alloys are laminated in layers. However, the details of the bonding mechanism have not yet been clarified. The present study investigates the relationship between the pressure during the process and the weld interface in the creation of the mentioned superplastic composite sheet. More specifically, a 0.5mm thick perforated steel plate is inserted between two Zn-22Al superplastic alloys and the FSF is applied to the top layer of Zn-22Al. The probe of the FSF tool passes directly above the perforated steel plate, the material stirred by the probe plastically flows into the hole and is joined to the underlying Zn-22Al interface by superplastic diffusion bonding (SPF/DB). It was revealed that the process parameters (rotational speed and tool feed rate) must be perfectly adequate to produce adequate heat input and pressure leading to a proper plastic flow of the material and the occurrence of superplasticity in Zn-22Al. In this study, as a first step to clarify the detailed joining mechanism, the amount of pressure applied to the specimen during the process is measured. While changing the process parameters, the pressure was measured at three points, under the probe of the friction stir process tool and, on the advancing, and retreating sides, to investigate the relationship between the parameters and the pressure at the joint interface.

Abstract: This paper is devoted to the numerical computation of a steady-state thermo-fluid modeling related to the Friction Stir Welding Process in a two-dimensional cylindrical geometry. It analyzes the efficiency of the implementation on parallel architectures of two finite-difference schemes on a structured grid. The first one applies the Newton-Raphson method to compute a numerical solution of this non-linear elliptic type equation, and uses an iterative sparse solver. The second one is based on a time-marching approach converging to the steady state solution thanks to a time-explicit computation. Their respective performance is presented and discussed. Some numerical simulation results are presented to validate the proposed approach.

Abstract: A technique for fabricating structural joints by closed-die-type friction-stir forming (FSF) is introduced in this study. The process is as follows. First, a steel sheet with a prepared hole is placed on an aluminum alloy plate. A die with a through-hole cavity is then placed above it to press down the steel sheet tightly. Next, a rotating stepped cylindrical tool is inserted into the through-hole cavity. To enclose the die cavity, the upper side of the tool is then positioned such that it is nearly in full contact with the inner surface of the through-hole. Finally, the top part of the tool is allowed to penetrate into the aluminum alloy plate through the prepared hole of the steel sheet to cause the material to extrude backward. Consequently, the material fills the whole of the space between the tool and die to generate a hollow-rivet-like aluminum alloy structure fastening the steel sheet to the aluminum alloy plate. This technique enables easier alignment between the die and the prepared hole of the steel as compared with the conventional joining technique which uses FSF. In addition, the new technique uses a one-sided approach (i.e., from the side of the harder material with a higher melting temperature) to join dissimilar materials, a process which is difficult for conventional methods of friction-stir welding and forming.

Abstract: Aluminium and titanium are currently in demand as lightweight materials. However, their combination is challenging due to their significantly different thermo-mechanical properties. Here, solid-state joining processes such as Friction Stir Welding open up new opportunities. Within this study, four commercial aluminium alloys (AA2024, AA5754, AA6056 and AA7050) were welded to Ti6Al4V. The results show a direct relationship between the solidus temperature of the aluminium alloys, the process temperature, energy input and resulting lap-shear strength. Regardless of the process parameters, AA5754 and AA6056 with higher solidus temperatures (600 °C and 555 °C) show superior bonding strength compared to AA2024 and AA7050, having a lower solidus temperature of 500 °C and 490 °C, respectively. Therefore, it is assumed that the maximum process temperature, proportional to the solidus temperature, has a major influence on the bonding. This, conversely, would imply that there is a physical limitation in the achievable joint strength between aluminium and titanium alloys as the required process temperature would exceed the solidus temperature of certain alloys. This assumption is verified for AA7050 by systematic variation of the rotation speed and therefore process temperature.

Abstract: This study utilized friction stir welding for butt joining of A1050 and C1020 plates, investigating the effects of cold rolling and annealing on the structure of the bonding interface and the hardness of the materials. The experiments revealed successful joint formation with minimized copper dispersion in aluminum and the formation of intermetallic compounds. Cold rolling resulted in increased hardness without significant crack propagation along the bonding interface. Annealing effectively reduced the difference in hardness, indicating that copper recrystallizes earlier than aluminum.

Abstract: In this paper, two numerical models of friction stir welding of two aluminum plates are considered. The coupled mechanical-temperature problem is solved with explicit integration over the time. The two models are based on the finite elements method (FEM) and have different complexity and number of participating parameters. The aim of the development is to highlight the weaknesses and strengths of the models of different complexity. The first model is simpler and it is based on the free penetration of the tool into the parts. The second model is based on the arbitrary Lagrange-Euler method and take in to the account the instrument penetration that allows to take into account the movement of the material in the process area. Convective and radiative heat transfers are accounted in the two models. The results for the temperature, stress and strain in the welded joint are studied and compared. The calculation time is given for each model. A parametric analysis was performed for the influence of the rotational speed of the pin, welding velocity and the pressing force. The influence of the temperature dependent physical properties of the welded plates is determined and compared for the both finite element models.

Abstract: An innovative method has been elaborated for the overlap friction stir welding (FSW) of 400 mm x 110 mm x 1 mm sheets of EN AW 5754 aluminium alloy, placed on a tilted jig.

Abstract: A welding test piece has been made by the overlap friction stir welding (FSW) of 400 mm x 110 mm x 1 mm sheets of EN AW 5754 aluminium alloy, placed on a tilted jig, of the multifunctional friction processing machine, type MMPF.

Abstract: During the last 15 years, the friction stir welding process (FSW) and the techniques developed based on the FSW principle have been a main research direction within ISIM Timisoara. The paper summarizes activities and results obtained by the FSW research team within the institute. The paper presents a synthesis that aims a briefly presentation of its own achievements and contributions from recent years regarding the development of the FSW process, especially on the following directions:- Friction stir welding on couples of similar and dissimilar materials;- Use of FSW-TIG (friction stir welding – tungsten inert gas assisted) and FSW-US hybrid processes friction stir welding - ultrasonic assisted);- Friction stir welding in protective gas environment;- Friction stir welding equipment and tools;- Systems for monitoring of the welding process. Results obtained at friction stir butt welding or by overlapping of some couples of materials that are difficult or impossible to be joined using conventional welding procedures, were presented. The results obtained during these years, as well as their scientific and technical level, have allowed the proposal for implementation of solutions that involve FSW welding for specific industrial applications (especially for the automotive field).

Abstract: Due to their properties (low density, high corrosion resistance, easy to process), magnesium alloys are used in all important industrial fields (aeronautics, automotive, transport, etc.). Magnesium is the lightest metal for complex metal structures with a density 2-3 times lower than that of aluminum and a quarter than that of steel. The possibility of joining magnesium with other materials allows a greater flexibility in designing and increasing the number of applications for light alloys.This paper presents results obtained by ISIM Timisoara for FSW welding of magnesium alloy AZ31B. Considering the difficulties that arise when welding magnesium alloys using classical processes, it can be assumed that by applying the FSW process for joining these types of materials, the results obtained are very good and can substantiate industrial applications.