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The Influence of Modification of the Front Surface Geometry of the RFSSW Tool Sleeve on the Plasticization Effect and Stirring Materials During Joining Sheets Made of Aluminum Alloy 2024

Łogin Waldemar, Śliwa Romana E., Ostrowski Robert

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 4

1435--1442

EN

The paper presents the results of research and analysis of the effect of joining by the RFSSW method of alclad sheets made of Al2024 with an anodic oxide coating, with the using the tool with modified geometry of the front surface of inner sleeve. The different effects of the modifications made on the phenomenon of plasticization and stirring of materials in the process of creating a weld, microstructure of welds and mechanical strength of lap joints were shown. The tests were carried out on 1.27 mm thick sheets, with the use of an unmodified tool and modified tools with three variants of the geometry. The welds and the joints samples were subjected to metallographic and strength tests. It has been shown that the use of a properly selected modified geometry has a beneficial effect on the transport of materials to be joined in the joint zone (flow pattern of plasticized layers and the stirring effect) during the welding, which translates into the strength of the joints and the nature of the weld failure.

2

Experimental and Numerical Stress State Assesment in Refill Friction Stir Spot Welding Joints

Gadalińska Elżbieta, Kubit Andrzej, Trzepieciński Tomasz, Moneta Grzegorz

Fatigue of Aircraft Structures

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2021

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Iss. 13

54--71

EN

Refill Friction Stir Spot Welding (RFSSW) is a technology used for joining solid materials that was developed in Germany in 2002 by GKSS-GmbH as a variant of the conventional friction stir spot welding (FSSW) [1]. In the RFSSW technology, the welding tool consists of a fixed outer part and rotating inner parts, which are called a pin and a sleeve. The tool for RFSSW is designed to plasticize the material of the parts to be joined by means of a rotary movement. The design of the tool allows independent vertical movement of both elements of the welding tool. This allows obtaining spot welds without creating holes that could weaken the structure. The main advantage of RFSSW is the potential for replacing the technologies that add weight to the structure or create discontinuities, such as joining with screws or rivets. Thus, RFSSW has great potential in the automotive, shipbuilding and aviation industries. Furthermore, the technology can be used to join different materials that could not be connected using other joining methods. The main objective of this work is to understand the physical and mechanical aspects of the RFSSW method - including the residual stress state inside the weld and around the joint. The results of the investigations can help to determine optimal parameters that could increase the strength and fatigue performance of the joint and to prove the significant advantage of RFSSW connections over other types of joints. The work assumes the correlation of two mutually complementary investigation methods: numerical analyses and experimental studies carried out with diffraction methods. The comparison between numerical and experimental results makes potentially possible the determination of degree of fatigue degradation of the material by observing the macroscopic stress state and the broadening of the diffraction peak width (FWHM), which is an indicator of the existence of micro-stress related to the dislocation density and grain size.

3

Analysis of the properties of RFSSW lap joints of Alclad 7075-T6 aluminum alloy sheets under static and dynamic loads

Kubit Andrzej, Faes Koen, Jurczak Wojciech, Bucior Magdalena, Kluz Rafał

Technologia i Automatyzacja Montażu

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2020

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nr 4

4--13

EN

This paper presents research regarding refill friction stir spot welding (RFSSW) of EN AW-7075-T6 Alclad aluminium alloy sheets, and the joint behaviour under static and dynamic loads. Single-point lap joint of sheets with different thicknesses, which corresponds to those used in aircraft fuselage structures, i.e. upper sheets with a thickness of 1.6 mm and lower sheets with a thickness of 0.8 mm, were analysed regarding the failure mechanism in static shear testing. It has been shown that a properly made joint is destroyed as a result of tension in the lower plate. The lower plate at the edge of the weld is structurally weakened by the HAZ, but also geometrically due to plastic deformation during the welding process, which has been demonstrated by metallographic investigations as well as by the FEM numerical model. Single-row RFSSW welded joints with different spacing of the welds and a riveted joint were impact tested. It has been shown that welded joints are characterized by a greater stiffness, which is higher when the spacing of the welds is smaller.

PL

Praca przedstawia badania połączenia zakładkowego RFSSW blach ze stopu aluminium EN AW-7075-T6 Alclad pod wpływem obciążeń statycznych oraz dynamicznych. Jednopunktowe połączenie zakładkowe blach o różnej grubości co odpowiada połączeniom stosowanym w konstrukcjach kadłubów lotniczych tj. górna blacha o grubości 1.6 mm oraz dolna blacha o grubości 0.8 mm, poddano analizie mechanizmu zniszczenia w próbie statycznego ścinania. Wykazano, że poprawnie wykonane połączenie ulega zniszczeniu na skutek rozciągania dolnej blachy. Dolna blacha przy krawędzi zgrzeiny jest osłabiona strukturalnie przez strefę wpływu ciepła, ale także geometrycznie poprzez deformację plastyczną powstałą podczas procesu zgrzewania, co wykazano na podstawie badań metalograficznych jak również przy użyciu modelu numerycznego MES. Jednorzędowe połączenia zakładkowe poddano badaniom udarności. Badano połączenia zgrzewane RFSSW o różnym rozstawie zgrzein oraz połączenie nitowane. Wykazano, że połączenia zgrzewane charakteryzują się większą sztywnością, która jest tym większa im mniejszy rozstaw zgrzein.

4

The Influence of Tool Geometry for Refill Friction Stir Spot Welding (RFSSW) on Weld Properties During Joining Thin Sheets of Aluminum Alloys

Łogin W., Śliwa R. E., Ostrowski R., Andres J.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 3

975--981

EN

The paper presents the results of research on the modification of the face geometry of the refill friction stir spot welding tool sleeve for welding thin aluminum sheets with an Alclad and an oxide anode coating. The analysis of the impact of such modification on the process perform (tool motion parameters, temperature) and microstructure as well as mechanical strength of the lap joints were analyzed. The tests were carried out using aluminum alloy 2024-T3 sheets with thickness 1.27 mm. For comparative purposes,joints were also made using plates without an Alclad and without anodized coating with using unmodified tool and modified toolswith developed 3 variants of face geometry. The samples with the joint were subjected to metallographic and strength tests. It has been shown that the use of modified geometry has a decisive influence on the performance of the process and the effect of softening and mixing of materials in the zone of point connection.

5

Experimental Research of the Weakening of the Fuselage Skin by RFSSW Single Row Joints

Kubit Andrzej, Bucior Magdalena, Kluz Rafał, Bochnowski Wojciech, Perłowski Ryszard

Advances in Science and Technology. Research Journal

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2019

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Vol. 13, no 3

90--97

EN

The paper presents the results of experimental investigations, the aim of which was to determine the degree of weakening of skin sheet of the thin-walled structure through a single-row welded joints made by Refill Friction Stir Spot Welding (RFSSW) technology. At the beginning, a short metallographic analysis of the weld was carried out, defining the characteristic areas of the microstructure. Then, comparative tests were carried out on the thin-walled structure sample in the form of a single-row skin-stringer joint. The structures made with the discussed technology of welding were compared with the traditionally joined structure by riveting. It has been shown that in the case of the welded structure, the skin sheet is weakened by more than 6% to a lesser extent than in the case of riveted. However, it was shown that the cracking path in the tensiled welded sheet runs along an unpredictable path, deviating from the line marked by the welds’ row. While in the case of riveted joint the cracking propagation along the row of rivets was revealed. The analyzes of fracture surfaces for both cases using scanning electron microscopy were also undertaken, thus undertaking preliminary considerations on the mechanism of fracture.

6

Wpływ zagłębienia narzędzia na jakość punktowych złączy zgrzewanych tarciowego z mieszaniem z zamknięciem krateru RFSSW wykonanych z blach ze stopów aluminium 2024-T3 I D16UTW

Lacki P., Derlatka A.

Rudy i Metale Nieżelazne Recykling

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2018

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R. 63, nr 4

10--16

PL

Jednym z parametrów punktowego zgrzewania tarciowego z mieszaniem z zamknięciem krateru RFSSW jest zagłębienie tulei narzędzia w łączone komponenty. Wartość zagłębienia zależy m.in. od grubości łączonych blach i tolerancji z jaką wykonano blachy oraz od pozostałych parametrów procesu RFSSW. Celem pracy było określenie wpływu zagłębienia narzędzia na jakość punktowych złączy RFSSW. Przedmiotem badań były złącza wykonane z blach ze stopu aluminium 2024-T3 o grubości 1,0 mm i stopu aluminium D16UTW o grubości 0,6 mm. Zgrzewanie następowało od strony blachy wykonanej ze stopu aluminium 2024-T3. Testowano trzy poziomy zagłębienia tulei, bez zmiany pozostałych parametrów zgrzewania. Zagłębienia wynosiły 1,10 mm, 1,15 mm i 1,20 mm. Dla każdego wariantu wykonano 10 zgrzein RFSSW. Osiem z nich służyło ocenie nośności złączy z uwzględnieniem analizy odkształceń zredukowanych, jedna z nich ocenie makrostrukturalnej, a jedna ocenie wizualnej.

EN

One of the parameters of Refill Friction Stir Spot Welding is a tool sleeve depth in the joined components. The value of the depth depends on inter alia joined sheets thicknesses, a tolerance with which the sheets were made and the other parameters of the RFSSW process. The aim of the work was to determine the impact of tool depth on the quality of the RFSSW joints. Joints made of an aluminum alloy 2024-T3 sheet having a thickness of 1.0 mm and an aluminum alloy D16UTW sheet having a thickness of 0.6 mm were analysed. The welding was performed on the side of the sheet made of aluminum alloy 2024-T3. Three tool depths without changing the other welding parameters were tested. The tool depths were following: 1.10 mm, 1.15 mm and 1.20 mm. For each variant 10 RFSSW welds were made. Eight of them were served to assess the load bearing capacity of the joints with consideration plastic strain analysis, one of them were for macrostructural assessment, and one of them were for a visual assessment.

7

Analysis of the mechanical properties and of micrographs of refill friction stir spot welded 7075-T6 aluminium sheets

Kubit A., Kluz R., Trzepieciński T., Wydrzyński D., Bochnowski W.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 1

235--244

EN

The main aim of the investigations was to determine the significance of parameters of RFSSW for the strength parameters of the resulting joint. RFSSW joints were made in 0.8-mm-thick 7075-T6 aluminium alloy using different welding parameters (tool rotational speed v, tool plunge depth, and joining time). The load capacity of joints was determined by shear tests. The optimum welding parameters which assure the highest load capacity (4.09 kN) in the tensile/shear test are: tool rotational speed of 3000 rpm, tool plunge depth of 1.55 mm, and joining time of 1.25 s. In the conditions of the static tensile test under pure shear the highest joint capacity (6.48 kN) is found for the joint welded at a tool plunge depth of 1.7 mm. Depending on the tool plunge depth, three types of joint damage were observed during tensile/shear tests: plug type fracture, shear fracture, and plug-shearracture. Incomplete refill is the main weld defect observed which is located on the path along which the sleeve plunges into the sheet. It was also found that alclad between the upper and lower sheets worsens the joint quality between the stir zone and thermo-mechanically affected zone.

8

Selection of basic position in Refill Friction Stir Spot Welding of 2024-T3 and D16UTW aluminum alloy sheets

Lacki P., Derlatka A., Gałaczyński T.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 1

443--449

EN

One of the important parameters of Refill Friction Stir Spot Welding is the so-called basic position of the tool. This is the arrangement of the pin and sleeve which occurs when the tool is plunged into the material. The basic positions can be divided into two categories. In the first category, the sleeve and the pin are above the sheet surface or below sheet surface and in the second category the pin is retracted within the sleeve or protrudes from it. The aim of the work was to test four settings of the basic position, and then determine the best setting of the basic position, without changing the other welding parameters. Joints made of an aluminum alloy 2024-T3 sheet having a thickness of 1.0 mm and an aluminum alloy D16UTW sheet having a thickness of 0.6 mm were analysed. The best setting of the basic position was determined based on assessment of the force carried in shear test, macrostructure and weld face of the joints.