Failure mechanisms of refill friction stir spot welded 7075-T6 aluminium alloy single-lap joints

Bucior, Magdalena; Wydrzyński, Dawid; Trzepieciński, Tomasz; Pytel, Maciej

doi:10.1007/s00170-017-1176-2

Cited by 39 publications

(39 citation statements)

References 32 publications

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“…The friction stir spot welding (FSSW) technique has been widely studied by many authors. Descriptions of the method, including the relations between the process parameters and joint strength, were provided by, for example, Cao et al [10], Chen [11] and Kubit et al [12]. Refill friction stir spot welding (RFSSW) is a modern modification of the FSSW technique which has been extensively investigated over recent years.…”

Section: Introductionmentioning

confidence: 99%

Polyoptimisation of the refill friction stir spot welding parameters applied in joining 7075-T6 Alclad aluminium alloy sheets used in aircraft components

Kluz

Kubit

Trzepieciński

et al. 2019

Int J Adv Manuf Technol

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In the aerospace industry, the refill friction stir spot welding (RFSSW) method is increasingly used to join thin sheets, especially those made of 2xxx and 7xxx series aluminium alloys. This paper presents the results of spot welding lap joints of 7075-T6 aluminium alloy sheets. The load capacity of joints was determined by tensile/shear tests using a universal testing machine. The effect of tool plunge depth, tool rotational speed and duration of welding on joint load capacity and failure mode was investigated. The polyoptimisation of the values of welding process parameters was carried out to ensure the highest load capacity of the joint at a minimum variance of the results obtained. The selection of the optimal parameters of the RFSSW process was carried out using an adequate mathematical model obtained on the basis of Weierstrass' theorem. It was found that tool rotational speed had the greatest impact on the load capacity of the joints. It was possible to increase the load capacity of the joint by increasing the duration of welding but only to a limited extent. The selection of optimal welding parameters requires a compromise solution, i.e. the selection of a tool rotational speed that ensured adequate plasticisation of the material with a welding duration that ensured that an appropriate joint microstructure was obtained and assured the required load capacity of the joint. The methodology of mathematical modelling of polyoptimisation presented can be useful in optimising similar joining processes.

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Section: Introductionmentioning

confidence: 99%

Polyoptimisation of the refill friction stir spot welding parameters applied in joining 7075-T6 Alclad aluminium alloy sheets used in aircraft components

Kluz

Kubit

Trzepieciński

et al. 2019

Int J Adv Manuf Technol

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“…The presence of the visible structural notch denotes too rapid a penetration of the sleeve into the base material, which causes partial blanking along the sleeve path instead of plastic deformation of the material. Kubit et al studied the effect of welding parameters on the load capacity of joints and analysed the defects in welded single‐lap joints obtained by the refill friction stir spot welding method. The experiments conducted indicate a great impact of tool plunge depth on the load capacity of the joint.…”

Section: Resultsmentioning

confidence: 99%

“…The welding of single‐lap fatigue specimens was conducted using an RPS100 spot welder by Harms & Wende GmbH & Co KG (Hamburg, Germany) at the Belgian Welding Institute (Zwijnaarde, Gent, Belgium). The RFSSW welding process can be briefly divided into four main stages, touchdown, plunging, refilling, and tool retraction, which were described in detail in recent papers by Kubit et al…”

Section: Methodsmentioning

confidence: 99%

“…The welding of single-lap fatigue specimens was conducted using an RPS100 spot welder by Harms & Wende GmbH & Co KG (Hamburg, Germany) at the Belgian Welding Institute (Zwijnaarde, Gent, Belgium). The RFSSW welding process can be briefly divided into four main stages, touchdown, plunging, refilling, and tool retraction, which were described in detail in recent papers by Kubit et al 12,13 RFSSW welding with incorrectly selected parameters can lead to the presence of many types of structural defect, such as structural notches, incomplete penetration, bonding ligaments, voids, and structural discontinuities. The welding parameters used in this study were selected based on previous investigations in order to ensure the creation of two types of sample: (1) without defects and (2) with accumulation of the typical defects of RFSSW welds, ie, voids in the weld corner, structural discontinuity along the circumference of the weld, and structural discontinuity in the weld bottom.…”

Section: Weldingmentioning

confidence: 99%

“…28 The quality of the weld is determined by several welding parameters, ie, plunge depth, rotational speed, plunge time, dwell time, and retraction time that can be varied over a wide range of values. The range of the welding parameters or their specific values provided by many authors 8,[10][11][12][13]17 can be linked only with a specific grade of material, coating type, and sheet thickness of the upper and lower sheets. Furthermore, the quality of the weld is very sensitive to the state of tool wear and coating used.…”

Section: Effect Of Welding Parameters On the Defectsmentioning

confidence: 99%

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Analysis of the effect of structural defects on the fatigue strength of RFSSW joints using C‐scan scanning acoustic microscopy and SEM

Kubit

Trzepieciński

Faes

et al. 2019

Fatigue Fract Eng Mat Struct

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Solid‐state refill friction stir spot welding (RFSSW) technology offers significant benefits in the fabrication of aluminium structures in the transport and aerospace industries. In this paper, the joining of 1.6‐mm‐thick Alclad 7075‐T6 aluminium alloy sheets is investigated. High‐cycle fatigue strength tests of single‐lap welded joints were carried out on an Instron E10000 testing machine with a limited number of cycles equal to 2 × 106. The welding of overlap fatigue specimens was conducted using an RPS100 spot welder by Harms & Wende GmbH & Co KG. C‐mode scanning acoustic microscopy (C‐SAM) and scanning electron microscopy (SEM) were utilised to evaluate the joint quality and characterise the microstructure. The paper discusses the effect of the maximum load force and defects (voids, hook, kissing bond, bonding ligament, etc) associated with the material flow in the weld on the failure mechanism. Insufficient plasticisation of sheet material and mixing of the material in the weld area are crucial defects that influence the number of destructive cycles. The weld defects in the joint structure are a source of a decrease in the fatigue life compared with the fatigue life of defect‐free welds. It was also found that RFSSW joint defects can be effectively detected by the nondestructive C‐SAM method.

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Effects of various tool plunge depths on microstructure evolution, mechanical properties and dome structure features of friction stir spot welded AA5052‐H32 similar joints

Bozkurt

Öztoprak

Sayer

et al. 2020

Materialwissenschaft Werkst

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The solid-state nature of friction stir spot welding process provides outstanding advantages for the sound joining of aluminum alloys. Within this study, 3 mm-thick AA5052-H32 sheets are successfully joined by friction stir spot welding using 2344 hot-worked steel pin to investigate the effects of various tool plunge depths on the microstructure, mechanical and metallurgical properties of similar welds. Therefore, the experiments are performed at different plunge depths in the range of 3 mm-4 mm. Accordingly, the relationships between the process parameter (tool plunge depth) and the responses (microstructure, dome structure, microhardness and lap shear tensile load) are established. Microstructure analyses demonstrate that the increase in the plunge depth leads to more grain refinement within the stir zone, which significantly affects the mechanical performance of the similar joints. This study also indicates that the tool plunge depth in friction stir spot welding process has a noteworthy influence on the characteristic features of the 5052 aluminum alloy joints, such as the dome structure. Moreover, an explicit increase in the microhardness towards the weld stir zone is observed in all specimens. It is found that the average maximum tensile-shear force enhances with the increment in the tool plunge depth from 3 mm to 4 mm.

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Failure mechanisms of refill friction stir spot welded 7075-T6 aluminium alloy single-lap joints

Cited by 39 publications

References 32 publications

Polyoptimisation of the refill friction stir spot welding parameters applied in joining 7075-T6 Alclad aluminium alloy sheets used in aircraft components

Polyoptimisation of the refill friction stir spot welding parameters applied in joining 7075-T6 Alclad aluminium alloy sheets used in aircraft components

Analysis of the effect of structural defects on the fatigue strength of RFSSW joints using C‐scan scanning acoustic microscopy and SEM

Effects of various tool plunge depths on microstructure evolution, mechanical properties and dome structure features of friction stir spot welded AA5052‐H32 similar joints

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