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Research Papers

Constant Heat Input Friction Stir Welding of Variable Thickness AZ31 Sheets Through In-Process Tool Rotation Control

[+] Author and Article Information
Gianluca Buffa

Department of Engineering,
University of Palermo,
Viale delle Scienze, Ed. 8,
90128 Palermo, Italy
e-mail: Gianluca.Buffa@unipa.it

Davide Campanella

Department of Engineering,
University of Palermo,
Viale delle Scienze, Ed. 8,
90128 Palermo, Italy
e-mail: Davide.Campanella@unipa.it

Archimede Forcellese

Department of Industrial Engineering and Mathematical Sciences,
Università Politecnica delle Marche,
Via Brecce Bianche 12,
60131 Ancona, Italy
e-mail: a.forcellese@univpm.it

Livan Fratini

Department of Engineering,
University of Palermo,
Viale delle Scienze, Ed. 8,
90128 Palermo, Italy
e-mail: Livan.Fratini@unipa.it

Michela Simoncini

Università degli Studi eCampus,
Via Isimbardi 10,
22060 Novedrate (CO), Italy
e-mails: michela.simoncini@uniecampus.it; m.simoncini@univpm.it

Antonio Barcellona

Department of Engineering,
University of Palermo,
Viale delle Scienze, Ed. 8,
90128 Palermo, Italy
e-mail: Antonio.Barcellona@unipa.it

1Corresponding author.

Manuscript received February 10, 2019; final manuscript received May 20, 2019; published online June 10, 2019. Assoc. Editor: Wayne Cai.

J. Manuf. Sci. Eng 141(8), 081002 (Jun 10, 2019) (9 pages) Paper No: MANU-19-1084; doi: 10.1115/1.4043838 History: Received February 10, 2019; Accepted May 21, 2019

Tailored blanks characterized by variable thickness were friction stir welded (FSWed) with the aim to obtain constant joint properties along the weld seam, regardless of the thickness change. To pursue this goal, the heat input was kept constant by in-process control of tool rotation. A dedicated numerical model of the process was used to determine the tool rotation values as a function of the sheet thickness. The mechanical properties and the microstructure of the FSWed joints, produced with varying process parameters, were studied. It was found that the proposed approach can produce joints with uniform properties along the weld line in terms of stress–strain curve shape, joint strength, elongation at failure, and microstructure.

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References

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Figures

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Fig. 1

(a) Mesh of the model at the beginning of the simulation and (b) sketch of Z-axis in relation to the pin tool and workpiece

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Fig. 2

Welded blanks with zones at different thicknesses along the welding line: (a) sheets with a hump zone and (b) sheets with a dip zone

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Fig. 3

Thermocouple location for the temperature measurement during FSW of AZ31 magnesium alloy

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Fig. 4

Comparison between numerical predictions and experimental measurements of temperature time history in the reference condition (thermocouples TC1 and TC2)

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Fig. 5

(a) Temperature distribution in the cross section of the reference case study and (b) temperature profiles along midthickness for the three case studies

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Fig. 6

Engineering stress versus engineering strain curves, ultimate tensile strength, and ultimate elongation obtained for conditions A, B, and RC

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Fig. 7

Temperature profiles along the midheight thickness for the joint welded under conditions A, B, and RC

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Fig. 8

Microstructure in the cross sections perpendicular to the welding line of the nugget zone: (a) condition B (top surface); (b) condition A (middle thickness), and (c) condition RC (middle thickness)

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Fig. 9

Engineering stress versus engineering strain curves, ultimate tensile strength, and ultimate elongation obtained for conditions C, D, and RC

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Fig. 10

Microhardness profiles in the midheight thickness in joint cross section in AZ31 obtained under the conditions C, D, and RC

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Fig. 11

Microstructure in the nugget zone along the weld centerline at different heights for the three case studies (conditions RC, C, and D)

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Fig. 12

Effective strain rate and Zener–Hollomon parameter distribution in the cross section of joints obtained under conditions C, D, and RC

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Fig. 13

(a) Grain size distribution in the cross section of the reference case study and (b) grain size profiles along midthickness of joints obtained under conditions C, D, and RC

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