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On the Application of Laser Shock Peening as a Manufacturing and Repair Process to Improve the Fatigue Performance of Refill Friction Stir Spot-Welded AA2024-T3 Joints Cover

On the Application of Laser Shock Peening as a Manufacturing and Repair Process to Improve the Fatigue Performance of Refill Friction Stir Spot-Welded AA2024-T3 Joints

Fatigue of Aircraft Structures
Volume 2024 (2024): Issue 16 (December 2024)
By: Nikolai Kashaev,  Tim Mohr,  Sören Keller,  Uceu Fuad Hasan Suhuddin,  Benjamin Klusemann,  Falk Dorn and  Volker Ventzke  
Open Access
|Jul 2025

Figures & Tables

Figure 1.

a) Geometry of the welded overlap joint and b) schematic representation of the refill FSSW joint: BM – base material, SZ – stir zone, HAZ – heat-affected zone, TMAZ – thermomechanical-affected zone.
a) Geometry of the welded overlap joint and b) schematic representation of the refill FSSW joint: BM – base material, SZ – stir zone, HAZ – heat-affected zone, TMAZ – thermomechanical-affected zone.

Figure 2.

a) Schematic illustration of the application of the LSP treatment to the base material specimens and to the welded specimen with refill FSSW joint in the case of b) LSP treatment on one side and c) LSP treatment on both sides. The starting point of each LSP sequence was in the lower right-hand corner. The direction of the LSP sequence is parallel to the y-direction. The step-position of each LSP sequence is in the negative direction of the x-axis. All dimensions are in mm.
a) Schematic illustration of the application of the LSP treatment to the base material specimens and to the welded specimen with refill FSSW joint in the case of b) LSP treatment on one side and c) LSP treatment on both sides. The starting point of each LSP sequence was in the lower right-hand corner. The direction of the LSP sequence is parallel to the y-direction. The step-position of each LSP sequence is in the negative direction of the x-axis. All dimensions are in mm.

Figure 3.

a) Sketch of specimen with positions for three drilled holes used for the residual stress analysis, b) weld side of specimen in as-welded condition with position of drilled hole, c) back side of specimen in as-welded condition with position for drilled hole, d) weld side of specimen welded and LSP-treated with position for drilled hole, e) back side of specimen welded and LSP-treated with position for drilled hole. Depth-resolved residual stress profiles obtained for f) BM and LSP-treated AA2024 sheet and g) AA2024 lap-joint in as-welded as well as welded and LSP-treated condition.
a) Sketch of specimen with positions for three drilled holes used for the residual stress analysis, b) weld side of specimen in as-welded condition with position of drilled hole, c) back side of specimen in as-welded condition with position for drilled hole, d) weld side of specimen welded and LSP-treated with position for drilled hole, e) back side of specimen welded and LSP-treated with position for drilled hole. Depth-resolved residual stress profiles obtained for f) BM and LSP-treated AA2024 sheet and g) AA2024 lap-joint in as-welded as well as welded and LSP-treated condition.

Figure 4.

Fatigue test results for as-welded and welded and LSP-treated.
Fatigue test results for as-welded and welded and LSP-treated.

Figure 5.

Fatigue test results for pre-damaged specimens.
Fatigue test results for pre-damaged specimens.

Figure 6.

a) Schematic representation of the cross section of the overlap joint with the weld and positions 1 and 2 indicating the two crack origins in the cross section (marked with the red box). b) Cross-section of the as-welded specimen tested at 3.5 kN and subjected to 6.5 × 103 cycles with cracks starting at positions 1 and 2, and c) the magnification of the crack at position 1. d) Cross-section of the as-welded specimen tested at 3.5 kN and subjected to 1.4 × 104 cycles with cracks starting at positions 1 and 2, and e) the magnification of the crack at position 2 located near the interface between the upper and lower parts and f) the magnification of the position 2 near the outer surface of the lower part (crack tip). g) Cross section of the welded and LSP-treated specimen on both sides tested at 3.5 kN and subjected to 1.0 × 107 cycles with cracks starting at positions 1 and 2, and h) the magnification of the crack at position 2.
a) Schematic representation of the cross section of the overlap joint with the weld and positions 1 and 2 indicating the two crack origins in the cross section (marked with the red box). b) Cross-section of the as-welded specimen tested at 3.5 kN and subjected to 6.5 × 103 cycles with cracks starting at positions 1 and 2, and c) the magnification of the crack at position 1. d) Cross-section of the as-welded specimen tested at 3.5 kN and subjected to 1.4 × 104 cycles with cracks starting at positions 1 and 2, and e) the magnification of the crack at position 2 located near the interface between the upper and lower parts and f) the magnification of the position 2 near the outer surface of the lower part (crack tip). g) Cross section of the welded and LSP-treated specimen on both sides tested at 3.5 kN and subjected to 1.0 × 107 cycles with cracks starting at positions 1 and 2, and h) the magnification of the crack at position 2.

Figure 7.

Categorization of the mechanisms responsible for the failure of specimens in the fatigue test. a) Fatigue fracture failure “crack through the sheet” and b) fatigue fracture failure “shearing the weld”.
Categorization of the mechanisms responsible for the failure of specimens in the fatigue test. a) Fatigue fracture failure “crack through the sheet” and b) fatigue fracture failure “shearing the weld”.

Figure 8.

Fracture surfaces of a)-d) as-welded specimen tested at 1.5 kN and subjected to 1.41 × 106 loading cycles and e)-h) welded and LSP-treated specimen on both sides tested at 4.0 kN and subjected to 1.60 × 106 loading cycles.
Fracture surfaces of a)-d) as-welded specimen tested at 1.5 kN and subjected to 1.41 × 106 loading cycles and e)-h) welded and LSP-treated specimen on both sides tested at 4.0 kN and subjected to 1.60 × 106 loading cycles.
DOI: https://doi.org/10.2478/fas-2024-0003 | Journal eISSN: 2300-7591 | Journal ISSN: 2081-7738
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Language: English
Page range: 29 - 44
Published on: Jul 7, 2025
Published by: ŁUKASIEWICZ RESEARCH NETWORK – INSTITUTE OF AVIATION
In partnership with: Paradigm Publishing Services
Publication frequency: 1 issue per year
Keywords:
fatigue crack,
refill friction stir spot-welding,
laser shock peening,
residual stress,
fatigue life extension
Related subjects:
Engineering,
Introductions and overviews,
Engineering, other

© 2025 Nikolai Kashaev, Tim Mohr, Sören Keller, Uceu Fuad Hasan Suhuddin, Benjamin Klusemann, Falk Dorn, Volker Ventzke, published by ŁUKASIEWICZ RESEARCH NETWORK – INSTITUTE OF AVIATION
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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