Author Contributions
Conceptualization, T.N.-P. and J.H.; methodology, T.N.-P. and J.H.; validation, T.N.-P.; investigation, H.E. and J.H.; resources, K.D.; data curation, H.E. and J.H.; writing—original draft preparation, J.H.; writing—review and editing, T.N.-P..; visualization, J.H.; supervision, T.N.-P.; project administration, T.N.-P.; funding acquisition, T.N.-P. and K.D.
Funding
This IGF project IGF-Nr.: 18.985 N of the “Forschungsvereinigung Schweißen und verwandte Verfahren e. V. des DVS” was supported via AiF within the program for promoting the Industrial Collective Research (IGF) of the German Ministry of Economic Affairs and Energy (BMWi), based on a resolution of the German Parliament.
Acknowledgments
The authors thank OSK Kiefer, Oppurg, Germany, for the peening of samples. We acknowledge support by the Open Access Publication Funds of the Technische Universität Braunschweig.
Conflicts of Interest
The authors declare no conflict of interest.
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Figure 1.
Macrographs of DV-butt welds. (a) S355N, (b) S960QL, (c) Al-6082 T6.
Figure 2.
Fatigue test samples (DV-weld) shown in as-welded condition.
Figure 3.
Residual stress at surface of DV-butt welds made from S355N (a), S960QL (b), and Al-6082 (c). Hachures indicate the weld seam width.
Figure 4.
Residual stress in the surface layer obtained at the weld toes by means of hole drilling method. DV-butt welds made from S355N (a), S960QL (b), and Al-6082 (c).
Figure 5.
Residual stress relaxation in shot peened DV-butt welds. Use of steel shots at constant intensity. Variation of the coverage of 98% (top) and 25% (bottom). Cyclic loading at R = 0.1 with maximum stress of 360 MPa.
Figure 6.
Change of residual stress depth profiles in shot peened (steel shots, intensity 0.3–0.4mmA, coverage of 98%) DV-butt welds under cyclic loading. Cyclic loading at R = 0.1 with maximum stress of 360 MPa.
Figure 7.
Fatigue test data of clean blasted DV-butt welds made from S355N. “Clean blasted” are results from test series 1–3, 10, 11, 14–17. Samples peened by participants 1 to 3 were clean blasted in industrial facilities and fatigue tested in Braunschweig (round robin principle).
Figure 8.
Fatigue test data of clean blasted DV-butt welds made from S960QL. Shown here are test series 4–9.
Figure 9.
Fatigue test data of clean blasted DV-butt welds made from Al-6082. Shown here are test series 7–8, 12, 13 and 18–20 named as “clean blasted” without further distinction.
Table 1.
Base metals used for specimen preparation: mechanical and chemical parameters determined by tensile test respectively spectroscopy.
Material | Yield Limit | Tensile Strength | Elongation at Fracture | CEV | Thickness |
---|
S355N | 376 MPa | 518 MPa | 27% | 0.41 | 10 mm |
S960QL | 995 MPa | 1033 MPa | 16% | 0.56 | 10 mm |
Al-6082 T6 | 317 MPa | 340 MPa | 17% | - | 5 mm |
Table 2.
Peening media used.
Parameter | Steel Shots S280 | Glass Beads | Corundum NK 24 |
---|
Particle size | 600–1180 µm | 300–400 µm | 595–841 µm |
Shape | spherical | spherical | edged |
Density | 7.3–7.8 g/cm3 | 2.6 g/cm3 | 3.9 g/cm3 |
Hardness | 400–520 HV | 500–530 HV 1 | 8–9 1 (Mohs hardness) |
Table 3.
Almen strips used.
Almen Strip | N | A | C |
---|
Thickness | 0.79 ± 0.02 mm | 1.29 ± 0.02 mm | 2.39 ± 0.02 mm |
Table 4.
Overview about fatigue test series of peened DV-butt welds.
Test Series | Base Metal | Peening Media | Intensity | Coverage | Surface Roughness Rz |
---|
Reference | S355N | - (as welded) | - | - | |
Reference | S960QL | - (as welded) | - | - | |
Reference | Al-6082 | - (as welded) | - | - | |
1 | S355N | Steel shots | 0.3–0.4 mmA | 1 × 98% | 56.7 µm |
2 | S355N | Glass beads | 0.3–0.4 mmA | 1 × 98% | 38.4 µm |
3 | S355N | Corundum | 0.3–0.4 mmA | 1 × 98% | 71.9 µm |
4 | S960QL | Steel shots | 0.3–0.4 mmA | 1 × 98% | 25.8 µm |
5 | S960QL | Glass beads | 0.3–0.4 mmA | 1 × 98% | 30.1 µm |
6 | S960QL | Corundum | 0.3–0.4 mmA | 1 × 98% | 80.2 µm |
7 | Al-6082 | Steel shots | 0.3–0.4 mmA | 1 × 98% | 99.9 µm |
8 | Al-6082 | Glass beads | 0.3–0.4 mmA | 1 × 98% | 63.9 µm |
9 | Al-6082 | Corundum | 0.3–0.4 mmA | 1 × 98% | 107.5 µm |
10 | S355N | Steel shots | 0.3–0.4 mmN | 1 × 98% | 57.3 µm |
11 | S355N | Steel shots | 0.3–0.4 mmC | 1 × 98% | 61.3 µm |
12 | Al-6082 | Steel shots | 0.3–0.4 mmN | 1 × 98% | 83.3 µm |
13 | Al-6082 | Steel shots | 0.3–0.4 mmC | 1 × 98% | 96.5 µm |
14 | S355N | Steel shots | 0.3–0.4 mmA | 0.25 × 98% | 35.8 µm |
15 | S355N | Steel shots | 0.3–0.4 mmA | 0.50 × 98% | 37.1 µm |
16 | S355N | Steel shots | 0.3–0.4 mmA | 0.75 × 98% | 30.7 µm |
17 | S355N | Steel shots | 0.3–0.4 mmA | 2 × 98% | 63.8 µm |
18 | Al-6082 | Steel shots | 0.3–0.4 mmA | 0.50 × 98% | 91.9 µm |
19 | Al-6082 | Steel shots | 0.3–0.4 mmA | 0.75 × 98% | 88.2 µm |
20 | Al-6082 | Steel shots | 0.3–0.4 mmA | 2 × 98% | 96.5 µm |
Table 5.
Additional test series of industrially clean blasted specimen (round robin principle).
Test Series | Base Metal | Peening Media | Shape | Participant |
---|
21 | S355N | Steel shots | Edged | 1 |
22 | S355N | Cast steel shots | Edged | 2 |
23 | S355N | Cast steel shots | Edged | 3 |
Table 6.
Fatigue strength enhancement of the S-N curve in dependence of the base metal after shot peening.
Base Metal | Fatigue Strength Enhancement at N = 100,000 | at N = 2,000,000 |
---|
S355N | - | ≈ 156% |
S960QL | 125–140% | 180–200% |
Al-6082 | ≈ 110% | ≈ 162% |
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