PSI - Issue 75

Ralf Glienke et al. / Procedia Structural Integrity 75 (2025) 474–488

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Ralf Glienke et al. / Structural Integrity Procedia 00 (2019) 000 – 000

3.2. Manufacturing of test specimens The test specimens for the transverse loaded butt welds (series #01 to #06) were manufactured using the submerged arc welding process (SAW) according to a qualified welding procedure specification (WPS), fully penetrated welded and fulfilled the requirements of quality level B according to ISO 5817 (2023). The weld root was removed to eliminate crack initiation from internal welding defects. The welded plates were tested 100 % non-destructively (VT + UT + MT + PT) before the specimens (geometrical characteristics acc. to ISO/TR 14345 (2012)) were cut out by cold mechanical processing. Furthermore, the weld geometry (weld toe angle, excess weld metal, weld width) as well as the angular and linear misalignments of each test specimen were macroscopically measured in cross-section. A parameterised FE model with seam geometry was used to determine the stress concentration factor (SCF) for each test specimen. The SCF mean values are contained in Table 1 and thus show similar specimen characteristics across all series. Further information on specimen preparation, measurement and FEA can be found in Glienke et al. (2024a), Glienke et al. (2024b). The free edges were thermally cut (oxy-fuel or laser cutting) and met the requirements regarding maximum hardening (450HV10) according to EN 1090-2 (2024). The test specimens had a parallel web with a length of 30 mm, which was used to generate a reproducible cutting quality. The free edge was produced using machine-controlled cutting. The cutting parameters, the surface roughness on the entry and exit side and the size of the heat-affected zone can be found in Glienke et al. (2024d), Schröder et al. (2025). Notch-free hourglass specimens (K t ≈ 1.0) were used to determine the material fatigue strength at zero mean stress. These base material specimens were again left in the as-rolled condition (#11, #13, #15) or additionally blast-cleaned to achieve the surface preparation grade Sa 3 (#12, #14, #16). The flat bars with central hole (#17 to #20) were laser-cut from the same plate of structural steel S235JR as the base material specimens. The holes were drilled (#17, #18) or machined (#19, #20). Again, the as-rolled condition and the blast-cleaning treatment Sa 3 were investigated. The specimen geometry and the resulting SCF’s are listed in Table 1. Further information can be found in Glienke et al. (2024c). 3.3. Qualification of blast-cleaning process Currently, there are no European or international standards regarding the quality assurance of blast-cleaning procedures that are used for the purpose of fatigue strength improvement. For the fatigue strength increasing effect of the blast-cleaning process as a post-weld treatment method (comparative to Haagensen et al. (2013)), a flawless execution is essential. The impact is based on inducing compressive residual stresses and work hardening in the near surface area of the weld toe and the adjacent area. Blast-cleaning of the critical areas, corresponding to D = 100 % coverage is crucial (Gericke et al. (2018)). The specimen blast-cleaning was carried out by a corrosion protection company. A high-carbon steel-cast grit acc. ISO 11124 M/HCS/G050 (ISO 11124-3 (2018)) was used as abrasive in a circulation system with a pressure of ≈ 6 bar. The Almen test acc. SAE J 443 (2024) can be used to determine the intensity of the blast-cleaning process. The intensity depends on various parameters (e.g. material, velocity, distance, angle). The Almen test is done by blasting several test strips, mounted on a test strip holder, with different blasting times, see Fig. 3 a). Due to the induction of residual stresses from blasting, a deflection of the test strip occurs after removal from the holder. The plastic deformation or rather resulting arc height of the test strip was measured with an Almen gauge. Almen test strips Type A, Grade 2 were used. Strips and specimens were blast-cleaned at the same distance of ≈ 500 mm, an angle of ≈ 75° (see Fig. 3 b) and resulted in an intensity of 644.4 µm A (see Fig. 3 c).

Fig. 3. a) Schematic illustration of Almen intensity test SAE J 443 (2024), b) process of Almen test in blast-cleaning booth, c) results of saturation curve with Almen intensity for chosen parameters, coverage determination d) indirect method with fluorescent marker and UV-light, e) direct method with 30x magnification of surface