PSI - Issue 57

Yevgen Gorash et al. / Procedia Structural Integrity 57 (2024) 611–617

612

2

Y. Gorash et al. / Structural Integrity Procedia 00 (2023) 000–000

6.0 3.0 0.8

8.0

25 blanks (12x12 cross-section)

DETAIL A

40.0 7.0 7.0 G

weld

2.1 gap

4.5

12.0

400.0 200.0 200.0 80.0 80.0

2.0

A

7.2

60°

160.0

c

R58.9

weld

d

3.0

12.0

25.0 offset

centre of the sample

25.0 offset

25.0

27.0

1.0

10.0

400.0

2.0 offset

1.0

12.0

a

10.0

b

41.0

39.0

6.0

160.0

M6x0.75

10.0

Fig. 1. Manufacturing and dimensions of USF samples from the welded plates: a) welded plate; b) blacks c) double-V butt weld; d) USF sample.

testing. However, there is almost no VHCF data ( > 10 8 ) for the welds made of low-carbon steel grades from EN 10025 and their equivalents with just a few publications, e.g. results for the bridge steel Q345 by He et al. (2012). So this research is focused on USF testing of two specific subgrades S275JR + AR and S355JR + AR with a goal of fatigue performance comparison. The fatigue welded samples are prepared with two surface conditions (polished and pre corroded) to investigate the extent of damage induced by the environmental e ff ect. The main purpose of this research is a fatigue performance comparison of the welds made of currently preferred steel S355JR + AR and the candidate steel S275JR + AR. Welded heavy machinery assemblies are designed to work for several years of guaranteed life at typically 15-20 Hz frequencies of loading under low stress amplitudes. In order to reach a few billion cycles within a practically sustainable testing time, an accelerated fatigue testing is required. The goal of reaching gigacycle fatigue domain is achieved using the ultrasonic fatigue testing approach with Shimadzu USF-2000A system. The USF samples for welds testing have a standard tapered shape geometry – exactly the same as used in testing of parent material in preceding work by Gorash et al. (2023). Preparation of these axi-symmetrical samples requires cutting of rectangular blanks (12x12mm in cross-section for S275JR + AR and 15x15mm in cross-section for S355JR + AR) and 160mm long using water-jet cutter, as shown in Fig. 1a. Blanks are cut out of the welded plates to have a HAZ in the middle as shown in Fig. 1b. The obtained blacks are turned into the axi-symmetrical samples as shown in Fig. 1d using HAAS TL-1 CNC Lathe. Two plates sized as 200 x 400 mm with a thickness of 12 mm or 15 mm were welded with a double-V butt joint using Metal Inert Gas (MIG) welding process to produce a 400x400 mm square plate, as shown in Fig. 1a. MIG is an arc welding process that uses a continuous solid wire electrode heated and fed into the weld pool from a welding gun. The two base materials are melted together forming a join. The gun feeds a shielding gas alongside the electrode helping protect the weld pool from airborne contaminants. The most important requirements to this particular welding are: 2. Manufacturing of welded specimens

• Butt weld preparation angle is 30 ◦ or corresponding groove angle is 60 ◦ (see Fig. 1c); • The root gap between the plates is 2 mm with root face length of 3 mm (see Fig. 1c); • 1.2 mm copper-coated MIG wire according to ER70S-6 AWS A5.18 standard; • Radiographic (X-ray) & ultrasonic (US) inspections of welds; • Mandatory post weld heat treatment (PWHT).