PSI - Issue 68

D. Tomerlin et al. / Procedia Structural Integrity 68 (2025) 1237–1244 D. Tomerlin et al./ Structural Integrity Procedia 00 (2025) 000–000

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2.3. Fracture toughness testing Fracture mechanics tests are carried out on the selected bar specimens that have undergone welding thermal cycles treatment on the Gleeble ® 3800 simulator. The bar specimens 10x10x110 mm and 10x10x130 mm with M10 threaded ends are prepared according to ASTM E1820 standard (2016), corresponding to Single Edge Notch Bend (SENB) test specimens. The crack starter notch is a narrow notch type manufactured using the Electrical Discharge Wire Cutting (EDWC) technology, with a wire diameter of 0.3 mm. The fatigue pre-cracking procedure, according to ASTM E1820 standard, simulates natural cracks, and provides quality fracture toughness test results. Testing machine MTS 647 (MTS Systems Corp., Eden Prairie, MN, USA) is used for the experimental investigation (Fig. 2). The ASTM E1820 fracture testing is used to determine the fracture toughness, applied load-CMOD curves, material fracture resistance in the form of J - R curves and CTOD( δ )- R curves. The results of the fracture toughness characteristic parameters are given in section 3.1.

Fig. 2. Fracture toughness testing of SENB specimen according to ASTM E1820 – test setup

2.4. Fatigue crack growth testing Fatigue crack growth tests are done on bar specimens previously heated on the Gleeble simulator. Specimens are prepared in accordance to ASTM E647 standard (2014), with the crack length measuring foil (gauge) placed on the surface for crack growth monitoring (Fig. 3). Pre-cracked SENB specimens are used, with crack growth monitoring using the RUMUL Fractomat (Russenberger Prüfmaschinen AG, Neuhausen, Switzerland). Fatigue crack growth testing determines the Paris-Erdogan law constants C and m , threshold Δ K th and crack growth rate da/dN .

Fig. 3. Fatigue crack growth testing of SENB specimen according to ASTM E647 – specimen