PSI - Issue 81

V. Sidyachenko et al. / Procedia Structural Integrity 81 (2026) 123–128

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( ⁄ ) = −30,973 ( ) 2 +5,591 +0,8724 , ( ⁄ ) = 3.3319 ( ) 2 +0.66608 +0.23662 . 2.2. Numerical procedure To analyze the obtained experimental results, numerical simulations were performed for each of the investigated specimens (Fig. 3). The finite element mesh was constructed as a regular grid with refinement towards the crack front and the free surface along the specimen thickness. To ensure solution co nvergence, the crack was modeled with initial blunting radii of 35 μm and 5 μm. The choice of the initial crack tip radius (blunting) depends on the final load magnitude in the calculations. It is assu med that if the final radius is at least 2.5 times larger than the initial one, the solution is valid (Graba and Gałkiewicz , 2007; Tkach and Burdekin , 2012). Reducing the initial radius from 35 μm to 5 μm leads to an increase in the maximum crack opening stress, which also shifts closer to the crack tip (Fig. 4). However, the relative stress distribution patterns among different specimen types remain consistent. Therefore, further calculations were performed using an initial blunting radius of 35 μm. The problem was solved in an elastic – plastic formulation with isotropic von Mises hardening, accounting for geometric nonlinearity. (3)

a

b

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Fig. 3. Finite-element models of the specimens: (a) CT-1 standard compact tension specimen, a/W=0.5; (b) CRSEN specimen under biaxial bending, a/W=0.15; (c) SEN(B) specimen under three-point bending, a/W = 0.13.

Fig. 4. Distribution of normalized opening stress / ahead of the crack tip for SEN(B), CRSEN, and CT-1 specimens, comparing initial crack-tip blunting radii. 3. Results and discussions The temperature dependence of fracture toughness (Master Curve) for CT-1 specimens was constructed in accordance with ASTM E1921 – 17a. For comparison, the experimental fracture toughness data for CRSEN, SENB, and CRSEN old (Pokrovskyi et al. (2023)) were plotted on the Master Curve after being converted to CT-1 equivalent values using relation (4) of ASTM E1921 – 17a (Fig. 5).