PSI - Issue 42

M. Yakovlev et al. / Procedia Structural Integrity 42 (2022) 1619–1625 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

1622

4

The crack was modelled as a mathematical notch. In order to accurately characterizing the influence of the strain gradient, a very refined mesh was used near the crack tip, where the elements' size is in the one micrometre order. Twenty-node quadrilateral brick isoparametric three-dimensional solid elements SOLID 186 were selected to obtain the 3D simulation model configurations (Fig. 2). An experimental axial tensile load of 54 kN was applied to the specimen. In this work, an elastic problem was solved.

Fig. 2. FE mesh of the specimen (a) and crack tip area (b).

In present study numerical calculations were performed for XH73M steel, which is widely used in aircraft engine design. The main mechanical properties of considered alloy at room temperature were determined according to the ASTM standard E8 and are listed in Table 2: E is the Young’s modulu s, σ 0 is the monotonic tensile yield strength, S is the ultimate tensile strength, a is the strain hardening coefficient, n is the strain hardening exponent.

Table 2. Main mechanical properties of XH73M. Material E, (GPa) σ 0 , (MPa)

S (MPa)

a

n

XH73M

180

780.66

1594

2.951

4.16

FE solution results ahead of the crack tip ( θ = 0º) were used for SIF calculation (Fig. 3). Shlyannikov (2013) generalized the numerical method to calculate the geometry-dependent SIF function Y , for the SIF calculation:

2 r   = , FEM i

K

(5)

1

FEM i  is stresses obtained from FEM analysis.

where r – crack tip distance,

Fig. 3. Crack front coordinate system

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