PSI - Issue 39

D. Fedotova et al. / Procedia Structural Integrity 39 (2022) 419–431 Author name / Structural Integrity Procedia 00 (2019) 000–000

423

5

Fig. 1. (a) CTS specimen and (b) loading conditions, (c) experimental crack paths for initial pure mode II fracture.

Table 2. Specimen sizes and loading conditions. Material Applied force F, kN

Applied force angle α, degree

Specimen thickness t, mm

Mode I

Mode II

Mode I

Mode II

Mode I

Mode II

Steel P2M Steel 34X

7.0 7.3

14.0 14.8 11.0 17.0

90 90 90 90

0 0 0 0

4.83 5.04 4.85

4.51 5.05 5.01 5.02

Al-alloy 7050

2.8-7.0 5.0-11.0

Ti-6Al-4V

5.0

To calculate the elastic and plastic SIFs under pure mode I and initial mode II with subsequent mixed mode numerical calculations were performed over a range of materials by employing the CTS specimen. In this study, the curvilinear crack trajectories obtained as a result of the experiment were considered for the classical state - plane strain. We modelled a CTS specimen (Fig. 1a) of in-plane dimensions 80 × 136 mm 2 and initial relative crack length a/w = 0.5. The initial crack tip was assigned a radius of curvature ρ = 60 nm. Typical finite element meshes for the experimental crack path and crack tip area in the CTS specimen are illustrated in Fig. 2a. With the aim of accurately characterizing the influence of the plastic strain gradients, a highly refined mesh was used near the crack tip, see Fig. 2b. A characteristic element size of h = 5 nm was used here. A typical mesh for the CTS specimen geometry has approximately 55 000 elements.

Fig. 2. (a) Finite element mesh for the crack-tip problem; (b) Near-tip mesh with the initial crack-tip radius.