PSI - Issue 61

Bekir Kaçmaz et al. / Procedia Structural Integrity 61 (2024) 130–137 Author name / Structural Integrity Procedia 00 (2024) 000–000

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Fig. 3. FE results for the crack surface, left: LIGD Model, right: CIGD Model

In case of rectangular cross-section, at the early stages of loading, warping induced by torsion causes additional normal stress distribution which results in tension dominated mode-I failure. However, for the circular cross-section, at the early stages of loading, cross-section does not warp. Shear stresses induced by torsion and normal stresses due to bending grow simultaneously leading to a failure with a much stronger shear component. Since the employed equivalent strain definition is suitable for tension dominated failure modes, the resulting predictions are better for the rectangular cross-section case. A potential remedy could be the use of alternative equivalent strain definitions that are more sensitive to mode-mixity, e.g. see Shedbale et al. (2021). Although the crack geometry is complex, failure is governed by a single crack in the experiments of Brokenshire, Brokenshire (1996). Capturing multiple 3D cracks and their interaction / coalescence before the emergence of a major crack, could be a challenging case for the LIGD formulation. In principle, model parameters can be tuned so that the resulting response matches the experimentally measured fracture related quantities, e.g. fracture energy. However, direct inclusion of fracture energy within the formulation, probably as a controlling parameter in damage evolution, could be a valuable extension that can be pursued, see e.g., Arefi et al. (2018).

Acknowledgements

This work was supported by the scientific and technological research council of Turkey (TU¨ B˙ITAK, project num ber: 121M121), which is gratefully acknowledged.

References

Arefi, A., van der Meer, F., Forouzan, M., Silani, M., 2018. Formulation of a consistent pressure-dependent damage model with fracture energy as input. Composite Structures 201, 208–216. doi: https://doi.org/10.1016/j.compstruct.2018.06.005 . Bazant, Z., Belytschko, T., Chang, T., 1984. Continuum theory for strain-softening. Journal of Engineering Mechanics 110, 1666–1692. doi: 10. 1061/(asce)0733-9399(1984)110:12(1666) . Brokenshire, D., 1996. A study of torsion fracture tests. PhD Thesis, Cardi ff University, United Kingdom.