PSI - Issue 61

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Izzet Erkin Ünsal et al. / Procedia Structural Integrity 61 (2024) 164–170 I.E U¨ nsal and T. Yalc¸inkaya / Structural Integrity Procedia 00 (2024) 000–000

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Fig. 4. Shear band formation for di ff erent length scales l / ∆ h = 0 . 0 (left), l / ∆ h = 0 . 5 (middle), l / ∆ h = 1 . 0 (right).

Similar to the bending example, increasing the length scale parameter results in a less prominent shear band for mation. Using this methodology, it is possible to change the intensity of the shear bands by adjusting the length scale parameter for a small amount. Even small changes in the length scale, comparable to the size of the mesh, cause very prominent definition loss on the shear band formation. This e ff ect causes the material to lose its characteristic feature of shear bands.

4. Conclusions and Outlook

In summary, this study utilized a size-dependent gradient plasticity model to analyze various numerical examples to examine the evolution of strain patterning amorphous materials. To induce disorder and trigger shear band formation, two distinct approaches were employed. The first approach utilised a central imperfection to trigger the formation of two stable and perpendicular shear bands. For this method, the shear bands are heavily a ff ected by the length scale parameter. Increasing the length-scale parameter –corresponding to a smaller specimen– resulted in thicker shear bands which contradicts the observations in the literature. Then an alternative approach is followed in which the the shear band formation is triggered by locally assigning di ff erent fluctuating yield stresses to each finite element. For this approach, increasing the length scale corresponds to a stronger material response –which fits the observations in literature– and for smaller specimens, the shear bands become less evident. In conclusion, the second approach makes better predictions agrees better with the experimental findings and is more suitable for the modelling of amorphous media. Acharya, A., Beaudoin, A.J., 2000. Grain-size e ff ect in viscoplastic polycrystals at moderate strains. Journal of the Mechanics and Physics of Solids 48, 2213–2230. Aifantis, E.C., 1984. On the Microstructural Origin of Certain Inelastic Models. Journal of Engineering Materials and Technology 106, 326–330. Ashby, M.F., Greer, A.L., 2006. Metallic glasses as structural materials. Scripta Materialia 54, 321–326. Aydiner, I.U., Tatli, B., Yalc¸inkaya, T., 2024. Investigation of failure mechanisms in dual-phase steels through cohesive zone modeling and crystal plasticity frameworks. International Journal of Plasticity 174, 103898. Bharathula, A., Lee, S.W., Wright, W.J., Flores, K.M., 2010. Compression testing of metallic glass at small length scales: E ff ects on deformation mode and stability. Acta Materialia 58, 5789–5796. Burnley, P.C., 2013. The importance of stress percolation patterns in rocks and other polycrystalline materials. Nature Communications 4, 2117. Chen, D.Z., Jang, D., Guan, K.M., An, Q., Goddard, W.A., Greer, J.R., 2013. Nanometallic glasses: Size reduction brings ductility, surface state drives its extent. Nano Letters 13, 4462–4468. References