Numerical implementation of a strain gradient plasticity model coupled with nonlocal damage

Date

2024-10-07

Author

Ünsal, İzzet Erkin

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This thesis presents the implementation of a lower-order strain gradient plasticity model to capture size-dependent plastic deformation and nonlocal damage effects. Two methods are employed to calculate the effective plastic strain gradient: the interpolation method, which uses plastic strain values at integration points, and the extrapolation method, which utilizes nodal values of plastic strain. The extrapolation method consistently predicts higher plastic strain gradients, leading to stronger material responses, particularly in cases involving sharp boundaries or material interfaces. However, both methods exhibit similar overall trends in simpler problems. The strain gradient framework is extended to include nonlocal damage effects through a volumetric averaging scheme. The interaction between hardening due to strain gradients and softening from damage is explored in several numerical simulations. Results indicate that increasing the damage length scale results in more diffused damage zones. In problems with sharp cracks, increasing the length scale associated with plasticity accelerated failure due to the intense strain gradients developing at the crack tip. Conversely, in problems with blunt cracks, the same length scale delayed failure by diffusing the localization of plastic deformation. Overall, the framework successfully captures the complex mechanisms governing material failure, depending on both geometry and loading conditions. The incorporation of strain gradient and nonlocal damage effects provides a versatile tool for modeling size-dependent behavior and damage evolution.

Subject Keywords

Strain gradient plasticity, Nonlocal damage, Size effect, CMSG theory

URI

https://hdl.handle.net/11511/111560

Collections

Graduate School of Natural and Applied Sciences, Thesis