IUTAM Symp. on Generalized continua: Phase field and SGP for hydrogen embrittlement. Martinez-Paneda

Описание: Invited talk at the IUTAM Symposium "Generalized continua emerging from microstructures", held on July 19-23 (2021) in Paris.

Title: A phase field fracture and strain gradient plasticity-based model for predicting hydrogen embrittlement

Abstract:
We present a new theoretical and computational framework for predicting hydrogen assisted cracking in elastic-plastic solids. Non-local constitutive choices are adopted for both damage and plasticity [1]. The model combines, for the first time: (i) stress-assisted diffusion of solute species, (ii) higher order strain gradient plasticity [2], and (iii) a hydrogen-sensitive phase field fracture formulation [3], inspired by first principles calculations. The theoretical model is numerically implemented using a mixed finite element formulation and several 2D and 3D boundary value problems are addressed to gain physical insight and showcase model predictions. The results reveal the critical role of plastic strain gradients in rationalising decohesion-based arguments and capturing the transition to brittle fracture observed in hydrogen-rich environments. Large crack tip stresses are predicted, which in turn raise the hydrogen concentration and reduce the fracture energy. The computation of the steady state fracture toughness as a function of the cohesive strength shows that cleavage fracture can be predicted in otherwise ductile metals using sensible values for the material parameters and the hydrogen concentration. In addition, we compute crack growth resistance curves in a wide variety of scenarios and demonstrate that the model can appropriately capture the sensitivity to the plastic length scales, the fracture length scale, the loading rate and the hydrogen concentration. Finally, the modelling framework is coupled with in-line inspection measurements to predict structural failure from a given distribution of defects. The paradigmatic case of a pipeline subjected to pit corrosion damage is addressed, showcasing the capabilities of the model in delivering large-scale multiphysics predictions as a function of the environment, the material properties and the loading conditions.

References
[1] Kristensen, P.K., Niordson, C.F., Martínez-Pañeda, E. (2020). A phase field model for elastic-gradient-plastic solids undergoing hydrogen embrittlement. Journal of the Mechanics and Physics of Solids, 143:104093.
[2] Martínez-Pañeda, E., Deshpande, V.S., Niordson, C.F., Fleck, N.A. (2019). The role of plastic strain gradients in the crack growth resistance of metals. Journal of the Mechanics and Physics of Solids, 126:136-150.
[3] Martínez-Pañeda, E., Golahmar, A., Niordson, C.F. (2018). A phase field formulation for hydrogen assisted cracking. Computer Methods in Applied Mechanics and Engineering, 342:742-761.