5 Werkstofftechnik
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Erscheinungsjahr
- 2018 (2) (entfernen)
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- Zeitschriftenartikel (2) (entfernen)
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- Englisch (2)
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Schlagworte
- Crack propagation (1)
- Diffusion (1)
- Environmentally assisted cracking (1)
- Fracture mechanics (1)
- Hot isostatic pressing (HIP) (1)
- Mass transport (1)
- Phase-field (1)
- Porosity (1)
- Single crystal superalloys (1)
- Vacancies (1)
Organisationseinheit der BAM
- 5.5 Materialmodellierung (2) (entfernen)
An improved diffusion model is proposed for pore annihilation during HIP of single-crystal nickel-base superalloys. The model assumes the pore dissolution by emission of vacancies and their sink to the low angle boundaries. Calculation, considering distribution of the pore sizes, predicts the kinetics of pore annihilation similar to the experimental one.
With the introduction of a mass transport mechanism the entire problem is subjected to a time frame that dictates the time-dependent action of soluted species on mechanical properties. A numerical framework within the phase-field approach is presented with an embrittlement-based coupling mechanism. The underlying functionals are expressed in terms of the displacement, mass concentration and crack phase-field. Within the phase-field approach the modelling of sharp crack discontinuities is replaced by a diffusive crack model facilitating crack initiation and complex crack topologies without the requirement of a predefined crack path. The isotropic hardening of the elasto-plastic deformation model and the local fracture criterion are affected by the species concentration. This allows for embrittlement and leads to an accelerated crack propagation. An extended mass transport equation for hydrogen embrittlement, accounting for mechanical stresses and deformations, is implemented. For stabilisation purposes a staggered scheme is applied to solve the system of partial differential equations by a multi-field finite-element method. A thermodynamically consistent coupling relation that accommodates the required mechanisms is presented.