Speaker
Description
A thermodynamically rigorous model is proposed to simulate dislocation dynamics in crystalline materials subjected to rapid/gradual temperature changes. The proposed model, called the Thermal Field Dislocation Mechanics (T-FDM) model [1], is a strong coupling of the FDM approach [2] with the heat transfer problem based on the concept of thermal quasi-dislocations [3]. Its novelty lies in its unique ability to model: (i) dislocation generation, annihilation and motion subject to mechanical and thermal (heat-flux/temperature) boundary conditions, and (ii) local temperature changes induced by moving dislocations, whose densities may evolve due to self-induced temperature changes.
The T-FDM model is designed to study dislocation dynamics during any non-isothermal process, e.g. (i) solid-state thermal cycling (SSTC) or intrinsic heat treatment of a heat-affected alloy being fabricated via an Additive Manufacturing (AM) process, (ii) quenching of alloys during conventional processing or post-processing, (iii) cooling of welds, etc.
The governing laws of T-FDM find their roots in the principles of rational thermodynamics. The validity of a key principle: local thermodynamic equilibrium, under rapid temperature changes similar to those occurring due to SSTC during AM is discussed.
The T-FDM model can be upscaled to form a temperature-gradient dependent polycrystalline plasticity model. Furthermore, its design favours coupling with physics or chemistry-based models, e.g. a thermo-chemo-mechanical coupling can be performed to simulate dislocation interactions with evolving chemical species such as precipitates.
[1] M. V. Upadhyay, On the thermo-mechanical theory of field dislocations in transient heterogeneous temperature fields, JMPS 145 (2020) 104150.
[2] A. Acharya, A model of crystal plasticity based on the theory of continuously distributed dislocations, JMPS 49 (2001) 761 – 784.
[3] E. Kröner, Kontinuumstheorie der versetzungen und eigenspannungen, Ergebnisse der Angewandten Mathematik 5 (1958) 1 – 79.
| Speaker Country | France |
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