Implementation of Stochastic discrete mechanical twinning module in the full-field crystal plasticity framework of DAMASK (the Düsseldorf Advanced Material Simulation Kit)

Figure 1: Nucleation and broadening of mechanical twinning in textured AZ31 Mg alloy during uniaxial compression.

Description: Deformation twinning is a frequently observed deformation mode in hexagonal structural materials that generally lack sufficient easily activated dislocation slip systems. How twins form is presently not fully understood, which results in a gap in our ability to confidently model and predict the contribution of mechanical twinning to the overall mechanical response of the material under investigation. To study the micromechanical consequences of the highly localized deformation caused by twinning within a full-field crystal elasto-viscoplastcity simulation the previously used descriptions that are spatially homogenized show only limited predictive capability. Instead of invoking a phase field-based description, it is suggested to reflect twinning by incorporating a deformation gradient jump ΔFp consistent with the rotation and shear caused by the (sudden) transformation of a material point into a deformation twin. This approach is compared to existing phase-field based descriptions and evaluated against a statistical dataset of twin propagation collected for commercially pure titanium. The model is used to investigate the influence of grain morphology and grain orientation relation on the formation and propagation of mechanical twins in presence of plastic deformation for hexagonal materials.
Strategy: Using already available phenomenological crystal plasticity module in DAMASK. Stochasticity will be introduced by adopting a Monte-Carlo type of approach. Supervisors already have good idea about the implementation and the project will be conduct under close supervision.
Timeline of the thesis
Task1: Basics of mechanical twinning in HCP materials: 1 to 2 weeks
Task2: Basics of crystal plasticity modeling: 2 to 3 weeks
Task3: Literature survey of existing mechanical twinning models: 2 to 3 weeks
Task4: Installation and exploration of DAMASK: 1 to 2 weeks
Task5: Implementation of the discrete twinning module in DAMASK: 4 to 6 weeks
Task6: Validation of the proper working of the model with test cases: 2 to 3 weeks
Task7: Documentation of code and thesis writing : 4 to 5 weeks

Virtual/ in-person meeting with one of the supervisor at least once in week.
Contact persons/supervisors: Satyapriya Gupta and Benedikt Weger

M.Tech. Dr.-Ing. B.Tech.
Satyapriya Gupta
Institut für Festigkeitslehre
Kopernikusgasse 24/I
8010 Graz
Tel. +43 316 873 - 7168

Dipl.-Ing. BSc
Benedikt Weger
Institut für Festigkeitslehre
Kopernikusgasse 24/I
8010 Graz
Tel. +43 316 873 - 7667