Browsing by Subject "multi-phase field method"
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Item Non-Equilibrium Phase Field Model Using Thermodynamics Data Estimated by Machine Learning for Additive Manufacturing Solidification(University of Texas at Austin, 2018) Nomoto, Sukeharu; Segawa, Masahito; Wakameda, HiroshiA multi-phase field method using finite interface dissipation model proposed by Steinbach et al. is applied to simulate solidification microstructure evolution of stainless steel composition in the non-equilibrium condition of high cooling rate and temperature gradient of additive manufacturing. The calculation is performed for quinary system in order to simulate solidification of engineering composition. Thermodynamic calculation using CALPHAD database in this multi-phase field method calculation is replaced by machine learning prediction procedure to reduce calculation time. The microstructure evaluated by using machine learning parameter is good agreement with one directly coupled with CALPHAD database. This calculation is approximately five times faster than the direct CALPHAD calculation method. Finally, it is confirmed that this multi-phase field method can be applicable to simulate non-equilibrium phase transformation of additive manufacturing condition with high numerical stabilization.Item Numerical Simulation of Solidification in Additive Manufacturing of Ti Alloy by Multi-Phase Field Method(University of Texas at Austin, 2017) Shimono, Yusuke; Oba, Mototeru; Nomoto, Sukeharu; Koizumi, Yuichiro; Chiba, AkihikoThe multi-phase field method (MPFM) coupled with the database of calculation of phase diagrams (CALPHAD) is a powerful tool for simulation of solidification microstructure evolution in engineering casting conditions. MPFM equations have been introduced assuming quasi-equilibrium at the interface. However, few attempts have been made adopting MPFM for solidification in additive manufacturing (AM) conditions because the process is considered to be in a strongly non-equilibrium condition. In other words, the classical solidification theory based on the local equilibrium assumption was not considered to be applicable to this process. However, some researchers have reported experimental observations of the columnar-to-equiaxed transition in the solidification of AM. These suggest MPFM can be adopted for solidification simulation of the AM process. We tackled the issue of applicability of MPFM for solidification simulation in AM of Ti alloys. It was confirmed that solidification simulation using MPFM can provide observation of the columnar-to-equiaxed transition and establish a solidification map for the AM process conditions.Item Solidification Simulation of Direct Energy Deposition Process by Multi-Phase Field Method Coupled with Thermal Analysis(University of Texas at Austin, 2018) Shimono, Yusuke; Oba, Mototeru; Nomoto, SukeharuThe multi-phase field method coupled with the thermodynamics database of calculation of phase diagrams has been successfully applied to simulation of solidification microstructure evolutions in engineering casting processes. As multi-phase field method is based on the local (quasi-)equilibrium assumption in solidification theory [1], applying this method to solidification of additive manufacturing processes is not studied enough because of extremely large cooling rate and temperature gradient conditions. On the other hand, some researchers have reported experimental observations of the columnar-to-equiaxed transition in the solidification of the additive manufacturing processes including the direct energy deposition. They suggest that the local (quasi-)equilibrium assumption can be applied to solidification of additive manufacturing processes [2]. In this study, solidification microstructures of titanium alloys in direct energy deposition are calculated by multi-phase field method. Temperature distributions obtained by thermal analyses using finite element method are adapted to multi-phase field method. The microstructure evolution of columnar-to-equiaxed transition is confirmed. The results are summarized in a solidification map for direct energy deposition process conditions.