RHEOLOGICAL CHARACTERIZATION DURING METALLURGICAL SOLID-LIQUID PHASE CHANGES IN RESISTANCE SPOT WELDING AND BINDER JET PRINTING
The dissertation offers a Multiphysics perspective in analyzing emerging metallurgical techniques. Heat transfer, structural deformation, and fluid flow associate with one another in phase-changing materials processing methods. To comprehensively analyze these aspects for an optimized final product, the authors have proposed a numerical mathematical model describing the thermal and geometric progression of the binary alloy casting process. The model is further executed in COMSOL Multiphysics, adapted in two metal manufacturing applications, resistance spot welding (RSW) and binder jet printing (BJP).
Resistance spot welding is a well-adapted metal sheeting joining technique with comparably limited modeling and simulating research. The heat transfer module and geometric deformation module are applied to the simulation of RSW to discuss the thermal gradient development of the welding zone. The model was further calculated and verified through a case study with Python.
BJP is a rapidly developing additive manufacturing method. The novel 3D printing technique brings challenges in post-processing geometric control and material selection limitations. Multiphysics simulation serves as an excellent tool in process parameters analysis and quality control. This dissertation focuses on the sintering process of BJP of binary alloy powders. Melting and solidification mathematical models were implemented in COMSOL, where the sintering shrinkage rate could be calculated. The shrinkage rate was further verified through experimental analysis of binder jet printed samples.
Microstructural analysis on sintered binder jet printed parts was performed to assess the validity of BJP to substitute the die casting method for manufacturing of valvebody. Sintering shrinkage and metallurgical analysis have been performed on the green and sintered BJP samples. After sintering, the final part achieved 98% density, and the integrity of the designed channels was preserved. The shrinkage analysis has indicated the effect of printing orientation and sintering orientation on the geometry and metallurgy of the final products. Microstructure analysis on the cross-sections of the sintered products also indicates the various defects induced from biner jet 3D printing.
The research aims to provide a systematic rheology analysis of the phase transformation process of binary alloys. The dissertation has connected the physical, mathematical modeling with 15
simulative modeling through the rheological evaluation of phase-changing manufacturing techniques. The connections were conclusively verified through empirical studies, including case assessment and experimentation. The research aims to offer universally applicable models that can be applied to phase-changing metal processing techniques.