High-fidelity modeling of metal additive manufacturing processes
Guest Speaker：Assistant Professor Lu Wang，City University of Hong Kong, China
Inviter: Ass.Prof. Lianghua Xiong
Date&Time: Thursday, 19th June, 10:00-11:00
Venue: Meeting Room 308, Xu Zuyao Building
Biography:
Prof. Lu Wang is currently an Assistant Professor in the Department of Mechanical Engineering at the City University of Hong Kong (CityU). Before joining CityU, he served as a research fellow at the National University of Singapore (NUS) from 2023 to 2024. He earned his Ph.D. from NUS in 2023 and completed his Master’s and Bachelor’s degrees at Huazhong University of Science and Technology (HUST) in 2016 and 2013, respectively. His research focuses on advanced manufacturing, with a particular emphasis on next-generation digital and smart manufacturing enabled by high-fidelity multi-scale, multi-physics modeling and advanced in-situ experiments. By integrating numerical simulations with advanced experimental observations, he investigates defect formation mechanisms, analyzes microstructure evolution, and optimizes structural performance during advanced manufacturing processes. He has published papers in prestigious academic journals, including Advanced Functional Materials, npj Computational Materials, International Journal of Machine Tools and Manufacture, Physical Review Applied, Additive Manufacturing, etc. Additionally, he serves as a reviewer for esteemed journals such as Nature Communications, Materials Today, International Journal of Machine Tools and Manufacture, npj Computational Materials, Additive Manufacturing, etc
Abstract:
The molten pool flow, particularly the keyhole fluctuation, plays a critical role in defect formation in additive manufacturing, which deteriorates the mechanical property, and is not fully understood. In this study, we derive an evaporation model for metal alloys considering the gas flow structure and material composition and implement it in a multi-physics thermal-fluid flow model, which utilizes the Volume of Fluid in the Finite Volume Method to capture free surfaces and the ray-tracing method to track multi-reflections of the laser within a keyhole. The simulation results indicate that our evaporation model is applicable for both common and near-vacuum environments. Furthermore, we simulate the keyhole pore formation process to reveal the mechanisms behind it, and the results are validated with the in-situ X-ray images. The simulation results present the instant bubble formation due to the keyhole instability and motion of the instant bubble when it pins on the solidification front. Moreover, a solute transport model with element evaporation effects is adopted to predict the element concentration distribution in the tracks and element concentration in the final part. Our solute transport model shows that the element evaporates from the keyhole surface due to the high keyhole surface temperature and is further mixed with high element concentration regions in the molten pool by liquid convection. Additionally, a Thermoelectric Magnetohydrodynamic (TEMDH) model is developed by incorporating the electrodynamic model with the Seebeck effect into the multi-physics thermal-fluid flow model. The laser scanning simulations on a bare plate under external magnetic fields indicate that the Lorentz force can smooth the fluid flow and further ameliorate the molten pool dynamics and dendrite morphology. With this high-fidelity multi-physics thermal-fluid flow model, the influence of metal evaporation and external magnetic fields on the molten pool dynamics are synthetically studied, which will give guidance to the metal additive manufacturing process.