Dr. GONG's Research
Dr. Haijun Gong, Associate Professor, completed his Ph.D. in Industrial Engineering in 2013 from University of Louisville. He has conducted research in additive manufacturing and 3D printing process development, property characterization of 3D printed metals, simulation and optimization of laser melting process, and physical phenomena in the selective laser melting and electron beam melting processes.
FDM-Based Metal 3D Printing
FDM is now the most popular 3D printing process (by number of machines) for printing thermoplastic materials, due to its economical machine expense and maintenance. However, direct material extrusion of molten metals is not realistic. Fortunately, this situation is changing by the introduction of metal-polymer filament into the 3D printing field. The filament has the same diameter of commonly used plastic filaments so that it fits for any open-source FDM based 3D printing platforms. It is firstly heated higher than glass transition temperature and then extruded from the nozzle to print a “green part”. After that, the green part is subjected to debinding process to remove the polymer contents to form a “brown part”, followed by a sintering process to achieve a dense metal part.
Lightweight Structure Design
Weight reduction is a key factor in the development of materials and components for use in many industries. Lightweight structures are widely used for this purpose. Lightweight structure design focuses on mesh generation from the original design of a CAD model. Then the skin body is generated to form a hollow structure. Lattice body is then created from the bracket mesh. The unit cell is customizable in terms of unit topology, unit size, beam thickness, and lattice angle. There are many topology patterns available for design studies, such as X, start, hexagon, octagon, etc.
Material Testing and Characterization
Metal based additive manufacturing (AM) processes used to fabricate metallic parts. These processes are of interest due to several advantages over conventional manufacturing methods. Freedom to fabricate intricate geometries, optimum material usage, elimination of expensive tooling etc. are some of the notable advantages of additive manufacturing processes. Because of their layered microstructure, the mechanical behavior of AM parts can be significantly different from conventionally manufactured parts. Further, AM parts can develop a variety of defects due to improper choice of process parameters or process disturbances. The AM metal testing and characterization is attracting more and more attention to academia and industry.