SUBJECT: Ph.D. Dissertation Defense
BY: Sang-In Park
TIME: Wednesday, August 17, 2016, 10:00 a.m.
PLACE: MRDC Building, 4211
TITLE: Estimating Mechanical Properties of Cellular Material from Additive Manufacturing Process
COMMITTEE: Dr. David W. Rosen, Chair (ME)
Dr. Seung-Kyum Choi (ME)
Dr. Yan Wang (ME)
Dr. Massimo Ruzzene (AE)
Dr. Chad Duty (ME, University of Tennessee)


Cellular materials have been used for engineering applications due to their favorable mechanical characteristics. However, conventional subtractive manufacturing processes are not suitable for cellular materials because of their complex geometries. Recently, additive manufacturing (AM) processes have begun to offer new opportunities to produce cellular materials. AM’s layer stacking process allows users to fabricate complex geometries with no additional effort. Although the AM technique can be a good solution for manufacturing issues, the mechanical properties of additively fabricated cellular materials cannot be guaranteed due to the inherent limitations of the AM process. This research aims to develop a mechanical property-estimation procedure for additively manufactured cellular materials by considering the effects of AM processes. In order to clearly understand the AM process, related parameters are categorized into four groups: (a) Design and Manufacturing process parameters (DMP), (b) Layer deposition parameters (LDP), (c) Structural element parameters (SEP), and (d) Cellular material properties (CMP). Three transformations are defined among these groups. Firstly, the functional relationship between DMPs and LDPs is established based on process-modeling simulation. The variation in LDPs due to manufacturing instabilities is quantified in the form of a stochastic distribution. Next, an as-fabricated voxel modeling approach is developed for describing the propagation of geometrical degradation from LDPs to SEPs. The effective value of SEPs are determined based on semi-rigid joint frame element formulation. Finally, a discrete homogenization approach is implemented with the semi-rigid elements to integrate the effects of AM processes into the mechanical property estimation procedure. The estimation framework developed in this research can be applied to analyze the performance of additively manufactured cellular materials and help to design of cellular materials.