SUBJECT: M.S. Thesis Presentation
BY: Jesse P. Castellana
TIME: Friday, April 23, 2021, 11:00am
TITLE: Modeling of Ceramic Machining
COMMITTEE: Dr. Shreyes Melkote, Chair (ME)
Dr. Steven Liang, (ME)
Dr. Christopher Saldana, (ME)
Powder ceramics parts are manufactured by combining a ceramic powder with a polymer binder into a slurry. The slurry is then plasticized and shaped through extrusion, casting, or pressing. After drying, the ceramic compact is now in the green state. The green ceramic is then sintered, making it harder and more brittle. Further shaping after sintering is often required, but methods for machining in the fired state have high costs and low efficiency. Additionally, fired machining is known to create subsurface damage that degrades the strength of the part, which requires more expensive post-processing to remove. An alternative is to machine the ceramic in the green state, when the ceramic is softer and can be machined at lower cost and with higher material removal rate. More work is needed to understand how process parameters and the material composition of the green ceramic impact the quality of the machined part and how green machining impacts strength reduction. Two sequential experiments are performed to characterize turning of green aluminum oxide. The first involves turning small sections of green alumina and measuring the resultant force and surface roughness. Factors including process parameters and aspects of the green alumina’s material composition are varied according to a fractional factorial design to understand how they impact force and roughness. The second experiment involves machining longer green alumina rods to be evaluated for bending strength in a four-point bend test. A subset of the factors in the first experiment are varied to produce rods of different force and roughness such that the effect of force and roughness on bending strength can be evaluated.