In Our Schools
Missouri University of Science Wins Geodesic Dome Design Competition
by Dan Field, Ph.D. Student, Missouri University of Science & Technology
Competition at MS&T2017. The dome team title “Miner Domeination” was comprised of four Missouri University of Science and Technology students, Sean Duran (MetE 2017), Sierra Rasmusen (MetE 2017), Ransom Stamp (MetE 2017), and Dan Field (MetE 2013, MetE2018). The advisor to the team was Dr. David C. Van Aken. The Missouri S&T team used a 3D
A
printed plastic pattern, and based on Magma™ simulations the team added risers and appropriate gating to the dome with foam to ensure the soundness of the final cast part. Dr. Mingzhi Xu assisted in investment coating which was performed using silica binder and silica sand to obtain a strong coating to withstand the ferro-static pressures during casting. The steel utilized for the dome was a foundry grade 4320 steel with chemistry of 0.21C – 0.42Mn – 1.71Si – 1.55Ni – 0.91Cr – 0.21Mo – 0.13V – balFe (in wt. %). This alloy was used because it provided the best combination of toughness and strength,
6 ❘ December 2017 ®
n investment cast steel was utilized to create the dome for the ASM Geodesic Dome Design
and would not distort during heat treatment and quenching. The alloy was melted in a coreless in- duction furnace from InductoTherm using induction iron, ferrosilicon, ferromanga- nese, ferromolybdenum, ferrovanadium, low carbon ferrochromium, pure nickel, and carbon in the form of graphite. An ar- gon cover gas was used to shield the melt and calcium wire additions were made to modify oxide inclusions and remove sulfur. Alloys were tapped at 1620°C producing a 150ºC super heat. After so- lidification the composition was verified by optical emission spectroscopy. Gating and risers were removed in
the Missouri S&T machine shop with the assistance of Nathan Inskip and the casting was normalized at 950°C for 2 hours and air cooled. Austenitization was performed for one hour at 890°C which was based on 50°C above the calculated A3 temperature from FactSage 7.0TM thermodynamic calculations using the FSstel database. Tempering at 650°C for 2 hours followed by water quenching to room temperature was used to obtain the final properties; this was done to promote a gradual failure if
Figures above: (left) 3D printed plastic mold used for investment shelling. (right) the final cast dome being tested in the MTS frame during the competition.
yielding occurred i.e. ductile not brittle failure. The domes for the competition
were tested using an MTS compression frame with a capability of 50kN (11,000 lbf). The Missouri S&T, and Virginia Tech teams both exceeded the maximum load of the system. 11 teams competed from all over the U.S., including Arizona State, Colorado School of Mines, McMaster, Michigan Tech and various other universities. No yielding of the dome was observed in the Missouri S&T dome. After judging the Missouri S&T team was awarded 3rd place for the competition. This was the first time Missouri University of Science and Technology has entered this competition. 1st place was awarded to Virginia Tech, and 2nd place was awarded to Arizona State.
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