Starting this month, TechFront has a new format that spotlights manufacturing research programs at key universities, followed by summaries of recent research in SME’s Journal of Manufacturing Systems, Journal of Manufacturing Processes and Manufacturing Letters, all published by Elsevier Ltd.
This month’s university focus is on the University of North Carolina Charlotte (UNCC). Manufacturing Engineering interviewed UNCC Professors Tony L. Schmitz and Chris Evans about the scope of UNCC’s undergraduate and graduate-level manufacturing education and research programs.
At UNCC, the emphasis is on students gaining practical shop-floor experience in undergraduate and graduate manufacturing. Located in the city of Charlotte, in the heart of NASCAR country, the urban university’s William States Lee College of Engineering includes the research of the Center for Precision Metrology, the Center for Freeform Optics, and the Siemens Large Manufacturing Solutions Laboratory in the Energy Production and Infrastructure Center (EPIC).
“The Center for Precision Metrology is the oldest research center here on campus,” said Chris Evans, professor of mechanical engineering and director of the Center for Precision Metrology (see https://cpm.uncc.edu/). “We support education, both graduate and undergraduate, but particularly graduate education where over a cycle of two years we have about 15 classes in aspects of metrology, manufacturing, and precision machine design. They’re all taught by faculty either in mechanical engineering or optical science engineering, because the centers are multidisciplinary.”
Featuring a state-of-the-art dimensional metrology lab, with equipment from suppliers including Hexagon Metrology, the Center for Precision Metrology supports faculty research in metrology and manufacturing. “I think we have the best metrology facility of any university in the US,” Evans stated. In addition to its cross-disciplinary approach, UNCC collaborates with industry, and has an industrial affiliates program includes companies such as Caterpillar, Cummins and Intel.
“The [affiliate] members come to campus to see presentations by students who are performing competitive, industrially driven research development programs selected by the affiliates themselves,” Evans added, “so basically the fees they pay to be a member fund the students. That’s an excellent outreach program, in terms of making our students visible to potential employers.”
Hands-on training is a key focus at UNCC. “I am proudly a ‘dirty-fingernails’ type of person,” Evans said. “Every one of our mechanical engineering undergraduates as a sophomore must take a manufacturing systems class that involves both their first design exposure and going into the shop.”
This experience shows UNCC undergraduates how to operate manual machine tools, and it requires them to build to a set of prints that are fully toleranced with GD&T for a single-cylinder air engine with no seal that must run for them to pass the course, Evans said. “They learn early in their career that they have to get their hands dirty and do real things, not just simulations,” he added. “They learn the meaning of tolerances.”
The 29,000-student UNCC campus has more than 1000 students in the mechanical engineering program, which is growing about 8% a year, Evans said.
At UNCC’s Siemens Energy Large Manufacturing Solutions Laboratory, headed by Professor John Ziegert, research is conducted on metrology gear purchased with a $2 million grant from Siemens Energy. Located in the EPIC unit, the lab’s centerpiece is a Leitz PMM-F 30-20-16 CMM that can accept large, heavy components with very complex geometry and quickly measure every dimension, angle and radius with accuracy within a few micrometers. The CMM was donated by Hexagon, an active partner in the Siemens lab, and is housed in a custom-designed environmental chamber that controls temperatures to 20 ±0.5°C. In addition, the lab has three laser trackers and access to an articulated arm CMM.
Providing practical experience, along with exposure to key industrial leaders, pays off for students attending UNCC’s manufacturing programs. “They generally have more than one offer, particularly our domestic students,” said Tony Schmitz, FSME, UNCC associate chair for graduate programs and professor of mechanical engineering and engineering science.
Other advantages lie in the university’s extensive collaboration with other manufacturing research institutions. The Center for Freeform Optics (https://centerfreeformoptics.org/) is a collaboration between UNCC and the University of Rochester. UNCC also works on an in-state collaboration advancing metal additive manufacturing science with NC State University (Raleigh), and another on powder metallurgy with UNC Greensboro.
“One thing I like about being in Charlotte is there’s collaboration in the air. We’re not internally competitive,” Evans said. That’s important, added Schmitz. “Many of the faculty of this department have been on the faculty at other universities and had other experiences, at national labs and so forth,” Schmitz said. “In all my experiences, this is the most collegial environment for a research organization that I’ve observed. I like to say, ‘We have grownups working here.’”
UNCC faculty researchers are involved in ongoing manufacturing research programs, including work at the Center for Freeform Optics on manufacturing processes for these optics based on single-crystal diamond tooling and ultraprecision machining. Another effort is headed by UNCC professor Gert Goch, an expert in gear manufacturing and gear manufacturing metrology, whose group recently developed a way of using areal description of gear teeth in metrology research.
At SOUTH-TEC 2017 in Greenville, SC, Schmitz gave attendees a futuristic look at manufacturing’s potential. He reprised his SME NAMRC-45 talk, based on his Blue Sky Competition award-winning research that focused on finding future manufacturing applications within biological processes found in nature. Schmitz’ talk, entitled “Biomimetic Manufacturing,” showed how biological systems can give cues for possible future manufacturing innovations. His work, winner of the inaugural NAMRI/SME Dornfeld Manufacturing Vision Award named after the late University of California, Berkeley, Professor David Dornfeld, presented a fascinating look into what future manufacturing researchers can come up with if they can “consider the outrageous” with open minds.
“We need to take new challenges and approaches,” Schmitz said of the SME Blue Sky Competition. “There’s a big risk/reward.” Schmitz’ explanation of biomimetic manufacturing outlined how looking closely at trees, bean sprouts, termites, beaver teeth, and even the Zika virus can give futurists clues to developing new manufacturing approaches.
In examining beaver teeth, for instance, Schmitz said the self-sharpening incisors would eventually grow too large for the beaver’s mouth if it stopped its constant chewing. Among Schmitz’s questions were: “Can we take advantage of the geometry? Could a cutting tool be designed that evolves to accommodate, rather than minimize wear? Instead of new coating material technology, could new designs ‘grow’ at an appropriate rate? … There are a lot of research possibilities in an intersection between manufacturing and biology.”
—Senior Editor Patrick Waurzyniak
These summaries, excerpts, and web links are from recent papers published in the SME Journal of Manufacturing Systems, Journal of Manufacturing Processes, and Manufacturing Letters, which are printed by Elsevier Ltd. (www.elsevier.com) and used here with permission.
In their article, “Joining sheet aluminum AA6061-T4 to cast magnesium AM60B by vaporizing foil actuator welding: Input energy, interface, and strength,” authors Bert Liu, Anupam Vivek and Glenn S. Daehn, of the Department of Materials Science and Engineering at Ohio State University (Columbus), examined techniques for successfully welding aluminum to cast magnesium to help automakers in their quest for ever-lighter automotive platforms that achieve greater fuel efficiency. The paper, which appears in the Journal of Manufacturing Processes, Vol. 30, December 2017, is available at http://www.sciencedirect.com/science/article/pii/S152661251730261X#!.
Dissimilar joining of sheet aluminum AA6061-T4 to cast magnesium AM60B was achieved by vaporizing foil actuator welding (VFAW). Three input energy levels were used (6, 8, and 10 kJ), and as a trend, higher input energies resulted in progressively higher flyer velocities, more pronounced interfacial wavy features, larger weld zones, higher peel strengths, and higher peel energies. In all cases, weld cross section revealed a soundly bonded interface characterized by well-developed wavy features and lack of voids and continuous layers of intermetallic compounds (IMCs). At 10 kJ input energy, flyer speed of 820 m/s, peel strength of 22.4 N/mm, and peel energy of 5.2 J were obtained.
In lap-shear, failure occurred in AA6061-T4 flyer at 97% of the base material’s peak tensile load. Peel samples failed along the weld interface, and the AM60B-side of the fracture surface showed thin, evenly-spaced lines of Al residuals which had been torn out of the base AA6061-T4 in a ductile fashion and transferred over to the AM60B side, indicating very strong AA6061-T4/AM60B bond in these areas. This work demonstrates VFAW’s capability in joining dissimilar lightweight metals such as Al/Mg.
In Volume 15 of Manufacturing Letters for January 2018, authors Xinchang Zhang, Wei Li and Frank Liou of the Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology (Rolla, MO), write about using modeling to help repair damaged turbine engine blades using direct metal deposition. Their paper, “Modeling of worn surface geometry for engine blade repair using Laser-aided Direct Metal Deposition process,” is available at http://www.sciencedirect.com/science/article/pii/S221384631730072X.
Engine blade repair requires obtaining the worn area and generating the corresponding toolpath for deposition. In this paper, an automated worn surface modeling method was proposed to regain the missing volume of damaged blades. Reverse engineering was utilized to reconstruct models of blades. The reconstructed damaged model was best-fitted with the nominal model. Cross-section area comparison method was used to detect the damaged layers. The ray casting method was adopted to intersect the damaged layers to extract the missing volume. The toolpath was generated and repair experiment performed using Laser-aided Direct Metal Deposition to validate the proposed method.
In “Analytical solutions for fixed-free beam dynamics in thin rib machining,” authors Tony L. Schmitz and Andrew Honeycutt of the UNC Charlotte Department of Mechanical Engineering and Engineering Science present two different analytical approaches for predicting thin-rib, fixed-free beam dynamics with varying geometries. This Journal of Manufacturing Processes, Volume 30, paper from December 2017 is available at http://www.sciencedirect.com/science/article/pii/S1526612517302554?via%3Dihub.
The first approach uses the Rayleigh method to determine the effective mass for the fundamental bending mode of the stepped thickness beams and Castigliano’s theorem to calculate the stiffness both at the beam’s free end and at the change in thickness. The second method uses receptance coupling substructure analysis (RCSA) to predict the beam receptances (or frequency response functions) at the same two locations by rigidly connecting receptances that describe the individual stepped beam sections, where the receptances are derived from the Timoshenko beam model.
Comparisons with finite element calculations are completed to verify the two techniques. It is observed that the RCSA predictions agree more closely with finite element results. Experiments are also performed where the stepped beam thickness is changed by multiple machining passes, and receptance measurements are carried out between passes. The RCSA predictions are compared to experimental results for natural frequency and stiffness. Agreement in natural frequency to within a few percent is reported.
In their paper, “Application of lean manufacturing principles to improve a conceptual plutonium 238 (Pu238) supply process,” authors Tomcy Thomas, Steven R. Sherman, and Rapinder S. Sawhney of the Department of Industrial and Systems Engineering, University of Tennessee (Knoxville) and the Radiochemical Science and Engineering Group, Nuclear Security and Isotope Technology Division, Oak Ridge National Laboratory (ORNL; Oak Ridge, TN), outline how lean processes can speed up the Pu238 supply process. The paper appears in the January 2018 Volume 46 of the Journal of Manufacturing Systems, and is available at https://www.sciencedirect.com/science/article/pii/S0278612517301413.
The US Department of Energy’s Pu-238 Supply Project aims to rebuild US capability to produce Pu238 at the kilogram scale. This radioisotope is used by NASA to power deep space probes, and supply is dwindling. It was last produced in the US in 1988. A conceptual design of a Pu238 supply process is described using existing processes and facilities at ORNL’s Radiochemical Engineering Development Center.
The rate-limiting section of the conceptual process was analyzed using discrete-event system simulation to determine expected production rates, bottlenecks, and the effects of time delays on the production rate. Process alternatives were generated based on lean manufacturing principles, and those were examined and compared to the original process using simulation to identify better operating strategies.
TechFront is edited by Senior Editor Patrick Waurzyniak.
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