Advanced Metal Forming and Tribology Laboratory
DEPARTMENT OF MECHANICAL AND AEROSPACE ENGINEERING
One way to describe Dr. Gracious Ngaile’s lab in Engineering Building III on NC State’s Centennial Campus is “heavy metal.”
Ngaile, a professor in the Department of Mechanical and Aerospace Engineering, conducts research on design and manufacturing, tribology (the science of interacting surfaces in motion) in manufacturing, hybrid manufacturing processes, modeling and optimization of manufacturing processes, material characterization and finite element analysis.
He is also interested in the influence of ultrasonic vibration on microforming processes and in developing new formulations of metal-forming lubricants that are easier on the environment.
Ngaile teaches courses that give students a hands-on introduction to modern manufacturing processes and to a wide range of metal forming processes including state-of-the-art techniques. He also teaches applied finite element analysis and materials processing by deformation.
A native of Tanzania, Ngaile earned a B.S. degree in mechanical engineering from the University of Dar Es Salaam. He had to learn to speak and read Japanese in order to complete master’s and Ph.D. degrees at Japan’s Kumamoto University.
In tube hydroforming, water or hydraulic oil is forced into a metal tube at pressure of as much as 20,000 pounds per square inch, blowing even thick stainless steel up like a balloon. That tube is in a die (or more commonly a mold, as it is referred to in plastics manufacturing) and the end result is a sturdy metal tube formed into an unusual shape. The shaping process can be done in as little as 10 seconds, making tube hydroforming a quick, efficient way to form tubes of unusual shapes that are used in everything from automobiles and satellite antennas to bicycle frames and saxophones.
At this macro level, much of Ngaile’s lab research is looking at ways to hydroform tubes made of lighter metals, like aluminum, as automobile manufacturers work to improve their vehicles’ fuel economy. These lighter metals are usually less ductile (less formable) making it difficult to form complex shapes, so the lab is looking at solutions like wrinkling parts of the tube before hydroforming to strengthen areas that might otherwise burst during the process.
At the micro level, Ngaile and graduate student James Lowrie have developed a new technique to hydroform tubes as small as .3 millimeters in diameter for applications in electronics and medical devices.
Other researchers and manufacturers have tried to scale down the conventional macro-level process to hydroform at the micro level but have been unsuccessful because they could not achieve a sufficient seal at the ends of such a tiny tube.
Ngaile and Lowrie for the first time have created a novel solution that has made it possible to hydroform tubes at such a small size.
Instead of attempting a perfect seal of the ends of the tube, the researchers flooded an entire chamber including the tube and die with fluid and placed a plastic sheet around the die and applied pressure to the entire chamber.
Because of the plastic sheet, pressure was applied everywhere but the die cavity itself, meaning that as the tube is deforming the material will flow (form) into the die cavity, creating the desired shape.
“We went on an entirely different route,” Ngaile said.