Contact: Phil Hearn
You don't have to be an engineer to know about fatigue and cracking under stress, but in the case of James C. Newman Jr., it helps.
When it comes to aircraft, you might say the Mississippi State scientist is a crackerjack university researcher on the subject of cracks. He has spent most of his adult life trying to improve the structural safety of just about everything that flies.
A Memphis, Tenn., native, with a doctorate in engineering mechanics from Virginia Tech University, he spent nearly 40 years as a senior scientist at NASA's Langley Research Center in Hampton, Va., before "coming back home" to the Mid-South in 2001. That was the year he joined MSU's aerospace engineering department.
"I spent my last 10 years at Langley working on the National Aging Aircraft Research Program," said Newman, who specializes in fracture mechanics and fatigue stress analyses. "It was probably the most exciting time of my life and career. We developed methodologies, concepts and computer codes to help the airline industry predict when this phenomenon called widespread fatigue damage would occur in aircraft."
The Boeing Co. started an aging aircraft program in 1983 to give special attention to planes that have exceeded their operational design life--usually after about 20 years. The Federal Aviation Administration initiated its own national program after nearly a third of the roof of an Aloha Airlines Boeing 737 blew off as the plane cruised above Kahului, Hawaii, in 1988. Congress also authorized NASA to conduct an independent aging aircraft program in collaboration with the FAA and the aircraft industry.
One Aloha flight attendant was sucked out of the plane when it suffered an explosive decompression, but the 737 managed to land safely without further fatalities. The accident was blamed on pre-existing fatigue cracks in the fuselage caused by frequent takeoffs and landings over a long period of years.
"You've got an aging fleet and that's a problem, but maintenance and inspection programs have greatly increased," said Newman. "The methods we develop to predict crack growth have direct application to the aircraft industry."
Since landing at MSU--where his son, James III, also is a member of the aerospace engineering faculty--Newman has been busy trying to help the university carve a special niche in the field of fatigue and fracture research. Steven Daniewicz and Judith Schneider, two colleagues in the mechanical engineering department, also play important roles in the campus effort, as do three graduate-student laboratory assistants.
MSU and about 25 other universities across the nation are members of the Aircraft Airworthiness Centers of Excellence program. Last year, Newman, whose mission for AACE involves the development of databases for use in the aircraft propeller and rotorcraft industries, received two grants totaling $275,000. Of the amount, $105,000 was provided by the FAA; $170,000 by the Office of Naval Research.
Because the FAA money required an equal match by the institution, Newman sought the assistance of MSU's Office of Research, Bagley College of Engineering, and the aerospace and mechanical engineering departments. With their help, he purchased two of the latest hydraulic testing systems developed by the Instron Corp. of Canton, Mass.
Engineering dean Wayne Bennett said university support in situations like this is essential because it "provides our engineering students with an exposure to various mechanical testing methods to complement their academic knowledge."
Controlled by monitoring equipment purchased in May from Pennsylvania-based Fracture Technology Associates, the Instron machines enable the scientists to conduct material fatigue-crack-growth tests 24 hours a day, seven days a week.
"Once a graduate student gets a test started and running, the system runs on its own," said Newman. "The Instron machines actually load the specimens, but the electronic hardware and software of the FTA system controls the machines."
Although Newman's research is applicable to all structural materials used in the manufacture of fixed-wing aircraft and helicopters, his current effort focuses on the strength and durability of propellers and rotor blades.
"Propellers are subjected to millions of cycles every couple of months," he said. "It's a high-cycle fatigue situation, so the threshold regime for crack growth is very important to the FAA. They want to have the propellers below this threshold so cracks won't develop and grow."
Newman said propeller blades normally are used for five years, then scrapped. "If a crack does develop, it will go to failure within a few months," he explained. "You want to design these blades so they will last twice their normal five-year life span."
NASA's aging aircraft research, in which Newman participated, had achieved most of its objectives by 1998. He said one outcome of the Langley project is a current ability to predict, "within a 5 percent" error factor, the critical pressure load at which a fuselage will experience a cracking pattern similar to the Aloha Airlines fuselage failure. From this, government regulators developed a "fracture criterion" now used by the aircraft industry, he added.
The FAA/NASA program closely examined a variety of structural aspects that may come into play during flight, including rivets and stress concentrations, corrosion caused by water accumulation and residual stress in metals. Since 1991, the National Transportation Safety Board also has pressed for more stringent examination of aircraft operating systems.
That was the year NTSB investigators determined that a "malfunction of the left engine propeller control unit" caused a commuter plane crash that killed U.S. Sen. John Tower of Texas and 22 others.
Newman said 80 percent of all aircraft accidents are caused by weather and human error, with only 3 percent attributed to structural failure.
"We're trying to improve the safety record of both commercial and commuter aircraft systems," he added. "That 3 percent is not very big, unless you happen to be on that aircraft."
NEWS EDITORS/DIRECTORS: For additional information, contact Dr. Newman at j.c.newman.jr@ae.msstate.edu or (662) 325-325-1521.