“Lately it occurs to me: What a long, strange trip it's been” are the most famous lyrics from the Grateful Dead’s most famous song “Truckin”, which was originally released in October, 1977. Now that the song is going through your head over and over and we are all showing our age, let’s talk about the trip.
The Gear Research Institute was originally incorporated in Illinois in October, 1982 although you can be sure the planning for this organization started well before that date. In case you did not do the math, this October is the GRI’s 30th anniversary, congratulations are well deserved. So, taking a brief trip back over the past 30 years, what have we seen:
- Challenger, Chernobyl and the
- OJ and Princess Diana
- Berlin Wall
- The new Millennium and Y2k meltdown
- 9/11 and the War on Terrorism
- Tsunami and Katrina
- iphone and ipad
- International Space Station
- Hybrid Cars and $4 gas
- The Internet
I hope you agree, what a strange trip it has been.
If we look at the original incorporation documents from 1982, and to refresh our memory, let see how well we focused over these past 30 years.
- To enlarge and enhance the existing body of engineering and scientific knowledge to the gear and power train related industries through applied research.
- To package and disseminate the knowledge of practicing industrial technologist, researchers and teachers for subsequent application thus providing the technical base for the industry to compete on a worldwide basis to benefit the U.S. economy and the general public.
So how did we do? Very well I must say and we even survived a move in 1996 to Penn State University with no loss of focus. The GRI has completed about 125 applied research programs and published 25 research papers on materials and tribology. In addition, the GRI has presented over 50 research results to audience of peers at both formal meetings and at research sponsored events. We have seen 25 students come and go over the years after gaining valuable experience in the gear laboratory, with many remaining in the gear industry to this day. So our founders got it right. We are all looking forward to many more successful years and we can be sure, what a strange trip it will be.
John (Jack) Masseth
Manager, Advanced Gear Manufacturing Technology
For a good part of the last several decades, double-vacuum melted (VIM-VAR) AISI 9310 was the steel of overwhelming choice for gears for rotary and fixed wing aircraft gear boxes. This “clean” steel provided the strength properties that enabled aircraft transmissions to be power dense and durable. However, this alloy also tempered at temperatures just over 300°F leaving very little room for operating under a “loss of lube” condition. In response to this need the steel industry responded with a variety of high hot hardness (H3) steels with higher tempering temperatures and in some cases, even higher “allowable” design stresses. Some organizations decided to utilize one or the other H3 steel, without the benefit of a comparative data on the gear related properties of these alloys. The Aerospace Bloc of the Gear Research Institute, however, decided to establish comparative performance data on these various steels in order to rationally identify which alloy offered the maximum potential for gear performance. This Bloc is sponsored by Avio, Boeing, General Electric, Honeywell, Latrobe Steel, Pratt & Whitney, Pratt & Whitney-Canada, REM Surface Engineering, Rolls Royce, Sikorsky Aircraft and Timken.
>Besides AISI 9310 VIM-VAR, the five additional alloys investigated were AMS 6308 (Pyrowear and Lesco 53), Pyrowear 675, CSS42L, Ferrum C61 and Ferrum C64. Two process variants, oil quenched and gas quenched were also considered. The gear related properties investigated were rotating/sliding contact fatigue, tooth bending fatigue,tooth impact resistance, oil-out performance and corrosion resistance. Also included in these evaluations are the impact of processes such as ISF and gas quenching. A meeting of the Steering Committee of this Bloc is scheduled where an “apples to apples” comparison of these alloys will be conducted in order to determine which of the alloy/alloys offers the maximum gear box performance.
In rotating/sliding fatigue tests cylindrical rollers are utilized to simulate the action of meshing gear teeth under load and the number of cycles, under a specific contact stress, to pitting failure or wear is obtained as a measure of the materials performance. Figure 1 shows the experimental rig utilized for this test. In tooth bending fatigue, a pair of gear teeth is subjected to cyclical loading till bending fatigue and tooth failure occurs. Figure 2 shows a tooth bending set up. Impact resistance is evaluated by dropping a measured weight on individual gear teeth and characterizing the force-displacement behavior of the tooth as it undergoes failure. Figure 3 shows a schematic of the experimental set up for impact testing. Oil-out performance is evaluated by running gears in a power re-circulating test rig (PC), under load and evaluating the behavior of the gear pair as lubricating oil is cut off to the mesh. Figure 4 shows a PC test rig on which this evaluation is conducted. A detailed description of the evaluation of corrosion resistance of gear steels was discussed in newsletter no. 9, 2012, earlier this year.
|Figure 3||Figure 4|
Education and Training
In order to assist the gear industry augment its aging work force, the Gear Research Institute has proposed two initiatives to train more gear knowledgeable engineers at the undergraduate and graduate levels. This involves incorporating engineering undergraduate students at the junior/senior level and graduate students in the Institute’s research efforts while being paid by a grant from the sponsoring industrial entity. Summer internships at the sponsor’s facility are also a part of the deal so that the student and the sponsor have an opportunity to assess each other with future employment in mind. We are glad to report that John Deere is the first organization to avail of this opportunity and is considering the resumes of several ME seniors to work at the laboratories of the Institute during the next academic year and future recruitment considerations. Besides funding the student John Deere is also contracting with the Institute to conduct a gear fatigue evaluation project that the selected student will work on at the Institute.
The Gear Research Institute is a non profit corporation. It has contracted with the Applied Research Laboratory of The Pennsylvania State University to conduct its activities, as a sponsor within the Drivetrain Technology Center. The Gear Research Institute is equipped with extensive research capabilities. These include rolling contact fatigue (RCF) testers for low- and high-temperature roller testing, power circulating (PC) gear testers for parallel axis gears with a 4-inch center distance (testers can be modified to accommodate other center distances), single tooth fatigue (STF) testers for spur and helical gears, gear tooth impact tester, and worm gear testers with 1.75 and 4-inch center distances. Extensive metallurgical characterization facilities are also available at Penn State in support of the Gear Research Institute. For further details on our testing capabilities please go to the Drivetrain Technology Center website or call Dr. Suren Rao, Managing Director, at (814) 865-3537.