Vol. 20, 2017
It's been a wonderful thirty years of my association and time with GRI, first as a Board of Trustees member, then GRI’s President and then back as a Board member, but it is time to move on. I came to know GRI during the years that the organization was transitioning from its mid- western location and "one man band", to Penn State, where it would become a globally recognized source for Gear Research. It was during this early time that AGMA became more involved in the GRI as they saw the direct benefit to the Gear Industry. And benefit it did!, under the very able leadership of Dr. Suren Rao, and many talented future Gear Engineers who would pass thru the GRI labs during their Undergraduate and Graduate degree studies.
So many wonderful and talented "Gear" people who have built GRI and established GRI as an important cog in the Industry as we know today. The technical article described here on evaluating ultra-clean gear steels for the aerospace industry is just one example of GRI’s significance to the industry.
On reflection, it never ceases to amaze me how giving time and talent always seems to give us so much more then we feel have given. I have met such wonderful and talented people from so many different areas of our industry. Not to mention opportunities to visit so many great factories, large and small, is and has been an incredible education in itself. I have been privileged and honored to have been able to add my small measure to what has become such a great resource to our Gear Industry.
Sam R. Haines
It is known that vacuum re-melting of steels, such as AISI 9310, AMS 6308, M-50, 4340, etc., improves their fatigue and endurance properties. In general vacuum melting reduces the gas content in the steel and in turn reduces the gas available to form inclusions. The absence of inclusions induces the avoidance of inclusion related failures in the material enhancing the material’s fatigue properties. Significant data and experience showing the improvement of fatigue properties of double vacuum melted steel (VIM-VAR) over single melted steel (VAR) already exists. Performance data on triple-melt Nickel alloys for gas turbine applications also demonstrates an increase in fatigue life and endurance. The question that needs to be answered is whether triple-melt steels would show improved gear related fatigue performance on a “cost justified” basis. The Gear Research Institute is stepping up to answer this question.
In a project sponsored by the Aerospace Bloc (sponsors: GE Avio, Bell Helicopter, Boeing, CarTech, GE, Honeywell, Lockheed-Martin, Pratt & Whitney-Canada, Pratt & Whitney-East Hartford, REM Surface Engineering, Rolls Royce, Sikorsky and UTC Space Systems), triple-melt AMS 6308 (VIM-VAR-VAR) and (VIM-ESR-VAR) alloys will be evaluated for axial fatigue properties. Baseline tests will also be conducted on AMS 6308 double-melt (VIM-VAR) steel. The axial fatigue tests will be conducted as per ASTM E466-15. This test was chosen as it is the simplest test to perform and further gear related fatigue tests are planned if data obtained in this initial effort is encouraging.
The various steels are manufactured by Carpenter Technologies (CarTech) specifically for this project. Very careful material processing details were defined by CarTech and accepted by the Steering Committee of the Aerospace Bloc. These details spelled out the post-processing after ingot casting and the inspection and evaluation procedures that the triple-melt and the double-melt steels for this project would undergo. They included metallurgical testing and standard release testing as per CarTech’s procedures. This test and evaluation data on these materials was also presented to the Steering Committee at one of the subsequent review meetings.
A significant amount of planning has also be expended in the location of the test specimen blanks relative to the ingot. Specimens are to be fabricated in both the longitudinal and transverse direction relative to the ingot. The key is to obtain specimens that characterize the entire ingot and not just one particular location or direction. Illustrated below in figure 1 are the location of the longitudinal and transverse test specimen blanks in the ingot for the axial fatigue and tensile tests planned in this effort. These specimen blanks will be wire electro-discharge-machined (EDM) from the ingots.
Figure 1: Location of longitudinal and transverse test specimens in the ingot
The axial fatigue tests and the tensile tests will be conducted on one of GRI’s universal hydraulic test machines illustrated in figure 2. Grips and other accessories required for the testing are available. While fully reversible fatigue tests were initially considered, this was abandoned due to the likelihood of damage to the fractured surfaces and tests with an R-value of 0.1 was considered as appropriate.
At the time of compiling this newsletter (October 2017) the AMS 6308 VIM-VAR, the VIM-VAR-VAR and the VIM-ESR-VAR steels had been received by GRI and test specimen blank fabrication was complete. Heat treat specifications for the test specimens had been finalized and was in process. Testing is planned after the specimens are received and test data demonstrating the fatigue benefits of triple-melt steels vs. double-melt steels will be available in late 2017 or early 2018.
Figure 2: Universal test machine with axial fatigue sample under test
Education and Training
In order to assist with replenishment of the gear industry’s aging work force, the Gear Research Institute has developed a hands on education for students at both the undergraduate and graduate levels. The results of the program are entry level engineers that have been trained in the basics of gearing. This involves incorporating engineering undergraduate students, at the junior/senior level and graduate students in the Institute’s research laboratory while being paid by a grant from the sponsoring industrial entity. Summer internships have also been arranged at the sponsor’s facility, so that the student and the sponsor have an opportunity to assess each other with future employment in mind.
Typically, students get hands on experience by setting up and monitoring gear test equipment with additional training topics such as gear metrology, failure analysis, metallurgical characterization, vibration monitoring for failure detection, statistical analysis of test data and more.
Tyler Snyder, currently a sophomore in the College of Engineering, started working in the lab in May 2016. Initially, Tyler was setting up and running four square gear test rigs. He has since taken on a project to redesign and automate the control system of a rolling/sliding contact fatigue (RCF) test machine. The redesign will result in the RCF rig being controlled by a National Instruments system, which will dramatically improve our data reliability and record keeping practices.
Linda Jones, who served as the Administrative Assistant for the Gear Research Institute since its move to Penn State University in 1996 has retired. Some of you have probably met her personally but she was a familiar and helpful voice to all members and sponsors who called in to the Institute at the Applied Research Laboratory. She will be missed, as many of the functions she performed for the Institute were unique and unusual. We are learning to operate without her and in the transition please contact Deborah Corl at (814) 863-4212, until further notice.
With deep sorrow, we also announce the passing away of an active member of the Aerospace Bloc, Doug Roever of Rolls Royce, whose obituary is noted below.
Please take a moment to check it out! http://gearresearch.org/job-postings.html.
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, helical and spiral bevel gears, and gear tooth impact tester. 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 www.gearresearch.org or call Aaron Isaacson, Managing Director, at (814) 865-5832.