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Computational Modeling Develops Ultra-Hard Steel
Industrial Productivity
Originating Technology/NASA Contribution
Glenn Research Center’s Mechanical Components Branch routinely
conducts research on transmissions and gearing for advanced
gas turbines, promoting their safety, weight reduction, and
reliability. The Mechanical Components Branch is staffed
by both NASA and U.S. Army Research Laboratory employees,
and the research program is designed and executed to meet
the needs of both organizations. The researchers have developed
a world-class set of instruments and test devices, including
a spiral bevel or face gear test rig for testing thermal
behavior, surface fatigue, strain, vibration, and noise;
a full-scale, 500-horsepower helicopter main-rotor transmission
testing stand; a gear rig that allows fundamental studies
of the dynamic behavior of gear systems and gear noise; and
a high-speed helical gear test for analyzing thermal behavior
for rotorcraft. These are just a few examples of the highly
specialized equipment the researchers at the Mechanical Components
Branch have at their disposal.
Since 1972, the branch’s spur gear fatigue rig has set the
standard for gear surface fatigue experiments, enabling development
of robust, efficient, and safe gas turbines and rotorcraft.
The test rig provides accelerated fatigue life testing for
standard spur gears at speeds
of up to 10,000 rotations per minute, and enables engineers
to investigate the effects of materials, heat
treat, shot peen, lubricants, as well as other factors, on
the gear’s performance.
Partnership
QuesTek Innovations LLC, based in Evanston, Illinois, is
an innovative materials solutions company that designs and
develops new materials in less than 50 percent of the time
and at less than 30 percent of the cost of traditional empirical
methods.
QuesTek provides unique materials solutions to a variety
of customers by using its powerful mechanistic computational
models to design steels and alloys to customer requirements.
The company’s methodology uniquely allows for design trade-offs,
such as steels optimally balanced for strength, toughness,
and corrosion resistance. Employing computational materials
design techniques, QuesTek uses fundamental thermodynamic
and kinetic data to predict alloy microstructures;
in contrast to traditional empirical—trial and error—approaches.
QuesTek recently developed a carburized, martensitic gear
steel with an ultra-hard case using its computational design
methodology, but needed to verify surface fatigue, lifecycle
performance, and overall reliability.
The Battelle Memorial Institute, a nonprofit global science
and technology enterprise that develops and commercializes
technology and manages laboratories for customers, introduced
the company to researchers at Glenn’s Mechanical Components
Branch and facilitated a partnership allowing researchers
at the NASA Center to conduct spur gear fatigue testing for
the company.
Testing revealed that QuesTek’s gear steel outperforms the
current state-of-the-art alloys used for aviation gears in
contact fatigue by almost 300 percent. This testing generated
necessary data to demonstrate the superiority of the ultra-hard
case alloy and quantified the contact fatigue benefit attainable
using QuesTek’s material. However, bending fatigue testing
demonstrated that the bending fatigue capability of the new
steel was somewhat less than the capability of the current
state-of-the-art alloys used for aviation gears. The test
data has provided guidance for engineers to select the best
combination of properties to satisfy the requirements of
a given application.
Product Outcome
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Uses
for this new class of steel are limitless in areas
needing exceptional strength for high-throughput
applications. |
With the confidence and credibility provided by the NASA
testing, QuesTek is commercializing two new steel alloys.
These alloys combine maximum case hardness with a tough,
ductile core, promoting high wear and contact fatigue life
and offer a 20-percent increase (or more) in gear endurance
in high-power density aerospace transmission systems.
Uses for this new class of steel are limitless in areas needing
exceptional strength for high-throughput applications. The
material is already being used in racing markets. For instance,
QuesTek’s C61 material was the power behind the Class 1600
champion in last year’s Baja 1000 off-road race. Aside from
racing, this high-performance material is in testing for
heavy equipment gearing and in oil/gas gearing applications.
NASA is interested in the materials for use in developing
vertical takeoff and landing vehicles, based on conventional
rotorcraft but with the speed and high-altitude performance
of turbo propellers. Advancements in gear design and reliability
make possible the development of these highly specialized
vehicles.
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