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Foreign Object Damage in Disks of Two Gas-turbine-grade Silicon Nitrides by Steel Ball Projectiles at Ambient TemperatureForeign object damage (FOD) behavior of two commercial gas-turbine-grade silicon nitrides, AS800 and SN282, was determined at ambient temperature through postimpact strength testing of disks impacted by steel ball projectiles with a diameter of 1.59 mm in a velocity range from 115 to 440 m/s. AS800 silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness (k(sub Ic)). The critical impact velocity V(sub c) for which the corresponding postimpact strength was the lowest was V(sub c) approximately equal to 440 and 300 m/s AS800 and SN282, respectively. A unique lower strength regime was typified for both silicon nitrides depending on impact velocity and was attributed to significant radial cracking. The damage generated by projectile impact was typically in the form of ring, radial, and cone cracks with their severity and combination being dependent on impact velocity. Unlike the thick (4 millimeters) flexure bar specimens used in our previous studies, the thin (2 millimeter) disk target specimen exhibited a unique back-side radial cracking on the reverse side just beneath the impact sites at and above impact velocities of 160 meters per second for SN282 and 220 meters per second AS800.
Document ID
20030065966
Acquisition Source
Glenn Research Center
Document Type
Technical Memorandum (TM)
Authors
Choi, Sung R.
(Ohio Aerospace Inst. Brook Park, OH, United States)
Pereira, J. Michael
(NASA Glenn Research Center Cleveland, OH, United States)
Janosik, Lesley A.
(NASA Glenn Research Center Cleveland, OH, United States)
Bhatt, Ramakrishna T.
(NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
September 7, 2013
Publication Date
July 1, 2003
Subject Category
Aircraft Propulsion And Power
Report/Patent Number
NASA/TM-2003-212224
E-13844
NAS 1.15:212224
Funding Number(s)
WBS: WBS 22-708-31-07
Distribution Limits
Public
Copyright
Public Use Permitted.
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