A214 CRITICAL IMPACT VELOCITY OF DAMAGE OF GAS-TURBINE GRADE SILICON NITRIDE CERAMIC UNDER ELEVATED TEMPERATURE WITH TENSILE LOAD(Gas Turbine-7)

2009 ◽  
Vol 2009.2 (0) ◽  
pp. _2-79_-_2-82_
Author(s):  
Takahiro INOUE ◽  
Satoshi SODEOKA ◽  
Hiro YOSHIDA
Keyword(s):  
Elevated Temperature ◽  
Silicon Nitride ◽  
Gas Turbine ◽  
Impact Velocity ◽  
Tensile Load ◽  
Silicon Nitride Ceramic ◽  
Critical Impact Velocity ◽  
Grade Silicon

Foreign Object Damage in Gas-Turbine Grade Silicon Nitrides by Silicon Nitride Ball Projectiles

2009 ◽  
Author(s):  
Sung R. Choi
Keyword(s):  
Silicon Nitride ◽  
Gas Turbine ◽  
Impact Velocity ◽  
Impact Damage ◽  
Hertzian Contact ◽  
Foreign Object ◽  
Silicon Nitrides ◽  
Foreign Object Damage ◽  
Critical Impact Velocity ◽  
Grade Silicon

Foreign object damage (FOD) behavior of two gas-turbine grade silicon nitrides (AS800 and SN282) was determined with a considerable sample size at ambient temperature using impact velocities ranging from 50 to 225 m/s by 1.59-mm diameter silicon nitride ball projectiles. The degree of impact damage as well as of post-impact strength degradation increased with increasing impact velocity, and was greater in SN282 than in AS800 silicon nitride. The critical impact velocity in which target specimens fractured catastrophically was remarkably low: about 200 and 130 m/s, respectively, for AS800 and SN282. The difference in the critical impact velocity and impact damage between the two target silicon nitrides was attributed to the fracture toughness of the target materials. The FOD by silicon nitride projectiles was significantly greater than that by steel ball projectiles. Prediction of impact force was made based on a yield model and compared with the conventional Hertzian contact-stress model.

scholarly journals Experiment on Foreign Object Damage of Gas Turbine-Grade Silicon Nitride Ceramic

1998 ◽  
Author(s):  
Hiro Yoshida ◽  
Takashi Nakashima ◽  
Makoto Yoshida ◽  
Yasushi Hara ◽  
Toru Shimamori
Keyword(s):  
Elevated Temperature ◽  
Silicon Nitride ◽  
Elevated Temperatures ◽  
Tensile Load ◽  
Strength Degradation ◽  
Spall Fracture ◽  
Silicon Nitride Ceramic ◽  
Impact Tests ◽  
The Impact ◽  
Bending Fracture

A new high quality turbine system using monolithic silicon-nitride ceramic is under development. In this study particle impact tests of the silicon-nitride have been tried at room and elevated temperatures with and without tensile load, which simulates centrifugal force of blade rotation. In the experiment 1 mm diameter particle is impacted at velocities up to 900 m s−1. In this paper, critical velocities for bending fracture and Hertzian cracks are examined. Moreover, strength degradation at elevated temperature and spall fracture of the blade are discussed. The main results are: 1) The bending fracture mode critical impact velocity for soft particles is higher than that for hard particles. 2)The impact parameter ϕ for initiation of Hertzian cracks ranges 1.08×10−5 – 1.56×10−5 for the materials tested. 3)Strength degradation at elevated temperature was clearly observed. 4) In the impact tests on blades spall fracture, which was caused by interaction of stress waves, appeared.

Effects of Target Size on Foreign Object Damage in Gas-Turbine Grade Silicon Nitrides by Steel Ball Projectiles

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Sung R. Choi ◽  
Zsolt Rácz
Keyword(s):  
Silicon Nitride ◽  
Gas Turbine ◽  
Impact Velocity ◽  
Steel Ball ◽  
Target Size ◽  
Hertzian Contact ◽  
Foreign Object ◽  
Silicon Nitrides ◽  
Foreign Object Damage ◽  
Grade Silicon

Foreign object damage (FOD) phenomena of two gas-turbine grade silicon nitrides (AS800 and SN282) were assessed at ambient temperature applying impact velocities from 20 to 300 m/s using 1.59-mm diameter hardened steel ball projectiles. Targets in a flexural configuration with two different sizes (thicknesses) of 1 and 2 mm were ballistic-impacted under a fully supported condition. The severity of impact damage, as well as the degree of post-impact strength degradation, increased with increasing impact velocity, increased with decreasing target size, and was greater in SN282 than in AS800 silicon nitride. The critical impact velocity where targets fractured catastrophically decreased with decreasing target size and was lower in SN282 than in AS800. Overall, FOD by steel projectiles was significantly less than that by silicon-nitride ceramic counterparts, due to much decreased Hertzian contact stresses. A correlation of backside cracking velocity versus target size was made based on a simplified elastic foundation analysis.

Effects of Target Size on Foreign Object Damage in Gas-Turbine Grade Silicon Nitrides by Steel Ball Projectiles

2011 ◽  
Author(s):  
Sung R. Choi ◽  
Zsolt Ra´cz
Keyword(s):  
Silicon Nitride ◽  
Gas Turbine ◽  
Impact Velocity ◽  
Steel Ball ◽  
Target Size ◽  
Hertzian Contact ◽  
Foreign Object ◽  
Silicon Nitrides ◽  
Foreign Object Damage ◽  
Grade Silicon

Foreign object damage (FOD) phenomena of two gas-turbine grade silicon nitrides (AS800 and SN282) were assessed at ambient temperature applying impact velocities from 20 to 300 m/s using 1.59-mm diameter hardened steel ball projectiles. Targets in a flexural configuration with two different sizes (thicknesses) of 1 and 2 mm were ballistic-impacted under a fully supported condition. The severity of impact damage, as well as the degree of post-impact strength degradation, increased with increasing impact velocity, increased with decreasing target size, and was greater in SN282 than in AS800 silicon nitride. The critical impact velocity where targets fractured catastrophically decreased with decreasing target size and was lower in SN282 than in AS800. Overall, FOD by steel projectiles was significantly less than that by silicon-nitride ceramic counterparts, due to much decreased Hertzian contact stresses. A correlation of backside cracking velocity versus target size was made based on a simplified elastic foundation analysis.

Target Size Effects on Foreign Object Damage in Gas-Turbine Grade Silicon Nitrides by Ceramic Ball Projectiles

2010 ◽  
Author(s):  
Sung R. Choi ◽  
Zsolt Ra´cz
Keyword(s):  
Silicon Nitride ◽  
Gas Turbine ◽  
Impact Velocity ◽  
Impact Damage ◽  
Target Thickness ◽  
Foreign Object ◽  
Silicon Nitrides ◽  
Foreign Object Damage ◽  
Post Impact ◽  
Grade Silicon

Foreign object damage (FOD) phenomena of two gas-turbine grade silicon nitrides (AS800 and SN282) were determined at ambient temperature using impact velocities ranging from 25 to 150 m/s by 1.59-mm diameter silicon nitride ball projectiles. Targets in flexure bar configuration with two different thicknesses of 1 and 2 mm were impacted under a fully supported condition. The degree of impact damage as well as of post-impact strength degradation increased with increasing impact velocity, increased with decreasing target thickness, and was greater in SN282 than in AS800 silicon nitride regardless of target thickness. The critical impact velocity, in which targets fractured catastrophically, decreased monotonically with decreasing target thickness and was lower in SN282 than in AS800. Backside cracking was dominant in both AS800 and SN282 target specimens with a thickness of 1 mm, occurring from an impact velocity of 50 m/s. A backside cracking analysis based on the elastic foundation approach was made as a function of target thickness. Overall, FOD by ceramic projectiles was significantly greater than that by hardened metallic counterparts.

Impact Fracture Behavior of Turbine-Grade Silicon Nitride Ceramic Under Tensile Stress at Elevated Temperatures

2005 ◽  
Author(s):  
Hiro Yoshida ◽  
M. Munawar Chaudhri ◽  
Takero Fukudome ◽  
Sazo Tsuruzono
Keyword(s):  
Silicon Nitride ◽  
Tensile Stress ◽  
Elevated Temperatures ◽  
Strength Degradation ◽  
Stress Effect ◽  
Predominant Role ◽  
Silicon Nitride Ceramic ◽  
Impact Fracture Behavior ◽  
Grade Silicon ◽  
Effects Of Temperature

A series of particle impact tests was carried out at elevated temperatures up to 1400°C and under tensile stresses up to 200 MPa using a gas turbine-grade silicon nitride (SN282-Kyocera Corporation). It was found that: 1) At room temperature, 100 MPa tensile stress brings 8% strength degradation. 2) Regarding the effect of the temperature without applying tensile stress, similar to the case of quasi-static loading, the fracture toughness seems to play a predominant role under the dynamic loading also. 3) At 1350°C under 100 MPa tensile stress, effect of the stress on the degradation increases by 15%. 4) The effects of temperature and tensile stress on the strength degradation seem to be additive for temperatures up to 1350°C. Above 1350°C, remarkable strength degradation appears.

scholarly journals Hot Pressed Silcon Nitride for Gas Turbine Applications

1972 ◽  
Author(s):  
M. L. Torti ◽  
G. Q. Weaver ◽  
D. W. Richerson
Keyword(s):  
Elevated Temperature ◽  
Silicon Nitride ◽  
Thermal Shock ◽  
Gas Turbine ◽  
Thermal Shock Resistance ◽  
Room Temperature ◽  
Promising Candidate ◽  
Shock Resistance ◽  
Room Temperature Strength

The high strengths now attainable with hot pressed silicon nitride combined with its good oxidation and thermal shock resistance make it a most promising candidate for advanced gas turbine hot components. This form of silicon nitride has flexural strengths of 110,000 psi at room temperature and 60,000 psi at 1200 C. A recent experimental version of the system has exhibited room temperature strength of 145,000 psi and elevated temperature (1200 C) strength of 100,000 psi. This may be the highest strength reported on any material at this elevated temperature.

Foreign Object Damage of Two Gas-Turbine Grade Silicon Nitrides in a Thin Disk Configuration

2003 ◽  
Author(s):  
Sung R. Choi ◽  
J. Michael Pereira ◽  
Lesley A. Janosik ◽  
Ramakrishna T. Bhatt
Keyword(s):  
Impact Strength ◽  
Gas Turbine ◽  
Impact Velocity ◽  
Foreign Object ◽  
Silicon Nitrides ◽  
Foreign Object Damage ◽  
Post Impact ◽  
Grade Silicon ◽  
Thin Disks ◽  
The Impact

Foreign object damage (FOD) behavior of two commercial gas-turbine grade silicon nitrides, AS800 and SN282, was determined at ambient temperature through post-impact strength testing for thin 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 (KIC). The critical impact velocity in which the corresponding post-impact strength yielded the lowest value was Vc ≈ 440 and 300 m/s for AS800 and SN282, respectively. A unique lower-strength regime was typified for both silicon nitrides depending on impact velocity, attributed to significant radial cracking. The damages generated by projectile impact were typically in the forms of ring, radial, and cone cracks with their severity and combination being dependent on impact velocity. Unlike thick (3 mm) flexure bar specimens used in the previous studies, thin (2 mm) disk target specimens exhibited a unique backside radial cracking occurring on the reverse side just beneath the impact sites at and above impact velocity of 160 and 220 m/s for SN282 and AS800, respectively.

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