scholarly journals Stress Relaxation Testing as a Basis for Creep Analysis and Design of Silicon Nitride

1999 ◽  
Author(s):  
David A. Woodford ◽  
Andrew A. Wereszczak ◽  
Wate T. Bakker
Keyword(s):  
Silicon Nitride ◽  
Creep Rate ◽  
Stress Relaxation ◽  
Constant Load ◽  
Tensile Creep ◽  
Initial Stresses ◽  
Load Testing ◽  
Analysis And Design ◽  
Creep Analysis ◽  
Significant Impairment

A new approach to tensile creep testing and analysis based on stress relaxation is described for sintered silicon nitride. Creep rate data covering up to five orders of magnitude were generated in tests lasting less than one day. Tests from various initial stresses at temperatures from 1250C to 1350C were analyzed and compared with creep rates measured during conventional constant load testing. It was shown that at least 40% of the creep strain accumulated under all test conditions was recoverable, and that the deformation could properly be described as viscoelastic/plastic. Tests were conducted to establish the level of repeatability and the effects of various thermomechanical histories. It was shown that none of the prior exposures led to significant impairment in creep strength. The results were used for three different grades to establish the value of the accelerated test to compare creep strengths for acceptance and for optimization. Several useful correlations were obtained between stress and creep rate. The systematic creep rate dependence as a function of loading strain prior to relaxation provided a possible basis for design in terms of a secant modulus analysis.

Stress Relaxation Testing as a Basis for Creep Analysis and Design of Silicon Nitride

2000 ◽  
Vol 122 (2) ◽  
pp. 206-211 ◽  
Author(s):  
David A. Woodford ◽  
Andrew A. Wereszczak ◽  
Wate T. Bakker
Keyword(s):  
Silicon Nitride ◽  
Creep Rate ◽  
Stress Relaxation ◽  
Constant Load ◽  
Tensile Creep ◽  
Initial Stresses ◽  
Load Testing ◽  
Analysis And Design ◽  
Creep Analysis ◽  
Significant Impairment

A new approach to tensile creep testing and analysis based on stress relaxation is described for sintered silicon nitride. Creep rate data covering up to five orders of magnitude were generated in tests lasting less than one day. Tests from various initial stresses at temperatures from 1250°C to 1350°C were analyzed and compared with creep rates measured during conventional constant load testing. It was shown that at least 40 percent of the creep strain accumulated under all test conditions was recoverable, and that the deformation could properly be described as viscoelastic/plastic. Tests were conducted to establish the level of repeatability and the effects of various thermomechanical histories. It was shown that none of the prior exposures led to significant impairment in creep strength. The results were used for three different grades to establish the value of the accelerated test to compare creep strengths for acceptance and for optimization. Several useful correlations were obtained between stress and creep rate. The systematic creep rate dependence as a function of loading strain prior to relaxation provided a possible basis for design in terms of a secant modulus analysis. [S0742-4795(00)02302-4]

Stress Relaxation Testing For Analysis of 12Cr1MoVG Steel for Creep Strength Evaluation

2007 ◽  
Vol 353-358 ◽  
pp. 408-411 ◽  
Author(s):  
Wei Ming Sun ◽  
Bing Bing Chen ◽  
Wei Ya Jin ◽  
Zeng Liang Gao
Keyword(s):  
Elevated Temperature ◽  
Stress Relaxation ◽  
Constant Load ◽  
Tensile Creep ◽  
Stress Relaxation Test ◽  
New Approach ◽  
Creep Properties ◽  
Time Stress ◽  
Creep Analysis ◽  
Short Time

The design of pressurized components at elevated temperature is limited by available mechanical properties that often do not span appropriate range of stress, time, strain and temperature. To improve the design process, a new approach based on short-time stress relaxation test (SRT) is introduced in steel tensile creep analysis. The experiments are implemented using SRT and tested for creep properties of 12Cr1MoVG steel at 560 °C. The results of creep curves agree well with the traditional constant load creep test data. The possibility to apply SRT approach is shown promising in the design of the pressurized component at elevated temperature.

Improved creep resistance in anisotropic silicon nitride

2001 ◽  
Vol 16 (8) ◽  
pp. 2182-2185 ◽  
Author(s):  
Naoki Kondo ◽  
Yoshikazu Suzuki ◽  
Manuel E. Brito ◽  
Tatsuki Ohji
Keyword(s):  
Silicon Nitride ◽  
Creep Rate ◽  
Tensile Stress ◽  
Creep Behavior ◽  
Creep Resistance ◽  
Elevated Temperatures ◽  
Tensile Creep ◽  
Grain Alignment ◽  
Remarkable Improvement ◽  
Order Of Magnitude

Tensile creep behavior of silicon nitride with aligned rodlike grains (anisotropic silicon nitride), fabricated by superplastic forging, was investigated at elevated temperatures. Creep rate of the anisotropic silicon nitride was about 1 order of magnitude lower than that of the isotropic one (without forging). The stress sensitivities for the isotropic and anisotropic specimens at 1200 °C were 2.1 and 2.6, respectively, and that for the anisotropic specimen at 1250 °C was 3.6. The grain alignment should cause a remarkable improvement in the creep resistance when a tensile stress is applied along the alignment direction.

Tensile Creep of Y-Si3N4: II. Cavitation

1991 ◽  
Vol 49 ◽  
pp. 972-973 ◽  
Author(s):  
B. J. Hockey ◽  
S. M. Wiederhorn
Keyword(s):  
Silicon Nitride ◽  
Creep Rupture ◽  
Tensile Creep ◽  
Sintering Aids ◽  
Microstructural Changes

ATEM has been used to characterize three different silicon nitride materials after tensile creep in air at 1200 to 1400° C. In Part I, the microstructures and microstructural changes that occur during testing were described, and consistent with that description the designations and sintering aids for these materials were: W/YAS, a SiC whisker reinforced Si3N4 processed with yttria (6w/o) and alumina (1.5w/o); YAS, Si3N4 processed with yttria (6 w/o) and alumina (1.5w/o); and YS, Si3N4 processed with yttria (4.0 w/o). This paper, Part II, addresses the interfacial cavitation processes that occur in these materials and which are ultimately responsible for creep rupture.

scholarly journals Effect of Low-Temperature Annealing on Creep Properties of AlSi10Mg Alloy Produced by Additive Manufacturing: Experiments and Modeling

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 179
Author(s):  
Chiara Paoletti ◽  
Emanuela Cerri ◽  
Emanuele Ghio ◽  
Eleonora Santecchia ◽  
Marcello Cabibbo ◽  
...  
Keyword(s):  
Creep Rate ◽  
Applied Stress ◽  
Minimum Creep Rate ◽  
Annealing Treatment ◽  
Constant Load ◽  
Experimental Conditions ◽  
Creep Properties ◽  
Low Temperature Annealing ◽  
Physically Based ◽  
Excellent Description

The effects of postprocessing annealing at 225 °C for 2 h on the creep properties of AlSi10Mg alloy were investigated through constant load experiments carried out at 150 °C, 175 °C and 225 °C. In the range of the experimental conditions here considered, the annealing treatment resulted in an increase in minimum creep rate for a given stress. The reduction in creep strength was higher at the lowest temperature, while the effect progressively vanished as temperature increased and/or applied stress decreased. The minimum creep rate dependence on applied stress was modeled using a physically-based model which took into account the ripening of Si particles at high temperature and which had been previously applied to the as-deposited alloy. The model was successfully validated, since it gave an excellent description of the experimental data.

The effects of sulfuric acid on the creep, recrystallization, and electrical properties of ice

2003 ◽  
Vol 81 (1-2) ◽  
pp. 395-400 ◽  
Author(s):  
D Iliescu ◽  
I Baker ◽  
X Li
Keyword(s):  
Electrical Resistivity ◽  
Sulfuric Acid ◽  
Single Crystals ◽  
Equal Channel Angular Extrusion ◽  
Boundary Migration ◽  
Constant Load ◽  
Tensile Creep ◽  
Grain Boundary Migration ◽  
Resistivity Measurements ◽  
Lower Resistivity

Both constant load creep and recrystallization are investigated using single crystals of 70–170 ppb sulfuric-acid-doped and -undoped ice. Both sets of crystals exhibited strains in excess of 200% under tensile creep. The undoped specimens reached these strains roughly twice as fast as the doped specimens. After large local strains were imparted to cuboidal single crystals using equal channel angular extrusion at –2°C and subsequent annealing at the same temperature, recrystallization occurred. It was found that a higher concentration of H2SO4 retarded both recrystallization and the subsequent grain-boundary migration. Direct current electrical resistivity measurements performed on polycrystalline, sulfuric-acid-doped (3 ppm) ice at –10°C showed a much lower resistivity in the grain boundaries than in the lattice. PACS No.: 81.90

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