Creep and Creep Rupture of an Advanced Silicon Nitride Ceramic

Ding, Jow‐Lian; Liu, Kenneth C.; More, Karren L.; Brinkman, C.R.

doi:10.1111/j.1151-2916.1994.tb07241.x

Cited by 51 publications

(10 citation statements)

References 18 publications

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“…Results of a compressive creep test at 1300OC are shown in Fig. 10, which also shows previously reported tensile creep data (Ding, 1994) MPa was slightly erratic but the trend of c r q deformation was discernible. Transient creep was observable following each load increment.…”

Section: Test Results and Discussionsupporting

confidence: 83%

A Technique to Achieve Uniform Stress Distribution in Compressive Creep Testing of Advanced Ceramics at High Temperatures

Liu

Stevens

Brinkman

et al. 1997

Journal of Engineering for Gas Turbines and Power

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A technique to achieve stable and uniform uniaxial compression is offered for creep testing of advanced ceramic materials at elevated temperatures, using an innovative self-aligning load-train assembly. Excellent load-train alignment is attributed to the inherent ability of a unique hydraulic universal coupler to maintain self-aligning. Details of key elements, design concept, and principles of operation of the self-aligning coupler are described. A method of alignment verification using a strain-gaged specimen is then discussed. Results of verification tests indicate that bending below 1.5% is routinely achievable with the use of the load-train system. A successful compression creep test is demonstrated using a dumb-bell shaped silicon nitride specimen tested at 1300OC for a period in excess of 4000 h.

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Section: Test Results and Discussionsupporting

confidence: 83%

A Technique to Achieve Uniform Stress Distribution in Compressive Creep Testing of Advanced Ceramics at High Temperatures

Liu

Stevens

Brinkman

et al. 1997

Journal of Engineering for Gas Turbines and Power

Self Cite

View full text Add to dashboard Cite

show abstract

“…It is a nearly universal phenomenon that annealing silicon nitride in air improves its creep resistance. [31][32][33][34][35][36][37][38][39][40] Only rarely does it degrade creep resistance. 38,41 The surface oxide layer that forms during oxidation is only one of the many responses of the material.…”

Section: (2) Specimen Size Effectsmentioning

confidence: 99%

Results of an International Round‐Robin for Tensile Creep Rupture of Silicon Nitride

Luecke

2002

Journal of the American Ceramic Society

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Fourteen laboratories participated in an interlaboratory study to establish the within-and between-laboratory repeatability of tensile creep rupture of silicon nitride. In air at 1375°C at 200 MPa, the times to failure ranged over a factor of 50, and the minimum creep rates ranged over a factor of 20. Despite these large ranges, taken individually, no one laboratory stands out from any other; all produced equally acceptable data. Consumers of silicon nitride tensile creep data must accept this magnitude of variability in reported creep data. The wide variety of specimen shapes and sizes, gripping systems, extensometry techniques, and temperature measurement strategies makes it impossible to assign definitively the root cause of the variability. However, there was a significant specimen size effect. As a group, the smalldiameter specimens lasted roughly five times longer and crept three times more slowly than the large-diameter buttonhead specimens. A possible interpretation of the origin of this difference is that the oxidizing conditions affected more of the volume of the small specimens during the test.

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“…In this case, the creep rate decreases with increasing strain, as many have observed for Si 3 N 4 . [1][2][3]5,6,18,20,22,26,27,56,75 Alternatively, Si 3 N 4 grain contact may impede the sliding that accommodates the redistribution of silicate material and carry part of the load that the silicate pockets originally carried, in effect changing the stress distribution. Hirano et al 58 have attributed the thousand-fold increase in tensile creep resistance of a Si 3 N 4 /SiC "nanocomposite" to suppression of grain-boundary sliding by submicrometer-sized SiC particles on grain boundaries.…”

Section: (4) Predictions Of the Modelmentioning

confidence: 99%

A New Model for Tensile Creep of Silicon Nitride

Luecke

Wiederhorn

1999

Journal of the American Ceramic Society

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The tensile creep rate of most commercial grades of Si 3 N 4 increases strongly with stress. Although the usual powerlaw functions can represent the creep data, the data often show curvature and systematic variations of slope with temperature and stress. In this article, we present a new approach to understanding the creep of ceramics, such as Si 3 N 4 , where a deformable second phase bonds a deformation-resistant major phase. A review of experimental data suggests that the rate of formation and growth of cavities in the second phase controls creep in these materials. The critical step for deformation is the redistribution of the second phase away from the cavitation site to the surrounding volume. The effective viscosity of the second phase and the density of active cavities determine the creep rate. Assuming that the hydrostatic stresses in pockets of the second phase are normally distributed leads to a model that accurately describes the tensile creep rate of grades of Si 3 N 4 . In this model, the creep rate increases exponentially with the applied stress, is independent of Si 3 N 4 grain size, is inversely proportional to the effective viscosity of the deformable phase, and is proportional to the cube of the volume fraction of the deformable phase.

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Creep and Creep Rupture of an Advanced Silicon Nitride Ceramic

Cited by 51 publications

References 18 publications

A Technique to Achieve Uniform Stress Distribution in Compressive Creep Testing of Advanced Ceramics at High Temperatures

A Technique to Achieve Uniform Stress Distribution in Compressive Creep Testing of Advanced Ceramics at High Temperatures

Results of an International Round‐Robin for Tensile Creep Rupture of Silicon Nitride

A New Model for Tensile Creep of Silicon Nitride

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