Creep design analysis of silicon nitride using stress relaxation data

✍ Scribed by David A. Woodford

• Publisher: Elsevier Science
• Year: 1996
• Weight: 633 KB
• Volume: 17
• Category: Article
• ISSN: 0261-3069
• DOI: 10.1016/s0261-3069(96)00043-x

✦ Synopsis

A new approach to tensile creep analysis of ceramics based on stress relaxation testing is described for sintered silicon nitride. The results are presented in terms of creep rate vs. stress, covering a maximum of five orders of magnitude in tests lasting less than one day. Tests for various initial stresses, and at temperatures between 1200°C and 135O"C, are analyzed, and compared with creep rates measured during conventional constant load testing. It is shown that a significant portion of the accumulated creep strain is anelastic and recoverable. This is confirmed using repeated tensile loading and unloading over a given range of temperature. Pseudo stress vs. time curves, generated from the data, show a strong rate sensitivity, which is confirmed in a low stress rate tensile test. A design analysis is made based on a characteristic stress vs. creep rate response at each temperature.

This is parameterized and used as a basis for a stress-temperature curve for a projected creep life.