Effect of cyclic loading on the creep performance of silicon nitride

Technical Report · Sat Apr 01 04:00:00 EST 1995

DOI:https://doi.org/10.2172/52850· OSTI ID:52850

Wereszczak, A A; Ferber, M K; Kirkland, T P ^[1]; Lin, C K.J. ^[2]

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1. Oak Ridge National Lab., TN (United States). High Temperature Materials Lab.
2. National Central Univ., Chung-Li (Taiwan, Province of China). Dept. of Mechanical Engineering

Tension-tension cyclic fatigue tests (triangular waveform, {sigma}{sub max} = 100 MPa, R = 0.1) were conducted on hot isostatically pressed (HIPed) silicon nitride at frequencies spanning several orders of magnitude (5.6 {times} 10{sup {minus}6} to 0.1 Hz or 10{sup {minus}3} MPa/s to 18 MPa/s) at 1,370 C in air. The amount of cyclic creep strain was found to be a function of the frequency or stressing rate with greater strains to failure observed as the frequency or stressing rate decreased. The total strain was viewed as the sum of elastic, anelastic (or transient recoverable), and plastic (viscous or non-recoverable) strain contributions, after the empirical Pao and Marin model. The plastic strain was found to be the dominant component of the total creep and was unsatisfactorily represented by the Pao and Marin model. To circumvent this, a time exponent was introduced in the plastic strain term in the Pao and Marin model. This modification resulted in good correlation between model and experiment at the slower frequencies examined but over-predicted the cyclic creep strain at the faster frequencies. The utility of using the modified Pao and Marin model to predict cyclic creep response from static creep and strain relaxation tests is described.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 52850
• Report Number(s): CONF-950629--6; ON: DE95010289
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPARATIVE EVALUATIONS
CREEP
EXPERIMENTAL DATA
FATIGUE
MATHEMATICAL MODELS
MECHANICAL TESTS
MICROSTRUCTURE
SILICON NITRIDES
THEORETICAL DATA