SEDL / STP / STP1201-EB / STP12777S

Comparison of Tension and Flexure to Determine Fatigue Life Prediction Parameters at Elevated Temperatures

Choi, SR
Research AssociatesResident Research Associates, Cleveland State UniversityNASA Lewis Research Center, ClevelandCleveland, OHOH

Salem, JA
Research Engineer, NASA Lewis Research Center, Cleveland, OH

Palko, JL
Research AssociatesResident Research Associates, Cleveland State UniversityNASA Lewis Research Center, ClevelandCleveland, OHOH

Pages: 14    Published: Jan 1994

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Abstract

High temperature slow crack growth of a hot-pressed silicon nitride (NCX 34) was determined at temperatures of 1200 and 1300°C in air. Three different testing methods were utilized: dynamic and static fatigue with bend specimens, and static fatigue with dog-bone-shaped tensile specimens. Good agreement exists between the dynamic and static fatigue results under bending. However, fatigue susceptibility in uniaxial tensile loading was greater than in bending. This result suggests that high temperature fatigue behavior should be measured with a variety of specimen configuration and loading cycles so that adequate lifetime prediction parameters are obtained.