SEDL / STP / STP1172-EB / STP24707S

Some Observations in Fracture Toughness and Fatigue Testing with Chevron-Notched Specimens

Salem, JA
National Aeronautics and Space Administration, Lewis Research Center, Cleveland, OH

Shannon, JL
National Aeronautics and Space Administration, Lewis Research Center, Cleveland, OH

Jenkins, MG
Oak Ridge National Laboratory, Oak Ridge, TN

Pages: 17    Published: Jan 1992

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Abstract

Chevron-notched specimens were used to test metallic and ceramic materials over a range of temperatures and testing conditions. The materials tested were M-50 bearing steel, alumina, silicon carbide, monolithic silicon nitride, and in situ toughened silicon nitride. Results were compared to measurements performed with compact-tension specimens, singleedge notched beam specimens, or single-edge precracked beam specimens.

Measured properties included fracture toughness, crack growth resistance, and fatigue crack growth rate. For materials with rising R-curves, the fracture toughness measured with chevron-notched specimens was dependent on specimen proportions and notch geometry, as related to the amount of crack extension to the measurement point. For materials with flat R-curves, the chevron-notch test is independent of notch geometry and specimen proportions.