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

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.