Size Requirements for Fatigue-Cracked Fracture Toughness Screening Specimens

Aluminum, titanium and steel alloys were selected on the basis of their strength/toughness properties for the purpose of investigating the performance of a proposed fatigue-cracked fracture toughness screening specimen. Specimens of varying thicknesses and widths were tested with the largest specimen of each alloy satisfying the minimum size requirements according to ASTM-E-399-74 specifications. The results of this program demonstrate the feasibility of the proposed specimen configuration with lowest width to thickness ratio showing the best correlation between the net-fracture strength and plane strain fracture toughness K sub I sub C. Further investigation is warranted to assess the effects of specimen eccentricity and other limitations related to relative toughness of the material. Prepared in cooperation with Del Research Corp., Hellertown, Pa.