An extensive study of the use of the chevron-notched short-bar (CNSB) specimen for measuring plane-strain fracture toughness in high-strength aluminum alloys is reported. The toughness measured in a CNSB specimen, K_SB, correlates closely with plane-strain fracture toughness, K_Ic, for toughnesses less than 35 MPa m^1/2. At higher toughnesses K_SB is higher than K_Ic for two reasons; first, sample heterogeneity causes the different sized specimens to sample different material, and second, an effect of rising crack growth resistance in the toughness range 40 to 55 MPa m^1/2; these latter test results should be considered invalid; however, within this range the K_Ic, K_SB correlation, although largely empirical, is still useful for screening purposes.

The toughness in high-strength aluminum alloy rolled plate may vary markedly through the plate thickness. Examples of these variations are presented.