Tests were conducted to determine J_Ic from resistance curves of J versus crack extension, obtained from fatigue-precracked specimens of a titanium 6Al-4V alloy. Specimens of various geometries were employed, all in three-point bending. Crack extensions were delineated by heat tinting.

Results obtained with J computed from the equation, J = 2A/Bb, are compared to those obtained with the compliance technique, using the plane-stress solutions of Bucci et al. J_Ic results are compared with a valid K_Ic value for this material.

The range of ratios of crack length to specimen width (a/W) is explored over which the equation J = 2A/Bb applies. The decrease in crack extension at experimental limit load (Δa_pmax →Δa_c) is examined as the ratio of specimen thickness to uncracked ligament (B/b) is increased. Variation in J_Ic from specimens cut from different positions through the plate thickness is also examined.