Tempered martensite embrittlement in low alloy steel was studied in terms of fracture toughness. The effects of plate thickness and notch root radius on crack initiation were analysed from a view point of fracture mechanics.
The results obtained are summarized as follows:
(1) The decrease in crack initiation stress intensity factor Kinit for the fatigue precracked specimens under plane strain conditions corresponded to the degree of tempered martensite embrittlement.
(2) The crack initiation stress intensity factor was correlated to the square root of the notch radius ρ1/2 for the thick specimens. Tempered martensite embrittlement appears in the crack initiation stress intensity factor Kinit of the specimen having a large notch root radius and large thickness.
