An ultrasonic method was applied to elastic-plastic fracture toughness testing, and the relationship between the plastic blunting at the fatigue precrack tip or the onset of stable crack growth and the echo difference output voltage characteristics during fracture toughness loading were clarified. The elastic-plastic fracture toughness test procedure based on Top-on and End-on ultrasonic methods was proposed by which the JIc value can be determined using a single specimen. The JIc values for various metallic materials from medium strength steels to aluminum and titanium alloys were evaluated according to the proposed JIc test procedure. The JIc measurements were also compared with those determined according to the SZ method using multiple specimens and those determined according to the AE method using a single specimen. It is confirmed that the proposed JIc test procedure based on Top-on and End-on ultrasonic methods is very useful.
