Fracture initiation in metals under stress wave loading conditions

摘要: An experimental procedure is described for accurately establishing the dynamic fracture initiation properties of structural metals at extremely high loading rates. The apparatus an adaptation Kolsky pressure bar(split-Hopkinson bar) in which a 1-in.-diameter round bar specimen with prefatigued circumferential notch loaded to failure by rapidly rising tensile pulse resulting from explosive detonation. Using standard technique, average stress site measured as function time. Crack opening displacement optical means, time, thus yielding complete load-displacement record each test. From data critical value crack-tip intensity factor, K I c , rates, excess 10 9 psi √in./s may be obtained. This nearly two orders magnitude faster than has been achieved other techniques. Results are presented tests conducted on SAE 4340 steel and 1020 cold-rolled steel, these compared results static performed specimens similar shape.