Measurement of the actual fracture toughness of a maraging 300 pressurized cylinder using the vessel as the test specimen

An improved experimental procedure for measuring the actual fracture toughness of a cylindrical pressure vessel is suggested. The 300 maraging-steel thin cylinder itself is used as the test specimen. A small flaw, introduced by a diamond inscriber, serves as a starter for the introduction of a longitudinal semi-elliptical surface crack by fatigue at the cylinder's inner surface. The precracked vessel is hydrostatically pressurized to failure followed by the evaluation of its fracture toughness using Raju and Newman[3] equation for the proper stress intensity factor. The actual material toughness of the maraging-300 vessels is evaluated by conducting a series of experiments on the newly suggested cylindrical specimen. An additional series of tests is then performed, following ASTM procedure E-740-80, on tensile specimens cut from the vessel. The tensile tests yield results that are in excellent agreement with those obtained with the cylindrical specimens thus experimentally validating the new procedure. Suggestions for further development of the new procedure are discussed.