Experimental Study on the Flaw Characterization of Multiple Flaws for Ductile Fracture

<jats:p>Flaw characterization of multiple flaws for ductile fractures was verified by comparing results of flat plate fracture tests and flaw combination rules in typical fitness-for-service codes. Single or double coplanar surface flaws were introduced into flat plate specimens made of Type 304 stainless steel using an electric discharge machine. Fracture tests of sixteen flat plates with flaws were conducted using a tensile testing machine. According in results of the fracture tests, collapse behavior for flat plates with double coplanar flaws was divided into two broad categories. One was coalescence behavior, in which the double flaws combined before the wall was penetrated. The other was penetration behavior, in which the wall was penetrated before coalescence. Rules for characterizing multiple flaws in fitness-for-service codes in Japan, the United States, and Europe were surveyed in order to compare them with test results. When the multiple flaws satisfy the criteria of rules in fitness-for service codes, a single combined flaw is assumed to conservatively estimate the limit load analysis for a ductile fracture. Flaw combination rules in typical fitness-for-service codes were found to conservatively estimate ductile fractures.</jats:p>