A round-robin project in Japan for the evaluation of nondestructive responses of natural flaws

This paper introduces the current status of a round-robin project aiming at gathering non-destructive data of natural flaws. The project, which was launched in 2009, prepared specimens containing artificial stress corrosion cracks and thermal fatigue cracks, and served the specimens to a round-robin test to gather non-destructive data. A total of 12 universities and research institutes have participated to the round-robin test. Some of the specimens are already destroyed to confirm the true profiles of the cracks, whereas others remain undestroyed. All the data are presented at a dedicated webpage, together with the results of the destructive tests, so that they are freely available for anybody. Keywords: thermal fatigue crack, stress corrosion cracking, electromagnetic nondestructive testing, ultrasonic testing, numerical modelin

Fabrication of imitative cracks by 3D printing for electromagnetic nondestructive testing and evaluations

AbstractThis study demonstrates that 3D printing technology offers a simple, easy, and cost-effective method to fabricate artificial flaws simulating real cracks from the viewpoint of eddy current testing. The method does not attempt to produce a flaw whose morphology mirrors that of a real crack but instead produces a relatively simple artificial flaw. The parameters of this flaw that have dominant effects on eddy current signals can be quantitatively controlled. Three artificial flaws in type 316L austenitic stainless steel plates were fabricated using a powderbed-based laser metal additive manufacturing machine. The three artificial flaws were designed to have the same length, depth, and opening but different branching and electrical contacts between flaw surfaces. The flaws were measured by eddy current testing using an absolute type pancake probe. The signals due to the three flaws clearly differed from each other although the flaws had the same length and depth. These results were supported by subsequent destructive tests and finite element analyses