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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
The control ((A) no defect) and three different types of defects were prepared ((B) three-wall defect, (C) one-wall defect, and (D) circumferential defect). Each defect was set at a depth of exactly 4 mm.