For the most part, materials used for building stuff are not perfect. By “appropriate design,” the engineer (designer or design team) must achieve (after fabrication consistent with that design) a component, structure, or system that will, when used as prescribed by the engineer (designer or design team), perform satisfactorily throughout the service life indicated by the engineer (designer or design team). In addition to the imperfections present in the original materials, manufacturing of the design may also introduce imperfections, and service-induced deterioration may introduce additional imperfections or cause imperfections already present to change. It is ultimately the responsibility of the engineer (designer, design team) to specify which imperfections must not be present during the service life to avoid failure. Recently the technical community has been involved in an exercise to identify and catalog flaws in materials and components fabricated by the process generally labeled as “additive manufacturing” (AM). This paper will make the case for why this exercise is insufficient for reliably performing nondestructive inspection of components manufactured by AM, an essential process to achieve the engineer’s goal. Focusing efforts on this cataloging effort is a “red herring.” The argument supporting this assertion can be generalized to any engineering design, despite the origin of the materials or manufacturing process, which is meant to achieve and maintain the structural integrity of critical components.
ANSI/ASQC, 1978, Standard-A1 1978 Terms, Symbols and Definitions for Acceptance Sampling, American Society for Quality, Milwaukee, WI.
ASTM International, 2017, E399, “Standard Test Method for Plane-Strain Fracture Toughness of Metallic Materials,” Annual Book of ASTM Standards, Vol. 03.01, ASTM Interna-tional, West Conshohocken, PA.
Dowling, N.E., 2012, Mechanical Behavior of Materials: Engineering Methods for Deformation, Fracture, Fatigue, 4th ed., 2012, Pearson, London, United Kingdom.
Nisitani, Hironobu, and Ken-Ichi Takao, 1981, “Significance of Initiation, Propagation, and Closure of Microcracks in High Cycle of Fatigue of Ductile Metals,” Engineering Fracture Mechanics, Vol. 15 Nos. 3–4, pp. 445–456.
Ritchie, R.O., D.L. Davidson, B.L. Boyce, J.P. Campbell, and O. Roder, 1999, “High-Cycle Fatigue of Ti-6Al-4V,” Fatigue & Fracture of Engineering Materials & Structure, Vol. 22, pp. 621–631.
US DOD, 1994, Military Handbook: Metallic Materials and Elements for Aerospace Vehicle Structures, MIL-HDBK-5G, 2 vols. US Department of Defense, Wright-Patterson AFB, OH.
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