Tutorial
Monday, July 15, 2024
1:00 PM – 5:00 PM
Nondestructive Testing for Additive Manufacturing
Orion Kafka, Newell Moser and Ward Johnson (National Institute of Standards and Technology, Applied Chemicals and Materials Division, Boulder, CO)
In this tutorial we will survey topics related to nondestructive testing as it relates to additively manufactured (AM) materials, with a highlight on those with which our team has particular expertise: 1) acoustic methods, 2) x-ray computed tomography and 3D image assessment.
Acoustic techniques can rapidly and cost-effectively provide information on internal flaws and material properties of additively manufactured materials. A broad survey of acoustic techniques currently being pursued for in-process monitoring and post-build assessment will be presented, with a focus on relative limitations and the types of defects detectable with each technique. A more detailed summary will then be presented of nonlinear acoustic techniques for detecting distributed defects in AM metal parts, including an innovative nonlinear reverberation spectroscopic technique that is being developed at NIST.
X-ray computed tomography (XCT) is a nondestructive measurement technique that provides topology information of objects, enabling users to visualize both internal and external features in 3D. XCT can thus be used to conduct quantitative, scientific measurements of AM parts. We will discuss the physicals aspects of the process, including specimen preparation and mounting, optional stages (e.g., environmental, load), and some considerations needed when configuring machine settings such as x-ray energy and exposure time. Impacts upon sensitivity and uncertainty of the raw instrument images (radiographs) will be discussed. We will then discuss algorithmic aspects to processing XCT images, including the reconstruction of radiographs into 3D gray-scale images as well as processing these images to conduct quantitative analysis tasks (e.g., measurement of pores and surface roughness).