Automated thresholding method for the computed tomography inspection of the internal composition of parts fabricated using additive manufacturing

Chisena, Robert S.; Engstrom, Sophia Marina; Shih, Albert J.

doi:10.1016/j.addma.2020.101185

Cited by 5 publications

(2 citation statements)

References 19 publications

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“…Samples were stacked during the scan, and tomography slices were reconstructed using X‐ray cone‐beam back projections. Raw XCT data sets were imported into MATLAB (R2021a) for post‐processing according to the process outlined in Chisena et al 32 . Each sample data set was thresholded and segmented for porosity using a normalized histogram of voxel intensity.…”

Section: Methodsmentioning

confidence: 99%

“…Samples were stacked during the scan, and tomography slices were reconstructed using X-ray cone-beam back projections. Raw XCT data sets were imported into MATLAB (R2021a) for post-processing according to the process outlined in Chisena et al 32 Each sample data set was thresholded and segmented for porosity using a normalized histogram of voxel intensity. Segmentation was conducted according to mixed Gaussian distribution clustering which treats XCT measurement artifacts as random noise and models internal sample features as a mixture of Gaussian distributions.…”

Section: Microstructural and Defect Imagingmentioning

confidence: 99%

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Assessment of flaws in cold‐sintered ZnO via acoustic wave speed and attenuation measurements

et al. 2023

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The cold sintering process (CSP) is a low temperature processing technique that utilizes a transient phase to synthesize dense ceramics. However, some CSP parts contain microflaws that arise due to inhomogeneities in pressure, temperature, and transient phase. This work uses 20 MHz ultrasound to verify the presence of defects in CSP ZnO samples of varying densities (84%–97%). Acoustic metrics used in this work include wave speed, which is affected by differences in the effective elastic properties of the medium, and attenuation, which quantifies wave energy loss due to scattering from defects. Wave speed maps were inhomogeneous, suggesting density gradients which were verified with scanning electron microscopy. In addition, it was demonstrated that the pores produced by cold sintering are anisometric, which increases the anisotropy in the elastic properties. High attenuation regions (>300 Np/m) are present in all samples independent of relative density and correspond to defects identified in X‐ray computed tomography (XCT) which were as small as 38 µm in effective diameter. However, some high attenuation spots do not correspond to visible defects in XCT, which suggests the presence of features undetectable with XCT such as residual secondary phases at the grain boundaries.

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Section: Methodsmentioning

confidence: 99%

Section: Microstructural and Defect Imagingmentioning

confidence: 99%

Assessment of flaws in cold‐sintered ZnO via acoustic wave speed and attenuation measurements

et al. 2023

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Strand width uniformly control for silicone extrusion additive manufacturing based on image processing

Tian

et al. 2022

Int J Adv Manuf Technol

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Evaluation of Flaw Detection Algorithm Using Simulated X-Ray Computed Tomography of Ground Truth Data

Kim

Pintar

Scott

et al. 2023

Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems

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A framework to generate simulated X-ray computed tomography (XCT) data of ground truth (denoted here as ‘GT’) flaws was developed for evaluation of flaw detection algorithms using image comparison metrics. The flaws are mimicking some of those found in additively manufactured parts. The simulated flaw structure gives a GT data set with which to quantitatively evaluate, by calculating exact errors, the results of flaw detection algorithms applied to simulated XCT images. The simulated data avoid time-consuming manual voxel labeling steps needed for many physical data sets to generate GT images. The voxelated pore meshes that exactly match GT images avoid approximations due to converting continuum pore meshes to voxelated GT images. Spherical pores of varying sizes were randomly distributed near the surface and interior of a cylindrical part. XCT simulation was carried out on the structure at three different signal-to-noise levels by changing the number of frames integrated for each projection. Two different local thresholding algorithms (a commercial code and the Bernsen method) and a global thresholding algorithm (Otsu) were used to segment images using varying sets of algorithm parameters. The segmentation results were evaluated with various image evaluation metrics, which showed different behaviors for the three algorithms regarding “closeness” to the GT data. An approach to optimize the thresholding parameters is demonstrated for the commercial flaw detection algorithm based on the semantic evaluation metrics. A framework to evaluate pore sizing error and binary probability of detection was further demonstrated to compare the optimization results.

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Automated thresholding method for the computed tomography inspection of the internal composition of parts fabricated using additive manufacturing

Cited by 5 publications

References 19 publications

Assessment of flaws in cold‐sintered ZnO via acoustic wave speed and attenuation measurements

Assessment of flaws in cold‐sintered ZnO via acoustic wave speed and attenuation measurements

Strand width uniformly control for silicone extrusion additive manufacturing based on image processing

Evaluation of Flaw Detection Algorithm Using Simulated X-Ray Computed Tomography of Ground Truth Data

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