Computed Tomography for the Nondestructive Testing of Additive Manufactured Components: Opportunities and Limitations

The additive manufacturing (AM) process has grown from university research laboratories into a production process for complex-shaped components. Due to the uniqueness of the manufacturing process, new challenges have arisen regarding process control, quality assurance, and surface finishing. This paper will show how the nondestructive radiographic testing (RT) technique computed tomography (CT) can make a valuable contribution to quality assurance at each step of the AM process. The use of CT is demonstrated using an example of chrome-nickel steel nozzles manufactured using the laser powder bed fusion (LPBF) process. The surface of the nozzles is then reworked with the Hirtisation process, a trademarked part finishing technology that is based on a combination of electrochemical pulse methods, hydrodynamic flow and particle assisted chemical removal, and surface treatment. In addition to the already known use of CT for detecting internal discontinuities, CT can be used to ensure sufficient wall thickness, measure internal channel surface roughness, and gauge the geometrical correctness of parts. In this paper, it is demonstrated how to use this RT technique to optimize the design and production process during the component development phase.

Weighting and standardization of frequencies to determine prevalence of AD imaging biomarkers

Objective:To estimate the prevalence of elevated brain amyloid and reduced cortical thickness (as a marker for neurodegeneration) in a defined population.Methods:Mayo Clinic Study of Aging participants underwent MRI to assess a composite Alzheimer disease (AD) signature cortical thickness measure and PET to assess brain amyloid accumulation. Participants were characterized as having elevated amyloid (A+/A−), reduced cortical thickness (N+/N−), and A+N+, A+N−, A−N+, or A−N−. The prevalence of AD biomarkers was derived by adjusting for nonparticipation and standardizing to the Olmsted County, Minnesota, population.Results:Among 1,646 participants without dementia (mean age 70.8 years; 53.2% men), the prevalence (95% confidence interval) of amyloidosis was 21.1% (19.1%–23.2%): women, 24.3%; men, 17.5%. The prevalence of reduced cortical thickness was 28.9% (26.4%–31.5%): women, 27.9%; men, 30.2%. The prevalence estimates of biomarker categories were as follows: A−N−: 61.4%; A+N−: 9.7%; A−N+: 17.4%; and A+N+: 11.5%, and varied by sex and byAPOEε4 carrier status. In men, prevalence estimates were as follows: A−N−: 62.6%; A+N−: 7.3%; A−N+: 19.9%; and A+N+: 10.2%. In women, prevalence estimates were as follows: A−N−: 60.4%; A+N−: 11.7%; A−N+: 15.3%; and A+N+: 12.6%. In ε4 carriers, prevalence estimates were as follows: A−N−: 54.6%; A+N−: 16.6%; A−N+: 12.4%; and A+N+: 16.4%. In non-ε4 carriers, prevalence estimates were as follows: A−N−: 63.3%; A+N−: 6.9%; A−N+: 19.9%; and A+N+: 10.0%.Conclusions:These prevalence estimates are important for understanding age-related trends in amyloid positivity and AD signature cortical thickness in the population, and for potentially projecting the future burden of biomarkers in elderly persons.

Cortical Thinning in Network-Associated Regions in Cognitively Normal and Below-Normal Range Schizophrenia

This study assessed whether cortical thickness across the brain and regionally in terms of the default mode, salience, and central executive networks differentiates schizophrenia patients and healthy controls with normal range or below-normal range cognitive performance. Cognitive normality was defined using the MATRICS Consensus Cognitive Battery (MCCB) composite score (T=50 ± 10) and structural magnetic resonance imaging was used to generate cortical thickness data. Whole brain analysis revealed that cognitively normal range controls (n=39) had greater cortical thickness than both cognitively normal (n=17) and below-normal range (n=49) patients. Cognitively normal controls also demonstrated greater thickness than patients in regions associated with the default mode and salience, but not central executive networks. No differences on any thickness measure were found between cognitively normal range and below-normal range controls (n=24) or between cognitively normal and below-normal range patients. In addition, structural covariance between network regions was high and similar across subgroups. Positive and negative symptom severity did not correlate with thickness values. Cortical thinning across the brain and regionally in relation to the default and salience networks may index shared aspects of the psychotic psychopathology that defines schizophrenia with no relation to cognitive impairment.

Tangential Biopsy Thickness versus Lesion Depth in Longitudinal Melanonychia: A Pilot Study

Longitudinal melanonychia can be caused by melanocyte activation (hypermelanosis) or proliferation (lentigo, nevus or melanoma). Histopathologic examination is mandatory for suspicious cases of melanomas. Tangential biopsy of the matrix is an elegant technique avoiding nail plate dystrophy, but it was unknown whether the depth of the sample obtained by this method is adequate for histopathologic diagnosis. Twenty-two patients with longitudinal melanonychia striata were submitted to tangential matrix biopsies described by Haneke. The tissue was stained with hematoxylin-eosin and the specimens were measured at 3 distinct points according to the total thickness: largest (A), intermediate (B) and narrowest (C) then divided into 4 groups according to the histopathologic diagnosis (G1: hypermelanosis; G2: lentigos; G3: nevus; G4: melanoma). The lesions were measured using the same method. The mean specimen/lesion thickness measure values for each group was: G1: 0,59/0,10 mm, G2: 0,67/0,08 mm, G3: 0,52/0,05 mm, G4: 0,58/0,10 mm. The general average thickness for all the specimens/lesions was 0,59/0,08 mm. We concluded that the tangential excision, for longitudinal melanonychia, provides an adequate material for histopathological diagnosis.

The Coating Fragile Phase Thickness Measure Methods of Galvannealed Steel Sheet

Powdering and desquamation is prone to happen when galvannealed sheet steel is stampinged and Powdering or desquamation often happens at the fragile phase where Fe content is high. The fragile phase thickness of the coating of galvannealed steel sheet is correlative nearly to the coating anti-pulverization ability.So it is very important to measure the fragile phase thickness with the research of galvannealed sheet steel process. The fragile phase thickness of the same batch galvannealed sheet steel made by some steel plant is about 560~590nm when it is measured by glow ischarge spectrometer , fracture observation methods by SEM and metallographic microscope, the error is very little.