Residual Stress Measurements in Extreme Environments for Hazardous, Layered Specimens

Abstract Background In nuclear fuel plates of low-enriched U-10Mo (LEU) clad with aluminum by hot isostatic pressing (HIP), post-irradiation stresses arising during reactor shutdown are a major concern for safe reactor operations. Measurement of those residual stresses has not previously been possible because the high radioactivity of the plates requires handling only by remote manipulation in a hot cell. Objective The incremental slitting method for measuring through-thickness stress profiles was modified, and a system for automated, remote operation was built and tested. Methods Experimental modifications consisted of replacing electric-discharge machining (EDM) with a small end mill and strain-gauge measurements with cantilever displacement measurements. The inverse method used to calculate stresses was the pulse-regularization method modified to allow discontinuities across material interfaces. The new system was validated by comparing with conventional slitting on a depleted U-10Mo (DU) fuel plate. Results The new system was applied to two measurements each on six as-fabricated (pre-irradiation) LEU miniature fuel plates. Variations between the measurements at two locations in the same plate were strongly correlated with measured geometrical heterogeneity in the plate—a tilt in the fuel foil. Compressive stresses in the U-10Mo were shown to increase from 20 to 250 MPa as the ratio of aluminum thickness to U-10Mo thickness increased causing increased constraint during cooling. Faster cooling rates during processing also increased stress magnitudes. Conclusions The measurements trends agreed with data in the literature from similar plates made with DU, which further validates the method. Because other methods are impractical in a hot cell, the modified slitting method is now poised for the first measurements of post-irradiation stresses.

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Effect of post-processing on microstructure and mechanical properties of Alloy 718 fabricated using powder bed fusion additive manufacturing processes

Rapid Prototyping Journal ◽

10.1108/rpj-12-2019-0310 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Sareh Götelid ◽

Taoran Ma ◽

Christophe Lyphout ◽

Jesper Vang ◽

Emil Stålnacke ◽

...

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Residual Stresses ◽

Design Methodology ◽

Hot Isostatic Pressing ◽

Powder Bed Fusion ◽

Content Type ◽

Powder Bed ◽

Nickel Based Superalloy ◽

Compressive Stresses

Purpose This study aims to investigate additive manufacturing of nickel-based superalloy IN718 made by powder bed fusion processes: powder bed fusion laser beam (PBF-LB) and powder bed fusion electron beam (PBF-EB). Design/methodology/approach This work has focused on the influence of building methods and post-fabrication processes on the final part properties, including microstructure, surface quality, residual stresses and mechanical properties. Findings PBF-LB produced a much smoother surface. Blasting and shot peening (SP) reduced the roughness even more but did not affect the PBF-EB surface finish as much. As-printed PBF-EB parts have low residual stresses in all directions, whereas it was much higher for PBF-LB. However, heat treatment removed the stresses and SP created compressive stresses for samples from both PBF processes. The standard Arcam process parameter for PBF-EB for IN718 is not fully optimized, which leads to porosity and inferior mechanical properties. However, impact toughness after hot isostatic pressing was surprisingly high. Originality/value The two processes gave different results and also responses to post-treatments, which could be of advantage or disadvantage for different applications. Suggestions for improving the properties of parts produced by each method are presented.

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Quantification of Steatosis and Fibrosis using a new system implemented in an ultrasound machine

Medical Ultrasonography ◽

10.11152/mu-2495 ◽

2020 ◽

Vol 22 (3) ◽

pp. 265 ◽

Cited By ~ 1

Author(s):

Ioan Sporea ◽

Victor Bâldea ◽

Raluca Lupușoru ◽

Felix Bende ◽

Ruxandra Mare ◽

...

Keyword(s):

Transient Elastography ◽

Liver Stiffness ◽

Shear Wave Elastography ◽

Strong Positive Correlation ◽

Strongly Correlated ◽

Controlled Attenuation Parameter ◽

Attenuation Parameter ◽

Range Interval ◽

Attenuation Imaging ◽

New System

Aim: The study compared the usefulness of 2D-SWE and attenuation measurements obtained using Aplio i800 from Canon together with Transient Elastography (TE) and the Controlled Attenuation Parameter (CAP) as the reference method.Material and methods: We included 112 consecutive adults with reliable LS measurements, 44 healthy subjects and 68 subjects with chronic hepatopathies in whom liver stiffness (LS) and steatosis were evaluated in the same session employing two elastography techniques: Transient Elastography (TE) with Controlled Attenuation Parameter (CAP) implemented on the FibroScan® 530 Compact system and Two Dimensional Shear Wave Elastography (2D-SWE) with Attenuation Imaging (ATI) installed on the Aplio i800 series ultrasound system. Reliable measurements were defined as the median value of 10, respectively 5 valid LS measurements for TE and 2D-SWE, with an interquartile range interval/median ratio (IQR/M) <30%.Results: A very strong positive correlation was found between LS values obtained by TE and 2D-SWE: r=0.88, p<0.0001 and between the attenuation coefficients of steatosis obtained by CAP and ATI, r=0.81, p<0.0001. The best cut-off values by 2DSWE for predicting different stages of liver fibrosis were: for F≥2 - 7.9 kPa and F=4 - 11.7 kPa. Regarding steatosis, the best ATI cut-off values were: for S≥1 - 0.79 dB/cm/mHz and for S3 - 0.86 dB/cm/mHz.Conclusion: 2D-SWE and ATI measurements with the new system strongly correlated with TE and CAP results.

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TEM Studies of Grain Boundary Films in Si3N4 Ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088968 ◽

1991 ◽

Vol 49 ◽

pp. 930-931

Author(s):

H.-J. Kleebe ◽

J.S. Vetrano ◽

J. Bruley ◽

M. Rühle

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Silicon Nitride ◽

Hot Isostatic Pressing ◽

Amorphous Film ◽

Liquid Phase Sintering ◽

Second Phase ◽

High Temperature Mechanical Properties ◽

Triple Points ◽

Boundary Films

It is expected that silicon nitride based ceramics will be used as high-temperature structural components. Though much progress has been made in both processing techniques and microstructural control, the mechanical properties required have not yet been achieved. It is thought that the high-temperature mechanical properties of Si3N4 are limited largely by the secondary glassy phases present at triple points. These are due to various oxide additives used to promote liquid-phase sintering. Therefore, many attempts have been performed to crystallize these second phase glassy pockets in order to improve high temperature properties. In addition to the glassy or crystallized second phases at triple points a thin amorphous film exists at two-grain junctions. This thin film is found even in silicon nitride formed by hot isostatic pressing (HIPing) without additives. It has been proposed by Clarke that an amorphous film can exist at two-grain junctions with an equilibrium thickness.

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The Response of Testis Cells to Low Dose X-Irradiation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100099155 ◽

1981 ◽

Vol 39 ◽

pp. 542-543

Author(s):

D. E. Philpott ◽

W. Sapp ◽

C. Williams ◽

Joann Stevenson ◽

S. Black

Keyword(s):

Electron Microscopy ◽

Stem Cell ◽

Light Microscopy ◽

Dose Level ◽

Cross Sections ◽

Low Dose ◽

Light And Electron Microscopy ◽

Cellular Responses ◽

Post Irradiation ◽

X Irradiation

The response of spermatogonial cells to X-irradiation is well documented. It has been shown that there is a radiation resistent stem cell (As) which, after irradiation, replenishes the seminiferous epithelium. Most investigations in this area have dealt with radiation dosages of 100R or more. This study was undertaken to observe cellular responses at doses less than 100R of X-irradiation utilizing a system in which the tissue can be used for light and electron microscopy.Brown B6D2F1 mice aged 16 weeks were exposed to X-irradiation (225KeV; 15mA; filter 0.35 Cu; 50-60 R/min). Four mice were irradiated at each dose level between 1 and 100 rads. Testes were removed 3 days post-irradiation, fixed, and embedded. Sections were cut at 2 microns for light microscopy. After staining, surviving spermatogonia were identified and counted in tubule cross sections. The surviving fraction of spermatogonia compared to control, S/S0, was plotted against dose to give the curve shown in Fig. 1.

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Crystallographic Characterization of Dislocation Loops in Irradiated Tungsten

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101190 ◽

1968 ◽

Vol 26 ◽

pp. 290-291

Author(s):

Robert C. Rau

Keyword(s):

Electron Microscope ◽

Ambient Temperature ◽

Dislocation Loops ◽

Polycrystalline Specimen ◽

Post Irradiation ◽

Neutron Fluences

Previous work has shown that post-irradiation annealing, at temperatures near 1100°C, produces resolvable dislocation loops in tungsten irradiated to fast (E > 1 MeV) neutron fluences of about 4 x 1019 n/cm2 or greater. To crystallographically characterize these loops, tilting experiments were carried out in the electron microscope on a polycrystalline specimen which had been irradiated to 1.5 × 1021 n/cm2 at reactor ambient temperature (∼ 70°C), and subseouently annealed for 315 hours at 1100°C. This treatment produced large loops averaging 1000 Å in diameter, as shown in the micrographs of Fig. 1. The orientation of this grain was near (001), and tilting was carried out about axes near [100], [10] and [110].

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Deformation at interfaces of Ti-6Al-4V/SiC fiber composites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121193 ◽

1992 ◽

Vol 50 (1) ◽

pp. 158-159

Author(s):

Warren J. Moberly ◽

Daniel B. Miracle ◽

S. Krishnamurthy

Keyword(s):

Thermal Stresses ◽

Load Transfer ◽

Coefficient Of Thermal Expansion ◽

Hot Isostatic Pressing ◽

Matrix Composites ◽

Ongoing Research ◽

Aerospace Applications ◽

Sic Fiber ◽

The Matrix ◽

Intermetallic Matrix Composites

Titanium-aluminum alloy metal matrix composites (MMC) and Ti-Al intermetallic matrix composites (IMC), reinforced with continuous SCS6 SiC fibers are leading candidates for high temperature aerospace applications such as the National Aerospace Plane (NASP). The nature of deformation at fiber / matrix interfaces is characterized in this ongoing research. One major concern is the mismatch in coefficient of thermal expansion (CTE) between the Ti-based matrix and the SiC fiber. This can lead to thermal stresses upon cooling down from the temperature incurred during hot isostatic pressing (HIP), which are sufficient to cause yielding in the matrix, and/or lead to fatigue from the thermal cycling that will be incurred during application, A second concern is the load transfer, from fiber to matrix, that is required if/when fiber fracture occurs. In both cases the stresses in the matrix are most severe at the interlace.

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Low-temperature Mo-catalyzed growth of crystalline Si3N4 by CVD

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100150423 ◽

1993 ◽

Vol 51 ◽

pp. 918-919

Author(s):

K.L. More ◽

R.A. Lowden ◽

T.M. Besmann

Keyword(s):

Vapor Deposition ◽

Hot Isostatic Pressing ◽

Chemical Vapor ◽

Processing Method ◽

Crystalline Material ◽

Structural Ceramic ◽

Alternative Processing ◽

Strong Candidate ◽

Hot Pressing Sintering ◽

Processing Techniques

Silicon nitride possesses an attractive combination of thermo-mechanical properties which makes it a strong candidate material for many structural ceramic applications. Unfortunately, many of the conventional processing techniques used to produce Si3N4, such as hot-pressing, sintering, and hot-isostatic pressing, utilize significant amounts of densification aids (Y2O3, Al2O3, MgO, etc.) which ultimately lowers the utilization temperature to well below that of pure Si3N4 and also decreases the oxidation resistance. Chemical vapor deposition (CVD) is an alternative processing method for producing pure Si3N4. However, deposits made at temperatures less than ~1200°C are usually amorphous and at slightly higher temperatures, the deposition of crystalline material requires extremely low deposition rates (~5 μm/h). Niihara and Hirai deposited crystalline α-Si3N4 at 1400°C at a deposition rate of ~730 μm/h. Hirai and Hayashi successfully lowered the CVD temperature for the growth of crystalline Si3N4 by adding TiCl4 vapor to the SiCl4, NH3, and H2 reactants. This resulted in the growth of α-Si3N4 with small amounts of TiN at temperatures as low as 1250°C.

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The Concurrent Validity of the Minnesota Child Development Inventory as a Measure of Young Children's Language Development

Journal of Speech and Hearing Disorders ◽

10.1044/jshd.5401.101 ◽

1989 ◽

Vol 54 (1) ◽

pp. 101-105 ◽

Cited By ~ 19

Author(s):

J. Bruce Tomblin ◽

Cynthia M. Shonrock ◽

James C. Hardy

Keyword(s):

Child Development ◽

Language Development ◽

Expressive Language ◽

Strong Predictor ◽

Receptive Language ◽

Strongly Correlated ◽

Language Measure ◽

The Mean ◽

Child Development Inventory ◽

Mean Length Of Utterance

The extent to which the Minnesota Child Development Inventory (MCDI), could be used to estimate levels of language development in 2-year-old children was examined. Fifty-seven children between 23 and 28 months were given the Sequenced Inventory of Communication Development (SICD), and at the same time a parent completed the MCDI. In addition the mean length of utterance (MLU) was obtained for each child from a spontaneous speech sample. The MCDI Expressive Language scale was found to be a strong predictor of both the SICD Expressive scale and MLU. The MCDI Comprehension-Conceptual scale, presumably a receptive language measure, was moderately correlated with the SICD Receptive scale; however, it was also strongly correlated with the expressive measures. These results demonstrated that the Expressive Language scale of the MCDI was a valid predictor of expressive language for 2-year-old children. The MCDI Comprehension-Conceptual scale appeared to assess both receptive and expressive language, thus complicating its interpretation.

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