scholarly journals Grain kinematics during stress relaxation in sand: not a problem for X-ray imaging

2019 ◽  
Vol 92 ◽  
pp. 01001
Author(s):  
Jelke Dijkstra ◽  
Edward Andò ◽  
Christophe Dano
Keyword(s):  
Stress Relaxation ◽  
Axial Stress ◽  
Image Correlation ◽  
Natural Sand ◽  
Full Field ◽  
X Ray ◽  
X Ray Imaging ◽  
Unavoidable Stress ◽  
Soil Skeleton ◽  
The Rich

X-ray tomography is a very valuable tool for studying the full-field 3D deformation of granular materials. The requirement to stop loading and scan a given state (assumed to be stationary) used in most approaches implies unavoidable stress relaxation during scanning. Since scanning times on laboratory tomographs are normally in the order of 1 hour, the strength of the assumption of a stationary state cannot be tested, which introduces some potential weakness in the interpretation of the rich micro-mechanics observed. This paper presents the kinematics of relaxation of a dry natural sand in a typical oedometric cell used for X-ray scanning, using a synchrotron X-ray source to provide scanning times of around 3 minutes, at two different magnifications. This allows the relaxation of the cell & sand system for the first time to be quantified. Advanced image correlation tools are used to quantify the rearrangements of the soil skeleton during loading and the subsequent relaxation. The results indicate that the magnitude of grain displacements during relaxation, associated to ≈4% reduction in externally measured axial stress under oedometric loading, falls below 0:01D50. It can, therefore, be concluded that the relaxation step required prior to an X-ray scan during an in-situ geomechanical experiment on dry sand does not lead to appreciable uncertainties.

Design, development and first experiments on the X-ray imaging beamline at Indus-2 synchrotron source RRCAT, India

2015 ◽  
Vol 22 (6) ◽  
pp. 1531-1539 ◽  
Author(s):  
A. K. Agrawal ◽  
B. Singh ◽  
Y. S. Kashyap ◽  
M. Shukla ◽  
P. S. Sarkar ◽  
...  
Keyword(s):  
Phase Contrast ◽  
Imaging Techniques ◽  
Phase Contrast Imaging ◽  
Design Development ◽  
Contrast Imaging ◽  
Synchrotron Source ◽  
Full Field ◽  
X Ray ◽  
X Ray Imaging ◽  
Micro Tomography

A full-field hard X-ray imaging beamline (BL-4) was designed, developed, installed and commissioned recently at the Indus-2 synchrotron radiation source at RRCAT, Indore, India. The bending-magnet beamline is operated in monochromatic and white beam mode. A variety of imaging techniques are implemented such as high-resolution radiography, propagation- and analyzer-based phase contrast imaging, real-time imaging, absorption and phase contrast tomographyetc. First experiments on propagation-based phase contrast imaging and micro-tomography are reported.

scholarly journals Nondestructive Characterization of Ceramic Composites Used as Combustor Liners in Advanced Gas Turbines

1995 ◽  
Author(s):  
W. A. Ellingson ◽  
S. A. Rothermel ◽  
J. F. Simpson
Keyword(s):  
Gas Turbines ◽  
Thermal Characteristics ◽  
Ceramic Matrix Composites ◽  
Ceramic Composites ◽  
Matrix Composites ◽  
Full Field ◽  
X Ray ◽  
X Ray Imaging ◽  
Combustor Liner ◽  
Nondestructive Characterization

Nondestructive characterization (NDC) methods which can provide full field information about components prior to and during use are critical to the reliable application of continuous fiber ceramic matrix composites in high firing temperature (>1350°C) gas turbines. For combustor liner applications, although nonmechanical load bearing components, thermal characteristics as well as mechanical integrity is vitally important. NDC methods being developed to provide necessary information include x-ray computed tomography (mainly for through-wall density and delamination detection), infrared-based thermal diffusivity imaging, and single-wall through-transmission x-ray imaging (mainly for fiber content and alignment detection). Correlation of the data obtained from NDC methods with subscale combustor liner tests have shown positive results at thermal cycling temperatures from 700°C to 1177°C.

scholarly journals Highly porous nanoberyllium for X-ray beam speckle suppression

2015 ◽  
Vol 22 (3) ◽  
pp. 796-800 ◽  
Author(s):  
Alexander Goikhman ◽  
Ivan Lyatun ◽  
Petr Ershov ◽  
Irina Snigireva ◽  
Pawel Wojda ◽  
...  
Keyword(s):  
Spatial Coherence ◽  
Special Device ◽  
X Rays ◽  
Speckle Structure ◽  
Full Field ◽  
X Ray ◽  
X Ray Imaging ◽  
Phase Amplitude ◽  
Highly Porous ◽  
Effective Source

This paper reports a special device called a `speckle suppressor', which contains a highly porous nanoberyllium plate squeezed between two beryllium windows. The insertion of the speckle suppressor in an X-ray beam allows manipulation of the spatial coherence length, thus changing the effective source size and removing the undesirable speckle structure in X-ray imaging experiments almost without beam attenuation. The absorption of the nanoberyllium plate is below 1% for 1 mm thickness at 12 keV. The speckle suppressor was tested on the ID06 ESRF beamline with X-rays in the energy range from 9 to 15 keV. It was applied for the transformation of the phase–amplitude contrast to the pure amplitude contrast in full-field microscopy.

Nondestructive Characterization of Ceramic Composites Used as Combustor Liners in Advanced Gas Turbines

1996 ◽  
Vol 118 (3) ◽  
pp. 486-490
Author(s):  
W. A. Ellingson ◽  
S. A. Rothermel ◽  
J. F. Simpson
Keyword(s):  
Gas Turbines ◽  
Thermal Characteristics ◽  
Ceramic Matrix Composites ◽  
Ceramic Composites ◽  
Matrix Composites ◽  
Full Field ◽  
X Ray ◽  
X Ray Imaging ◽  
X Ray Computed ◽  
Nondestructive Characterization

Nondestructive characterization (NDC) methods, which can provide full-field information about components prior to and during use, are critical to the reliable application of continuous fiber ceramic matrix composites in high-firing-temperature (>1350°C) gas turbines. [For combustor liners, although they are nonmechanical load-bearing components, both thermal characteristics and mechanical integrity are vitally important.] NDC methods being developed to provide necessary information include x-ray computed tomography (mainly for through-wall density and delamination detection), infrared-based thermal diffusivity imaging, and single-wall through-transmission x-ray imaging (mainly for fiber content and alignment detection). Correlation of the data obtained from NDC methods with subscale combustor liner tests have shown positive results at thermal cycling temperatures from 700°C to 1177°C.

scholarly journals Multiscale X-ray imaging using ptychography

2018 ◽  
Vol 25 (4) ◽  
pp. 1214-1221 ◽  
Author(s):  
Simone Sala ◽  
Venkata S. C. Kuppili ◽  
Stefanos Chalkidis ◽  
Darren J. Batey ◽  
Xiaowen Shi ◽  
...  
Keyword(s):  
Generation X ◽  
Imaging Techniques ◽  
X Rays ◽  
Widespread Application ◽  
Full Field ◽  
X Ray ◽  
X Ray Imaging ◽  
Imaging Mode ◽  
Resolution Imaging ◽  
Complementary Techniques

The success of ptychography and other imaging experiments at third-generation X-ray sources is apparent from their increasingly widespread application and the improving quality of the images they produce both for resolution and contrast and in terms of relaxation of experimental constraints. The wider availability of highly coherent X-rays stimulates the development of several complementary techniques which have seen limited mutual integration in recent years. This paper presents a framework in which some of the established imaging techniques – with particular regard for ptychography – are flexibly applied to tackle the variable requirements occurring at typical synchrotron experiments. In such a framework one can obtain low-resolution images of whole samples and smoothly zoom in on specific regions of interest as they are revealed by switching to a higher-resolution imaging mode. The techniques involved range from full-field microscopy, to reach the widest fields of view (>mm), to ptychography, to achieve the highest resolution (<100 nm), and have been implemented at the I13 Coherence Branchline at Diamond Light Source.

Study of Mode I-II Mixed Crack Propagation in Electrofusion Joint of Polyethylene Pipe

2018 ◽  
Author(s):  
Yue Zhang ◽  
Jianfeng Shi ◽  
Jinyang Zheng
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Strain Distribution ◽  
Axial Stress ◽  
Propagation Direction ◽  
Image Correlation ◽  
J Integral ◽  
Full Field ◽  
Crack Propagation Direction ◽  
Finite Element Numerical Simulation

Electrofusion joint plays an important role in connecting polyethylene (PE) pipe. In our previous study, penetrating crack failure through the fitting with an angle of about 70° was observed, and axial stress was found to be an important factor in the crack propagation. In this paper, experiments were carried out to study the crack propagation phenomena of the electrofusion joint of PE pipe. Digital Image Correlation (DIC) method was used to measure the displacement on specimen’s surface, as well as full-field strain distribution, based on which the J-integral of the crack tip was calculated. Besides, a finite element numerical simulation was conducted, and its accuracy was verified by experimental J-integral value. Through combination of experimental observations and finite element method, the phenomenon that the angle between crack propagation direction and tube axial is about 70° is detailed analysed. By comparison and analysis of the testing results, critical J-integral value during crack propagation is determined. Furthermore, critical J-integral value of crack propagation in electrofusion joint is predicted.

Confocal full-field X-ray microscope for novel three-dimensional X-ray imaging

2009 ◽  
Vol 16 (5) ◽  
pp. 616-621 ◽  
Author(s):  
Akihisa Takeuchi ◽  
Yasuko Terada ◽  
Yoshio Suzuki ◽  
Kentaro Uesugi ◽  
Sadao Aoki
Keyword(s):  
Three Dimensional ◽  
Full Field ◽  
X Ray ◽  
X Ray Imaging
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