I12-JEEP: Joint Engineering, Environmental and Processing
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Open Access
Abstract: The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits).
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May 2016
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[9244]
Open Access
Abstract: Spiders are an important animal group, with a long history. Details of their origins remain limited, with little knowledge of their stem group, and no insights into the sequence of character acquisition during spider evolution. We describe a new fossil arachnid, Idmonarachne brasieri gen. et sp. nov. from the Late Carboniferous (Stephanian, ca 305–299 Ma) of Montceau-les-Mines, France. It is three-dimensionally preserved within a siderite concretion, allowing both laboratory- and synchrotron-based phase-contrast computed tomography reconstruction. The latter is a first for siderite-hosted fossils and has allowed us to investigate fine anatomical details. Although distinctly spider-like in habitus, this remarkable fossil lacks a key diagnostic character of Araneae: spinnerets on the underside of the opisthosoma. It also lacks a flagelliform telson found in the recently recognized, spider-related, Devonian–Permian Uraraneida. Cladistic analysis resolves our new fossil as sister group to the spiders: the spider stem-group comprises the uraraneids and I. brasieri. While we are unable to demonstrate the presence of spigots in this fossil, the recovered phylogeny suggests the earliest character to evolve on the spider stem-group is the secretion of silk. This would have been followed by the loss of a flagelliform telson, and then the ability to spin silk using spinnerets. This last innovation defines the true spiders, significantly post-dates the origins of silk, and may be a key to the group's success. The Montceau-les-Mines locality has previously yielded a mesothele spider (with spinnerets). Evidently, Late Palaeozoic spiders lived alongside Palaeozoic arachnid grades which approached the spider condition, but did not express the full suite of crown-group autapomorphies.
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Mar 2016
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I12-JEEP: Joint Engineering, Environmental and Processing
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Open Access
Abstract: Distortion correction or camera calibration for an imaging system
which is highly configurable and requires frequent disassembly for
maintenance or replacement of parts needs a speedy method for
recalibration. Here we present direct techniques for calculating distortion
parameters of a non-linear model based on the correct determination of the
center of distortion. These techniques are fast, very easy to implement, and
accurate at sub-pixel level. The implementation at the X-ray tomography
system of the I12 beamline, Diamond Light Source, which strictly requires
sub-pixel accuracy, shows excellent performance in the calibration image
and in the reconstructed images.
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Dec 2015
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[7338]
Abstract: To improve the manufacturing quality of welded structures, to prevent failures at weld joints and to predict their lifetime, measurements of the residual stresses generated by welding in the structures are extremely useful. The residual stresses may reduce the component life due to phenomena that occur at low applied stresses such as brittle fracture, fatigue and stress corrosion cracking. Welded thin Ti–6Al–4V panel components are commonly found in aero-engine assemblies and the weld integrity and reliability are critical. In this work, the residual stress distributions in a welded thin Ti–6Al–4V T-joint were measured by the newly developed SScanSS program with synchrotron X-ray diffraction technique. The measurement performed in this study, which included a large number of measurement points, has mapped a complete stress field in a thin sheet T-joint weld. It has not only provided improved understanding of residual stress in such a joint but also filled the missing link between the residual stress obtained by numerical modelling and their validation. The results have shown that the longitudinal stresses play the most important role in the residual stress distribution over the flange and high tensile stresses appear in the region near the weld zone. The measured results were compared with the numerically predicted results and these showed good agreement.
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Oct 2015
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I12-JEEP: Joint Engineering, Environmental and Processing
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Abstract: During solidification of metallic alloys, coalescence leads to the formation of solid bridges
between grains or grain clusters when both solid and liquid phases are percolated. As such, it
represents a key transition with respect to the mechanical behavior of solidifying alloys and to
the prediction of solidification cracking. Coalescence starts at the coherency point when the
grains begin to touch each other, but are unable to sustain any tensile loads. It ends up at
mechanical coherency when the solid phase is sufficiently coalesced to transmit macroscopic
tensile strains and stresses. Temperature at mechanical coherency is a major input parameter in
numerical modeling of solidification processes as it defines the point at which thermally induced
deformations start to generate internal stresses in a casting. This temperature has been determined
for Al-Zn alloys using in situ X-ray diffraction during casting in a dog-bone-shaped mold.
This setup allows the sample to build up internal stress naturally as its contraction is prevented.
The cooling on both extremities of the mold induces a hot spot at the middle of the sample
which is irradiated by X-ray. Diffraction patterns were recorded every 0.5 seconds using a
detector covering a 426 9 426 mm2 area. The change of diffraction angles allowed measuring
the general decrease of the lattice parameter of the fcc aluminum phase. At high solid volume
fraction, a succession of strain/stress build up and release is explained by the formation of hot
tears. Mechanical coherency temperatures, 829 K to 866 K (556 C to 593 C), and solid
volume fractions, ca. 98 pct, are shown to depend on solidification time for grain refined
Al-6.2 wt pct Zn alloys.
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Sep 2015
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I12-JEEP: Joint Engineering, Environmental and Processing
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Michael
Drakopoulos
,
Thomas
Connolley
,
Christina
Reinhard
,
Robert
Atwood
,
Oxana
Magdysyuk
,
Nghia
Vo
,
Mike
Hart
,
Leigh
Connor
,
Bob
Humphreys
,
George
Howell
,
Steve
Davies
,
Tim
Hill
,
Guy
Wilkin
,
Ulrik
Pedersen
,
Andrew
Foster
,
Nicoletta
De Maio
,
Mark
Basham
,
Fajin
Yuan
,
Kaz
Wanelik
Open Access
Abstract: I12 is the Joint Engineering, Environmental and Processing (JEEP) beamline,
constructed during Phase II of the Diamond Light Source. I12 is located on
a short (5 m) straight section of the Diamond storage ring and uses a 4.2 T
superconducting wiggler to provide polychromatic and monochromatic X-rays
in the energy range 50150 keV. The beam energy enables good penetration
through large or dense samples, combined with a large beam size (1 mrad
horizontally x 0.3 mrad vertically). The beam characteristics permit the study of
materials and processes inside environmental chambers without unacceptable
attenuation of the beam and without the need to use sample sizes which are
atypically small for the process under study. X-ray techniques available to users
are radiography, tomography, energy-dispersive diffraction, monochromatic
and white-beam two-dimensional diffraction/scattering and small-angle X-ray
scattering. Since commencing operations in November 2009, I12 has established
a broad user community in materials science and processing, chemical
processing, biomedical engineering, civil engineering, environmental science,
palaeontology and physics.
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May 2015
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I12-JEEP: Joint Engineering, Environmental and Processing
I13-2-Diamond Manchester Imaging
I18-Microfocus Spectroscopy
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Open Access
Abstract: Tomographic datasets collected at synchrotrons are becoming very large and complex, and, therefore, need to be managed efficiently. Raw images may have high pixel counts, and each pixel can be multidimensional and associated with additional data such as those derived from spectroscopy. In time-resolved studies, hundreds of tomographic datasets can be collected in sequence, yielding terabytes of data. Users of tomographic beamlines are drawn from various scientific disciplines, and many are keen to use tomographic reconstruction software that does not require a deep understanding of reconstruction principles. We have developed Savu, a reconstruction pipeline that enables users to rapidly reconstruct data to consistently create high-quality results. Savu is designed to work in an 'orthogonal' fashion, meaning that data can be converted between projection and sinogram space throughout the processing workflow as required. The Savu pipeline is modular and allows processing strategies to be optimized for users' purposes. In addition to the reconstruction algorithms themselves, it can include modules for identification of experimental problems, artefact correction, general image processing and data quality assessment. Savu is open source, open licensed and 'facility-independent': it can run on standard cluster infrastructure at any institution.
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May 2015
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I12-JEEP: Joint Engineering, Environmental and Processing
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Fiona
Strobridge
,
Bernardo
Orvananos
,
Mark
Croft
,
Hui-chia
Yu
,
Rosa
Robert
,
Hao
Liu
,
Zhong
Zhong
,
Thomas
Connolley
,
Michael
Drakopoulos
,
Katsuyo
Thornton
,
Clare P.
Grey
Diamond Proposal Number(s):
[8385]
Open Access
Abstract: Nanosized, carbon-coated LiFePO4 (LFP) is a promising
cathode for Li-ion batteries. However, nano-particles are problematic for
electrode design, optimized electrodes requiring high tap densities, good
electronic wiring, and a low tortuosity for efficient Li diffusion in the
electrolyte in between the solid particles, conditions that are difficult to
achieve simultaneously. Using in situ energy-dispersive X-ray diffraction,
we map the evolution of the inhomogeneous electrochemical reaction in
LFP-electrodes. On the first cycle, the dynamics are limited by Li
diffusion in the electrolyte at a cycle rate of C/7. On the second cycle,
there appear to be two rate-limiting processes: Li diffusion in the
electrolyte and electronic conductivity through the electrode. Three-dimensional modeling based on porous electrode theory
shows that this change in dynamics can be reproduced by reducing the electronic conductivity of the composite electrode by a
factor of 8 compared to the first cycle. The poorer electronic wiring could result from the expansion and contraction of the
particles upon cycling and/or the formation of a solid-electrolyte interphase layer. A lag was also observed perpendicular to the
direction of the current: the LFP particles at the edges of the cathode reacted preferentially to those in the middle, owing to the
closer proximity to the electrolyte source. Simulations show that, at low charge rates, the reaction becomes more uniformly
distributed across the electrode as the porosity or the width of the particle-size distribution is increased. However, at higher rates,
the reaction becomes less uniform and independent of the particle-size distribution.
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Apr 2015
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I12-JEEP: Joint Engineering, Environmental and Processing
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Open Access
Abstract: High-throughput processing of parallel-beam X-ray tomography at synchrotron facilities is lacking a reliable and robust method to determine the center of rotation in an automated fashion, i.e. without the need for a human scorer. Well-known techniques based on center of mass calculation, image registration, or reconstruction evaluation work well under favourable conditions but they fail in cases
where samples are larger than field of view, when the projections show low signal-to-noise, or when optical defects dominate the contrast. Here we propose an alternative technique which is based on the Fourier analysis of the sinogram. Our technique shows excellent performance particularly on challenging data.
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Jul 2014
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I12-JEEP: Joint Engineering, Environmental and Processing
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X.
Song
,
M.
Xie
,
F.
Hofmann
,
T.
Illston
,
T.
Connolley
,
C.
Reinhard
,
R.
Atwood
,
L.
Connor
,
M.
Drakopoulos
,
L.
Frampton
,
Alexander
Korsunsky
Diamond Proposal Number(s):
[6974, 7016]
Abstract: In the present study, residual stresses in the Powder Bed Direct Laser Deposition (PB DLD) built parts were investigated using X-ray diffraction strain measurement and finite element simulation. The microstructure and texture of the DLD built parts were studied, indicating that the vertically elongated grains have preferred orientation of (001)-type pointing in the growth direction in the nickel superalloy C263. A conceptual model of residual stress generation was proposed using fictitious thermal expansion based on the argument that residual stresses arise from strain incompatibility that is “frozen in” within the work piece during fabrication.
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Jan 2014
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