I12-JEEP: Joint Engineering, Environmental and Processing
|
Diamond Proposal Number(s):
[20611]
Open Access
Abstract: Metallic alloys coalesce via extremely rapid melting and subsequent solidification to form fusion welded joints. The melt pool evolution in melting and solidification sequences during the welding process determines the formation of the final weld joint shape, microstructure and defects. The scientific insight on weld pool evolution and related phenomena can be a key contribution to enhance structural integrity and resilience of the welded structures or components. However, inherent complexity with multi-physics phenomena, associated high temperatures and the rapidness of the processes make direct experimental investigation of welding is extremely demanding. Thus, internal flow behaviour during welding or other melt-pool-based metal processing such as additive manufacturing remains unclear and hinders progression to process optimisation. In this contribution we report the observation of melt pool dynamics that take place during electric arc welding, obtained through in situ synchrotron imaging at millisecond scale. The analysis flow patterns along with the quantified weld pool surface dynamics revealed us to how different contributing forces dictate the flow conditions over the distinct durations of the relatively short existence of the liquid phase. Our preliminary results suggest the existence of arc, surface tension and gravity dominant regimes during the evaluation of the weld pool. Further, we present our observations on how different welding parameters influence these regimes and develop into different transient conditions.
|
May 2020
|
|
B16-Test Beamline
I12-JEEP: Joint Engineering, Environmental and Processing
|
Diamond Proposal Number(s):
[20611, 19595]
Open Access
Abstract: The flow within the melt pool during welding is a major factor that dictates the formation of the final fusion zone shape, solidification microstructure and defects. In this paper, we report the evolution sequence of the arc weld pool flow that observed via fast in-situ synchrotron X-ray imaging. Varying flow regimes attribute to the dominance of characteristic forces within the weld pool during rapid solid-liquid-solid phase transformation. Our analysis indicates the general sequence in the arc, surface tension and gravity driven force domination. Welding process parameters appear to influence significantly in determining the domination interval and the intensity of individual force. In some instances, arc and surface tension driven forces can prevent pores, which causes porosity in final welded structures, escaping from the melt pool. Preliminary relations between power input levels, diffract force domination regimes, flow patterns and pool surface changes in fusion welds are suggested by considering the behavior of multiple weld pools.
|
Feb 2020
|
|
B22-Multimode InfraRed imaging And Microspectroscopy
I11-High Resolution Powder Diffraction
I12-JEEP: Joint Engineering, Environmental and Processing
|
Harry G. W.
Godfrey
,
Lydia
Briggs
,
Xue
Han
,
William J. F.
Trenholme
,
Christopher
Morris
,
Mathew
Savage
,
Louis
Kimberley
,
Oxana
Magdysyuk
,
Michael
Drakopoulos
,
Claire A.
Murray
,
Chiu C.
Tang
,
Mark D.
Frogley
,
Gianfelice
Cinque
,
Sihai
Yang
,
Martin
Schroeder
Diamond Proposal Number(s):
[11278]
Open Access
Abstract: Understanding the mechanism of assembly and function of metal-organic frameworks (MOFs) is important for the development of practical materials. Herein, we report a time-resolved diffraction analysis of the kinetics of formation of a robust MOF, MFM-300(Fe), which shows high adsorption capacity for CO2 (9.55 mmol g−1 at 293 K and 20 bar). Applying the Avrami-Erofe’ev and the two-step kinetic Finke-Watzky models to in situ high-energy synchrotron X-ray powder diffraction data obtained during the synthesis of MFM-300(Fe) enables determination of the overall activation energy of formation (50.9 kJ mol−1), the average energy of nucleation (56.7 kJ mol−1), and the average energy of autocatalytic growth (50.7 kJ mol−1). The synthesis of MFM-300(Fe) has been scaled up 1000-fold, enabling the successful breakthrough separations of the CO2/N2 mixture in a packed-bed with a selectivity for CO2/N2 of 21.6. This study gives an overall understanding for the intrinsic behaviors of this MOF system, and we have determined directly the binding domains and dynamics for adsorbed CO2 molecules within the pores of MFM-300(Fe).
|
Nov 2019
|
|
I12-JEEP: Joint Engineering, Environmental and Processing
|
Open Access
Abstract: X-Ray parallel-beam micro-tomography systems at synchrotron facilities are mainly bespoke designs. Technical problems from a detector system can strongly affect the quality of reconstruction results. Radial lens distortion in the visible light optics causes streak artifacts which get stronger towards the edge of the image. The irregular response of the detector gives rise to a variety of stripe artifacts in the sonogram; full stripes, partial stripes, fluctuating stripes, and unresponsive stripes. These give rise to ring artifacts of different kinds in the reconstructed image. The scattering of the scintillation photons can cause artifacts which are similar to beam hardening artifacts and reduce the resolution of the image. Here we present our practical approaches to tackle each such problem. These approaches are easy to implement and have low computational cost. The algorithms are freely available as open-source software.
|
Sep 2019
|
|
I12-JEEP: Joint Engineering, Environmental and Processing
Optics
|
Diamond Proposal Number(s):
[14033]
Open Access
Abstract: High energy X-ray phase contrast tomography is tremendously beneficial to the study of thick and dense materials with poor attenuation contrast. Recently, the X-ray speckle-based imaging technique has attracted widespread interest because multimodal contrast images can now be retrieved simultaneously using an inexpensive wavefront modulator and a less stringent experimental setup. However, it is time-consuming to perform high resolution phase tomography with the conventional step-scan mode because the accumulated time overhead severely limits the speed of data acquisition for each projection. Although phase information can be extracted from a single speckle image, the spatial resolution is deteriorated due to the use of a large correlation window to track the speckle displacement. Here we report a fast data acquisition strategy utilising a fly-scan mode for near field X-ray speckle-based phase tomography. Compared to the existing step-scan scheme, the data acquisition time can be significantly reduced by more than one order of magnitude without compromising spatial resolution. Furthermore, we have extended the proposed speckle-based fly-scan phase tomography into the previously challenging high X-ray energy region (120 keV). This development opens up opportunities for a wide range of applications where exposure time and radiation dose are critical.
|
Jun 2019
|
|
I12-JEEP: Joint Engineering, Environmental and Processing
|
Ramzi
Al-agele
,
Emily
Paul
,
Sophie
Taylor
,
Charlotte
Watson
,
Craig
Sturrock
,
Michael
Drakopoulos
,
Robert C.
Atwood
,
Catrin S.
Rutland
,
Nicola
Menzies-gow
,
Edd
Knowles
,
Jonathan
Elliott
,
Patricia
Harris
,
Cyril
Rauch
Open Access
Abstract: Global inequalities in economic access and agriculture productivity imply that a large number of developing countries rely on working equids for transport/agriculture/mining. Therefore, the understanding of hoof conditions/shape variations affecting equids' ability to work is still a persistent concern. To bridge this gap, using a multi-scale interdisciplinary approach, we provide a bio-physical model predicting the shape of equids’ hooves as a function of physical and biological parameters. In particular, we show (i) where the hoof growth stress originates from, (ii) why the hoof growth rate is one order of magnitude higher than the proliferation rate of epithelial cells and (iii) how the soft-to-hard transformation of the epithelium is possible allowing the hoof to fulfil its function as a weight-bearing element. Finally (iv), we demonstrate that the reason for hoof misshaping is linked to the asymmetrical design of equids' feet (shorter quarters/long toe) together with the inability of the biological growth stress to compensate for such an asymmetry. Consequently, the hoof can adopt a dorsal curvature and become ‘dished’ overtime, which is a function of the animal's mass and the hoof growth rate. This approach allows us to discuss the potential occurrence of this multifaceted pathology in equids.
|
Jun 2019
|
|
I12-JEEP: Joint Engineering, Environmental and Processing
|
Diamond Proposal Number(s):
[7858]
Open Access
Abstract: Residual stress/strain and microstructure used in additively manufactured material are strongly dependent on process parameter combination. With the aim to better understand and correlate process parameters used in electron beam melting (EBM) of Ti-6Al-4V with resulting phase distributions and residual stress/strains, extensive experimental work has been performed. A large number of polycrystalline Ti-6Al-4V specimens were produced with different optimized EBM process parameter combinations. These specimens were post-sequentially studied by using high-energy X-ray and neutron diffraction. In addition, visible light microscopy, scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) studies were performed and linked to the other findings. Results show that the influence of scan speed and offset focus on resulting residual strain in a fully dense sample was not significant. In contrast to some previous literature, a uniform α- and β-Ti phase distribution was found in all investigated specimens. Furthermore, no strong strain variations along the build direction with respect to the deposition were found. The magnitude of strain in α and β phase show some variations both in the build plane and along the build direction, which seemed to correlate with the size of the primary β grains. However, no relation was found between measured residual strains in α and β phase. Large primary β grains and texture appear to have a strong effect on X-ray based stress results with relatively small beam size, therefore it is suggested to use a large beam for representative bulk measurements and also to consider the prior β grain size in experimental planning, as well as for mathematical modelling.
|
Feb 2019
|
|
Electrical Engineering
Mechanical Engineering
|
Open Access
Abstract: I12 is a high-energy imaging, diffraction and scattering beamline at Diamond. Its source is a superconducting wiggler with a power of approximately 9kW at 500 mA after the fixed front-end aperture; two permanent filters aim at reducing the power in photons below the operating range of the beamline of 50-150 keV, which accounts for about two-thirds of the total*. This paper focuses on the design and simulation process of the secondary permanent filter, a 4mm thick SiC disk. The first version of the filter was vulnerable to cracking due to thermally induced stress, so a new filter based on an innovative concept was proposed: a water-cooled shaft rotates, via a ceramic interface, the SiC disk; the disk operates up to 900 degrees C, and a copper absorber surrounding the filter dissipates the heat through radiation. We utilised analysis data following failure of an initial prototype to successfully model the heat flow using FEA. This model informed different iterations of the re-design of the assembly, addressing the issues identified. The operational temperature of the final product matches within a few degrees C the one predicted by the simulation.
|
Dec 2018
|
|
I12-JEEP: Joint Engineering, Environmental and Processing
|
Lee
Aucott
,
Hongbiao
Dong
,
Wajira
Mirihanage
,
Robert
Atwood
,
Anton
Kidess
,
Shian
Gao
,
Shuwen
Wen
,
John
Marsden
,
Shuo
Feng
,
Mingming
Tong
,
Thomas
Connolley
,
Michael
Drakopoulos
,
Chris R.
Kleijn
,
Ian M.
Richardson
,
David J.
Browne
,
Ragnvald H.
Mathiesen
,
Helen
Atkinson
Diamond Proposal Number(s):
[8218, 7855]
Open Access
Abstract: Internal flow behaviour during melt-pool-based metal manufacturing remains unclear and
hinders progression to process optimisation. In this contribution, we present direct timeresolved
imaging of melt pool flow dynamics from a high-energy synchrotron radiation
experiment. We track internal flow streams during arc welding of steel and measure
instantaneous flow velocities ranging from 0.1ms−1 to 0.5ms−1. When the temperaturedependent
surface tension coefficient is negative, bulk turbulence is the main flow
mechanism and the critical velocity for surface turbulence is below the limits identified in
previous theoretical studies. When the alloy exhibits a positive temperature-dependent
surface tension coefficient, surface turbulence occurs and derisory oxides can be entrapped
within the subsequent solid as result of higher flow velocities. The widely used arc welding and the emerging arc additive manufacturing routes can be optimised by controlling internal
melt flow through adjusting surface active elements.
|
Dec 2018
|
|
I12-JEEP: Joint Engineering, Environmental and Processing
|
Open Access
Abstract: Synchrotron-based X-ray micro-tomography systems often suffer severe ring artifacts in reconstructed images. In sinograms the artifacts appear as straight lines or stripe artifacts. These artifacts are caused by the irregular response of a detecting system giving rise to a variety of observed types of stripes: full stripes, partial stripes, fluctuating stripes, and unresponsive stripes. The use of pre-processing techniques such as distortion correction or phase retrieval blurs and enlarges these stripes. It is impossible for a single approach to remove all types of stripe artifacts. Here, we propose three techniques for tackling all of them. The proposed techniques are easy to implement; do not generate extra stripe artifacts and void-center artifacts; and give superior quality on challenging data sets and in comparison with other techniques. Implementations in Python and a challenging data set are available for download.
|
Oct 2018
|
|
