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Instruments / Technical Area	Publication Details	Published
I12-JEEP: Joint Engineering, Environmental and Processing	Effect of plasticity on creep deformation in type 316H stainless steel Abdullah Al Mamun , Chris Simpson , Tomiwa Erinosho , Dylan Agius , Christina Reinhard , Mahmoud Mostafavi , David Knowles ASME 2019 Pressure Vessels & Piping Conference DOI: 10.1115/PVP2019-93587 Diamond Proposal Number(s): [18836] Show Abstract ▼ Abstract: The creep life and deformation behaviour of high-temperature steels can be significantly affected by the prior plastic loading. This effect is partly due to the generation of intergranular strains from the grain-scale elastic and plastic anisotropic deformation during plastic loading. This paper investigates the effect of these plasticity generated intergranular strains on the subsequent creep strain accumulation behavior in type 316H stainless steel. An in-situ synchrotron diffraction experiment was conducted at 550°C, where the sample was loaded incrementally to different magnitudes of plastic strain, followed by a displacement-controlled stress relaxation dwell at each of this stage. The lattice strains of 4 grain families were measured during these stages. It was found that the intergranular strains generated during the plastic deformation significantly affect the relative magnitude of creep strain accumulation in different grain families. A subtle but significant difference has been observed between the creep intergranular strain accumulation behavior and the plastic intergranular strain accumulation behavior in different grain families which can be used to interrogate the validity of any micromechanical models’ formulation for creep and plastic deformation. The macroscopic stress relaxations measured from the experiment were compared with the prediction from a novel crystal plasticity based micromechanical model developed in our group. A good overall match was found between the experiment and the model regarding the magnitude of stress relaxation after various level of plasticity. The experiments have demonstrated that the model requires further development to accurately predict the rate of stress relaxation and the micro scale lattice strain evolution during creep.	Nov 2019
B18-Core EXAFS I11-High Resolution Powder Diffraction I12-JEEP: Joint Engineering, Environmental and Processing	Influence of microstructure on the corrosion of archaeological iron observed using 3D synchrotron micro-tomography H. J. Simon , G. Cibin , C. Reinhard , Y. Liu , E. Schofield , I. C. Freestone Corrosion Science DOI: 10.1016/j.corsci.2019.108132 Diamond Proposal Number(s): [16863, 16328] Show Abstract ▼ Abstract: A combination of X-ray analytical techniques has been used to study the microstructure and corrosion of a 450-year-old cast-iron cannonball fragment from the Mary Rose shipwreck. Using a 3D approach, it has been shown that akaganeite, β-FeO(OH, Cl), starts to appear ˜1.5 mm below the outer surface of the object, occurring selectively around non-contiguous graphite flakes in the microstructure, with no corrosion in graphite-free regions. This spatial analysis has given a new look inside a 450-year-old system, to see how metallographic features interact with local chemical environments to give complex corrosion products, centuries in the making.	Aug 2019
I12-JEEP: Joint Engineering, Environmental and Processing	Validating 3D two-parameter fracture mechanics models for structural integrity assessments C. A. Simpson , S. Tonge , T. Connolley , C. Reinhard , T. J. Marrow , M. Mostafavi Theoretical And Applied Fracture Mechanics 102281 DOI: 10.1016/j.tafmec.2019.102281 Diamond Proposal Number(s): [12606] Show Abstract ▼ Abstract: In-situ fracture tests were carried out on the I12 beamline at the Diamond Light Source. Four Al-Ti metal-matrix composites (MMCs), with two crack lengths, were studied to assess for the impact of in-plane constraint. Synchrotron X-ray computed tomography and synchrotron X-ray diffraction were used to measure total strain and elastic strain respectively. In this work, the measured elastic strains in the samples are detailed as a function of applied load and compared against those predicted from a 3D elastic-plastic finite element model. The modelled strains increased asymptotically towards the tip of the electro discharge machined notch. The experimental results do not highlight the same response, which is due to a combination of blunting and low experimental spatial resolution. Far field experimental and measured strain fields converged, notably in the test piece containing a long notch ( a/W = 0.5) and higher levels of constraint.	Jun 2019
I12-JEEP: Joint Engineering, Environmental and Processing	Effect of mixed salts on atmospheric corrosion of 304 stainless steel Liya Guo , Na Mi , Haval Mohammed-ali , Majid Ghahari , Andrew Du Plessis , Angus Cook , Steven Street , Christina Reinhard , Robert C. Atwood , Trevor Rayment , Alison J. Davenport Journal Of The Electrochemical Society 166, C3010 - C3014 DOI: 10.1149/2.0021911jes Diamond Proposal Number(s): [7412] Open Access Show Abstract ▼ Abstract: Atmospheric corrosion of stainless steel can take place when airborne salt particles deposit on the metal surface, forming droplets when the relative humidity (RH) reaches a critical value: the deliquescence relative humidity of the salt. Most work to date has focused on single salts such as MgCl2 or NaCl. In the present work, the effect of mixed salts is investigated at 45% RH, above the deliquescence relative humidity of MgCl2 but below that of NaCl. Dish-shaped pits were found in pure MgCl2 solutions and mixed solutions. Crevice corrosion takes place under NaCl crystals. This is shown both with ex situ measurements and in situ time-dependent measurements using X-ray microtomography, where pit growth was also monitored.	Jan 2019
I12-JEEP: Joint Engineering, Environmental and Processing	The effect of relative humidity change on atmospheric pitting corrosion of stainless steel 304L Liya Guo , Steven Street , Haval B. Mohammed-ali , Majid Ghahari , Na Mi , Sarah Glanvill , Andrew Du Plessis , Christina Reinhard , Trevor Rayment , Alison Davenport Corrosion Science DOI: 10.1016/j.corsci.2019.01.033 Diamond Proposal Number(s): [8334] Show Abstract ▼ Abstract: Relative humidity fluctuations tend to influence atmospheric corrosion under natural exposure conditions. In this study, the effect of change in relative humidity on pitting corrosion of stainless steel under MgCl2 droplets is investigated with in situ X-ray microtomography and optical microscopy. Relative humidity fluctuations (between 33% RH and 85% RH or between 33% RH and 12% RH) tend to lead to nucleation of many small pits whereas continuous exposure at constant 33% RH leads to growth of a single pit. This indicates that natural fluctuations in relative humidity might be beneficial for preventing the growth of a large penetrating pit.	Jan 2019
I12-JEEP: Joint Engineering, Environmental and Processing	Validating 3D two-parameter fracture mechanics for structural integrity assessments C. A. Simpson , S. Tonge , A. Cinar , C. Reinhard , T. J. Marrow , M. Mostafavi Procedia Structural Integrity 13, 965 - 970 DOI: 10.1016/j.prostr.2018.12.180 Diamond Proposal Number(s): [12606] Open Access Show Abstract ▼ Abstract: In-situ fracture tests were carried out on the I12 beamline at the Diamond Light Source. Four Al-Ti metal-matrix composites (MMCs), with varying combinations of thickness and crack length, were studied to assess for the impact of in-plane and out-of-plane constraint. Synchrotron X-ray computed tomography and synchrotron X-ray diffraction were used to measure total strain and elastic strain respectively. The total strain was calculated via digital volume correlation, with Ti particles within the MMC providing sufficient texture to track the internal displacement vectors in 3D. The total, elastic-plastic strain energy release rate, Jtotal was calculated from 2D slices extracted from the 3D displacement field, with Jtotal reaching a maximum value at the sample surface. It is, however, still unclear whether calculating Jtotal on a slice-by-slice basis provides an accurate representation of strain energy release rate across the crack front; techniques to evaluate the J-integral from the full 3D displacement field are being developed.	Dec 2018
I12-JEEP: Joint Engineering, Environmental and Processing	Measurements of stress during thermal shock in clad reactor pressure vessel material using time-resolved in-situ synchrotron x-ray diffraction Sam Oliver , Chris Simpson , Andrew James , Christina Reinhard , David Collins , Martyn Pavier , Mahmoud Mostafavi ASME 2018 Pressure Vessels and Piping Conference DOI: 10.1115/PVP2018-84676 Show Abstract ▼ Abstract: Nuclear reactor pressure vessels must be able to withstand thermal shock due to emergency cooling during a loss of coolant accident. Demonstrating structural integrity during thermal shock is difficult due to the complex interaction between thermal stress, residual stress, and stress caused by internal pressure. Finite element and analytic approaches exist to calculate the combined stress, but validation is limited. This study describes an experiment which aims to measure stress in a slice of clad reactor pressure vessel during thermal shock using time-resolved synchrotron X-ray diffraction. A test rig was designed to subject specimens to thermal shock, whilst simultaneously enabling synchrotron X-ray diffraction measurements of strain. The specimens were extracted from a block of SA508 Grade 4N reactor pressure vessel steel clad with Alloy 82 nickel-base alloy. Surface cracks were machined in the cladding. Electric heaters heat the specimens to 350°C and then the surface of the cladding is quenched in a bath of cold water, representing thermal shock. Six specimens were subjected to thermal shock on beamline I12 at Diamond Light Source, the UK’s national synchrotron X-ray facility. Time-resolved strain was measured during thermal shock at a single point close to the crack tip at a sample rate of 30 Hz. Hence, stress intensity factor vs time was calculated assuming K-controlled near-tip stress fields. This work describes the experimental method and presents some key results from a preliminary analysis of the data. Copyright © 2018 by ASME	Jul 2018
	In-situ synchrotron X-ray radiography observation of primary Al 2 Cu intermetallic growth on fragments of aluminium oxide film Feng Wang , Dmitry Eskin , Thomas Connolley , Chuangnan Wang , Billy Koe , Andrew King , Christina Reinhard , Jiawei Mi Materials Letters 213, 303 - 305 DOI: 10.1016/j.matlet.2017.11.090 Open Access Show Abstract ▼ Abstract: While using synchrotron X-ray radiography for studying ultrasonic melt processing, the growth of the primary Al2Cu intermetallic phase on fragments of aluminium oxide film during solidification of a hypereutectic Al-35% Cu alloy was observed in-situ and in real time with adequate spatial and temporal resolution. This provides the first direct evidence for the nucleation of a primary phase on oxide particles during solidification of real metallic alloys. Comparison of the primary Al2Cu intermetallics grown in the melt with and without fragments of aluminium oxide film reveals considerable refinement, which demonstrates that the enhanced nucleation of a primary phase on oxide particles promotes structure refinement.	Nov 2017
I12-JEEP: Joint Engineering, Environmental and Processing	The effect of long-term bisphosphonate therapy on trabecular bone strength and microcrack density A. Jin , J. Cobb , U. Hansen , R. Bhattacharya , C. Reinhard , N. Vo , R. Atwood , J. Li , A. Karunaratne , C. Wiles , R. Abel Bone And Joint Research 6, 602 - 609 DOI: 10.1302/2046-3758.610.BJR-2016-0321.R1 Diamond Proposal Number(s): [9811, 852] Open Access Show Abstract ▼ Abstract: Objectives Bisphosphonates (BP) are the first-line treatment for preventing fragility fractures. However, concern regarding their efficacy is growing because bisphosphonate is associated with over-suppression of remodelling and accumulation of microcracks. While dual-energy X-ray absorptiometry (DXA) scanning may show a gain in bone density, the impact of this class of drug on mechanical properties remains unclear. We therefore sought to quantify the mechanical strength of bone treated with BP (oral alendronate), and correlate data with the microarchitecture and density of microcracks in comparison with untreated controls. Methods Trabecular bone from hip fracture patients treated with BP (n = 10) was compared with naïve fractured (n = 14) and non-fractured controls (n = 6). Trabecular cores were synchrotron scanned and micro-CT scanned for microstructural analysis, including quantification of bone volume fraction, microarchitecture and microcracks. The specimens were then mechanically tested in compression. Results BP bone was 28% lower in strength than untreated hip fracture bone, and 48% lower in strength than non-fractured control bone (4.6 MPa vs 6.4 MPa vs 8.9 MPa). BP-treated bone had 24% more microcracks than naïve fractured bone and 51% more than non-fractured control (8.12/cm2 vs 6.55/cm2 vs 5.25/cm2). BP and naïve fracture bone exhibited similar trabecular microarchitecture, with significantly lower bone volume fraction and connectivity than non-fractured controls. Conclusion BP therapy had no detectable mechanical benefit in the specimens examined. Instead, its use was associated with substantially reduced bone strength. This low strength may be due to the greater accumulation of microcracks and a lack of any discernible improvement in bone volume or microarchitecture. This preliminary study suggests that the clinical impact of BP-induced microcrack accumulation may be significant.	Oct 2017
I12-JEEP: Joint Engineering, Environmental and Processing	Synchrotron X-ray characterisation of crack strain fields in polygranular graphite S. M. Barhli , L. Saucedo-mora , M. S. L. Jordan , A. F. Cinar , C. Reinhard , M. Mostafavi , T. J. Marrow Carbon DOI: 10.1016/j.carbon.2017.08.075 Diamond Proposal Number(s): [9478] Show Abstract ▼ Abstract: The strain field of a crack in polygranular isotropic nuclear graphite, a quasi-brittle material, has been studied during stable fracture propagation. Synchrotron X-ray computed tomography and strain mapping by diffraction were combined with digital volume correlation and phase congruency image analysis to extract the full field displacements and elastic crystal strains. The measured displacement fields have been analysed using a Finite Element method to extract the elastic strain energy release rate as a J-integral. Non-linear properties described the effect of microcracking on the elastic modulus in the fracture process zone. The analysis was verified by the good agreement of the predicted and measured elastic strain fields when using the non-linear model. The intrinsic critical elastic strain energy release rate for mode I crack propagation is approximately 200 J m−2.	Sep 2017

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