Professor James Marrow
Tel: 07540 722660 (mobile)
Tel: +44 1865 273938 (Room 110.10.18)
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My research is focussed on the degradation of structural materials and the role of microstructure. A significant proportion of this work is related to materials utilised in the nuclear industry. This work was been funded by organisations including EPSRC, Rolls-Royce, British Energy, EdF, the Health and Safety Executive (Nuclear Installations Inspectorate), Ministry of Defence and the Nuclear Decommissioning Authority. A key aspect is the investigation of fundamental mechanisms of damage accumulation using novel materials characterisation techniques. This has concentrated recently on computed X-ray tomography and strain mapping by digital image correlation, which I apply to studies of the degradation of Generation IV nuclear materials such as graphite and silicon carbide composites.
The next generation of nuclear power systems must be demonstrably safer, proliferation resistant and efficient. They will not provide power for some decades to come. Their development requires new high temperature fuels and structural materials with resistance to irradiation. This can only be achieved through fundamental understanding of materials microstructure and the mechanisms of materials ageing.
Research in engineering materials for energy generation is not a quick-fix topic. New materials take from 15-20 years to come into service, and then are expected to be in service for 40-80 years. The key physical mechanisms that determine manufactured performance, and how these properties age in service, are not very well understood, and mistakes in materials selection can have enormous financial and social implications.
Prediction is a major challenge, and deep understanding of the fundamental mechanisms of materials aging is essential to identify and avoid potential "cliff-edges" in future materials performance.
Advanced 2D and 3D Digital Image Correlation the Full Field Displacements of Cracks and Defects
Selim Barhli, Prof. James Marrow, Dr Mahmoud Mostafavi (Bristol), Dr Dave Hollis (LaVision)
The aim of the project is to develop improved digital image and volume correlation algorithms for the detection and quantitative analysis of crack-like defects in engineering materials under complex modes of loading. The objectives are to; develop and evaluate methods for the detection of crack-like discontinuities by digital image correlation, using synthetic data for 2D displacement fields generated by finite element models or analytical solutions and applied to artificial speckle pattern images; investigate the effects of image quality (i.e. noise) on crack detection in synthetic data, applying methods such as pattern-recognition and image-filtering; develop and evaluate methods to optimise the measurement of the displacement fields associated with longer cracks under different states of stress, using masking and iterative approaches based on the measured strain gradients in synthetic data; extend the developed two-dimensional methods to three-dimensional synthetic data and apply the developed algorithms and methods to the experimental characterisation of damage in brittle, quasi-brittle and ductile materials. This will include model brittle materials, optimised for DIC and DVC, and real engineering materials such as concretes, ceramic-matrix composites and structural metals under different states of loading. Existing data are being used, together with new data obtained in this project. The project is supported by and in collaboration with LaVision Ltd.
Stress concentration behaviour in radiolytic-oxidised graphite
Matthew Jordan, Prof. James Marrow, Prof. David Nowell
This industrial CASE EPSRC studentship PhD project, supported by EDF Energy, aims to understand the effects of stress concentrations, such as keyway roots, on the fracture strength of radiolytic-oxidised nuclear graphite components. Its objective is a notch-sensitivity strength test, using a sharp corner, which could be used on specimens of radiolyically-oxidised graphite, machined from the small samples extracted from reactor cores. A modelling framework for component and specimen strength will be developed, calibrated by small specimen tests, such as those used to monitor graphite material properties. It is supported by a program of tests to investigate the effects of specimen size on notch sensitivity, in particular the validity of data obtained from tests on small, notched specimens, in a range of quasi-brittle model materials. Particular use is made of computed synchrotron X-ray tomography and digital volume correlation to measure the deformation at the notch tip.
Microstructure-based modelling of crack nucleation and growth in nuclear graphite
Dr Yelena Vertyagina, Prof. James Marrow
This project, funded by EDF Energy, aims to improve confidence in the prediction of the fracture strength of radiolytically-oxided graphite components in advanced gas-cooled reactors (AGR) from small specimen test data. This will be done through the development of a microstructure-representative fracture model for polygranular graphite, which addresses interactions between microstructure heterogeneity, strain state and crack development and accounts for the effects of fast neutron irradiation and radiolytic oxidation. The objective is to obtain an improved strength criterion for crack initiation, and determine whether this supports the conservatism of the maximum principle stress criterion currently used in the EDF brick cracking models. The model will be validated by comparison with experimental data from virgin and fast neutron irradiated radiolytically-oxidised graphite. It will be applied to predict the fracture behaviour of fast neutron irradiated radiolytically-oxidised polygranular nuclear graphite at stress concentrations, addressing in particular the influence of microstructure heterogeneity on strength variability and the extent of stable crack extension prior to unstable fracture. The specific objectives are to: Obtain experimental observations to define the criteria for short crack propagation in virgin nuclear graphite (and suitable heterogeneous model materials), in three-dimensions and two-dimensions, under different states of loading. Develop a model framework to predict the onset of crack nucleation, stable crack propagation and unstable fracture in a heterogeneous microstructure. Use available experimental data on the elastic properties, flexural strength and work of fracture of fast neutron irradiated, radiolytically oxidised polygranular nuclear graphite to understand their effects on mean strength and data scatter (i.e. statistics of strength) and hence predict the fracture behaviour of radiolytically oxidised polygranular nuclear graphite in a wider range of conditions. Predict the fracture behaviour of fast neutron irradiated, radiolytically oxidised polygranular nuclear graphite at stress concentrations, addressing in particular the influence of microstructure heterogeneity on the extent of stable crack extension prior to unstable fracture and the statistics of strength. To date, Cellular Automata models have been developed to obtain computationally efficient descriptions of the fracture behaviour of representative porous volumes. These are now being integrated into the CA-FE models that are being developed in the EPSRC-funded QUBE project.
QUBE: QUasi-Brittle fracture: a 3D Experimentally-validated approach
Dr Luis Saucedo Mora, Prof. James Marrow
By improving basic understanding of damage mechanisms, we aim to create a framework to predict fracture behaviour and strength of quasi-brittle materials, validated by unique experimental observations of damage development at the microstructural scale. The challenge of different length-scales will be overcome by protocols for large-scale cellular automata finite element simulations of damage from high fidelity, three-dimensional descriptions of microstructure and damage mechanisms. The project is aimed at the integrity of quasi-brittle materials, particularly those used in the nuclear energy sector, such as nuclear graphite. The project is funded by EPSRC (EP/J019992/1), with partners including the University of Bristol, University of Manchester, EDF, Amec, ONR, Magnox and Arup. This is the first systematic research to bridge the gap between experimental advances in observation and computational modelling of damage and fracture in complex materials. Three-dimensional nonlinear fracture modelling methods will be physically validated for the first time. The development and integration of a series of numerical models and methods; 3D cohesive fracture modelling, representation of random heterogeneity, generation of 3D FE meshes from tomography, Monte Carlo simulations and multiscale modelling represent major advances in theories and applications of computational mechanics. It will provide a powerful tool for fracture modelling of structures of quasi-brittle materials and an innovative method for their reliability assessment. In the work at Oxford, a Cellular Automata Finite Element approach has been developed that can simulate damage development with high microstructural fidelity in large models. Significant use is also made of synchrotron X-ray computed tomography and diffraction to characterise the strains and stresses within the fracture process zone, as a validation of the modelling.
Three-dimensional characterization and multi-scale modelling of damage in natural biomaterials
Liye Yan, Prof. James Marrow
Benefiting from complicated morphological geometries and hierarchal microstructures, biomaterials such as shell, bone and enamel present a good combination of stiffness, strength and toughness, which are unmatched by their engineering counterparts such as nacre-like laminated composites. As a consequence, biomaterials’ mechanical behaviours, especially their resistance to crack initiation and propagation under bending or compression, have been extensively studied for a wide range of applications in biological, medical and engineering fields. Furthermore, factors that influence these mechanical properties have also been studied to improve the design of new biomimetic materials. In this project, mechanical testing will be done to obtain the basic mechanical properties of biomaterials. In particular, in-situ mechanical testing will be conducted during high resolution X-ray tomography. The reconstructed images will be analysed using digital volume correlation to obtain the full displacement field. Image-based finite element models will be solved for the prediction of mechanical response of biomaterials under loading and the input parameters will be tuned to match the experimental results. By studying the materials under different states of loading, the mechanical properties of the materials will be obtained. The scientific aspects of the project lie on: 1) Use different image-modelling techniques to build a finite element model to achieve more reliable and accurate prediction of damage developed in biomaterials under bending and compression in order to design biomimetic engineering materials, which are stiff but damage tolerant, and biocompatible materials, which are used in clinic field. 2) Image-based modelling techniques allow the incorporation of hierarchical structures of biomaterials into models, which facilitates the investigation of structure-related issues including the structural changes of microstructures in response to different temperatures and environmental changes.
Validation of Three-Dimensional Fracture Mechanics Methods under Mixed Mode Loading
Matthew Molteno (visitor), Dr Thorsten Becker (Stellenbosch University, RSA), Prof. James Marrow
This project is funded by the South African National Research Foundation (NRF) to improve the capabilities for the characterizing cracking in energy materials used in power stations. The research is linked to the EPPEI materials science specialization which has identified damage accumulation as a key South African research concern. Crack behavior is greatly influenced by the geometry and stress state of the surrounding material. In multi-axial stress states or complex crack geometries, fracture resistance should be considered in three separate modes for crack path and failure prediction. In such cases, full-field experimental deformations are typically obtained from the material surface with digital image correlation; however, the majority of cracking is subsurface and complex. The aim of this project is to develop and experimentally validate techniques to measure the fracture resistance of materials along three-dimensional curved crack fronts and multi-axial stress states. To achieve precise geometries, curved crack fronts are approximated with electrical discharge machined notches. Strain maps have been obtained using in-situ X-ray computed tomography and digital volume correlation. The method focuses on the J-integral approach to obtain three-dimensional fracture parameters locally along the curved crack front. Results are decomposed into Mode I-III parts and compared with finite element models, and other fracture mechanics approaches. These methods will be applied to nuclear graphite to better understand its crack front behavior and fracture resistance. The project is being conducted by Matt Molteno, visiting Oxford from Stellenbosch University http://www0.sun.ac.za/mateng/
3D multi-scale characterization and modelling of damage in ceramic matrix composites
Shixiang Zhao, Prof. James Marrow
SiC/SiC ceramic matrix composites are a promising materials for high temperature structural components in the nuclear power generation, such as accident tolerant fuel cladding. Such components must safely operate in a severe environment. Nuclear grade SiC/SiC composites are therefore optimized for strength and damage tolerance, and have a relatively complex microstructure. In order to understand of the fracture behaviour of such microstructures, particularly in after exposure to harsh environments, different modes of loading are applied to small test specimens. Materials models are required to interpret these tests and to optimise component and microstructure design. This project is using high resolution X-ray tomography and the digital volume correlation to study crack development in situ, which enables 3D insight into the mechanical behaviour. The experimental data will further support the development of the materials-based modelling for the structural design, such as the FEMME model. This multi-scale model takes into account the detailed microstructure and is able to simulate the complex fracture behaviour. This project is linked to the European 7th Framework programme MatISSE (Materials' Innovations for Safe and Sustainable nuclear) (http://www.fp7-matisse.eu)
An innovative, multi-scale, real-time approach to the understanding of deformation and fracture in irradiated nuclear reactor core graphites
Dr Dong Liu (EPSRC Postdoctoral Research Fellow), hosted by Professor James Marrow
The primary material of interest for this project is nuclear graphite. Nuclear graphite current serves as a neutron moderator and structural core component in the 14 operation UK Advanced Gas-cooled Reactors, and it is also a candidate material for future reactor designs such as Very High Temperature Reactors worldwide. In the irradiating and high temperature environment, nuclear graphite degrades in its microstructure, physical and mechanical properties. This project makes use of a range of cutting-edge techniques to investigate the deformation and fracture of nuclear graphites in the extreme environments. These are challenging experiments that require access to national and international large facilities (ENGIN-X, Rutherford Appleton Laboratory; ALS, Lawrence Berkeley Laboratory). In general, micro-mechanical testing on micro-metre miniature specimens prepared by focussed ion beam milling, high temperature in situ neutron diffraction combined with high temperature digital image correlation, high temperature in situ x-ray computed tomography with digital volume correlation, high temperature in situ Raman spectroscopy, and in situ electro-thermal mechanical testing combined with infrared imaging/pyrometry are adopted to characterise the deformation and fracture over multiple length-scales from nano-metre (lattice) up to centimetre range. These outcome will feed into microstructure-based computer models to forward predict the bulk behaviour and integrity of graphite components subjected to longer service. In addition to nuclear graphite, this project studies a range of other nuclear and energy materials such as MAX phase ceramics with combined properties from ceramics and metals at high temperature for the application of neutron resistant components and porous nanomaterial-based catalysts in solid oxide fuel cells, porous ceramic thermal barrier coatings for the application of turbine blades, SiC composites for high temperature nuclear applications, and the mechanical integrity of GaN-diamond based electronic devices.
Short Crack Propagation in an Anisotropic Polycrystalline Metal
Phil Earp, Prof. James Marrow, Prof. Alan Cocks
This project aims to investigate the criteria for crack formation in polycrystalline 𝛼-uranium. It is thought that the interaction between microstructural features such as twins and grain boundaries cause stress concentrations that lead to fracture initiation. Experimental work will involve characterising the strain fields in the material as it deforms, locating the regions of high stress, and characterising the form of this stress concentration and how the material accommodates it. 3-dimensional characterisation of the uranium microstructure will be achieved using serial-sectioning Electron Backscatter Diffraction (EBSD). The criteria for crack initiation and propagation will be investigated in tensile test experiments. Two-camera Digital Image Correlation (DIC) will be used to characterise the deformation of the material and identify areas of strain localisation. High-Resolution EBSD will be used to investigate the local strain field around features of interest such as slip bands or twins where they are blocked by a grain boundary. Along with measurements of grain orientations, this will be used to assess the strength of grain boundaries and the criteria for grain boundary failure. The objective is to relate the observed microstructural features to the sites of fracture initiation, to be able to identify microstructures that may be more susceptible to failure.
9 public active projects
Summary of publications on ORCID
L. Saucedo-Mora and T. J. Marrow, Multi-scale damage modelling in a ceramic matrix composite using a finite-element microstructure meshfree methodology, Philos. Trans. R. Soc. London A Math. Phys. Eng. Sci. 374, (2016). doi: 10.1098/rsta.2015.0276
S. Rahimi, K. Mehrez, and T. J. Marrow, Effect of surface machining on intergranular stress corrosion cracking (IGSCC) in sensitised type 304 austenitic stainless steel, Corros. Eng. Sci. Technol. 0, 1 (2016). doi: 10.1080/1478422X.2015.1122295
Zou C, Marrow TJ, Reinhard C, Li B, Zhang C, Wang S. Porosity characterization of fiber-reinforced ceramic matrix composite using synchrotron X-ray computed tomography. Journal of Instrumentation 2016;11:C03052. doi:10.1088/1748-0221/11/03/C03052.
D. Khoshkhou, M. Mostafavi, C. Reinhard, M.P. Taylor, D.S. Rickerby, I.M. Edmonds, Evans, H.E., Marrow, T.J., Connolly, B.J., Three-dimensional displacement mapping of diffused Pt thermal barrier coatings via synchrotron X-ray computed tomography and digital volume correlation, Scr. Mater. 115 (2016) 100–103. doi:10.1016/j.scriptamat.2015.10.033.
C.N. Morrison, A.P. Jivkov, Y. Vertyagina, T.J. Marrow, Multi-scale modelling of nuclear graphite tensile strength using the site-bond lattice model, Carbon N. Y. 100 (2016) 273–282. doi:10.1016/j.carbon.2015.12.100.
Saucedo-Mora, L., Mostafavi, M., Khoshkhou, D., Reinhard, C., Atwood, R., Shuang, Z., Connolly, B., Marrow, T.J., Observation and simulation of indentation damage in a SiC–SiCfibre ceramic matrix composite. Finite Elements in Analysis and Design 110, 11–19 (2016).
Sláme?ka, K. Skalka, P., ?elko, L., Pokluda, J., Saucedo-Mora, L., Marrow, T. J., Thandavamoorthy, U. Plasma-sprayed thermal barrier coatings: Numerical study on damage localization and evolution. Frattura ed Integrita Strutturale 10, 322–329 (2016).
Cai, B., Lee, P. D., Karagadde, S., Marrow, T. J. & Connolley, T. Time-resolved synchrotron tomographic quantification of deformation during indentation of an equiaxed semi-solid granular alloy. Acta Materialia 105, 338–346 (2016).
Marrow, T. J. Liu, D. Barhli, S.M. Saucedo-Mora, L Vertyagina, Y. Collins, D.M. Reinhard, C. Kabra, S. Flewitt, P.E.J. Smith, D.J. In situ measurement of the strains within a mechanically loaded polygranular graphite. Carbon 96 (2016) 285-302 doi: 10.1016/j.carbon.2015.09.058
Liu, D., Mostafavi, M., Marrow, T. J., Smith, D. J. & Flewitt, P. E. J. Cruciform biaxial flexural testing of polygranular nuclear graphite. in 23rd Conference on Structural Mechanics in Reactor Technology (2015).
Jordan, M. S. L., Saucedo-Mora, L., Barhli, S. M., Nowell, D. & Marrow, T. J. Measurements of Stress Concentration Behaviour in AGR Nuclear Graphite. in 23rd Conference on Structural Mechanics in Reactor Technology (2015).
Marrow, T. J., Jordan, M. S. L. & Vertyagina, Y. Towards a notch-sensitivity strength test for irradiated nuclear graphite structural integrity. in The 4th EDF Energy Nuclear Graphite Symposium. Engineering Challenges Associated with the Life of Graphite Reactor Cores (Flewitt, P. E. J. & Wickham, A. J.) 247–259 (EMAS Publishing, 2014).
Vertyagina, Y. & Marrow, T. J. 3D Cellular Automata Fracture Model for Porous Graphite Microstructures. in 23rd Conference on Structural Mechanics in Reactor Technology (2015).
Saucedo-Mora L, Marrow TJ. Method for the explicit insertion of microstructure in Cellular Automata Finite Element (CAFE) models based on an irregular tetrahedral Finite Element mesh: Application in a multi-scale Finite Element Microstructure MEshfree framework (FEMME). Finite Elem Anal Des 2015;105:56–62. doi:10.1016/j.finel.2015.07.001.
Cai, B., Karagadde, S., Marrow, T. J., Connolley, T. & Lee, P. D. Synchrotron X-ray Tomographic Quantification of Deformation Induced Strain Localisation in Semi-solid Al- 15wt.%Cu. IOP Conference Series: Materials Science and Engineering 84, 012079 (2015). doi: 10.1088/1757-899X/84/1/012079
Saucedo-Mora L, Marrow TJ. FEMME : a multi-scale Finite Element Microstructure MEshfree fracture model for quasi-brittle materials with complex microstructures . Eng Fract Mech 2015;in press. doi:10.1016/j.engfracmech.2015.05.059.
Saucedo-Mora L, Sláme?ka K, Thandavamoorthy U, Marrow TJ. Multi-scale modeling of damage development in a thermal barrier coating. Surf Coatings Technol 2015;276:399–407. doi:10.1016/j.surfcoat.2015.06.038.
Cai, B., Karagadde, S., Rowley, D., Marrow, T. J., Connolley, T., & Lee, P. D. (2015). Time-resolved synchrotron tomographic quantification of deformation-induced flow in a semi-solid equiaxed dendritic Al–Cu alloy. Scripta Materialia, 103, 69–72. doi:10.1016/j.scriptamat.2015.03.011
Lyon, K. N., Marrow, T. J., & Lyon, S. B. (2015). Influence of milling on the development of stress corrosion cracks in austenitic stainless steel. Journal of Materials Processing Technology, 218, 32–37. doi:10.1016/j.jmatprotec.2014.11.038
Mostafavi, M., Collins, D. M., Cai, B., Bradley, R., Atwood, R. C., Reinhard, C., … Marrow, T. J. (2015). Yield behavior beneath hardness indentations in ductile metals, measured by three-dimensional computed X-ray tomography and digital volume correlation. Acta Materialia, 82, 468–482. doi:10.1016/j.actamat.2014.08.046
Marrow, J., Reinhard, C., Vertyagina, Y., Saucedo-Mora, L., Collins, D., & Mostafavi, M. (2014). 3D Studies of Damage by Combined X-ray Tomography and Digital Volume Correlation. In Procedia Materials Science (Vol. 3, pp. 1554–1559). doi:10.1016/j.mspro.2014.06.251
Saucedo-Mora, L., & Marrow, T. J. (2014). 3D Cellular Automata Finite Element Method with Explicit Microstructure: Modeling Quasi-brittle Fracture using Meshfree Damage Propagation. In Procedia Materials Science (Vol. 3, pp. 1143–1148). doi:10.1016/j.mspro.2014.06.186
Cai, B., Karagadde, S., Yuan, L., Marrow, T. J., Connolley, T., & Lee, P. D. (2014). In situ synchrotron tomographic quantification of granular and intragranular deformation during semi-solid compression of an equiaxed dendritic Al–Cu alloy. Acta Materialia, 76, 371–380. doi:10.1016/j.actamat.2014.05.035
Marrow, T. J., Mostafavi, M., Hashimoto, T., & Thompson, G. E. (2014). A quantitative three-dimensional in situ study of a short fatigue crack in a magnesium alloy. International Journal of Fatigue, 66, 183–193. doi:10.1016/j.ijfatigue.2014.04.003
Stratulat, A., Duff, J., & James Marrow, T. (2014). Grain boundary structure and intergranular stress corrosion crack initiation in high temperature water of a thermally sensitised austenitic stainless steel, observed in situ. Corrosion Science, 85, 428–435. doi:10.1016/j.corsci.2014.04.050
Vertyagina, Y., Mostafavi, M., Reinhard, C., Atwood, R., & Marrow, T. J. (2014). In situ quantitative three-dimensional characterisation of sub-indentation cracking in polycrystalline alumina. Journal of the European Ceramic Society, 34(12), 3127–3232. doi:10.1016/j.jeurceramsoc.2014.04.002
Gonzalez, D., King, A., Mostafavi, M., Reischig, P., du Roscoat, S. R., Ludwig, W., … Marrow, T. J. (2013). Three-dimensional observation and image-based modelling of thermal strains in polycrystalline alumina. Acta Materialia, 61(20), 7521–7533. doi:http://dx.doi.org/10.1016/j.actamat.2013.06.005
Mostafavi, M., Vertyagina, Y., Reinhard, C., Bradley, R., Jiang Xia, Galano, M. and Marrow, J., (2014), 3D studies of indentation by combined X-ray tomography and digital volume correlation, Key Engineering Materials, 592-593, 14-23, http://dx.doi.org/10.4028/www.scientific.net/KEM.592-593.14
Saucedo, L., Mostafavi, M., Khoshkhou, D., Reinhard, C., Atwood, R., Zhao, S., … Marrow, T. J. (2013). 3D cellular automata finite element (CAFE) modelling and experimental observation of damage in quasi-brittle nuclear materials: Indentation of a SiC-SiCfibre ceramic matrix composite. In SMINS-3. Idaho Falls, USA: OECD-NEA. www.oecd-nea.org/science/smins3/
Mostafavi, M., Baimpas, N., Tarleton, E., Atwood, R. C., McDonald, S. A., Korsunsky, A. M., & Marrow, T. J. (2013). Three dimensional crack observation, quantification and simulation in a quasi-brittle material. Acta Materialia, 61(16), 6276–6289. doi:http://dx.doi.org/10.1016/j.actamat.2013.07.011
BAIMPAS, N., XIE, M., SONG, X., HOFMANN, F., ABBEY, B., MARROW, J., … KORSUNSKY, A. M. (2013). RICH TOMOGRAPHY TECHNIQUES FOR THE ANALYSIS OF MICROSTRUCTURE AND DEFORMATION. International Journal of Computational Methods, (2), 1343006. doi:10.1142/S0219876213430068
Yang, Z., Ren, W., Mostafavi, M., Mcdonald, S. A., & Marrow, T. J. (2013). Characterisation of 3d fracture evolution in concrete using in-situ X-ray computed tomography testing and digital volume correlation. In Proceedings of the 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures, FraMCoS 2013 (pp. 236–242).
Mostafavi, M., McDonald, S.A., Çetinel, H., Mummery, P.M., Marrow, T.J.Flexural strength and defect behaviour of polygranular graphite under different states of stress, (2013) Carbon, 59, pp. 325-336. 10.1016/j.carbon.2013.03.025
Marrow T.J. and Tomkins B., The role of UK structural integrity research in the European fast neutron reactor programme, TAGSI/FESI Symposium: Structural Integrity of Nuclear Power Plant - learning from history and looking to the future, TWI Abingdon, April 2013
Lasithiotakis, M., Marsden, B. J., & Marrow, T. J. (2013). Annealing of ion irradiation damage in nuclear graphite. Journal of Nuclear Materials, 434(1-3), 334–346. doi:10.1016/j.jnucmat.2012.12.001
Mostafavi, M., McDonald, S. A., Mummery, P. M., & Marrow, T. J. Observation and quantification of three-dimensional crack propagation in poly-granular graphite. Engineering Fracture Mechanics, (2013). doi:10.1016/j.engfracmech.2012.11.023
Aswad, M. A., & Marrow, T. J. (2012). Intergranular crack nuclei in polycrystalline alumina. Engineering Fracture Mechanics, 95, 29–36. doi:10.1016/j.engfracmech.2012.08.005
Becker, T. H., Mostafavi, M., Tait, R. B., & Marrow, T. J. (2012). An approach to calculate the J-integral by digital image correlation displacement field measurement. Fatigue and Fracture of Engineering Materials and Structures, 35 ( 10 ) pp. 971 - 984
Duff, J. A., & Marrow, T. J. (2012). In situ observation of short fatigue crack propagation in oxygenated water at elevated temperature and pressure. Corrosion Science, 68(3), 34–43. doi:10.1016/j.corsci.2012.10.030
Kovac, J. ., Marrow, T. J. ., Govekar, E. ., & Legat, A. . (2012). Detection and characterisation of intergranular stress-corrosion cracking on austenitic stainless steel. Materials and Corrosion, 63(8), 664–673.
Marrow, T. J., Mostafavi, M., Macdonald, S., & Mummery, P. M. (2012). Observation and quantification of three-dimensional crack propagation in poly-granular graphite. 19th European Conference on Fracture, ECF19. Kazan, Russia.
Mostafavi, M. ., Schmidt, M. J. J. ., Marsden, B. J. ., & Marrow, T. J. . (2012). Fracture behaviour of an anisotropic polygranular graphite (PGA). Materials Science and Engineering A, 558, 265–277.
S Rahimi, T J Marrow (2012) Effects of orientation, stress and exposure time on short intergranular stress corrosion crack behaviour in sensitised type 304 austenitic stainless steel, 359-373. In Fatigue and Fracture of Engineering Materials and Structures 35 (4).
M Mostafavi, T J Marrow (2012) Quantitative in situ study of short crack propagation in polygranular graphite by digital image correlation, 695-707. In Fatigue and Fracture of Engineering Materials and Structures 35 (8).
M Herbig, A King, P Reischig et al. (2011) 3-D growth of a short fatigue crack within a polycrystalline microstructure studied using combined diffraction and phase-contrast X-ray tomography, 590-601. In Acta Materialia 59 (2).
L Babout, M Janaszewski, T J Marrow et al. (2011) A method for the 3-D quantification of bridging ligaments during crack propagation, 131-134. In Scripta Materialia 65 (2).
S Rahimi, D L Engelberg, T J Marrow (2011) A new approach for DL-EPR testing of thermo-mechanically processed austenitic stainless steel, 4213-4222. In Corrosion Science 53 (12).
T H Becker, T J Marrow, R B Tait (2011) An Evaluation of the Double Torsion Technique, 1511-1526. In Experimental Mechanics 51 (9).
T H Becker, T J Marrow, R B Tait (2011) Damage, crack growth and fracture characteristics of nuclear grade graphite using the Double Torsion technique, 32-43. In Journal of Nuclear Materials 414 (1).
A King, W Ludwig, D Engelberg et al. (2011) Diffraction contrast tomography for the study of polycrystalline stainless steel microstructures and stress corrosion cracking, 47-50. In Revue de Metallurgie. Cahiers D'Informations Techniques 108 (1).
M Mostafavi, T J Marrow (2011) In situ observation of crack nuclei in poly-granular graphite under ring-on-ring equi-biaxial and flexural loading, 1756-1770. In Engineering Fracture Mechanics 78 (8).
A King, W Ludwig, M Herbig et al. (2011) Three-dimensional in situ observations of short fatigue crack growth in magnesium, 6761-6771. In Acta Materialia 59 (17).
W. Ludwig, A. King, M. Herbig, P. Reischig, L. Babout, H. Proudhon, E.M. Lauridsen, Marrow, T J La microstructure 3D des materiaux polycristallins vue sous la lumiere synchrotron. L’Actualit ?e Chimique 62–67 (2011).
T.H. Becker, M. Mostafavi, R.B. Tait, T.J. Marrow, An Approach to Calculate the J-Integral by Digital Image Correlation Displacement Field Measurement, Fatigue and Fracture of Engineering Materials and Structures, accepted for publication 2012
M. Lasithiotakis, B.J. Marsden, T.J. Marrow, Application of an independent parallel reactions model on the annealing kinetics of BEPO irradiated graphite, J. Nuclear Materials, Volume 427, Issues 1–3, August 2012, Pages 95–109
Babout, L. ; Janaszewski, M. ; Bakavos, D. ; McDonald, S.A. ; Prangnell, P.B. ; Marrow, T.J. ; Withers, P.J.3D inspection of fabrication and degradation processes from X-ray (micro) tomography images using a hole closing algorithm, Imaging Systems and Techniques (IST), 2010 IEEE International Conference on 1-2 July 2010
M Mostafavi and TJ Marrow, Quantitative in situ study of short crack propagation in polygranular graphite by digital image correlation, Fatigue and Fracture of Engineering Materials and Structures (2012) DOI: 10.1111/j.1460-2695.2012.01648.x, In press.
M Herbig, J Marrow, J-Y Buffiere, A King, W Ludwig, H Proudhon, P Reischig, N Stevens, A Khan, E Lauridsen, A new dimension in short fatigue crack characterisation, ESRF Highlights 2011, Structure of Materials, pp 31-32
M. Mostafavi and T.J. Marrow, In situ observation of crack nuclei in poly-granular graphite under ring-on-ring equi-biaxial and flexural loading, Engineering Fracture Mechanics, Volume 78, Issue 8, May 2011, Pages 1756-1770
S. Al Shahrani, T. J, Marrow, Influence of Twins on Short Fatigue Cracks in Type 316L Stainless Steel, Key Engineering Materials (2011), 465, 507
Herbig, M , King, A., Reischig, P, Proudhon, H., Lauridsen, E.M, Marrow, J, Buffiere, J.-Y., Ludwig, W., 3-D growth of a short fatigue crack within a polycrystalline microstructure studied using combined diffraction and phase-contrast X-ray tomography, Acta Materialia Volume 59, Issue 2, January 2011, Pages 590-601
King, A., Ludwig, W., Engelberg, D., Marrow, T.J., Diffraction contrast tomography for the study of polycrystalline stainless steel microstructures and stress corrosion cracking, Revue de Metallurgie. Cahiers D'Informations Techniques, Volume 108, Issue 1, January 2011, Pages 47-50
King, A., Ludwig, W., Herbig, M., Buffiere, J.-Y., Khan, A.A., Stevens, N., Marrow, T.J. Three-dimensional in situ observations of short fatigue crack growth in magnesium, Acta Materialia, Volume 59, Issue 17, October 2011, Pages 6761-6771
S. Rahimi and T. J. Marrow, Effects of orientation, stress and exposure time on short intergranular stress corrosion crack behaviour in sensitised type 304 austenitic stainless steel, Fatigue Fract Engng Mater Struct, 2012, 35,359–373
S. Rahimi, D.L. Engelberg, T.J. Marrow, A New Approach for DL-EPR Testing of Thermo-Mechanically Processed Austenitic Stainless Steel, Corrosion Science, Volume 53, Issue 12, December 2011, Pages 4213-4222
T.H. Becker, T.J. Marrow, R.B. Tait, An Evaluation of the Double Torsion Technique, Experimental Mechanics, DOI 10.1007/s11340-011-9468-1, Experimental Mechanics, 51 (9) pp. 1511-1526.
A. Hodgkins, T. J. Marrow, M. R. Wootton, R. Moskovic and P. E. J. Flewitt, Fracture behaviour of radiolytically oxidised reactor core graphites: a view, Materials Science and Technology, Volume 26, Number 8, August 2010 , pp. 899-907(9)
T. Hashimoto, X. Zhou, C. Luo, K. Kawano, G.E. Thompson, A.E. Hughes, P. Skeldon, P.J. Withers, T.J. Marrow and A.H. Sherry, Nanotomography for understanding materials degradation, Scripta Materialia, Volume 63, Issue 8, October 2010, Pages 835-838
T.H. Becker, T.J. Marrow, R.B. Tait, Damage, crack growth and fracture characteristics of nuclear grade graphite using the Double Torsion technique, J Nucl. Mater, Volume 414, Issue 1, 1 July 2011, Pages 32-43
T. Hashimoto, X. Zhou, C. Luo, K. Kawano, G.E. Thompson, A.E. Hughes, P. Skeldon, P.J. Withers, T.J. Marrow and A.H. Sherry, Nanotomography for understanding materials degradation, Scripta Materialia, Volume 63, Issue 8, October 2010, Pages 835-838
J. Kovac, C. Alaux, T.J. Marrow, E. Govekar, A Legat, Correlations of electrochemical noise, acoustic emission and complementary monitoring techniques during intergranular stress-corrosion cracking of austenitic stainless steel, Corrosion Science 52 (2010) 2015–2025.
King A., Herbig M., Ludwig W., Reischig P., Lauridsen E.M., Marrow T., Buffiere J.Y. - Non-destructive analysis of micro texture and grain boundary character from X-ray diffraction contrast tomography, Nuclear Instruments and Methods in Physics Research B 268, 291-296 (2010)
A, King, N. Schell, R.V. Martins, F. Beckmann, H-U Ruhnau, R, Kiehn, J. Marrow, W. Ludwig, A Schreyer, Grain tracking at the high energy materials science beamline of the Petra III synchrotron radiation source, Materials Science Forum, 652, (2010), pp70-73
W. Ludwig, P. Reischig, A. King, M. Herbig, E.M. Lauridsen, T.J. Marrow, J.Y. Buffière, 3D grain mapping by X-ray diffraction contrast tomography and the use of Friedel pairs in diffraction data analysis, Review of Scientific Instruments, 80, 033905 (2009)
S. Rahimi, D Engelberg and T.J. Marrow, Characterisation of Grain Boundary Cluster Compactness in an Austenitic Stainless Steel (2010), Materials Science and Technology, Volume 26, Number 6, pp. 670-675
R. Jones, V. Randle, D. Engelberg, T.J. Marrow, Five-parameter grain boundary analysis of a grain boundary-engineered austenitic stainless steel, Journal of Microscopy, Volume 233, Number 3, March 2009 , pp. 417-422(6)
A. King, M. Herbig, W. Ludwig, P. Reischig, E.M. Lauridsen, T. Marrow, J.Y. Buffière, Non-destructive analysis of micro texture and grain boundary character from X-ray diffraction contrast tomography (2009), Nuclear Instruments and Methods in Physics Research B 268 (2010) 291–296
W. Ludwig, A. King, P. Reischig, M. Herbig, E.M. Lauridsen, S. Schmidt, H. Proudhon, S. Forest, P. Cloetens, S. Rolland du Roscoat, J.Y. Bufï¬ï¿½ère, T. Marrow, H.F. Poulsen, New opportunities for 3D materials science of polycrystalline materials at the micrometre lengthscale by combined use of X-ray diffraction and X-ray imaging (2009), Materials Science and Engineering A, Materials Science and Engineering A 524, 69-76 (2009)
A. King, G. Johnson, D. Engelberg, W. Ludwig and J. Marrow. Observations of intergranular stress corrosion cracking in a grain-mapped polycrystal (2008) Science, 321 (5887), pp. 382-385.
L. Babout, B.J. Marsden, P.M. Mummery and T.J. Marrow. Three-dimensional characterization and thermal property modelling of thermally oxidized nuclear graphite, (2008) Acta Materialia, 56 (16), pp. 4242-4254.
D.L. Engelberg, R.C. Newman and T.J. Marrow. Effect of thermomechanical process history on grain boundary control in an austenitic stainless steel (2008) Scripta Materialia, 59 (5), pp. 554-557.
S. Rahimi, D.L. Engelberg, J.A. Duff and T.J. Marrow. In-situ Observation of Intergranular Crack Nucleation in a Grain Boundary Controlled Austenitic Stainless Steel, (2009) Journal of Microscopy, (233), pp. 423–431
C. Berre, S.L. Fok, P.M. Mummery, J. Ali, B.J. Marsden, T.J. Marrow, G.B. Neighbour, Failure analysis of the effects of porosity in thermally oxidised nuclear graphite using finite element modelling, (2008) Journal of Nuclear Materials, 381, (1-2), pp 1-8.
A.N. Jones, G.N. Hall, M. Joyce, A. Hodgkins, K. Wen, T.J. Marrow, B.J. Marsden, Microstructural characterisation of nuclear grade graphite, (2008) Journal of Nuclear Materials, 381, (1-2), pp 152-157.
L. Lin, H. Li, A.S.L. Fok, M. Joyce, J. Marrow, Characterization of heterogeneity and nonlinearity in material properties of nuclear graphite using an inverse method, (2008) Journal of Nuclear Materials, 381, (1-2), pp 158-164.
K. Wen, J. Marrow and B. Marsden. Microcracks in nuclear graphite and highly oriented pyrolytic graphite (HOPG) (2008) Journal of Nuclear Materials, 381, (1-2), pp 199-203.
M.R. Joyce and T.J. Marrow. Microstructural scale strain localisation in nuclear graphite (2008) Journal of Nuclear Materials, 381, (1-2), pp 171-176.
M. Lasithiotakis, B. Marsden, J. Marrow and A. Willets. Application of an independent parallel reactions model on the annealing kinetics to irradiated graphite waste (2008) Journal of Nuclear Materials, 381, (1-2), pp 83-91.
C. Berre, S.L. Fok, B.J. Marsden, P.M. Mummery, T.J. Marrow and G.B. Neighbour. Microstructural modelling of nuclear graphite using multi-phase models (2008) Journal of Nuclear Materials, 380, (1-3), pp 46-58.
M.R. Joyce, T.J. Marrow, P. Mummery and B.J. Marsden. Observation of microstructure deformation and damage in nuclear graphite (2008) Engineering Fracture Mechanics, 75 (12), pp. 3633-3645.
M. Kuroda and T.J. Marrow. (2008) Modeling the effects of surface finish on fatigue limit in austenitic stainless steels, Fatigue and Fracture of Engineering Materials and Structures, Vol. 31 (7), pp. 581-598.
M. Kuroda and T.J. Marrow. Preparation of fatigue specimens with controlled surface characteristics (2008) Journal of Materials Processing Technology, 203 (1-3), pp. 396-403.
D.L. Engelberg, F.J. Humphreys and T.J. Marrow. The influence of low-strain thermo-mechanical processing on grain boundary network characteristics in type 304 austenitic stainless steel (2008) Journal of Microscopy, 230 (3), pp. 435-444.
G. Johnson, A. King, M.G. Honnicke, J. Marrow and W. Ludwig. X-ray diffraction contrast tomography: A novel technique for three-dimensional grain mapping of polycrystals. II. The combined case (2008) Journal of Applied Crystallography, 41 (2), pp. 310-318.
O.M. Alyousif, D.L Engelberg and T.J. Marrow. Surface grain boundary engineering of shot-peened type 304 stainless steel (2008) Journal of Materials Science, 43 (4), pp. 1270-1277.
L. Shi, H. Li, Z. Zou, A.S.L. Fok, B.J. Marsden, A Hodgkins, P.M. Mummery and J. Marrow. Analysis of crack propagation in nuclear graphite using three-point bending of sandwiched specimens (2008) Journal of Nuclear Materials, 372 (2-3), pp. 141-151.
K.Y. Wen, T.J. Marrow and B.J Marsden. The microstructure of nuclear graphite binders (2008) Carbon, 46 (1), pp. 62-71.
A.P. Jivkov and T.J. Marrow. Rates of intergranular environment assisted cracking in three-dimensional model microstructures (2007) Theoretical and Applied Fracture Mechanics, 48 (3), pp. 187-202.
***“Experimental validation of Inter-granular stress corrosion cracking (IGSCC) predictive models”
Supervisors: Prof Sergio Lozano-Perez , Prof James Marrow (Oxford), Dr Fabio Scenini (Manchester)
Stress Corrosion Cracking (SCC) is a very important mode of failure in nuclear reactors. A lot of effort from the scientific community has been dedicated to develop more accurate predictive models for crack initiation and propagation. EDF has produced one of the most comprehensive models to date and this project aims to validate it through direct characterization. We aim to produce a fully comprehensive benchmark dataset that allows a better validation and optimization of IGSCC models. For this purpose, we will test a nickel alloy in simulated reactor conditions (autoclave) and fully characterize the resultant stress corrosion cracks.
The student will be based in Oxford and work in close collaboration with EDF and the University of Manchester. Frequent trips to both institutions are expected. He/she will be in charge of sample design and preparation for autoclave testing in Manchester and characterization including EBSD, FIB, 3D tomography, DIC and TEM in Oxford and Manchester.
Candidates are expected to hold a first class or strong upper second class degree (or equivalent international qualifications), as a minimum, in Chemistry, Materials Science, Physics, Engineering or a related science subject. A Master’s degree in a related discipline is also desirable.
Candidates are recommended to apply as soon as possible as applications will be considered on an individual basis as and when they are received and this position will be filled as soon as possible, but the latest date for considering applications will be 31 July 2016.
Subject to contract this project will be supported by a 3.5 year studentship sponsored by the Materials Ageing Institute (MAI) and EDF. This studentship will provide full fees and maintenance for a student classified as home fee status (this includes an EU student who has spent the immediate previous three years, or more, in the UK undertaking undergraduate study) or EU fee status. Further information on the availability of funding can be obtained from Marion Beckett, firstname.lastname@example.org. The stipend will be at least £17,296 per year.
Students classified as overseas fee status are eligible for this funded project, but would have to provide the difference between home/EU and overseas student fees from some other source such as a scholarship or personal funds. For students who commence their studies in October 2016 this difference is expected to be in the region of £46,000 over three years. Please see http://www.ox.ac.uk/admissions/graduate/fees-and-funding for a statement of the actual fees.
Any questions concerning the project can be addressed to Professor Sergio Lozano-Perez (email@example.com). You can also visit his group website: http://www.ox.ac.uk/admissions/postgraduate_courses/apply/index.html
The Effect of Microstructure on Strength and Fracture Resistance of Nuclear Graphite
James Marrow, David Nowell (Engineering)
The project is concerned with the role of significant defects, such as single or collections of large pores, on sub-critical and critical crack propagation in polygranular nuclear graphite, which is used as a moderator and structural component in the UK Advanced Gas Cooled Reactors, and also in some designs of Generation IV advanced high temperature reactors.
The aim is to experimentally validate a key aspect of the microstructure modelling of short crack propagation in nuclear graphite: the role of significant defects such as single or collections of large pores. Advantage will be taken of new facilities in Oxford (high resolution X-ray computed tomography) and methods for in situ study of three-dimensional deformation and damage (e.g. digital volume correlation). The work will be done using non-irradiated graphite, but the methodology developed will be suitable for active studies in due course.
The project's objectives are to observe the propagation of sub-critical cracks from significant defects in virgin graphite, test developed microstructure-sensitive models of sub-critical crack propagation, simulate the effect of the effects of microstructure on the statistics of strength and fracture resistance of virgin graphite and improve the modelling of sub-critical crack propagation in reactor components.
This project is in collaboration with EDF Energy Generation.
Also see homepages: James Marrow
Mechanisms for the control of fatigue resistance of advanced lightweight nano-composites
James Marrow, Marina Galano, Fernando Audebert
This project is concerned with the role of microstructure in the fatigue resistance of novel high strength Light weight nanostructured alloys. A new family of rapid solidified alloys show good mechanical properties with combined high strength and low density, these alloys have the potential to be used in pistons in car engines and replace Ti-alloys in gas turbines; the consequent reduction in weight and inertial forces will reduce fuel consumption and increase power output.
Tests performed to data show these alloys have very good fatigue resistance, but there have been no fundamental studies to investigate the mechanisms for this; the hypothesis is that initiated fatigue cracks are arrested at interfaces between the matrix and reinforced zones. If so, then the strain paths arising from process variations during forging may have a significant effect on microstructure and the local fatigue properties. To study this, a range of microstructures of a nanostructured Al alloy obtained by different heat treatments and processing conditions will be produced and tested to correlate fatigue crack initiation and growth with the microstructure; importantly the interactions between arrested fatigue cracks and local microstructure will be studied using advanced electron microscopy, including high resolution EBSD and TEM of FIB-milled selected regions, to develop mechanistic models for fatigue resistance.
In situ study of atmospheric stress corrosion cracking in engineering alloys under controlled humidity environments
James Marrow and Marina Galano
Stress corrosion cracking of engineering alloys, such as stainless steels and high strength aluminium, can occur gradually in specific conditions of controlled humidity and temperature - if a salt deposit is present. To predict the lifetime of structural components, it is very important to understand the kinetics of both crack initiation and crack propagation. However, the presence of the corrosion deposit makes direct observations difficult, particularly of the early stages of crack development.
This project will investigate the effects of surface finish and applied stress, utilising digital image correlation (DIC) to detect the onset of stress corrosion cracking and quantify its propagation during long term tests. Previous studies have demonstrated that DIC can detect cracks beneath the corrosion deposit. A key objective will be to apply a novel method that injects the measured crack tip displacement field into finite element analysis software to obtain the crack's strain energy release rate - this describes the mechanical driving force that is responsible for crack propagation. Combined with local measurements of the crack tip opening displacement, the aim is to understand the influence of mechanical factors in the early stages of stress corrosion cracking in engineering alloys. The use of X-Ray computed tomography and digital volume correlation to study cracks in three-dimensions will also be explored.
The project is suitable for students with s background in engineering, materials science or physics.
Also see homepages: James Marrow
Experimental Validation of Crack Propagation Criteria under Mixed Mode Loading
To accurately predict crack paths in brittle materials, it is important to properly address the effect of mixed mode loading in multi-axial stress states. Predictive models exist, and their experimental validation needs support from direct measurement the crack tip strain fields for comparison with the predicted strain fields; the latter are currently used to predict the crack path. Discrepancies are expected due to material microstructure effects such as aggregate interlocking (from shear loading), for instance. We have developed tools so that direct measurement of crack tip displacement fields can be used to calculate the stress intensity factor, via the J-integral. This is done by injecting the measured displacements as boundary conditions into a Finite Element mesh; the displacement field is obtained by digital image correlation.
This project will apply these methods to examine the crack propagation criteria in brittle materials, such as the polygranular graphite used in current and next generation nuclear reactors. The project will also investigate the relationships between the applied stress state, the local strain fields and the crack propagation path. This experimentally-based study will support the ongoing modelling and experimental studies in industry; an EPSRC iCASE studentship with industry may be available.
The project is suitable for students with an engineering, physics or materials background and will involve techniques such as digital image correlation, finite element modelling and computed X-ray tomography.
Also see homepages: James Marrow
Three-Dimensional Fracture Mechanics
James Marrow, David Nowell (Engineering)
The fracture resistance of engineering materials is measured using standard test specimens; real cracks and engineering components are three-dimensional and more complex, so approximations and adjustments are needed to reliably assess their structural integrity. Over-conservatism, to safely account for the uncertainties in these adjustments, can have significant economic consequences. There is also an increasing need to miniaturized test specimens, to monitor the degradation of structural material properties in fission and fusion energy generating power plants.
We are using 2D and 3D digital correlation image analysis, combined with X-ray computed tomography techniques (laboratory and synchrotron), to obtain precise, in-situ, measurements of the material displacements inside solid samples, such as the strain distribition at stress concentrations; damage development relaxes the elastic strain energy and increases strength for example.
You will investigate, by experiment and finite element modelling, the propagation of three-dimensional cracks, to develop novel test methods to study energy materials.
The project is suitable for graduates with an engineering, mathematical or physics background.
Also see homepages: James Marrow
Also see a full listing of New projects available within the Department of Materials.