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Thomas Marrow

Professor James Marrow
James Martin Professor of Energy Materials

Mansfield College

Oxford Martin School

 

Tel: 07540 722660 (mobile)
Tel: +44 1865 273938 (Room 110.10.18)
Tel: +44 1865 273777 (reception)
Fax: +44 1865 273789 (general fax)

ORCID iD iconorcid.org/0000-0001-6120-9826
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X-ray Tomography Research Images on Instagram

Summary of Interests

My research is focussed on the degradation of structural materials and the role of microstructure.  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.

We use synchrotron tomographt and also laboratory tomography in our work.  You can follow some of the images we obtain on our laboratrory tomography instrument here www.instagram.com/xradia_oxford

Current Research Projects

3D multi-scale characterization and modelling of damage in ceramic matrix composites
Shixiang Zhao, Prof. James Marrow
SiC/SiC ceramic matrix composites are promising materials for high temperature structural components in the next nuclear power generations. Those applications include accident tolerant fuel cladding. Such components must be able to safely operate in extreme environments. In order to understand of the fracture behaviour of such materials, different modes of loading are applied to the test specimens, including the complex hoop pressurization loading. In this project, we use innovative in-situ characterization technologies, such as high-resolution Synchrotron X-ray tomography and digital volume correlation, to reveal the 3D mechanical behaviour of the materials. In collaboration with Diamond Synchrotron and University of Manchester, we can investigate the 3D mechanical response of the materials at the elevated temperature up to 1100 °C real time. The microstructure-based modelling, FEMME (https://doi.org/10.1016/j.engfracmech.2015.05.059), is used to interpret the experimental data and further optimise the materials design. This project is linked to the European 7th Framework programme MatISSE (Materials' Innovations for Safe and Sustainable nuclear) (http://www.fp7-matisse.eu)

Short Crack Propagation in an Anisotropic Polycrystalline Metal
Phil Earp, Prof. James Marrow, Prof. Alan Cocks
This project is investigating the deformation of polycrystalline 𝛼-uranium leading to crack formation. It is thought that the interaction between microstructural features such as twins and grain boundaries cause stress concentrations that lead to fracture initiation. Experiments are being performed to measure the development of strain in the material as it deforms, locate the regions of high stress, and characterise the form of this stress concentration and how the material accommodates it. Neutron diffraction is being used to measure lattice strain and identify texture changes due to deformation twinning. Two-camera Digital Image Correlation (DIC) will be used to characterise the deformation of the material and identify areas of strain localisation. High Angular Resolution Electron Backscatter Diffraction (HR-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 results will provide data for development and validation of new crystal plasticity models for orthorhombic metals, as part of a related project in the Department of Engineering.

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.

Micro-mechanical Testing of the hex-BN Interlayer in SiC/SiC Composites for Aerospace Application
Robin De Meyere, Prof. David Armstrong, Prof. James Marrow
This project - funded by Rolls-Royce plc - investigates the degradation of the hex-BN interlayer in SiC/SiC composites used in engine components. Silicon carbide fibre/silicon carbide matrix composites are finding renewed interest in the aerospace community for use as high temperature components in engines due to the potential for significant weight savings over metallic parts. Due to the low fracture toughness of monolithic silicon carbide, the most promising concepts use silicon carbide fibres embedded in a silicon carbide matrix. The toughness of the composite is achieved by the application of interphase coating to the fibre before the matrix is applied, which allows for cracks to deviate from the matrix, increasing toughness from fibre pullout and crack bridging. It is critical for the interphase coating to maintain the appropriate properties (modulus, interfacial shear strength, friction, etc.) to maintain the desired composite behaviour. Over time, the interphase coating can degrade due to cyclic loading and environmental exposures as a result of frictional heating, oxidation, and other environmental mechanisms. These can change the properties of the fibre interphase resulting in regions that are embrittled or have poor load sharing. This project aims to use novel micro-mechanical testing methods to measure the strength and toughness of the individual composite components as well as the interfaces in virgin material, and in materials which have been environmentally aged for different lengths of time. These tests will be carried out both at room temperature and elevated temperatures up to 1000ºC in the hot-temperature nano-indenter. Advanced electron microscopy techniques, including EDX, EBSD and TKD will be used to image both environmental and mechanical damage. Macro mechanical-testing in conjunction with X-ray tomography (both lab and synchrotron based) will be performed and contrasted to finite element simulations, in order to relate the micro-scale properties as a function of temperature and degradation to bulk behaviour. 

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.

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 and cortical bone  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. In this project, mechanical tests including compression tests on limpets in both wet and dry conditions and Hertzian indentation tests on cortical bones in both wet and dry conditions have be done to observe the mechanical behaviours of these biomaterials using in-situ high resolution X-ray tomography. After pre-processing using Imagej, the reconstructed images are analysed using digital volume correlation (DVC) to obtain the full displacement fields within the volume of materials under different loading states. Image-based finite element models are built using the rotation-corrected 3D displacement field, extracted from DVC as boundary conditions, to obtain the stress/strain relationship and elastic modulus. The scientific aspects of the project lie on: 1) Use of image-modelling techniques to build a finite element model to describe damage developed in cortical bones under indentation 2) Image-based modelling techniques to incorporate the hierarchical structures of biomaterials into models.

Exploring degradation and failure mechanisms in solid state batteries using in situ X-ray tomography and NMR
Ziyang Ning, Prof. James Marrow, Prof. Peter G Bruce
Solid state batteries are a promising type of battery to replace current conventional liquid state Lithium-ion battery due to their greater safety, higher energy density and wider operating temperature range for energy storage. However, degradation and failure induced by lithiation are still a major challenge for solid state batteries. X-ray tomography has emerged as a powerful technique for studying lithium ion batteries, allowing non-destructive and quantitative imaging of these complex systems. NMR (nuclear magnetic resonance) can also help reveal the electrochemical process by quantitative analysis. This project involves the application of in situ X-ray tomography and NMR characterization of electrochemical process and microstructural change in synthesized solid state batteries. The tomography scan (during cycling) aims to map the processes of lithium stripping, plating, dendrite formation and microstructural change in the bulk volume and at the SEI (solid electrolyte interface), while quantitative analysis of the internal strain can be achieved by DVC (digital volume correlation). Experiments will be carried out on different electrolyte materials, with different cycling conditions, e.g. different current densities, applied pressures. NMR will give further information about the chemical environmental change at the interface induced by electrochemical processes.

In situ 3D observation of damage development and healing in a carbon-fibre/epoxy composite
Yiwen Zhang (Part II undergraduate Project Student) and Prof. James Marrow
The aim of this project is to investigate the toughening mechanism of interface-toughened carbon fibre epoxy composite. It has been shown by our collaborators at Sheffield (Patrick Smith) that the interlaminar fracture toughness can be improved by printing PMMA droplets on the interface between carbon fibre epoxy plys. In situ delamination tests are performed on inkjet-printed samples provided by Sheffield University. By taking a series of laboratory and synchrotron X-ray tomographs, we can observe the propagation process of interlaminar crack and how it interacts with printed droplets. Digital volume correlation measurement is being used to quantify how the strain field in the region of interest changes during this process.

8 public active projects

Research Publications

Summary of publications on ORCID

Huber, J. E., Hofmann, F., Barhli, S., Marrow, T. J., & Hildersley, C. (2017). Observation of crack growth in a polycrystalline ferroelectric by synchrotron X-ray diffraction. Scripta Materialia, 140, 23–26. https://doi.org/10.1016/j.scriptamat.2017.06.053

Vertyagina, Y., & Marrow, T. J. (2017). A multi-scale three-dimensional Cellular Automata fracture model of radiolytically oxidised nuclear graphite. Carbon. https://doi.org/10.1016/j.carbon.2017.06.031

Cinar, A. F., Barhli, S. M., Hollis, D., Flansbjer, M., Tomlinson, R. A., Marrow, T. J., & Mostafavi, M. (2017). An autonomous surface discontinuity detection and quantification method by digital image correlation and phase congruency. Optics and Lasers in Engineering, 96, 94–106. https://doi.org/10.1016/j.optlaseng.2017.04.010

Barhli, S. M., Mostafavi, M., Cinar, A. F., Hollis, D., & Marrow, T. J. (2017). J-Integral Calculation by Finite Element Processing of Measured Full-Field Surface Displacements. Experimental Mechanics. https://doi.org/10.1007/s11340-017-0275-1

Yang, Z., Ren, W., Sharma, R., McDonald, S., Mostafavi, M., Vertyagina, Y., & Marrow, T. J. (2017). In-situ X-ray computed tomography characterisation of 3D fracture evolution and image-based numerical homogenisation of concrete. Cement and Concrete Composites, 75, 74–83. https://doi.org/10.1016/j.cemconcomp.2016.10.001

Barhli, S. M., Saucedo-Mora, L., Simpson, C., Becker, T., Mostafavi, M., Withers, P. J., & Marrow, T. J. (2016). Obtaining the J-integral by diffraction-based crack-field strain mapping. Procedia Structural Integrity, 2, 2519–2526. https://doi.org/10.1016/j.prostr.2016.06.315

Mostafavi, M., Bradley, R., Armstrong, D.E.J., and Marrow, T.J. (2016) Quantifying yield behaviour in metals by X-ray nanotomography. Sci. Rep., 6, 34346. doi:10.1038/srep34346

Saucedo-Mora, L., Lowe, T., Zhao, S., Lee, P.D., Mummery, P., Marrow, T.J., (2016) In situ observation of mechanical damage within a SiC-SiC ceramic matrix composite. J. Nucl. Mater., 481, 13–23. doi:10.1016/j.jnucmat.2016.09.007

Saucedo-Mora, L., Zou, C., Lowe, T., & Marrow, T. J. (2016). Three-dimensional measurement and cohesive element modelling of deformation and damage in a 2.5-dimensional woven ceramic matrix composite. Fatigue & Fracture of Engineering Materials & Structures. https://doi.org/10.1111/ffe.12537

Vertyagina, Y., and Marrow, T.J. (2016) Multifractal-based assessment of Gilsocarbon graphite microstructures. Carbon N. Y., 109, 711–718. doi:10.1016/j.carbon.2016.08.049

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).

Slámecka, K. Skalka, P., Ielko, 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.

 

 

Projects Available

Thermo-mechanical property measurement of nuclear graphites at elevated temperature
T J Marrow

This EPSRC Industrial CASE (iCASE) project with the UK National Nuclear Laboratory (NNL) aims to understand the thermo-mechanical properties of nuclear graphites at elevated temperatures (up to 850°C) that are relevant to current and future nuclear systems.

The experimental studies will investigate the relationships between applied total strains (tensile and compressive, measured by image correlation in 2-D and 3-D) and the elastic strains in the graphite crystals (measured, for instance, by synchrotron X-ray and neutron diffraction).

The local effects on microstructure and its properties will be examined by correlative Focussed-Ion Beam (FIB) tomography, electron microscopy, Raman spectroscopy and micromechanical testing at ambient and elevated temperatures. These studies aim to understand how tensile and compressive deformations are accommodated by competing mechanisms such as micro cracking, basal slip and twinning, and what effects this may have on the coefficient of thermal expansion.

These data will provide inputs for non-linear finite element modelling of the behaviour of graphites at elevated temperatures. The objective is to validate micro-mechanistic models for graphite deformation, and to provide the foundations for future work on irradiated graphites. During the secondment with the sponsor, the student will engage with NNL's work on modelling and property measurement of irradiated graphites.

This is a 4-year EPSRC Industrial CASE studentship in conjunction with NNL and will provide full fees and maintenance for a student who has home fee status (this includes an EU student who has spent the previous three years (or more) in the UK undertaking undergraduate study). Candidates with EU fee status are eligible for a fees-only award, but would have to provide funding for their living costs from another source such as personal funds or a scholarship. The stipend will be £16,777 per year. Information on fee status can be found at http://www.ox.ac.uk/admissions/graduate/fees-and-funding/fees-and-other-charges.

Applications will be considered as and when they are received and this position will be filled as soon as possible, but the latest date for receipt of applications will be 25 January 2019.

On the application form, in the section headed ‘Departmental Studentship Applications’, you must indicate that you are applying for a studentship and enter the reference code for this studentship 18MATERIALS03.

Any questions concerning the project can be addressed to Professor James Marrow (james.marrow@materials.ox.ac.uk). General enquiries on how to apply can be made by e mail to graduate.studies@materials.ox.ac.uk. You must complete the standard Oxford University Application for Graduate Studies. Further information and an electronic copy of the application form can be found at http://www.ox.ac.uk/admissions/postgraduate_courses/apply/index.html

Also see homepages: James Marrow

Experimentally-informed 3D modelling of damage development in interfacially-toughened composite laminates
James Marrow

Aviation and wind power rely on long fibre-reinforced polymer composites for key structural components (fuselage, wings and blades). However, these can fail by delamination (cracking between layers bonded during manufacture), and the necessary conservative design approaches add weight and cost and reduce efficiency. The project's partners at Sheffield have improved delamination resistance without a weight penalty via a novel ink-jet printing manufacturing method, but its actual mechanism is unproven.

The aim of this project is to develop and apply experimentally informed multi-scale modelling to optimise the design and manufacture of ink-jet print toughened and self-healing lightweight composites.

Oxford developed a method for damage simulation in heterogeneous materials. This multi-scale approach introduces fine scale microstructural description into larger scale structural integrity models. In situ measurements of damage development, obtained by digital volume correlation of high resolution X-ray tomographs of mechanically tested samples, can be used to tune the FEMME model [Saucedo-Mora, L., and Marrow, T.J. (2016) http://dx.doi.org/10.1098/rsta.2015.0276]. This permits damage simulation in different loading states and with alternative microstructure architectures. Modelling-led structural design and microstructure optimisation is then feasible, due to the computational efficiency of the FEMME method being 2-3 orders of magnitude greater than conventional image-based finite element simulations.

You will design and perform critical X-ray tomography experiments to observe, in situ and in 3D, the mechanism by which the inkjet printed interfaces fail and potentially self-repair. The aim is then to demonstrate FEMME model simulation of the experimentally observed fracture behaviour, and show its potential to predict the structural integrity of engineering components under different states of load.

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

In situ studies of strain accommodation in MAX phase materials for advanced nuclear energy
James Marrow

MAX phases are 2D-layered hexagonal carbides or nitrides that can exhibit very high mechanical damage tolerance at high temperatures.  In common with ceramics, they are significantly less activated than metals by fast neutron irradiation.  Hence they have potential applications in structural applications for advanced nuclear fission.  However, the structure/property relationships and mechanisms of damage accumulation in MAX phases need to be better understood for microstructure-based modelling to support the design and development of materials and engineering components.

Strain mapping by both image analysis and diffraction has revolutionized studies of deformation in structural materials.  Together, they can provide excellent knowledge of both the elastic and plastic strain states within complex structures, which are internally “strain gauged” in three-dimensions with high spatial resolution.  Image correlation tools applied to tomographs can measure three-dimensional deformation and total strain states with high precision.  Diffraction analysis to measure elastic strains within bulk materials is also routine with neutrons and also on high energy synchrotron X-ray beam-lines.  

The project aims to use X-ray and neutron diffraction and imaging to map, in situ and in 3D, both the total and elastic strains under load and at elevated temperature, and thereby study the mechanisms of strain accommodation in bulk MAX phase materials for nuclear energy, with emphasis on the effects of strain history, microstructure texture and material heterogeneity, in order to improve material reliability and performance.

This project collaborates with SCK-CEN (Belgium) who are developing NbZr carbide and nitride MAX phases for nuclear applications in conjunction with the European Energy Research Alliance Joint Programme in Nuclear Materials that aims to develop materials for next generation sustainable nuclear energy.  Standard mechanical testing (including studies of irradiated materials) are being conducted by SCK-CEN, together with electron-microscopy microstructure characterisation by EBSD and TEM.

The project is suitable for students with a background in materials science, engineering or physics

Also see homepages: James Marrow

Three-Dimensional Deformation and Fracture Mechanics
James Marrow

The mechanical properties and fracture resistance of engineering materials are 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.  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.  Material properties can be extracted from small volumes by indentation tests, but generally we have no knowledge of what actually happens under the surface, and this requires assumptions to be made.

One way to address this is to use 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 deformation and cracking. (e.g. http://dx.doi.org/10.1038/srep34346, http://dx.doi.org/10.1016/j.actamat.2014.08.046 and http://dx.doi.org/10.1016/j.jeurceramsoc.2014.04.002)

The aim of this project is to investigate, by experiment and finite element modelling, the propagation of three-dimensional cracks and deformation under indentations with the objective of developing novel test methods to assess strain hardening and fracture resistance.  You will use high resolution X-ray tomography and digital volume correlation to measure the displacement field under indentations, and you will also study and model the development of cracks in brittle materials.

The project is suitable for graduates with an engineering, mathematical or physics background.

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.  The interactions between microstructure and crack propagation may also be studied by in situ high-resolution computed tomography (Marrow, T.J. et al (2014) http://dx.doi.org/10.1016/j.ijfatigue.2014.04.003).

The project is suitable for students with an engineering, physics or materials background and will involve techniques such as electron microscopy, materials processing digital image correlation, finite element modelling and computed X-ray tomography.

 

Also see homepages: Marina Galano James Marrow

Experimental Validation of Crack Propagation Criteria under Mixed Mode Loading
James Marrow

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 ongoing modelling and experimental studies.

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

Also see a full listing of New projects available within the Department of Materials.