@article{ChristenLevchukSchoriEtAl2012,

title = {Deformable image registration and 3D strain mapping for the quantitative assessment of cortical bone microdamage},

author = {David Christen and Alina Levchuk and Stefan Schori and Philipp Schneider and Steven K. Boyd and Ralph Müller},

url = {http://eprints.soton.ac.uk/361073/},

year  = {2012},

date = {2012-01-01},

journal = {Journal of the Mechanical Behavior of Biomedical Materials},

volume = {8},

pages = {184–193},

abstract = {The resistance to forming microcracks is a key factor for bone to withstand critical loads without fracturing. In this study, we investigated the initiation and propagation of microcracks in murine cortical bone by combining three-dimensional images from synchrotron radiation-based computed tomography and time-lapsed biomechanical testing to observe microdamage accumulation over time. Furthermore, a novel deformable image registration procedure utilizing digital volume correlation and demons image registration was introduced to compute 3D strain maps allowing characterization of the mechanical environment of the microcracks. The displacement and strain maps were validated in a priori tests. At an image resolution of 740?nm the spatial resolution of the strain maps was 10?ensuremathmum (MTF), while the errors of the displacements and strains were 130 nm and 0.013, respectively. The strain maps revealed a complex interaction of the propagating microcracks with the bone microstructure. In particular, we could show that osteocyte lacunae play a dual role as stress concentrating features reducing bone strength, while at the same time contributing to the bone toughness by blunting the crack tip. We conclude that time-lapsed biomechanical imaging in combination with three-dimensional strain mapping is suitable for the investigation of crack initiation and propagation in many porous materials under various loading scenarios.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{SchoettleSinclairStarinkEtAl2012,

title = {Deflected ‘teardrop cracking’ in nickel based superalloys: Sustained macroscopic deflected fatigue crack growth},

author = {C. Schoettle and I. Sinclair and M. J. Starink and P. A. S. Reed},

url = {http://www.sciencedirect.com/science/article/pii/S0142112312001569},

doi = {http://dx.doi.org/10.1016/j.ijfatigue.2012.04.017},

issn = {0142-1123},

year  = {2012},

date = {2012-01-01},

journal = {International Journal of Fatigue},

volume = {44},

pages = {188 - 201},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ScottSinclairSpearingEtAl2012,

title = {Damage accumulation in a carbon/epoxy composite: Comparison between a multiscale model and computed tomography experimental results},

author = {A. E. Scott and I. Sinclair and S. M. Spearing and A. Thionnet and A. R. Bunsell},

url = {http://www.sciencedirect.com/science/article/pii/S1359835X12001042},

doi = {10.1016/j.compositesa.2012.03.011},

issn = {1359-835X},

year  = {2012},

date = {2012-01-01},

journal = {Composites Part A: Applied Science and Manufacturing},

volume = {43},

number = {9},

pages = {1514 - 1522},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{LambertChambersSinclairEtAl2012,

title = {3D damage characterisation and the role of voids in the fatigue of wind turbine blade materials},

author = {J. Lambert and A. R. Chambers and I. Sinclair and S. M. Spearing},

url = {http://www.sciencedirect.com/science/article/pii/S0266353811004155},

doi = {10.1016/j.compscitech.2011.11.023},

issn = {0266-3538},

year  = {2012},

date = {2012-01-01},

urldate = {2014-04-24},

journal = {Composites Science and Technology},

volume = {72},

number = {2},

pages = {337–343},

abstract = {The fatigue mechanisms of Glass Fibre Reinforced Polymer (GFRP) used in wind turbine blades were examined using computed tomography (CT). Prior to mechanical testing, as-manufactured [+45/−45/0]3,s glass/epoxy specimens were CT scanned to provide 3-dimensional images of their internal microstructure, including voids. Voids were segmented and extracted, and individual characteristics and volumetric distributions were quantified. The coupons were then fatigue tested in uniaxial loading at R = −1% to 40% of the nominal tensile failure stress. Some tests were conducted to failure for correlation with the initial void analysis and to establish failure modes. Other tests were stopped at various life fractions and examined using CT to identify key damage mechanisms. These scans revealed transverse matrix cracking in the surface layer, occurring predominantly at free edges. These free-edge cracks then appeared to facilitate edge delamination at the 45/−45° interface. Propagation from sub-critical, surface ply damage to critical, inner ply damage was identified with either a −45/0° delamination, or a 0° fibre tow failure allowing a crack to propagate into the specimen bulk. Final failure occurred in compression and was characterised by total delamination between all the 45/−45° plies. A quantitative void analysis, taken from the pre-test CT scans, was also performed and compared against the specimens’ fatigue lives. This analysis, to the authors’ knowledge the first of its kind, measured and plotted approximately 10,000 voids within the gauge length of each specimen. The global void measurement parameters and distributions showed no correlation with fatigue life. A local ply-level investigation revealed a significant correlation between the largest void and fatigue life in the region of the laminate associated with the crack propagation from sub-critical to critical damage.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{DhillonSchneiderKuhnEtAl2011,

title = {Analysis of sintered polymer scaffolds using concomitant synchrotron computed tomography and in situ mechanical testing},

author = {Amritpaul Dhillon and Philipp Schneider and Gisela Kuhn and Yvonne Reinwald and Lincoln J. White and Alina Levchuk and Felicity R. A. J. Rose and Ralph Müller and Kevin M. Shakesheff and Cheryl V. Rahman},

url = {http://eprints.soton.ac.uk/361071/},

year  = {2011},

date = {2011-12-01},

journal = {Journal of Materials Science: Materials in Medicine},

volume = {22},

number = {12},

pages = {2599–2605},

abstract = {The mechanical behaviour of polymer scaffolds plays a vital role in their successful use in bone tissue engineering. The present study utilised novel sintered polymer scaffolds prepared using temperature-sensitive poly(DL-lactic acid-co-glycolic acid)/poly(ethylene glycol) particles. The microstructure of these scaffolds was monitored under compressive strain by image-guided failure assessment (IGFA), which combined synchrotron radiation computed tomography (SR CT) and in situ micro-compression. Three-dimensional CT data sets of scaffolds subjected to a strain rate of 0.01%/s illustrated particle movement within the scaffolds with no deformation or cracking. When compressed using a higher strain rate of 0.02%/s particle movement was more pronounced and cracks between sintered particles were observed. The results from this study demonstrate that IGFA based on simultaneous SR CT imaging and micro-compression testing is a useful tool for assessing structural and mechanical scaffold properties, leading to further insight into structure?function relationships in scaffolds for bone tissue engineering applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{VoideSchneiderStauberEtAl2011,

title = {The importance of murine cortical bone microstructure for microcrack initiation and propagation},

author = {Romain Voide and Philipp Schneider and Martin Stauber and Gerrit H. Lenthe and Marco Stampanoni and Ralph Muller},

url = {httpeprints.soton.ac.uk361072},

year  = {2011},

date = {2011-08-01},

journal = {Bone},

volume = {49},

number = {6},

pages = {1186–1193},

abstract = {In order to better understand bone postyield behavior and consequently bone failure behavior, this study aimed first to investigate cortical bone microstructure and second, to relate cortical bone microstructure to microdamage initiation and propagation in C57BL6 (B6) and C3HHe (C3H) mice; two murine inbred strains known for their differences in bone phenotype. Murine femora of B6 and C3H were loaded axially under compression in a stepwise manner. For each loading step, 3D data sets at a nominal resolution of 700 nm were acquired by means of synchrotron radiation-based computed tomography. Cortical bone microstructure was divided into three phases the canal network, the osteocyte lacunar system, and microdamage. Canal volume density and canal unit volume both correlated highly to crack number density (canal volume density R2=0.64, pensuremath0.005 and canal unit volume R2=0.75, pensuremath0.001). Moreover, the large canal units in C3H bone were responsible for more microdamage accumulation compared to B6 bones. This more pronounced microdamage accumulation due to large intracortical bone voids, which eventually leads to a fatal macrocrack (fracture), represents a potential contributing factor to the higher incidence of bone fractures in the elderly.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{BahBrowneYoungEtAl2011,

title = {Effects of implant positioning in cementless total hip replacements},

author = {M. T. Bah and Martin Browne and P. G. Young and R. Bryan and V. B. Xuan},

url = {http://www.tandfonline.com/doi/abs/10.1080/10255842.2011.595241},

doi = {10.1080/10255842.2011.595241},

year  = {2011},

date = {2011-08-01},

journal = {Computer Methods in Biomechanics and Biomedical Engineering},

volume = {14},

pages = {275–276},

abstract = {Cementless Total Hip Replacements (THRs) are required to approximate as closely as possible the natural joint function for the full postoperative life span. Unfortunately, implant positioning is not always perfect due to the curved shape of the thigh bone and the stem is often straight [1]. Surgeons need to decide on three orientation angles that directly influence the success of a cementless THR: the antero/retro version of the femur neck orientation, implant varus/valgus placement and anterior/posterior orientation. Ideally, to account for positioning variability, all possible implant orientations should be analysed and simulated. Unfortunately, this would be an intractable task if it was attempted experimentally, and computational simulations are often applied to reduce this burden. However, even in computational pre-clinical assessments of implant primary stability, this is a huge task, as it involves generating a new mesh for each new position and solving the corresponding Finite Element (FE) problem [2]. In the current work, this problem is addressed using a mesh morphing-based framework that can efficiently assess the effects of implant positioning.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ReesPriestClayton2011,

title = {The structure of methane gas hydrate bearing sediments from the Krishna–Godavari Basin as seen from Micro-CT scanning},

author = {Emily VL Rees and Jeffery A Priest and Chris RI Clayton},

url = {http://www.sciencedirect.com/science/article/pii/S0264817211001127},

doi = {10.1016/j.marpetgeo.2011.03.015},

year  = {2011},

date = {2011-01-01},

journal = {Marine and Petroleum Geology},

volume = {28},

number = {7},

pages = {1283–1293},

publisher = {Elsevier},

abstract = {The Indian National Gas Hydrate Program (NGHP) Expedition 1, of 2006, cored through several methane gas hydrate deposits on the continental shelf around the coast of India. The pressure coring techniques utilized during the expedition (HYACINTH and PCS) enabled recovery of gas hydrate bearing, fine-grained, sediment cores to the surface. After initial characterization core sections were rapidly depressurized and submerged in liquid nitrogen, preserving the structure and form of the hydrate within the host sediment. Once on shore, high resolution X-ray CT scanning was employed to obtain detailed three-dimensional images of the internal structure of the gas hydrate. Using a resolution of 80 μm the detailed structure of the hydrate veins present in each core could be observed, and allowed for an in depth analysis of orientation, width and persistence of each vein. Hydrate saturation estimates could also be made and saturations of 20–30% were found to be the average across the core section with some portions showing highs of almost 60% saturation. The majority of hydrate veins in each core section were found to be orientated between 50 and 80° to the horizontal. Analysis of the strikes of the veins suggested a slight preferential orientation in individual sample sections, although correlation between individual sections was not possible due to the initial orientation of the sections being lost during the sampling stage. The preferred vein orientation within sample sections coupled with several geometric features identified in individual veins, suggest that hydraulic fracturing by upward advecting pore fluids is the main formation mechanism for the veined hydrate deposits in the K–G Basin.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{MavrogordatoTaylorTaylorEtAl2011,

title = {Real time monitoring of progressive damage during loading of a simplified total hip stem construct using embedded acoustic emission sensors},

author = {Mark Mavrogordato and Mark Taylor and Andrew Taylor and Martin Browne},

url = {http://eprints.soton.ac.uk/185499/},

year  = {2011},

date = {2011-01-01},

journal = {Medical Engineering & Physics},

volume = {33},

number = {4},

pages = {395–406},

abstract = {Acoustic emission (AE) is a non-destructive technique that is capable of passively monitoring failure of a construct with excellent temporal resolution. Previous investigations using AE to monitor the integrity of a total hip replacement (THR) have used surface mounted sensors; however, the AE signal attenuates as it travels through materials and across interfaces. This study proposes that directly embedded sensors within the femoral stem of the implant will reduce signal attenuation effects and eliminate potential complications and variability associated with fixing the sensor to the sample. Data was collected during in vitro testing of implanted constructs, and information from both embedded and externally mounted AE sensors was compared and corroborated by micro-Computed Tomography (micro-CT) images taken before and after testing. The results of this study indicate that the embedded sensors gave a closer corroboration to observed damage using micro-CT and were less affected by unwanted noise sources. This has significant implications for the use of AE in assessing the state of THR constructs in vitro and it is hypothesised that directly embedded AE sensors may provide the first steps towards an in vivo, cost effective, user friendly, non-destructive system capable of continuously monitoring the condition of the implanted construct.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ScottMavrogordatoWrightEtAl2011,

title = {In situ fibre fracture measurement in carbon–epoxy laminates using high resolution computed tomography},

author = {AE Scott and M Mavrogordato and P Wright and I Sinclair and SM Spearing},

url = {http://www.sciencedirect.com/science/article/pii/S0266353811002090},

doi = {10.1016/j.compscitech.2011.06.004},

year  = {2011},

date = {2011-01-01},

journal = {Composites Science and Technology},

volume = {71},

number = {12},

pages = {1471–1477},

publisher = {Elsevier},

abstract = {High resolution Synchrotron Radiation Computed Tomography (SRCT) has been used to capture fibre damage progression in a carbon–epoxy notched [90/0]s laminate loaded to failure. To the authors knowledge this provides the first direct in situ measurement of the accumulation of fibre fractures for a high performance material under structurally relevant load conditions (i.e. fractures within the bulk of an essentially conventional engineering laminate). A high level of confidence is placed in the measurements, as the failure processes are viewed internally at the relevant micromechanical length-scales, as opposed to previous indirect and/or surface-based methods. Whilst fibre breaks are the dominant composite damage mechanism considered in the present work, matrix damage, such as transverse ply cracks, 0° splits and delaminations, were also seen to occur in advance of extensive fibre breaks. At loads where fibre break density levels were significant, splitting and delamination were seen to separate the central 0° ply in the near notch region from the 90° plies. Fibre breaks were initially observed in isolated locations, consistent with the stochastic nature of fibre strengths. The formation of clusters of broken fibres was observed at higher loads. The largest clusters observed consisted of a group of eleven breaks and a group of fourteen breaks. The large clusters were observed at the highest load, at sites with no prior breaks, indicating they occurred within a relatively narrow load range. No strong correlation was found between the location of matrix damage and fibre breaks. The data achieved has been made available online at www.materialsdatacentre.com for ongoing model development and validation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{DierolfMenzelThibaultEtAl2010,

title = {Ptychographic X-ray computed tomography at the nanoscale},

author = {Martin Dierolf and Andreas Menzel and Pierre Thibault and Philipp Schneider and Cameron M. Kewish and Roger Wepf and Oliver Bunk and Franz Pfeiffer},

url = {http://www.nature.com/nature/journal/v467/n7314/abs/nature09419.html},

year  = {2010},

date = {2010-09-01},

journal = {Nature},

volume = {467},

number = {7314},

pages = {436–439},

abstract = {X-ray tomography is an invaluable tool in biomedical imaging. It can deliver the three-dimensional internal structure of entire organisms as well as that of single cells, and even gives access to quantitative information, crucially important both for medical applications and for basic research1, 2, 3, 4. Most frequently such information is based on X-ray attenuation. Phase contrast is sometimes used for improved visibility but remains significantly harder to quantify5, 6. Here we describe an X-ray computed tomography technique that generates quantitative high-contrast three-dimensional electron density maps from phase contrast information without reverting to assumptions of a weak phase object or negligible absorption. This method uses a ptychographic coherent imaging approach to record tomographic data sets, exploiting both the high penetration power of hard X-rays and the high sensitivity of lensless imaging7, 8, 9. As an example, we present images of a bone sample in which structures on the 100?nm length scale such as the osteocyte lacunae and the interconnective canalicular network are clearly resolved. The recovered electron density map provides a contrast high enough to estimate nanoscale bone density variations of less than one per cent. We expect this high-resolution tomography technique to provide invaluable information for both the life and materials sciences},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{BergomiCugnoniWiskottEtAl2010,

title = {Three-dimensional morphometry of strained bovine periodontal ligament using synchrotron radiation-based tomography},

author = {Marzio Bergomi and Joel Cugnoni and H. W. Anselm Wiskott and Philipp Schneider and Marco Stampanoni and John Botsis and Urs C. Belser},

url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7580.2010.01250.x/full},

doi = {10.1111/j.1469-7580.2010.01250.x},

year  = {2010},

date = {2010-06-01},

journal = {Journal of Anatomy},

volume = {217},

number = {2},

pages = {126–134},

abstract = {The periodontal ligament (PDL) is a highly vascularized soft connective tissue. Previous studies suggest that the viscous component of the mechanical response may be explained by the deformation-induced collapse and expansion of internal voids (i.e. chiefly blood vessels) interacting with liquids (i.e. blood and interstitial fluids) flowing through the pores. In the present work we propose a methodology by means of which the morphology of the PDL vascular plexus can be monitored at different levels of compressive and tensile strains. To this end, 4-mm-diameter cylindrical specimens, comprising layers of bone, PDL and dentin covered by cementum, were strained at stretch ratios ranging from lambda = 0.6 to lambda = 1.4 and scanned using synchrotron radiation-based computer tomography. It was concluded that: (1) the PDL vascular network is layered in two distinct planes of blood vessels (BVs): an inner layer (close to the tooth), in which the BVs run in apico-coronal direction, and an outer layer (close to the alveolar bone), in which the BVs distribution is more diffuse; (2) during tension and compression, the porosity tissue is kept fairly constant; (3) mechanical straining induces important changes in BV diameters, possibly modifying the permeability of the PDL and thus contributing to the viscous component of the viscoelastic response observed under compressive forces},

keywords = {},

pubstate = {published},

tppubtype = {article}

}