345 research outputs found

    Non-destructive Evaluation of Workpiece Properties along the Hybrid Bearing Bushing Process Chain

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    To combine the advantages of two materials, hybrid bulk metal workpieces are attractive for subsequent processes such as metal forming. However, hybrid materials rely on the initial bond strength for the effective transfer of applied loads. Thus, a non-destructive evaluation of the bonding along the production process chain is of high interest. To evaluate to what extent non-destructive testing can be employed to monitor the bonding quality between the joining partners steel and aluminum and to characterize the age hardening condition of the aluminum component, ultrasonic testing and electrical conductivity measurements were applied. It was found that a lateral angular co-extrusion process can create homogeneous bonding although the electrical conductivity of the aluminum is altered during processing. A previous bonding before the subsequent die forging process leads to a sufficient bonding in areas with little deformation and is therefore, advantageous compared to unjoined semi-finished products, which do not form a bonding if the deformation ratio is too small. An influence of the subsequent heat treatment on the bonding is not visible in the ultrasonic testing signals though a homogenized electrical conductivity can be detected, which indicates uniform artificial aging conditions of the aluminum allo

    Nondestructive Testing Methods and New Applications

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    Nondestructive testing enables scientists and engineers to evaluate the integrity of their structures and the properties of their materials or components non-intrusively, and in some instances in real-time fashion. Applying the Nondestructive techniques and modalities offers valuable savings and guarantees the quality of engineered systems and products. This technology can be employed through different modalities that include contact methods such as ultrasonic, eddy current, magnetic particles, and liquid penetrant, in addition to contact-less methods such as in thermography, radiography, and shearography. This book seeks to introduce some of the Nondestructive testing methods from its theoretical fundamentals to its specific applications. Additionally, the text contains several novel implementations of such techniques in different fields, including the assessment of civil structures (concrete) to its application in medicine

    X-ray Computed Tomography and image-based modelling of plant, root and soil systems, for better understanding of phosphate uptake

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    A major constraint to crop growth is the poor bioavailability of edaphic nutrients, especially phosphate (P). Improving the nutrient acquisition efficiency of crops is crucial in addressing pressing global food-security issues arising from increasing world population, reduced fertile land and changes in the climate. Despite the undoubted importance of root architecture and root/soil interactions to nutrient uptake, there is a lack of approaches for quantifying plant roots non-invasively at all scales. Mathematical models have allowed our understanding of root and soil interactions to be improved, but are almost invariably reliant on idealised geometries or virtual root growth models. In order to improve phenotyping of advantageous traits for low-P conditions and improve the accuracy of root growth and uptake models, more sophisticated and robust approaches to in vivo root and soil characterisation are needed. Microfocus X-ray Computed Tomography (?-CT) is a methodology that has shown promise for noninvasive imaging of roots and soil at various scales. However, this potential has not been extended to consideration of either very small (rhizosphere scale) or large (mature root system scale) samples. This thesis combines discovery experiments and method development in order to achieve two primary objectives:• The development of more robust, well-described approaches to root and soil ?-CT imaging. Chapters 2 and 3 explore the potential of clinical contrasting methods in root investigation, and show how careful consideration of imaging parameters combined with development of user invariant image-processing protocol can improve measurement of macro-porous volume fraction, a key soil parameter. • Chapter 4 develops an assay for first-time 3D imaging of root hairs in situ within the rhizosphere. The resulting data is used to parameterise an explicit P uptake model at the hair scale, suggesting a different contribution of hairs to uptake than was predicted using idealised geometries. Chapter 5 then extends the paradigm for root hair imaging and model generation, building a robust, modular workflow for investigating P dynamics in the rhizosphere that can accommodate non-optimal soil-water states

    Multiscale Quantitative Imaging of Human Femoral Heads Using X-ray Microtomography

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    PhDClinical diagnostic tools provide limited information on the underlying structural and mechanical properties of bone-tissue affected by degenerative and bone metabolic diseases. In-vivo bone failure studies provide limited information due to constraints such as X-ray dosage, cost and various other practicalities. In-vitro studies are thus required to enhance understanding of this phenomenon. The aims of this study were to use quantitative high-definition X-ray Micro-Tomography (XMT) to assess factors contributing to pathological and non-pathological bone failure and repair in relation to the mechanics of whole human femoral heads. XMT images of one normal and six pathological femoral heads were collected at 26 – 8.8 μm voxel resolution and evaluated to determine structural features; bone mineral concentration (BMC); and using image analysis, identify microcallus formations. In addition, in-vitro compression tests were carried out on specimens taken from regions with different anatomical loading. Bone quality was then related to the anatomical loading and BMC. Results from non-pathological tissue where used to establish a baseline for measurements of structural features. Microcallus formations where identified and used as markers to map the occurrence of bone damage. In osteoarthritic (OA) heads, the damage was found to be concentrated in localised clusters. Conversely, in the osteoporotic head damage was distributed homogeneously throughout the entire specimen. No significant difference in the BMC was observed, however there was a iii significant difference in the bone quality values between the non-pathological and pathological heads, and also between the pathologies. In-vitro mechanical testing revealed a difference in the mechanical properties of OA trabecular bone in relation to bone quality measurements but the samples exhibited no significant correlation to anatomical loading. X-ray Ultra Microscopy (XuM) at 200nm and 775nm voxel resolution was used to investigate the nano-morphology of individual trabeculae. The XuM images showed differences in bone structure and fewer osteocyte lacunae present close to fracture site. XuM also identified micro-cracks within trabeculae that were encased by microcallus formations. The application of novel quantitative high definition X-ray imaging to clinically relevant tissue at multiple length scales has provided new metrological data on the distribution of damage within pathological tissue. Insight into the vulnerability of diseased tissue to damage could ultimately lead to improved diagnosis from clinical radiographs

    Investigating the ultrastructure of enamel white spot lesions (WSL) using Optical Coherence Tomography at different length scales

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    White spot lesion (WSL) is the clinical presentation of early caries, which is a demineralisation that occurs at subsurface level, with a well-mineralised surface layer enclosing the lesion. Early diagnosis and treatment of WSL is crucial to prevent further destruction of tooth structure. The aim of this research is to investigate the potential of optical coherence tomography (OCT) to be used as an adjunct diagnostic clinical tool to evaluate the severity of such lesions. This research also compared the OCT outputs with traditional histology, X-ray Microtomography (XMT), Synchrotron X-ray Diffraction (SXRD) and Scanning Electron microscope (SEM). All specimens were collected from patients undergoing dental treatment at Eastman Dental Hospital with informed consent following ethical approvall. Initially, Artificial WSLs were induced on sound enamel surfaces using a buffered methylcellulose gel system at pH 4.6 for 7 and 14 days. Type-matched native WSL and healthy control teeth were selected based on ICDAS for comparison. Imaging of samples was obtained using OCT of whole teeth and by polarised microscopy, SXRD, XMT and SEM of polished 250 μm thick sections. Polarised microscope, XMT and SEM confirmed the findings of the OCT results. Images showed that the more back scattered signals recorded, the deeper the destruction throughout enamel thickness. SXRD results showed changes in enamel texture, which was interpreted from measuring crystallite orientations and lattice parameter. SXRD result showed some correlation with OCT images, however more investigation is required to confirm the findings. In conclusion, the variations observed in the back-scattered light in OCT experiment were because of mineral density variation within enamel structure, as well as the changes in prismatic structure and may be related to crystallite texture and orientation. OCT has shown to be a reliable non-destructive technique, that can investigate the internal structure, by measuring the back-scattered light from materials such as enamel and dentine. In healthy samples, OCT B-scans showed a homogenous pattern of scattering intensity throughout enamel structure, indicating healthy structure, while in both natural and induced white spot lesions, a non homogenous scattering intensity was observed, indicating changes in enamel structure
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