Browsing by Author "Gnaëpel-Herold, T"

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    Neutron residual stress measurements in linepipe
    (Elsevier B. V., 2006-11-15) Law, M; Gnaëpel-Herold, T; Luzin, V; Bowie, G
    Residual stresses in gas pipelines are generated by manufacturing and construction processes and may affect the subsequent pipe integrity. In the present work, the residual stresses in eight samples of linepipe were measured by neutron diffraction. Residual stresses changed with some coating processes. This has special implications in understanding and mitigating stress corrosion cracking, a major safety and economic problem in some gas pipelines. © 2006 Elsevier B.V
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    Neutron residual stress measurements in rails
    (Taylor & Francis, 2013-07-09) Luzin, V; Prask, HJ; Gnaëpel-Herold, T; Gordon, J; Wexler, D; Rathod, C; Pal, S; Daniel, W; Atrens, A
    Rails were among the first objects of study by neutron diffraction strain measurement and the first experiments were done as early as the late 1980s [1, 2]. This interest is easy to explain: the problem of rail fracturing is critical from the public safety point of view and the penetrating ability of neutrons suggested the possibility of breakthrough experiments and fast progress in this field. It was well-established that residual stresses, both near-surface and interior, played a signifi cant role in the development of defects which led to rail failure. This suggested three distinct approaches of neutron diffraction strain measurement that could contribute to various problems of the rail industry. The first method was to map the complete triaxial stress distribution non-destructively in the interior of an intact rail, ideally before and after significant service. Another approach was to use slices, for example to characterize how different processing methods produce favourable or detrimental stress distributions in rails. A third technique was to make non-destructive measurements, but in critical and not very deep portions of rails, for example, to examine defects and their relation to rail failure in the top running surface of rails, e.g. "white layer" formation. © 2013, Taylor & Francis.
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    Through-thickness residual stress measurement by neutron diffraction in Cu+W plasma spray coatings
    (Trans Tech Publications, 2009-11-10) Luzin, V; Matejicek, J; Gnaëpel-Herold, T
    A range of different spraying techniques can be used to coat the surfaces of engineering components. These techniques are based on different principles and can involve high temperature (plasma spray), high kinetic energy (cold spray) or both (HVOF spray – High-Velocity Oxi-Fuel). Resultant residual stress in such coatings, being a characteristic of the spraying process, can reveal details of the stress formation mechanism. When its dependence on the physical parameters and conditions of the spraying process is established, this knowledge can be used for the prediction and control of stress that occurs in applications. Neutron diffraction is a suitable method for obtaining stress distribution in such coatings. Residual stresses in two-phase Cu+W coatings made by water stabilized plasma spraying were studied. Two-phase coatings develop both significant microstress (inter-phase stress) and the stress dependence on phase content of the coating constituents. Through-thickness residual stress profiles have been measured by neutron diffraction with spatial resolution of 0.5 mm for a series of Cu+W coatings with varying volume fractions. Measurements were made in both phases in order to separate micro- and macro-stresses. Comprehensive sample characterization, measurements of the residual stresses, mechanical and thermal properties of the composite coatings enabled quantitative modeling and interpretation of the experimental data.
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    Use of neutron diffraction for stress measurements in thin and thick thermal sprayed coatings
    (Maney Publishing, 2010-03-01) Luzin, V; Prask, HJ; Gnaëpel-Herold, T; Sampath, S
    Thermal spraying is a widely used and cost effective technique for the surface protection of engineering components. The spectrum of applications is vast: corrosion protection, wear resistance and abrasion resistance, thermal barriers, electrical (dielectric) coatings, etc. Process induced residual stress has long been recognised as an important factor influencing the integrity and overall performance of coatings. Residual stress generation during thermal spraying is a complex phenomenon. Significant efforts have been made to improve understanding of the evolution of residual stresses during deposition and to develop practical models for numerical prediction of stress distributions in coatings. Owing to the high penetrating power of neutrons and spatial resolution in the millimetre and submillimetre range, neutron diffraction is, perhaps, the most versatile method for stress determination, and has been used extensively for experimental validation of theoretical predictions. Examples of neutron diffraction residual stress results are presented to illustrate the capabilities of the technique: a thin (∼0·3 mm) Mo/Mo2C composite HVOF coating, several examples of millimetre thick ceramic and metallic coatings, and thick coatings (∼10 mm) of iron made by spray forming. © 2010, Maney Publishing