Measurement of Creep Deformation in Weldments

This PhD project has developed a new high temperature strain measurement system using Digital Image Correlation (DIC) in order to investigate spatially varying and time dependent deformation during high temperature creep tests of engineering materials. Several challenges associated with measuring creep deformation at elevated temperature have been overcome including the choice of specimen design, specimen oxidation, furnace temperature uniformity, image distortion caused by thermal currents and sufficient illumination. It is demonstrated that the system created can produce reliable measurement data over a period of several months with a spatial resolution of 0.6 mm for temperatures up to 650°C, but in principle higher resolution and temperatures should be achievable. The research aim of this project, funded by EDF Energy (formerly British Energy), was to attempt to measure spatially varying creep deformation properties across thick and thin section weldments that operate at high temperatures in UK advanced gas cooled reactor power plant (AGR). The new measurement system is applied to examine the creep behaviour of a thick section multi-pass welded joint made from Type 316H austenitic stainless steel which was supplied by EDF Energy. Specifically the local creep deformation properties across the weldment in the parent material, heat affected zone (HAZ) and multipass weld layers are investigated in medium term creep tests (>2300 hours). This is achieved by cutting samples from three different locations of the thick section joint, that is from top, middle and bottom positions, and subjecting them to tensile and creep testing at a temperature of 545°C. Spatially resolved stress-strain (tensile) and strain-time (creep) results were obtained transversely across the whole section of the multi-pass weldment and across the thickness direction. The DIC in-situ measurements also provided strain information in the transverse to loading direction from which the reduction of area of the specimen and true stress and strain distribution were calculated. The weld metal showed faster creep rates than HAZ and parent materials and this is attributed to the observed introduction of substantial plastic strain in the parent material on initial loading. Locally the creep strain distribution in the weld metal appears to correlate with individual weld passes. The full-field measurement results allowed the development of creep deformation leading to ultimate rupture to be observed. The high temperature tensile and creep results presented in this thesis demonstrate the capability of the new DIC based system created for full field measurements of displacement and strain at high temperature during creep tests enduring several thousand hours. The system opens a new horizon for studying deformation and rupture behaviour of complex structures at elevated temperature

An on-the-bottom sea gravimeter.

Massachusetts Institute of Technology. Dept. of Geology and Geophysics. Thesis. 1966. Ph.D.Lacking l. 23 and l. 24.Bibliography: leaves 184-187.Ph.D

Deformation studies of the folded myolites of the Moine Thrust, Eriboll district, Northwest Scotland.

An area in the northern part of the Moine Thrust Zone of Loch Eriboll and in the NE side of Loch Hope, NW Scotland, has been mapped in the scale of approximately 1:10,560. Detailed measurements have beea made of structures such as foliations and lineations and these have been studied and analysed geometrically in terms of their relative age and the consistence over the whole area. The mapping has also traced the intricate pattern of thrust faults which trend roughly NNE/SSW. These thrust zones delimit different nappes and the deformation aspects of these faults indicate that the rheology of the rocks suffered changes during the thrust belt evolution. The easternmost major thrust zone is considered to have been developed first and clearly shows the characteristics of a ductile deformation zone. This zone is interpreted here as the Moine Thrust Zone, sensu stricto. A conspicuous mylonitic zone lies beneath and trends parallel to the Moine Thrust Zone and is limited in the west by a thrust which carried the mylonites onto clearly non mylonitic rock. The width of the mylonitic zone varies from Loch Hope in the north to the SE end of Loch Eriboll. This width variation is interpreted as due to thickening of the mylonitic zone by effects of folding and also due to the different deformation bands which anastomose and die out. Closely spaced cross sections, transverse to the extension of the belt of deformation are illustrated and discussed. Strain analyses were carried out in two different domains of the mapped area. In the southern half of the area, where the frequency of folds is high, the distribution of fold hinges in sheath or curvilinear folds were used as strain indicators. Models, numerical methods and computer programmes for this strain evaluation have been thoroughly investigated. A detailed description of the methods used and tests performed with the constructed computer programmes is given. The results are analysed in conjunction with the land geology and structure. For the northerly half of the mapped area, strain estimations have been made using the grain shapes of the Paleozoic quartzites which are common in the two lowermost nappes. A new method for fitting the strain ellipsoid using three orthogonal ellipses was devised. A computer programme making use of this method was constructed and applied to the existent data. An alternative solution is also presented for the case where the fitted surface is not an ellipsoid. The strain results with the above methods are compared with those obtained using other published programmes and methods of strain estimation. . Microtextural variations in the Paleozoic quartzites of the northern domain have been studied. A detailed textural description and correlation is made between the textures and the available information on the deformation intensities shown by the quartz grains. An increase in the measured strain intensity is generally accompanied by an increase in the amount of recrystallized new quartz grains. These facts are consistent with the geology and structures of the nappes where sampling was done. Paleostress estimates using recrystallized grain sizes have been performed at 31 localities in the Eriboll and Hope areas. The methodology of particle-size estimation is described in detail. The necessity for a standardization in the methods of particle-size measurement is emphasized with examples. The estimations of the differential stresses are greater in zones of greater relative deformation intensity. Although there are limitations and some adverse criticisms on the reliability of these paleostress estimates, the conclusion reached by this study is that they form a pattern that fits well with the geology and structure of the investigated area. Rheologic considerations on quartz deformation constitutes the last part of the thesis. Deformation maps were constructed for this study using ranges of probable differential stress and the measured size of the newly recrystallized quartz grains. It is concluded that strain is predominantly accommodated by internal mechanisms operated by dislocation processes. It is also inferred that the operative strain-rate for the deformation conditions of this area, is between 10-13s -1 and 10-12s-

Bowdoin Orient v.137, no.1-25 (2007-2008)

https://digitalcommons.bowdoin.edu/bowdoinorient-2000s/1008/thumbnail.jp

Maritime expressions:a corpus based exploration of maritime metaphors

This study uses a purpose-built corpus to explore the linguistic legacy of Britain’s maritime history found in the form of hundreds of specialised ‘Maritime Expressions’ (MEs), such as TAKEN ABACK, ANCHOR and ALOOF, that permeate modern English. Selecting just those expressions commencing with ’A’, it analyses 61 MEs in detail and describes the processes by which these technical expressions, from a highly specialised occupational discourse community, have made their way into modern English. The Maritime Text Corpus (MTC) comprises 8.8 million words, encompassing a range of text types and registers, selected to provide a cross-section of ‘maritime’ writing. It is analysed using WordSmith analytical software (Scott, 2010), with the 100 million-word British National Corpus (BNC) as a reference corpus. Using the MTC, a list of keywords of specific salience within the maritime discourse has been compiled and, using frequency data, concordances and collocations, these MEs are described in detail and their use and form in the MTC and the BNC is compared. The study examines the transformation from ME to figurative use in the general discourse, in terms of form and metaphoricity. MEs are classified according to their metaphorical strength and their transference from maritime usage into new registers and domains such as those of business, politics, sports and reportage etc. A revised model of metaphoricity is developed and a new category of figurative expression, the ‘resonator’, is proposed. Additionally, developing the work of Lakov and Johnson, Kovesces and others on Conceptual Metaphor Theory (CMT), a number of Maritime Conceptual Metaphors are identified and their cultural significance is discussed