Energy-resolved neutron imaging for reconstruction of strain introduced by cold working

Energy-resolved neutron transmission imaging is used to reconstruct maps of residual strains in drilled and cold-expanded holes in 5-mm and 6.4-mm-thick aluminum plates. The possibility of measuring the positions of Bragg edges in the transmission spectrum in each 55 × 55 µm2 pixel is utilized in the reconstruction of the strain distribution within the entire imaged area of the sample, all from a single measurement. Although the reconstructed strain is averaged through the sample thickness, this technique reveals strain asymmetries within the sample and thus provides information complementary to other well-established non-destructive testing methods

The score is not the music: integrating experience-based and practice-based perspectives on value co-creation in collective consumption contexts

In response to recent calls for deeper understanding of value co-creation between multiple actors, this article explores co-creation in collective consumption contexts. These are defined as settings within which multiple consumers, and optionally multiple other actors such as service personnel, are co-present (physically and/or virtually) and coordinate with one another during product/service consumption. To understand co-creation in such contexts, the article argues for an integration of practice-based and experience-based perspectives, because while collective coordination occurs via social practices, the value that results is by definition an individual experience. By studying an orchestral music context in which multiple consumers and service providers participate, the authors develop a framework dialectically relating co-creation practices to value. Four variables emerge influencing the relationship between co-creation practices and value: role rigidity, consumer heterogeneity conflict, participation access, and signposting. Value can be constrained by role rigidity and by consumer heterogeneity conflict between consumers of differing competence; mitigating this requires that service providers pay attention to participation access and signposting (guiding consumers to select and combine practices in line with their skills and competences). Overall, the findings show how practices shape not just coordination among consumers, but also social learning. Implications for service organizations include how to facilitate social learning between novices and experts so as to optimize value for all

Experimental and numerical investigation of residual stress effects on fatigue crack growth behaviour of S355 steel weldments

Fatigue crack growth tests have been conducted on S355 G10+M structural steel which is widely used in the fabrication of offshore structures. Fracture mechanics tests have been performed on compact tension specimens with the crack tip located in the heat affected zone. All tests were performed at room temperature in air and the obtained results are compared with the literature data available on a range of offshore structural steels and also the recommended BS7910 trends using the 2-stage law and simplified law. The specimen orientation, with respect to the location of the extraction within the welded plate, has also been examined and discussed in this work. Residual stress measurements have been performed prior to testing by using the neutron diffraction technique. Finally, a numerical model has been developed in order to calculate the effective stress intensity factor range in the presence of residual stresses. The results have shown that the residual stresses play a key role in the fatigue life of the welded structures, especially in the near threshold regio

Residual stress measurements in offshore wind monopile weldments using neutron diffraction technique and contour method

Reliable assessment of the fatigue life of offshore wind monopiles operating in harsh offshore environments relies on quantifying the level of residual stresses locked-in at circumferential weld regions. This study presents, for the first time, residual stress characterisation, using the contour method, on a large structural welded mock-up, typical of the weldment used in offshore wind monopiles. The contour method and neutron diffraction measurements were also conducted on a compact tension specimen extracted from the large mock-up. The extracted compact tension sample, typically used for fracture and fatigue crack growth tests, showed notably significant remnant residual stresses that could impact fracture and fatigue test results. In addition the measured 2D map of transverse residual stresses, acting normal to the crack plane, playing a key role in fatigue crack opening/closure, exhibited variations through the thickness of the compact tension sample. The key conclusion was that the residual stresses in small laboratory samples extracted from large scale weldments should be carefully characterised and taken into account in structural integrity tests. Besides, the measurement results on the welded mock-up showed that the level of damaging tensile residual stress in large-scale mock-ups and hence real size structural welded monopiles is considerably larger than residual stresses in extracted laboratory samples; hence will have more significant influence on structural integrity of offshore wind assets

Experimental investigation of lattice deformation behavior in S355 steel weldments using neutron diffraction technique

This study aims to investigate the influence of welding process on the elastic lattice deformation and its effects on fatigue and fracture behavior of S355 G10+M steel, which is widely used in fabrication of offshore wind turbine monopile structures. In situ neutron diffraction measurements were taken on cross-weld test samples at room temperature to monitor the evolution of intergranular strains under static and cyclic loading conditions. Both static and cyclic test results have shown that the {200} orientation exhibits the least load carrying capacity while {211} had the maximum stiffness. The hkl-specific response predicted using Reuss and Kröner model were found to agree well with experimental values obtained for the heat-affected zone for all the orientations; however, discrepancies between the experimental and model predictions have been observed for the base metal and weld metal. Moreover, the microstructural differences between the weld metal and heat-affected zone resulted in the maximum elastic–plastic strain mismatch at the interface of the two regions. The results from this experiment would be useful to understand the role of crystal-specific microstrains and lattice deformation on fatigue and fracture behavior of thick-walled monopile weldments

Communicative dynamics of artistic collaboration

In his 2001 writings on artistic collaboration, art theorist Charles Green describes how some artistic duos and teams developed a ‘phantom’ element— a ‘third hand’ or collaborative identity independent from and yet related to the individual identities and voices of the artistic collaborators involved. This thesis examines communicative interaction characteristic of these types of collaborations in order to explore this phantom element: what it means, what it is, how it develops and its relationship to the artistic collaborators. Ultimately, it investigates how artists can develop a collaborative author through persistent dialogue and communicative interaction. Focusing on the communicative dynamics of collaborative art practices, the first part of this study illustrates how collaboration reworks conventional notions of authorship. Integrating communication theory and group studies, it then analyses different applications of the term collaboration in contemporary art theory, challenging writings that indiscriminately categorise a variety of participatory activities and roles as collaborative. In doing so, this research examines different types of collaborative relationships; it investigates the conditions necessary for collaborative communication to produce collaborative authorship, outlining various defining characteristics of collaboration. The final portion of this study focuses on collaborative situations in which all of these defining characteristics are met. Using semiotic and hermeneutic phenomenological frameworks, it traces the development of a collective consciousness, collective identity and collective voice. Incorporating research obtained through naturalistic enquiry and questionnaires, it examines how prolonged communication, shared ownership and shared decision-making contribute to the development of these collective entities, leading up to the establishment of a collaborative author. An accompanying DVD and booklet documents the practice-based portion of this investigation— Nomadics, a nine-month multi-media artistic collaboration. The DVD not only evidences the physical art installation that resulted from the collaboration, but also the collaborative practice, providing specific examples to help support claims made within the body of the thesis.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Texture analysis with a time-of-flight neutron strain scanner

A time-of-flight (TOF) neutron strain scanner is a white-beam instrument optimized to measure diffractograms at precise locations within bulky specimens, typically along two perpendicular sample orientations. Here, a method is proposed that exploits the spatial resolution (∼1 mm) provided by such an instrument to determine in a nondestructive manner the crystallographic texture at selected locations within a macroscopic object. The method is based on defining the orientation distribution function (ODF) of the crystallites from several incomplete pole figures, and it has been implemented on ENGIN-X, a neutron strain scanner at the ISIS facility in the UK. This method has been applied to determine the texture at different locations of Al alloy plates welded along the rolling direction and to study a Zr2.5%Nb pressure tube produced for a CANDU nuclear power plant. For benchmarking, the results obtained with this instrument for samples of ferritic steel, copper, Al alloys and Zr alloys have been compared with measurements performed using conventional X-ray diffractometers and more established neutron techniques. For cases where pole figure coverage is incomplete, the use of TOF neutron transmission measurements simultaneously performed on the specimens is proposed as a simple and powerful test to validate the resulting ODF.Fil: Malamud, Florencia. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Santisteban, Javier Roberto. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vicente Alvarez, Miguel Angel. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bolmaro, Raul Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Kelleher, Joe. ISIS Neutron and Muon Source; Reino UnidoFil: Kabra, Saurabh. ISIS Neutron and Muon Source; Reino UnidoFil: Kockelmann, Winfried. ISIS Neutron and Muon Source; Reino Unid