- Title
- Neutron strain tomography
- Creator
- Gregg, Alexander W. T.
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2020
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- This thesis by publication concerns the development and demonstration of algorithms to perform strain tomography; full-field reconstruction of the elastic strain tensor from neutron measurements, in a manner analogous to density reconstruction from medical computed tomography (CT). Strain tomography has the potential to significantly impact the way experimental mechanics is carried out. This technique has obvious application in the characterisation of residual stresses in conventionally manufactured components (e.g. those that are laser-clad [1], welded [2], cast [3], rolled [4] and forged [5]), but may also aid in the development of novel manufacturing techniques, such as metal additive manufacturing, where the printing process can lock-in residual strains that can have a profound impact on the effective strength and service life of components [6]. These effects must be understood to advance the technology. Strain can be measured by a number of techniques, varying in accuracy, precision and destructivity. This thesis primarily concerns neutron diffraction-based approaches, which, for crystalline samples, can provide non-contact measurements of elastic strain deep within the bulk of engineering materials. For many years, both 'point-wise' and through-thickness measurements of strain have been possible using neutrons — the latter relying on Bragg-edge analysis and providing an average normal strain measurement over the illuminated path of the neutron beam. Over the past decade, advances in instrument and detector technology have allowed for Bragg-edge neutron transmission strain imaging, where hundreds of thousands of these through- thickness transmission strain measurements can be performed simultaneously and a high-resolution strain image constructed with a single exposure of a sample. This thesis contributes a number of significant contributions to the Bragg-edge neutron strain tomography problem — reconstruction of the full strain tensor field from these images: 1. The development and experimental validation of algorithms for full-field strain reconstruction in special cases (e.g. systems without eigenstrain — in-situ loadings only). 2. The development and experimental validation of the first algorithms for (general) residual strain reconstruction in the axisymmetric and 2D domains. 3. The development and experimental validation of an algorithm for 3D residual strain — the most general form of the problem. Near the end of the project, progress was also made toward a strain tomography algorithm for conventional neutron strain diffractometers. With further development, this new technique may also allow strain tomography at the multitude of existing neutron diffraction strain scanners around the world.
- Subject
- strain; strain tomography; Bragg-edge neutron transmission; neutron transmission strain measurement; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1423032
- Identifier
- uon:37894
- Rights
- Copyright 2020 Alexander W. T. Gregg
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 6 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 210 KB | Adobe Acrobat PDF | View Details Download |