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Speckle pattern control in the application of digital image correlation for detecting damage in helmets.

Matthews, Scott J.C. (2020) Speckle pattern control in the application of digital image correlation for detecting damage in helmets. Doctoral thesis, University of Surrey.

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Throughout use, military equipment is subjected to everyday wear and tear. Some may be significant in its own right, some will interact with other damage, and some will fatigue with use. Under these circumstances, how will equipment that has been in the field deal with an actual ballistic event, or other primary duty issue? Current assessment methodologies ensure safety standards are met, but detailed evaluation of components requires transportation from site. Minimising transport of equipment would reduce costs and fuel usage, and also save lives. The current work considers the use of digital image correlation (DIC) for non-destructive evaluation (NDE), with a particular focus on the assessment of combat helmets. To optimize component loading, the use of pressure differentials and single-point mechanical loading were trialed. Finite element analysis (FEA) suggests pressure differentials produce a greater likelihood for the detection of component damage via surface strain discontinuities. By contrast, single point loading produces highly concentrated strain in the region of contact, whilst minimal strains result for the rest of the component. The optimization of component speckling has also been considered, leading to the development of a novel approach using customisable transfer paper, which can be printed with a pattern specific to a given test geometry. This allows greater standardization, faster application, and increased accuracy, compared with traditional approaches, such as spray painting a speckle pattern. Following these experiments, NDE of an entire military helmet was investigated using a portable test rig. With the method for helmet loading in concept stage, proof that the technique can detect damage is presented via five case studies. The variety of materials and testing processes show the novel approach for component speckling has direct use for the completion of, and external to, the primary goal of the project: “to develop a DIC technique with the potential for portable damage detection of helmets”.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Matthews, Scott J.C.0000-0002-5890-2416
Date : 30 April 2020
Funders : RCUK, ESPRC
DOI : 10.15126/thesis.00853892
Contributors :
Depositing User : Scott Matthews
Date Deposited : 19 May 2020 10:53
Last Modified : 02 Jun 2020 11:51

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