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Project PAJ2: Report No. 6, Project CAM6: Report No. 4.

Duncan, B C (1998) Project PAJ2: Report No. 6, Project CAM6: Report No. 4. NPL Report. CMMT(A)109

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This interim report summarises progress on the development of an extensometer for measuring strain at high rates of strain. It details progress on developing a high speed linescan camera system. This work forms part of milestones 2/3 on project PAJ2 and milestones 2/3 on project CAM6 that are concerned with the acquisition and analysis of mechanical design data for impact loading of adhesives and plastics.
The measurement of mechanical data at high rates is a specialised and difficult process. Accurate strain measurements are needed to obtain the accurate materials data required by computer aided design systems. Commercial apparatus to measure strain at high rates is limited in capability and expensive. As part of the MTS project, work has been directed at developing an alternative and less expensive method for strain measurement. A linescan camera, which combines both acceptable linear resolution and high data capture rates, was identified as a potential high speed extensometer. An EG&G Reticon linescan camera with a 2000 element detector and scan rate of up to 10,000 lines per second has been purchased and interfaced with a personal computer. Prototype software has been written to control the camera, analyse and locate the edges of gauge marks and store data.
Initial measurements have demonstrated that the linescan camera can function adequately as an extensometer. Tensile stress-strain curves for polypropylene specimens were measured at strain rates up to 2 s -1 , which is the upper rate for conventional extensometers. They are in reasonable agreement with the conventional extensometry data. Some technique development has been performed and further work will be undertaken in these projects with the aim of enabling the extensometer to be used more routinely and reliably as a measurement instrument.

Item Type: Report/Guide (NPL Report)
NPL Report No.: CMMT(A)109
Subjects: Advanced Materials
Advanced Materials > Adhesives
Advanced Materials > Polymers
Last Modified: 07 Sep 2018 14:32
URI: http://eprintspublications.npl.co.uk/id/eprint/975

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