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Modelling the long-term deformation behaviour of polymers for finite element analysis.

Dean, G D; McCartney, L N; Crocker, L E; Mera, R D (2008) Modelling the long-term deformation behaviour of polymers for finite element analysis. NPL Report. MAT 22

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Creep studies have been carried out under tension, compression and shear on two grades of poly(oxymethylene) supplied by Du Pont and Ticona. Measurements under tension have been modelled using a function with 4 material parameters. One of these parameters, related to a mean retardation time for the relaxation process responsible for creep, decreases with increasing stress and this gives rise to non-linear creep behaviour. Measurements of creep under compression and shear have enabled the model to be adapted to include the influence of the stress state.
In order for the model to be implemented in a finite element system, theoretical methods have been explored for using creep data to predict long-term deformation behaviour under situations where the stress varies with time. This is not straightforward when creep deformation is non-linear. An expression has been proposed for achieving this under a uniaxial tensile stress, and has been evaluated using experimental tests where the stress is increased or decreased in discrete steps. Solutions have also been obtained for changes in stress under a specified strain history from which good agreement has been obtained between the prediction of stress relaxation behaviour and experimental results.

Item Type: Report/Guide (NPL Report)
NPL Report No.: MAT 22
Keywords: Creep, non-linear, model, finite element analysis
Subjects: Advanced Materials
Advanced Materials > Materials Modelling
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/4206

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