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|Title: ||Behaviour of metals as a function of strain rate and temperature|
|Authors: ||Ashton, Mark|
|Issue Date: ||1999|
|Publisher: ||© Mark Ashton|
|Abstract: ||Five materials, copper (two versions), iron, and armour plate steel (two versions)
have been tested at different strain-rates and temperatures. All tests were in compression.
The materials were studied to provide experimental data for input into hydrocode models
of armour behaviour by the Defence Research Agency, Fort Halstead. A wide selection
of metals was examined so that comparisons could be drawn between modelling the
behaviour of face centred and body centred cubic metals, and to carry out a broader
investigation into how the results obtained were affected by the test methods.
Experiments were performed at temperatures from -100°C to 20°C and mean
plastic strain-rates from 10-3 to 103 S-l, using a Split Hopkinson Pressure Bar (SHPB)
system for high strain-rates and a Hounsfield 50 kN machine for quasistatic conditions.
The stress-strain behaviour of the materials as a function of temperature and strain-rate
was then determined.
The effects of interfacial friction on the measured compreSSlve properties of
copper and the armour plate steels have been investigated. Since the coefficient of
friction was the critical parameter, ring tests were carried out and the Avitzur analysis
applied. In general, the coefficient of friction decreased with increasing strain-rate and
temperature. The tested specimen's appearance indicated the same friction trends.
Hydrocode modelling of the SHPB system produced corrections to the flow
stress, to compensate for interfacial friction, that agree well with those predicted by the
Avitzur analysis. Deformed finite element mesh plots analysed in conjunction with
barrelled specimens have given a clearer insight into the mechanisms of interfacial
The Armstrong-Zerilli constitutive models have been applied to copper, iron and
armour plate steel results corrected for thermal softening and specimen-platen interfacial
friction. These models have been shown to provide a reasonable description of the
The research investigation has shown that in order to obtain fundamental stressstrain
behaviour of the materials, then corrections must be applied, which can be quite
significant. These corrections must take into account the effects of material thermal
softening and the specimen-platen interfacial friction.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Physics)|
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