High strain rate testing of metals
File(s)
Author(s)
Worley, Alexander
Type
Thesis
Abstract
Tensile and compressive tests were carried out on a selection of metals of interest
in engineering applications. These metals were tested at a range of strain rates
and temperatures with the aim of calibrating material constitutive models for the
simulation of full scale structures in industry. In order to validate these models for
use under conditions of strain rates exceeding those imposed by the tests which
were used for calibration of the models, both tensile and compressive ballistic
tests were carried out. A ball on plate experiment was used to compare the
deformation predicted under the tensile conditions, including high speed speckle
DIC for out of plane displacement measurement. A bespoke gas gun for the
purpose of carrying out Taylor impact tests on samples of the same materials
was designed and installed at Imperial College. The gas gun was used to carry
out Taylor tests which were also lmed at high speed for comparison with tests
simulated under compressive loading. Furthermore, post-impact samples were
sectioned so that a hardness survey could be carried out across the internal section
of a sample. These data were combined to produce a map indicative of plastic
strain within the sample and used as another validation tool for the model using
the Taylor test. It was found that the Johnson-Cook model was not su cient
to represent the materials at the conditions under study. Both the ball on plate
and Taylor test comparisons revealed the discrepancy between the model and the
actual material response. Furthermore, the hardness map of the post test Taylor
cylinders revealed that a volume within the cylinder at the base of the bulge
experienced less hardening than the volume around it, consistent with predictions
made from the nite element analysis.
in engineering applications. These metals were tested at a range of strain rates
and temperatures with the aim of calibrating material constitutive models for the
simulation of full scale structures in industry. In order to validate these models for
use under conditions of strain rates exceeding those imposed by the tests which
were used for calibration of the models, both tensile and compressive ballistic
tests were carried out. A ball on plate experiment was used to compare the
deformation predicted under the tensile conditions, including high speed speckle
DIC for out of plane displacement measurement. A bespoke gas gun for the
purpose of carrying out Taylor impact tests on samples of the same materials
was designed and installed at Imperial College. The gas gun was used to carry
out Taylor tests which were also lmed at high speed for comparison with tests
simulated under compressive loading. Furthermore, post-impact samples were
sectioned so that a hardness survey could be carried out across the internal section
of a sample. These data were combined to produce a map indicative of plastic
strain within the sample and used as another validation tool for the model using
the Taylor test. It was found that the Johnson-Cook model was not su cient
to represent the materials at the conditions under study. Both the ball on plate
and Taylor test comparisons revealed the discrepancy between the model and the
actual material response. Furthermore, the hardness map of the post test Taylor
cylinders revealed that a volume within the cylinder at the base of the bulge
experienced less hardening than the volume around it, consistent with predictions
made from the nite element analysis.
Version
Open Access
Date Issued
2015-08
Date Awarded
2016-02
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Dear, John
Hooper, Paul
Sponsor
Atomic Weapons Establishment (Great Britain)
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)