| Compression mechanical properties of Zirconium under different temperature and different strain rates were studied by MTS and split Hopkinson pressure bar(SHPB) apparatus.Small SHPB tests was used to investigate mechanical properties under high rates.Two-dimensional effects would be brought into small specimen SHPB tests,and this effect was mainly elastic indentation of the bar's interface with the specimen.The two-dimensional effects decreased rapidly,when the specimen developed into plastic deformation stage.The influence could be eliminated efficiently by mounting strain gauges in series or far away from the specimen-bar interfaces in the eccentric compression tests.Also,a distortional signal would be recorded when a bent bar was used in test.It's found that the amplitude of distortion increases with the increasing bending.A limiting condition for bent bar in Hopkinson bar tests was presented.Also, these difficulties were evaluated and testified by numerical simulations and some experiments.The experiment system of high temperature split Hopkinson pressure bar (SHPB)by adding ceramic platens between bars and specimen was investigated in this paper,which is suitable for measuring the dynamic response of metals at 1073K. The influence of ceramic platens and temperature field was analyzed.Compression experiments on the HP-Zr were carried out in a temperature range of 298K-1073K and a strain rate range of 10-4s-1-2800s-1.Results indicated that:The stress～strain curves show an unusual strain hardening behavior,flow stress and strain hardening increased with the increasing strain rate,and decreased with the increasing temperature.Macroscopic ductile cracking at 45°to the compression axis is seen for large deformation tests.The failure strain of single large deformation test was the same as that of small strain reloading tests.Optical micrographs show that the twinning increased with an increase in strain and strain rates,and decreased rapidly with the increasing temperature.The cylindrical compression specimens failed by adiabatic shearing bands(ASB).In small deformation stage,the twinning density increased with the increasing strain;further more,the interactions between twins, grain boundry and slip band,many micro-twins were seen;adiabatic shearing bands were seen in large deformation specimens,the twins bowed toward to the shearing bands.SEM graphs of failure surface appeared typical shearing rupture characteristics. The strain hardening of stress～strain curves coincided with the twinning development in specimen during deformation,the ASB might be caused by in-homogeneity of twinning orientations.A constitutive model based on the dislocation kinetics was used to describe the stress-strain relationship of HP-Zr at the investigated temperatures and strain rates.Furthermore,a modification incorporating the twinning effect was applied to the model.The correlations between the simulated curves and the experimental results are in good agreement,except for the conditions in which developing twins play an important role.With the interface of LS-DYNA and the theory of plastic constitutive relation,the constitutive model based on the dislocation kinetics was used to study the dynamic failure of metallic tube of SHPB tests and the process of deformation and failure of cylinder shells subjected to internal sliding explosion.The time curves of the stress, temperature and damage were given,which would gave reference to the test.The final part is the summary of the paper and the prospect of the future work.
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