scholarly journals An evaluation of constitutive relations for high-rate material behaviour using the tensile Hopkinson-bar

1994 ◽  
Vol 04 (C8) ◽  
pp. C8-477-C8-482 ◽  
Author(s):  
J. P. Noble ◽  
J. Harding
Keyword(s):  
Constitutive Relations ◽  
Hopkinson Bar ◽  
High Rate ◽  
Material Behaviour

scholarly journals Bertram Hopkinson's pioneering work and the dislocation mechanics of high rate deformations and mechanically induced detonations

2014 ◽  
Vol 372 (2015) ◽  
pp. 20130181 ◽  
Author(s):  
Ronald W. Armstrong
Keyword(s):  
Constitutive Relations ◽  
Shear Banding ◽  
High Rate ◽  
Hopkinson Pressure Bar ◽  
Isentropic Compression ◽  
Impact Tests ◽  
Dislocation Mechanics ◽  
Pressure Bar ◽  
High Rate Deformation

Bertram Hopkinson was prescient in writing of the importance of better measuring, albeit better understanding, the nature of high rate deformation of materials in general and, in particular, of the importance of heat in initiating detonation of explosives. This report deals with these subjects in terms of post-Hopkinson crystal dislocation mechanics applied to high rate deformations, including impact tests, Hopkinson pressure bar results, Zerilli–Armstrong-type constitutive relations, shock-induced deformations, isentropic compression experiments, mechanical initiation of explosive crystals and shear banding in metals.

The effect of particle size on microstructure, relative density and indentation load of Mg-B4C composites fabricated at different loading rates

2019 ◽  
Vol 54 (17) ◽  
pp. 2297-2311 ◽  
Author(s):  
K Rahmani ◽  
GH Majzoobi
Keyword(s):  
Particle Size ◽  
Relative Density ◽  
Loading Rate ◽  
Hopkinson Bar ◽  
Maximum Load ◽  
Indentation Load ◽  
High Rate ◽  
Split Hopkinson Bar ◽  
Indentation Tests ◽  
Split Hopkinson

The effect of reinforcing particle size on microstructure, relative density and indentation of Mg reinforced by 0, 1.5, 3, 5 and 10% volume fractions of nano- and micro-sized B4C was investigated. The composites were fabricated through powder compaction technique at strain rates of 1.6 × 103 s−1, 8 × 102 s−1 and 8×103 s−1 using split Hopkinson bar, drop hammer and Instron, respectively. The results indicated that the size of B4C and loading rate had significant effect on relative density. For example, the relative density of Mg-10 vol.% B4C nanocomposite was around 2.5% higher than that of its corresponding microcomposites. The relative density of the samples produced at high rate of loading was in average 1.2% higher than that of the samples fabricated quasi-statically. The results of indentation tests on the produced nanocomposite and microcomposite samples also revealed that loading rate and B4C particle size had significant effect on strength of specimens. For example, for Mg-5 vol.% B4C, the maximum load in load–depth curve of the specimens produced by split Hopkinson bar increased from 530 N for micron-sized B4C to 780 N for nano-sized B4C, around 45% improvement. Moreover, nanocomposites had better indentation resistance compared to similar micro composites fabricated using the three methods.

The use of the Hopkinson bar to validate constitutive relations at high rates of strain

1999 ◽  
Vol 47 (5) ◽  
pp. 1187-1206 ◽  
Author(s):  
J.P. Noble ◽  
B.D. Goldthorpe ◽  
P. Church ◽  
J. Harding
Keyword(s):  
Constitutive Relations ◽  
Hopkinson Bar

High Strain Rate Torsion and Bauschinger Tests on Ti6Al4V

2012 ◽  
Vol 706-709 ◽  
pp. 774-779 ◽  
Author(s):  
Jan Peirs ◽  
Patricia Verleysen ◽  
Kim Verbeken ◽  
Frederik Coghe ◽  
Joris Degrieck
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Kinematic Hardening ◽  
Hopkinson Bar ◽  
Image Correlation ◽  
Material Behaviour ◽  
Split Hopkinson Bar ◽  
Strain And Strain Rate ◽  
Split Hopkinson

An accurate isotropic and kinematic hardening model and description of the strain rate dependent material behaviour is necessary for simulation of fast forming processes. Consequently, the material model parameter identification requires experiments where large strains, high strain rates and strain path changes can be attained. Usually, quasi-static tension-compression Bauschinger tests are used to assess the materials kinematic hardening. Hereby it’s important to have the same specimen geometry and boundary conditions in the forward and reverse loading step which is not easily achieved in high strain rate testing techniques. In this work, high strain rate split Hopkinson bar torsion experiments on Ti6Al4V are carried out to study the constitutive material behaviour at large plastic strain and strain rate. In torsion experiments, due to the absence of cross sectional area reduction, higher strains than in tensile tests can be obtained. In addition, a modified torsional split Hopkinson bar setup is developed to perform dynamic Bauschinger tests. A shear reversed-shear load is applied instead of the classical tension-compression load cycle. The test results are analysed to find out if the technique can be used for characterisation of the kinematic material behaviour. Digital image correlation and finite element simulations are used to improve the interpretation of the experimental results.

High rate material behaviour at hot forming conditions

2008 ◽  
Vol 13 (1) ◽  
pp. 49-62 ◽  
Author(s):  
Lothar W. Meyer ◽  
Corinna Kuprin ◽  
Thorsten Halle
Keyword(s):  
High Rate ◽  
Hot Forming ◽  
Material Behaviour

Structure of Palladium Single-Crystal Films Prepared by Flash Evaporation onto (001) NaCl Substrates

1970 ◽  
Vol 28 ◽  
pp. 456-457
Author(s):  
L. E. Murr ◽  
G. Wong
Keyword(s):  
Single Crystal ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
High Rate ◽  
Flash Evaporation ◽  
Optimum Load ◽  
Single Crystal Films ◽  
Crystal Films ◽  
A Current

Palladium single-crystal films have been prepared by Matthews in ultra-high vacuum by evaporation onto (001) NaCl substrates cleaved in-situ, and maintained at ∼ 350° C. Murr has also produced large-grained and single-crystal Pd films by high-rate evaporation onto (001) NaCl air-cleaved substrates at 350°C. In the present work, very large (∼ 3cm2), continuous single-crystal films of Pd have been prepared by flash evaporation onto air-cleaved (001) NaCl substrates at temperatures at or below 250°C. Evaporation rates estimated to be ≧ 2000 Å/sec, were obtained by effectively short-circuiting 1 mil tungsten evaporation boats in a self-regulating system which maintained an optimum load current of approximately 90 amperes; corresponding to a current density through the boat of ∼ 4 × 104 amperes/cm2.

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