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.

Dislocation mechanics of copper and iron in high rate deformation tests

2009 ◽  
Vol 105 (2) ◽  
pp. 023511 ◽  
Author(s):  
Ronald W. Armstrong ◽  
Werner Arnold ◽  
Frank J. Zerilli
Keyword(s):  
High Rate ◽  
Dislocation Mechanics ◽  
Deformation Tests ◽  
High Rate Deformation

Simultaneous effects of strain rate and temperature on mechanical response of fabricated Mg–SiC nanocomposite

2019 ◽  
Vol 54 (5) ◽  
pp. 659-668 ◽  
Author(s):  
K Rahmani ◽  
GH Majzoobi ◽  
A Atrian
Keyword(s):  
Strain Rate ◽  
Mechanical Response ◽  
Split Hopkinson Pressure Bar ◽  
High Rate ◽  
Dynamic Tests ◽  
Hopkinson Pressure Bar ◽  
Compaction Temperature ◽  
Static Tests ◽  
Split Hopkinson ◽  
Pressure Bar

Mg–SiC nanocomposite samples were fabricated using split Hopkinson pressure bar for different SiC volume fractions and under different temperature conditions. The microstructures and mechanical properties of the samples including microhardness and stress–strain curves were captured from quasi-static and dynamic tests carried out using Instron and split Hopkinson pressure bar, respectively. Nanocomposites were produced by hot and high-rate compaction method using split Hopkinson pressure bar. Temperature also significantly affects relative density and can lead to 2.5% increase in density. Adding SiC-reinforcing particles to samples increased their Vickers microhardness from 46 VH to 68 VH (45% increase) depending on the compaction temperature. X-ray diffraction analysis showed that by increasing temperature from 25℃ to 450℃, the Mg crystallite size increases from 37 nm to 72 nm and decreases the lattice strain from 45% to 30%. In quasi-static tests, the ultimate compressive strength for the compaction temperature of 450℃ was improved from 123% for Mg–0 vol.% SiC to 200% for the Mg–10 vol.% SiC samples compared with those of the compaction at room temperature. In dynamic tests, the ultimate strength for Mg–10 vol.% SiC sample compacted at high strain rate increased remarkably by 110% compared with that for Mg–0 vol.% SiC sample compacted at low strain rate.

scholarly journals A Simple Rate–Temperature Dependent Hyperelastic Model Applied to Neoprene Rubber

2020 ◽  
Vol 6 (3) ◽  
pp. 336-347
Author(s):  
A. R. Trivedi ◽  
C. R. Siviour
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
High Rate ◽  
Hopkinson Pressure Bar ◽  
Temperature Dependent ◽  
Temperature Superposition ◽  
High Strain Rate Deformation ◽  
Split Hopkinson ◽  
Hyperelastic Model ◽  
Pressure Bar ◽  
Two Parameter

Abstract Rubber is widely used in engineering applications in which it may be subjected to impact loading leading to high strain rate deformation. This resulting deformation may occur at a variety of temperatures, notwithstanding the self-heating of the material. For this reason, it is necessary to study the mechanical behaviour of these materials over a range of loading conditions. The strong rate and temperature dependence of their properties provides a further motivation for this understanding. In this paper, the relationships between the response of a neoprene rubber at various strain rates and temperatures are investigated, and a simple model making use of the time–temperature superposition (TTS) principle proposed to describe the material behaviour. As it is challenging to obtain high rate data on rubbery materials using conventional apparatus, such as the split-Hopkinson pressure bar (SHPB), the simple two parameter hyperelastic model proposed here provides a useful complementary tool to interrogate the response.

Development of a Material Constitutive for High-Rate Using a Combined Experiment/Computation Method

2004 ◽  
Vol 261-263 ◽  
pp. 269-276
Author(s):  
J.F. Lu ◽  
Zhuo Zhuang ◽  
K. Shimamura
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Equivalent Strain ◽  
High Rate ◽  
Computation Method ◽  
Failure Behavior ◽  
Hopkinson Pressure Bar ◽  
Material Constants ◽  
Split Hopkinson ◽  
Pressure Bar

To describe the high-rate behaviour of metals, a revised form of the classic Johnson-Cook strength model with unknown material constants has been used. The 1D stress-strain relations as well as the effects of strain, strain rate and temperature are examined by Split Hopkinson Pressure Bar (SHPB) test. The undetermined material constants are solved using a variable-dissociation method. The element failure criterion based on maximum equivalent strain is also introduced to estimate the material failure behavior under high strain rate. A corresponding user-defined material subroutine (UMAT) has been developed for revised Johnson-Cook model, which is implemented into ABAQUS. Using this implicit scheme, several groups of finite element simulations under different strain rates are completed in ABAQUS/Standard. The results agree well with the test data and other results by explicit code.

scholarly journals On the dynamic and quasi-static shear strength of SLM AlSi10Mg

2021 ◽  
Vol 250 ◽  
pp. 01031
Author(s):  
Ben Amir ◽  
Eytan Kochavi ◽  
Shimon Gruntman ◽  
Yuval Gale ◽  
Shmuel Samuha ◽  
...  
Keyword(s):  
Shear Strength ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Properties ◽  
High Rate ◽  
Dynamic Shear ◽  
Hopkinson Pressure Bar ◽  
Static Mechanical ◽  
Dynamic Shear Strength ◽  
Pressure Bar ◽  
Static Shear

Additive manufacturing by selective laser melting (AM-SLM) is an advanced manufacturing approach in which a structure is fabricated by successive thin powder layers melted by a focused laser beam. The aerospace and automotive sectors are especially interested in the AMSLM technology that enables quick production of complex and customized structures. AlSi10Mg alloy has been found to be applicable to AM-SLM mainly because good cast-ability, strong weldability and low shrinkage during solidification. While many studies on the quasi-static mechanical properties and the structure of SLM AlSi10Mg were published, there is limited published research focused on the dynamic properties of SLM AlSi10Mg under high rate strains. In addition to that, the shear strength of SLM aluminium alloys is rarely investigated. This study presents an investigation of the AM-SLM AlSi10Mg static and dynamic shear strength and its dependency on build direction. Experiments included quasi-static shear experiments performed according to the protocol of ASTM B565, and dynamic shear tests performed using a split Hopkinson pressure bar (SHPB), coupled to innovative punch assembly that generates pure dynamic shear loads on the sample. The design of this sample holder has been validated numerically and an experimentally. The quasi-static experiments revealed that the static shear strength is independent of build direction. In contrast, the dynamic tests demonstrated that the dynamic shear strength of vertically built samples is higher by almost 11% than the shear strength of samples built horizontally. This last phenomenon explained with a suggested mechanism based onelectron microscope fractography.

Quasistatic and Dynamic Compressive Behavior of Gelatin

2010 ◽  
Author(s):  
Jiwoon Kwon ◽  
Ghatu Subhash
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Rate Sensitivity ◽  
Polymeric Materials ◽  
Soft Materials ◽  
High Rate ◽  
Constitutive Behavior ◽  
Hopkinson Pressure Bar ◽  
Property Data ◽  
Split Hopkinson ◽  
Pressure Bar

Gelatin has been extensively used as a tissue stimulant. Determination of properties and tits constitutive behavior is crucial to successful use of gelatin in these applications. In this study, ballistic gelatin was used because the recipe to prepare the gelatin and its quasi-static strength (250 bloom) of this particular type of gelatin is well known [1]. Although the study for high rate deformation is important to understand the damage from blast impact, majority of the currently available material property data is in quasi-static range [2,3]. Generally, polymeric materials (including human tissue) exhibit highly rate sensitive response [4]. Therefore, the understanding of the constitutive behavior for these materials at high rate loading is essential. This study will provide the rate sensitivity of gelatin by comparing the response under quasi-static and dynamic loading. In order to investigate the dynamic behavior of gelatin, the split Hopkinson pressure bar (SHPB) was used in this study. Because use of a solid metallic bar to test such soft materials does not provide an adequate transmitted signal, a polymer split Hopkinson pressure bar (PSHPB) was used to reduce the impedance mismatch between bar and soft gelatin specimen. The nature of dispersion and attenuation was corrected using an iterative scheme developed earlier [5].

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