Micromechanical Considerations in Shock Compression of Solids

Johnson, J. N.

doi:10.1007/978-1-4612-0911-9_7

Cited by 10 publications

(5 citation statements)

References 58 publications

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“…In the context of deformation by motion of dislocations, dislocation transport could be included in a variety of ways. Researchers have previously pointed to the need to consider dislocation transport for non-local phenomena in the context of dynamically loaded materials [47]. Dislocation flux can be modeled by directly accounting for the transport of specific families of dislocations, and there are approaches which account for flux at a coarser scale using descriptors based on net burgers vector content.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Defect evolution and pore collapse in crystalline energetic materials

Barton¹,

Winter²,

Reaugh³

2009

Modelling Simul. Mater. Sci. Eng.

137

103

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This work examines the use of crystal based continuum mechanics in the context of dynamic loading. In particular, we examine model forms and simulations which are relevant to pore collapse in crystalline energetic materials. Strain localization and the associated generation of heat are important for the initiation of chemical reactions in this context. The crystal mechanics based model serves as a convenient testbed for the interactions among wave motion, slip kinetics, defect generation kinetics and physical length scale. After calibration to available molecular dynamics and single crystal gas gun data for HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), the model is used to predict behaviors for the collapse of pores under various conditions. Implications for experimental observations are discussed.

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Section: Discussionmentioning

confidence: 99%

“…Such mechanisms are not included in the model here. As in other models of energetic materials [13,47] we consider the rapid generation of dislocation density which can occur behind a nominally elastic precursor wave [48], here in the context of crystal mechanics. The dislocation density evolves according to…”

Section: Slip and Dislocation Density Kineticsmentioning

confidence: 99%

Defect evolution and pore collapse in crystalline energetic materials

Barton¹,

Winter²,

Reaugh³

2009

Modelling Simul. Mater. Sci. Eng.

137

103

View full text Add to dashboard Cite

show abstract

“…The effect of the Hugoniots of the flyer plates will have an effect since different over-driven states can be reached even when the equilibrium final state is the same. Johnson [45] has pointed out that strong shear states exit in the shock fronts that create defects. These defects can be nucleation centers for new phases that will change transition rates.…”

Section: Kinetics Of Plastic I Shock Decaymentioning

confidence: 99%

First-Order Polymorphic and Melting Phase Transitions Under Shock Loading

Forbes

2012

Shock Wave Compression of Condensed Matter

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Some materials at high pressure have structural arrangements of atoms and molecules that are at a lower energy state than that at (P ¼ 0, v o , T-293 K) conditions. When this occurs a thermodynamic force on the material exists to change the configuration to the new one. This process is called a first-order phase transition that is characterized by the coexistence of several thermodynamic phases. It is well established that condensed matter can also undergo thermodynamic second order phase transitions in electric and magnetic properties that are not treated in this book. Readers interested in second order phase transitions seen in dynamic experiments consult the literature especially the articles by Keeler and Royce [1].Static studies of phase transitions provide the baseline for understanding many phase transitions. They can show if the mixed phase region is in thermodynamic equilibrium or in a metastable state. Inferring phase transformations under dynamic loading from experimental static data is very useful. The first order guess of the phase seen in dynamic experiments will be the same as observed in static experiments but this needs to be verified in real-time dynamic experiments. One must keep in mind that under dynamic loading, phases other than that seen in static experiments are a possibility. This was seen in a recent study of shocked polycrystalline iron [2] where fcc phases occurred in certain oriented crystal grains. Note that this shock study using intense x-rays directly confirmed experimentally the majority of the iron transition was martensitic in nature, which agrees with static studies.The kinetics of the transformation determines whether a new configuration occurs under shock loading. If the transformation takes many microseconds to occur it will not be seen in standard shock wave experiments and the material will be put into a thermodynamic metastable state. Since dynamic loading is different than static compression some transitions that require cooperative lattice motion can be accelerated due to the shear in a shock wave. This is what happens in the body center cubic (bcc or a) to hexagonal closed packed (hcp or ɛ) lattice transition in iron [3] at 130 kbar. Keep in mind that due to creation of defects,

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“…Nevertheless, GB structure has not been considered in detail in understanding and modeling of the shock and spall responses of materials. Also, hydrodynamic modeling of shock and spall behavior in materials has traditionally ignored many effects due to heterogeneities such as GBs [8]. By 'spall', we mean shock compression and release-induced fracture of solids.…”

Section: Introductionmentioning

confidence: 99%

Effect of grain boundary structure on plastic deformation during shock compression using molecular dynamics

Fensin

Valone

Cerreta

et al. 2012

Modelling Simul. Mater. Sci. Eng.

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Grain boundaries (GBs) can play an important role in governing the mechanical behavior and damage evolution of a material during both quasistatic and dynamic loading. However, the general consensus of the shock physics community has been that minute details about the GB structure should not affect the response of a material to dynamic loading. In this paper, we present results of molecular-dynamics simulations investigating whether or not small changes in boundary structure are ‘recognized’ by the shock wave and can in turn affect the spall strength of a material. As a test case, we study a Σ11 asymmetric tilt GB in copper with an ordered and a disordered structure. The results are also compared with face-centered-cubic single crystals which correspond to the crystal orientations of the two grains in the bi-crystal. These results show that ordered and disordered boundaries undergo dissimilar amounts of plastic deformation during shock loading, which leads to spall strengths that vary by 12%, likely due to differences in the GB structures.

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Micromechanical Considerations in Shock Compression of Solids

Cited by 10 publications

References 58 publications

Defect evolution and pore collapse in crystalline energetic materials

Defect evolution and pore collapse in crystalline energetic materials

First-Order Polymorphic and Melting Phase Transitions Under Shock Loading

Effect of grain boundary structure on plastic deformation during shock compression using molecular dynamics

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