The Experts below are selected from a list of 39 Experts worldwide ranked by ideXlab platform
K T Ramesh - One of the best experts on this subject based on the ideXlab platform.
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multi scale defect interactions in high rate brittle material failure part i model formulation and application to alon
Journal of The Mechanics and Physics of Solids, 2016Co-Authors: Andrew L. Tonge, K T RameshAbstract:Abstract Within this two part series we develop a new material model for ceramic protection materials to provide an interface between microstructural parameters and bulk continuum behavior to provide guidance for materials design activities. Part I of this series focuses on the model formulation that captures the strength variability and strain rate sensitivity of brittle materials and presents a statistical approach to assigning the local flaw distribution within a specimen. The material model incorporates a Mie–Gruneisen equation of state, micromechanics based damage growth, granular flow and dilatation of the highly damaged material, and Pore Compaction for the porosity introduced by granular flow. To provide initial qualitative validation and illustrate the usefulness of the model, we use the model to investigate Edge on Impact experiments ( Strassburger, 2004 ) on Aluminum Oxynitride (AlON), and discuss the interactions of multiple mechanisms during such an impact event. Part II of this series is focused on additional qualitative validation and using the model to suggest material design directions for boron carbide.
Andrew L. Tonge - One of the best experts on this subject based on the ideXlab platform.
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multi scale defect interactions in high rate brittle material failure part i model formulation and application to alon
Journal of The Mechanics and Physics of Solids, 2016Co-Authors: Andrew L. Tonge, K T RameshAbstract:Abstract Within this two part series we develop a new material model for ceramic protection materials to provide an interface between microstructural parameters and bulk continuum behavior to provide guidance for materials design activities. Part I of this series focuses on the model formulation that captures the strength variability and strain rate sensitivity of brittle materials and presents a statistical approach to assigning the local flaw distribution within a specimen. The material model incorporates a Mie–Gruneisen equation of state, micromechanics based damage growth, granular flow and dilatation of the highly damaged material, and Pore Compaction for the porosity introduced by granular flow. To provide initial qualitative validation and illustrate the usefulness of the model, we use the model to investigate Edge on Impact experiments ( Strassburger, 2004 ) on Aluminum Oxynitride (AlON), and discuss the interactions of multiple mechanisms during such an impact event. Part II of this series is focused on additional qualitative validation and using the model to suggest material design directions for boron carbide.
Kazuro Hirahara - One of the best experts on this subject based on the ideXlab platform.
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interseismic Pore Compaction suppresses earthquake occurrence and causes faster apparent fault loading
Geophysical Research Letters, 2009Co-Authors: Yuta Mitsui, Kazuro HiraharaAbstract:[1] Physical and chemical processes operating on faults during interseismic periods are important for earthquake generation. In this study, we focus on Pore Compaction within fault zones driven by chemical kinetic effects. One established model of Compaction causes an increase of Pore fluid pressure almost linearly with time, if fluid diffusion is neglected. We introduced it into a simple numerical model for earthquake cycles and found that this effect can drastically change the recurrence of earthquakes: (1) It gradually stabilizes the fault and eventually suppresses earthquake occurrence (2) It surprisingly causes faster “apparent” fault loading. Furthermore, we developed an expression for the “apparent” loading velocity and checked that it is consistent with the results of numerical calculations. We also extended the expression for the “apparent” loading velocity to include the effect of Pore dilatancy. This “apparent” loading would not only appear in a simple elastic system with a single degree of freedom, but also in complicated systems that involve simulations of realistic earthquake cycles.
T Berstad - One of the best experts on this subject based on the ideXlab platform.
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numerical predictions of ballistic limits for concrete slabs using a modified version of the hjc concrete model
International Journal of Impact Engineering, 2008Co-Authors: M Polancoloria, Odd Sture Hopperstad, T Borvik, T BerstadAbstract:Abstract Some modifications to the Holmquist–Johnson–Cook (HJC) model (1993) for concrete under impact loading conditions are proposed. First, the pressure-shear behaviour is enhanced by including the influence of the third deviatoric stress invariant to take into account the substantial shear strength difference between the tensile and compressive meridians. Second, the modelling of strain-rate sensitivity is slightly changed so that the strain-rate enhancement factor goes to unity for zero strain rate. Third, three damage variables describing the tensile cracking, shear cracking and Pore Compaction mechanisms are introduced. A critical review of the constitutive model with alternative proposals for parameter identification is given. The model parameters are obtained for two concrete qualities, and perforation of concrete slabs is considered numerically and compared with experimental results from the literature. Ballistic limit assessments with deviations under 8% when compared to the experimental results are obtained, indicating that the modified version of the HJC concrete model represents a good compromise between simplicity and accuracy for large-scale computations of concrete plates impacted by projectiles.
D A Shockey - One of the best experts on this subject based on the ideXlab platform.
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micromechanical model for comminution and granular flow of brittle material under high strain rate application to penetration of ceramic targets
International Journal of Impact Engineering, 1993Co-Authors: D.r. Curran, L Seaman, T. Cooper, D A ShockeyAbstract:Abstract Under sufficiently energetic attack by penetrators or explosives, brittle materials are comminuted and forced into large strain divergent flow, deforming non-elastically by sliding and ride-up of fragments, with accompanying competition between dilatancy and Pore Compaction. This paper describes a micromechanical model of such deformation with application to penetration of thick ceramic targets. The model was used in parametric finite element code calculations of the penetration of an eroding, long tungsten rod into a target package consisting of a thick aluminum nitride plate confined in steel. The calculations successfully exhibited the key generic features commonly observed experimentally, including the formation of a comminuted ceramic region around the eroding penetrator nose, dilatant expansion of comminuted material into the region behind the penetrator, and conical fractures radiating outward from this region into the intact material. The most important ceramic properties that govern the depth of penetration were inferred to be the friction between comminuted granules, the unconfined compressive strength of the intact material and the Compaction strength of the comminuted material. However, further work is needed to define the relative importance of the properties of the comminuted and intact material.