Evolution of shock compression pulses in polymethylmethacrylate and aluminum

Popova, Tatiana; Mayer, Alexander E.; Khishchenko, K. V.

doi:10.1063/1.5029418

Cited by 31 publications

(7 citation statements)

References 41 publications

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“…Previously, the dislocation plasticity model [39] was improved in [43] by means of a more enhanced dislocation kinetics, which considers immobilized dislocations besides the mobile ones. It allows one to describe the structure of release waves following the shock wave in both the full statement with the Orowan equation for the plastic strain rate [43][44][45] and in the reduced model [46] based on the concept of relaxation time dependent on the dislocation density [47]. A 2D version of the model supplemented by submodel of mechanical twinning was successfully used in [24] for calculation of the Taylor impact tests in comparison with the experimental data from the literature.…”

Section: Introductionmentioning

confidence: 99%

Taylor Impact Tests with Copper Cylinders: Experiments, Microstructural Analysis and 3D SPH Modeling with Dislocation Plasticity and MD-Informed Artificial Neural Network as Equation of State

Rodionov

Lupanov

Grachyova

et al. 2022

Metals

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Taylor impact tests involving the collision of a cylindrical sample with an anvil are widely used to study the dynamic properties of materials and to test numerical methods. We apply a combined experimental-numerical approach to study the dynamic plasticity of cold-rolled oxygen-free high thermal conductivity OFHC copper. In the experimental part, impact velocities up to 113.6 m/s provide a strain up to 0.3 and strain rates up to 1.7 × 104 s−1 at the edge of the sample. Microstructural analysis allows us to find out pore-like structures with a size of about 15–30 µm and significant refinement of the grain structure in the deformed parts of the sample. In terms of modeling, the dislocation plasticity model, which was previously tested for the problem of a shock wave upon impact of a plate, is implemented in the 3D case using the numerical scheme of smoothed particle hydrodynamics (SPH). The model includes an equation of state implemented in the form of an artificial neural network (ANN) and trained according to molecular dynamics (MD) simulations of uniform isothermal stretching/compression of representative volumes of copper. The dislocation friction coefficient is taken from previous MD simulations. These two efforts are aimed at building a fully MD-based material model. Comparison of the final shape of the projectile, the reduction of the sample length and increase in the diameter of the impacted edge of the sample confirm the applicability of the developed model and allow us to optimize the model parameters for the case of cold-rolled OFHC copper.

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Section: Introductionmentioning

confidence: 99%

Taylor Impact Tests with Copper Cylinders: Experiments, Microstructural Analysis and 3D SPH Modeling with Dislocation Plasticity and MD-Informed Artificial Neural Network as Equation of State

Rodionov

Lupanov

Grachyova

et al. 2022

Metals

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“…Previously, we used explicit dislocation kinetics-based models of the plastic flow [35,36]. Here we employ the following equation taken from [46] for the plastic strain rate in the vicinity of i-th pore:…”

Section: Fracture Modelmentioning

confidence: 99%

“…where H(σ) is the Heaviside step function. Equation ( 9) expresses the modified Maxwell relaxation model with accounting of the yield strength Y like in [35,46]. In contrast to [35,46], both the yield strength Y and the relaxation time τ are treated as constants and directly optimized to reach the correspondence with the MD, as described in Section 2.3.…”

Section: Fracture Modelmentioning

confidence: 99%

“…Equation ( 9) expresses the modified Maxwell relaxation model with accounting of the yield strength Y like in [35,46]. In contrast to [35,46], both the yield strength Y and the relaxation time τ are treated as constants and directly optimized to reach the correspondence with the MD, as described in Section 2.3. This simplification can be eliminated in the future works, but here we try to use the simplest possible model of plasticity and to concentrate on the optimal parameter fitting.…”

Section: Fracture Modelmentioning

confidence: 99%

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Spall Fracture of Solid and Molten Copper: Molecular Dynamics, Mechanical Model and Strain Rate Dependence

Mayer

Pogorelko

Voronin

et al. 2022

Metals

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In this study, we formulate a mechanical model of spall fracture of copper, which describes both solid and molten states. The model is verified, and its parameters are found based on the data of molecular dynamics simulations of this process under ultrahigh strain rate of tension, leading to the formation of multiple pores within the considered volume element. A machine-learning-type Bayesian algorithm is used to identify the optimal parameters of the model. We also analyze the influence of the initial size distribution of pores or non-wettable inclusions in copper on the strain rate dependence of its spall strength and show that these initial heterogeneities explain the existing experimental data for moderate strain rates. This investigation promotes the development of atomistically-based machine learning approaches to description of the strength properties of metals and deepens the understanding of the spall fracture process.

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“…The introduction of dislocation immobilization kinetics [ 31 ] allows one to describe the gradual increase in yield strength behind the shock front, leading to a smooth structure of release waves following the shock wave [ 31 , 45 , 46 ]. A reduced version of this model was proposed in [ 47 ], where the Orowan equation for the plastic strain rate was replaced by a modified Maxwell relaxation model with the relaxation time dependent on the density of mobile dislocations [ 48 ]. The developed model was successfully applied for the simulation of classical Taylor tests in 2D [ 44 ] and 3D [ 23 ] cases, as well as for the investigation of instability in plastic flow as a mechanism of its localization [ 49 ].…”

Section: Introductionmentioning

confidence: 99%

Modified Taylor Impact Tests with Profiled Copper Cylinders: Experiment and Optimization of Dislocation Plasticity Model

et al. 2023

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Current progress in numerical simulations and machine learning allows one to apply complex loading conditions for the identification of parameters in plasticity models. This possibility expands the spectrum of examined deformed states and makes the identified model more consistent with engineering practice. A combined experimental-numerical approach to identify the model parameters and study the dynamic plasticity of metals is developed and applied to the case of cold-rolled OFHC copper. In the experimental part, profiled projectiles (reduced cylinders or cones in the head part) are proposed for the Taylor impact problem for the first time for material characterization. These projectiles allow us to reach large plastic deformations with true strains up to 1.3 at strain rates up to 105 s−1 at impact velocities below 130 m/s. The experimental results are used for the optimization of parameters of the dislocation plasticity model implemented in 3D with the numerical scheme of smoothed particle hydrodynamics (SPH). A Bayesian statistical method in combination with a trained artificial neural network as an SPH emulator is applied to optimize the parameters of the dislocation plasticity model. It is shown that classical Taylor cylinders are not enough for a univocal selection of the model parameters, while the profiled cylinders provide better optimization even if used separately. The combination of different shapes and an increase in the number of experiments increase the quality of optimization. The optimized numerical model is successfully validated by the experimental data about the shock wave profiles in flyer plate experiments from the literature. In total, a cheap, simple, but efficient route for optimizing a dynamic plasticity model is proposed. The dislocation plasticity model is extended to estimate grain refinement and volume fractions of weakened areas in comparison with experimental observations.

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Evolution of shock compression pulses in polymethylmethacrylate and aluminum

Cited by 31 publications

References 41 publications

Taylor Impact Tests with Copper Cylinders: Experiments, Microstructural Analysis and 3D SPH Modeling with Dislocation Plasticity and MD-Informed Artificial Neural Network as Equation of State

Taylor Impact Tests with Copper Cylinders: Experiments, Microstructural Analysis and 3D SPH Modeling with Dislocation Plasticity and MD-Informed Artificial Neural Network as Equation of State

Spall Fracture of Solid and Molten Copper: Molecular Dynamics, Mechanical Model and Strain Rate Dependence

Modified Taylor Impact Tests with Profiled Copper Cylinders: Experiment and Optimization of Dislocation Plasticity Model

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