Mechanical Behavior of Polycrystalline Non-metallics at Elevated Temperature Progress Report, Apr. 1 - Sep. 30, 1966
Mechanical behavior of polycrystalline nonmetallics at elevated temperature
POLYCRYSTAL↗
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Characterization of ceramic materials for microelectronic applications Summary report no. 1, 23 Nov. 1965 - 23 Nov. 1966
Dielectric properties of polycrystalline barium titanate ceramic materials for microelectronic applications
CERAMICS↗
The effect of temperature and photon radiation on the electrical breakdown of ceramic insulations
Temperature and gamma radiation effects on electric breakdown of polycrystalline alpha phase aluminum oxide ceramic insulators used in nuclear thermionic reactors
POLYCRYSTAL↗
Effect of recrystallization on friction properties of some metals in single-crystal and polycrystalline form
Recrystallization effect on sliding friction of metals in single-crystal polycrystalline form
POLYCRYSTAL↗
Impurity distribution in MgO.
Microprobe study of impurities in hot-pressed polycrystalline MgO compact and existence of significant grain boundary volume
IMPURITY↗
Magnetostriction of Single Crystal and Polycrystalline Tb 0.60 Dy 0.40 at Cryogenic Temperatures
At cryogenic temperatures, TbDy alloys exhibit giant magnetostriction, which makes these materials interesting for engineering service in cryogenics actuators, valves, and positioners.
polycrystal cryogenic TbDy magnetostriction↗
Heat Switches for Cryogenic Application with Polycrystalline Magnetostrictive and Superconducting Flux Tube Actuation
These heat switches are designed to replace slower gas-gap switches in many applications. Applications include isolating calorimeters, and the thermal shorting of heat shields to shorten cool down times on cryogenic apparatus.
High Temperature Superconductor↗
Geometric Requirements for Modeling Polycrystalline Representative Volume Elements Using the Generalized Method of Cells
To accurately predict the mechanical response of advanced metallic parts, the grain structure of the metal must be considered and coupled to the macroscale in a multiscale model. The size of the microscale representative volume element must be sufficiently large, and the grid used to discretize the microscale must be adequately refined, in order to ensure an accurate and converged solution. The generalized method of cells is used to predict the mechanical properties of polycrystalline representative volume elements of copper containing randomly oriented grains with the properties of a single face-centered-cubic crystal. Moreover, the results of a parametric study are used to conclude the geometric requirements for an objective microscale model, with respect to the elastic stiffness.
Multiscale Modeling↗
A Convolutional Neural Network for Enhancement of Multi-Scale Localization in Granular Metallic Representative Unit Cells
A convolutional neural network was used to enhance the localization of strain and stress for a generalized method of cells model of a metallic microstructure. Enhanced shear strains, measured in terms of the linear regression coefficients as a function of ground truth strains, were improved from inaccurate and uncorrelated (slope=0.003, Rsq=0.000) to accurate and well correlated (slope=0.890, Rsq=0.882) relative to ground truth (slope=1.0, Rsq=1.0). In applying the convolutional neural network, a convolutional stride of 1.0 (padding=’same’) was only modestly effective while strides of 2 or 3 were more effective yet at higher cost. Additional convolutional layers were generally more expensive than additional dense layers, often with limited benefit. The accuracy of enhanced localized shear strains and stress is expected to yield benefits for damage progression models, especially in the context of hierarchical multi-scale methods where the generalized method of cells is applied at the intermediate scale.
Machine Learning↗
Molecular Dynamics Study of Creep Deformation in Nickel-based Superalloy
The present study employs molecular dynamics simulations of Ni-based superalloy to investigate the creep behavior under uniaxial compression test. Dislocation dynamics is analyzed for the nickel-based single crystal superalloy with the presence of void and with varying the distribution of gamma-prime phase The results show that multiple-void systems are more prone to yield than single-void systems and single-void systems are more prone to yield than the system withoutvoid. From the simulations, it has been determined that the creep mechanism in Ni/Ni3Al is subject to change on the applied stress depending on the distribution of gamma-prime phases change. Dislocation behavior is also observed in addition to the time evolution of dislocation nucleation and growth to quantify the propensity and mechanism of creep in nickel-based single crystal superalloy. The studies confirmed that dislocation length prior to plastic deformation decreased as the number of voids increased. In addition, the deformation behavior for finegrained nickel-based polycrystalline superalloy upon grain size variation is also investigated. Our findings show that both the movement mechanisms of the grains and grain boundaries and the relationship between grain size and yield strength are highly affected by the grain size of the materials. All the databases have then been classified to accurately predict the target class vi machine learning using the data mining tool WEKA.
creep, nickel-based superalloy, molecular dynamics↗