BUSCADOR RECOLECTA

An FFT-based algorithm is developed to simulate the propagation of elastic waves in heterogeneous
d-dimensional rectangular shape domains. The method allows one to prescribe the displacement as a function of time in a subregion of the domain, emulating the application of Dirichlet boundary conditions on an outer face. Time discretization is performed using an unconditionally stable beta-Newmark approach. The implicit problem for obtaining the displacement at each time step is solved by transforming the equilibrium equations into Fourier space and solving the corresponding linear system with a preconditioned Krylov solver. The resulting method is validated against analytical solutions and compared with implicit and explicit finite element simulations and with an explicit FFT approach. The accuracy of the method is similar to or better than that of finite elements, and the numerical performance is clearly superior, allowing the use of much larger models. To illustrate the capabilities of the method, some numerical examples are presented, including the propagation of planar, circular, and spherical waves and the simulation of the propagation of a pulse in a polycrystalline medium

The effect of dislocation pile-ups on the critical resolved shear stress necessary to overcome a regular distribution of circular precipitates has been analyzed by means of dislocation dynamics simulations. Both precipitates that can and cannot be sheared by dislocations have been considered. Hardening increases with the number of dislocations in the pile-up in the case of impenetrable precipitates due to the back-stress while shearable precipitates are eventually cut by dislocations if enough Orowan loops are piled-up against the precipitate. Analytical expressions for the critical resolved shear stress to overcome both impenetrable and shearable precipitates were developed based on the concept of an effective diameter as a function of the number of dislocations in the pile-up and of the friction stress to shear the precipitate. © 2023 The Author(s)

Object kinetic Monte Carlo (OkMC) is a fundamental tool for modeling defect evolution in volumes and times far beyond atomistic models. The elastic interaction between defects is classically considered using a dipolar approximation but this approach is limited to simple cases and can be inaccurate for large and close interacting defects. In this work a novel framework is proposed to include exact elastic interactions between defects in OkMC valid for any type of defect and anisotropic media. In this method, the elastic interaction energy of a defect is computed by volume integration of its elastic strain multiplied by the stress created by all the other defects, being both fields obtained numerically using a FFT solver. The resulting interaction energies reproduce analytical elastic solutions and show the limited accuracy of dipole approaches for close and large defects. The OkMC framework proposed is used to simulate the evolution in space and time of self-interstitial atoms and dislocation loops in iron. It is found that including the anisotropy has a quantitative effect in the evolution of all the type of defects studied. Regarding dislocation loops, it is observed that using the exact interaction energy results in higher interactions than using the dipole approximation for close loops.

This study introduces a microstructure -sensitive fatigue life prediction framework based on CP-FFT which includes the effect of surface roughness. The model is applied to flat Hastelloy-X specimens fabricated using Selective Laser Melting. The surface roughness measured is incorporated introducing a free surface with sinusoidal profile. The framework can accurately predict the fatigue life reduction of rough flat specimens using the fatigue parameters of polished bulk specimens and introducing the actual microstructure and roughness. A parametric study shows a monotonic reduction of life with the roughness amplitude but a minor effect of the surface waviness.

<p>Descripción del proyecto:</p>
<p> Investigación desarrollada dentro del proyecto ADSORBENT (Advanced Modeling Techniques for Hydrogen Embrittlement),</p>
<p> un estudio computacional multiescala de los mecanismos que participan en el fenómeno de fragilización por hidrógeno de aleaciones férreas.</p>
<p></p>
<p>Descripción del dataset: </p>
<p> Data generated by means of DFT calculations of hydrogen interstitial in the BCC lattice of iron. They include:</p>
<p> - Calculated energy landscape of Hydrogen as an interstitial in the absence of other defects or mechanical stress</p>
<p> - Calculations of the transition barriers between high-symmetry sites in the BCC-Fe lattice in stress-free configurations</p>
<p> - Calculations of the transition barriers between high-symmetry sites in the BCC-Fe lattice when subjected to hydrostatic, uniaxial and shear stress states.</p>
<p> - Calculations of the transition barriers between high-symmetry sites in the BCC-Fe lattice in the vicinity of a vacancy</p>
<p> - Calculations of the transition barriers between high-symmetry sites in the BCC-Fe lattice for two hydrogen interstitials.</p>
<p>