Journal of Multiscale Modelling

We setup a dislocation dynamics finite element framework by bridging a dislocation dynamics program and an open source finite element program. As part of initial verification, deformation of single crystal micro-pillar having single and double glide activation is demonstrated. A case study of a twin boundary is presented wherein the dislocation pile-up at the grain boundary and formation of a residual dislocation are shown. For studying the dislocation interactions with other grain boundaries, model grain boundaries are considered. We consider three synthetic grain boundaries namely transparent, semi-transparent, and impenetrable. The model’s transparent and semi-transparent grain boundaries contain no dislocations and very low density of dislocations in them, respectively, and thus low number of interactions with other dislocations. More junctions and cross-slip occurrences are recorded near the semi-transparent grain boundary. The most dislocation–dislocation interactions near grain boundaries result into glissile junctions. The current results are compared against literature data and it is observed that other than junction formation, cross-slip is very frequency observed near grain boundaries.

This study examines the heat transmission of magneto-hydrodynamic (MHD) hybrid nanofluid (Ag–${\mathrm{\text{Al}}}_2{\mathrm{\text{O}}}_3∕{\mathrm{\text{H}}}_2$O) flows between two stretchable or shrinkable walls. The nanoparticle volume fraction is considered an uncertain parameter and is represented using triangular and Gaussian fuzzy numbers. The governing radial momentum and energy equations are transformed into nonlinear ordinary differential equations using a similarity transformation and with the required boundary conditions. A generalized homotopy approach is used to analyze the impacts of embedding parameters, including the Reynolds number, stretching/shrinking parameter, opening angle, radiation parameter, Magnetic parameter, and solid volume fraction on velocity and thermal profiles in crisp and uncertain cases. The findings demonstrate that fluid velocity and temperature distribution increase as the stretching parameter increases. The correctness of the suggested technique is validated by comparing the results with the available numerical solution. It has been observed that there is a great agreement between the present results and the numerical ones.

In this paper, a multi-scale computational analysis is conducted based on representative volume element (RVE) modeling and molecular dynamics (MD) simulation of a carbon fiber-reinforced polymer composite micropillar. The fiber distribution in the micropillar was obtained from a specimen manufactured for real micropillar mechanical testing. Based on the failure modes directly observed from the micropillar testing, the RVE model aims to capture the major failure mechanism, which is the fiber/matrix interface failure of the composite. In the finite element model, the properties of each individual phase, namely, the fiber and the matrix are first identified. Then, cohesive elements are incorporated into the interphase region between the fiber and matrix to capture the interphase debonding. Finally, the global stress–strain relation of the composites is obtained and compared to experimental results. A good correlation was found. Due to convergence difficulties associated with stiffness degradation, the simulation was performed in the commercial software ABAQUS/Explicit. A Molecular dynamics simulation is performed to investigate the stress–strain relation and shear strength of carbon fiber-reinforced polymer composites at nanoscale. The compressive strength and stiffness obtained from MD simulation were lower than that observed from experiments. Interface debonding is a critical failure mode, of which the failure strength is determined from fiber pull-out simulation. The results can be used in RVE simulation to deduce the interphase properties. The modeling method allows the detailed failure mechanisms of the composite microstructure to be captured and a correlation between the micro-properties and macro-properties of the material to be established.