Computational materials science of cement-based materials

This paper describes recent research and theoretical results obtained for cement-based materials using computational materials science techniques. Computer-generated microstructure models are used to simulate the microstructure development during hydration, and exact algorithms are applied to these models to compute experimentally verifiable physical properties. Good agreement is found between experimental and simulation results.

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Resume Cet article décrit les résultats théoriques d'études récentes de matériaux à matrice de ciment au moyen des techniques de modélisation appliquées à la science des matériaux. On a utilisé des modèles de microstructure obtenus par ordinateur pour simuler le développement de la microstructure pendant l'hydratation, et on applique des algorithmes exacts à ces modèles afin de calculer les propriétés physiques vérifiables expérimentalement. On trouve une bonne concordance entre les résultats expérimentaux et ceux obtenus par simulation. Cet article est une adaptation de la conférence présentée à l'occasion de la remise de la Médaille Robert L'Hermite, lors de la 46ème Réunion du Conseil Général de la RILEM à Madrid, le 1 er octobre 1992.

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This paper is a non-verbatim written account of the 1992 Robert L'Hermite Medal lecture presented at the 46th General Council of RILEM, in Madrid, Spain, 1 October 1992.     

Computational materials science: The emergence of predictive capabilities of material behaviour

The availability of high performance computers and development of efficient algorithms has led to the emergence of computational materials science as the third branch of materials research complementing the traditional theoretical and experimental approaches. It has created new virtual realities in materials design that are either experimentally not realizable easily or are prohibitively expensive. The possibilities of doing calculations from first principles have led to predictive capabilities that open up new avenues of discovering novel materials with desired properties, understanding material behaviour on the nano- to the macroscopic scale and helping research in new frontiers that could interface between nano-materials and drug design, as well as in understanding biological systems. Here, we describe some significant recent developments related to alloy and steel design as well as the study of matter on the nano-scale — an area that has gained much prominence in current materials research.     

Computational materials: Multi-scale modeling and simulation of nanostructured materials

The paper provides details on the current approach to multi-scale modeling and simulation of advanced materials for structural applications. Examples are given that illustrate the suggested approaches to predicting the behavior and influencing the design of nanostructured materials such as high-performance polymers, composites, and nanotube-reinforced polymers. Primary simulation and measurement methods applicable to multi-scale modeling are outlined. Key challenges including verification and validation are highlighted and discussed.     

Nanoscale ion beam polishing of optical materials

A method of ion beam polishing is described, the special features of which consist in (i) preferential ion beam assisted deposition of a nanometer-thick layer into depressions of the initial relief by oxygen-ion sputtering of a target with a composition identical to that of the processed object; (ii) sputtering of the resulting surface structure by a normally incident low-energy oxygen ion beam to a depth reaching approximately two layers of the deposited material; and (iii) deposition-sputtering cycles repeated with gradually decreasing thickness of the deposited layer until the necessary final state of the surface is attained. Examples of the surface of quartz, sitall (glass ceramic), and BK-7 optical glass processed using the proposed ion beam polishing method show a more than twofold decrease in the height of the relief protrusions as compared to that on the initial surface. On the ion beam processed quartz surface areas with dimensions 2.5×2.5 μm, the maximum roughness height did not exceed 0.8 nm.     

Computational plasticity of mixed hardening pressure-dependency constitutive equations

In the present study, two semi-implicit schemes, based on the exponential maps method, are derived for integrating the pressure-sensitive constitutive equations. In spite of the fact that the consistent tangent operator is necessary to preserve the quadratic rate for the asymptotic convergence of the Newton-Raphson solution in the finite element analyses, there exists no derivation of this operator for the exponential-based integrations of the pressure-sensitive plasticity in the literature. To fulfill this need, the algorithmic tangent operators are extracted for the new semi-implicit as well as the former exponential-based integrations. Moreover, for the accurate integration presented by Rezaiee-Pajand et al. (Eur J Mech A Solids 30:345–361, 2011), the consistent tangent operator is obtained. Eventually, all the investigations are assessed by a broad range of numerical tests.     

Continuum Mechanics Approach and Computational Modelling of Submicrocrystalline and Nanoscale Materials

The material volumes containing internal submicrocrystalline and nano structures are investigated by numerical methods of continuum and quantum mechanics and some computational tools have been developed. Purpose of the research is numerical multiscale modeling and computer simulation of nanoparticle-reinforced materials and carbon-like nanostructures.     

Computational materials design: A perspective for atomistic approaches

Summary Present theoretical and computational approaches, combined with the impressive advances in computer hardware and software, open the possibility for materials design from first principles. This article presents a perspective on the relevant developments in computational chemistry, solid state physics and statistical mechanics and it assesses the merits and limitations of Hartree-Fock, density functional, semiempirical and force field approaches in terms of six criteria: capability, generality, accuracy, accessible system size, accessible time scales and computational efficiency. Functional materials for microelectronic, optical and magnetic applications currently present better opportunities for first-principles approaches than structural materials, where atomistic approaches, despite some encouraging results, are still far from capturing the full complexity of the dynamics involved in mechanical, thermal, diffusive and corrosive behavior.