Defence of dissertation in the field of civil engineering, Sergei Khakalo, M.Sc. (Tech.)
Modeling metamaterials and microarchitectured nano- and macro-structures by generalized continuum mechanics and isogeometric analysis.
The public examination of the doctoral dissertation of Sergei Khakalo, M.Sc. (Tech.), will be held on 8 December 2017 at 12.00 at the Aalto University School of Engineering. The title of the dissertation is Strain gradient continuum mechanics: simplified models, variational formulations and isogeometric analysis with applications. Field of the dissertation is civil engineering, computational structural engineering and mechanics.
The role of material modeling, in both scientific research and industrial R&D activities, is constantly increasing due to the achievements of multi-scale material sciences, computational sciences and advanced manufacturing technologies. The increasing complexity of materials, or structures with highly noticeable architectured microstructure, across the scales requires more advanced modeling techniques than provided by single-scale classical continuum mechanics laying a basis for today’s engineering design and analysis.
The dissertation focuses on a generalized continuum theory, namely strain gradient elasticity, considered as a remedy towards cost-efficient multi-scale modeling. Besides developing and analyzing theoretical models, the dissertation provides numerical methods for reliable computational engineering. Namely, for the “next-generation” continuum models involving high-order partial differential equations, classical methods such as the finite element method (FEM) must be replaced by non-standard numerical methods. The dissertation proposes isogeometric Galerkin methods as a general-purpose computational tool flexible enough for a wide range of applications and supporting interoperability within digital design, engineering and manufacturing chains. In the present work, isogeometric methods are implemented as user-subroutines into a commercial FEM-software (Abaqus).
Besides validation and verification problems, the dissertation provides some practical applications of both continuum models and numerical methods, and further demonstrations in the public defense. In particular, very strong size dependencies of 2D and 3D lattice structures with triangular and octet-truss microstructures are demonstrated: generalized continuum models elegantly capture the static and dynamic bending response of the lattice structures. The size dependency of lattice structures is utilized by designing a microarchitectured auxetic metamaterial which is 2.5 times stiffer and 25 % lighter than its conventional counterpart.
Opponent: Professor Francesco dell’Isola, Sapienza University of Rome, Department of Structural and Geotechnical Engineering, Rome, Italy
Supervisor: Assistant Professor Jarkko Niiranen, Aalto University School of Engineering, Department of Civil Engineering
Electronic dissertation: https://aaltodoc.aalto.fi/handle/123456789/49
Sergei Khakalo, email@example.com, tel +35850 434 4602