Research area and topicality of the work. Mechanical properties and their evolution under loading are the most significant factors for the development of various mechanical structures, technologies and equipment. It seems to be natu-ral that deeper understanding of the behaviour of existing and design of new materials presents a challenge in different research areas.

It should be noted, that all the materials are heterogeneous in meso- and

micro- scales. They exhibit essential differences, compared to the macroscopic continuum behaviour. Basically, both experimental and numerical simulation methods are extensively applied for investigation purposes.

Experimental techniques, capable of giving a realistic view of the inside of the material and extracting the real data, are very expensive. Therefore, the nu-merical simulation tools are extensively used as an alternative for investigation purposes. They have considerable advantages allowing the reproduction of multiple experiments and providing comprehensive data about ongoing phe-nomena.

Recently, numerical technologies have become highly multidisciplinary subjects. They comprise phenomenological and statistical ideas, while mathe-matical models employ the relations of continuum mechanics, classical discre-tization methods and molecular dynamics. The Discrete Element Method (DEM) is one of new methods. It is aimed at simulating the dynamic behaviour of the contacting particles. Variable topology of the system of particles is an essential attribute of DEM. However, DEM is in the state of development, and many issues have still to be solved in the nearest future a particular focus is placed on the development of continuum consistent DEM models for elastic solids and investigation of brittle fracture. On the other hand, computer imple-mentation requires the development of new computational tools.

Therefore, the investigation of dynamic the behaviour and fracture of elastic and solid structures by the Discrete Element Method is a relevant problem which has to be solved in the nearest future.

The main objectives and tasks. The main objective of the present work is to enhance the existing and to develop classical continuum consistent DEM models for discretisation of elastic continuum and to apply them to the simula-tion of the dynamic deformation behaviour and fracture problems.

The following tasks have to be performed:

1. Development of the lattice type DEM models for discretisation of the elastic continuum.

2. Evaluation of the discrete elasticity parameters.

3. Development of a computational DEM algorithm and software code.

4. Investigation and their evaluation of the developed models and applica-tion to investigation of the dynamic deformation behaviour and fracture.

Novelty of the research. The present work addresses a relatively new simulation tool, the Discrete Element Method (DEM) and its application to the solution of continuum problems. Original contribution of the work is the devel-opment of classical continuum consistent lattice type DEM models. The appli-cation of the natural finite elements to evaluating discrete elasticity constants presents the main novelty. Compared to earlier approaches, the developed models exhibit diversity of lattice geometry and cover a full range of Poisson’s ratio values.

The particular contribution concerns the development of the original DEM software code DEMMAT-C. The results provided new knowledge on DEM ap-plication to elastic dynamics, brittle fracture and post-fracture behaviour.

Research object and methods. Dynamic deformation behaviour and brittle fracture of the heterogeneous solids are considered, while the research is focus-sed on the development and implementation of the classical continuum consis-tent DEM models. Computational DEM methodology and the original code DEMMAT were used. Standard BEM and ANSYS code was applied for valida-tion purposes.

Practical value. The developed DEM models and software code demon-strated good performance and competitive ability compared to standard BEM technologies in capturing dynamic behaviour and exhibited clear advantages in simulation of brittle fracture and multi-cracking phenomenon, in particular.

The presented DEM development serves as a basis for enhanced elasticity models, including anisotropy, irregular lattice grid and 3D problems and for various fracture models.

The developed methodology may be applied in smaller scales, including atomistic structures.

Raktažodžiai: Discrete element method, heterogeneous structure, elastic dynamic deformation, brittle fracture