Research group leader
- Basic mechanisms of creep, fatigue, brittle fracture and their combination in relation to microstructure of advanced metallic materials and composites.
- Theoretical studies of crack behaviour in metallic materials and composites and components.
- Multi-scale simulation of deformation and fracture processes, quantitative fractography and prediction of fatigue life under multiaxial loading.
- Solutions to problems related to fatigue, creep and brittle fracture of both currently applied and developed materials in industrial applications.
- Atomistic and multiscale studies of mechanical response of crystals, interfaces and thin surface layers to multiaxial loading, computational analysis of electronic structure and magnetism in solids.
Properties of engineering materials have to be continuously improved in order to achieve heightened performance, safety and reliability in engineering systems. The main objective of the research group’s activities is to study the relationship between material structures and material properties, mainly mechanical. The research is aimed at fatigue, creep, their interaction, and fracture properties of advanced materials and metal based composites used or currently being developed for application in energetics, transport and medicine. The expected results cover both the generation of material data necessary for safe and reliable application of engineering structures and components in service, and the extension of basic knowledge in material damage mechanisms.
Content of research
To achieve the objectives specified in the preceding section, extensive investigation of the properties (predominantly mechanical, electric and magnetic) of selected advanced materials in relation to their microstructure is carried out. Another line of research activity is the study of mechanisms in degradation processes in advanced metallic materials and composites under conditions simulating service loading.
Current specific research activities include:
Mechanical properties of advanced materials
The research currently focuses on basic mechanisms operating in materials during creep, fatigue and brittle fracture and on their relation to microstructures. Mechanical tests performed include creep testing, fatigue testing, tensile testing, fracture tests, as well as combined tests; e.g. combined creep/fatigue experiments. The research group is equipped with extensive set of testing facilities so that the tests can be performed in a broad range of temperatures, strain rates and other external parameters. The corresponding know-how is already available. An integral part of the group’s research activity is in theoretical studies of crack behaviour in homogeneous or composed materials and components. These studies are based on standard computational methods such as FEM.
Microstructure, diffusion and thermodynamics of advanced metallic materials
The group focuses on investigation of structures of materials in relation to their thermodynamic and diffusion properties. Structure is understood over a wide range of length scales starting with atomic bonds, through crystallographic lattice and its imperfections, to the size and morphology of crystallites (grains) in material. Within the framework of the Core facilities the research group has almost all the necessary equipment and the know-how for the investigation.
Multiaxial fatigue of advanced metallic materials
Research in this area primarily focuses on the elevated temperature behaviour of advanced metallic materials used in highly stressed components of turbines and combustion engines, with a special focus on aeronautics. Nickel based superalloys or lightweight TiAl intermetallic alloys are often subjected to complex loading conditions due to external load transfer, abrupt changes in geometry, temperature gradients, and material imperfections. The acquisition of a computer controlled multiaxial testing system facilitating high temperature cyclic multiaxial straining allows the study of damage mechanisms and provides information to obtain pertinent parameters characterizing the resistance of these advanced materials. Materials will be subjected to similar strain and stress histories to those they would encounter in critical locations of components and structures in the transport and energy production industries. The changes in the mechanical response are recorded and the modification of the internal structures and fatigue damage introduced by simulated complex loading situations are studied using transmission and scanning electron microscopy and atomic force microscopy in order to improve the resistance of new advanced materials and predict their fatigue life under the most severe external conditions.
Multiaxial fatigue of materials with protective surface layers
The mechanical damage of engineering materials and components is most frequently caused by multiaxial fatigue loading. Our current research is focused on the prediction of fatigue life of polycrystalline and surface hardened metallic samples subjected to this kind of loading. The investigation involves a development of multiaxial fatigue-life criteria, testing of samples under combined push-pull/torsion and bending/torsion cyclic loading and the application of 3D quantitative fractography.
Molecular dynamics and ab initio simulations of deformation and fracture at atomic level
Development of advanced materials, composites and various protective coatings often takes the advantage of computer aided materials design. Modern ab initio methods for electronic structure calculations represent a powerful tool for materials designers. Such methods can predict not only physical properties but also mechanical characteristics (such as elasticity and strength) of proposed materials without the need of synthesizing them which makes the design and development cheaper. Understanding the basic physical mechanisms of deformation and fracture is also facilitated by atomistic modelling.
Our group employs these approaches for studying structural transformations and deformation of single crystals, nanocomposites, thin films and shape-memory alloys. The atomistic methods are interconnected with sophisticated finite-element approaches in multi-scale models of fracture processes in nano, micro and macro sized samples made of these materials.