Projects / Programmes
Numerical and Experimental Analysis of Nonlinear Mechanical Systems
January 1, 2004
- December 31, 2008
| Code |
Science |
Field |
Subfield |
| 2.05.00 |
Engineering sciences and technologies |
Mechanics |
|
| Code |
Science |
Field |
| T210 |
Technological sciences |
Mechanical engineering, hydraulics, vacuum technology, vibration and acoustic engineering |
Fracture mechanics, structure integrity, fatigue crack growth rate, optimal design, nonlinear periodic and aperiodic oscillations, stability of mechanical systems, bifurcations, parametric identification of vibration systems, statistical mechanics, nonequilibrium mechanics
Researchers (13)
Organisations (1)
Abstract
Applicability of fracture mechanics parameters cover transferability between experimentally determined fracture behaviour of specimens and structures. This should take in account interaction of hetrogeneous mechanical properties and effect of different loading modes to structure's loading. Main research based on numerical modelling and experimental verification of global fracture behaviour of structure. In this research the new technique for mechanical properties and fracture properties will be developed by observing deformable behvaiour of surface of materials-similar as hardness indentation testing.
Into the field of shape optimization there are two dominant in-roads. The first one is of a parametrization type and the second of an evolutionary type. In the research group we will address the development of parametrization based approach. The possibility of shape parametrization of structures by employing standard finite element meshes will remove the largest drawback of parametrization based approaches and thus enhance their usability. This will be achieved by introducing design-element-independent control points which will be related to the structural shape in a much looser manner. This research will be accompanied by the development of our own gradient-based optimization method adapted to the considered optimization problems. Among the objectives the highest priority is set to the enhanced approach to shape optimization which will be usable in practice.
In the past, the research group concentrate attention on the investigation of periodic and aperiodic oscillations of nonlinear dynamical systems by using incremental harmonic balance method with multiple time scales. As independent result of this effort, an general algorithm for parametric studies of periodic and aperiodic oscillations is working out. The incremental harmonic balance method with multiple time scales will be further developed for an automated construction of frequency spectrum of some kind of nonautonomous systems exhibiting the phenomenon of internal resonance. Also, bifurcations of nonlinear oscillations will be explored by using branch tracing. The arc length method, algorithms for solving various singular points and stability analysis will be involved in the method. Beside systems with cubic nonlinearities explored in the past, the parametrically excited systems and nonlinear systems with discontinuous characteristics will be investigated, too. Stability regions of parametrically systems will be determined by using multiple time scales concept for the problem of combination frequencies. Galerkin procedure, which is a part of the method, wiil be used for parametric identification of nonlinear periodically excited systems and autonomous relaxation systems.
By using theory of nonequilibrium processes the solid state and fluid models for computation of equlibrium as well as nonequilibrium mechanical properties will be worked out in the field of statistical mechanic. The one's own models will be expanded also on the range of polymers and ion fluids. By using the developed models, elastic and shear modules, compressibility, viscosity, etc. of arbitrary materials will be computed and mechanical properties of new materials will be predicted. The influence of translation, rotation and vibration of molecules will be considered. Special attention will be paid to intermolecular potentials. The nonequlibrium mechanics study of molecules, composed from many atoms will be studied in details. The mixtures in solids and fluids will be investigated, where mixing rules will be determined on the basys of the comparison with experimental results.
Significance for science
Development of the IHB and EL-P methods, respectively is based on the application of multiple time scales, wich enable to treat problems of periodic as well as aperiodic nature. The introduction of an additional, slow time scale into EL-P method enables the treatment of stationary and nonstationary aperiodic phenomena, which is the newest approach in solving problems of this type. In the analysis, nonlinear frequencies of oscillating systems are considered, which can be noncommensurate in general and influenced by internal resonances. In the fracture mechanics the model is developed, which can explain the variation of the fatigue crack growth rate during the fatigue crack propagation in inhomogeneous specimens including residual stresses. The introduction of multiple scales into numerical analysis enables the correct modelling of the crack initiation and local crack growth in specimens. On the field of optimization we contributed to the development new optimization procedures. The most important gain is an effective shape parametrization of structures and the consideration of their stability during the optimization process. Research in the field of statistical mechanics and development of the theoretical models has a greath meaning for the computation of equilibrium and nonequilibrium mechanical properties of solids and fluids.
Significance for the country
Researches, which are recently performed, have a greath meaning for quality assurance of structures and nonlinear mechanical systems during the changeable operation conditions. Researches have a greath applicative meaning in the area of structural elements such as beams, plates, shells as well as in the rotordynamics and mechanical systems with flexibile structures. In frame of performed research, it was performed stress-strain analysis of fracture behaviour of inhomgeneous advanced materials. Results show development of new inhomogeneous materials for components in order to gain certain mechanical and functional properties. An inhomogeneity of materials usually exhibit unstable fracture behaviour, but it is possibe to improve higher loading capacity and higer crack initiaiton and crack growth resistance by appropriate design of inhomogenous structures. Application of research results contribute to development of national significat products such structure's components with advanced performance with high level of quality. The newly developed optimization procedures enable efficient shape design of structures. This new knowledge will incrase the competitiveness of the enterprises, dealing with structural design. Knowledge in the area of the statistical mechanics and influence of the temperature in thermomechanical models will be useful in conquering of nanotechnologies and MEMS.
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