Přijďte k nám ve dnech 12., 14. a 16. listopadu 2019, ať vidíte, na čem děláme! Více zde.
28 December 2016, 11:00 
Modelling of lotustype porous structures: bi and multi axial loading 
Assoc. prof. dr. Matjaž Šraml, University of Maribor, Slovenia 
Abstract: A computational modelling of the lowcycle fatigue behaviour of lotustype porous material subjected to multiaxial loading cycles is presented. The considered computational models have the same porosity but different pore topology patterns. Multiaxial loading conditions in the direction perpendicular to the longitudinal axis of pores are assumed to be proportional (inphase) and nonproportional (outofphase) loading paths in numerical simulation. The fatigue life analysis is performed using a damage initiation and evolution law, based on the inelastic strain energy approach. The computational results show that a different fatigue life is obtained in the models with the same porosity but with different pore topology at the same loading level. Furthermore, the results of computational simulations show a qualitative understanding of the loading path on lowcycle fatigue failures of lotustype porous material under multiaxial loading conditions.

7 December 2016, 10:00 
Iron. Static and "dynamic" phase diagrams and transformation kinetics. 
Prof. Eugene B. Zaretsky, Department of Mechanical Engineering, Ben Gurion University, Beer Sheva, Israel 
Abstract: Our civilization is closely acquainted with iron for some 4500 years, iron polymorphism is known for some 100 years, and it is some 50 years since the iron static phase (P,T) diagram has been established with reasonable accuracy. The talk describes some recent experimental results aimed to establishing the borders of existence of iron phases when the iron is compressed by shock. Such "dynamic" phase diagram is found to differ strongly from the static one, i.e. the shockgenerated metastable phase can subsist for a time longer than the experiment duration (microseconds) while the time required for the phase formation (transformation kinetics) is extremely short, few tens of nanoseconds.

9 November 2016, 10:00 
Regularized Models for Softening Materials 
Prof. Milan Jirásek, Czech Technical University in Prague, Faculty of Civil Engineering 
Abstract: For many materials, the deformation process at some stage leads to propagation and coalescence of existing defects and to initiation of new ones. If the defects grow sufficiently fast, the material can exhibit, on the macroscopic scale, a decrease of the averaged stress even at increasing strain. This phenomenon, referred to as softening, is one of the destabilizing factors that can, under certain conditions, lead to localization of inelastic deformation processes into narrow bands. An objective description of localized strain patterns in the framework of continuum mechanics requires special adjustments of material models, because for traditional models the width of the localized band can become arbitrarily small and, consequently, the numerical solution exhibits a pathological sensitivity to the discretization (e.g., to the size of finite elements). 
5 October 2016, 10:00 
Experimental study and simulation on localization of phase transformation in shape memory alloys 
Ing. Petr Sedlák, Ph.D., Institute of Thermomechanics of the CAS, v. v. i. 
Abstract: The remarkable properties of shape memory alloys (SMA) that are utilized in a number of useful applications are due to a phase transformation between austenite and martensite. In many situations, the transformation does not proceed homogenously, but in the form of macroscopic transformation bands, i.e. in a highly localized manner. Since these inhomogeneities influence the mechanical response and reduce the fatigue performance of SMA products, the roots and mechanisms of localization have been investigated by material scientists and engineers for many years. In a unique experiment utilizing the advanced technique of threedimensional Xray diffraction (3DXRD), complete strain and stress states of the polycrystalline grains close to the macroscopic transformation band front have been resolved on a grainbygrain basis for the first time. Results show substantial heterogeneity of stress between grains – implied by anisotropy of both elastic and transformation properties – and a striking redistribution of macroscopic (homogenized) stress near the interface. Analysis of the experimental data allowed the team to adapt an established constitutive model tailored for NiTi SMA so that nonlocal, gradient effects could be included. Consequent numerical simulation of the propagating transformation band demonstrated how the internal stress redistributes close to the phase interface within the wire causing the macroscopic localization to occur. 
15 September 2016, 10:00 
Effects of the nozzle exit boundary layer on hotjet mixing 
Ing. Jan Lepičovský, DrSc., Institute of Thermomechanics of the CAS, v. v. i. 
Abstract: The main motivation of the research effort reported here was passive protection of airplanes against an enemy’s heat seeking missiles. The stated goal was to reduce the temperature of a jet engine exit flow by means of the hotjet rapid mixing with the ambient air, and no penalty of the jet engine thrust was allowed. The focus of the first phase of this project was to explore the properties of highspeed free jets and demonstrate that it is possible to enhance jet flow mixing by flow excitation. Inconsistencies in hotjet responses to flow excitations were investigated in the second phase of this project. It was shown that the jet receptivity to flow excitation is strongly dependent on a character of the nozzle exit boundary layer. Finally, it was proven that the decisive factor controlling the jet receptivity is the velocity gradient across the exit boundary layer. There were also side byproducts of this research effort. First, it was an improvement in the highfrequency stroboscopic visualization of largescale turbulent structures in free jet flows. The second innovation was the development of a new methodology for conditional sampling of random laser velocimeter data. 
17 August 2016, 10:00 
Rotationfree parametrization and isogeometric analysis of shear deformable plates and shells 
Prof. Dr.Ing. habil. Manfred Bischoff, Institut für Baustatik und Baudynamik, Universität Stuttgart 
Abstract: Structural theories for static and dynamic analysis of shear deformable plates and shells (ReissnerMindlin type) usually employ independent degrees of freedom for displacements and rotations. It is shown how equivalent models can be developed based on displacement degrees of freedom only. In the context of finite element formulations this has the advantage that transverse shear locking can be intrinsically avoided within a standard displacementbased concept, regardless of the underlying function spaces used for discretization. As in this context higher continuity of the shape functions is required, a natural way is to incorporate such theories into the isogeometric concept, using NURBS (nonuniform rational Bsplines) as shape functions. Corresponding sheardeformable shell finite element formulations for geometrically linear and nonlinear applications are presented and their performance is demonstrated with the help of numerical examples. 
2 June 2016, 10:00 
Mathematics of fluids in motion 
Prof. Eduard Feireisl, Institute of Mathematics of the CAS, v. v. i. 
Abstract: We discuss the recent development of the mathematical theory of fluid dynamics, classical and new open problems and possibilities of their solution. Special attention is paid to the recent results on well and/or illposedness of problems describing inviscid fluids. In particular, several modern concepts of solutions are examined: Weak, very weak, measurevalued etc.

4 May 2016, 10:00 
Development of Human Artificial Vocal Folds 
Dr. Jaromír Horáček, Institute of Thermomechanics of the CAS, v. v. i. 
Abstract: Voice production is a complex physical process, which involves airflow coming from the lungs, selfoscillating vocal folds and acoustics of the resonance cavities of the human vocal tract. The vocal folds, excited by the airflow, generate a primary sound which propagates in the airways of the vocal tract modifying its spectrum and producing the final acoustic signal radiated from the mouth. Understanding basic principles of voice production is important for detection of laryngeal pathologies and treatment of laryngeal disorders. The physical models of voice production are important tools not only for experimental verification of computational 3D finite element models of phonation, but also for development of the vocal folds prosthesis. The study compares results of in vitro measurements of phonation characteristics performed on originally developed 1:1 scaled artificial models of human vocal folds. The measured aerodynamic, vibration and acoustic characteristics of the last models are comparable with the values found in humans..

6 April 2016, 10:00 
Stochastic SelfOrganization in Inner Structure of Vehicular Systems 
Prof. Milan Krbálek, Faculty of Nuclear Sciences and Physical Engineering, Department of Mathematics, Czech Technical University in Prague 
Abstract: History of traffic science is relatively short. Generally, it is meant that the first scientific article is the essay of Professor Bruce Greenshields dated to 1934. The factual beginning of systematic scientific discipline (called Transportation Science) is the year 1992, when the field accelerated by many famous publications. Nowadays Transportation Science is very well anchored in the portfolio of scientific disciplines (associated MIF is 1.377). For the purposes of this seminar talk we choose a theme of predictions for statistical properties of traffic flows and detection of surprising relations in traffic microstructure.

2 March 2016, 13:30 
Animal Flight 
Dr. Rudolf Dvořák, Institute of Thermomechanics of the CAS, v. v. i. 
Abstract: Unlike airplanes, animals must have either flapping wings (birds, bats) or oscillating wings (insects). Only such wings can produce both lift and thrust, provided the animal has sufficient muscle power.

3 February 2016, 10:00 
FLUIDIC OSCILLATORS FOR ALGAE CULTIVATION and their role in geopolitic stability 
Prof. Ing. Václav Tesař, CSc., Institute of Thermomechanics of the CAS, v. v. i. 
Abstract: 
6 January 2016, 10:00 
Discontinuous Galerkin method for the solution of elastodynamic, compressible flow and fluidstructure interaction problems 
Prof. Miloslav Feistauer, Department of Numerical Mathematics, Faculty of Mathematics and Physics, Charles University in Prague 
Abstract: 