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FEM simulation of the nanoindentation test with rigid non-rigid indenter
Kovář, J. ; Fuis, Vladimír
This paper focuses on the comparing of the results of the FEM simulations of fused silica nanoindentation tests. Fused silica is modelled like bilinear elasto-plastic material with the parameters estimated from the experiment. FEM simulations are made with the 2D axisymmetric conical indenter which is equivalent to the Berkovich indenter and the indentation curves are evaluated. The FEM simulations were made with the rigid and the non-rigid indenter and the difference between the indentation curves obtained with these models is assessed. The evaluated indentation curves are compared with the indentation curves obtained from the experiment.
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Anisotropy of Turbulent Flow around an Airfoil
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
The flow around an airfoil is analyzed from the point of view turbulence anisotropy assessment. The turbulent flow-field in the vicinity of an airfoil is populated by vortices, in some locations they tend to regularity in orientation, i.e. to anisotropy. However in the wake behind the plate as well as in the core of the boundary layer on the plate suction side the turbulence is close to isotropic state.
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Real-time diagnostics for ROS running systems based on probabilistic patterns identification
Věchet, Stanislav ; Krejsa, Jiří
Autonomous mobile robots consists of various software modules to achieve given goal, including solving complex navigation tasks as localization, mapping or path planning. These tasks are highly dependent on the quality of data measured and gathered from hardware subsystems. Using Robot Operating System (ROS) as integration basis reduces the development effort and time to market. While ROS framework itself is considered as reliable and stable to run even soft real-time tasks, in case of any internal failures on data misreadings can be problematic to debug or even identify the problem for common user. Due to this unpleasant situations we develop a virtual assistant, internally represented as diagnostic expert system, to help users to identify and possibly fix the problem.
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Utilization of Convolution Neural Network Based Road Detection in Mobile Robot Localization
Krejsa, Jiří ; Věchet, Stanislav
Mobile robot on-road navigation requires fusion of both global and local sensory information with an emphasis on the road detection processing. The paper deals with the road detection based on convolution neural networks (CNN) using commonly available tools such as TensorFlow and Keras. The road is defined by its linear boundaries. Network output is formed by the road definition together with classification parameters and serves as a local sensor in Kalman filter based localization. CNN based road detection is currently capable to successfully detect about 90% of images.
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Effect of pipe inclination on local concentration and flow behaviour of settling slurry
Vlasák, Pavel ; Chára, Zdeněk ; Matoušek, Václav ; Kesely, Mikoláš ; Konfršt, Jiří ; Mildner, Michael
Settling slurry, consisted from narrow-graded sand of mean particle diameter 0.87 mm and water, was investigated on an experimental pipe loop of inner diameter 100 mm. The investigation was focused on the effect of the pipe inclination, slurry concentration, and velocity on concentration distribution, and deposition limit. The settling slurries tend to stratify, a layered structure is typical for a settling slurry flow. Slurry stratification is sensitive to pipe inclination, and differs for the positive and negative pipe inclination. Deposition limit increases with pipe inclination up to about 25°, and then remain nearly constant.
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Engineering Mechanics 2019
Zolotarev, Igor ; Radolf, Vojtěch
The proceedings contains papers presented at the 25th International Conference on Engineering Mechanics, which has been held in Svratka resort in Czech Republic under auspices of the Czech Society of Mechanics and being a part of IFTOMM (The International Federation for the Promotion of Mechanism and Machine Science) activities. As it corresponds with character of the conference, this proceedings consists of several topic oriented parts: Biomechanics, Fluid mechanics, Dynamics, Fracture mechanics, Kinematics, Mechatronics, Reliability of structures, Mechanics of solids, Technological processes, Thermodynamics. The volume represents a well-balanced overview of theoretical, numerical and experimental work on fundamental and applied studies.
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Testing of HPD model of dissipated energy of hard rubbers at torsional finite Deformations and temperatures
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Šnábl, Pavel
This paper deals with the temperature dependence of hard rubber behavior on torsional harmonic loading. This behavior was described by dissipated and deformation energy of the rubber. This knowledge was used to test the validity of the hyperelastic proportional damping (HPD) in dependence on temperature and finite deformations. From the experiments, the dissipated energy was obtained from the hysteresis loop in one period of harmonic load, depending on the temperature for the given frequency. The deformation energy was determined from the shear stress analysis on the surface of the cylinder considering hyperelasticity. The constants of these models were obtained by optimizing the stress-strain curve from the shear analysis on the cylinder surface. With this optimization, the Yeoh hyperelastic model was chosen.
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Influence of tissue changes in superficial lamina propria on production of Czech vowels
Hájek, P. ; Švancara, P. ; Horáček, Jaromír ; Švec, J.
Superficial lamina propria (SLP) is a water-like vocal fold (VF) layer located directly under overlying epithelium. Its material properties affect VF motion and thus resulting spectrum of produced sound. Influence of stiffness and damping of the SLP on sound spectrum of Czech vowels is examined using a two-dimensional (2D) finite element (FE) model of a human phonation system. The model consists of the VF (structure model) connected with an idealized trachea and vocal tract (VT) (fluid models). Five VTs for all Czech vowels [a:], [e:], [i:], [o:] and [u:] were used and their geometry were based on MRI data. Fluid flow in the trachea and VT was modelled by unsteady viscous compressible Navier-Stokes equations. Such a formulation enabled numerical simulation of a fluid-structure-acoustic interaction (FSAI). Self-sustained oscillations of the VF were described by a momentum equation including large deformations and a homogeneous linear elastic model of material was used. Fluid and structure solvers exchange displacements and boundary forces in each iteration. During closed phase VFs are in contact and fluid flow is separated. We can observe that both the damping and the stiffness of the SLP substantially influence the amplitude and frequency of VFs vibration as well as the open time of the glottis.\n
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Experimental and computer modelling study of glottal closing velocity during phonation
Horáček, Jaromír ; Radolf, Vojtěch ; Bula, Vítězslav ; Šidlof, P. ; Geneid, A. ; Laukkanen, A. M.
This preliminary study shows that the impact stress between the colliding vocal folds during phonation should not be evaluated from the maximum velocity of the glottal closing because the velocity of the closing diminishes just before the glottal closure. This phenomenon, which can be caused by a pressure cushion effect in the fast narrowing glottal gap, is demonstrated with measurements from high speed camera images recorded from human and on a physical laboratory model for vowel [u:] phonation and on a three-mass computer model employing a Hertz model of impact force. For a more detailed future study of this phenomenon a faster camera has to be used. \n
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