National Repository of Grey Literature 42 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Analysis of composite sandwich panel under conditions simulating placement on a rocket carrier
Král, Martin ; Horníková, Jana (referee) ; Majer, Zdeněk (advisor)
This work deals with composite sandwich panels, which are currently used as supporting structures for satellites. This type of panel contains an aluminum honeycomb core and two thin laminate coatings, reinforced with carbon fibers. Laminate sandwich panel coatings offer an alternative to conventional aluminum coatings, which is advantageous mainly due to the reduction of weight and increase of the flexural stiffness of the panels. The work is a parametric study of mechanical properties for several variants of the coating of sandwich panels. These are laminate coatings, differing in the orientation of the fibers in the individual layers, as well as an aluminum alloy coating. The study is divided into two parts. The first part examines the deformation-stress response of a sandwich panel, which is simply supported at the edges and loaded with pressure. The response calculation is performed using FEM and verified by the method of sum of an infinite series. The second part investigates the deformation-stress response of the joint, (node) of two sandwich panels, which is loaded by random vibrations, aimed at simulating the mechanical environment of the rocket carrier during the takeoff of the launch vehicle. The response is calculated using FEM and verified by an experiment on a vibrating stool for a selected variant of the laminate coating of sandwich panels. The results of the work can be used for the design of baffle of the X-ray imaging device (SXI), which is part of the equipment of the space satellite of the SMILE project.
Proposal of topology of piezoceramic composite sensor
Dostal, Vojtěch ; Ševeček, Oldřich (referee) ; Majer, Zdeněk (advisor)
This master thesis deals with design and numerical modelling of piezoceramic sensor, which is placed on a rail, in order to generate electrical energy, which can be used for wireless monitoring of railway traffic and to monitor the condition of the railway. The thesis is divided into three parts. Theoretically background of piezoelectric energy harvesting is described in first part, where some previous application of piezoelectric generator in railway area are shown. In the second part, parametric analysis of numerical model is performed, which directly leads to finding best location on a rail, where piezoelectric generator should be placed. For this analysis the homogenized model of MFC sensor was used. Results of the numerical model were then compared with the results of the conducted experiment. The third part presented own design of piezoceramic sensor, which is placed onto most suitable location on a rail. Results from numerical analysis shown eligibility of using piezoceramic sensor to monitor the railway traffic.
Numerical modeling of failure of a particle composite with ceramic matrix
Kosorín, Michal ; Hrstka, Miroslav (referee) ; Majer, Zdeněk (advisor)
Subcritical crack growth in composite materials plays quite an important role in determination of the service life and leads to the defects growth below the fracture toughness. The thesis presents search of the several scientific works dealing with the determination of the crack growth direction in composite materials. The aim of this diploma thesis was to create 2D and 3D finite element models to analyse crack growth in Low Temperature Co-fired Ceramics (LTCC). These models were compared based on the time calculation of the crack propagation under the subcritical growth conditions.
Analysis of specific systems of bodies with neutral bonds
Grúz, Jan ; Hájek, Petr (referee) ; Majer, Zdeněk (advisor)
This thesis deals with analytical and graphical solution of three specific systems of bodies that are in static equilibrium. These systems of bodies contain neutral bonds. The opening part dedicates to theory and principles of solution of contact forces in bonds, which are further used for calculations and graphical solutions. The first system of bodies is a demonstrative tappet mechanism which was created for demonstration of some methods of graphical solution. The second system is inspired by lifting mechanisms in production lines. The aim is to find out the magnitude of contact forces for different positions of the lifted weight and a minimal torque of the propulsion. For solving the third system of bodies, principles of statics and hydrostatics are used. The aim is to find out the minimal magnitude of force for activating the mechanism. All systems of equations are solved in Matlab.
Computational tool for a stress-strain analysis of the mechanically loaded circular and annular plate
Dohnal, Jakub ; Majer, Zdeněk (referee) ; Ševeček, Oldřich (advisor)
The bachelor's thesis primarily deals with the creation of a computational tool for stress-strain analysis of rotationally symmetric circular and intercircular plates. The commercial software MATLAB and its component APP DESIGNER were used for this purpose. The program uses analytical relationships of general solid mechanics to solve differential equations for several types of plates and loads. Part of the bachelor thesis is also a parametric study comparing the outputs of analytical and numerical model based on the finite element method, aimed at identifying the practical application of the analytical solution and its accuracy for a particular case of the plate.
Stress-strain analysis of elastomer components of flexible coupling
Láštic, Daniel ; Majer, Zdeněk (referee) ; Burša, Jiří (advisor)
The diploma thesis deals with computational modelling of stress-strain states in elastomeric components of a flexible coupling. The first part of the thesis is dedicated to research about usage and designs of flexible coupling and about fatigue of elastomers. The second part of the thesis concerns creation of the computational model. The model of material is determined based on uniaxial tension test of a specimen produced from a real elastomer component. The results are presented in the form of comparison of two designs of elastomer component with respect to fatigue behaviour based on a maximum principal strain range. The results of computational modelling in the viewpoint of crack initiation site are in good agreement with the results from the component used in operation and dif-ferences between the two designs are negligible. The quantitative difference of the two designs is 15 %.
Integration of SMART Material within Mechanical Structure
Běhal, Josef ; Majer, Zdeněk (referee) ; Hadaš, Zdeněk (advisor)
This diploma thesis deals with the modelling of the piezoelectric composite material using the finite element method. The thesis is divided into three parts. Research study is done in the first part. It focuses on the possibility of use of the piezoelectric layers as sensors. The second part concerns the homogenization of MFC (macro fiber composite). Material and piezoelectric parameters are obtained by modelling elementary structural cell under different loading conditions. Determined characteristics are verified with experimental data. The third part proposes the design of the experimental device, which allows the simulation of the rotor excitation by rotating unbalance. Excitation responses of MFCs placed in specific locations are calculated using FEA model of the device. The conclusion includes the description of the suitability to vibration measurement on the device.
Computational analysis of the influence of initial defects on the ceramic foam failure upon mechanical loading
Papšík, Roman ; Majer, Zdeněk (referee) ; Ševeček, Oldřich (advisor)
The thesis deals with computational modelling of ceramic foams and analysis of influence of structural manufacturing defects (like broken struts, closed pores and material clumps) have on foam strength. Model of foam geometry was discretized using beam elements in order to decrease computational cost. In place where several struct join, rigid beam element was used so that the increased stiffness is better modelled. Closed walls of pores were modelled and discretised by shell elements. Influence of loading direction was analysed on foams containing no defects and then influence of amount of defects in foam on strength was further analysed. Highest strength show foams created by cells whose structs are oriented in direction of loading. These were losing strength most rapidly. Foam with structure of rhombic dodecahedral cell was least influenced by presence of closed pore defects but it also showed lowest strength even without defects. Cells with struts oriented in direction of loading experienced biggest drop in strength. Kelvin cell is a compromise. It was shown that difference in strength of strut with constant and varying cross-section is tenths of percent.
Assessment of impact of production inaccuracies on characteristic of a helical conus-shaped spring in compression
Sitte, David ; Majer, Zdeněk (referee) ; Burša, Jiří (advisor)
This bachelor thesis deals with the possible influence of production inaccuracies on the characteristics of the helical conus-shaped spring in compression. In the first part of the thesis there is a search for a given problem of the helical conus-shaped spring in compression calculation according to the algorithm created in the bachelor thesis „Určení charakteristiky kónické vinuté tlačné pružiny“ created by Libor Loveček. The remaining part of the thesis focuses on a concrete the helical conus-shaped spring in compression, namely on taking its variable pitch into consideration to achieve a better correspondence of the numerical model to the experimental characteristics.
A study of the stress distribution near the sharp notch tip
Svoboda, Petr ; Majer, Zdeněk (referee) ; Profant, Tomáš (advisor)
The presented diploma thesis deals with the problem of determining the stress singularity exponent of the V-notch. This task can be divided into two parts. The first deals with the theoretical background, that means the basic relations of mechanics and the basic concepts of fracture mechanics. The second part deals with the elaboration of the Williams method and the creation of a program for calculating the stress singularity exponent.

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