The thesis deals with the behaviour of a cracked rail wheel. The aim was to perform the strain analysis of intact wheel as well as the fracture analysis of the primary direct cracked wheel. Solution includes an analysis of operating conditions, assessment of the substantiality of articular components of load, stiffness of the wheel, a comprehensive analysis of fracture of the selected railway wheel profile and optimization of the wheel shape depending on the matching fracture properties.

Determination of mechanical properties of very thin films is rather difficult task as all of currently using testing techniques have some weakness. This master’s thesis deals with microcompressive test and bulge test. Finite element simulations of the two methods were carried out in order to better understanding of experimental record. Microcompression combines the sample preparation with the use of focused ion beam (FIB) with a compression test carried out using nanoindenter. Cylindrical specimens (pillars) were prepared from Al film deposited on Si substrate using FIB. Experimentally measured data on pillars needs correction to obtain undistorted material properties of Al thin film. A necessary correction using FE modeling is suggested in the thesis. Second part of the work is focused on modeling of bulge test. Pressure is applied on freestanding SiNx film while deflection of the film is measured. Stress state in the film is biaxial making determination of mechanical properties of the film more complicated. The goal is to present how to model the whole problem. In addition, preparation of the specimens was simulated to estimate residual stress in the film. The paper contributes to a better characterization of very thin surface layers and determination of their mechanical properties.

This master thesis deals with creation of computational model for stress - strain analysis of front car seat folding mechanism. The calculation has been done using FEM for static and dynamic load case. The results displayed the critical area of mechanism and determined the value of force when the safety of mechanism is not guaranteed and the force when the mechanism failure occurs. According to results from both load cases was made a statement that is necessary to model the dynamic load cases respecting the load time course.

This diploma thesis deals with creation of computational model of AZUB recumbent tricycle composite axle for stress strain analysis. The thesis consists of four main parts. The first part contains introduction to the offer of full suspended tricycles from the most known manufacturers. Furthermore it contains introduction to composite materials that makes the main element of AZUB´´s suspension, and the description of the AZUB´´s front axle. In the second part there is detailed compilation of computational model for purpose of stress strain analysis of three load states. The effect of specific material and geometry parameters on axle behavior is discussed with the aim of choosing the most appropriate variant. Third part deals with the manufacturing of the front axle prototype and with tests leading to input data for numerical model and verification of computational model. Modifications and changes that lead to manufacturing of the second prototype are content of the last part. Based on this experience some recommendations for future development of the numerical axle model and the front axle suspension itself are formulated.

This master thesis deals with creation computional model of specific door leaf which was researched and now is provided by company named IFE-CR, a.s. Finite element method analysis is performed within the standards for load conditions during the operation. Stress-strain response should be the main factor to comparing results with experiment on real door. Based on acquired knowledge from the original model we can evaluate credibility of mechanical behavior of newly designed model which has lower profil tapered from the original 42 mm to 25,4 mm. From the results of FEM analysis of the modified profile is evaluated applicability to the real operational state. At the end is quantified material and financial savings achieved by reducing the height of profile.

To, jak se bude implantát chovat v lebce, je velmi důležitým faktorem, který ovlivňuje jeho funkci. K ovlivnění dochází především vnějšími silami a nitrolebečním tlakem. Tato zatížení mohou způsobit pohyb implantátu a poškození živých tkání. Tato práce shrnuje poznatky a analýzy, týkající se rekonstrukce poranění lebky. Srovnání implantátů z různých materiálů a fixátorů je založené na napěťově-deformační analýze implantátu, zatíženého vnějšími silami a nitrolebečním tlakem.

No description available.

Hydrated cement paste (HCP), which is present in various cement-based materials, includes a number of constituents with distinct nano-structures. The elastic properties of the HCP crystals are calculated using molecular dynamics (MD) methods. The accuracy of estimated values is verified by comparing them with the results from experimental tests and other atomistic simulation methods. The outcome of MD simulations is then extended to predict the elastic properties of the C-S-H gel by rescaling the values calculated for the individual crystals. To take into account the contribution of porosity, a detailed microporomechanics study is conducted on low- and high-density types of C-S-H. The obtained results are verified by comparing the rescaled values with the predictions from nanoindentation tests. Moreover, the mechanical behavior of the HCP crystals is examined under uniaxial tensile strains. From the stress-strain curves obtained in the three orthogonal directions, elastic and plastic responses of the HCP crystals are investigated. A comprehensive chemical bond and structural damage analysis is also performed to characterize the failure mechanisms of the HCP crystals under high tensile strains. The outcome of this study provides detailed information about the nonlinear behavior, plastic deformation, and structural failure of the HCP phases and similar atomic structures.

Colonoscopy provides a minimally invasive tool for examining and treating the colon without surgery, but current endoscope designs still cause a degree of pain and injury to the colon wall. The most common colonoscopies are long tubes inserted through the rectum, with locomotion actuators, fiber optic lights, cameras, and biopsy tools on the distal end. The stiffness required to support these tools makes it difficult for the scopes to navigate the twisted path of the colon without damaging the inside wall of the colon or distorting its shape. In addition, little is known about how sharp and forceful endoscopes can be without accidentally cutting into tissue during navigation. In order to solve the requirements of stiffness (to support tools) and flexibility (to navigate turns), we expanded on a design by Zehel et al. [49], who proposed surrounding a flexible endoscope with an external exoskeleton structure, with controllable stiffness. The exoskeleton structure is comprised of rigid, articulating tubular units, which are stiffened or relaxed by four control cables. The stiffened or locked exoskeleton structure aids navigation and provides stability for the endoscope when it protrudes beyond the exoskeleton structure for examination and procedures. This research determined the design requirements of such an exoskeleton structure and simulated its behavior in a sigmoid colon model. To predict just how pointed an endoscope can be without damaging tissue under a given force, we extrapolated a strength model of the descending colon from published stress-strain curves of human colon tissue. Next we analyzed how friction, cable forces, and unit angles interact to hold the exoskeleton structure in a locked position. By creating two- and three-dimensional models of the exoskeleton structure, we optimized the dimensions of the units of an exoskeleton structure (diameter, thickness, and leg angle) and cable holders ( cable attachment location) to achieve the turns of the sigmoid colon, while still remaining lockable. Models also predicted the loss of force over the exoskeleton structure due to curving, further determining the required cable angles and friction between units. Finally we determined how the stiffness of the endoscope stem affected locking ability and wear inside the exoskeleton structure. / Ph. D.

No description available.