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Stanovení modulu pružnosti v tahu tenké vrstvy - numerická analýza zkoušky mikrokompresního vzorku a "bulge testu" / Determination of elastic modulus of thin layer - numerical study of microcompressive test and the bulge testPetráčková, Klára January 2013 (has links)
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.
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Deformačně-napěťová analýza sklápěcího mechanismu předního sedadla / Stress-strain analysis of front seat folding mechanismGergeľ, Erik January 2014 (has links)
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.
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Napjatostní, deformační a spolehlivostní analýza přední kompozitní nápravy lehokola / Stress, deformation and safety analysis of the recumbent bicycle frontal composite axleOndrejka, Jan January 2014 (has links)
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.
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Změna konstrukce profilu dveřního křídla pro kolejové vozidlo / Modifying profile design of the door leaf for rail vehicleLysák, Jan January 2015 (has links)
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.
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Deformační a napěťová analýza lebečního fixátoru / Stress and strain analysis of skull implantChamrad, Jakub January 2016 (has links)
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.
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MECHANICAL CHARACTERIZATION – MONOTONIC MICRO-TENSILE, STRESS RELAXATION, AND STRAIN-CONTROLLED CYCLIC STRESS-STRAIN RESPONSES OF SINGLE ELECTROSPUN PVDF NANOFIBERSFalola, Adekunle Samuel 29 August 2019 (has links)
No description available.
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Nano-Scale Investigation of Mechanical Characteristics of Main Phases of Hydrated Cement PasteHajilar, Shahin 18 March 2015 (has links)
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.
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Design and Development of a Minimally Invasive Endoscope: Highly Flexible Stem with Large Deflection and Stiffenable Exoskeleton StructureChoi, JungHun 27 February 2006 (has links)
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.
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Material characterization of viscoelastic polymeric molding compoundsJulian, Michael Robert January 1994 (has links)
No description available.
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Metodologická studie setření změn mechanických vlastností kolagenních tkání u pes equinovarus congenitus / Methodological study of changes in mechanical properties of collagen tissues from pes equinovarus congenitusČervený, Gustav January 2017 (has links)
The goal of this thesis was to invent and perform a testing protocol, witch can detect connective tissue mechanical and structural properties simultaneously in patients with clubfoot. Based on literature findings, it was presumed that connective tissue differ between medial and lateral side of foot. Because of low availability of specimen, it was important to draw and mention crucial alterations of testing protokol, for minimization of failed measurments. For reasons above, two specimens diveded into two samples was used for experiment. Described and discused methodics may enable of reader to insigt to drawbacks of this examination. For usability of this protocol, a setting and testing of few hypotheses was performed. One axis tensial testing with SHG microscopy examination was used in combination for experiment. One of the main result was finding, that structural differencies witch were expected, were not distinctive in samples in untensioned state. But, distingtive differencies may be drawed in tensioned samples. This differences for low number of specimen, cannot show any tendence. Results of tensial testing showed, that samples from medial side of foot can have higher toughness and higher fragility. For future acquisition of tendencies in specimen differencies, it is important to set particular...
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