|
|
Small strain stiffness of soils and methods of its measurement
Havlíček, Jaroslav ; Miča, Lumír (referee) ; Chalmovský, Juraj (advisor)
This thesis consists of theoretical and practical part. Firstly, the soil behaviour at small-strain range and its physical nature are described. Subsequently, the individual soil parameters affecting the value of small-strain shear modulus and the shape of the stiffness reduction curve with increasing shear strain are described. The individual methods of measuring the small-strain stiffness in the laboratory and in-situ with a more detailed explanation of the evaluation of measurements using bender elements are given in the last chapter of the theoretical part. In the practical part, a device for measuring small-strain stiffness using bender elements was put into operation. The used laboratory equipment is described first and then the parameters of tested soil are given. The main chapter is measurement and evaluation of the impact of software and hardware settings and the influence of effective stress of soil on the small-strain shear modulus that is compared with predictions of empirical expressions from the literature.
|
|
|
Rheological properties of binders
Hotař, Petr ; Fišer,, Jiří (referee) ; Kudrna, Jan (advisor)
The comparison of rheological properties (complex shear modulus and phase angle and dynamic viscosity) of four paving bitumens and two polymer modified bitumens is performed in this diploma thesis. Furthermore, the empirical tests (needle penetration and softening point) were determined on these binders. Effect of asphalt binders aging was modeled using RTFOT test and modified RTFOT test (3 x RTFOT).
|
|
|
Experimental comparison of shear properties of FRP measured by ASTM methods
Ponížil, Tomáš ; Mališ, Michal (referee) ; Urík, Tomáš (advisor)
Přesné určení konstitutivních smykových závislostí napětí na deformacích je základem pro pochopení chování anizotropního kompozitního materiálu. Bylo vyvinuto mnoho zkoušek smykových vlastností kompozitních materiálu. Jelikož vyvolání čisté smykové napjatosti je složité, tento stav je vyvolán pouze některými z nich. V této práci je ověřeno použití systému Aramis k vyhodnocení průběhu smykového přetvoření a následnému výpočtu konstitutivních smykových vlastností při provedení jednoduché zkoušky ohybem krátkého nosníku. Tyto výsledky jsou dále porovnány se zkouškou podle Nicolae Iosipesca.
|
|
|
Properties and behavior of magnetorheological elastomers and foams
Zedník, Roman ; Macháček, Ondřej (referee) ; Roupec, Jakub (advisor)
This bachelor thesis provides a current overview of magnetorheological foams and elastomers. The structure of individual types of foams and elastomers was discussed here. Various operation modes which are essential for constructing of devices with these materials were explained. Further regulation options and ways of magnetic induction conduction were discussed. And most important microscopic and macroscopic properties were highlighted. Latest ways of production of these materials are mentioned here. Lastly methods of use of MR foams and elastomers were proposed and above that which of the materials is most appropriate for certain application was said.
|
|
|
Laboratory research on stiffness of unsaturated soil in very small and small strain region
Mohyla, Tomáš ; Boháč, Jan (advisor) ; Herle, Ivo (referee) ; Panuška, Jakub (referee)
Unsaturated soils have come into focus of the geotechnical community in recent decades. They are commonly found in the interaction of structures with the geological environment. Laboratory tests are important to provide information on the behaviour of unsaturated soils and as a fundamental input for the design of engineering structures. Laboratory tests can also be used to design and calibrate numerical models describing the behaviour of unsaturated soils. One of the important input parameters of such models is the initial stiffness of the soil and its decrease with increasing strain. This thesis deals with a laboratory investigation of the stiffness of unsaturated soil in the regions of very small and small strains. The tested soil was a loess from the quarry near the village of Horky nad Jizerou, Central Bohemia, which represents a typical soil found in engineering practice. The soil was reconstituted for the purpose of laboratory tests. The maximum (initial) stiffness of the soil was determined from measurements using piezoelectric bender elements and the stiffness decay curves were measured using local strain transducers (LVDTs). The laboratory tests were carried out in a double-walled triaxial cell for unsaturated soils, mounted with a high air-entry value ceramic disc (HAEV). The triaxial...
|
|
|
: Viscoelasticity of bones - the methodology of measurement
Cihlář, Zdeněk ; Ďoubal, Stanislav (advisor) ; Kuchařová, Monika (referee)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of biophysics and physical chemistry Candidate: Mgr. Zdeněk Cihlář Supervisor: Prof. RNDr. Ing. Stanislav Ďoubal, CSc. Title of Thesis: Viscoelasticity of bones - the methodology of measurement The aim of the thesis was to verify the methodology of measuring the viscoelastic parameters of human bones using an apparatus enabling the measurement of dynamic characteristics. The method is based on measurement of deformation response of samples to short or rectangular impulse of force. The samples were obtained from femoral head. The methodology is therefore based on measuring of creep curves and impulse characteristics. Resulting damped oscillations were analysed. The transient and impulse characteristics in bending stress and twisting stress were obtained. Based on these characteristics, viscoelastic parameters of samples were determined (Young modulus, shear modulus and viscosity). The Poisson's number, indicating the ratio of transverse contraction to longitudinal extension of the material during deformation, was calculated using the values of Young's modulus and shear modulus. The measured values of the Young's modulus in bending stress vary in the range from 62MPa to 670MPa. The values of the shear stress modulus range...
|
|
|
Stiffness anisotropy of Brno Tegel determined by bender elements
Krupička, Martin ; Najser, Jan (advisor) ; Malát, Richard (referee)
This Thesis deals with the determination of shear moduli of Brno Neogene clay ("tegel") in various directions and the determination of its stiffness anisotropy. The basic measure of stiffness anisotropy in this thesis is considered to be the degree of anisotropy αG given by the ratio of shear moduli in the horizontal (Ghh) and vertical direction (Gvh). Measurements of shear wave velocity were performed on undisturbed vertically and horizontally oriented samples of the Brno tegel in triaxial cell using piezoceramic sensors, so-called bender elements. As an advanced method for determining the degree of anisotropy of the material, another pair of bender elements was used in the measurements, mounted horizontally on the side walls of the sample in the triaxial cell. Based on these measurements, the values of shear moduli Ghh and Gvh for different stress levels were determined. The ratio of shear moduli then determined the degree of anisotropy αG ≈ 1,43 for the given stresses, as the most reliable value based on performed experiments. Literature review part of the thesis briefly summarizes the existing findings from research of physical and mechanical properties of the Brno tegel.
|
|
|
Small strain stiffness of soils and methods of its measurement
Havlíček, Jaroslav ; Miča, Lumír (referee) ; Chalmovský, Juraj (advisor)
This thesis consists of theoretical and practical part. Firstly, the soil behaviour at small-strain range and its physical nature are described. Subsequently, the individual soil parameters affecting the value of small-strain shear modulus and the shape of the stiffness reduction curve with increasing shear strain are described. The individual methods of measuring the small-strain stiffness in the laboratory and in-situ with a more detailed explanation of the evaluation of measurements using bender elements are given in the last chapter of the theoretical part. In the practical part, a device for measuring small-strain stiffness using bender elements was put into operation. The used laboratory equipment is described first and then the parameters of tested soil are given. The main chapter is measurement and evaluation of the impact of software and hardware settings and the influence of effective stress of soil on the small-strain shear modulus that is compared with predictions of empirical expressions from the literature.
|
|
|
: Viscoelasticity of bones - the methodology of measurement
Cihlář, Zdeněk ; Ďoubal, Stanislav (advisor) ; Kuchařová, Monika (referee)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of biophysics and physical chemistry Candidate: Mgr. Zdeněk Cihlář Supervisor: Prof. RNDr. Ing. Stanislav Ďoubal, CSc. Title of Thesis: Viscoelasticity of bones - the methodology of measurement The aim of the thesis was to verify the methodology of measuring the viscoelastic parameters of human bones using an apparatus enabling the measurement of dynamic characteristics. The method is based on measurement of deformation response of samples to short or rectangular impulse of force. The samples were obtained from femoral head. The methodology is therefore based on measuring of creep curves and impulse characteristics. Resulting damped oscillations were analysed. The transient and impulse characteristics in bending stress and twisting stress were obtained. Based on these characteristics, viscoelastic parameters of samples were determined (Young modulus, shear modulus and viscosity). The Poisson's number, indicating the ratio of transverse contraction to longitudinal extension of the material during deformation, was calculated using the values of Young's modulus and shear modulus. The measured values of the Young's modulus in bending stress vary in the range from 62MPa to 670MPa. The values of the shear stress modulus range...
|
|
|
Properties and behavior of magnetorheological elastomers and foams
Zedník, Roman ; Macháček, Ondřej (referee) ; Roupec, Jakub (advisor)
This bachelor thesis provides a current overview of magnetorheological foams and elastomers. The structure of individual types of foams and elastomers was discussed here. Various operation modes which are essential for constructing of devices with these materials were explained. Further regulation options and ways of magnetic induction conduction were discussed. And most important microscopic and macroscopic properties were highlighted. Latest ways of production of these materials are mentioned here. Lastly methods of use of MR foams and elastomers were proposed and above that which of the materials is most appropriate for certain application was said.
|
guest ::
