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Role of Plasticity in Nitinol Fatigue
Shayanfard, Pejman ; Seiner,, Hanuš (referee) ; Dlouhý, Antonín (referee) ; Šandera, Pavel (advisor)
Disertace analyzuje vliv koncentrátorů napětí na průběh martensitické transformace, vznik plastické deformace a její vliv na přerozdělení napětí a vznik zbytkového pnutí a reziduálního martenzitu v okolí koncentrátorů v prvcích ze slitin s tvarovou pamětí NiTi. Vliv je analyzován v režimech superelastického isotermálního cyklování a aktuačního cyklování, t.j. teplotního cyklování pod vnějším napětím. Disertace využívá pro vyhodnocení vlivu experimentální přístup spolu s numerickými simulacemi metodou konečných prvků na modelových případech tenkých pásků ze slitin NiTi opatřených půlkruhovými vruby. V experimentální části je vyhodnocován vliv koncentrátorů pomocí termomechanických experimentů s využitím metod obrazové korelace a rentgenové mikrodifrakce pro lokální analýzu deformací a fázových objemových podílů v průběhu cyklování v okolí vrubů. Simulace metodou konečných prvků poskytují komplementární informace o průběhu napětí, deformací a martensitické transformaci, zejména o vývoji jednotlivých složek celkové deformace, tj. elastické a plastické, a vývoji zbytkového pnutí a s ním souvisejícím zbytkovým martensitem.Disertace je dále doplněna o numerickou analýzu vlivu konstrukce stentů na lokální cyklický průběh martensitické transformace a jeho vliv na únavové vlastnosti.
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Asphalt Layers using Fibreglass Composite Materials
Sadil, Dominik ; Hýzl, Petr (referee) ; Šperka, Pavel (advisor)
The diploma thesis deals with using of reinforcing composite materials in asphalt layers. These geosynthetic materials are in road construction used especially to reduce spreading cracks and extend the service life of the construction. As par of this work, test specimens of different types of asphalt layers were produced. These samples were subjected to laboratory testing, where the results of different reinforced asphalt slabs were compared. Within the diploma thesis primarily deals with the testing of the shear bond strength between asphalt layers in order to determine what are the other influencing factors of the test. Another part of the thesis is the 4-point bending test, during which a special technology in the form of a DIC camera was used to monitor the behavior of the asphalt layer over time.
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Use of the DIC method in solving basic problems of solid mechanics
Hrůza, Vlastimil ; Pokorný, Jan (referee) ; Ščerba, Bořek (advisor)
This bachelor’s theses deals with the solution of basic problems of solid mechanics using digital image correlation. The research part of the thesis presents some of the optical methods used for deformation measurement, digital image correlation in particular, whose history, principles, limitations and utilizations are described in detail. In the practical part of the theses, three experiments are carried out, which are then evaluated using digital image correlation and the results are compared with the created computational models. In the first experiment, strain on the tensile test specimens with notches is measured, the second experiment is focused on measuring strain when bending curved beams and in the final experiment, natural frequency of a fork produced by 3D printing is determined.
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Comparison of strains determined by finite element method and by optical measurement system
Zajíček, Vít ; Hlavoň, Pavel (referee) ; Vlk, Miloš (advisor)
This thesis focuses on the comparison of numerical simulation and optical measurement of deformation of the turbinehousing made by Honeywell company. The numerical calculation performed by finite element method to simulate transient thermal load on the measured entity. Numerical result of the strain state of the body caused by temperature gradients. To verify the simulation is used an experimental digital correlation method VIC-3D. The thesis also mentioned the theoretical foundations of digital correlation methods and thermal analysis.
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Computational analysis of a car axle arm opening
Procházka, Vojtěch ; Kubík, Petr (referee) ; Petruška, Jindřich (advisor)
This thesis is focused on behavior of control arm opening with bushing pressed in. The tested component is a part of control arm of a car. The parts were tested in tensile and compressive strength. Real experiments were measured by optical system Aramis during the testing to determine deformations of the part. These tests are also modeled by a finite element method using an Abaqus software. In GOM Correlate software is created full-field comparison of deformation results from Aramis and FEA. Based on this comparison computational model is calibrated. Sensitivity analysis is performed at the end of the thesis.
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Optical measurement of crack length utilizing the DIC method
Dziubek, Jan ; Halabuk, Dávid (referee) ; Ščerba, Bořek (advisor)
The thesis deals with the measurement of crack length using digital image correlation. The theoretical part of the thesis presents the method of digital image correlation, crack problems, and also introduces conventional methods for measuring crack length. There are currently no universal procedures in the field of crack length measurement using DIC. Different authors have only proposed different procedures to find the crack tip. Three different methods are used to determine the crack length using digital image correlation. Use of the edge detection method in the displacement field, the inflection point search method and the deformation threshold method. The aim of this work is to describe and compare these approaches.
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Application of DIC method in residual stress measurement using hole drilling method
Kováříková, Sabina ; Kubík, Petr (referee) ; Návrat, Tomáš (advisor)
This thesis deals with measurement of residual stress by hole drilling method. This method is based on drilling a hole and measurement of deformation in the area around this hole. Measured deformations are then converted to residual stresses by using calibration coefficients. The deformation around the drilled hole is measured by optical non contact method called digital image correlation (DIC). First part of the thesis is focused on current state of research. The thesis contains evaluation of residual stresses by using different methods and evaluation of used methods.
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Application of optical methods for determining the deformation of bodies
Kováříková, Sabina ; Šebek, František (referee) ; Návrat, Tomáš (advisor)
This Bachelor’s thesis is focused on application of digital image correlation method for determining the deformation of bodies. It contains theoretical knowledge about this method and realization of measurements on selected bodies. The aim of the thesis is to compare experimentally obtained results with the results, obtained in software Ansys Workbench. The Bachelor’s thesis also contains characteristics of other optical methods, used for determining the deformation of bodies and research of software, which can be used for data processing, based on DIC method.
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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.
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