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Determination of residual stresses from strain field around drilled hole
Horák, Richard ; Návrat, Tomáš (referee) ; Halabuk, Dávid (advisor)
The master’s thesis focuses on determining homogeneous residual stresses using the hole-drilling method. The optical method of digital image correlation (DIC) is used for measuring released strains. In order to evaluate residual stresses using the entire strain field, it is necessary to know the functional dependencies of calibration constants on this field. Therefore, a significant part of the master’s thesis includes finding these dependencies in relation to the dimensions of the drilled hole and coordinates of the measured points. Another part of the thesis deals with the evaluation of homogeneous residual stresses based on provided experimental data obtained from the measurement of uniaxially loaded steel flat bar with a through-hole. At the end of the thesis, a sensitivity analysis is performed, which examines the influence of input variables in the calculation algorithm in relation to computed residual stresses.
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Comparison of crack length measurement methods utilizing digital image correlation
Dziubek, Jan ; Houfek, Lubomír (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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Detection of infill defects in 3D printed structures using the DIC method
Doležal, Tomáš ; Halabuk, Dávid (referee) ; Ščerba, Bořek (advisor)
Additive manufacturing offers wide range of advantages. However various internal defects are likely to be formed during the manufacturing process which negatively affect mechanical properties. Detection of those defects is critical to ensure that the manufactured component stays reliable and maintains its dependability throughout its whole life. The potential of the digital image correlation (DIC) method for detect detection in components manufactured using additive technologies has not yet been investigated in the literature. In this master thesis a novel non-destructive defectoscopic method for the internal defect detection in 3D printed structures is presented, based on the evaluation of the strain field obtained by the DIC method. The method was experimentally evaluated on samples with artificial internal defects fabricated by FDM technology. The samples containing defects were successfully visually detected. A convolutional neural network was then used for the defect detection and achieved a classification accuracy of 94,5 %. This methodology has a potential to provide cheap and fast detection of internal defects formed in additive manufactured components in the future although future research is still required.
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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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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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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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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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Deformační analýza kmene při kácení
Veselý, Jiří
This work deals with strain analysis of tree during felling. The main goal is to describe the origin of the deformation field. Another aim is to explain the effect of individual cuts on the size of deformation forces. Two relatively new methods in the field of wood are used to investigate the experimentally, namely digital image correlation (DIC) and finite element method. The work deals with methodical foundations for tree research during its felling. The DIC method measured seven trees in the forest when felling. Using the results obtained by this experiment, the numerical model was validated. This comparison suggested higher rigidity of the body using the finite element method compared to the actual tree, but the reaction was similar. With respect to the higher stiffness, the model was used to describe the deformation field inside the tree and to describe the effect of each cut on this field. The thesis also draws attention to the methodological errors that can occur during felling and which have been described in the experiment. Another output is an indication of the direction in which further measurements should be made and the errors that occurred during this measurement to avoid repetition.
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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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