1,721,165 research outputs found
The stress analysis for a crack with its tip at an interface between two materials
No full textThe problem of arbitrarily oriented crack terminating at the boundary of two bonded materials is studied from the point of view of linear elastic fracture mechanics
Calculation of Fatigue Crack Lengths from CMOD Measurement Performed on Concrete 3PB Specimens
No full textThe fatigue of cement based composites is now one of the progressive branches in research. To describe fatigue crack growth quantitatively it is necessary to know the values of materials parameters for Paris-Erdogan law. In cement based composites it is difficult to measure crack lengths directly. Therefore the crack mouth opening displacement (CMOD) is measured and then recalculated to crack lengths. The aim of the present article is to find the relation between CMOD and the corresponding crack length for three point bend (3PB) specimen by using cohesive model that is implemented in ATENA softwar
Application of the Williams expansion near a bi-material interface
No full textA simplified model of a crack approaching a bi-material interface is modelled by means of the finite element method in order to investigate the significance of the higher-order terms of the Williams expansion for the proper approximation of the opening crack-tip stress near the bi-material interface. The discussion on results is presented and the importance of the higher-order terms proved
Numerical Study of Influence of Quality Fem Mesh in the Vicinity of Bi-Material Interface on Loading Force Values: Push-out Test
No full textThe contribution is focused on numerical study of influence of quality FEM (finite element method) mesh on values of the maximum load forces for a Push-out test. The Push-out test is used for assessment the mechanical properties of the connection between the two materials, in the study case the interface of concrete and steel. Software ATENA 2D is used for numerical simulatio
Numerical support for wedge splitting test on non-traditional geometry
No full textBakalářská práce je zaměřena na numerickou podporu netradičního štípacího testu. Numerická analýza je provedena v programu ANSYS pro tělesa s různými vstupními parametry a vyhodnocení jejich chování při štípacím testu. Sledované jsou výsledné hodnoty parametrů charakteristických pro výpočty lomové mechaniky; faktor intenzity napětí a T-napětí a jejich funkcích v závislosti na délce sledované trhliny, jejichž průběh je graficky znázorněn.Bachelor thesis is focused on numerical support of wedge splitting test with non-traditional geometry. Numerical analysis takes place in program Ansys, defining behavior of models with modified entry parameters. Attention is focused on values of parameters characteristic for fracture mechanics; stress intensity factor and T-stress and functions describing their relationship to length of crack, evaluation of which is graphically illustrated.
Basic features of aggregate-matrix-interface fracture of selected building composites
No full textThe aim of this work is to analyze the behavior of cement composite, depending on the features of ITZ. The first part of the thesis is theoretical and deals with the origin and features of ITZ, defines the basic relationships and concepts of continuum mechanics and linear elastic fracture mechanics and presents crack tips posibilities in the three-phase composite, including their short characterization. The second part is practical and describes creation of numerical model in the ANSYS software, presentation of partial results and compare of them. The result of this work is a comparison of the mean values of stress and amplitude of stress depending on the features of ITZ
Assessment of fatigue life of concrete
No full textThe bachelor thesis deals with the fatigue life of concrete and examination of fatigue tests. Another topic is the measurement and evaluation of crack growth rate by a newly discovered method using graphite and Arduino connected to an electrical circuit. With this method due to the low electric resistance of the graphite, we can discover accurate time of failure of the speciment and the resolution between the main crack and microcracks
Multi-filament yarns testing for textile-reinforced concrete
No full textThe scope of the presented master thesis was the experimental study of multi-filament yarns made of AR-glass and used for textile-reinforced concrete. The behavior under the tensile loading was investigated by laboratory tests. A high number of yarn specimens (over 300) of six different lengths (from 1 cm to 74 cm) was tested to obtain statistically significant data which were subsequently corrected and statistically processed. The numerical model of the multi-filament bundle was studied and applied for prediction of the yarn performance and for later results interpretation. The model of n parallel filaments describes the behavior of a bundle with varying parameters representing different sources of disorder of the response and provides the qualitative information about the influence of their randomization on the overall bundle response. The aim of the carried experiment was to validate the model presumptions and to identify the model parameters to fit the real load-displacement curves. Unfortunately, due to unsuccessful correction of measured displacements devalued by additional non-linear contribution of the unstiff experiment device the load-displacement diagrams were not applicable to model parameters identification. The statistical evaluation was carried only for the maximal load values and the effect of the specimen size (length) on its strength was demonstrated. The size effect curve did not exclude the existence of spatial correlation of material mechanical properties modifying the classical statistical Weibull theory
Analysis of stress state and failure in test specimens used for determination of fracture-mechanical parameters of quasi-brittle materials
No full textThe thesis is focused on a test on determination of the fracture-mechanical parameters of quasi-brittle materials, especially concrete. What is referred to as the wedge-splitting test is considered, for which a variety of shapes of notched specimen can be used. This work is exclusively focused on the cylinder-shaped specimen of diameter 150 mm and breadth of 100 mm. The test is performed virtually using Atena 2D FEM software. Progress of failure is observed during loading of the specimen for various notch lengths. The amount of energy released for the development the failure outside of the tested cross-sectional area (weakened by the notch) is quantified and the size of the fracture process zone is investigated. The described analysis is performed for several material sets witch differ in cohesive properties of the quasi-brittle material expressed via the so-called characteristic length. Suitable proportions of the test specimen are sought, in order to avoid the failure and thus also the energy dissipation outside of the specimen ligament area during the experimental tests, which shall lead to more accurate estimates of fracture-mechanical parameters of the tested material
Fracture process zone and energy dissipation during fracture of quassi-brittle materials
No full textThe work is focused on the comparison of selected fracture properties of quasi-brittle materials, particularly concrete, determined from results from tests on specimens of different sizes and notch lengths. The first part deals with the study of selected plasticity (failure) criteria and their testing within the mathematical package (MathCAD) for their later intended implementation in a program for estimation of the size and shape of the fracture process zone. Next part is devoted to numerical simulations of three-point bending test of notched beams. These simulations were performed using the ATENA FEM software. Results of the simulations are evaluated using fracture models; this thesis presents values of fracture parameters quantifying the amount of energy dissipated in the fracture process zone
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