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Analysis of crack behaviour under mixed-mode loading
Antalík, Adam ; Miarka, Petr (referee) ; Malíková, Lucie (advisor)
This bachelor’s thesis deals with the analysis of the stress field in the vicinity of the crack tip, described by the stress intensity factor K. The objective of this thesis is to calculate values of the parameter K for a crack in a rectangular specimen subjected to asymmetric four-point bending. Thus, mixed mode I + II loading conditions occur. The first part of the thesis deals with the fracture mechanics concept. In the second part, a cracked specimen is modelled in the Ansys Mechanical APDL software. In the final part, the resulting values of the parameter K, obtained from the commands KCALC, CINT and two empirical equations, are presented. The MTS criterion is applied for estimation of the crack propagation angel and all results are discussed thoroughly.
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ANALYSIS OF MIXED MODE I/II FAILURE OF SELECTED STRUCTURAL CONCRETE GRADES
Miarka, Petr ; Šejnoha,, Michal (referee) ; Hutař,, Pavel (referee) ; Seitl, Stanislav (advisor)
The presented thesis is devoted to the experimental and numerical analysis of concrete fracture under the mixed-mode I/II load. This phenomenon was analysed on various concrete grades and types which are used in the fabrication of precast concrete structural elements. Subsequently, the Brazilian disc test with central specimen was used in experimental and numerical parts. The numerical part employs both linear elastic fracture mechanics (LEFM) approach and non-linear material model to assess the concrete fracture and failure under the mixed mode I/II load. The LEFM part is dedicated to evaluation the geometry functions and higher order terms of the Williams’ expansion, while the non-linear analysis is dedicated to crack initiation and propagation throughout the specimen using the concrete damage plasticity model. The experimental part is dedicated to the analysis of the mixed mode-mode I/II fracture resistance by the generalised tangential stress (GMTS) criterion with focus set on the governing role of the critical distance rC. Furthermore, the experimental part validates the applicability of the Williams’ expansion on the concrete. For this, experimentally measured displacements by digital image correlation technique were used to calculate the Williams’s expansion terms. Lastly, the thesis deals with the influence of the aggressive environment on the material’s fracture toughness and on the fracture resistance under the mixed mode I/II has been studied.
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NUMERICAL STUDY OF UNIVERSAL BEAM (I SECTION) UNDER BENDING LOAD WITH CRACK
Morán, Alvarez J. ; Seitl, Stanislav ; Miarka, Petr
The structural components often contain cracks as a results of applied load. Therefore, these cracks must be studied how they affect the structural behavior and the total service life-time of the component. Bearing beams of the bridges have usually cross-section in the shape of an I-profile. In this contribution, a numerical parametric model was made in order to study the influence of the crack length, Poisson's ratio and web thickness on the stress distribution in the structural element, for which a three-point bending specimen was applied. The model is based on the linear elastic fracture mechanics (LEFM), with focus set on the determination of the stress intensity factor, as it is one of the main parameters used in the description of the stress fields in vicinity of the crack tip.
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MULTI-PARAMETER MTS AND SED CRITERION APPLIED ON A CRACK IN AN ALKALI-ACTIVATED CONCRETE SPECIMEN UNDER MIXED-MODE LOADING
Malíková, Lucie ; Miarka, Petr ; Simonová, H.
The paper is devoted to an analysis of a crack propagation in a semi-circular concrete specimen under three-point bending. I+II mixed-mode loading is ensured via an inclined crack. Crack deflection angle is investigated by means of the generalized/multi-parameter form of the Maximum Tangential Stress (MTS) criterion and Strain Energy Density (SED) criterion as well as experimentally. The multi-parameter fracture mechanics concept applied in this work is based on the approximation of the crack-tip stress field by means of the Williams series expansion (WE). It has been proved that this approach can help to describe crack behavior in some kinds of materials better than the classical (one-parameter: stress intensity factor) fracture mechanics. This conclusion is discussed also in this paper.
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Advanced statistical evaluation of fatigue data obtained during the measurement of concrete mixtures with various water-cement ratio
Seitl, Stanislav ; Benešová, A. ; Blasón, S. ; Miarka, Petr ; Klusák, Jan ; Bílek, V.
The Basquin’s law is usually applied for the evaluation of fatigue properties of civil engineering \nmaterials. For materials like concrete, some researchers recommended applying the Weibull model. In this\ncontribution, Basquin’s law, Castillo-Canteli model and Kohout-Věchet model were applied for the advanced \nstatistical description of S−N curves (Wöhler curve). For the application of the models, the experimental data \nmeasured on reference concrete mixtures used for the development of self-healing concrete at the Faculty of \nCivil Engineering, TU Ostrava. Fitting data of applied models were compared and analyzed
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Analysis of crack behaviour under mixed-mode loading
Antalík, Adam ; Miarka, Petr (referee) ; Malíková, Lucie (advisor)
This bachelor’s thesis deals with the analysis of the stress field in the vicinity of the crack tip, described by the stress intensity factor K. The objective of this thesis is to calculate values of the parameter K for a crack in a rectangular specimen subjected to asymmetric four-point bending. Thus, mixed mode I + II loading conditions occur. The first part of the thesis deals with the fracture mechanics concept. In the second part, a cracked specimen is modelled in the Ansys Mechanical APDL software. In the final part, the resulting values of the parameter K, obtained from the commands KCALC, CINT and two empirical equations, are presented. The MTS criterion is applied for estimation of the crack propagation angel and all results are discussed thoroughly.
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Expected Fatigue Crack Propagation with Selected Geometric Shapes in IPE 80
Juhászová, Tereza ; Seitl, Stanislav ; Miarka, Petr
The focus of this contribution is to investigate fatigue behaviour of I cross-section beam. Stainless steel IPE beam with initiate concentrator is loaded in three point bending and the crack growth rate is analysed for various crack front shapes. Stress intensity factor size in the crack tip is being investigated in relation to growth rate of discontinuity. Load number of cycles is predictable basing on hypothesis of fatigue behaviour of material and the results are compared to experimental results of studies performed on compact tension specimen made from the similar material.
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ANALYSIS OF MIXED MODE I/II FAILURE OF SELECTED STRUCTURAL CONCRETE GRADES
Miarka, Petr ; Šejnoha,, Michal (referee) ; Hutař,, Pavel (referee) ; Seitl, Stanislav (advisor)
The presented thesis is devoted to the experimental and numerical analysis of concrete fracture under the mixed-mode I/II load. This phenomenon was analysed on various concrete grades and types which are used in the fabrication of precast concrete structural elements. Subsequently, the Brazilian disc test with central specimen was used in experimental and numerical parts. The numerical part employs both linear elastic fracture mechanics (LEFM) approach and non-linear material model to assess the concrete fracture and failure under the mixed mode I/II load. The LEFM part is dedicated to evaluation the geometry functions and higher order terms of the Williams’ expansion, while the non-linear analysis is dedicated to crack initiation and propagation throughout the specimen using the concrete damage plasticity model. The experimental part is dedicated to the analysis of the mixed mode-mode I/II fracture resistance by the generalised tangential stress (GMTS) criterion with focus set on the governing role of the critical distance rC. Furthermore, the experimental part validates the applicability of the Williams’ expansion on the concrete. For this, experimentally measured displacements by digital image correlation technique were used to calculate the Williams’s expansion terms. Lastly, the thesis deals with the influence of the aggressive environment on the material’s fracture toughness and on the fracture resistance under the mixed mode I/II has been studied.
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