Wyniki wyszukiwania - BazTech

1

The Computational Method of Predicting the Crack Path in Confrontation with Laboratory Tests

Gontarz Jakub, Podgórski Jerzy

Advances in Science and Technology. Research Journal

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2023

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Vol. 17, no 2

90--110

EN

The paper presents the results of laboratory tests and computer simulations of the pull-out test of a rod embedded in a concrete cylindrical sample. The main purpose was to verify the force-displacement relationship and the crack paths. The X-FEM method of fracture simulation was used. The authors compared a simple maximum principal stress criterion, as well as their own method of simulating fracture propagation in brittle materials, implemented with the user subroutine in the Simulia Abaqus FEA system. A number of conclusions were obtained in the analyzes, related to the influence of the finite element mesh size, the method of modeling the rod and its contact with concrete. The advantages of own method were presented. the reasons for the differences between the results of simulations and laboratory tests were presented.

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Simulation of the Griffith's Crack Using Own Method of Predicting the Crack Propagation

Podgórski Jerzy, Gontarz Jakub

Advances in Science and Technology. Research Journal

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2021

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Vol. 15, no 4

1--13

EN

The paper presents the results of numerical simulation of brittle material fracture initiated by Griffith's crack situated at any angle with respect to the load direction. The simulations were performed with the Simulia Abaqus FEA system using the X-FEM method. The direction of the crack propagation was determined using the user's subroutine written in Fortran, implemented in the Abaqus system. The authors programmed several conditions for the direction of the fracture propagation: maximum principal stress criterion, Ottosen-Podgórski criterion, three criteria based on displacements around the crack tip, and the MTS criterion, which is based on stress intensity factors. For the purposes of this study, two shapes of the crack tip were analyzed - sharp and blunted. The relationship between the direction of the initial fracture and the direction of crack propagation was found. The simulations were carried out for the angles of the initial crack from 0° to 90°, every 10°. A theoretical analysis of the implemented criteria was also carried out and compared to numerical results. The influence of the shape of the crack tip on the simulation result was analyzed. It was shown that the simulation results closest to the theoretical results were obtained for the own implementation of the stress-based criteria. It has also been proven that the shape of the crack tip has little effect on the result if the finite element mesh is properly densified. However, the sharp crack has a disadvantage for small initial crack angles. The Author’s method of predicting the crack propagation has been proven correct and effective. This work is also the basis for the further development of the described method.

3

Simulation of four-point beam bending test using the X-FEM method

Gontarz Jakub, Podgórski Jerzy

Budownictwo i Architektura

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2020

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Vol. 19, no 3

57--67

EN

This article presents the results of the computer simulations of a four-point bending test of a concrete single-edge notched beam. In this publication, the authors compared the X-FEM method of simulating the crack in the Abaqus FEA system. The paper also contains the results obtained with the Abaqus subroutine recently developed by the authors, used for defining the direction of the crack and the failure criterion. The publication explains the way of working of this algorithm. The described calculations show that computer analysis gives unrealistic results in terms of the destructive force. SEN-beam is an interesting laboratory test in which a lot of factors influence the results. It is especially important to study what phenomena occur in the final phase of the study, when the crack tip is near the opposite side.

PL

Artykuł ten przedstawia wyniki symulacji komputerowych testu czteropunktowego zginania betonowej belki z nacięciem (belka SEN). W tej pracy autorzy porównali metodę symulowania propagacji szczeliny X-FEM w systemie Abaqus FEA. Ponadto zawiera ona wyniki uzyskane z nowej autorskiej subrutyny programu Abaqus, odpowiedzialnej za definiowanie kierunku propagacji szczeliny i kryterium zniszczenia. Praca opisuje również zasadę działania tego algorytmu. Opisywane obliczenia pokazują, że komputerowa analiza daje wyniki siły niszczącej dalekie od rzeczywistości. Belka SEN jest ciekawym badaniem laboratoryjnym, w którym na wynik ma wpływ wiele czynników. Szczególnie ważne jest zbadanie zjawiska występującego w końcowej fazie symulacji, kiedy wierzchołek szczeliny jest blisko krawędzi.

4

Report on laboratory tests of sandstone and porphyry for rock fracture analysis

Gontarz Jakub, Szulej Jacek

Budownictwo i Architektura

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2020

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Vol. 19, no 2

87--100

EN

The paper presents the results of mechanical tests of three types of rocks from stone mines in Poland. Compression tests of cubic samples, three-point bending tests of beams, bending of beams with notch and testing of tensile strength using the quasi-Brazilian method were performed. Based on the tests, the compressive strength, tensile strength, Young's modulus, and Poisson's ratios were determined. The stress intensity factor and critical strain energy release rate in mode I were determined from the bending test of the notched beams. The determined values were used as parameters of computer models which are used to verify the authors’ method of predicting the crack propagation in the Abaqus FEA system.

PL

Artykuł prezentuje wyniki badań laboratoryjnych trzech typów skał z kopalni kamienia w Polsce. Wykonano badanie ściskania kostek, badanie trójpunktowego zginania belek, zginania belek z nacięciem i badanie rozciągania przy rozłupywaniu metodą kwazi-Brazylijską. Na podstawie badań uzyskano wytrzymałość na ściskanie, wytrzymałość na rozciąganie, moduł Younga i współczynnik Poissona. Współczynnik intensywności naprężenia i krytyczna energia pękania w modzie I zostały uzyskane z badań zginania belek z nacięciem. Uzyskane wyniki zostały użyte jako parametry do modeli komputerowych, które są używane do weryfikacji autorskiej metody przewidywania propagacji szczeliny w systemie Abaqus.

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Analysis of crack propagation in a "pull-out" test

Gontarz Jakub, Podgórski Jerzy

Studia Geotechnica et Mechanica

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2019

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Vol. 41, nr 3

160--170

EN

The article describes a computer analysis of the pull-out test used to calculate the force needed to pull out a rock fragment and determine the shape of this broken fragment. The analyzed material is sandstone and porphyry. The analysis included the first approach to using own subroutine in the Simulia Abaqus system, that is, which task is undertaken to accurately determine the crack path of the Finite Element Method model. The work also contains a description of laboratory tests and analytical considerations.

6

Comparison between numerical analysis and actual results for a pull-out test

Gontarz Jakub, Podgórski Jerzy, Jonak Józef, Kalita Marek, Siegmund Michał

Engineering Transactions

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2019

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Vol. 67, iss. 3

311--331

EN

The paper describes a computer analysis of the pull-out test used to determine the force needed to pull out a fragment of rock and the shape of this broken fragment. The analyzed material is sandstone and porphyry. The analysis included a comparison of different methods of propagation of cracks in the Abaqus computer program using the Finite Element Method. The work also contains a description of laboratory tests and analytical considerations.