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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.

2

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

3D FE analysis of the behavior of elliptical cracks on orthopedic cement of the total hip prosthesis

Benouis A., Zagane M. S., Boulenouar A., Serier B., Belgherras M. E.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 3

803--813

EN

An explicit analysis conducted on the crack behavior in chirurgical cement (Polymethylmethacrylate – PMMA) used for Total Hip Prosthesis (THP) is of great importance in collecting information about the nature of the phenomenon of loosening of the cement application. The rupture of the orthopedic cement is practically the main cause of this loosening. Understanding diﬀerent rupture mechanisms give a great value in advancing the durability of the cemented total prosthesis. The purpose of this study is to analyse cracks behavior, initiated in the cement that links the femoral-stem with the bone, using the Finite Element Analysis Method (FEM). The present study brings into focus the variation of the stress intensity factor in modes I, II and III. This rupture criterion is used according to the nature of crack, its orientation and its location in the orthopedic cement. At ﬁrst, the level and distribution of the equivalent von Mises stress is analysed, which is induced in the medial, proximal and distal parts of the bone cement. Then, the behavior of diﬀerent geometric forms of an elliptical crack is evaluated which are located and initiated within the body of these three parts.

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An estimation of the high-pressure pipe residual life

Jovicic G., Nikolic R., Zivkovic M., Milovanovic D., Jovicic N., Maksimovic S., Djordjevic J.

Archives of Civil and Mechanical Engineering

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2013

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Vol. 13, no. 1

36--44

EN

The paper presents an estimation of the residual life of the power plant high-pressure pipe, which has been in exploitation for years. A crack was noticed in the pipe, thus it was necessary to estimate the pipe material residual life until its eventual failure. The combined methodology for residual life estimation, which consists of experimental and numerical investigations, was developed. The samples were taken directly from the real high pressure pipe and material properties were determined experimentally, both at room and elevated (operational) temperature. The experimental results also served for the verification of the developed numerical methodologies. The FEM and the X-FEM methods were used for the residual life numerical estimation of the high pressure pipe. The stress and strain fields, used for the estimate, were obtained by application of the Paris' law. The final verification of numerical results was realized by comparing the critical crack length to the experimentally obtained value.

6

Numerical modelling of impact fracture of cortical bone tissue using X-FEM

Abdel-Wahab A. A., Silberschmidt V. V.

Journal of Theoretical and Applied Mechanics

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2011

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Vol. 49 nr 3

599-619

EN

A cortical bone tissue is susceptible to fracture that can be caused by events, such as traumatic falls, sports injuries and traffic accidents. A proper treatment of bones and prevention of their fracture can be supported by in-depth understanding of deformation and fracture behaviour of this tissue in such dynamic events. Parameters such as damage initiation under impact, damage progression and impact strength can help to achieve this goal. In this paper, Extended Finite-Element Method (X- FEM) implemented into the commercial finite-element software Abaqus is used to simulate the actual crack initiation and growth in a cantilever beam of cortical bone exposed to quasi-static and impact loading using the Izod loading scheme. Izod tests were performed on notched bone specimens of bovine femur to measure its impact strength and to validate simulations. The simulation results show a good agreement with the experimental data.

PL

Istota korowa kości jest tkanką podatną na złamanie wywołane m.in. takimi zdarzeniami jak upadki, kontuzje sportowe czy wypadki samochodowe. Odpowiednie leczenie czy profilaktyka stanu kości powinny być wsparte głębokim zrozumieniem zjawisk deformacji i pękania tej tkanki zachodzących podczas takich dynamicznych obciążeń. Znajomość parametrów opisujących inicjację uszkodzenia pod wpływem obciążenia uderzeniowego, progresja tego uszkodzenia i wreszcie odporność na złamanie może być pomocna w tej praktyce. W prezentowanej pracy przedyskutowano implementację rozszerzonej metody elementów skończonych (X-FEM) do standardowego i komercyjnego pakietu ABAQUS w celu symulacji faktycznych zjawisk towarzyszących inicjacji i propagacji pęknięcia belki wykonanej z materiału oddającego właściwości istoty korowej poddanej działaniu quasi-statycznych i uderzeniowych obciążeń, wspartej próbami udarnościowymi Izoda. Testy Izoda zostały przeprowadzone na przygotowanych próbkach z bydlęcej kości udowej z naciętym karbem w celu eksperymentalnej weryfikacji wytrzymałości na uderzenie. Rezultaty badań numerycznych wykazały dobrą zgodność z wynikami tych prób.