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AA5052 failure prediction of electromagnetic flanging process using a combined fracture model

Deng Huakun, Mao Yunfei, Li Guangyao, Zhang Xu, Cui Junjia

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e84, 1--17

EN

Electromagnetic forming process could significantly increase the forming limit of aluminum alloy. However, high-speed fracture prediction of aluminum alloys is a major problem in the development of electromagnetic flanging process. In this study, notched specimen tensile tests with high-speed Digital Image Correlation system were conducted under the strain rate range from 0.001 to 100 s-1. A fracture model of AA5052 alloys which combined of an uncoupled fracture model, Gissmo damage evolution model and Johnson-Cook strain rate effect was established. Electromagnetic flanging experiments were conducted to verify the failure criteria effectiveness. Results showed that failure strain was significantly influenced by strain rate under various loading path. Compared with the experiments, the percentage error of established electromagnetic flanging process FEM model was less than 4%. The fracture model established could well predict notched specimen high-speed failure, and also accurately predict sheet failure model of electromagnetic flanging experiments and, thus, verified the effectiveness of the established dynamic failure criteria in electromagnetic flanging process.

2

The overview of fracture mechanics models for concrete

Akram Amanda

Architecture Civil Engineering Environment

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2021

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Vol. 14, no. 1

47--58

EN

Fracture mechanics of concrete is a complex matter still thoroughly researched from different angles. It is not an easy task to describe fracture process in concrete, as there are many factors affecting crack development and propagation. Practical applications of fracture mechanics could allow engineers to design concrete structures more effectively and safely. At the minimum, it could help estimate the “safe” period of time left before the unstable, dangerous crack propagation. This utilitarian goal was the reason for many researchers to invent numerous theoretical models in order to describe the crack occurrence better. However, dealing with various analytical problems was not a simple matter and thus existing models of fracture mechanics for concrete have different limitations. Over the years first fracture theories for concrete were reviewed repeatedly. All of these investigations lead to modifications of older models in order to overcome found drawbacks, which proved not to be an easy task. Recently, new approaches to fracture analyses seemed to produce promising results, like universal size effect law (USEL) or modified two parameter fracture model (MTPM) with alternative ways for evaluating fracture parameters. In the paper some of them will be discussed together with other fracture models, starting from some of the very first ones introduced for concrete, like fictitious crack model (FCM) and crack band model (CBM).

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Analiza parametrów mechaniki pękania betonu z wykorzystaniem nowoczesnych technik komputerowych

Bernatowicz A.

Budownictwo i Inżynieria Środowiska

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2017

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Vol. 8, no. 1

7--13

PL

Wykorzystanie parametrów mechaniki pękania umożliwia bardziej ekonomiczne podejście do projektowania konstrukcji. Tradycyjne badania doświadczalne dostarczają wielu istotnych informacji dotyczących zarysowań oraz koncentracji naprężeń w obciążanych elementach. Wymagają one jednak dużej liczby czasochłonnych prób. Wstępne obliczenia przeprowadzone za pomocą programów komputerowych, pozwalają ograniczyć je do niezbędnego minimum. W niniejszej pracy przedstawiono przegląd dostępnych programów komputerowych wykorzystywanych do analizy parametrów mechaniki pękania. W ramach badań własnych, wykonano model próby rozciągania przy rozłupywaniu w programie Robot Structural Analysis oraz przeprowadzono weryfikację obliczeń w programie Abaqus. Przedmiotem badań był betonowy dysk osłabiony szczeliną prostą lub skośną, symulujący prosty lub złożony stan naprężeń w elemencie betonowym.

EN

The use of the parameters of fracture mechanics presents a new way of designing in civil engineering. Traditional laboratory research provides lots of important information connected to cracks and tension - concentration in loaded elements. On the other hand, tests are very time - consuming. Initial calculations by means of computer programmes allow to decrease amount of laboratory tests only to extreme minimum. The paper contains the overview of the most common computer programmes used for the analysis of parameters of fracture mechanics . Moreover, the own model of Brazilian test in computer programme called Robot Structural Analysis was created. The model verification was made in Abaqus CAE. Concrete discs with straight or inclined crack in the middle, which simulates simple ‒ or mixed ‒ tension conditions in concrete element, were used as the subject of the study.

4

Odporność na pękanie przy skręcaniu betonu z popiołami lotnymi

Golewski G. L.

Materiały Budowlane

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2016

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nr 10

28--29

PL

W artykule przedstawiono wyniki badań wpływu dodatku krzemionkowych popiołów lotnych (FA), w ilości 20 i 30% masy cementu, na proces pękania w betonie zwykłym przy skręcaniu (wg III modelu pękania). Badania odporności na pękanie przeprowadzono na prasie osiowo-skrętnej MTS 809. Oceniano wpływ dodatku FA na współczynnik intensywności naprężeń KIIIc. Badania wykonano na kompozytach młodych i dojrzałych (po 3, 7, 28, 90, 180 i 365 dniach). Dodatek FA zarówno w ilości 20%, jak i 30% powoduje spadek odporności na pękanie betonu młodego. Po 28 dniach dojrzewania betonu z 20% dodatkiem FA zanotowano wyraźny wzrost KIIIc, natomiast w przypadku betonu z 30% dodatkiem FA analizowany parametr mechaniki pękania miał niewielkie wartości.

EN

This paper presents results of tests on the effect of the addition of siliceous fly ashes (FA) in the amount of 20 and 30% by weight of cement on the fracture processe in plane concrete at torsion (Mode III fracture). Fracture toughness tests were performed on axial/torsional MTS 809 Test System. The studies examined the effect of FA additive on the parameter KIIIc. Experimental investigation was carried out both on young and mature concrete composites (after: 3, 7, 28, 90, 180 and 365 days). A 20% addition of FA as well as a 30% addition of FA causes a reduction in fracture toughness of young concrete. After 28 days of curing a significant increase of the KIIIc was noticed in composites with a 20% additive of FA while concrete mixtures with a 30% additive of FA still had lower analyzed fracture mechanics parameter.

5

Application of the fracture-band model to glacier seismic event series

Górski M.

Acta Geophysica Polonica

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2002

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Vol. 50, nr 3

373-379

EN

We present an application of the fracture-band model to the study of icequake series recorded in June 1999 at Hans glacier, Spitsbergen. The determination of seismicity of the glacier is based on two measurement networks. Using the calculated data of seismic moments, stress drops, and seismic radiated energies, we are able to calculate for each event in series the values of seismic efficiency, the total released energy, the ratio of tensile stress to shear stress, the ratio of source thickness to source radius, and the damage factor.

6

Earthquake fracture-band theory

Teisseyre R., Teisseyre K., Górski M.

Acta Geophysica Polonica

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2001

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Vol. 49, nr 4

463-479

EN

We present the theory of general structure of fracturing in an earthquake source; this new model is based on generalization of the shear band model presented in pervious papers. These models of the seismic source zone are based on the thermodynamics of line defects. In the thermodynamics of line defects the dislocation superlattice plays an essential role. The concept of line vacancy (vacant dislocation) enables us to construct a superlattice consisting of dislocations and vacant dislocations. The model introduced applies to plastic deformations; stress load increase may lead to some changes in dislocation density related to the superlattice. Such changes can also be related to a change of the number of vacant dislocations or to a change of the superlattice parameter. An increase of the number of dislocations corresponds in this case to a hardening process and is related to the spatial structure of superlattice. A pronounced plastic deformation is realized through the formation of shear bands; the dislocation number becomes multiplied along the shear planes and in consequence exceeds the number prescribed by the superlattice structure which, however, will be perservered in the direction perpendicular to the shear band planes. Our new generalization takes into account the tensile and shear fracturings forming the concurrent processes; however, some phase shifts between them shall be included. Moreover, in this paper the earthquake structure model may be not only related to the microdefect distribution, but also to an existence of macro-defects bound to a fine structure of focal region. This fine structure can be formed by some elements of the fracture space or by a certain distribution of the grains. Properties of such structures are described by the micromorphic theory. Moreover, we will not split, in a heuristic way, the deformations into the elastic and plastic parts, because the plastic phenomena are to some extent included here by the micromorphic or, as one can say, the granular/block structure properties of the medium. Applications for an analysis of earthquakes, mining tremors, volcanic events and icequakes are presented.