Temat: failure criterion - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Calibration of the Ductile Failure Criterion for Nickel-Based Superalloys taking into Account the Localization of the Strain
Autorzy:: Madejski, B.
Socha, G.
Tematy:: equivalent plastic strain
tensile test
failure criterion; Pokaż więcej
Wydawca:: Sieć Badawcza Łukasiewicz - Instytut Lotnictwa
Powiązania:: https://bibliotekanauki.pl/articles/97929.pdf Link otwiera się w nowym oknie
Opis:: Static tension test allows characterization of material strength properties. This simple test provides input data for numerical calculation of structural components made of the tested alloy. Elastic, plastic and failure behavior of the structural component in question is simulated, using, for example, the FEM package, based on parameters obtained as the result of tensile testing. When using the results of the tensile test for modeling the material failure it is important to estimate correctly plastic strain corresponding to failure. It is common practice to use elongation of the specimen gage part for the calculation of failure strain. On the other side, the most popular ductile failure criterion used by engineers performing numerical simulation of the material’s behavior relies on the equivalent plastic strain as the criterial quantity. Those two parameters can differ significantly. In order to calculate the equivalent plastic strain correctly, we have to remember about strain localization (necking) appearing during tensile tests and take into account the fact that during tensile testing we have three non-zero strain tensor components. Ignoring this fact, and using only elongation as the criterial quantity can lead to enormous simulation error. This error is analyzed in this paper for nickel based superalloy tested at elevated temperatures.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Experimental and numerical analysis of aluminum alloy AW5005 behavior subjected to tension and perforation under dynamic loading
Autorzy:: Bendarma, A.
Jankowiak, T.
Łodygowski, T.
Rusinek, A.
Klósak, M.
Tematy:: aluminum alloy
AW5005
ballistic behavior
failure criterion; Pokaż więcej
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:: https://bibliotekanauki.pl/articles/280547.pdf Link otwiera się w nowym oknie
Opis:: The paper describes mechanical behavior of aluminum alloy AW5005 (EN AW5005) under impact loading. The work is focused on tensile tests and the process of perforation of aluminum alloy AW5005 sheets. Experimental, analytical and numerical investigations are carried out to analyse in details the perforation process. Based on these approaches, ballistic properties of the structure impacted by a conical nose shape projectile are studied. Different failure criteria are discussed, coupling numerical and experimental analyses for a wide range of strain rates. Optimization method functions are used to identify the parameters of the failure criteria. Finally, good correlation is obtained between the numerical and experimental results for both tension and perforation tests.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Failure criterion for brick masonry: a micro-mechanics approach
Autorzy:: Kawa, M.
Tematy:: strength anisotropy
micromechanics
masonry microstructure
masonry
failure criterion; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/178604.pdf Link otwiera się w nowym oknie
Opis:: The paper deals with the formulation of failure criterion for an in-plane loaded masonry. Using micro-mechanics approach the strength estimation for masonry microstructure with constituents obeying the Drucker–Prager criterion is determined numerically. The procedure invokes lower bound analysis: for assumed stress fields constructed within masonry periodic cell critical load is obtained as a solution of constrained optimization problem. The analysis is carried out for many different loading conditions at different orientations of bed joints. The performance of the approach is verified against solutions obtained for corresponding layered and block microstructures, which provides the upper and lower strength bounds for masonry microstructure, respectively. Subsequently, a phenomenological anisotropic strength criterion for masonry microstructure is proposed. The criterion has a form of conjunction of Jaeger critical plane condition and Tsai-Wu criterion. The model proposed is identified based on the fitting of numerical results obtained from the microstructural analysis. Identified criterion is then verified against results obtained for different loading orientations. It appears that strength of masonry microstructure can be satisfactorily described by the criterion proposed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Effect of increasing mining rate on longwall coal mining – Western Donbass case study
Autorzy:: Sdvyzhkova, O.
Patyńska, R.
Tematy:: rock
stress-strain state
mining rate
failure criterion
roof collapse; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/178393.pdf Link otwiera się w nowym oknie
Opis:: This paper presents the problems associated with the rapid change of the rock stress-strain state in terms of increasing the rate of coal mining. Parameters of the roof collapse are determined depending on the rate of a longwall advancing under conditions of poor rocks. Statistical data are processed to obtain a general trend concerning the mining rate impact on the roof collapse. The statistical strength theory is applied to explain the increase in mined-out space and the size of hanging roof behind a coal face. Numerical simulation is carried out to determine a critical size of mined-out space that provokes a roof collapse. The area of yielded rocks is outlined using the criterion developed taking into account the rate of longwall advancing. A general regularity is obtained to determine the roof collapse parameters. The developed technics gives a possibility to predict the moment of general roof collapse at the initial stage of longwalling to prevent the negative effect of the rapid stress redistribution provoking joints propagation and intensive gas release. The estimation of the rock stress-strain state considering the rate of mining operations can be useful for tasks related to a new technology implementation. The statistical strength theory and failure criterion applied together provides adequate planning of mining activities and the assessment of natural hazards.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Influence of an empirical Geological Strength Index method for determining linear and nonlinear failure criteria
Autorzy:: Vivanco, Angélica
Avendaño, Eslainer
Tematy:: failure criterion
Hoek–Brown
Mohr–Coulomb
GSI
Geological Strength Index; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Wydział Geoinżynierii, Górnictwa i Geologii. Instytut Górnictwa
Powiązania:: https://bibliotekanauki.pl/articles/58972491.pdf Link otwiera się w nowym oknie
Opis:: The construction of tunnels and underground galleries in mining has as fundamental input data the results of the failure criteria: traditionally Hoek–Brown and Mohr–Coulomb, to determine the failure envelopes that will allow the design of an economically exploitable mining system within viable safety frameworks that these criteria will guide. Therefore, the determination of rock mass resistance becomes fundamental and complex simultaneously due to the very nature of rock mass. Then, to identify a stressful state in which an excavation can be in conditions of stability it is necessary to have certain information both high in quality and economically valuable, which is not available in the early stages of the mining project. Thus, empirical methods and statistical relationships take notoriety, so this research evaluates the influence of an empirical method for the determination of the Geological Strength Index on the Mohr–Coulomb and Hoek–Brown failure criteria, with the benefit of estimating a stress field in which the excavation can self-sustain, evaluated in a first estimate in the pre-feasibility stage of the project, giving a guideline for design engineers. This research argues that the Geological Strength Index estimation method of Vivanco and Avendaño is recommended to estimate the Mohr–Coulomb failure criterion, but not the Hoek–Brown failure criterion.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Three-dimensional biomechanical modeling and simulation of trephine cutting cornea for keratoplasty
Autorzy:: Su, P.
Lu, D.
Deng, S.
Zhang, L.
Hao, Y.
Yang, Y.
Tematy:: rogówka
biomechanika
kryterium wytężeniowe
FEM
cornea
biomechanics
failure criterion
finite element simulation; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/307486.pdf Link otwiera się w nowym oknie
Opis:: Trephination is one of the basic operations of keratoplasty, and the biomechanical mechanism of the operation can be revealed based on three-dimensional modeling and simulation of trephine cutting cornea. Methods: Based on the analysis of the physical and biomechanical characteristics of corneal trephination, a three-dimensional numerical model of corneal trephination is built, where the cornea can be simplified to two layers structure including stroma and epithelium, and the trephine cuts the cornea under the vertical motion load and the rotational motion load. A three-dimensional failure criterion of corneal material is proposed based on the yield strength theory. On this basis, trephination simulation is carried out, and the units of corneal material are removed from the model when they meet the defined failure criterion. Results: Under the given parameters including the velocity, the angle and the angular velocity, the trephine force curves, include the linear cutting force and the rotary cutting force are obtained, and show the change of the forces with displacement during the process of trephination simulation. The maps of the equivalent stress show the destruction and deformation of the cornea. Then, the experiment of robotic trephination is carried out under the same parameters and the effectiveness of the simulation is evaluated. Conclusions: Based on mechanics theory and finite element method, the process of trephine cutting cornea has been reproduced, and the interaction mechanism is revealed, which lays the foundation for the development of real-time simulation and virtual system of the corneal surgery.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Evaluation of the impact of hydrostatic pressure and Lode angle on the strength of the rock mass based on the Hoek–Brown criterion
Autorzy:: Marczak, H.
Tematy:: generalized Hoek–Brown failure criterion
equivalent cohesion
equivalent friction angle
global strength
invariant stress; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/178623.pdf Link otwiera się w nowym oknie
Opis:: Determination of the global uniaxial compressive strength of rock mass on the basis of the Hoek–Brown failure criterion requires knowledge of the strength parameters: cohesion and the angle of internal friction. In the conventional method for the determination of these parameters given by Balmer, they are expressed by the minimum principal stress. Thus, this method does not allow for the assessment of an impact of hydrostatic pressure and stress path on the value of cohesion, friction angle and global uniaxial compression of rock mass. This problem can be eliminated by using the Hoek–Brown criterion expressed by the invariants of the stress state. The influence of hydrostatic pressure and the Lode angle on the strength parameters of the rock mass was analysed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Kryterium wytrzymałości geomateriałów z mikrostrukturą warstwową
Failure criterion of geomaterials with microstructure of layered type
Autorzy:: Kawa, M.
Łydżba, D.
Tematy:: mikrostruktura warstwowa
anizotropia
kryterium wytrzymałości
teoria homogenizacji
microstructure of layered type
anisotropy
failure criterion
homogenization theory; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/349226.pdf Link otwiera się w nowym oknie
Opis:: W artykule przedstawiono anizotropowe kryterium wytrzymałości geomateriałów z mikrostrukturą warstwową. Rozważana mikrostruktura to periodyczny dwuskładnikowy ośrodek warstwowych, w którym wytrzymałość poszczególnych składników opisuje warunek Druckera-Pragera. Proponowane kryterium to koniunkcja anizotropowego kryterium Pariseau oraz równania płaszczyzny krytycznej. Przydatność postulowanego opisu zweryfikowano wykorzystując teorię homogenizacji. Parametry materiałowe są zdefiniowane w artykule w sposób analityczny, w funkcji parametrów wytrzymałościowych składników struktury. Jako przykład zastosowania kryterium przedstawia się rozwiązanie zagadnienia nośności granicznej podłoża uwarstwionego w funkcji kąta upadu warstw. Zaprezentowane wyniki pokazują istotny wpływ anizotropii wytrzymałości materiału na rozwiązanie zagadnienia brzegowego.
The paper presents anisotropic failure criterion of geomaterials with microstructure of layered type. The microstructure is considered as composed of two constituents periodically distributed in the space. Both constituents are assumed to be isotropic with strength ruled by Druckcr-Prager criterion. The overall strength condition proposed is a conjunction of Pariseau anisotropic failure criterion and critical plane equation. Usefulness of this description is verified based on the homogenization theory procedure. Material constants are defined, in an analytical form, as a function of strength parameters of the constituents. As an example of criterion application the results of load carrying capacity of layered soil are presented for different orientations of layers. The results clearly show influence of strength anisotropy of material on the solution of boundary-value problem.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: An annual cycle of changes in water temperature as a cause of cracking in massive concrete hydraulic structures
Roczny cykl zmian temperatury wody jako przyczyna pękania w masywnych konstrukcjach betonowych budowli hydrotechnicznych
Autorzy:: Łydżba, D.
Różański, A.
Sobótka, M.
Tematy:: budowla hydrotechniczna
elektrownia wodna
naprężenia cieplne
wpływ temperatury
HPP
hydropower plant
thermal stresses
temperature changes
failure criterion; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/348677.pdf Link otwiera się w nowym oknie
Opis:: The paper deals with the problem of temperature effect on a massive concrete hydraulic structure. The article is split into two parts. In the first part is an investigation concerning temperature distribution in a concrete wall of a hydraulic structure due to annual changes in water temperature. The conclusion of these considerations is that the temperature distribution in the concrete element, due to slow annual changes in temperature of flowing water, is almost uniform in space. The advantage of this fact is taken into consideration in another part in which the results of a numerical analysis concerning a HPP on the Vistula river is presented. Final conclusion is that water temperature changes can easily cause cracking in concrete hydraulic structures.
W artykule rozważany jest wpływ temperatury na masywne konstrukcje betonowe obiektów hydrotechnicznych. Praca składa się z dwóch zasadniczych części. W pierwszej określany jest rozkład temperatury występujący w betonowej ścianie budowli wodnej na skutek rocznych, wolnych zmian temperatury wody. Wniosek z tych rozważań, tj. że rozkład temperatury wewnątrz elementu betonowego jest prawie jednorodny jest wykorzystany jako założenie w drugiej części pracy. Analizie numerycznej poddana jest jedna z elektrowni wodnych na Wiśle. Z przeprowadzonych obliczeń wynika, że zmiany temperatury wody, występujące w klimacie charakterystycznym dla Polski, mogą prowadzić do powstawania pęknięć w betonowych elementach budowli hydrotechnicznych.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: The meaning of average compressive and tensile strength for Hoek-Brown mi constant determination
Autorzy:: Małkowski, Piotr
Niedbalski, Zbigniew
Tematy:: kryterium wytrzymałościowe Hoeka-Browna
wytrzymałość skały
skała
Hoek-Brown failure criterion
rock strength
laboratory tests on rocks; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:: https://bibliotekanauki.pl/articles/59111348.pdf Link otwiera się w nowym oknie
Opis:: One of the most widely used failure criteria for rocks in the world is the Hoek-Brown failure criterion. For its use, the mi empirical parameter for a specific rock type is needed. The triaxial compression test is recommended for its determination; however, the full stress path for every rock comprises confined tension as well. This affects the course of the Hoek-Brown envelope, which is non-linear and starts at uniaxial tension. Fifty-one series of tests were carried out for three rock types: sandstone, claystone and limestone, to show the difference between the results of the mi determination, using two different approaches – so-called linear and non-linear. Moreover, the consistency between the developed simplified methods of constant determination and mi were checked. These comprised the UCS-based method, R-index method, TS-based method and advanced regression functions of compressive and tensile strength. The relationship between mi constant and the internal friction angle was checked as well. The analysis of the results showed that the consistency with the regression models developed by researchers depends on the chosen estimator. If it is derived from the triaxial test only, the results are closer to a linear determination of mi constant and have a good correlation with internal friction angle. If both tensile and compressive strength are used for its determination, the non-linear value correlates better with the advanced regression functions, but quite poor with the average compressive strength (R-index method) and tensile strength (TS-based method). Taking into account that every rock retained next to the geotechnical or mining object is not only compressed but also tensed, the non-linear mi interpretation seems to be more correct. The interlayers and discontinuities inside sedimentary rocks increase the scatter of lab results and reduce the accuracy of mi determination.
Dostawca treści:: Biblioteka Nauki

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