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1
Content available Prediction of concrete life under coupled dry and wet-sulfate erosion based on damage evolution equation
Nie Nan
Archives of Civil Engineering
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2023
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Vol. 69, nr 4
679--692
EN
In a corrosive environment with coupled dry-wet-sulfate action, concrete structures are susceptible to erosion by sulfate ions, which seriously affects the safe operating life. To forecast the operational lifetime of concrete below the influence of the dry-wet cycle and sulfate erosion environment, four different admixtures of polypropylene fiber: 0, 0.6, 0.9, and 1.2 kg/m3, were incorporated into concrete specimens, and indoor accelerated tests were designed to observe the macroscopic and microscopic deterioration law analysis of concrete specimens; using the precept of damage mechanics, the damage of concrete under solubility cycle was established. The damage evolution equation of concrete under freeze-thaw cycles was established and the operational life of concrete was predicted. The results showed that the overall mass loss rate of concrete specimens increased with the number of tests, and the relative energetic modulo decreased with the number of tests; the pore change pattern, microstructure, and internal material composition of specimens under different working conditions were obtained by using NMR scanning technique, SEM electron microscope scanning technique and XRD physical phase analysis technique. The damage evolution equation shows that adding a certain amount of polypropylene fiber to concrete can improve the working life of concrete under dry and wet connected sulfate assault.
2
Content available Simulating progressive damage of notched composite laminates with various lamination schemes
Mandal B., Chakrabarti A.
International Journal of Applied Mechanics and Engineering
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2017
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Vol. 22, no. 2
333--347
EN
A three dimensional finite element based progressive damage model has been developed for the failure analysis of notched composite laminates. The material constitutive relations and the progressive damage algorithms are implemented into finite element code ABAQUS using user-defined subroutine UMAT. The existing failure criteria for the composite laminates are modified by including the failure criteria for fiber/matrix shear damage and delamination effects. The proposed numerical model is quite efficient and simple compared to other progressive damage models available in the literature. The efficiency of the present constitutive model and the computational scheme is verified by comparing the simulated results with the results available in the literature. A parametric study has been carried out to investigate the effect of change in lamination scheme on the failure behaviour of notched composite laminates.
3
Content available The Problem of Airflow Around Building Clusters in Different Configurations
Jędrzejewski M., Poćwierz M., Zielonko-Jung K.
Archive of Mechanical Engineering
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2017
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Vol. LXIV, nr 3
401--418
EN
In the paper, the authors discuss the construction of a model of an exemplary urban layout. Numerical simulation has been performed by means of a commercial software Fluent using two different turbulence models: the popular k-ε realizable one, and the Reynolds Stress Model (RSM), which is still being developed. The former is a 2-equations model, while the latter – is a RSM model – that consists of 7 equations. The studies have shown that, in this specific case, a more complex model of turbulence is not necessary. The results obtained with this model are not more accurate than the ones obtained using the RKE model. The model, scale 1:400, was tested in a wind tunnel. The pressure measurement near buildings, oil visualization and scour technique were undertaken and described accordingly. Measurements gave the quantitative and qualitative information describing the nature of the flow. Finally, the data were compared with the results of the experiments performed. The pressure coefficients resulting from the experiment were compared with the coefficients obtained from the numerical simulation. At the same time velocity maps and streamlines obtained from the calculations were combined with the results of the oil visualisation and scour technique.
4
Content available Experimental Study on the Riveted Joints in Glass Fibre Reinforced Plastics (GFRP)
Bielawski R., Kowalik M., Suprynowicz K., Rządkowski W., Pyrzanowski P.
Archive of Mechanical Engineering
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2017
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Vol. LXIV, nr 3
301--313
EN
The aim of the paper is to validate the use of measurement methods in the study of GFRP joints. A number of tests were carried out by means of a tensile machine. The studies were concerned with rivet connection of composite materials. One performed two series of tests for two different forces and two fibre orientations. Using Finite Element Method (FEM) and Digital Image Correlation (DIC), strain maps in the test samples were defined. The results obtained with both methods were analysed and compared. The destructive force was analysed and, with the use of a strain gauge, the clamping force in a plane parallel to the annihilated sample was estimated. Destruction processes were evaluated and models of destruction were made for this type of materials taking into account their connections, such as riveting.
5
Content available remote Influence of exponent in damage evolution equation on the accuracy of damage modelling in brittle materials
Mika P.
Engineering Transactions
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2015
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Vol. 63, iss. 4
463--479
EN
This paper analyses the influence of nonlinearity of the damage evolution equation that is introduced by exponent to the results obtained in the simulation of elastic-brittle material. Constitutive equation of linear-elastic medium with damages is described by the linear-tensorial function due to damage tensor. The nucleation and growth of microdamages are modelled using a two-parameter equation of damage evolution, in which the current level of damage is expressed by the principal values of Vakulenko-Kachanov and Murakami-Ohno damage tensors. The study examines a relationship between the time of the first macro crack appearance, principal values of damage tensor at the critical moment and the exponent adopted to the equation of damage evolution. The subjects of the analysis are changes in both the qualitative and quantitative variables characterizing the damage.
6
Content available remote Modelowanie konstrukcji powłokowej z uwzględnieniem procesu rozwoju uszkodzeń
Mika P.
Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska
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2011
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z. 58, nr 3/II
405-412
PL
Rozwój metod numerycznych i dostępność szybkich komputerów umożliwia zastosowanie coraz bardziej złożonych modeli teoretycznych zaimplementowanych w programach komputerowych (np. ABAQUS, [1], pozwalających na projektowanie z wykorzystaniem rezerw nośności konstrukcji. Modele te pozwalają na analizę nukleacji, wzrostu i propagacji mikrouszkodzeń w warunkach pełzania, prowadzących w konsekwencji do formowania się makrouszkodzeń, a w drugim etapie do propagacji makropęknięć tworzących front zniszczenia. Podstawowym problemem projektowym będzie takie ujęcie zagadnienia, by w przewidywanym czasie eksploatacji konstrukcji nie dopuścić do zapoczątkowania drugiego etapu eksploatacji, natomiast w przypadku pojawienia się pierwszych makropęknięć należy określić czas pozostały do całkowitego zniszczenia przekroju nośnego. W pracy przeprowadzono badania możliwości opisu konstrukcji powierzchniowych, w warunkach ewolucji kruchego uszkodzenia, przez przyjęty model matematyczny. Zastosowano tensorowy model konstytutywny [2], z uwzględnieniem zmiennej sztywności materiału opisanej tensorem uszkodzeń, włączony do programu ABAQUS w procedurze użytkownika UMAT. Otrzymane wyniki dowodzą możliwości praktycznego zastosowania przyjętego sformułowania konstytutywnego do modelowania konstrukcji inżynierskich.
EN
Engineering structures frequently exhibit changeable stress fields, caused by e.g. micro crack growth. As a consequence of this growth the deterioration of material properties, such as rupture toughness, strength, rigidity and lifetime reductions should be modelled. The process of damage growth usually accelerates after the first crack appears, followed by macrocracks, which combine together changing the structure thickness. The numerical study of this phenomenon is proposed with a special interest in the time of initial macroscopic cracks appearance at a point, the location of the first cracks and rupture front propagation, the physical properties of the structure material which affect the possible mechanisms of the damage front development and the mode of the failure front propagation. A way of numerical modeling of the failure front propagation in structures is of particular interest addressed in this study.
7
Modelling of damage accumulation for complex loading
Szusta J., Seweryn A.
Modelling and Optimization of Physical Systems
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2010
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z. 9
85--86
8
Content available remote Zmienna uszkodzenia D dla skał - część 1. Wybrane metody oznaczania zmiennej D
Tomiczek K.
Budownictwo Górnicze i Tunelowe
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2009
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nr 3
12-17
PL
W tej części artykułu przedstawiono metody oznaczania zmiennej uszkodzenia D, opisującej stopień uszkodzenia materiału skalnego, proponowane przez Lemaitre’a oraz Ju i Xie. Zwrócono uwagę na różnice w wartościach współczynnika odkształcalności podłużnej (modułu Younga) E dla materiału dziewiczego i uszkodzonego, wynikające z kształtu i przebiegu charakterystyk naprężenie – odkształcenie, oznaczonych w próbach jednoosiowego monocyklicznego i wielocyklicznego rozciągania. Zaproponowano cztery sposoby oznaczania wartości zmiennej uszkodzenia D, opierając się na wcześniejszych doświadczeniach Lemaitre’a, Ju i Xie.
EN
This part of the article presents the method of determining the damage variable D, describing the degree of damage to the rock material, proposed by Lemaitre and Ju and Xie, Attention was paid to the differences in the values of the coefficient of longitudinal deformability (Young's modulus) E for the virgin and damaged material, resulting from the shape and the course of characteristics of the stress- strain, identified in samples of uni-axial mono-cyclic and multi-cyclic tensioning. It proposes four ways of determining the value of damage variable D, based on previous experiences by Lemaitre, Ju and Xie.
9
Analytical and experimental study of damage induced anisotropy of concrete
Litewka A., Bogucka J., Dębiński J.
Foundations of Civil and Environmental Engineering
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2002
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No. 2
101-124
EN
Deformation and damage induced anisotropy of initially isotropic brittle material was studied experimentally for uni-axially compressed concrete. In this specific case a transverse isotropy, characterised by the plane of isotropy perpendicular to the direction of the compressive load, is developed in the loading process. Modification of the material constants in the loading process was analysed experimentally by employing the strain gauge technique combined with the ultrasonic pulse velocity measurements. The experimentally determined stress strain curves as well as the respective values of material constants were compared with the theoretical predictions. The validity of the respective constitutive equations proposed was verified by using the available experimental results for concrete subjected to bi-axial and to tri-axial state of stress.
PL
Rozwój anizotropii materiału pierwotnie izotropowego, spowodowany jego odkształceniem, został przebadany doświadczalnie w betonie poddanym osiowemu ściskaniu. W tym szczególnym przypadku następuje rozwój izotropii transwersalnej, charakteryzującej się płaszczyzną izotropii prostopadłą do kierunku ściskania. Zmiana stałych materiałowych, zachodząca w procesie obciążenia, była mierzona doświadczalnie z użyciem tensometrów elektrooporowych i z równoczesnym pomiarem prędkości fal ultradźwiękowych. Otrzymane doświadczalnie krzywe ściskania, jak też krzywe zależności stałych materiałowych od obciążenia porównano z przewidywaniami teoretycznymi. Poprawność zaproponowanych równań konstytutywnych została zweryfikowana z użyciem dostępnych wyników doświadczalnych dla betonu poddanego płaskiemu i przestrzennemu stanowi naprężenia.
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