Wyniki wyszukiwania - BazTech

1

Numerical Modelling of a Rotary Compression Test on a Cylindrical Specimen

Pater Zbigniew

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no 4

23--32

EN

This paper reviews studies on the modelling of the Mannesmann effect, which leads to the formation of an axial crack in parts formed by cross and skew rolling. This effect also occurs in the rotational compression (RC) test of a cylindrical specimen, which is used to determine the critical damage value. RC tests were carried out under laboratory conditions at the Lublin University of Technology on C45 steel specimens formed at 950°C. Based on the tests, the crack propagation was presented as a function of the progress of rotational compression, measured by the length of the deformation path. The RC tests were numerically modelled in Forge® using four ductile fracture criteria. The effectiveness of the Mannesmann effect modelling was evaluated by comparing the numerically predicted cracks with the experimentally determined ones. In addition, the influence of an occurring axial crack on the stress state in the forming specimen was analysed.

2

The influence of a polyurea coating on bent reinforced concrete beams with various reinforcement ratios

Szafran Jacek, Matusiak Artur, Rzeszut Katarzyna, Jankowiak Iwona

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 1

art. no. e144579

EN

“Polyurea coatings as a possible structural reinforcement system” is a research project aimed at exploring possible applications of polyurea coatings for improving structural performance (including steel, concrete, wooden and other structures used in the construction industry). As part of the project, this paper focuses on evaluating the performance of bent reinforced concrete (RC) beams covered with a polyurea coating system. Easy polyurea application and its numerous advantages can prove very useful when existing RC structural elements are repaired or retrofitted. Laboratory tests of three types of RC beams with three different longitudinal reinforcement ratios were performed for the purposes of this paper. The tests were designed to determine the bending strength, performance and cracking patterns of the coated RC beams. In addition, a theoretical model was developed to predict the impact of the polyurea coating on the bending strength of the RC beams. On this basis, the effect of the coating on the bending strength and the performance of the coated beams at the ultimate limit state (ULS) was examined and analyzed. The results showed that the use of the polyurea coating has a positive impact on the cracking state of the RC beams subject to bending and little effect on their bending strength.

3

The impact of a polyurea layer on cracking and performance of reinforced concrete beams under breaking load

Szafran Jacek, Matusiak Artur, Rzeszut Katarzyna, Jankowiak Iwona

Structure and Environment

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2022

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Vol. 14, no. 3

76--82

EN

The paper discusses the results of laboratory experimental studies on reinforced concrete components (beams) with an outer polyurea layer. The important part of the study is the comparison of the results concerning the load-displacement relation for the reference beams (without the polyurea layer on their external surfaces) and those with the polyurea layer. The main conclusion from this part of the research is that the beam elements covered with a polyurea layer are protected against corrosion processes even in an emergency state. The occurrence of scratches, even of large size, is neutralized by the coating that effectively bridges them.

PL

W artykule zaprezentowano wyniki laboratoryjnych badań eksperymentalnych dotyczących elementów żelbetowych (belek) wraz z zewnętrzną warstwą polimocznika. Istotną częścią pracy jest porównanie wyników zależności obciążenie - przemieszczenie dla belek referencyjnych (bez warstwy polimocznika na powierzchniach zewnętrznych) oraz tych taką warstwę posiadającą. Kluczowym wnioskiem płynącym z tej części badań jest ten mówiący o tym, że elementy belkowe pokryte warstwą polimocznika zabezpieczone są przed korozją nawet w stanie awaryjnym. Występowanie rys nawet znacznych rozmiarów jest zneutralizowane poprzez skuteczne ich mostkowanie powłoką.

4

Analysis of causes of damage to single-layer concrete highway pavement

Glinicki Michał A., Jóźwiak-Niedźwiedzka Daria, Antolik Aneta, Dziedzic Kinga, Dąbrowski Mariusz, Bogusz Karolina, Lisowski Paweł

Roads and Bridges - Drogi i Mosty

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2022

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Vol. 21, no. 3

183--201

EN

Premature damage to the concrete pavement of a trunk road section after 15 years of its service life was noticed. The damage manifested itself in cracking along transverse joints and in the corners of slabs. Diagnostic investigations, covering a petrographic analysis of concrete and mineral aggregates by means of optical and scanning microscopy, an evaluation of the elastic properties, the degree of cracking and air-void parameters and an identification of the alkali-silica reaction products, were carried out on core samples. Multiple cracks in coarse quartzite aggregate particles and in cement matrix were found. A significant presence of microcrystalline and cryptocrystalline quartz in quartzite particles was detected. Typical alkali-silica reaction products were unambiguously identified. The considerable cracking and the substantial decrease in the modulus of elasticity were correlated with the presence of reactive quartz in the quartzite aggregate and the alkali-silica reaction was found to be the main cause of the damage. Additional damaging factors, such as heavy traffic loads and frost aggression, are discussed.

PL

Po 15 latach eksploatacji odcinka drogi ekspresowej zaobserwowano przedwczesne uszkodzenia nawierzchni betonowej objawiające się widocznymi spękaniami, głównie wzdłuż spoin poprzecznych oraz w narożach płyt. Na próbkach-odwiertach przeprowadzono badania diagnostyczne, obejmujące analizę petrograficzną betonu i kruszyw mineralnych przy użyciu mikroskopii optycznej i skaningowej, ocenę właściwości sprężystych, stopnia spękania i charakterystyki porów, a także identyfikację produktów reakcji alkalia-krzemionka. Stwierdzono liczne pęknięcia w ziarnach kruszywa grubego kwarcytowego oraz w matrycy cementowej. W ziarnach kwarcytu zidentyfikowano znaczącą obecność kwarcu mikrokrystalicznego i kryptokrystalicznego. Jednoznacznie zidentyfikowano produkty reakcji alkalia-krzemionka o typowym składzie. Znaczne spękanie i zmniejszenie modułu sprężystości skorelowano z obecnością reaktywnego kwarcu w kruszywie kwarcytowym, uznając reakcję alkalia-krzemionka za główną przyczynę uszkodzeń. Przedyskutowano możliwą rolę dodatkowych czynników destrukcyjnych, takich jak wpływ ruchu pojazdów ciężkich oraz agresji mrozu.

5

Wpływ nietypowych rozwiązań konstrukcyjno-wykończeniowych panelowego dachu drewnianego na powstanie uszkodzeń ścian działowych poddasza

Berkowski Piotr, Dmochowski Grzegorz

Materiały Budowlane

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2022

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nr 11

145--147

PL

W artykule przedstawiono analizę stanu technicznego oraz przyczyny powstania uszkodzeń obudowy połaci dachowej, z płyt gipsowo-kartonowych o zwiększonej odporności na ogień (GKF), w budynku jednorodzinnym o drewnianej konstrukcji szkieletowej z dachem panelowym. Pokrycie dachu stanowiła blacha na macie dystansowej, z izolacją z wełny mineralnej pokrytej folią dachową i paroizolacją. W trakcie eksploatacji budynku zaczęły pojawiać się liczne spękania na styku obudowy połaci dachowej i ścian, osiągające rozwartość do 1,5 cm. Na podstawie przeprowadzonych analiz stwierdzono, że przyczyną powstania uszkodzeń były wahania wilgotności drewnianych elementów dachu, wynikające z braku właściwej wentylacji warstw połaci dachowej.

EN

The article presents an analysis of the technical condition and the causes of damages of the plasterboards (with increased fire resistance) casing of the roof in a single-family building with a wooden frame structure with panel roof. The roof was covered with a metal sheet on a spacer mat with mineral wool insulation, covered with a roof foil and a vapor barrier. During the operation of the building, numerous cracks began to appear at the junction of the roof covering and walls, reaching a width of up to 1.5 cm. Based on the conducted analyzes, it was found that the cause of the damage was fluctuations in the humidity of wooden roof elements, resulting from the lack of proper ventilation of the roof layers.

6

Naprawa i uszczelnianie rys oraz dylatacji przy przeciekach

Rokiel Maciej

Izolacje

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2022

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R. 27, nr 5

88, 89

PL

W artykule autor omawia problematykę naprawy i uszczelnień rys oraz dylatacji. Wskazuje na możliwe przyczyny powstawania uszkodzeń i przedstawia szereg skutecznych rozwiązań naprawczych.

EN

In the article, the author discusses the issues of repair and sealing of cracks and expansion joints. He indicates possible causes of damage and presents a number of effective repair solutions.

7

Reinforcement of cracked hollow-core slabs during the construction of the building

Szeląg Romuald

Inżynieria Bezpieczeństwa Obiektów Antropogenicznych

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2022

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Nr 4

54--62

EN

During the implementation of investment processes with the use of ready-made prefabricated elements, undesirable situations may occur that cause scratches, excessive deflections or damage. This is due to the fact that defects occur during transport, storage or incorrect loading of the elements. The conducted tests and technical assessments often allow the use of built-in elements, however, under the conditions of the need to make their reinforcements. This may be due to the scale of damage or defects made during molding and, as a consequence, the implementation of prefabricated elements with too low load capacity. Taking action each time should allow for the implementation of reinforcements of the elements, limiting the need to dismantle them, which would result in their irretrievable destruction. The implementation of reinforcements allows to reduce the generation of waste from new elements and allows for the proper management of already produced prefabricated elements. Used elements with reinforcements should be subject to technical inspection in the same periods as other structural elements. Proper implementation of repairs allows for the final effect to be similar to the parameters of elements free of technical defects. Due to the existing problem of damage to new elements of prefabricated channel ceilings, solutions have been developed that can be used to reinforce the elements without the need to dismantle them from the places of installation, while reducing the time spent on the process.

8

Overlying sand-inrushing mechanism and associated control technology for longwall mining in shallow buried coal seams with the soft surrounding rock

Wang Fangtian, Shao Dongliang, Zhang Cun, Zhang Chenkai, Song Ziyu

Archives of Mining Sciences

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2022

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Vol. 67, no. 4

681--697

EN

Taking the sand-inrushing accident of the Selian No. 1 coal mine in the Ordos of inner Mongolia as the research background, four main factors of sand-inrushing, including sand source, channel, sand-breaking power, and flowing space, were analysed. The disaster formation process (SCPS) illustrated that sand-inrushing disasters in shallowly buried coal seams with soft surrounding rock have the characteristics of being significantly influenced by mining, the development of vertical overburden channels, and sufficient space for water-sand mixed particles to flow. Universal Distinct Element Code (UDEC) software has been used to reveal that the vertical cracks in the overburden between the coal wall and support undergo a process of development and expansion along with the cumulative stress of mining. This showed that the vertical fissure through the overburden is the main pathway for the disaster. Combined with the site conditions, disaster occurrence mechanism, and numerical simulation results, a comprehensive prevention and control technology based on the working face and roadway grouting to block the channel was proposed. It contains reasonable mining height and optimisation of advancing speed, so that safe and efficient mining of coal seams in shallow-buried soft surrounding rocks could be achieved.

9

Assessment of the possibility of using the existing foundations for the construction of a steel silos

Plechawski Stanisław

Structure and Environment

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2021

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Vol. 13, no. 4

104--112

EN

The article presents an assessment of the possibility of using the existing reinforced concrete foundations as foundations for a new battery of steel silos for storing rape and soybean in the factory of fats. Visual tests of the reinforced concrete mantle were performed, as well as destructive and non-destructive tests of concrete strength, tests of the location of reinforcement, concrete carbonation and the degree of steel corrosion. On the basis of the conducted analyzes, final conclusions and recommendations concerning the conditions of further operation were formulated.

PL

W artykule przedstawiono ocenę możliwości wykorzystania istniejących fundamentów żelbetowych jako fundamentów pod nową baterię silosów stalowych do magazynowania rzepaku i soi w zakładach tłuszczowych. Wykonano badania wizualne płaszcza żelbetowego, niszczące i nieniszczące badania wytrzymałości betonu, badania lokalizacji zbrojenia, karbonatyzacji betonu i stopnia korozji stali. Na podstawie przeprowadzonych analiz sformułowano wnioski końcowe oraz zalecenia dotyczące warunków dalszej eksploatacji.

10

Ultimate compressive strength assessment of uncleaned and cleaned corroded plates with locked crack

Woloszyk Krzysztof, Garbatov Yordan

Polish Maritime Research

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2021

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nr 3

117--127

EN

The work presented here investigates the structural response of cleaned corroded plates, subjected to compressive load in the presence of a locked crack, where the change of mechanical properties as a result of corrosion development and the cleaning process is also accounted for. A Finite Element model for assessing the compressive strength, considering geometric and material nonlinearities, is developed, and the analysed plates are compared with the available experimental data. An experimental design plan is generated using the Design of Experiments techniques, which quantifies the influence of the governing variables and their interactions with respect to the plate’s ultimate compressive strength. With a limited number of observations, the most significant effects are identified. The corrosion degradation is revealed to be the most crucial effect leading to an effective strength reduction. It was found that, in the case of a corroded plate with a locked crack subjected to a compressive load, the most severe case is when the crack is transversely oriented. The strength reduction is slightly lower than when the corrosion degradation and the presence of a crack are considered to be a simple summation of these two effects but acting separately. The outcome of the analysis is the development of several empirical formulations that allow a fast estimation of the ultimate strength of a corroded plate, subjected to compressive load in the presence of a locked crack, accounting for different cleaning.

11

Sheave axles of mine shaft hoists – difficulties and limitations in assessing their technical condition during in-service tests

Straszak Sławomir, Wiktor Artur

Mining – Informatics, Automation and Electrical Engineering

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2021

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R. 59, nr 4

7--13

EN

The paper discusses the difficulties and limitations in the possibility of assessing the technical condition of sheave axles during in-service tests resulting from the lack of access to many areas of the outer surface of the axle due to built-in bearings and mounted sheaves, as well as from the complex shape of some types of axles. Examples of inservice axle failures are given and the causes are discussed. In addition, information on the legal basis for performing non-destructive testing of sheave axles in service, technical requirements for sheave axles, critical areas found in axles, theoretical basis for ultrasonic testing, and testing techniques including the latest phased array method is presented.

PL

W artykule omówiono trudności i ograniczenia w możliwości oceny stanu technicznego osi kół linowych podczas badań w eksploatacji wynikające z braku dostępu do wielu obszarów powierzchni zewnętrznej osi ze względu na zabudowane łożyska i osadzone koła linowe, jak i wynikające ze skomplikowanego kształtu niektórych typów osi. Podano przykłady eksploatacyjnych uszkodzeń osi i omówiono przyczyny ich powstawania. Dodatkowo przedstawiono informacje dotyczące podstaw prawnych wykonywania badań nieniszczących osi kół linowych w czasie eksploatacji; wymagań technicznych dla osi kół linowych; obszarów krytycznych występujących w osiach; teoretycznych podstaw badań ultradźwiękowych oraz technik prowadzenia badań wraz z najnowszą metodą phased array.

12

Osie kół linowych górniczych wyciągów szybowych – trudności i ograniczenia w ocenie stanu technicznego podczas badań eksploatacyjnych

Straszak Sławomir, Wiktor Artur

Mining – Informatics, Automation and Electrical Engineering

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2021

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R. 59, nr 4

14--20

PL

W artykule omówiono trudności i ograniczenia w możliwości oceny stanu technicznego osi kół linowych podczas badań w eksploatacji wynikające z braku dostępu do wielu obszarów powierzchni zewnętrznej osi ze względu na zabudowane łożyska i osadzone koła linowe, jak i wynikające ze skomplikowanego kształtu niektórych typów osi. Podano przykłady eksploatacyjnych uszkodzeń osi i omówiono przyczyny ich powstawania. Dodatkowo przedstawiono informacje dotyczące podstaw prawnych wykonywania badań nieniszczących osi kół linowych w czasie eksploatacji; wymagań technicznych dla osi kół linowych; obszarów krytycznych występujących w osiach; teoretycznych podstaw badań ultradźwiękowych oraz technik prowadzenia badań wraz z najnowszą metodą phased array.

EN

The paper discusses the difficulties and limitations in the possibility of assessing the technical condition of sheave axles during in-service tests resulting from the lack of access to many areas of the outer surface of the axle due to built-in bearings and mounted sheaves, as well as from the complex shape of some types of axles. Examples of inservice axle failures are given and the causes are discussed. In addition, information on the legal basis for performing non-destructive testing of sheave axles in service, technical requirements for sheave axles, critical areas found in axles, theoretical basis for ultrasonic testing, and testing techniques including the latest phased array method is presented.

13

Application of a geometrically nonlinear elastoplastic gradient-enhanced damage model with incremental potential to composite microstructures

Boussetta H., Dittmann J., Wulfinghoff S.

Archives of Mechanics

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2021

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Vol. 73, nr 5-6

499--540

EN

The prediction of inelastic processes like plastic deformations and cracks within the microstructure of modern man-made materials by realistic, yet simple and efficient continuum models remains a major task in material modelling. For this purpose, gradient-extended standard dissipative solids represent one of the most promising model classes, which is also formulated and applied in this work to investigate microscopic failure mechanisms in three exemplary three-dimensional composite microstructures. The model combines geometrically nonlinear isotropic elastoplasticity with an isotropic damage model with gradient-extension. For the numerical treatment, a variational constitutive update algorithm based on the exponential map is applied. The model is used to provide insight into the microscopic failure of a brittle woven composite material, a particle-reinforced plastic and a carbon fiber reinforced composite. The influence of different microstructural and material parameters on the overall failure behavior is characterized. Adaptive meshing is used to enable a refined numerical resolution of the cracked regions.

14

A new index for damage identification in beam structures based on modal parameters

Taghipour Reza, Nashta Mina Roodgar, Bozorgnasab Moshen, Mirgolbabaei Hessam

Archive of Mechanical Engineering

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2021

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LXVIII, nr 4

375--394

EN

The structural damages can lead to structural failure if they are not identified at early stages. Different methods for detecting and locating the damages in structures have been always appealing to designers in the field. Due to direct relation between the stiffness, natural frequency, and mode shapes in the structure, the modal parameters could be used for the purpose of detecting and locating the damages in structures. In the current study, a new damage indicator named “DLI” is proposed, using the mode shapes and their derivatives. A finite element model of a beam is used, and the numerical model is validated against experimental data. The proposed index is investigated for two beams with different support conditions and the results are compared with those of two well-known indices – MSEBI and CDF. To show the capability and accuracy of the proposed index, the damages with low severity at various locations of the structures containing the elements near the supports were investigated. The results under noisy conditions are investigated by considering 3% and 5% noise on modal data. The results show a high level of accuracy of the proposed index for identifying the location of the damaged elements in beams.

15

Analysis of ultimate compressive strength of cracked plates with the use of doe techniques

Woloszyk Krzysztof, Garbatov Yordan

Polish Maritime Research

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2020

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nr 3

109--120

EN

The objective of this work is to investigate the structural compressive response of plates with locked cracks accounting for all relevant factors and correlation between them. The nonlinear FE model considering both geometric and material nonlinearities is employed herein, and the FE model of the structural response of intact plates is validated with the available experimental data. In the common studies, based on One Factor at a Time analysis, some of the parameters and interactions between them are excluded. In the present study, the numerical investigations are conducted with the use of the Design of Experiments techniques, where all essential parameters and their interactions are adequately considered. With a total of 32 numerical analyses, the most influential factors and their interactions are identified. As a study outcome, empirical formulations, which allow for a fast estimation of the ultimate compressive strength of intact plates, plates with locked cracks, and repaired cracked plates, are derived. The developed formulations represent a fast and practical tool for estimating the ultimate compressive strength of intact, cracked, and repaired plates, which can be easily employed in the reliability analysis.results followed by their discussion.

16

The mechanism of fractured porosity formation in heterogeneous rocks under irreversible volume-stress deformation

Bondar Halyna, Yevdoschuk Mykola

Nafta-Gaz

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2020

|

R. 76, nr 5

287--290

EN

The paper deals with the study of the deformation, strength, and reservoir properties of rocks under various stress conditions, typical of great depths. The effect of all-round compression causes a change in the elastic, plastic, and strength characteristics of rocks. Some features of fracture formation and development in inhomogeneous solids under tension and compression were determined. The irreversible deformation mechanism of rocks under an uneven volume stress was considered. The irreversible deformation of rocks combines two types of deformation–intergranular slip, which produces the development of micro-fracturing, and intracrystalline slip, which mainly develops only at high pressure. The typical types of rock damage for uneven triaxial compression (transcrystalline and intercrystalline damage) were investigated. The phenomenon of loosening and increasing the volume as a result of irreversible deformations is mainly caused by the simultaneous formation of intergranular micro-cracks and micro-shifts along grain boundaries. As a result of these micro-dislocation combinations, macroscopic shift planes are formed, followed by irreversible deformation. On the surfaces of deformed samples, slip lines often appear; these are the traces of these macroscopic shift planes. Rock samples deformed due to high pressure are presented. The slip plane traces are clearly visible on the samples’ surfaces. It has been stated that under conditions typical of 8–10 km depths, irreversible deformation occurs with decompaction of their structure, increasing the coefficients of porosity and permeability. The effect of rocks deconsolidation caused by stress can be so significant, that in some cases may even increase the volume of voids by 1.5–2 times. The processes of dissolution and leaching of chemically unstable elements are of great importance in determining the filtration capacity and reservoir properties of deep-lying rocks, affected by irreversible deformation changes. Different dependences of volume growth, decompaction intensity coefficient, and permeability coefficient on the overall compression under uneven triaxial stress–which was based on the data of sandstone and marble–have been illustrated. The volume growth is quantitatively determined with the help of the decompaction intensity coefficient, and it is correlated with the collector and filtration capacity of rocks.

PL

Artykuł dotyczy badań odkształcenia, wytrzymałości oraz właściwości zbiornikowych skał w różnych warunkach naprężenia typowych dla znacznych głębokości. Wpływ ściskania obwodowego powoduje zmianę właściwości sprężystych, plastycznych i wytrzymałościowych skał. Określono niektóre cechy tworzenia i rozwoju pęknięć w niejednorodnych ciałach stałych pod wpływem rozciągania i ściskania. Rozważano mechanizm nieodwracalnego odkształcenia skał pod wpływem niejednolitego naprężenia objętościowego. Nieodwracalne odkształcenie skał łączy dwa rodzaje odkształcenia: poślizg międzyziarnowy, powodujący rozwój mikropękania, oraz poślizg międzykrystaliczny, który rozwija się tylko przy wysokim ciśnieniu. Badano rodzaje zniszczenia skał typowe dla niejednolitego trójosiowego ściskania (zniszczenie śródkrystaliczne i międzykrystaliczne). Zjawisko rozluźniania i zwiększenia objętości w wyniku odkształceń nieodwracalnych jest powodowane przez jednoczesne tworzenie mikropęknięć międzyziarnowych oraz mikroprzesunięcia wzdłuż granic ziaren. W wyniku tych kombinacji mikrodyslokacji tworzone są makroskopowe płaszczyzny przemieszczenia, a następnie odkształcenie nieodwracalne. Na powierzchni próbek odkształconych często pojawiają się linie poślizgu, które są śladami tych makroskopowych płaszczyzn poślizgu. Zaprezentowano próbki skalne odkształcone z powodu wysokiego ciśnienia. Na powierzchni próbek widoczne są wyraźnie ślady płaszczyzn poślizgu. Stwierdzono, że w warunkach typowych dla głębokości 8–10 km występuje odkształcenie nieodwracalne z rozgęszczeniem ich struktury, zwiększeniem współczynników porowatości i przepuszczalności. Wpływ dekonsolidacji skał powodowany przez naprężenie może być tak istotny, że całkowicie usuwa konsolidację skał, powodowaną przez naprężenia efektywne, a w niektórych przypadkach może zwiększyć objętość pustek nawet 1,5–2 razy. Procesy rozpuszczania i ługowania elementów niestabilnych chemicznie mają duże znaczenie dla określenia zdolności filtracji oraz właściwości zbiornikowych skał zalegających głęboko pod wpływem nieodwracalnych zmian odkształcenia. Zilustrowano różne zależności wzrostu objętości, współczynnika intensywności dekompakcji i współczynnika przepuszczalności od całkowitego ściskania pod wpływem niejednolitego naprężenia trójosiowego, oparte na danych dla piaskowca i marmuru. Wzrost objętości jest ilościowo określony za pomocą współczynnika intensywności dekompakcji i jest skorelowany z właściwościami filtracyjnymi skał.

17

Effect of calcium sulfoaluminate additive on linear deformation at different humidity and strength of cement mortars

Abdulwahid Al-Musawi Kadhim, Bindhu Abraham Kottayil, Potses Tatsiana, Leonovich Sergey, Kalinouskaya Natallia, Beulah M., Budrevich Neli

Inżynieria Bezpieczeństwa Obiektów Antropogenicznych

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2020

|

Nr 2

1--9

EN

The effect of calcium sulfoaluminate additives (CSA) on the compression and bending strength of mortar, as well as linear deformation of prism samples at different environmental humidity was studied. Test results indicate that bending strength of mortars with CSA and the referent at the age of 28 days are practically equal. Compressive strength of mortars with CSA reduced by 20 ... 23% for all dosages of CSA. Relative linear deformations depend on the humidity of the environment. At a humidity of 100%, the relative linear deformations are positive and the expansion increases with increasing dosage of the expanding additive. When hardening in dry air at a humidity of 55%, the greatest shrinkage deformations were for mortars with CSA. We can conclude that the expanding effect of CSA is fully manifested at high humidity, i.e. under construction conditions, this means very high-quality moisture care for concrete structures.

18

The failure analysis of the drilling rig hoisting steel wire rope

Peterka Pavel, Krešák Jozef, Vojtko Marek, Halek Branislav, Heinz David

Eksploatacja i Niezawodność

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2020

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Vol. 22, no. 4

667--675

EN

Drilling rigs belong to the lowest-safety level of hoisting rope systems. The valid regulation for drilling permits the usage of steel ropes on condition that their permanent safety does not decrease under the value 2.5. Considerable dynamic and cyclic stresses, abrasion and corrosive environment generated during the operation cause rapid fatigue and rope damage. The stress of the rope in operation leads to the specific precautions ensuring the safety rope work. The specific precautions include monitoring of the rope tractive work measured in tonne-kilometres (ton-kilometres services). The working part of the hoisting ropes of the drilling rigs - after the stated number of tonne kilometres was worked off - is slipped and a regular non-destructive rope test (NDT) is recommended. Rope under sizing, failing in rope slipping program and non- implementation of NDT controls led to the situations endangering the drilling crew safety. After the critical situations the operator decided to perform the analysis of the condition of all ropes.

19

Niekonwencjonalna metoda wykrywania pęknięć

Gardyński Leszek

Dozór Techniczny

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2020

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z. 4

12--15

PL

W artykule opisano wyniki badań doświadczalnych istnienia potencjalnych pęknięć w grubościennych profilach wykonanych metodami obróbki plastycznej. Inspiracją do napisania artykułu były badania zlecone autorowi, mające na celu potwierdzenie istnienia pęknięć powstałych na łukach, przy zginaniu blach tworzących profile ramion maszyn budowlanych. Istnienia tych pęknięć ostatecznie nie potwierdzono. Głównym wnioskiem jest to, że w niektórych przypadkach, kiedy podejrzewamy istnienie uszkodzeń, warto jest w czasie badań spotęgować ich przyczynę, aby ostatecznie wykluczyć ich istnienie.

20

Analysis of deflection and cracking of concrete beams with non-metallic reinforcement

Kosior-Kazberuk Marta, Krassowska Julita

System Safety : Human - Technical Facility - Environment

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2019

|

Vol. 1, nr 1

782--789

EN

The composite bars have become a useful substitute for conventional reinforcement in civil engineering structures for which load capacity and resistance to influences of environmental factors' are required. Considering the requirements of responsible design of engineering structures with particular emphasis on durability, the use of non-metallic reinforcement in reinforced structural elements allows to reduce the costs related to erection of buildings, as well as the costs of building maintenance and renovations. The behaviour of model beams made of concrete reinforced with composite bars (fiber reinforced polymer bars) in three-point bending test was analyzed. The strength parameters of composite bars were tested. The bending capacity, deformation of concrete, and beam deflection were determined. Crack propagation in the model beams under load was analyzed using the Aramis 5M optical measuring system. Due to the strength characteristics of the composite reinforcing bars, the beams exhibited significant tensile strains, which resulted in the development of cracks of considerable width.