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Tytuł:
Lengthwise crack study of a beam with non-linear creep
Autorzy:
Rizov, Victor Iliev
Powiązania:
https://bibliotekanauki.pl/articles/38890066.pdf
Data publikacji:
2024
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
beam structure
non-linear creep
lengthwise crack
Opis:
An analytical study of the strain energy release rate for an inhomogeneous beam structure with a lengthwise crack subjected to non-linear creep is developed. The beam is inhomogeneous along its length. Two cases are analysed (material with identical creep behaviour in tension and compression, and material with asymmetrical creep behaviour). Since the stress cannot be determined explicitly from the non-linear stress-strain-time relationship, an approach for obtaining of time-dependent solutions of the strain energy release rate is developed by expressing the z-coordinate as a function of the stress. The analysis indicates that the asymmetrical creep behaviour leads to an increase in the strain energy release rate.
Źródło:
Engineering Transactions; 2024, 72, 1; 15-38
0867-888X
Pojawia się w:
Engineering Transactions
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of Rheological Properties of Cement Composites Based on Waste Materials
Autorzy:
Zakrzewski, Mateusz
Domski, Jacek
Powiązania:
https://bibliotekanauki.pl/articles/27322945.pdf
Data publikacji:
2023
Wydawca:
Politechnika Koszalińska. Wydawnictwo Uczelniane
Tematy:
cement composites
creep
steel cord
fiber-reinforcement concrete
long-term study
concrete beams
waste aggregate
waste fibers
crack
Opis:
This report presents the results and analysis of long-term properties of fiber-reinforced cement composite based on waste aggregate. The long-term tests were carried out on the stand proposed by the authors for simultaneously testing three beams with dimensions of 100x200x2900 mm. A total of 8 mixtures of cement composites with aggregate from ceramic waste and waste sand were tested. Three beams were made for each mixture. One without dispersed reinforcement and two with 0.5% and 1.0% fiber reinforcement ratios. As dispersed reinforcement, steel cord and hooked steel fibers were used. The beams were subjected to a four-point bending test. The research was carried out for 1000 days. An optical system was used as an innovative solution in long-term research. Based on the measurements, the creep coefficient in the mid-span of the beams was determined, and the crackings of the beams were analysed. The results obtained using manual measuring devices and the optical system were compared. A good convergence of measurement methods was observed. During the analysis of the results, the coefficients modifying the method for calculating the crack width included in Eurocode 2 were determined.
Źródło:
Rocznik Ochrona Środowiska; 2023, 25; 159--173
1506-218X
Pojawia się w:
Rocznik Ochrona Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental study of the nonlinear behaviour of deep-sea mooring polyester fibre ropes
Autorzy:
Zhang, He
Zeng, Ji
Jin, Bowen
Chou, Chiate
Li, Hangyu
Dong, Hailei
Powiązania:
https://bibliotekanauki.pl/articles/34611198.pdf
Data publikacji:
2023
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
polyester fibre ropes
static stiffness
creep coefficient
long-term cyclic loads
dynamic stiffness
Opis:
Mooring ropes are essential components of ships and offshore floating structures and they are subjected to cyclic axial loads. This study investigates the evolution of the full-cycle stiffness of fibre polyester ropes under long-term static and dynamic loading. First, the static stiffness characteristics of the ropes, including the rope elongation properties at different stages, shrinkage rates, and creep coefficients after an idle period, are examined under static loads; an empirical formula for static stiffness is established. Second, the dynamic stiffness characteristics of the ropes are investigated under cyclic loads that are typical of platform production operations. The stabilities of the structure under different tensions are compared; the effects of mean tension, tension amplitude, and load cycle on the dynamic stiffness of the ropes are analysed and an empirical formula is established to predict the dynamic stiffness during the engineering design phase. The results of this study can be helpful for the rational design of deep-sea taut-leg mooring systems because they present the evolution of the full-cycle stiffness characteristics of mooring ropes.
Źródło:
Polish Maritime Research; 2023, 3; 153-162
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on creep-fatigue model of anchored jointed rock mass
Autorzy:
Song, Yang
Fan, Bo
Li, Yong-Qi
Wang, He-Ping
Powiązania:
https://bibliotekanauki.pl/articles/2200878.pdf
Data publikacji:
2023
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
shear creep
anchored jointed rock mass
fractional order
fatigue load
damage
Opis:
To explore the mechanical response of anchored rock mass with an interaction of fatigue and creep, this paper selects the fatigue amplitude and fatigue frequency as influencing factors to carry out a fatigue-creep experiment of the anchored rock mass. Based on fractional order theory and binary perturbation theory, a new fractional order creep model is constructed. The results show that compared with the Burgers model, the newly proposed creep model can better describe the whole process of creep deformation of the anchored jointed rock mass under fatigue loading.
Źródło:
Journal of Theoretical and Applied Mechanics; 2023, 61, 1; 163--173
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Aktualizacja modelu teoretycznego Mostu Rędzińskiego na podstawie pomiarów konstrukcji, po 10 latach eksploatacji
An updating of the model of the Rędziński bridge based on the structural monitoring, after 10 years of operation
Autorzy:
Żółtowski, Krzysztof
Binczyk, Mikołaj
Kalitowski, Przemysław
Powiązania:
https://bibliotekanauki.pl/articles/2142039.pdf
Data publikacji:
2022
Wydawca:
Polski Związek Inżynierów i Techników Budownictwa
Tematy:
most podwieszony
Most Rędziński
model numeryczny
kalibracja modelu
pełzanie
metoda elementów skończonych
MES
cable-stayed bridge
Rędziński bridge
numerical model
model updating
creep
finite element method
FEM
Opis:
W roku 2020 zrealizowano prace badawcze, które miały na celu ocenę stanu konstrukcji Mostu Rędzińskiego we Wrocławiu po 10 latach eksploatacji. W ramach badań eksperckich wykonano pomiary sił w wantach mostu metodą wibracyjną, dokonano pomiarów geodezyjnych przęseł i pylonu oraz zbudowano model numeryczny. Model posłużył do oceny aktualnego stanu wytężenia elementów konstrukcji. Konieczne było przeprowadzenie aktualizacji pierwotnego modelu teoretycznego z uwagi na szereg istotnych zmian, które z upływem czasu zachodzą w konstrukcji, a które trudno precyzyjnie oszacować w trakcie projektowania. Zmiany te są efektem pełzania betonu, relaksacji stali i osiadania fundamentów. W artykule przedstawiono proces aktualizacji modelu teoretycznego mostu podwieszonego na podstawie wyników pomiarów. Uwzględniono w niej wpływ technologii budowy, pierwotny naciąg want, efekty reologiczne oraz osiadania podpór. Ostatecznie uzyskano model, w którym siły w wantach oraz trwałe deformacje przęseł i pylonu są zgodne z wartościami pomierzonymi. Potwierdzono, że w modelowaniu konstrukcji podwieszonej bardzo istotne jest precyzyjne określenie ciężaru własnego przęseł oraz sił naciągu w wantach. Niewielkie błędy w ich przyjęciu mogą skutkować dużymi błędami w wyznaczonej geometrii obiektu i siłach wewnętrznych.
In 2020, research was performed to assess the condition of the structure of the Rędziński Bridge in Wrocław after 10 years of operation. As a part of expert research, the forces in the bridge cables were measured using the vibration method, geodetic measurements of the spans and the pylons were made, and a numerical model was created. The model was used to assess the current condition of the structural elements. It was necessary to update the original theoretical model due to a number of significant changes that occur over time in the structure, and which were difficult to precisely estimate during the design. These changes are the results of concrete creep, steel relaxation and foundation subsidence. The paper presents the process of updating the theoretical model of a cable-stayed bridge on the basis of measurement results. It takes into account the influence of construction technology, the primary tension of the cables, rheological effects and subsidence of supports. Finally, a model was obtained in which the forces in the cables and the deformation of the spans and the pylon are consistent with the measured values. It was confirmed that in modelling a cable-stayed bridge, it is very important to precisely determine the dead weight of the spans and the tension forces in the cables. Small errors in their estimation may result in large errors in the determined geometry of the structure and internal forces.
Źródło:
Przegląd Budowlany; 2022, 93, 5-6; 76--81
0033-2038
Pojawia się w:
Przegląd Budowlany
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dendrochronological record of soil creep and landslide activity – the comparison of tree-ring eccentricity and compression wood (examples from the Kamienne Mts., Poland)
Autorzy:
Sitko, Katarzyna
Wistuba, Małgorzata
Malik, Ireneusz
Krąpiec, Marek
Yu, Ruide
Zhang, Haiyan
Powiązania:
https://bibliotekanauki.pl/articles/2124701.pdf
Data publikacji:
2022
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
dendrochronology
landslide
soil creep
compression wood
tree-ring eccentricity
Opis:
Forested mountain slopes can be simultaneously affected by soil creep and landslide activity, both of which cause the tilting of tree stems, with the result that their dendrochronological record of tree-ring eccentricity and compression wood is potentially similar. There is a need to identify similarities and differences in these records and thus our research aimed to compare patterns of eccentricity and compression wood developed by trees under the impact of soil creep and landslides. We sampled trees growing on a landslide and creeping slopes in the Kamienne Mts., with 21 Norway spruce trees were sampled on each site. We found several main differences between the dendrochronological record of landslide activity and soil creep. On the landslide we found larger number of dendrochronological events, stronger and more variable eccentricity and a similar number of upslope and downslope events. On creeping slopes, upslope eccentricity events predominate, and the number of eccentricity events dated in all trees increases in time. We also compared the utility of eccentricity and compression wood for dating mass movements. They differ in their sensitivity to stem tilting. Thus, in analyses of landslide activity and soil creep activity, it is recommended to include both wood anatomy features.
Źródło:
Geology, Geophysics and Environment; 2022, 48, 2; 133--146
2299-8004
2353-0790
Pojawia się w:
Geology, Geophysics and Environment
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Drying shrinkage and creep properties of self-compacting concrete with expansive agent and viscosity modified admixture
Autorzy:
Liu, He
Duan, Guangchao
Zhang, Jingyi
Powiązania:
https://bibliotekanauki.pl/articles/2174047.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
beton samozagęszczalny
środek ekspansywny
UEA
domieszka o zmodyfikowanej lepkości
pełzanie
skurcz suszenia
self-compacting concrete
expansive agent
viscosity modified admixture
creep
drying shrinkage
Opis:
Self-Compacting Concrete (SCC) has been widely used in the filling layer of high-speed railways. The quality of the filling layer directly affects the durability, comfort, and safety of the track system. In this study, shrinkage characteristics and the creep behavior of SCC were investigated by compressive creep tests and shrinkage tests. They were performed on specimens with different loading levels with a calcium sulfoaluminate-based expansive agent (UEA) and viscosity modified admixture (VMA). Furthermore, based on the scanning electron microscope (SEM) morphology of hydration products and X-ray diffraction (XRD) analysis, the influence of admixtures on microstructure and mineral phases of SCC was analyzed.The results show that when concretes were loaded with the same stress level, the main factor influencing creep of SCC was the quantity and microstructure of amorphism and hydration crystal. The XRD and SEM result showed that UEA andVMAmake the creep and shrinkage of SCC reduce obviously as the cementitious system grow many crystals in hydration products. The creep of NC was less than SCC with identical compressive strength. At the same time, the addition of UEA can improve the ability to resist drying shrinkage.
Źródło:
Archives of Civil Engineering; 2022, 68, 3; 539--551
1230-2945
Pojawia się w:
Archives of Civil Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Time History on Long-Term Deformation of Gypseous Soils
Autorzy:
Fattah, Mohammed Y.
Al-Shakarchi, Yousif J.
Al-Numani, Huda N.
Powiązania:
https://bibliotekanauki.pl/articles/2172881.pdf
Data publikacji:
2022
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
gypseous soil
creep
collapse
time history
relative density
Opis:
The time-dependent behavior of three gypseous soils was investigated. The soils had gypsum content of 66%, 44%, and 14.8%. The mineralogical and chemical properties of the soils were determined. Two series of tests were performed. In the first, collapsibility characteristics were investigated for a long period (60 days) by conducting single and double oedometer tests. In the second series, the effect of relative density on collapse with time was investigated. The samples were compacted to 40%, 50%, and 60% relative density and then tested. The results of collapse tests showed that the relationship between the strain and logarithm of effective stress has two vertical lines. The first one represents the collapse settlement taking place within 24 h, while the second one represents the long-term collapse. The collapse potential (CP) in both single and double oedometer tests increases when the gypsum content increases from 14.8% to 66% and when the initial void ratio increases. The CP–logarithm of time relationship for soaked samples prepared at different relative densities under 800 kPa indicated that the CP increased with time for the soil sample compacted at 60% relative density and the increase was higher than those compacted at 40% and 50% relative density. The curves started with a straight line and then a concave downward curve was observed with a high strain. For samples compacted at 40% and 50% relative densities, the curves were interrupted by little soil collapses, while the third curve exhibited smooth relation following the collapse.
Źródło:
Studia Geotechnica et Mechanica; 2022, 44, 3; 198--210
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fracture analysis for viscoelastic creep using peridynamic formulation
Autorzy:
Azizi, Muhammad Azim
Mohd Zahari, Mohd Zakiyuddin
Abdul Rahim, Sharafiz
Azman, Muhamad Amin
Powiązania:
https://bibliotekanauki.pl/articles/2200832.pdf
Data publikacji:
2022
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
viscoelastic
peridynamic
creep behavior
fracture mechanic
Opis:
The purpose of this paper is to provide a peridynamic (PD) model for the prediction of the viscoelastic creep deformation and failure model. The viscoelastic characteristic consists of several stages, namely primary creep, secondary creep, tertiary creep and fracture. A non- linear viscoelastic creep equation based on the internal state variable (ISV) theory covering four creep stages and PD equations are used. The viscoelastic equation is inserted into the PD equation to derive a PD model with two time parameters, i.e., numerical time and vis- coelastic real time. The parameters of the viscoelastic equation are analyzed and optimized. A comparison between numerical and experimental data is performed to validate this PD model. The new PD model for nonlinear viscoelastic creep behavior is confirmed by an ac- ceptable similarity between the numerical and experimental creep strain curves with an error of 15.85%. The nonlinearity of the experimental and numerical data is sufficiently similar as the error between the experimental and numerical curves of the secondary stage strain rate against the load is 21.83%. The factors for the errors are discussed and the variation of the constants in the nonlinear viscoelastic model is also investigated.
Źródło:
Journal of Theoretical and Applied Mechanics; 2022, 60, 4; 579--591
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Bending Creep Behaviour of a Powder Metallurgy FeMnSiCrNi Shape Memory Alloy
Autorzy:
Ciurcă, Lenuța
Pricop, Bogdan
Agop, Maricel
Bujoreanu, Leandru-Gheorghe
Powiązania:
https://bibliotekanauki.pl/articles/2125532.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
FeMnSiCrNi shape memory alloy
bending creep
creep rate
multifractal model
Opis:
FeMnSiCrNi alloys represent a promising class of FeMnSi-based shape memory alloys (SMAs) characterized by excellent characteristics of formability and corrosion resistance. The present paper is focused on a 68Fe-18Mn-3Si-7Cr-4Ni (mass. %) SMA, produced by powder metallurgy routine, which was tested to creep, using a dual cantilever specimen holder, and analyzed by means of the dedicated software of a dynamic mechanical analyzer. The specimens were tested at five temperatures by applying, at each of them, four bending force values, during 2000 s. The variation of bending creep deflection with time, temperature and force was discussed both from the point of instant value and 1000 s-value. These results enabled plotting a space diagram of stabilized creep rate variation with both applied force and test temperature. In such context, a theoretical model in a multifractal paradigm of motion was built, considering that FeMnSiCrNi shape memory alloy can be assimilated, both structurally and functionally, with a multifractal object. Finally, this model was validated by means of experimental data.
Źródło:
Archives of Metallurgy and Materials; 2022, 67, 3; 901--908
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on the shear creep characteristics of anchored jointed rock masses under creep fatigue loading
Autorzy:
Song, Yang
Li, Yong-Qi
Powiązania:
https://bibliotekanauki.pl/articles/2200837.pdf
Data publikacji:
2022
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
disturbed load
sandstone
marble
creep body
rheological model
Opis:
To study creep characteristics of deep rock masses under low-frequency earthquakes and other loads, sandstone and marble samples were used to characterize soft rock and hard rock, respectively. Shear creep tests of anchored rock masses under fatigue loading were carried out by using the graded loading method. A new nonlinear rheological model was constructed to characterize mechanical properties of anchored rock masses under fatigue loading. Creep fatigue curves of soft rock and hard rock have clear creep characteristics including instantaneous, attenuation, steady-state and accelerated creep stages. This work provides new insights into the stability of rock masses.
Źródło:
Journal of Theoretical and Applied Mechanics; 2022, 60, 4; 625--635
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Właściwości reologiczne betonu lekkiego na kruszywie spiekanym
Rheological properties of lightweight concrete on sintered aggregate
Autorzy:
Lewiński, Paweł
Fedorczyk, Zbigniew
Zacharski, Łukasz
Rogowska, Anna
Powiązania:
https://bibliotekanauki.pl/articles/2142041.pdf
Data publikacji:
2022
Wydawca:
Polski Związek Inżynierów i Techników Budownictwa
Tematy:
beton lekki
beton z kruszywem spiekanym
właściwości reologiczne
pełzanie
skurcz
badanie laboratoryjne
badanie wytrzymałościowe
lightweight concrete
sintered aggregate concrete
sintered fly ash aggregate
rheological properties
creep
shrinkage
laboratory test
strength test
Opis:
Zastosowanie betonu lekkiego na kruszywie spiekanym do sprężonych konstrukcji obiektów budowlanych było przedmiotem najnowszych prac wielu autorów. Wykorzystując specjalny beton lekki na kruszywie spiekanym, jako materiał gwarantujący obniżenie ciężaru własnego konstrukcji, przy zachowaniu wymaganych właściwości wytrzymałościowych betonu uzyskuje się - jak się okazuje - w elementach konstrukcji sprężonych dodatkową rezerwę w zakresie nośności i ugięć. Niezbędnym warunkiem tych nowych zastosowań jest wiarygodne przebadanie właściwości reologiczne rozpatrywanego betonu. W tym celu w Laboratorium Konstrukcji Budowlanych, Geotechniki i Betonu ITB, niezależnie od przeprowadzonych badań doraźnych właściwości wytrzymałościowych omawianego betonu lekkiego, prowadzone są prace mające na celu wyznaczenie właściwości reologicznych w zakresie długotrwałego skurczu i pełzania.
The application of lightweight concrete on sintered aggregate for prestressed concrete structures has been the subject of recent works by many authors. By using a special lightweight concrete on sintered aggregate as a material that guarantees the reduction of the dead weight of the structure, while maintaining the required strength properties of concrete, it turns out that additional reserve capacity and deflection are obtained in the elements of prestressed structures. Reliable testing of the rheological properties of the considered concrete is a necessary condition for these new applications. For this purpose, in the Laboratory of Building Structures, Geotechnics and Concrete ITB, regardless of the conducted tests of short-term strength properties of the considered lightweight concrete, the tests are carried out to determine the rheological properties of long-term shrinkage and creep.
Źródło:
Przegląd Budowlany; 2022, 93, 5-6; 70--75
0033-2038
Pojawia się w:
Przegląd Budowlany
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A roadway in close distance to coal seam in deep mine: location selection and supporting practice based on creep characteristics of surrounding rocks
Autorzy:
Wang, Xufeng
Wang, Jiyao
Chen, Xuyang
Chang, Zechao
Powiązania:
https://bibliotekanauki.pl/articles/2073870.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
kopalnia głębinowa
pokłady węgla
pełzanie
deep mine
close distance
coal seam group
location of roadway
creep
Opis:
In deep mines, since the broken surrounding rocks & high-stress level of a roadway being near a coal seam, the creep characteristics of surrounding rocks should be considered as the main influencing factor in the selection for the roadway’s location of the lower coal seam. Both VI15 and VI16-17 coal seams of the Pingdingshan No. 4 Coal Mine, in China, Henan province, are close coal seams with a depth of around 900 m. According to the traditional formula calculation results, when the lower coal seam roadway is staggered 10 m to the upper coal seam goaf, the roadway pressure behaviour is significant, and the support becomes difficult. In this paper, the properties of surrounding rock were tested and the influence of lower coal seam on the stress state of surrounding rock is analysed by numerical simulation, and systematic analysis on the stress and creep characteristics of the surrounding rock of the mining roadway and its effects on the deformation is performed. The results demonstrated that the roadway’s locations in the lower coal seam can be initially divided into three zones: the zone with accelerated creep, the transition creep zone and the insignificant creep zone. The authors believed that the roadway layout in an insignificant creep zone can achieve a better supporting effect. Based on the geological conditions of the roadway 23070 of the VI16-17 coal seam of the Pingdingshan No. 4 Coal Mine, combined with the above analysis, a reasonable location of roadway (internal offset of 30 m) was determined using numerical simulation method. The reliability of the research results is verified by field measurement. The above results can provide a reference for selecting the roadway’s location under similar conditions.
Źródło:
Archives of Mining Sciences; 2021, 66, 3; 407--419
0860-7001
Pojawia się w:
Archives of Mining Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Concept of advanced lifetime monitoring system for steam turbines
Koncepcja zaawansowanego systemu monitorowania żywotności turbin parowych
Autorzy:
Banaszkiewicz, Mariusz
Powiązania:
https://bibliotekanauki.pl/articles/1840894.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN
Tematy:
monitoring
steam turbines
lifetime assessment
low-cycle fatigue
creep
monitorowanie
turbina parowa
ocena żywotności
zmęczenie małocyklowe
pełzanie
Opis:
The increasing share of renewables in electricity production adversly affects the operation of thermal plants, including steam turbine units. Intermittency of renewable sources results in high variability of steam turbine operating conditions, which together with the inherent scatter of turbine operating parameters significantly complicates their lifetime assessment. The paper presents a concept of lifetime monitoring system in scope of creep-fatigue damage. The system is based on online and offline calculations, performs online analysis of measurement data and takes into account the results of material tests. Functionality of the system main modules is described and mathematical models suitable for online calculations are presented. A general concept of hardware configuration for the system is proposed as well.
Wzrastający udział odnawialnych źródeł energii w produkcji prądu ma niekorzystny wpływ na pracę elektrowni cieplnych, w tym bloków parowych. Niestabilność źródeł odnawialnych skutkuje dużą zmiennością warunków pracy turbin parowych, co w połączeniu z nieodłącznym rozrzutem parametrów pracy turbin w znaczący sposób komplikuje ocenę ich żywotności. W artykule przedstawiono koncepcję systemu monitorowania żywotności w zakresie zużycia zmęczeniowo-pełzaniowego. System ten oparty jest na obliczeniach w trybie online i offline, wykonuje na bieżąco analizę danych pomiarowych oraz uwzględnia wyniki badań materiałowych. Omówione zostały funkcje głównych modułów systemu wraz z propozycją modeli matematycznych odpowiednich do obliczeń w trybie online. Zaproponowano również ogólną koncepcję konfiguracji sprzętowej systemu.
Źródło:
Diagnostyka; 2021, 22, 1; 23-29
1641-6414
2449-5220
Pojawia się w:
Diagnostyka
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Creep Behaviors at 275 °C for Aluminum-Matrix Nano-composite under Different Stress Levels
Autorzy:
Azadi, M.
Behmanesh, A.
Aroo, H.
Powiązania:
https://bibliotekanauki.pl/articles/2079834.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
aluminum alloy
nanocomposite
nanoparticles
regression model
creep
stress
stop aluminium
nanokompozyt
nanocząstki
model regresji
pełzanie
naprężenia
Opis:
Aluminum alloys, due to appropriate strength to weight ratio, are widely used in various industries, including automotive engines. This type of structures, due to high-temperature operations, are affected by the creep phenomenon; thus, the limited lifetime is expected for them. Therefore, in designing these types of parts, it is necessary to have sufficient information about the creep behavior and the material strength. One way to improve the properties is to add nanoparticles and fabricate a metal-based nano-composite. In the present research, failure mechanisms and creep properties of piston aluminum alloys were experimentally studied. In experiments, working conditions of combustion engine pistons were simulated. The material was composed of the aluminum matrix, which was reinforced by silicon oxide nanoparticles. The stir-casting method was used to produce the nano-composite by aluminum alloys and 1 wt.% of nanoparticles. The extraordinary model included the relationships between the stress and the temperature on the strain rate and the creep lifetime, as well as various theories such as the regression model. For this purpose, the creep test was performed on the standard sample at different stress levels and a specific temperature of 275 o. By plotting strain-time and strain rate-time curves, it was found that the creep lifetime decreased by increasing stress levels from 75 MPa to 125 MPa. Moreover, by comparing the creep test results of nanoparticle-reinforced alloys and nanoparticle-free alloys, 40% fall was observed in the reinforced material lifetime under 75 MPa. An increase in the strain rate was also seen under the mentioned stress. It is noteworthy that under 125 MPa, the creep lifetime and the strain rate of the reinforced alloy increased and decreased, respectively, compared to the piston alloy. Finally, by analyzing output data by the Minitab software, the sensitivity of the results to input parameters was investigated.
Źródło:
Archives of Foundry Engineering; 2021, 21, 3; 81-89
1897-3310
2299-2944
Pojawia się w:
Archives of Foundry Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 164

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