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1

A pre-protection method for a pipe-jacking channel over shield tunnels

Cui Yunliang, Yang Xukun, Wang Xinquan, Diao Hongguo, Li Xiao, Gao Yuanyuan

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2024

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Vol. 72, nr 2

art. no. e148443

EN

With the improvement of the planning level of underground space, the location of the planned under-crossing tunnel can be known in advance when constructing the upper-span tunnel. Therefore, pre-protection measures can be taken in advance during the construction of the upper-span tunnel. A new pre-protection method of a pipe-jacking channel was proposed to reduce the adverse effects of under-crossing shield tunnels. Numerical simulations of different pre-protection schemes were carried out using the finite element method to analyze its deformation control effect. The simulation results show that the deformation control effect of the gantry reinforcement scheme is the most significant. It is shown that the displacement of the pipe-jacking channel is more significantly suppressed with pre-protection measures than without preventive protection measures. The vertical displacement curve of the pipe-jacking channel exhibits a “W” shape after the construction of the double-lane shield underpass. By comparing the three different working conditions, it is found that the maximum vertical displacement and surface settlement of the pipe-jacking channel greatly reduced the gantry reinforcement pre-protection. Compared with Case 3, the effect of the pre-protection measures adopted in Case 2 was less obvious, which indicated that the form of the pre-protection had an important influence on controlling the deformation of the pipe-jacking channel.

2

Analiza nośności na ścinanie betonowych próbek zespolonych z wrębami w płaszczyźnie zespolenia

Sadowski Grzegorz, Wiliński Piotr, Halicka Anna

Przegląd Budowlany

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2023

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R. 94, nr 5-6

87--92

PL

W pracy przedstawiono badania próbek zespolonych z powierzchnią prefabrykatu z wrębami oraz referencyjnych elementów monolitycznych. Na podstawie wyników badań laboratoryjnych wykonano modele numeryczne, które posłużyły do analizy sposobu zniszczenia złącza. Przeprowadzono analizę porównawczą efektywności złącza badanych elementów z modelami numerycznymi oraz wynikami badań dostępnymi w literaturze. Badania i analizy wykazały, że zniszczenie złącza nastąpiło przez ścięcie wrębów, poprzedzone zerwaniem adhezji w styku. Nośność złącza uzależniona jest od geometrii próbek oraz sposobu ich obciążenia.

EN

The paper presents tests of composite specimens with the indented surface element and reference monolithic elements. Based on the results of laboratory tests, numerical models were made, which were used for further analysis of the interface cracking. A comparative analysis of the effectiveness of the notches of the tested elements with numerical models and the results of research available in the literature was carried out. Testing and analysis showed that the failure of the joint occurred by notch shear, preceded by adhesion rupture at the interface. The bearing capacity of interface between the concrete depends on the specimens’ geometry and the way they are loaded.

3

Research on stability of rock mass and þ30 level surface construction works when re-exploiting the seam H10 at Mong Duong Coal Mine, Vietnam

Vu Tien T., Dao Doan V.

Journal of Sustainable Mining

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2023

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Vol. 22. iss. 2

100--109

EN

The re-exploitation of coal seams located near the ground is one of the solutions to increase output, reduce mining investment costs, and avoid wasting coal resources. The re-exploitation of coal seams will also cause instability of the surrounding rock mass and may affect surface construction works. Through the process of re-exploiting the longwall in seam H10 at Mong Duong Coal Mine, the authors have studied and evaluated the stability of the rock mass and þ30 level surface works (including fan station and gateroad). To achieve the results in this study, the numerical simulation model method and the analytical method were applied. The model analysis results have determined that the displacement and deformation areas of the rock mass around the mining area correspond to the length of the cut in the strike direction of the longwall H10. The analysis and calculation results from the model show that the longwall in seam H10 can be re-exploited when leaving a protective coal pillar about 50 m from the center of the þ30 fan station at the east side; this distance ensures the stability of the rock mass that located near the ground and the surface works at þ30.

4

Numerical simulation of hydrogen storage in the Konary deep saline aquifer trap

Luboń Katarzyna, Tarkowski Radosław

Gospodarka Surowcami Mineralnymi

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2023

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T. 39, z. 3

103--124

EN

Nowadays, hydrogen is considered a potential successor to the current fossil-fuel-based energy. Within a few years, it will be an essential energy carrier, and an economy based on hydrogen will require appropriate hydrogen storage systems. Due to their large capacity, underground geological structures (deep aquifers, depleted hydrocarbon fields, salt caverns) are being considered for hydrogen storage. Their use for this purpose requires an understanding of geological and reservoir conditions, including an analysis of the preparation and operation of underground hydrogen storage. The results of hydrogen injection and withdrawal modeling in relation to the deep Lower Jurassic, saline aquifer of the Konary geological structure (trap) are presented in this paper. A geological model of the considered structure was built, allowable pressures were estimated, the time period of the initial hydrogen filling of the underground storage was determined and thirty cycles of underground storage operations (gas injection and withdrawal) were simulated. The simulations made it possible to determine the essential parameters affecting underground hydrogen storage operation: maximum flow rate of injected hydrogen, total capacity, working gas and cushion gas capacity. The best option for hydrogen storage is a two-year period of initial filling, using the least amount of cushion gas. Extracted water will pose a problem in relation to its disposal. The obtained results are essential for the analysis of underground hydrogen storage operations and affect the economic aspects of UHS in deep aquifers.

PL

Ze względu na bardzo dużą pojemność podziemne struktury geologiczne (głębokie poziomy wodonośne, sczerpane złoża węglowodorów, kawerny solne) są rozważane do magazynowania wodoru. Ich wykorzystanie w tym celu wymaga rozpoznania uwarunkowań geologiczno-złożowych, w tym analizy przygotowania oraz pracy podziemnego magazynu wodoru. Przedstawiono wyniki modelowania zatłaczania i odbioru wodoru do głębokiego dolnojurajskiego poziomu solankowego struktury geologicznej Konary. Zbudowano model geologiczny rozważanej struktury, oszacowano dopuszczalne ciśnienia szczelinowania oraz ciśnienie kapilarne nadkładu, wyznaczono długości wstępnego okresu zatłaczania wodoru do podziemnego magazynu, przeprowadzono modelowanie przebiegu 30-letniej pracy podziemnego magazynu (zatłaczania i odbioru gazu). Przeprowadzone symulacje umożliwiły określenie istotnych parametrów wpływających na prace podziemnego magazynu wodoru: maksymalną wielkość przepływu zatłaczanego wodoru, pojemność całkowitą, pojemność roboczą i wielkość poduszki gazowej. Pozwoliły stwierdzić, że im dłuższy wstępny okres zatłaczania wodoru, tym większą musimy zastosować poduszkę gazową. Za najlepszą opcję dla magazynowania wodoru zaproponowano dwuletni okres wstępnego zatłaczania gazu do struktury; opcja z najmniejszą wielkością poduszki gazowej. Stwierdzono, że ilość wody, jaka jest eksploatowana w trakcie odzyskiwania wodoru, podczas cyklicznej eksploatacji magazynu, spada wraz ze zwiększeniem długości wstępnego okresu zatłaczania wodoru. Eksploatowana woda będzie stanowiła znaczący problem związany z jej unieszkodliwieniem. Otrzymane wyniki są istotne w analizie pracy podziemnego magazynu wodoru i wpływają na aspekty ekonomiczne UHS w głębokich solankowych poziomach wodonośnych.

5

Numerical simulation study on NO oxidation by OH radical clusters in flue gas

Wen Zhengcheng, Zhang Xiaofeng, Huang Ju, Yang Zhengyin

Environment Protection Engineering

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2023

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Vol. 49, nr 3

69--82

EN

Fenton reaction is an important method to remove NO from flue gas. • OH radicals generated in the Fenton reaction can effectively oxidize NO to NO2, which is absorbed and removed by alkali sorbent. To supply guidance for engineering research, numerical simulation of NO oxidation by • OH radical clusters in flue gas has been carried out using Fluent software. The average concentration of NO on the cross sections at various positions of a cylindrical pipe with a circular surface was calculated by simulation. Under various working conditions (temperature, • OH/NO molar ratio, NO concentration in flue gas, and jet velocity), NO oxidation efficiency by • OH radical was simulated and the key factors affecting NO oxidation were analyzed. The results show that temperature and • OH/NO molar ratio are the key factors affecting the oxidation of NO by • OH radicals. The injection velocity has also a significant effect on the oxidation efficiency while the moisture and oxygen content are minor factors influencing the process. The optimum oxidation efficiency of NO is obtained at 473–523 K, the molar ratio of • OH/NO ca. 1.4, the jet velocity 10 m/s, and the flue gas velocity of 3 m/s.

6

Impact of thermal backfill parameters on current-carrying capacity of power cables installed in the ground

Szultka Seweryn, Czapp Stanisław, Tomaszewski Adam

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 3

art. no. e145565

EN

Proper design of power installations with the participation of power cables buried in homogeneous and thermally well-conductive ground does not constitute a major problem. The situation changes when the ground is non-homogeneous and thermally low-conductive. In such a situation, a thermal backfill near the cables is commonly used. The optimization of thermal backfill parameters to achieve the highest possible current-carrying capacity is insufficiently described in the standards. Therefore, numerical calculations based on computational fluid dynamics could prove helpful for designers of power cable lines. This paper studies the influence of dimensions and thermal resistivity of the thermal backfill and thermal resistivity of the native soil on the current-carrying capacity of power cables buried in the ground. Numerical calculations were performed with ANSYS Fluent. As a result of the research, proposals were made on how to determine the current-carrying capacity depending on the dimensions and thermal properties of the backfill. A proprietary mathematical function is presented which makes it possible to calculate the cable current-carrying capacity correction factor when the backfill is used. The research is expected to fill the gap in the current state of knowledge included in the provisions of standards.

7

Damage and stability analysis of sandstone-type uranium ore body under physical and chemical action of leaching solution

Liu Yulong, Huang Lei, He Guicheng, Hu Nan, Zhou Shuhui, Yu Qing, Ding Dexin

Archives of Mining Sciences

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2023

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Vol. 68, no. 3

409--423

EN

In this paper, the typical sand-conglomerate uranium ore in north China was taken as the research object. The uniaxial compression and tensile tests of sand-conglomerate specimens under natural status and acidic solution status were used to research the compressive strength, tensile strength, Young’s modulus, cohesion and internal friction angle. Focusing on this type of uranium deposit, during the underground design of the in-situ leaching mining method, the three-dimensional finite element method was used to conduct a numerical simulation of the liquid collecting tunnel with different structural parameters of 10 m×2 m, 3 m×2 m, 2 m×2 m, and comprehensively analyse the vertical displacement, principal stress and plastic deformation zone changes of the tunnelbefore and after leaching. Based on the results, influenced by an acidic aqueous solution, the grain of the conglomerate became soft and secondary pores appeared, resulting in the superimposed effect of physical damage and chemical damage. Macroscopically, an obvious decrease was witnessed in mechanical property. Based on the stability and economy factor of three scenarios before and after leaching, the scenario was recommended as the experimental testing scenario, specifically, two longitudinal collecting tunnel were arranged along the strike of the orebody, with the size of 3 m×2 m and the width of the middle pillar of 4 m. The results of the numerical simulation are significant in guiding the design of underground in-situ leaching technology and determining the structural parameters of the deposit.

8

Quantitative Prediction of Air Entrainment Defects in Casting Filling Process

Yin Yajun, Xie Yao, Song Yingchen, Shen Xu, Ji Xiaoyuan, Zhou Jianxin

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 4

117--126

EN

Air entrainment defect is a common type of defect in the casting process, which will seriously affect the quality of the casting. Numerical simulation technology can predict the occurrence of casting defects according to the evolution law of liquid metal in the process of filling and solidification. The simulation of air entrainment process is a hot and difficult issue in the field of numerical simulation. The evolution law of air entrainment and the tracking of induced bubbles in the process of metal filling are still lacking. So is the quantitative prediction of trained gas. In this paper, based on the numerical simulation software of Inte CAST, this paper proposes an algorithm for air entrainment search and tracking, which is used to develop a quantitative prediction system for air entrainment. The feasibility of the system is verified through the simulation calculation of the typical test pieces of the air entrainment and the prediction of air entrainment defects of the casting in the process of filling is obtained through the simulation calculation of the actual casting, which can provide a certain guiding role for the optimization of the process in the production practice.

9

Uniaxial compression test and numerical simulation of rock-like specimen with T-Shaped cracks

Liangxiao Xiong, Chen Haijun, Xu Zhongyuan, Hu Deye

Archives of Civil Engineering

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2023

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Vol. 69, nr 2

227--244

EN

In this study, the uniaxial compression test and PFC2D numerical simulation were carried out on the artificial rock specimen with T-shaped prefabricated fractures. The effects of the lengths l1, l2 of the main fractures, the length l3 of the secondary fracture, and the angle β between the secondary fracture and the loading direction on the uniaxial compressive strength and crack evolution law of specimen were studied. The research results show that the change of l1, l2 and β has obvious effect on the compressive strength and crack growth of the specimen, but the change of l3 has little effect on the compressive strength of the specimen. When l3 = 40 mm and l1 ≠ l2, the angle β influences on the crack propagation and failure mode of the specimen.

10

Refined energy method for the elastic flexural-torsional buckling of steel H-section beam-columns. Part II: Comparison and verification for elements LTU and LTR

Giżejowski Marian, Barszcz Anna, Wiedro Paweł

Archives of Civil Engineering

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2023

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Vol. 69, nr 2

265--289

EN

In investigations constituting Part I of this paper, the effect of approximations in the flexural-torsional buckling analysis of beam-columns was studied. The starting point was the formulation of displacement field relationships built straightforward in the deflected configuration. It was shown that the second-order rotation matrix obtained with keeping the trigonometric functions of the mean twist rotation was sufficiently accurate for the flexural-torsional stability analysis. Furthermore, Part I was devoted to the formulation of a general energy equation for FTB being expressed in terms of prebuckling stress resultants and in-plane deflections through the factor k1. The energy equation developed there was presented in several variants dependent upon simplified assumptions one may adopt for the buckling analysis, i.e. the classical form of linear eigenproblem analysis (LEA), the form of quadratic eigenproblem analysis (QEA) and refined (non-classical) forms of nonlinear eigenproblem analysis (NEA), all of them used for solving the flexural-torsional buckling problems of elastic beam-columns. The accuracy of obtained analytical solutions based on different approximations in the elastic flexural-torsional stability analysis of thin-walled beam-columns is examined and discussed in reference to those of earlier studies. The comparison is made for closed form solutions obtained in a companion paper, with a scatter of results evaluated for k1 = 1 in the solutions of LEA and QEA, as well as for all the options corresponding to NEA. The most reliable analytical solution is recommended for further investigations. The solutions for selected asymmetric loading cases of the left support moment and the half-length uniformly distributed span load of a slender unrestrained beam-column are discussed in detail in Part II. Moreover, the paper constituting Part II investigates how the buckling criterion obtained for the beam-column laterally and torsionally unrestrained between the end sections might be applied for the member with discrete restraints. The recommended analytical solutions are verified with use of numerical finite element method results, considering beam-columns with a mid-section restraint. A variant of the analytical form of solutions recommended in these investigations may be used in practical application in the Eurocode’s General Method of modern design procedures for steelwork.

PL

W I części niniejszej pracy zastosowano różne rodzaje aproksymacji w analizie wyboczenia giętno-skrętnego elementów ściskanych i zginanych w płaszczyźnie większej bezwładności przekroju. Punktem wyjścia było sformułowanie zależności na pole przemieszczeń w konfiguracji odkształconej. Pokazano, że macierz rotacji, otrzymana przy zachowaniu funkcji trygonometrycznych średniego kąta skręcenia, jest wystarczająco dokładna do analizy stateczności giętno-skrętnej. Szczególną uwagę zwrócono w Części I na sformułowanie ogólnego równania energetycznego dla FTB, wyrażonego w funkcji sił przekrojowych na podstawowej ścieżce równowagi, przed utratą płaskiej postaci zginania II rzędu, a także wpływu efektu ugięć w płaszczyźnie większej bezwładności przekroju, wyrażonego za pomocą współczynnika k1. Otrzymane równanie energetyczne zostało przedstawione w kilku wariantach zależnych od założeń upraszczających, jakie można przyjąć do rozwiązywania problemów wyboczenia giętno-skrętnego, tj. w postaci klasycznej analizy liniowego problemu własnego (LEA), w postaci kwadratowego problemu własnego (QEA) oraz w postaci udoskonalonej (nieklasycznej) analizy nieliniowego problemu własnego (NEA). W części II, w pierwszej kolejności, została zbadana i dyskutowana dokładność otrzymanych rozwiązań analitycznych w odniesieniu do propozycji przedstawionych we wcześniejszych opracowaniach. Przeprowadzone są też porównania dla rozwiązań w postaci zamkniętej uzyskanych w Części I, z oceną rozrzutu wyników, po przyjęciu k1 = 1 w rozwiązaniach odpowiadających LEA i QEA, a także wszystkich opcji w rozwiązaniach odpowiadających NEA. Do dalszych badań rekomendowano najbardziej wiarygodne rozwiązanie analityczne. Szczegółowej weryfikacji poddano rozwiązania uzyskane dla wybranych asymetrycznych przypadków obciążenia: momentem na lewej podporze i równomiernie rozłożonym obciążeniem w połowie długości nieusztywnionego, smukłego elementu ściskanego i zginanego. Ponadto w Części II zbadano, w jaki sposób kryterium wyboczeniowe, uzyskane dla elementu ściskanego i zginanego bez usztywnień poprzecznych i przeciwskrętnych między przekrojami końcowymi, może być zastosowane dla elementu z dyskretnymi stężeniami poprzecznymi. Zalecane rozwiązania analityczne zweryfikowano z wykorzystaniem wyników numerycznych metody elementów skończonych dla elementów stężonych w przekroju środkowym. Wariant analitycznej postaci rozwiązania zalecanego w zaprezentowanych badaniach może być wykorzystany w praktyce w eurokodowej Metodzie Ogólnej (GM).

11

Experimental study on the dynamic tensile mechanical properties of marble under water and oil conditions

Li Chaoxin, Liu Dongyan, Zhu Yunhui

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

317--330

EN

To investigate the dynamic tensile properties and energy dissipation characteristics of marble in three different conditions: dry, water-saturated, and oil-saturated, a Brazilian disk splitting test was conducted using a 50 mm diameter Hopkinson pressure bar (SHPB) device. The findings indicate that the peak strain and dynamic tensile strength of the three conditions increase with strain rate, exhibiting a clear strain rate effect. Additionally, lubricating effects of water and oil weaken internal shear sliding friction, thus promoting crack expansion. Furthermore, immersion of fluid in marble weakens the cementation of internal mineral particles, leading to lower tensile strength of marble saturated with water and oil compared to dry marble under dynamic impact. When analyzing the energy dissipation of marble, both the absorption energy and dissipation energy density increase with oil strain rate, indicating a positive correlation. Moreover, numerical results obtained from ANSYS/LS-DYNA correspond well with experimental data, thus verifying and interpreting the experimental outcomes.

12

Buckling resistance of metal columns with smoothly variable cross sections

Błażejewski Paweł, Klekiel Tomasz, Kołodziej Sebastian, Marcinowski Jakub, Sakharov Volodymyr

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

613--628

EN

Metal columns of hollow and smoothly variable cross-sections, simply supported at their ends are considered in the paper. Columns of such shapes are recently frequently designed by architects in public utility buildings of various types. In thiswork authors present the comparatively simple method of buckling resistance assessment which can be used by designers of metal columns of such shapes. The formula on critical force required in the procedure was derived for columns of variable cross section by means of Mathematica™ system. The closed formulae were obtained for a rod with a certain, predefined geometry being the surface of revolution. Critical forces obtained by means of derived formulae were compared with results of numerical solutions. To assess the compression resistance of considered rods the general Ayrton-Perry approach was applied and bow imperfection with assumed amplitude was used in the analysis. Results of numerical simulations and experimental tests inserted in the paper confirm the correctness and the effectiveness of the proposed procedure of buckling resistance assessment of considered struts.

PL

Przedmiotem rozważań zaprezentowanych w artykule są słupy metalowe o przekroju pierścieniowym zmiennym wzdłuż ich osi wzdłużnej i swobodnie podpartych na końcach. Słupy tego kształtu są ostatnio często projektowane przez architektów w różnego typu obiektach użyteczności publicznej. Relatywnie prosty sposób oszacowania nośności wyboczeniowej słupów rozważanego kształtu został zaprezentowany przez autorów pracy. Wzór na siłę krytyczną niezbędną do oszacowania nośności wyboczeniowej został wyprowadzony z wykorzystaniem systemu Mathematica™. Zamknięte wzory na siły krytyczne zostały wyprowadzone dla pewnej klasy prętów o wstępnie zdefiniowanej geometrii stanowiącej powierzchnię obrotową. Siły krytyczne otrzymane z pomocą wyprowadzonych wzorów były porównane z wynikami symulacji numerycznych. Aby oszacować nośność wyboczeniową zastosowano ogólne podejście Ayrton-Perry’ego i wstępne wygięcie łukowe prętów o założonych różnych amplitudach. Wyniki symulacji numerycznych i badań eksperymentalnych zamieszczone w pracy potwierdziły poprawność i efektywność zaproponowanej metody szacowania nośności wyboczeniowej rozważanych prętów.

13

Theoretical and experimental analysis of guided wave propagation in plate-like structures with sinusoidal thickness variations

Zima Beata, Moll Jochen

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e34, 2023

EN

Guided waves have attracted significant attention for non-destructive testing (NDT) and structural health monitoring (SHM) due to their ability to travel relatively long distances without significant energy loss combined with their sensitivity to even small defects. Therefore, they are commonly used in damage detection and localization applications. The main idea of incorporating guided waves in NDT and SHM is based on processing the received signals and appropriate interpretation of their characteristics. A great amount of research devoted to diagnostics of plate-like structures considers specimens with constant thickness, which significantly facilities the diagnostic process. In such a case the velocity is also assumed to be constant. However, the developed diagnostic methods should be applicable, especially for the structures exposed to an aggressive environment, excessive load, or unfavorable weather conditions, etc., when the probability of damage occurring is much higher. In such cases, the assumption about the uniform thickness alongside the propagation path cannot be applied in every case. Thus, the present study is focused on wave propagation in metallic plates with variable thickness. The results of theoretical, numerical and experimental investigations of antisymmetric Lamb mode propagation in aluminum plates with a sine-shaped surface are presented. In the first step, the influence of non-uniform thickness distribution on wave velocity has been described. Next, the inverse problem aimed at shape reconstruction based on time of flight (ToF) analysis and spatially varying wave velocity was solved and compared with the standard dispersion curve-fitting method.

14

Study on force reduction mechanism in ultrasonic-assisted grinding based on single-grain scratching

He Yuhui, Zhang Jiajia, Zhou Weihua, Tang Jinyuan, Xu Yanbin, Zhang Yutong

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e80, 2023

EN

Ultrasonic vibration-assisted grinding (UAG) has been proven to be a promising grinding ability improvement technique due to the grinding force reduction. However, the reduction mechanism is still unclear due to the lack of knowledge on material softening and grain-workpiece contact conditions in UAG. In this paper, we present a numerical and experimental study on ultrasonic vibration-assisted scratching (UAS) to understand the force reduction mechanism for UAG from a single-grain perspective. Based on crystal plasticity theory and dislocation density model, the constitutive model for ultrasonic-assisted deformation is established, in which the infuence of vibration amplitude and strain rate is considered. To further study the acoustic softening effect, the ultrasonic assisted tensile test is conducted. The finite element model for UAS is developed with the kinematic analysis and the consideration of acoustic softening effect. The comparison between the simulated and experimental results indicates that the process force reduction under ultrasonic vibration can be attributed to (1) the reduction of contact area due to the path interference effect and (2) the yield stress reduction due to the acoustic softening effect. This research can deepen the understanding of the beneficial effect of ultrasonic vibration in UAG and offers new insight for studying other ultrasonic-assisted machining method.

15

Investigation of the mechanical and hygrothermal behavior of coffee ground wastes valorized as a building material: analysis of mix designs performance and sorption curve linearization effect

Hamdaoui Mohamed Ali, Benzaama Mohammed-Hichem, El Mendili Yassine, Chateigner Daniel, Gascoin Stéphanie

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e57, 2023

EN

Coffee ground wastes (CGW) are by-products from the coffee-making processes. In this study, we propose to valorize them in construction materials at large scale. In particular, we investigate the mechanical and hygrothermal performances of earthen cob construction with incorporation of various amounts of CGW. Our results indicate that adding coffee grounds to cob enhances its hygrothermal performances as well as its compressive strength. An interesting enhancement of the lightened earth thermal characteristics as well as a good control of the hydric load in the air while maintaining acceptable mechanical properties is observed. Numerical analysis is used to evaluate the hygrothermal behavior of cob specimens to better understand their energy performances. A simplification of the simulation methods using a linearization of the sorption curve is incorporated to reduce calculation times and optimize outputs. The method is validated using experimental data, which shows a promising improvement compared to previous approaches. The proposed method can be faithfully applied to the study of hygrothermal behavior of biomaterials, which is strongly related to the building energy performance and the investigation of their durability in a fast and effcient way.

16

Three-dimensional numerical study of the behavior of thermoelectric and mechanical coupling during spark plasma sintering of a polycrystalline material

Kriba Abdelmalek, Mechighel Farid

Archive of Mechanical Engineering

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2023

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LXX, nr 4

497--529

EN

Spark plasma sintering (SPS) is a promising modern technology that sinters a powder, whether it is ceramic or metallic, transforming it into a solid. This technique applies both mechanical pressure and a pulsed direct electric current simultaneously. This study presents a three-dimensional (3D) numerical investigation of the thermoelectric (thermal and electric current density fields) and mechanical (strain-stress and displacement fields) couplings during the SPS process of two powders: alumina (ceramic) and copper (metallic). The ANSYS software was employed to solve the conservation equations for energy, electric potential, and mechanical equilibrium simultaneously. Initially, the numerical findings regarding the thermoelectric and mechanical coupling phenomena observed in the alumina and copper specimens were compared with existing numerical and experimental results from the literature. Subsequently, a comprehensive analysis was conducted to examine the influence of current intensity and applied pressure on the aforementioned coupling behavior within the SPS device. The aim was to verify and clarify specific experimental values associated with these parameters, as reported in the literature, and identify the optimal values of applied pressure (5 MPa for alumina and 8.72 MPa for copper) and electric current (1000 A for alumina and 500 A for copper) to achieve a more homogeneous material.

17

Investigation of mechanical motion amplification for vibration energy harvesting

Satpute Nitin, Iwaniec Marek, Narina Ramesh, Satpute Sarika

Vibrations in Physical Systems

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2022

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Vol. 33, nr 1

art. no. 2022113

EN

Vibration Energy Harvesting is being investigated for autonomous sensors and actuators that mainly utilize ambient and machine induced vibrations. Recently mechanical motion amplification is incorporated for improving power to weight ratio of vibration harvesters. The present study is motivated to investigate mechanical motion amplification characteristics with different configurations. The parameters investigated are motion amplification ratio, force transmissibility characteristics, weight of the electrical generator, effective damping coefficient achieved and linear nature of damping. Numerical analysis has been performed to compare important characteristics of device operating without amplification to that of with amplification with different configuration. The study has been concluded with comments on application of suitable type of amplification mechanism depending on weight/space constraints and desired effective damping coefficient.

18

Akustyka przeszkleń architektonicznych - podstawy zasad przenoszenia dźwięku i właściwości folii akustycznych

Ju Hengyi

Świat Szkła

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2022

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R. 27, nr 4

45--48

19

Badania innowacyjnego układu sterowania systemem fotowoltaicznym (PV)

Graca Kamil, Matura Dawid, Kupczyk Michał, Pitlok Tomasz, Zgliczyński Sławomir

Śląskie Wiadomości Elektryczne

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2022

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Nr 6 (144)

4--8

PL

Artykuł przedstawia proces tworzenia oraz efekt końcowy, którym było opracowanie układu sterowania oraz algorytmu regulującego pracą systemu fotowoltaicznego (PV – od angielskiego słowa photovoltaics). W celu przeprowadzenia analizy wpływu warunków środowiskowych na blok fotowoltaiczny, została przygotowana wirtualizacja realnego obiektu oraz symulacje numeryczne.

EN

The article presents the process of creating and end results of development of the control system with steering algorithm. In order to analyze the influence of environmental conditions on the photovoltaic unit, the virtualization of a real object and numerical simulations were prepared.

20

Modelowanie numeryczne przewodów złożonych z nadprzewodników wysokotemperaturowych

Kubiczek Krzysztof, Kampik Marian

Przegląd Elektrotechniczny

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2022

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R. 98, nr 12

48--51

PL

Ze względu na swoje zalety, w szczególności duży prąd krytyczny i duże krytyczne pole magnetyczne, taśmy typu Rare-Earth Barium Copper Oxide (REBCO) są jednymi z najbardziej obiecujących nadprzewodników wysokotemperaturowych. Uzyskiwany rozkład pola magnetycznego dla bardziej złożonych struktur, takich jak na przykład przewodów zbudowanych z taśm nadprzewodzących, może być symulowany numerycznie na podstawie pomiarów laboratoryjnych. W pracy przedstawiono metodykę takich symulacji: od pomiarów pojedynczej próbki do symulacji złożonych struktur nadprzewodzących.

EN

Rare Earth Copper Oxide (REBCO) tapes are one of the most promising high temperature (HTS) superconductors due to their advantages such as high critical current and high critical magnetic field. Magnetic field distribution of complex structures, for example cables composed of abovementioned tapes, can be numerically modeled based upon laboratory measurement results. This article presents step-by-step the method of modeling of complex structures.