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1

Computational Methods of the Identification of Chaboche Isotropic-Kinematic Hardening Model Parameters Derived from the Cyclic Loading Tests

Wójcik Marta, Gontarz Andrzej, Skrzat Andrzej, Winiarski Grzegorz

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no 1

61--75

EN

The Chaboche-Lemaitre combined isotropic-kinematic hardening model (CKIH) gives an overall information about the material behaviour under cyclic loading. The identification of hardening parameters is a difficult and time-consuming problem. The procedure of the parameters identification using the experimental hysteresis curve obtained in a cyclic loading test under strain control is presented in details here for a S235JR construction steel. The last stabilized cycle extracted from the hysteresis curve is required for the identification of hardening parameters. The model with three backstresses is tested here. The optimization algorithm is also used for the improvement of the agreement between experimental and numerical data. In order to include some uncertainty of experiment and the identification procedure, the authorial algorithm written on the basis of the fuzzy logic soft-computing method is applied here. The results obtained show that the identification procedure presented in this paper ensures the good agreement between the experimental tests and numerical calculations. The correct selection of parameters associated with the hardening is essential for the right description of material behaviour subject to loading in different engineering problems, including in metal forming processes.

2

Effect of the Addition of Dispersed Reinforcement on the Resilient Modulus of Slightly Cemented Non-Cohesive Soil

Wasil Mariola, Dobrzycki Patryk, Zabielska-Adamska Katarzyna

Studia Geotechnica et Mechanica

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2023

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Vol. 45, nr s1

293--303

EN

The aim of this article is to determine the effect of the addition of dispersed reinforcement on the resilient modulus of non-cohesive soil used as material for improved subgrade or subbase course of the pavement structure. Resilient modulus (Mr) is a parameter used in road construction, which characterises soil subgrade or base aggregates stiffness in flexible pavement subjected to the traffic load. This article presents laboratory test results of non-cohesive coarse material (gravelly sand – grSa – without fines) with the addition of 1.5% cement and dispersed reinforcement – polypropylene fibres in lengths of 12, 18 and 40 mm. Tests were conducted on the samples with various percentages of fibres (0, 0.2 and 0.3%) relating to the dry mass of the soil. Samples were compacted according to the standard Proctor (SP) and modified Proctor (MP) methods. Main laboratory tests were conducted in the triaxial apparatus enabling testing samples subjected to cyclic loads according to AASHTO T307 standard. Resilient modulus was determined after 7 and 28 days of curing. The results indicate the influence of fibre amount, fibre length, and curing time on the Mr of the soil modified with 1.5% of cement. The obtained results were also influenced by the method of compaction. The addition of polypropylene fibres decreases the resilient modulus of soil stabilised by 1.5% of cement. The best results of dispersive reinforcement were obtained for samples containing 0.3% of fibres with a length of 18 mm, compacted by the MP methods.

3

Shear modulus and damping ratio of recycled concrete aggregate from cyclic torsional shear test

Gabryś Katarzyna

Roads and Bridges - Drogi i Mosty

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2023

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Vol. 22, no. 4

387--398

EN

This study examines the small-strain dynamic properties of three mixtures of recycled concrete aggregate (RCA) using laboratory investigations typical of natural soils, namely cyclic torsional shear (CTS) tests. In order to construct two samples, crushed concrete curbs originating from a demolition site in Warsaw was employed. To create the third sample, crushed concrete from demolished buildings also Warsaw was used, mainly from concrete wall and floor elements. A series of CTS tests were performed to investigate the impact of various parameters, including confining pressure, excitation frequency, and number of vibration cycles on the G−modulus, Gmax−modulus, shear modulus degradation curve G(γ)/Gmax, D−ratio, Dmin−ratio, variation in damping curve D(γ)/Dmin. The resulting stiffness and damping characteristics of the analysed concrete aggregate were compared with those of natural gravel and sand aggregate – natural aggregate (NA). The results collected from the CTS tests indicate that the performance of most RCA is comparable to that of NA and can be used as an unbound granular material (UGM).

PL

W niniejszym badaniu zbadano właściwości dynamiczne przy małych odkształceniach trzech mieszanek kruszywa betonowego z recyklingu (RCA) przy użyciu badań laboratoryjnych typowych dla gruntów naturalnych, a mianowicie badania cyklicznego ścinania skrętnego (CTS). Do wykonania dwóch próbek wykorzystano pokruszone krawężniki betonowe pochodzące z rozbiórki w Warszawie. Do stworzenia trzeciej próbki wykorzystano pokruszony beton z rozebranych budynków, także z Warszawy, głównie z betonowych elementów ścian i podłóg. Przeprowadzono serię testów CTS w celu zbadania wpływu różnych parametrów, w tym ciśnienia ograniczającego, częstotliwości wzbudzenia i liczby cykli wibracji na moduł G, moduł Gmax, krzywą degradacji modułu ścinania G(γ)/Gmax, współczynnik D, współczynnik Dmin, zmianę krzywej tłumienia D(γ)/Dmin. Uzyskane charakterystyki sztywności i tłumienia analizowanego kruszywa betonowego porównano z charakterystykami naturalnego kruszywa żwirowo-piaskowego – kruszywa naturalnego NA). Wyniki zebrane z badań CTS wskazują, że wydajność większości destruktu betonowego jest porównywalna z kruszywem naturalnym i może być stosowana jako niezwiązany materiał ziarnisty (UGM).

4

Mechanical properties and energy of sandstone under cyclic loading in evolutionary pattern experimental studies

Xu Daqiang, Zhang Peisen, Yan Wei, Zhang Xiaole, Dong Yuhang, Niu Hui

Archives of Mining Sciences

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2023

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Vol. 68, no. 2

351--370

EN

In order to explore the mining failure law of deep coal seam floor and clarify the mechanical behavior and energy change in the floor strata during mining, the mechanical properties and energy evolution law of sandstone under cyclic loading with different confining pressures (20, 30, 40 MPa) were studied using the Rock Top multi-field coupling tester. The results are as follows: (1) the hysteresis phenomenon of a rock stress-strain curve under cyclic loading is evident. Moreover, the hysteresis loop migrates to the direction of strain increase, and the fatigue damage caused by cyclic loading has a certain weakening effect on the peak strength of rock; (2) both the number of cycles and the axial strain show a nonlinear change characteristic that satisfies the quadratic function relationship. Among them, the stress level of the rock is the main factor affecting the fitting effect; (3) under the same confining pressure, with an increase in cycle level, the macroscopic deformation of the rock increases, the accumulation of fatigue damage in the sample increases, and the irreversible deformation of the rock increases, which leads to an increase in energy input and dissipation; (4) in terms of elastic energy and dissipation energy, elastic energy plays a dominant role. In the initial cycle, the rock is destroyed, and the rock energy loss is great. After the second cycle, the input energy is mainly stored in the rock in the form of elastic energy, and only a small part of the input energy is released in the form of dissipation energy; (5) the confining pressure can improve the efficiency of rock absorption and energy storage, enhance the energy storage limit of rock, and limit the dissipation and release of partial energy of rock. The greater the confining pressure, the more evident the limiting effect, and the more significant the dominant position of elastic energy; and (6) the change in the energy dissipation ratio can be divided into three stages: rapid decline stage, stable development stage and rapid rise stage. The greater the increase in dissipation energy, the greater the degree of rock damage. The evolution process of the energy dissipation ratio can reflect the internal damage accumulation process of rock well, which can be used as the criterion of rock instability.

5

Experimental investigations of steel cold-formed moment-resisting bolted lap joints under monotonic and cyclic loading

Budziński Rafał, Ślęczka Lucjan

Archives of Civil Engineering

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2023

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Vol. 69, nr 4

359--377

EN

Joints in cold-formed steel framing structures are usually designed as bolted lap type ones with a gusset plate. Unlike the end-plate joints in hot-rolled structures, the load in such joints is transferred through shearing of the bolts and bearing of the material. The prediction of their structural properties may be problematic in view of unfavourable influence of the hole clearance and hole ovalization resulting from low bearing resistance of thin walls. A few experimental programmes showed that these issues lead to a different behaviour of the whole joint comparing to common end plate type. These concerns may be particularly important for joints under variable loading, which are prone to deterioration of structural properties. The testing programme conducted by the authors was focused on their behaviour under monotonic and cyclic loading with attention to a potential drop of resistance and stiffness. Monotonic tests revealed quite similar course of the joints’ response. In view of high deformability of the specimens at the intermediate stage of each monotonic test, plastic moment resistances of joints were associated with the initial part of the moment-rotation curves and were multiple times lower than maximum moments obtained in the experiments. The quantities of deterioration of structural properties were determined based on cyclic tests. Drop of resistance and stiffness was observed for several levels of loading range, but the trend of decrease varied for each property. Application of the DIC technique allowed one to identify qualitatively and quantitatively the sources of joint deformability.

PL

Węzły w stalowych konstrukcjach szkieletowych z elementów giętych na zimno są zwykle projektowane jako śrubowe zakładkowe z blachą węzłową. W odróżnieniu od wariantu doczołowego, powszechnego w konstrukcjach z kształtowników walcowanych na gorąco, obciążenie jest w nich przekazywane poprzez ścinanie śrub i docisk do ścianek elementów. Ich projektowanie może nastręczać trudności jeśli chodzi o przewidywanie właściwości strukturalnych związanych z obrotem, a więc sztywności i ciągliwości. Wynika to z niekorzystnych i trudnych w analizie przemieszczeń wewnątrz złączy śrubowych. Składają się na nie luzy występujące pomiędzy trzpieniem śruby a otworem oraz owalizacja otworów pod obciążeniem spowodowana małą nośnością cienkich ścianek na docisk. Wiele dotychczas przeprowadzonych badań doświadczalnych wykazało, że wspomniane wpływy prowadzą do innego zachowania się tego typu węzłów w porównaniu z wariantem doczołowym. Zagadnienia te mogą okazać się szczególnie niekorzystne przy działaniu obciążeń zmiennych, prowadzących do potencjalnej degradacji właściwości strukturalnych. W niniejszym artykule przedstawiono podsumowanie autorskich badań doświadczalnych śrubowych węzłów zakładkowych, pełniących funkcję połączenia okapowego w stalowej ramie portalowej z kształtowników giętych na zimno. Celem badań było określenie ich zachowania się pod wpływem obciążeń monotonicznych i cyklicznych ze zwróceniem szczególnej uwagi na potencjalną degradację nośności i sztywności. Nowością opisaną w artykule jest zastosowanie techniki DIC (Digital Image Correlation), która pozwoliła na jakościową i ilościową identyfikację źródeł odkształcalności węzłów. Badania przeprowadzono na stanowisku doświadczalnym przygotowanym dla węzłów narożnych konstrukcji stalowych. Elementy próbne składały się z fragmentu rygla i słupa ramy portalowej (odpowiednio element pionowy i poziomy), połączonych w sposób zakładkowy z wykorzystaniem blachy węzłowej. Siła generująca moment zginający w węźle przykładana była poziomo w swobodnym końcu rygla (element pionowy) dzięki wykorzystaniu siłownika hydraulicznego. Następnie obciążenie przekazywane było na słupek (element poziomy), który był połączony pośrednio z podłogą siłową za pomocą dwóch podpór przegubowych.

6

Earthquake protection of reinforced concrete structures with infill walls using PUFJ and FRPU systems

Kwiecień Arkadiusz, Akyildiz Ahmet Tugrul

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

199--216

EN

Advancements in technology and material sciences lead new solutions to be used in civil engineering. PolyUrethane Flexible Joints (PUFJ) and Fiber Reinforced PolyUrethanes (FRPU) are among those innovative solutions. PUFJ implemented systems comprise of seismic preventive buffer material between masonry infill walls and reinforced concrete (RC) frames, whereas FRPU solution is designed for covering the wall surfaces with thin composite strips. Both methods are primarily developed for increasing the ductility capacities of buildings while sustaining the overall structural strength without compromising on the safety of these systems against earthquakes. In this article, test results of the quasi-static cyclic experiments as well as dynamic tests on the shake tables including harmonic forces operating in resonance are presented. Moreover, numerical analyses are performed in order to comprehend the behavior of PUFJ implemented frames constituted with different masonry materials than above which are under various loading conditions. The outcomes confirmed the high efficiency of the proposed solutions, which at the same time meet the strict requirements of the modern seismic standards.

PL

Postępy w technologii i materiałoznawstwie prowadzą do nowych rozwiązań wprowadzanych w inżynierii lądowej. Wśród tych innowacyjnych rozwiązań znajdują się podatne złącza poliuretanowe (PUFJ) i poliuretany wzmocnione włóknami (FRPU). Systemy PUFJ instalowane są pomiędzy murowanymi ścianami wypełniającymi a ramami żelbetowymi jako anty-sejsmiczny element buforowy, natomiast systemy FRPU są przeznaczone do wzmacniania powierzchni ścian cienkimi pasami kompozytowymi. Obie metody zostały opracowane w celu zwiększenia ciągliwości budynków, przy jednoczesnym utrzymaniu ich ogólnej nośności, a tym samym w celu zwiększenia bezpieczeństwa użytkowania tych budynków w trakcie trzęsień ziemi. W artykule przedstawiono wyniki badań elementów w skali naturalnej pod quasi-statycznymi obciążeniami cyklicznymi oraz obciążeniami dynamicznymi na stole sejsmicznym i pod działaniem sił harmonicznych w rezonansie. Ponadto zostały przeprowadzone analizy numeryczne, mające na celu poznanie zachowania się podobnych konstrukcji z innymi materiałami murowymi współpracującymi z PUFJ, które poddane zostały różnym warunkom obciążenia. Wyniki potwierdziły wysoką skuteczność proponowanych rozwiązań, które jednocześnie spełniają surowe wymagania współczesnych norm sejsmicznych.

7

Quasi-static cyclic loading experiment and analysis of double-side slotted steel tube shear damper

Hui Cun, Zhou Zhongyi, Li Yonggang, Jiao Yongkang, Hai Ran

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e45, 2023

EN

The traditional shear type damper is optimized, and a low-cost double-sided slotted steel tube shear damper with steel tube is proposed. The elastic-plastic deformation in the plane of the slotted steel plate on the side of the steel tube is used to absorb the seismic energy to achieve the purpose of vibration reduction. Taking the height, width, joint width and wall thickness of the bending element as the design parameters, four groups of nine double-sided slotted steel tube shear dampers are designed and quasi-static tests are carried out to study the effects of different design parameters on their working performance, energy dissipation capacity and failure characteristics. The test results show that the damper has strong plastic deformation capacity, good seismic performance and energy dissipation capacity. The hysteretic curve is symmetrical and full, which is similar with shuttle shape. The yield displacement is small, but the deformation capacity is strong. Properly increasing the width of bending element and the wall thickness of steel tube is helpful to energy dissipation. The finite element model of the damper is established, and the simulation results are in good agreement with the test results, which verifies the correctness of the finite element model and can provide some reference for related engineering applications.

8

A review of the seismic performance behaviour of hybrid precast beam-to-column connections

Ghayeb Haider Hamad, Sulong N. H. Ramli, Razak Hashim Abdul, Mo Kim Hung, Ismail Zubaidah, Hashim Huzaifa, Gordan Meisam

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e35, 2023

EN

In order to withstand challenges such as earthquakes, it is important to appropriately design the beam-to-column connection of precast structures. Numerous precast connections were designed to be used worldwide to attain satisfactory seismic performance. The failures observed for many beam-column connections were primarily due to the brittle behaviour of poor connection details between the precast concrete members. This review article examines past experimental studies which used hybrid precast connections comprised of three types: (1) dry and wet connections with steel sections (Type I), (2) composite concrete (Type II), and (3) composite concrete and steel sections (Type III). The seismic performance behaviour of these connection types was evaluated and compared with that of the monolithic connections. The analysis showed that both the dry semi-rigid and rigid connections Type I can be implemented in the seismic zones. In addition, most of the wet connections Type I, Type II, and Type III can simulate the behaviour of monolithic rigid connections. Therefore, the wet connections Type I, Type II, and Type III can withstand high seismic excitations. Overall, the performance of hybrid dry connection Type I can be improved by using strengthening technique methods in the connection to maintain the continuity of the PC beam. Moreover, the use of composite materials with and without the steel sections as connector elements in the connection (Type II and Type III) can be a feasible method to simulate the seismic performance of monolithic connections.

9

Development of an advanced constitutive model for spoil-structure interaction problems

Doan Nhat-Phi, Liakou Anna, Garala Thejesh Kumar, Cui Ge, Kantesaria Naman, Halder Koushik, Heron Charles M., Marshall Alec M.

Górnictwo Odkrywkowe

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2022

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R. 63, nr 3

43--50

EN

Revitalisation options for mine spoil heaps is an important issue to consider when planning for post-mining land use. One option is the installation of wind turbines on the spoil heaps, which provide a sustainable energy source. This option poses challenges for foundation design due to the nature of the spoil material, which is usually highly heterogeneous due to the way spoils are deposited, and can contain high proportions of high-plasticity cohesive soils (clay). This paper presents results obtained using an advanced constitutive model that was developed to simulate cohesive mine spoil behaviour and presents model results for the prediction of foundation response under both monotonic and cyclic loading. The model is a modified version of the original isotropic bounding surface plasticity model that additionally involves a damaged-based plastic modulus in order to realistically represent soil strength degradation induced by cyclic action. The model is used for the simulation of shallow foundations for onshore wind turbines on a cohesive clay with a heterogeneous (linearly increasing) undrained shear strength (random spatial variability is not considered). Two different loading scenarios of a shallow strip foundation are considered in the paper: a pure moment-vertical loading (M-V), and a moment-horizontal-vertical loading (M-H-V). The effect of the adopted spoil-foundation interface type is also considered: (1) a fully-bonded interface and (2) a tensionless interface. Results demonstrate that, though the vertical bearing capacity is only slightly affected by the interface properties, the moment capacity is shown to be strongly influenced by the predefined contact conditions. For the footing system under M-H-V loading, a dominant footing uplift mechanism is obtained for light structures and the opposite holds for heavily loaded structures, where significant settlement accumulation occurs during cyclic loading. Based on the analysis, the moment bearing capacity of the footing system decreases as the slenderness ratio and/or the vertical safety factor increase, and the opposite mechanism is obtained as the strength heterogeneity degree increases.

PL

Możliwości rewitalizacji zwałowisk są ważnym zagadnieniem przy planowaniu zagospodarowania terenów pogórniczych. Jedną z opcji jest instalacja na hałdach turbin wiatrowych, które stanowią zrównoważone źródło energii. Opcja ta stanowi wyzwanie dla projektowania fundamentów biorąc pod uwagę charakter materiału zwałowego, który ze względu na sposób deponowania jest zwykle wysoce niejednorodny i może zawierać dużo wysokoplastycznych gruntów spoistych (iłów). W artykule przedstawiono wyniki uzyskane przy użyciu zaawansowanego modelu konstytutywnego, który został opracowany w celu symulacji zachowania spoistego materiału zwałowego oraz zaprezentowano wyniki modelowania dla przewidywania reakcji fundamentu będącego zarówno pod obciążeniem monotonicznym jak i cyklicznym. Model jest zmodyfikowaną wersją oryginalnego izotropowego modelu plastyczności powierzchni granicznej, który dodatkowo zawiera moduł plastyczności oparty na zniszczeniu w celu realistycznego przedstawienia degradacji wytrzymałości gruntu wywołanej działaniem cyklicznym. Model jest wykorzystywany do symulacji płytkich fundamentów turbin wiatrowych na iłach spoistych o niejednorodnej (liniowo wzrastającej) wytrzymałości na ścinanie bez odpływu (nie uwzględniono losowej zmienności przestrzennej). W pracy rozpatrzono dwa różne scenariusze obciążenia płytkiej ławy fundamentowej: czyste obciążenia moment-pionowe (M-V) oraz obciążenia moment-poziome-pionowe (M-H-V). Rozważono również wpływ przyjętego rodzaju styku zwałowisko-fundament: (1) całkowicie związany oraz (2) beznaprężeniowy. Wyniki pokazują, że choć nośność pionowa tylko w niewielkim stopniu zależy od właściwości styku, to okazuje się, że nośność momentu jest silnie uzależniona od zdefiniowanych wcześniej warunków kontaktowych. Dla systemu stopy fundamentowej pod obciążeniem M-H-V, w przypadku lekkich konstrukcji uzyskuje się dominujący mechanizm unoszenia stopy, a w przypadku konstrukcji silnie obciążonych odwrotny, gdzie podczas cyklicznego obciążenia następuje znaczna akumulacja osiadań. Na podstawie przeprowadzonej analizy można stwierdzić, że nośność systemu stopy fundamentowej maleje wraz ze wzrostem współczynnika smukłości i/lub pionowego współczynnika bezpieczeństwa, a odwrotny mechanizm uzyskuje się wraz ze wzrostem stopnia niejednorodności wytrzymałości.

10

Experimental study on fatigue mechanical properties of sandstone after dry and wet cycle

Jin-Song Zhang, Yu Lu, Heng-Liang Zhang, Yu-Di Yang, Yi-Shun Bu

Archives of Civil Engineering

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2022

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Vol. 68, nr 4

377--387

EN

At present, many studies have been carried out on the fatigue mechanical properties of conventional rocks, but there are few studies on the mechanical properties of rocks after water rock interaction. The aim is to better study the fatigue mechanical characteristics of sandstone after dry wet cycle and the research object we take was sandstone samples after a certain number of drying and wetting cycles. The WAW-2000 electro-hydraulic servo pressure system was used to carry out uniaxial fatigue cyclic loading and unloading tests with different amplitudes and different upper limit stresses. The test found that: when the sample is damaged under fatigue load, the stress-strain curve shows a sharp downward trend and a sudden instability failure occurred in the sample. With the increase of the upper limit stress and amplitude, the life of the sample decreases gradually which also conforms to the change of power function. Then the relationship between fatigue life and stress is obtained. The fatigue stress-strain curve is characterized by sparse-dense-sparse. With the increase of cycle time, the axial strain of the sample shows an inverted “S” shape. The strain change can be divided into three stages: initial stage, constant velocity stage and acceleration stage.

11

Wpływ cyklicznych obciążeń mechanicznych na odporność korozyjną aluminium

Strąk Adrian, Francke Barbara

Materiały Budowlane

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2021

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nr 6

2--6

PL

W artykule zaprezentowano wpływ zmęczeniowych obciążeń mechanicznych na odporność korozyjną profili okiennych i drzwiowych wykonanych ze stopu aluminium EN AW-6063 z powłoką poliestrową. W badaniach zastosowano własną metodę oceny, polegającą na cyklicznych obciążeniach skupionych działających na próbkę metodą trójpunktowego zginania. Efektem tych obciążeń było powstanie w obrębie struktury aluminium trwałego odkształcenia plastycznego, podczas gdy w przypadku powłoki pokrywającej profile aluminiowe nastąpiło niewielkie zmniejszenie odporności korozyjnej, niepowodujące jednak utraty właściwości barierowych. Stwierdzono również, że gdy obciążeniom mechanicznym towarzyszy działanie kwaśnej mgły solnej, pojawiają się mikrouszkodzenia w strukturze powłok, w istotny sposób zmniejszając ich właściwości barierowe, co potwierdzono wynikami badań spektroskopii impedancyjnej.

EN

The article presents the effect of mechanical load fatigue on corrosion resistance of profiles made of EN AW-6063 aluminium alloy with polyester coating. In test, own research methodology was used, consisting in cyclical application of concentrated load to the tested sample with the three-point bending method. The effect of these loads was the formation of a permanent plastic deformation within the aluminium structure, while in the case of the coating covering aluminium profiles, there is a slight reduction in corrosion resistance, without the loss of barrier properties, however. It was also found that when in addition to mechanical load, salt spray test was applied, microdamage in the coatings’ structure appeared, significantly reducing their barrier properties, which was confirmed by the results of impedance spectroscopy.

12

Comparative Study of Long- and Short-Stretch Woven Compression Bandages

Aboalasaad Abdelhamid R. R., Sirková Brigita Kolčavová, Bílá Pavlína, Khalil Amany A. S.

Autex Research Journal

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2021

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Vol. 21, no. 4

435--444

EN

Compression therapy using bandages or socks is the most common treatment for venous leg ulcers and edema. This article aims to compare the compression between long- and short-stretch bandages (LSB and SSB, respectively). Load-elongation curves, cyclic loading, and elastic recovery are investigated for both Cotton/Polyamide/Polyurethane and 100% bleached cotton bandages as LSB and SSB, respectively. Static (resting) and dynamic (working) pressures are measured on seven male legs, 31 ± 3.6 years old, using both two and three layers bandaging. Picopress pressure tests are performed on the ankle and mid-calf positions at gradual decreasing compression from the ankle to the knee. The deviation percentage between the experimental results by Picopress and theoretical calculations using Laplace's law and Al-Khaburi equations is compared. LSB recovered approximately 99% of its original length after stress-relaxation whereas SSB recovered only 93% of its original length after 5 days of cyclic load-relaxation. Moreover, SSB lost approximately 28.6% of its activity after wearing on the human leg for 5 days.

13

The Coupled Eulerian-Lagrangian Analysis of the KOBO Extrusion Process

Wójcik Marta, Skrzat Andrzej

Advances in Science and Technology. Research Journal

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2021

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Vol. 15, no 1

197--208

EN

The KOBO extrusion is an unconventional elastic-plastic deformation process in which the phenomenon of chang- ing a path of plastic deformation due to die cyclic oscillations by a given angle and with a given frequency is applied. As the result of the application of the oscillating rotary motion of the die, the reduction of the extrusion force was obtained. The numerical study of the KOBO extrusion of metallic materials was presented in this paper. The three-dimensional coupled Eulerian-Lagrangian (CEL) analysis was applied. The relationship between the extrusion force and the punch displacement during the KOBO process was achieved. The effective plastic strain distribution in the butt was found. The results of the numerical computations were compared with the experimen- tal data. The influence of the material hardening parameters on the cyclic loading phenomena (ratcheting, mean stress relaxation) in terms of the course of the KOBO extrusion was also examined. The proper determination of the material hardening parameters can help to optimize the KOBO process in terms of the reduction the extrusion force and the choice of the amount of die oscillations.

14

Compressive deformation characteristics of crushed sandstone based on multiple experimental factors

Sun Yanan, Zhang Peisen, Yan Wei, Yan Fenqian, Wu Junda

Archives of Mining Sciences

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2020

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Vol. 65, no. 1

129--146

EN

In this study, the compressive deformation of crushed sandstone was tested using a crushed rock deformation-seepage test system, and the effects of various factors, including crushed rock grade, grade combination, water saturation status, and stress loading method (i.e., continuous loading or cyclic loading and unloading), on the compressive deformation of crushed sandstone was analyzed from four perspectives including stress-strain, bulking coefficient, deformation mechanism and energy dissipation. The results indicate that the stress-strain relations of crushed sandstone are closely associated with all factors considered, and are well represented by exponential functions. The strain observed for a given applied stress increased with increasing crushed rock grade throughout the loading period. Crushed sandstone grades were combined according to a grading index (n), where the proportion of large-grade rocks in the sample increased with increasing n. The bearing capacity of a water-saturated crushed sandstone sample with n = 0.2 was less than that of an equivalent dry sample for a given applied stress. The stress-strain curve of a water-saturated crushed sandstone sample with n = 0.2 under cyclic loading and unloading was similar to that obtained under continuous loading. Observation and discovery, the deformation mechanism of crushed sandstone was mainly divided into four stages, including crushing, rupture, corner detachment and corner wear. And 20% of the work done by testing machine is used for friction between the crushed sandstone with the inner wall of the test chamber, and 80% is used for the closing of the void between the crushed sandstone, friction sliding, crushing damage.

15

Analysis of composite shear walls with a gap between reinforced concrete wall and steel frame

Bahrami Alireza, Yavari Mojtaba

Archives of Civil Engineering

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2020

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Vol. 66, nr 1

41--53

EN

In this research, nonlinear analysis of composite shear walls (CSWs) with a gap between reinforced concrete wall and steel frame is investigated under cyclic loading by the use of the finite element method (FEM) software ABAQUS. For the purpose of the verification, an experimental test is modelled and comparison of its obtained result with that of the experimental test demonstrates an inconsiderable difference between them; therefore, the reasonable accuracy of the modelling is revealed. Then, effects of different parameters on the behaviour of the CSWs are examined. Gap size between reinforced concrete wall and steel frame, reinforcement percentage, steel sections of beams and columns, and existence of reinforced concrete wall are considered as parameters. It is concluded that change of the parameters affects the ultimate strength, ductility, and energy dissipation of the system. A steel shear wall (SSW) is also modelled and compared with the CSWs. Buckling of the walls is presented as well.

16

Multiaxial fatigue experimental analysis of 6063-T66 aluminum alloy of the base material and the welded material

Uhríčik Milan, Kopas Peter, Palček Peter, Oršulová Tatiana, Hanusová Patrícia

Quality Production Improvement - QPI

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2019

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Vol. 1, Iss. 1

334--341

EN

This article deals with determining of fatigue lifetime of aluminum alloy 6063-T66 during by multiaxial cyclic loading. The experiments deal with the testing of specimens for identification of the strain-life behavior of material, the modeling of combined loading and determining the number of cycles to fracture in the region of low-cycle fatigue. Fatigue tests under constant amplitude loading were performed in a standard electromechanical machine with a suitable gripping system. Based on the experimental results the fatigue design curves are compared to the fatigue data from the base material and the welded material and also multiaxial fatigue models, which are able to predict fatigue life at different loads.

17

The Experimental Estimation of The Elastic Modulus of a Fly Ash Based Trackbed Layer Under Cyclic Loading

Lojda Vit, Lidmila Martin, Pycha Marek

Inżynieria Mineralna

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2019

|

R. 21, nr 1

119--123

EN

In a railway track structure system, trackbed layers are designed to compensate for insufficient bearing capacity and/or water or frost resistance of natural soil. These, so called, ‘capping layers’ can be constructed from raw materials like sand or gravel or from industrial materials like asphalt or concrete. However, more environmentally and cost friendly alternatives have been studied in recent years. Fly-ash represents one such promising material and a trial section of a main line track with the capping layer made from a fly-ash-based mixture was constructed in Czech Republic in 2005. The performance of the capping layer in the section has been measured since. In this paper, results of the laboratory estimation of the elastic modulus under cyclic traffic-like induced loading are presented for the most recent group of samples. The results show that the elastic limit of the fly-ash-based material lies well above the stresses induced by railway traffic and that its behaviour is stable under the cyclic loading. This suggests that the mechanical properties of the material may not be determinative for the design of the layer and that the feasibility factors may take precedent. This in turn suggests that either the design strength of the material or the designed thickness of the layer may be possibly reduced.

PL

W systemie konstrukcji torów kolejowych warstwy nośne są zaprojektowane tak, aby kompensować niedostateczną nośność i/lub odporność na wodę lub mróz naturalnej gleby. Te tzw. warstwy zamykające mogą być zbudowane z surowców takich jak piasek lub żwir lub z materiałów przemysłowych, takich jak asfalt lub beton. W ostatnich latach badano alternatywy bardziej przyjazne dla środowiska i kosztów. Popiół lotny stanowi jeden z takich obiecujących materiałów, badania w Czechach prowadzono od 2005 r. Wykonano próbny odcinek głównego toru linii kolejowej z warstwą przykrywającą wykonaną z mieszanki na bazie popiołu lotnego. Wydajność warstwy przykrywającej w przekroju została zmierzona. W niniejszej pracy przedstawiono wyniki laboratoryjnej oceny modułu sprężystości przy obciążeniu indukowanym podobnym do ruchu cyklicznego dla najnowszej grupy próbek. Wyniki pokazują, że granica sprężystości materiału na bazie popiołu lotnego leży znacznie powyżej naprężeń wywołanych ruchem kolejowym i że jego zachowanie jest stabilne pod obciążeniem cyklicznym. Sugeruje to, że właściwości mechaniczne materiału mogą nie być decydujące dla konstrukcji warstwy i że materiał może być zastosowany. To z kolei sugeruje, że można albo zmniejszyć wytrzymałość projektową materiału, albo zaprojektowaną grubość warstwy.

18

Evaluation of hot-mix asphalt containing Portland cement treated blast furnace slag

Rondón-Quintana H. A., Ruge-Cardenas J. C., Bastidas-Martínez J. G.

Archives of Civil Engineering

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2019

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Vol. 65, nr 2

193--207

EN

Iron production’s waste materials include significant quantities of blast furnace slag (BFS) which could potentially be used as a substitute for natural aggregates in hot mix asphalt (HMA) used in highway projects. Although many of properties of slag are interesting, its porosity and absorption rate would lead to greater consumption of asphalt. For this study, a Portland cement (PC) paste was used to reduce the porosity of a BFS. This PC treated BFS (called BFS-C) was then used in an HMA to replace the coarse fraction of a natural aggregate. Marshall, Indirect Tensile Strength (ITS), resilient modulus and Cantabro tests were then carried out on different HMA mixtures that included BFS-C. Using BFS-C, HMA’s resistance under monotonic loading, stiffness under cyclic loading, and resistance to moisture damage increased remarkably. In addition, the Cantabro abrasion resistance of BFS-C improved was better than that of the HMA mixture produced with untreated BFS.

19

Ocena trwałości zmęczeniowej końcówki drążka kierowniczego

Szymczak T., Brodecki A., Kowalewski Z., Lasota P.

Transport Samochodowy

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2018

|

z. 2

63--72

PL

W pracy zaprezentowano wyniki badań trwałościowych końcówki drążka kierowniczego pojazdu o dmc powyżej 3.5 tony. W badaniach wykorzystywano wielkogabarytową platformę wibroizolowaną, serwohydrauliczny siłownik mobilny oraz cyfrowy kontroler sygnałów IST Instron. Próby prowadzono w warunkach działania obciążenia zmiennego cyklicznie do uzyskania 2×106 cykli. Ze względu na kompleksową ocenę zachowania końcówki drążka kierowniczego testy przerywano, by wykonywać oględziny obiektu badań. Wyznaczono zmiany kąta wychylenia oraz momentu siły w funkcji liczby cykli oraz przedstawiono ich prognozę. Omówiono procedurę badawczą służącą ocenie trwałości przegubu kulistego.

EN

The paper reports results from test of steering rod tip used in car having permissible total mass above 3.5 t. Anti-vibration platform, servo-hydraulic actuator and digital controller IST Instron were used to execute the tests. The experiments were carried out under cyclic loading up to 2×106 cycles. The tests were interrupted for inspecting the examined object. Variations of angle and force moment and prediction of their values versus number of cycles are presented. Details of experimental procedure for evaluation of steering rod tip are provided.

20

Numerical modelling of innovative DST steel joint under cyclic loading

Lemos A., Da Silva L. S., Latour M., Rizzano G.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 3

687--701

EN

This paper addresses the numerical simulation of an innovative double split Tee beam-to-column joint fitted with a dissipative friction damper, recently proposed at the University of Salerno. The innovative connection prevents damage to all other structural components with the exception of one component of the connection that is specially designed to dissipate the input energy of a seismic hazard by means of the slippage of a friction material. The main topics herein presented are the development of a strategy for the numerical modelling of complex friction problems and a detailed numerical model of the overall beam-to-column joint equipped with the friction device. The joint is subjected to both monotonic and cyclic loading conditions. The numerical modelling was developed using the Finite Elements Method (FEM) with Abaqus Software. Sliding force–displacement curves are obtained for two damper materials and an estimation of their wearing is presented. To evaluate the accuracy of the numerical model, moment–rotation curves of the joint are compared with the experimental curves. The FE results show good correlations and confirm the potential interest of this novel joint typology to achieve easily replaceable details in case of a seismic event.