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1

Finite element model updating of steel-concrete composite bridge: A study case of the Ruri bridge in Vietnam

Nguyen Duc Cong, Salamak Marek, Katunin Andrzej, Gerges Michael, Abdel-Maguid Mohamed

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

425--443

EN

The study presents the finite element (FE) model update of the existing simple-spans steel-concrete composite bridge structure using a particle swarm optimisation (PSO) and genetic algorithm (GA) approaches. The Wireless Structural Testing System (STS-WiFi) of Bridge Diagnostic, Inc. from the USA, implemented various types of sensors including: LVDT displacement sensors, intelligent strain transducers, and accelerometers that the static and dynamic historical behaviors of the bridge structure have been recorded in the field testing. One part of all field data sets has been used to calibrate the cross-sectional stiffness properties of steel girders and material of steel beams and concrete deck in the structural members including 16 master and slave variables, and that the PSO and GA optimisation methods in the MATLAB software have been developed with the new innovative tools to interface with the analytical results of the FE model in the ANSYS APDL software automatically. The vibration analysis from the dynamic responses of the structure have been conducted to extract four natural frequencies from experimental data that have been compared with the numerical natural frequencies in the FE model of the bridge through the minimum objective function of percent error to be less than 10%. In order to identify the experimental mode shapes of the structure more accurately and reliably, the discrete-time state-space model using the subspace method (N4SID) and fast Fourier transform (FFT) in MATLAB software have been applied to determine the experimental natural frequencies in which were compared with the computed natural frequencies. The main goal of the innovative approach is to determine the representative FE model of the actual bridge in which it is applied to various truck load configurations according to bridge design codes and standards. The improved methods in this document have been successfully applied to the Vietnamese steel-concrete composite bridge in which the load rating factors (RF) of the AASHTO design standards have been calculated to predict load limits, so the final updated FE model of the existing bridge is well rated with all RF values greater than 1.0. The presented approaches show great performance and the potential to implement them in industrial conditions.

2

Coupling Characteristics of Needles and Backing Cloth During the Carpet Tufting Process

Xu Yang, Huang Shuang, Sheng Xiaowei, Zhijun Sun

Fibres & Textiles in Eastern Europe

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2022

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Vol. 30, no. 3

9--17

EN

Focusing on the needle and backing cloth on a tufting machine type DHG801D-200, a finite element model was built using ABAQUS/Explicit software. The tufting processes, in which the individual tufting needles and 1/10 needle modules puncture the polypropylene woven and nonwoven fabrics (hot-air bonded nonwoven and thermo-calender bonded nonwoven), were simulated, respectively. Finally, the needle forces were estimated, and the deformations and stress field distribution of the backing cloth at different times were analysed.

3

A novel method for identification of damage location in frame structures using a modal parameters-based indicator

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

Archives of Civil Engineering

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2022

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Vol. 68, nr 3

633--643

EN

Diverse strategies for identifying and finding the damages in structures have been continuously engaging to originators within the field. Due to the direct connection between the firmness, characteristic frequency, and mode shapes within the structure, the modular parameters may well be utilized for recognizing and finding the damages in structures. In current consider, a modern damage marker named Damage Localization Index (DLI) is applied, utilizing the mode shapes and their derivative. A finite element model of a frame with twenty and thirty components has been utilized, separately. The numerical model is confirmed based on experimental information. The indicator has been explored for the damaged components of a frame with one bay. The results have been compared with those of the well-known index CDF. To demonstrate the capability and exactness of the proposed method, the damages with low seriousness at different areas of the structures are explored. The results are investigated in noisy condition, considering 3% and 5% noise on modal data. The outcomes show the high level of accuracy of the proposed method for identifying the location of the damaged elements in frames.

4

Numerical and experimental investigations on Mannesmann effect of nickel‑based superalloy

Zhang Zhe, Liu Dong, Man Tongchi, Li Nan, Yang Yanhui, Pang Yuhua, Wang Jianguo

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e133

EN

The preparation of nickel-based superalloy tubes by rotary tube piercing (RTP) process is still difficult due to the Mannesmann effect (central cracking phenomenon) has not been clarified. The combinations of numerical analysis and experiment verifications method were adopted in the study. The critical parameters for central cracking were determined by experiments. It was found that the evolution process of central cracking for nickel-based superalloy includes voids nucleation, growth and aggregation. Based on the obtained critical parameters, the evolutions of stress, strain, strain rate, temperature and damage were discussed by numerical simulation. By comparing the experiment results and simulation results, the Normalized Cockcroft and Latham (NCL) model was determined as the most suitable model. Considering the influences of temperature and strain rate on the damage threshold, the NCL model of Inconel 718 alloy was established by high-temperature tensile test. Based on the above results, it is found that the maximum shear stress promotes the plastic deformation, which provides necessary conditions for the generation of defects, and the maximum principal stress induces the generation of voids and expansion of micro-cracks, which directly leads to the central cracking. The essence of central cracking is ductile fracture under tensile stress.

5

Experimental and theoretical research on large-diameter rock-socketed pile embedded depth

Li Yanfeng, Zhao Jihe, Xiong Ying, Wang Qinghe

Archives of Civil Engineering

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2021

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Vol. 67, nr 2

537--550

EN

A theoretical formula for large-diameter rock-socket depth is developed to support pail embedding in a large bridge pile foundation project. There is a horizontal additional stress concentration at the place where the soil around the rock-socketed pile meets the soil layer under the horizontal load. When the rock-socketed tip stress and bending moment of the pile are relatively small, the pile shows favourable embedment effect and the pile foundation can be considered safe. The function curve of soil resistance around the pile under the action of horizontal force was obtained by finite element analysis. The force characteristics reveal the depth of the largediameter rock-socketed pile under the horizontal load. As the rock-socketed pile rotates under the action of horizontal force, the rock mass resistance around the pile changes according to the cosine. The distribution of pileside soil resistance is proportional to the displacement and distributed according to the sine. A comprehensive correction coefficient of pile shaft resistance β is introduced to deduce the theoretical formula of the depth hr of the large-diameter rock-socketed pile embedded in the bedrock. It is verified through both experiments and numerical analysis.

6

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

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

Archive of Mechanical Engineering

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2021

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LXVIII, nr 4

375--394

EN

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

7

Konečno-èlementnaâ modelʹ èlektronno-lučevoj pajki tverdosplavnyh režuŝih èlementov k opravke

Goranskij G.G., Pobol A.I

Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo

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2020

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Z. 26 (176)

44-55

RU

Sozdany obobŝennye konečno-èlementnye (KÈ) modeli èlektronno-lučevoj obrabotki (ÈLO) poverhnostej dlâ materialov s suŝestvenno otličaûŝimisâ teplofizičeskimi svojstvami, pozvolâûŝie proizvoditʹ rasčet i optimizaciû režimov processa. Dlâ izdelij raznoj geometrii, učityvaâ termodinamiku processa i temperaturnye zavisimosti svojstv materialov, upravlââ geometriej èlektronnogo pučka i ciklogrammoj processa, optimizirovany diapazony ènergeti českih parametrov ÈLO. KÈ modelirovanie nagreva poverhnosti pri ÈLO provedeno dlâ detali ploskoj formy stacionarnym istočnikom so skaniruûŝej razvertkoj, a takže pri vozdejstvii v režime linejnogo peremeŝeniâ luča bez skaniruûŝej razvertki. Dlâ optimizacii èlektronno-lučevogo oplavleniâ pri pajke predložena termodinamičeskaâ KÈ modelʹ, učityvaûŝaâ geometričeskie osobennosti rezcovyh vstavok i teplofizičeskie svojstva sostavlâûŝih ih materialov. Pokazano, čto učet temperaturnoj zavisimosti teplofizičeskih svojstv materialov pozvolâet realizovyvatʹ shemy ÈLO s menʹšej prodolžitelʹnostʹû vozdejstviâ pučka bolʹšej moŝnosti.

EN

Generalized finite-element models for the electron-beam treatment of the surface of materials with significantly different thermophysical properties have been created, allowing the calculation and optimization of process conditions. For products of different geometries, taking into account the thermodynamics of the process and the temperature dependences of the properties of materials, controlling the electron beam geometry and the process cycloramas, the ranges of energy parameters of electron beam processing have been optimized. Finite-element modeling of surface heating during electron-beam processing was carried out for a flatshaped part by a stationary source with scanning, as well as when exposed to linear beam movement without scanning. To optimize electron beam reflow during soldering, a thermodynamic finite-element model is proposed that takes into account the geometric features of the cutter inserts and the thermophysical properties of their constituent materials. It is shown that taking into account the temperature dependence of the thermophysical properties of the materials makes it possible to realize electron beam processing schemes with a shorter duration of exposure to a beam of greater power.

8

Timoshenko beam model for vibration analysis of composite steel-polymer concrete box beams

Niesterowicz Beata, Dunaj Paweł, Berczyński Stefan

Journal of Theoretical and Applied Mechanics

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2020

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Vol. 58 nr 3

799--810

EN

The free vibration model of a steel-polymer concrete beam based on Timoshenko beam theory is presented in this paper. The results obtained on the basis of the model analysis, describing the values of the natural frequencies of the beam vibrations, were compared with the results obtained by the solution of the model formulated on the basis of the classical Euler-Bernoulli beam theory, the finite element model and the results of experimental studies. The developed model is characterized by high compliance with experimental data: the relative error in the case of natural vibration frequencies does not exceed 0.4%, on average 0.2%.

9

Study on the Trajectory of Free-End Fiber in Jet Vortex Spinning Based on the Elastic Thin-Rod Finite Element Model of Flexible Fiber

Han Chenchen, Gao Weidong, Chen Lifen

Autex Research Journal

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2020

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Vol. 20, no. 1

43--48

EN

During the air flow twisting process of jet vortex spinning, the moving characteristics of flexible free-end fiber are complex. In this paper, the finite element model of the fiber is established based on elastic thin rod element. According to the air pressure and velocity distribution in the airflow twisting chamber of jet vortex spinning, this paper analyzes the undetermined coefficients of the finite element kinetic differential equation of the free-end fiber following the principle of mechanical equilibrium, energy conservation, mass conservation and momentum conservation. Based on numerical simulation, this paper gets the trajectory of the free-end fiber. Finally, the theoretical result of the free-end fiber trajectory by finite element simulating is tested by an experimental method. This paper has proposed a new method to study the movement of the fiber and learn about the process and principle of jet vortex spinning.

10

Verifying of the finite element model of the bridge based on the vibration monitoring at differente stages of construction

Hernandez W., Viviescas A., Riveros-Jerez C. A.

Archives of Civil Engineering

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2020

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Vol. 66, nr 1

25--40

EN

This paper presents the results of a dynamic response evaluation of a segmental bridge during two construction stages: before connecting the final segment of the bridge and after connecting the final segment of the bridge but prior to opening the bridge to traffic. The vibration signals obtained from Ambient Vibration Testing (AVT) campaigns were processed in order to obtain the modal parameters of the bridge during the two construction stages. Modal parameters experimentally obtained for the first stage were compared with those obtained from Finite Element (FE) models considering different construction loads scenarios. Finally, modal parameters experimentally obtained for the second stage were used to update its corresponding FE model considering two scenarios, before and after the installation of the asphalt pavement. The results presented in this paper demonstrated that a rigorous construction control is needed in order to effectively calibrate FE models during the construction process of segmental bridges.

11

Improving the procedure of probabilistic load testing design of typical bridges based on structural response similarities

Owerko P., Winkelmann K.

Archives of Civil Engineering

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2020

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Vol. 66, nr 4

325--342

EN

This paper concerns load testing of typical bridge structures performed prior to operation. In-situ tests of a two-span post-tensioned bridge loaded with three vehicles of 38-ton mass each formed the input of this study. On the basis of the results of these measurements an advanced FEM model of the structure was developed for which the sensitivity analysis was performed for chosen uncertainty sources. Three uncorrelated random variables representing material uncertainties, imperfections of positioning and total mass of loading vehicles were indicated. Afterwards, two alternative FE models were created based on a fully parametrised geometry of the bridge, differing by a chosen global parameter – the skew angle of the structure. All three solid models were subjected to probabilistic analyses with the use of second-order Response Surface Method in order to define the features of structural response of the models. It was observed that both the ranges of expected deflections and their corresponding mean values decreased with an increase of the skewness of the bridge models. Meanwhile, the coefficient of variation and relative difference between the mean value and boundary quantiles of the ranges remain insensitive to the changes in the skew angle. Owing to this, a procedure was formulated to simplify the process of load testing design of typical bridges differing by a chosen global parameter. The procedure allows - if certain conditions are fulfilled - to perform probabilistic calculations only once and use the indicated probabilistic parameters in the design of other bridges for which calculations can be performed deterministically.

PL

Pracę otwiera przegląd najnowszej literatury fachowej o zasięgu międzynarodowym, dotyczącej próbnych obciążeń obiektów mostowych. W licznych publikacjach badawczych jednoznacznie stwierdzono, iż zasadne jest, by często stosowane w tym zakresie metody deterministyczne uzupełniać lub zastępować analizami probabilistycznymi. Niniejsza praca stanowi zatem rozwinięcie dotychczasowych osiągnięć i spostrzeżeń. Przedmiotem pracy jest analiza możliwości zwiększenia efektywności procesu przygotowania probabilistycznych projektów próbnych obciążeń typowych konstrukcji mostowych, różniących się wybranym parametrem geometrycznym (w tym przypadku – kątem ukosu konstrukcji „α”) przed ich dopuszczeniem do eksploatacji w zakresie pomiarów statycznych. Punktem wyjściowym przedstawionej analizy jest próbne obciążenie in-situ typowego, drogowego mostu sprężonego. Jednym z podstawowych kryteriów dopuszczenia obiektu mostowego do użytkowania w niektórych krajach, jest wykazanie, iż ugięcia dźwigarów głównych obiektu mostowego wywołane statycznym obciążeniem próbnym są mniejsze niż te określone teoretycznie w modelu MES obiektu. W pierwszej kolejności zatem, wyniki pochodzące z rzeczywistych badań próbnego obciążenia zostały zestawione z ich teoretycznymi odpowiednikami, pochodzącymi z prostego modelu rusztowego mostu. Ten przykład ogranicza się do analizy maksymalnych ugięć jednego z dźwigarów głównych obiektu. Wykazano, iż ugięcia z pomiarów in-situ (pomierzone przemieszczenia zostały odpowiednio przeliczone na ugięcia, aby uwzględnić wpływ osiadania podpór i zgniotów łożysk) były mniejsze niż te określone teoretycznie. Nie było zatem podstaw do niedopuszczenia mostu do użytkowania ze względu na niespełnienie kryterium ugięć. Jednakże, w rezultacie analizy wykazano, iż wyniki odpowiedzi konstrukcji z prostego modelu deterministycznego różniły się znacznie od wyników pomiarów. W związku z tym, w celu opracowania procedury zwiększenia efektywności procesu przygotowywania probabilistycznych projektów próbnych obciążeń obiektów typowych, do dalszych analiz porównawczych i probabilistycznych wygenerowany został znacząco bardziej zaawansowany model bryłowy MES.

12

Finite beam element with 22 DOF for curved composite box girders considering torsion, distortion, and biaxial slip

Zhu Li, Wang Jia-Ji, Li Ming-Jie, Chen Chao, Wang Guang-Ming

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

16--34

EN

Experimental and numerical study on the mechanical performance of curved steel–concrete composite box girders is reported in this research. First, this research establishes a theoretical model for curved composite girders with 11° of freedoms (DOFs) for each node. The DOFs include the longitudinal displacement, transverse displacement, deflection, torsion angle, warping angle, and interface biaxial slip between steel and concrete. Based on the virtual work theorem, the equilibrium function, the stiffness matrix, the node displacement matrix and the external load matrix are proposed for the curved composite girders using the FE spatial discretization. Second, the authors conduct an experimental program on three large-scale curved composite girders with various interface shear connectors and central angles. The comparison between the developed finite beam element, the elaborate FE model and the test results indicates the developed finite beam element has an adequate level of accuracy in predicting the deflection, the torsion angle and the axial strain distribution of test specimens. Third, based on the developed finite beam element model, the effect of initial curvature, number of diaphragms, and the interface connector stiffness on the curved composite girder is examined. The simulation results showed that the initial curvature significantly contributes to the displacement and stress of composite girders. Applying more diaphragms can notably reduce the distortion angle and distortion displacement. The interface shear connector stiffness has a significant influence on the curved composite girder. With the increasing shear connector stiffness, the displacement and stress of curved composite girders decrease notably. Based on the parametric analyses, it is recommended to limit the central angle of simply supported composite girder below 45°, to apply an adequate number of diaphragms, and to design curved composite girders as fully shear connection specimens.

13

Patient-specific finite element analysis of frictional behavior in different esophageal regions during endoscopy

Lin Chengxiong, Ren Pan, Li Wei, Deng Hengyi, Zhou Zhongrong

Acta of Bioengineering and Biomechanics

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2020

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Vol. 22, no. 2

11--24

EN

Endoscopy is a common and effective method to treat digestive system diseases. Not only can it detect the physiological state of the digestive tract, but also can conduct clinical operations. As a result, it’s of great significance to make clear the relationship between the clinical operation and the complications. Methods: Considering the difficulty in measuring the contact force and determining the stress distribution in real time during endoscopy, a specific-patient finite element model for the frictional behavior at the endoscope-esophagus interface was built in current study. By collecting the CT data of the patient, a 3D esophagus model was built and divided into three characteristic regions (narrow region, thoracic region and abdominal region) according to the physiological structure. Results: Results showed that the radius of the narrowest position was the dominant factor for the maximum von Mises stress when the endoscope passed through the narrow region. For abdominal region and thoracic region, with the increasing coefficient of friction (COF) and amplitude, the total force duo to frictional force (CFSM), frictional dissipation (FD), strain energy (SE) and maximum von Mises stress (Max) all increased correspondingly. Meanwhile, the region of stress concentration gradually approached the initial contact stage. Conclusions: The results can provide theoretical basis and technical support for clinical application and offer some suggestions for medical workers during endoscopy as well.

14

Investigation of crack resistance in epoxy/boron nitride nanotube nanocomposites based on multi-scale methodInvestigation of crack resistance in epoxy/boron nitride nanotube nanocomposites based on multi-scale method

Hemmatian Hossein, Zamani Mohammad Reza, Jam Jafar Eskandari

Journal of Theoretical and Applied Mechanics

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2019

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Vol. 57 nr 1

207--219

EN

Boron nitride nanotubes (BNNTs) possess superior mechanical, thermal and electrical properties and are also suitable for biocomposites. These properties make them a favorable reinforcement for nanocomposites. Since experimental studies on nanocomposites are timeconsuming, costly, and require accurate implementation, finite element analysis is used for nanocomposite modeling. In this work, a representative volume element (RVE) of epoxy/BNNT nanocomposites based on multi-scale modeling is considered. The bonds of BNNT are modeled by 3D beam elements. Also non-linear spring elements are employed to simulate the van der Waals bonds between the nanotube and matrix based on the Lennard- -Jones potential. Young’s and shear modulus of BNNTs are in ranges of 1.039-1.041 TPa and 0.44-0.52 TPa, respectively. Three fracture modes (opening, shearing, and tearing) have been simulated and stress intensity factors have been determined for a pure matrix and nanocomposite by J integral. Numerical results indicate that by incorporation of BNNT in the epoxy matrix, stress intensity factors of three modes decrease. Also, by increasing the chirality of BNNT, crack resistance of shearing and tearing modes are enhanced, and stress intensity factor of opening mode reduced. BNNTs bridge the crack surface and prevent crack propagation.

15

Studying the Flexural Behavior of Reinforced Concrete Beams under the Effect of High Temperature: A Finite Element Model

Al-Baijat Hamadallah, Alhawamdeh Mohammad, Khawaldeh Aya

Advances in Science and Technology. Research Journal

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2019

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Vol. 13, no 2

150--156

EN

The strength of concrete elements can be greatly affected by elevated temperature as in fires, and so a great concern must be taken regarding its behavior under such condition. In this paper, a finite element model was built up using ABAQUS software to investigate the flexural behavior of reinforced concrete (RC) beams subjected to service load under elevated temperature. The beam was simply supported and was loaded at one-third and two-third of span length. The study consisted of three RC beams models; the first model simulated a control beam specimen at ambient temperature 20 °C, while the other two models demonstrated damaged beams specimens according to two high temperatures 400 °C and 800 °C, respectively. Each RC beam had 2 m span length, 300 mm height and 200 mm width. The steel reinforcement configuration was 3ϕ16 mm (Grade 60) main bars at the positive moment region in the beam bottom, 2ϕ14 mm (Grade 60) secondary bars at the beam top, and ϕ10 mm /150 mm closed stirrups. The model was validated by comparing its results with the theoretical results from ACI code and literature. Several mechanical properties were investigated including concrete compressive strength, modulus of elasticity, and reinforcing steel yielding strength. The test results showed a reduction in the flexural capacity of the RC beams, tested at 400 °C and 800 °C, of 17.6% and 88.2%, respectively, with respect to the control beam. The maximum service load carried by the beam, at one-third and two-third of the span length, decreased by 17.1% and 88.1% for the 400 ℃ and 800 ℃ high temperature, respectively. The results also showed an increase in deflection when the temperature increased due to the loss in stiffness.

16

Prototyping an MR damper system

Trębacz P.

Przegląd Elektrotechniczny

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2018

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R. 94, nr 11

149--154

EN

Magnetorheological (MR) shock absorbers are semi-active devices based on smart fluids. The fluid when exposed to magnetic field undergoes a transition from a liquid to a pseudo-solid. The change is reversible and fast and it has made the material attractive for use in semi-active real-time systems for vibration reduction. At the same time designing a shock absorber is a complex process due to the multi-physics involved. In this paper the author shows an approach that can be used for virtual prototyping studies of MR flow-mode devices. Magnetostatic calculations are followed by time-harmonics analyses of the circuit of the valve. The analysis is then complemented by a parametric study of the controller-damper system subjected to regulated (commanded) current step inputs using a lumped parameter model of the MR valve.

PL

Tłumiki magnetoreologiczne (MR) należą do grupy semi-aktywnych urządzeń wykorzystującyc tzw. ciecze inteligentne. Ciecz magnetoreologiczna jest zawiesiną cząstek ferromagnetycznych I nalezy do grupy materiałów o sterowalnych właściwościach reologicznych. Ciecz MR umieszczona w polu magnetycznym zmianie zmienia lepkość pozorną. Zmiana ta jest szybka i odwracalna, a końcowy stan materiału zależy od natężenia pola magnetycznego. Dzięki temu materiały te znalazły zastosowanie w semi-aktywnych układach redukcji drgań. Zaprojektowanie tłumika MR o odpowiednich osiągach jest jednak zadaniem złożonym. W niniejszym artykule autor przedstawia koncepcję budowy modelu systemu MR obejmującego tłumik i regulator PWM. Na wybranym przykładzie przedstawiono wyniki obliczeń polowych magnetostatycznych i harmonicznych obwodu tłumika. Wyniki obliczeń posłużyły m.in. do budowy modelu obwodu sterującego tłumika o parametrach skupionych z regulatorem.

17

Vibrational analysis of armchair phosphorene nanotubes by a DFT-based finite element model

Rouhi S., Shahnazari A., Ansari R.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 2

611--621

EN

A finite element model based upon the density functional theory is developed to investigate the vibrational characteristics of armchair phosphorene nanotubes. To this end, the PP bonds are simulated by beam elements whose elastic properties are obtained from the analogy of molecular and structural mechanics. The effects of nanotube length, diameter and boundary conditions on the frequencies of armchair phosphorene nanotubes are evaluated. It is shown that the effect of nanotube radius on its natural frequency is weakened by increasing the nanotube aspect ratio. Comparing the first ten frequencies of armchair phosphorene nanotubes with different diameters, it is observed that the effect of diameter on the vibrational behavior of phosphorene nanotubes is more pronounced at higher modes.

18

Formation mechanism and control methods of inhomogeneous deformation during hot rough rolling of aluminum alloy plate

Hao P., He A., Sun W.

Archives of Civil and Mechanical Engineering

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2018

|

Vol. 18, no. 1

245--255

EN

The inhomogeneous deformation which appears in hot rough rolling of aluminum alloy plate, reduces rolling output and negatively affects the rolling process. To study the formation mechanism of the inhomogeneous deformation, a finite element model for the five-pass hot rough rolling process of aluminum alloy plate is built. Results show that inhomogeneous deformation distribution in thickness direction causes two bulges at head and tail ends, as indicated by the analysis of the equivalent plastic strain distribution and deformation. However, formation mechanism of the inhomogeneous deformation at head end differs from that at tail end. Changing the end shape and angular rolling are adopted for decreasing the length and width of the crocodile mouth. It can be found that the crocodile mouth can be improved effectively by increasing the central bump length and the rotation angles through simulation and experiments. Then, the combination effect of two methods is simulated and results show that the combination effect is better than respectively using of each method. In addition, combination of two methods can avoid the restricted conditions for respectively using of each method.

19

A finite element model development as a part of process of energy absorption material selection

Jakubowski R., Skorupka Z.

Journal of KONES

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2016

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Vol. 23, No. 3

217--223

EN

The Warsaw Institute of Aviation major role in the RASTAS Spear project was to design an energy absorption system for the space probe lander. As the system was meant to be unmanned, the main requirement was to use no active solutions like parachute or rocket propulsion (less complexity in application and thus more reliability). A group of various materials was chosen to be tested. Tests campaign was divided into three stages: static compression tests, low speed dynamic tests and high speed dynamic tests. The high-speed dynamic tests were divided into two substages. In the first one simple cube specimens were tested to obtain data necessary for second substage in which full-scale object was tested. Having valuable data from experiments, numerical simulations in LS-DYNA software were carried out and then the results were compared. Based on experimental data several iterations during finite element model developing process were made. That process allowed setting up properly simulation by changing and adjusting properties such: material models, contact types, element formulation and other important constants. The finite element simulation results showed a good correlation with experimental data. The knowledge gained from numerical model optimization in connection with experimental data allowed for creating faster and more accurate energy absorbing material selection methodology. This methodology was successfully used in subsequent projects in which Institute of Aviation took part and also can be used in other future applications.

20

Stability characteristics of single-walled boron nitride nanotubes

Ansari R., Rouhi S., Mirnezhad M., Aryayi M.

Archives of Civil and Mechanical Engineering

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2015

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Vol. 15, no. 1

162--170

EN

Boron nitride nanotubes, like carbon nanotubes, possess extraordinary mechanical properties. Herein, a three-dimensional finite element model is proposed in which the nanotubes are modeled using the principles of structural mechanics. To obtain the properties of this model, a linkage between the molecular mechanics and the density functional theory is constructed. The model is utilized to study the buckling behavior of single-walled boron nitride nanotubes with different geometries and boundary conditions. It is shown that at the same radius, longer nanotubes are less stable. However, for sufficiently long nanotubes the effect of side length decreases.