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In order to enhance the initial velocity and energy conversion efficiency of multi-stage synchronous induction coil launchers, the direction of coil energization for the drive coils is studied. There are typically two energization methods for multi-stage launching devices: (1) PP (Positive-Positive), where positive current is applied to all drive coils, and (2) PN (Positive-Negative), where currents in opposite directions are alternately applied to the drive coils. A finite element model of a four-stage coil launcher is established in ANSYS2022R2, and the acceleration effects of the armature under different inter-stage distances are analyzed for two energization methods. The study reveals that the PN configuration does not always result in higher armature velocities compared to the PP configuration under different inter-stage distances. The theoretical explanation is provided for the variations in the forces exerted by the previous and next drive coils on the armature during the acceleration process. It is found that the magnitude of the induced current in the previous and next drive coils during the launch process is influenced by the inter-stage distance, which in turn affects the electromagnetic thrust coupled with the armature. Thus, the method of determining the direction of current in the launching device coil is obtained. [ABSTRACT FROM AUTHOR]

In order to enhance the initial velocity and energy conversion efficiency of multi-stage synchronous induction coil launchers, the direction of coil energization for the drive coils is studied. There are typically two energization methods for multi-stage launching devices: (1) PP (Positive-Positive), where positive current is applied to all drive coils, and (2) PN (Positive-Negative), where currents in opposite directions are alternately applied to the drive coils. A finite element model of a four-stage coil launcher is established in ANSYS2022R2, and the acceleration effects of the armature under different inter-stage distances are analyzed for two energization methods. The study reveals that the PN configuration does not always result in higher armature velocities compared to the PP configuration under different inter-stage distances. The theoretical explanation is provided for the variations in the forces exerted by the previous and next drive coils on the armature during the acceleration process. It is found that the magnitude of the induced current in the previous and next drive coils during the launch process is influenced by the inter-stage distance, which in turn affects the electromagnetic thrust coupled with the armature. Thus, the method of determining the direction of current in the launching device coil is obtained.

The preservation of the cultural heritage is a current challenge for modern societies. Thus, it is important to analyse the structural behaviour of historical buildings in order to detect and prevent future damage. This paper analyses the historical settlements of the Giralda tower of the Cathedral of Seville. Currently, it has a tilt which might have been caused by a differential settlement. With this aim, a detailed characterisation of the foundation and its geotechnical model has been carried out. An accurate 3D Finite Elements Model (FEM) has been used to analyse the settlements, taking into account the different construction phases, the loads, the time of execution and consolidation between phases. Finally, the 3D FEM results have been compared with other previous works and the in-situ measurements of the verticality of the tower. Therefore, the authors have found that the tilt to the south-east direction has been caused by the thicker, soft strata under this corner, which has caused differential settlement in this direction. Moreover, it should be highlighted that a good agreement between the settlements of the model and its real top displacements has been obtained. [ABSTRACT FROM AUTHOR]

The use of nanomodified epoxy resins can potentially increase composites application to aeronautical structural components, thanks to the potential enhancement, in terms of physical and mechanical properties, when compared to the neat epoxy matrix. In this work, the effects of silica nanoparticles (NPs) on the fracture toughness and, consequently, the crack growth resistance of fiber‐reinforced polymers (FRPs) have been numerically investigated. The skin‐stringer debonding initiation and growth have been studied by a tailored innovative numerical procedure considering an aeronautical panel reinforced with a single T‐shape stringer, made of carbon fibers/epoxy resin material, and subjected to compressive load. An analytical model has been used to evaluate the Mode I fracture toughness value of the nanomodified resin, and the Virtual Crack Closure Technique methodology has been employed to assess the delamination growth in the frame of a Finite Elements (FE) analysis performed in the Ansys FE environment. Numerical results presenting the comparison between charged and neat configurations have been assessed to provide a first understanding of the influence of nanoparticles on the static delamination growth in geometrically complex composite structures. [ABSTRACT FROM AUTHOR]

It is a promising treatment strategy to use an induction heating system for pipe lining, which can void the low efficiency and difficult temperature control of the traditional flame and hot air heating. In this study, a novel finite element model of pipe scanning induction heating was established, and the reliability of the model was verified through experiments. In addition, through the Plackett-Burman design, the main factors affecting the temperature fluctuation at 5 mm of the lining layer are analyzed. Finally, based on the analysis results, the system parameters were optimized by response surface method and the parameter configuration of the induction heating system with the minimum temperature fluctuation of 5 mm lining layer was obtained. The model established in this paper greatly reduces the calculation time of the electromagnetic induction heating finite element model of the moving magnetic field. It can be applied to the temperature information prediction of the lining induction heating where high-temperature accuracy is required and provides a reference for the characterization of the lining induction heating system and its application in low-temperature heat treatment, and the modeling strategy can be extended to the characterization of the temperature field evolution of any mobile heat source.

The application of edible coating in bakery products could be a suitable alternative to maintain safety, textural and organoleptic characteristics during the storage. To achieve a continuous coating layer, the coating solvent should be eliminated by a drying process, avoiding the food internal dehydration. The main factors that influence the drying time of the coating are the temperature, thickness of the coating and the solvent concentration. In order to define the optimal drying time, numerical modelling could provide a suitable alternative to experimental techniques. In this study, finite elements models able to describe the heat and moisture transfer inside and on the surface of coated bun breads, as function of drying temperature, time and coating thickness were developed and validated. A good agreement was obtained between calculated and experimental data reporting RMSE of 0.05 and 0.04 kg water kg solid −1 for the samples dried at 25 and 60 °C, respectively. A relation between the optimal drying time, coating thickness and the drying temperature was determined (R2 = 0.981, 95% confidence bounds). The model could be used for other coating formulations and bakery products, simply by changing material properties and geometrical dimensions. • FEM was developed to study the drying of edible coating on sandwich breads. • The model describes the drying, varying the process conditions, coating and product properties. • Good agreement was obtained between numerical and experimental results. • Relations between drying time, temperature and coating thickness were determined. [ABSTRACT FROM AUTHOR]

Highlights • Numerical study for the characterization of cement paste-aggregates interface. • A cohesive zone model is calibrated using experimental tensile tests applied to a mortar composite. • Characterization of cohesive zone model parameters during hydration and leaching of the composite. • Initial damage at the interface between cement paste and aggregates induced by an imperfec contact area. Abstract The influence of an Interfacial Transition Zone on mechanical behavior of concrete has been established by many authors. Several experimental studies have highlighted the weak mechanical properties of Interfacial Transition Zone due mainly to higher porosity than other phases, or to the presence of initial damage at the interface between paste and aggregates. Thus, it is necessary to take this zone into account when modelling the mechanical behavior of concrete, particularly outside of the elastic domain. Various analytical or numerical methods have been proposed, and some of these replace the physical representation of an Interfacial Transition Zone, by an imperfect interface between paste and aggregates, and an adhesion model with specific mechanical properties. In this work a cohesive zone model coupling adhesion, friction and unilateral contact is applied to a finite element model of a cement paste-aggregate composite, designed to test interface mechanical properties. Cohesive zone model parameters are calibrated using an experimental study of the same composite, submitted to mechanical loading during hydration and leaching of cement paste. This numerical approach allows modelling of the mechanical behavior of a composite until the tensile strength is reached. Moreover evolution of cohesive zone model parameters during hydration and leaching, shows a partial adhesion on contact surfaces between cement paste and aggregate. This could explain initial interface damage. [ABSTRACT FROM AUTHOR]

The conditions for the operation of railway systems are closely related to the increase of the commercial demand; as a consequence, the performance of the structural elements of railways changes. The present paper focuses on a study of the structural behaviour of bolster-beams under commercial operation conditions of railway systems, specifically in the dynamic conditions generated in events of over-traction and over-braking on the vehicle running. The proposed work is constructed based on the following phases: (i) analysis of the kinematics of the vehicle; (ii) development of numerical models, a model based on the multibody theory, and a Finite Elements model; (iii) development of experimental field tests; and (iv) development of simulations for a detailed analysis of the structural behaviour for a study of the strain distribution in the main bolster-beam. This study is applied to a particular case of a railway system that provides commercial service to passengers.

The problems on traffic safety caused by a lateral wind acting on railway vehicles are known and have been studied in the scientific literature. It is also known that the train speed increases the risk of derailment or overturning of the vehicle in a strong lateral wind event, especially with light vehicles such as the high speed trains. Some of the actions taken by public institutions of several countries to maintain the safety during the train travel with strong winds are the reduction of the train operation speed, during the lateral wind event, and the installation of wind barriers in certain high-speed line sections. On the deck of a high pier viaduct, the expected lateral winds are stronger because of the distance between the deck and the ground. On the other hand, on these laterally flexible bridges, the deck movements, induced by the wind, can affect traffic safety aggravating the problem, particularly when the deck presents a large exposed surface area, or wind barriers are used to reduce the wind direct impact on the train. In this article, the efficiency of the simultaneous use of wind barriers and tuned mass dampers at the top of the bridge piers is studied numerically, with a non-linear dynamic interaction train-bridge-wind model, in order to avoid the reduction of the train speed because of traffic safety and passengers’ comfort when turbulent winds are acting. [ABSTRACT FROM AUTHOR]

The conditions for the operation of railway systems are closely related to the increase of the commercial demand; as a consequence, the performance of the structural elements of railways changes. The present paper focuses on a study of the structural behaviour of bolster-beams under commercial operation conditions of railway systems, specifically in the dynamic conditions generated in events of over-traction and over-braking on the vehicle running. The proposed work is constructed based on the following phases: (i) analysis of the kinematics of the vehicle; (ii) development of numerical models, a model based on the multibody theory, and a Finite Elements model; (iii) development of experimental field tests; and (iv) development of simulations for a detailed analysis of the structural behaviour for a study of the strain distribution in the main bolster-beam. This study is applied to a particular case of a railway system that provides commercial service to passengers. [ABSTRACT FROM AUTHOR]

The present work is aimed to simulate the Friction Stir Welding process as a three-dimensional thermally coupled viscoplastic flow. A Finite Element technique is employed, within the context of a general purpose FEM framework, to provide the temperature distributions and the patterns of plastic flow for the material involved in the welded joints. The computational tool presented here may be of great relevance for technologist seeking to set the process control variables, as they are intended to obtain suitable material properties that yield the adequate on service response of the structural components.

Groundwater flow and tritium transport model was performed for model domain of new NPP site in Lithuania using three-dimensional finite-element code FEFLOW 5.0 which allows modelling of groundwater flow and contaminant transport in a layered three-dimensional system. The goal of these estimations is to describe the tritium transport from hypothetical reactor of new NPP. The model was calibrated using monitoring data of water level. The results of this calculation will allow predicting the tritium transport from NPP's reactor. [ABSTRACT FROM AUTHOR]

Fretting is associated with the small amplitude relative oscillatory motion between two solid surfaces in contact. Fretting fatigue is a damage mechanism observed in a machine components subjected to fretting in tandem with fluctuating bulk stresses. This paper presents the results of an experimental investigation of the fretting fatigue behavior of AISI 4140 vs. Ti-6–4 in a cylinder-on-flat contact configuration, and a computational fatigue damage model of the same configuration. In the experimental investigation, a fretting test fixture was designed and developed which was coupled with an MTS machine to impose the fretting fatigue damage. Fretting fatigue experiments were conducted under completely ( R =−1) reversed axial stress amplitudes, a constant maximum Hertzian Pressure ( P h ) of 3 GPa and at a frequency of 5 Hz. The test rig was also used in a fretting wear configuration under gross slip conditions to determine coefficient of friction for the same contacting pair of materials. In the computational modeling, damage mechanics constitutive relations were incorporated in a finite element model to analytically investigate the fretting fatigue. Voronoi tessellation was used to account for the randomness of the material microstructure and its effects on the fatigue behavior. Material properties needed for the damage model were determined using the analytical solution for maximum fretting stress ( σ fretting ) at the trailing edge of the contact which is assumed to drive the fretting fatigue failure. The critical damage value for AISI 4140 was extracted using the method of variation of elasticity modulus. Fretting fatigue lives predicted from the analytical model show good agreement with the measured experimental results. [ABSTRACT FROM AUTHOR]

The Strategy on Radioactive Waste Management of Lithuania (Radioaktyviųjų… 2008) envisages evaluating the possibilities of disposal of spent nuclear fuel and long-lived radioactive waste from operation and decommissioning of Ignalina NPP in a deep geological repository. The crystalline basement and sedimentary cover of south-eastern Lithuania was selected for the current model case studies due to availability of geological and hydrogeological data from previous explorations. Groundwater flow, radionuclide (iodine-129 as mobile and long-lived one) transport and heat transfer, modelling using computer code FEFLOW was performed. The model domain of south-eastern Lithuania comprises Protero-zoic-Archaean aquifer with overlaying aquifers system of sedimentary cover. The upward groundwater flow through defected canister located in tectonically damaged zone was conservatively generated. The main results of calculations are following: in case of upward groundwater flow, the maximum activity concentration of 129I in groundwater of the tectonic fracture zone above defected canister will not exceed 10−4 Bq/l; the maximum temperature in the tectonic fracture will obtain about 30-35°C and will not impact on the radionuclide transport. Location of model domain in south-eastern Lithuania does not mean any reference to the site for deep geological repository. The results show that doses obtained by human via drinking water should be below the dose constraint (0.2 mSv /year). Santrauka Radioaktyviųjų atliekų tvarkymo strategija numato galimybę panaudotą branduolinį kurą ir kitas ilgaamžes radioak- tyviąsias atliekas, susidariusias eksploatuojant Ignalinos AE ir susidarysiančias ją demontuojant, galutinai patalpinti giliai geologinėse formacijose. Dėl didelio geologinės bei hidrogeologinės informacijos kiekio šiame darbe nagrinėti tik Pietryčių Lietuvos kristalinis pamatas bei jį dengiantys nuosėdinių uolienų sluoksniai. Radionuklidų bei šilumos sklaidai kristalinio pamato uolienose vertinti naudota kompiuterinė programa FEFLOW 5.0. Pasirinkta konteinerio defekto scenarijus, taikant skaičiavimus, atliktus LEI ekspertų. Modelis apima archėjaus ir proterozojaus vandeningąjį sluoksnį bei nuosėdinėje dangoje slūgsančius vandeninguosius kompleksus. Modeliuotas požeminio vandens srautas, kylantis per tektoniškai pažeistą zoną, kurioje palaidotas PBK konteineris. Iš pagrindinių modeliavimo rezultatų nustatyta, kad ilgaamžio ir mažai sorbuojamo radionuklido 129I sklaidos intensyvumas mažai priklauso nuo geologinės aplinkos savybių, o šilumos sklaida neturi įtakos radionuklidų sklaidai. Žmogaus gaunama dozė, skaičiavimų duomenimis, nesieks ribinės vertės (0,2 mSv/metai). Reikšminiai žodžiai: panaudotas branduolinis kuras, geologinis atliekynas, kristalinis pamatas, požeminis vanduo, baigtiniai elementai

ABSTRACT Linear solar concentrators focus radiation onto the solar cell achieving a Gaussian illumination profile. Most of these concentrators use an active cooling system to evacuate the energy not converted into electricity to avoid undesirable overheating. Heat sinks can cause different temperature profiles in the cell depending on the cooling mechanism. Two temperature patterns are most common: the Gaussian and the anti-Gaussian. The effect of these temperature curves on the cell's electrical parameters has been analysed and characterised numerically and experimentally under different concentrated radiations. A power output increase is shown when the cell is subjected to a Gaussian temperature profile. Contrarily, the cell efficiency decreases more than 3% under the anti-Gaussian temperature profile. It is demonstrated that it is possible to tailor the temperature profile to maximise voltage output for determined illumination conditions. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper proposes an analytical tool that supports the design process of a disc-spring valve system used in hydraulic dampers. Such a valve is representative of a broader family of valve systems used in many industrial applications. The tool will speed up the valve-system design process.The paper considers a valve system that combines a number of circular metal plates, referred to further in the paper as ‘a stack of plates’. The proposed analytical tool obtains a key design characteristic of a valve, the flow rate, and the corresponding maximum stress level in the stack of plates as a function of pressure load. The stress level enables the ranking of valve settings in terms of durability. The calculation process is based on the response of a nonlinear, data-driven model that approximates the a priori simulated cases to cover the complete range of input design parameters, namely the number of plates, their thickness and their diameter. The cases are produced by a first-principle model using a Finite Element (FE) approach. The model was calibrated based on experimental results to provide accurate results in the entire range of input parameters. The advantage of the analytical tool is its ability to immediately provide the pressure-stress-flow characteristic of a valve instead of repeating time-consuming calculations for each new setting of input parameters. The objectives of the paper are as follows: to (a) adapt the model to a three-plate stack by applying large strain theory, (b) select and rank the Artificial Neural Networks used in order to approximate simulation data, and (c) demonstrate validation and application results obtained with the Approximation Tool. [ABSTRACT FROM AUTHOR]

The finite elements method is used to calculate the output EMF curve of a synchronous tachogenerator. A rotor tooth pattern was optimized in order to significantly decrease the level of higher harmonics in the output EMF of a tachogenerator. [ABSTRACT FROM AUTHOR]

The Strategy on Radioactive Waste Management of Lithuania (Radioaktyviųjų… 2008) envisages evaluating the possibilities of disposal of spent nuclear fuel and long-lived radioactive waste from operation and decommissioning of Ignalina NPP in a deep geological repository. The crystalline basement and sedimentary cover of south-eastern Lithuania was selected for the current model case studies due to availability of geological and hydrogeological data from previous explorations. Groundwater flow, radionuclide (iodine-129 as mobile and long-lived one) transport and heat transfer, modelling using computer code FEFLOW was performed. The model domain of south-eastern Lithuania comprises Protero-zoic-Archaean aquifer with overlaying aquifers system of sedimentary cover. The upward groundwater flow through defected canister located in tectonically damaged zone was conservatively generated. The main results of calculations are following: in case of upward groundwater flow, the maximum activity concentration of 129I in groundwater of the tectonic fracture zone above defected canister will not exceed 10−4 Bq/l; the maximum temperature in the tectonic fracture will obtain about 30-35°C and will not impact on the radionuclide transport. Location of model domain in south-eastern Lithuania does not mean any reference to the site for deep geological repository. The results show that doses obtained by human via drinking water should be below the dose constraint (0.2 mSv /year). [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work is to show the effects in a PV cell of the combined profiles of non-uniform temperature and radiation. Particular attention is paid to the modelling of cell operation at open circuit voltage with those profiles, as long as they serve as a general model in different circumstances: combined direct Gaussian temperature and radiation profiles, with several temperature amplitudes and movement of these profiles across the cell; analysis under Gaussian concentrated illumination and inverse Gaussian temperature profile simulating a general cell cooling device. In addition, we will study the cell behaviour under truncated radiation and temperature profiles. Irregular radiation and temperature distributions will also be studied. [ABSTRACT FROM AUTHOR]

Abstract: A two-dimensional finite element model of current flow in the front surface of a PV cell is presented. In order to validate this model we perform an experimental test. Later, particular attention is paid to the effects of non-uniform illumination in the finger direction which is typical in a linear concentrator system. Fill factor, open circuit voltage and efficiency are shown to decrease with increasing degree of non-uniform illumination. It is shown that these detrimental effects can be mitigated significantly by reoptimization of the number of front surface metallization fingers to suit the degree of non-uniformity. The behavior of current flow in the front surface of a cell operating at open circuit voltage under non-uniform illumination is discussed in detail. [Copyright &y& Elsevier]

In this paper, the weight functions for deep and superficial points of semi elliptical crack, situated in pipes internal surface are achieved Coefficients of tension intensity are introduced into closed solution, using the achieved weight functions for two parabolic pressure loading position on the crack surface and pipe with internal pressure. In order to modeling the linear semi elliptical crack situated in internal surface of thin-walled pipe, three-dimensional finite elements method has been used. The weight function for deep and corner points of semi elliptical crack has been achieved. For computing the coefficients of tension intensity quantities we have used the extrapolate displacement method Results have been compared with the finite element method, which show good results. [ABSTRACT FROM AUTHOR]

This article describes and solves a mathematical model useful to study a vehicle's kinematics before and after collision, and the structure behaviour during an impact. The algorithm is based on solving differential equations using Runge-Kutta numerical method. To extract input data, a full-scale numerical model is solved using LS-Dyna. The friction coefficient between vehicle and barrier is evaluated and compared with the input value. The motion of the vehicle is solved and then passengers are added. The acceleration and displacement of the passenger's centre of gravity are computed for different cases of impact angle and safety restrain system's stiffness. To extend the capabilities for accident-reconstruction applications, a procedure to construct deformation force pulse is presented. Also, a method for the evaluation of vehicle's kinematic parameters using force-deformation curve is presented. The performances of the open architecture of the analytical model are presented and applied for the study of passenger's head motion. [ABSTRACT FROM AUTHOR]

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Monitoring and managing small coastal ecosystems requires a considerable understanding of the temporal dynamics of biophysical factors describing the coastal water systems. For this reason, daily observation from space could be a very efficient tool. The objective of the work described in this paper is to evaluate the contribution of remote sensing to the continuous monitoring of coastal areas. It is well known that in coastal areas, the presence of inorganic suspended sediments and coloured dissolved organic matter can make chlorophyll-concentration measurements from remote sensing difficult. To overcome these difficulties, an alternative approach to the SeaWiFS standard chlorophyll algorithm is presented, based on a semi-analytic model for sea water and on the use of MODIS data as input in a model for atmospheric effects removal. Moreover, land contamination (mixed sea­land pixels) can introduce ambiguities in sea-surface temperature measurements from remote sensing. This paper proposes the use of a hydrodynamic model as a time­space interpolator of in situ campaign data, to extensively validate the temperature values extracted from AVHRR sensor. We validated the proposed approach, using experimental field data collected over a two-year campaign in the Taranto Gulf. The results seem to indicate a good agreement between remote-sensed and in situ data. [ABSTRACT FROM AUTHOR]

The low frequency broadband vibrational behavior of a piano soundboard is considered. Attention is focused on the ability of finite element models and analytical models to predict precisely the behavior of such a complicated structure—especially with its orthotropy and rib effects. In order to validate these abilities, an experimental modal analysis, considered as the reference, is compared first with a numerical calculation and then with an analytical modeling of the modal basis of the same soundboard. The high structural complexity of the soundboard exceeds the analytical capabilities, but agreement is very good for the numerical model, in the frequency domain, and equally in the spatial one. The final aim is to generate a numerical tool for designing and optimizing piano soundboards. [Copyright &y& Elsevier]