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In this paper, a finite element procedure is used to study the dynamic behaviour of a paper web in a free span between two rollers, including effects of transport velocity and surrounding air. The paper web is modelled as a three-dimensional orthotropic structure. The influence of air is accounted for by utilizing fluid–solid interaction analyses based on acoustic theory. The contribution of transport velocity is included through gyroscopic matrices and forces. The structural response on harmonic excitations has been studied using linear and non-linear models. Results show that air significantly reduces eigenfrequencies of the web. So called “edge-flutter” is nothing but the result of skew tension profile. Excessive web vibration can be eliminated by adjusting the web tension. [Copyright &y& Elsevier]

Abstract: In this paper we describe electrophoresis of charged particles in a thin layer of a nonpolar liquid between two insulating substrates because this configuration is common in recently developed in-plane electronic paper. In the in-plane electrophoresis experiments a model system of charged inverse micelles in dodecane has been used which is well understood from studies of out-of-plane electrophoresis. The transient current due to drift and diffusion of charged inverse micelles is measured in thin in-plane devices upon application of a voltage step. For the modelling of the transient dynamics of charged inverse micelles without chemical reactions or convection a 1-dimensional approximation of the Poisson–Nernst–Planck (PNP) equations is developed. This approximation is valid for a sufficiently thin in-plane device and allows much faster calculations. Firstly, it is verified in the case of a sufficiently thin in-plane device and high applied voltage that the 1-dimensional approximation is in good agreement with the solution of the full 2-dimensional PNP equations with finite elements implementation. Then, the 1-dimensional approximation is used to study the transient current and trajectories of trace amounts of charged colloidal particles in different regimes depending on the screening of the electric field. Also a comparison is made to the well-studied case of out-of-plane electrophoresis. Finally, it is verified that for voltages much larger than the thermal voltage the experimental results are in good agreement with the 1-dimensional approximation, indicating that the charge transport dynamics of charged inverse micelles in the bulk are described well by the model. [Copyright &y& Elsevier]

This paper presents a quasistatic problem of an elastic body in frictional contact with a moving foundation. The model takes into account wear of the contact surface of the body caused by the friction. We recall existence and uniqueness results obtained in Sofonea et al. (2017). The main aim of this paper is to present a fully discrete scheme for numerical approximation together with an error estimation of a solution to this problem. Finally, computational simulations are performed to illustrate the mathematical model. [ABSTRACT FROM AUTHOR]

Highlights • The mathematical model of corrugated shells with special shapes is presented. • Effect of corrugation parameters on critical load is investigated. • Linear and nonlinear buckling analyses are conducted. • Critical load of corrugated shells is compared to smooth ones. • Specific range of corrugation parameters significantly increase the value of relative critical load. Abstract The problem of elastic stability of the shells with special shapes with corrugated middle surfaces under external pressure is debated in the presented paper. Solution of the problem is based on FEM study. Corrugated barrelled, pseudo-barrelled, and cylindrical shells of constant mass are considered. Geometrical modification of the middle surface geometry is based on sine wave along principal directions. Middle surface of the corrugated shells are described referring to differential geometry of surfaces by parametric functions in three-dimensional Euclidean space. Linear and nonlinear buckling analyses are conducted. Examples of buckling modes are presented, which differ significantly from those typical for shells of revolution with positive or zero Gaussian curvature. It is proven that corrugation may lead to serious increase or decrease of critical load for all types of presented shells. [ABSTRACT FROM AUTHOR]

Abstract A coupled finite particle method (FPM) is proposed to model wave-structure interaction. The coupled FPM combines the advantages of FPM, smoothed particle hydrodynamics (SPH), δ -SPH model and particle shifting technology (PST). The coupled FPM is more accurate than SPH for evaluating the interior fluid particles and more flexible than FPM for evaluating the free surface. The density diffusive term of δ -SPH model can allow for a relatively large CFL condition number and maintain a high computational efficiency. With the help of PST, the particle clustering and fracturing are eliminated effectively, and the well-conditioned corrective matrix is acquired. The coupled FPM method is tested by simulations of regular waves and the interaction between waves and the rigid plate. Then, the coupled FPM method is applied to model Oscillating Wave Surge Converter (OWSC) including two-dimensional (2-D) and three dimensional (3-D) simulations. All numerical results show that the coupled FPM is robust, and is capable to simulate wave-structure interaction accurately. The linked data are be associated to this paper, and the readers are able to download the source code that can be used to test regular waves contained in the paper. The web site of the code is https://data.mendeley.com/datasets/xjk3ccgr8t/draft?a=622fb107-3cb9-4c68-af8e-7b3ac1b3fc48. Highlights • The coupled FPM is proposed to model wave and structure interaction. • A 3-D geometry model is improved to detect the particles in the vicinity of free surface. • The coupled FPM method is developed to model Oscillating Wave Surge Converter (OWSC) including 2-D and 3-D results. [ABSTRACT FROM AUTHOR]

Abstract Spacecraft are subjected to severe mechanical loads, especially during the ascent phase of the launch. Among several vibrational environments, shock loads, which are caused mainly by the activation of pyrotechnic devices used for the separation of the payloads and the different stages of the launcher, are transmitted throughout the entire structure and reach the scientific instruments of the spacecraft. Therefore, it is important to verify if the space instruments can withstand this environment, considering the nature of the shock, which generally consists in an intensive and short load. In recent years, the demand of numerical analyses to predict the responses of the structures against shocks is increasing and, for this reason, it is necessary to establish adequate numerical methods, taking into account the complex mathematical treatment and the uncertainty in the load characterization. The purpose of this paper is to present the application of different methods to calculate the required structural results for a space instrument subjected to the shock environments using a finite element model (FEM). The procedures for each method, the type of the results that can be calculated and the comparison of the results are described in this paper. The objective is to select the most suitable analysis method for shock loads based on the precision of the results and the capability of obtaining all the variety of data for a complete evaluation of the structure. [ABSTRACT FROM AUTHOR]

In this paper, we are interested in the displacement of two incompressible phases in a Darcy–Brinkman flow in a porous media. The equations are obtained by the conservation of the mass and by considering the Brinkman regularization velocity of each phase. This model is treated in its general form with the whole nonlinear terms. This paper deals with construction and convergence analysis of a combined finite volume–nonconforming finite element scheme together with a phase-by-phase upstream according to the total velocity. [ABSTRACT FROM AUTHOR]

The nef cone volume appeared first in work of Peyre in a number-theoretic context on Fano varieties, and was then studied by Derenthal and co-authors in a series of papers on del Pezzo surfaces. The idea was subsequently extended to also measure the Zariski chambers of del Pezzo surfaces. We start in this paper to explore the possibility to use this attractive concept to effectively measure the size of the nef cone on algebraic surfaces in general. This provides an interesting way of measuring in how big a space an ample line bundle can be moved without destroying its positivity. We give here complete results for simple abelian surfaces that admit a principal polarization and for products of elliptic curves. [ABSTRACT FROM AUTHOR]

The frictional receding contact problem for two graded layers pressed by a rigid punch is considered in this paper. The punch is subjected to both normal and tangential loads thereby resulting in frictional contact with the upper layer. It is also assumed that the contact between the layers is frictional and the lower layer is fixed. It is further assumed that the gradation in the layers follows an exponential variation through the thickness with different profiles while Poissons ratios are taken as constants. Using standard Fourier transform, the contact problem is converted to a system of two singular integral equations in which the contact pressures and the contact widths are the unknowns. The integral equations are then solved numerically using Gauss–Jacobi integration formula. The Finite Element Method was additionally employed and both exponential and power law material gradation is used to solve the investigated problem and the obtained numerical and analytical results are in good agreement. The primary intention of this paper is to investigate the effect of material gradation, friction coefficients, layers thicknesses and material property mismatch at the interface between the layers on the contact pressures and contact widths. [ABSTRACT FROM AUTHOR]

Incremental bulk deformation processes have traditionally been difficult to simulate. This paper will argue that, despite advances in computation and software, they remain difficult to model. The main reason for this is the shortage of ideas on what is the real objective of FE modelling for such processes. Even a very detailed model and data obtained in simulation does not give answers to the main question - how to optimise the process parameters? High computational time and volume of information only aggravate the situation. All modern mathematical techniques of dimensionality reduction (such as POD/PGD) lose their power when the priorities and acceptable compromises of modelling are not clear. This paper tries to use a large volume of available experimental and modelling experience to illustrate this problem and look for possible break-through directions. [ABSTRACT FROM AUTHOR]

This paper presents a framework for nonlinear system identification of civil structures using sparsely measured dynamic output response of the structure. Using a sequential maximum likelihood estimation (MLE) approach, the unknown FE model parameters, the measurement noise variances, and the input ground acceleration time histories are estimated jointly. This approach requires the computation of FE response sensitivities with respect to the unknown FE model parameters (i.e., FE parameter sensitivities) as well as the FE response sensitivities with respect to the values of the input ground acceleration at every time step (i.e., FE input sensitivities). The FE parameter and input sensitivities are computed using the direct differentiation method (DDM). The presented output-only nonlinear FE model updating method is validated using the numerically simulated seismic response of a realistic three-dimensional five-story reinforced concrete building structure. The simulated building responses to a horizontal bi-directional seismic excitation is contaminated with artificial measurement noise and used to estimate the unknown FE model parameters characterizing the nonlinear material constitutive laws of the reinforced concrete, as well as the root mean square of the measurement noise at each measurement channel, and the full time history of the seismic base acceleration. The method presented in this paper provides a powerful framework for structural system and damage identification of civil structures, when the input excitations are not measured, are partially measured, or the measured input excitations are erroneous. [ABSTRACT FROM AUTHOR]

Numerical simulation of oil-water miscible displacement is discussed in this paper, and a compressible problem of energy mathematics is solved potentially. The mathematical model defined by a nonlinear system includes mainly two partial differential equations (PDEs): a parabolic equation for the pressure and a convection-diffusion equation for the saturation. The pressure is obtained by a conservative mixed finite volume element method (MFVE). The computational accuracy is improved for Darcy velocity. A conservative upwind mixed finite volume element method (UMFVE) is applied to compute the saturation on changing meshes. The diffusion is discretized by a mixed finite volume element method, and the convection is computed by upwind differences. The upwind method can solve convection-dominated diffusion equations accurately and avoids numerical dispersion and nonphysical oscillation. The saturation and the adjoint vector function are obtained simultaneously. An optimal order error estimates is obtained. Finally, numerical examples are provided to show the accuracy, efficiency and possible applications. [ABSTRACT FROM AUTHOR]

The numerical modelling of the internal heat generation in passenger vehicle tyres using finite element analysis is a well-known numerical approach. However, this application is rather uncommon for earthmover tyres. This paper describes the development of a finite element model of a 23.5R25 earthmover tyre for the numerical modelling of the temperature distribution in the tyre cross-section at steady-state heat transfer conditions using an uncoupled analysis procedure. Considering the non-linear behaviour of the rubber compounds used for the manufacturing of these tyres, as well as the complexity associated with the composite structural aspects of the tyre, the material properties used for the proposed numerical model were established experimentally. In the analyses completed, the tyre behaviour was studied by simulations at various inflation pressures, loads and rolling velocities. The numerical tyre defection was within an 8% deviation from the actual tyre behaviour. Thermal simulation results were used to derive an equation that can be used to predict the maximum temperature that would occur in the tyre’s cross-section as a function of its vertical deflection, its forward rolling velocity and the ambient temperature of the surroundings. The numerical models and simulations presented in this paper were completed using MSC.Marc/Mentat. [ABSTRACT FROM AUTHOR]

This paper deals with contact analysis of rolling bearings. A new mathematical model and numeric method are presented in this paper for the purpose of contact analysis of rolling bearings based on the principle of mathematical programming method. Three-dimensional (3D), finite element method (FEM) is introduced to calculate deformation influence coefficients and gaps of assumed pairs of contact points between the contact surfaces in the mathematical model. Special software is developed to realize numeric calculation procedures of the contact analysis. With the help of the developed software, loaded bearing contact analyses are conducted for a deep groove ball bearing and a cylindrical roller bearing. In the case of the ball bearing, it is found that calculated contact pressure on the ball surfaces is correct elliptical distribution (usually called contact ellipse). This result is more reasonable than the results obtained by commercial software SolidWorks and other researchers. In the case of the roller bearing, it is found that edge-loads (non-Hertz contact that cannot be analyzed with Hertz theory) on the roller surface are analyzed when the roller is not crowned. It is also found that the edge-loads disappear and contact pressure on the roller surface becomes uniform distribution when the roller is crowned with Johson-Gohar curve. Since the most important features (contact ellipse and edge-loads) of the bearing contacts are analyzed successfully by the developed software and these results cannot be obtained simply by general methods, the mathematical model and numeric method presented in this paper are of practical meaning in engineering design and the developed software can be used as a tool for contact strength and rigidity calculations of the rolling bearings. [ABSTRACT FROM AUTHOR]

In Jung and Roh (2017), we investigated some properties of approximate solutions of the second-order inhomogeneous linear differential equations. In this paper as an application of above paper we will study the stability of the time independent Schrödinger equation with a potential box of finite walls. [ABSTRACT FROM AUTHOR]

Simulating multi-body dynamics with both rigid and flexible parts and with frictional contacts is a hard problem. We solve this by expressing the couplings between the bodies as position level constraints. The implicit treatment of the constraint directions gives us improved stability over velocity based methods. Then by employing regularization of nonlinear constraints and a convex minimization formulation, we bridge constraint-based methods to traditional force-based methods. In fact, the former are just a dual variables formulation of the latter. We solve this dual problem using position based dynamics (PBD). We show how PBD is a completely valid modeling technique and we extend it with an accurate contact and Coulomb friction model. We further show for the first time how the same solver can be used to simulate both rigid and deformable solids with two way coupling. For the soft bodies we introduce a novel form of linear finite elements expressed as constraints, that is more accurate than PBD mass-spring systems. More of our results include the energy conserving Newmark integrator and the accelerated Jacobi solver suitable for parallel architectures. Note that this paper is an extended and revised version of the conference paper published in [1]. [ABSTRACT FROM AUTHOR]

A numerical investigation on cold-formed high strength steel (HSS) tubular beams is presented in this paper. The nominal 0.2% proof stresses of the HSS sections ranged from 700 MPa to 1100 MPa. In the complementary study [1], experimental investigation on the beam specimens have been performed. In the present study, numerical modelling methodology for beams was first validated and parametric study on the cold-formed HSS tubular beams was conducted. A total of 423 numerical data was obtained to investigate the structural performance of HSS tubular beams. The experimental and numerical results were then compared with the codified design guidelines from ANSI/AISC 360-10 [2], EN 1993-1-1 [3], AS 4100 [4] and AISI S100 [5] in addition to the predictions from Direct Strength Method (DSM) for square hollow sections (SHS), rectangular hollow sections (RHS) and circular hollow sections (CHS). The codified slenderness limits for sections subjected to bending were examined. Improvements on the design guidelines are proposed in this paper. [ABSTRACT FROM AUTHOR]

Material non-linearity of pier members is an important factor that needs to be considered for dynamic analysis of the bridge pier subjected to barge impact. However, many existing studies pertaining to barge impact on the bridge pier are based on the assumption that the pier is rigid or elastic. High-resolution finite-element simulation serves as the main strategy for dynamic analysis of the bridge pier subjected to barge impact considering material non-linearity of pier members. However, high-resolution finite-element simulations are expensive regarding both calculation time and computing resources, thus efficient models are often required. This paper develops the numerical model of the square RC pier column with fixed base. By coupling the simplified mass-spring model developed by the authors previously with the RC pier column at the impact position using fibre beam elements, the efficient model is developed to predict the impact force time-history and dynamic responses of the RC pier column subjected to barge impact. The studies in this paper show that the prediction quality of the proposed efficient model is adequate for different impact scenarios. [ABSTRACT FROM AUTHOR]

Pulsed water jets have been widely applied in the field of underground mining because of their unique advantages. Revealing the mechanical mechanism of rock breaking under a pulsed water jet is significant in advancing the application of pulsed water jets in the rock crushing process. Based on continuum mechanics and interpolation theory, this paper establishes a numerical model to simulate the propagation of stress waves in rock by adopting the method of smooth particle hydrodynamics (SPH). According to the simulation results, this paper presents a quantitative approach to schematize the propagation of stress waves in the time-space dimension. The waveforms of stress waves in the selected path and the effective stress history of test particles are obtained to quantitatively describe the propagation of stress waves. Relying on the approach, the effects of jet velocity and rock properties on the propagation of stress waves are investigated. The results show that in the rock model, the influence area, propagation speed and attenuation rate of the stress wave all increase with increasing jet velocity. Moreover, the mean effective stress of a test particle in the numerical model increases with increasing jet velocity. Of the rocks considered in this paper, granite shows the greatest mean effective stress acting on the test particle, propagation speed, and attenuation rate of the stress wave. [ABSTRACT FROM AUTHOR]

This paper presents a study on the metal cutting simulation with a particular numerical technique, the Particle Finite Element Method (PFEM) with a new modified time integration algorithm and incorporating a contact algorithm capability . The goal is to reproduce the formation of continuous chip in orthogonal machining. The paper tells how metal cutting processes can be modelled with the PFEM and which new tools have been developed to provide the proper capabilities for a successful modelling. The developed method allows for the treatment of large deformations and heat conduction, workpiece-tool contact including friction effects as well as the full thermo-mechanical coupling for contact. The difficulties associated with the distortion of the mesh in areas with high deformation are solved introducing new improvements in the continuous Delaunay triangulation of the particles. The employment of adaptative insertion and removal of particles at every new updated configuration improves the mesh quality allowing for resolution of finer-scale features of the solution. The performance of the method is studied with a set of different two-dimensional tests of orthogonal machining. The examples consider, from the most simple case to the most complex case, different assumptions for the cutting conditions and different material properties. The results have been compared with experimental tests showing a good competitiveness of the PFEM in comparison with other available simulation tools. [ABSTRACT FROM AUTHOR]

This paper presents a two-dimensional numerical (2D) model for analysing the full three-dimensional (3D) problem of heat transport problems in laminated composite plates. A 2D finite element model is enough for good representation of a 3D problem since each single node in the mesh has enough degrees of freedom associated with particular layers of the laminated plate. The 2D numerical model is quite simple and effective and it allows considering multi-layered structures in which individual layers are made of different materials and the structure may consist of a combination of thick and very thin layers without numerical instabilities. The method presented in this paper is combined with a specially tailored postprocessing procedure so that results from the planar mesh can be visualised as 3D graphics. The paper is illustrated with a set of examples in which stationary and non-stationary problems are considered. In these examples modelling of the laminated glass with three glass panes and thin layers of bonding material is presented. [ABSTRACT FROM AUTHOR]

Abstract: Finite element analysis of ink-tack delamination of paperboard were presented. The paperboard was modeled as a multilayered structure with a softening interface model connecting the paperboard plies. The paperboard plies were modeled as orthotropic linear elastic. The ink-tack loading was applied to the board in the form of a moving displacement boundary condition. The purpose of the analysis was to assess the influence from the elastic moduli of the individual layers on the ink-tack delamination event. The results indicated that in most cases of practical interest the board delaminated between the outer plies of the board, although the interface strength was lower in the middle of the board. This observation helped to explain why traditional tests for out-of-plane testing of paper by standardized methods could not uniquely predict the propensity for ink-tack delamination. [Copyright &y& Elsevier]

This paper focuses on coupling two different computational approaches, namely finite element method (FEM) and meshless finite difference method (MFDM), in one domain. The coupled approach is applied in solving thermomechanical initial–boundary value problem where the heat transport in the domain is non-stationary. In this method, the domain is divided into two subdomains for FEM and MFDM, respectively. Contrary to other coupling techniques, the approach presented in this paper is defined in terms of mathematical problem formulation rather than at the approximation level. In the weak form of thermomechanical initial–boundary value problem (variational principle), the appropriate additional coupling integrals are defined a-priori. Subsequently, the FEM and the MFDM approximations, which may differ from each other, are provided to the formulation. It is assumed that there exists a very thin layer of material between the subdomains, which is not spatially discretized. The width of this layer may be considered the coupling parameter and it is the same for both, thermal and mechanical parts. Similar approach is applied to essential boundary conditions (e.g. prescribed temperature and displacements). Consequently, the consistent formulation of the mixed problem for the coupled FEM–MFDM method is derived. The analysis is illustrated with two- and three-dimensional examples of mechanical and thermomechanical problems. [ABSTRACT FROM AUTHOR]

This paper describes iterative methods for the high frequency electromagnetic analysis using the finite element method of Maxwell equations including displacement current. The conjugate orthogonal conjugate gradient method has been widely used to solve a complex symmetric system. However, the conventional method suffers from oscillating convergence histories in large-scale analysis. In this paper, to solve large-scale complex symmetric systems arising from the formulation of the E method, an iterative substructuring method like the minimal residual method is presented, and the performance of the convergence of the method is evaluated by numerical results. As the result, the proposed method shows a stable convergence behavior and a fast convergence rate compared to other iterative methods. [ABSTRACT FROM AUTHOR]

Crowd induced dynamic loading in large structures, such as gymnasiums or stadiums, is usually modelled as a series of harmonic loads which are defined in terms of their Fourier coefficients. Different values of these Fourier coefficients that were obtained from full scale measurements can be found in codes. Recently, an alternative has been proposed, based on random generation of load time histories that take into account phase lags among individuals inside the crowd. This paper presents the results of some studies carried out in order to compare the existing load models used to simulate periodic jumpings and develop a new load model. Generally the testing is performed on platforms or structures that can be considered rigid because their natural frequencies are higher than the excitation frequencies associated with crowd loading. But in this paper, to validate these load models test have been performed on a structure designed to be a gymnasium, which has natural frequencies within that range. Test results have been compared with predictions based on the load modelling alternatives with quite good agreement. A calibrated finite element model of the structure has been used for this purpose. The new model provides a clear improvement in the energy contained within higher frequencies. [ABSTRACT FROM AUTHOR]

The ultimate strength of hollowcore slabs is greatly affected by their post-cracking behaviour. The composite action between the concrete topping and the hollowcore slab adds another level of nonlinearity. This paper presents a comprehensive finite element study to evaluate the nonlinear properties of the interface between a hollowcore slab and its concrete topping. The presented finite element modeling procedure was validated using data from a previous comprehensive experimental study by the authors. The nonlinear material behaviour of the concrete and the prestressing strands were also accounted for. The paper presents a modeling method that realistically simulates the staged construction technique of composite hollowcore slabs. Finite element results allowed understanding changes to the interface properties due to the confining effect of the applied load as well as the interaction between the shear and peel stresses. [ABSTRACT FROM AUTHOR]

The aim of the present paper is to provide an efficient numerical technique to evaluate the linear elastic stress parameters to use in an existing fatigue model. The model allows to assess the tensile fatigue limit of components weakened by defects, cracks, sharp as well as blunt notches with an arbitrary notch opening angle. To apply the fatigue model, both the elastic stress concentration factor of the notch and the notch stress intensity factor of the corresponding sharp notch must be evaluated. Therefore, in principle two different linear elastic stress analyses should be performed. The novel technique proposed in the present paper involves only a single linear elastic stress analysis, consisting of a sharp and coarse finite element model: sharp because the notch tip radius is set to zero, and therefore a sharp V-shaped notch is modelled; coarse because coarse patterns of finite elements can be employed. Approximate values of the elastic stress concentration factor and of the notch stress intensity factor calculated from the sharp and coarse finite element model are compared with very accurate estimations obtained from dedicated analyses. To illustrate the fatigue assessment procedure, experimental notch fatigue limits taken from the literature and characterised by a variety of geometrical configurations are compared with theoretical estimations. [ABSTRACT FROM AUTHOR]

The present work focuses on a new numerical model for the fully coupled hydro-mechanical analysis of groundwater flows through poroelastic saturated media. In particular, the presence and eventual propagation of fluid-driven fractures is accounted for within a non-regularized cohesive zone model. In this paper, the fracture propagation is considered as a reactivation process: the fracture already exists and evolves ( i.e. opens or closes) on a pre-defined path initially constrained. The Talon-Curnier constitutive law is considered for the fracture interfaces and its expression has been adapted to the hydro-mechanical coupling related to the fracture evolution. The fluid pressure inside the fracture is governed by the lubrication equation. The momentum-stress balance equations involving fluid flow and deformation of the solid porous matrix are derived within the framework of the generalized Biot theory. The extended finite element method (XFEM) is preferred to a standard finite element spatial discretization in order to easily handle the presence and evolution of discontinuities in the porous medium. A set of four Lagrange multipliers is introduced to prevent spurious oscillations of the numerical solution at the interface. Comparisons between numerical results and theoretical solution assess the validity of the model presented in this paper. In addition, the hydro-mechanical interactions between neighboring fractures and the effects of the permeability of the porous medium are investigated. We also demonstrate the capability of our model to handle non-planar fracture paths. [ABSTRACT FROM AUTHOR]

In modern utility boilers, characterized by high values of steam pressure and temperature, the individual superheater stages and also the individual passes are made of different low alloy steel grades. The use of tubes having a complex shape of cross section allows the building of the platen with smooth side surfaces, which are arranged in the upper part of the combustion chamber. This avoids the erosion of the superheater tubes and deposition of slag and ash in the spaces between adjacent tubes. The superheaters of this type are widely used in CFB boilers. To select the appropriate steel for each pass and each stage, the maximum wall temperature of tube need to be determined. Steam and tube wall temperature were computed in the superheater using a method proposed in the paper and compared with the results obtained by CFD simulation using Star-CCM+ software. The method presented in the paper can be easily applied to the modeling of flow and thermal processes in superheaters with complicated flow arrangements which usually are found in steam boilers. The advantage of the proposed method is a short computing time in comparison with detailed and complex 3D models. Using the methodology developed in the article, time needed to obtain final results at steady-state conditions can be lower even dozen times in comparison to CFD calculations. The proposed calculation method can be used in the design of modern subcritical and supercritical boilers, in which the temperature of the live steam is very high. Very careful and precise calculations of steam and tube walls temperature along the steam flow path will avoid the overheating of the tube material. [ABSTRACT FROM AUTHOR]

Double-skin composite (DSC) panels can offer high strength and robustness while improving the convenience of construction, with great potential for application in high rise buildings and nuclear power plants. In DSC panels, the stability of the outer surface steel plates are governed by the constraints of the in-fill concrete and the discrete shear connectors, i.e., the ratio of connector spacing ( B ) and surface steel plate thickness ( t ). In this paper, tests were performed on 10 specimens to assess the buckling behavior of DSC panels. The arrangement of the shear studs and the B / t ratio were varied in the tests. The results show that the arrangement and spacing of the shear studs can considerably influence the buckling shapes and loading capacity of the steel plates. Three-dimensional finite element (FE) models were developed to simulate the behavior of DSC panels subject to compression, and the FE results were found to be in good agreement with the observed buckling behavior during tests. A theoretical model based on Euler's equation was also proposed to predict the buckling stress of steel plates, and it showed reasonable agreement with the experimental measurements and FE results. The formula proposed in this paper can be used for determining the number or spacing of shear studs in DSC walls. [ABSTRACT FROM AUTHOR]

Sustainable development could have a significant impact on conventional construction, reducing or replacing steel and concrete as primary materials in structures. Bamboo, a natural resource, has been used as a general building material for decades in some regions of the world. Countries in Asia and South America have found many uses for bamboo because it grows rapidly and has excellent mechanical properties. The purpose of this paper is to test the designs of different configurations of bolted connections in order to create a composite bamboo I-shaped beam for further applications. Three different configurations of connections for a bamboo composite I-shaped beam were analyzed, with the purpose of identifying an optimal configuration that results in a stiffer, safer beam. A three-dimensional Finite Element Model (FEM) computational model was developed to identify areas of high stress concentration and maximum deflection for the various connection configurations. The findings of this paper are a first step in the process of considering and validating composite bamboo I-shaped beams as a primary construction material in structures such as bridges and buildings. [ABSTRACT FROM AUTHOR]

• Error using only force in the constitutive characterization of heterogeneous strain. • Use of heterogeneous deformation field for accurate constitutive characterization. • Use of the non-conflicting concept to assess the performance of constitutive models. The mechanical characterization of thermoplastics submitted to finite strain is a non-trivial procedure since they may present necking and cold-drawing. These phenomena are associated with heterogeneous strain fields that may mask the real stress–strain curve and lead to mistaken conclusions about the capability of constitutive models to represent the material mechanical response. Aiming to shed light on this issue, this paper presents a numerical study based on a Finite Element Method Updating (FEMU) technique to obtain the true stress–strain curve of a thermoplastic specimen. FEMU technique is employed to characterize three elastoplastic models with different mathematical frameworks. Inverse problems are constructed considering force response and displacement data of a heterogeneous strain field on the specimen due to the necking and neck propagation kinematics. Results shown that even a very simple multilinear elastoplastic model, available in commercial software, is capable of representing force response of a tensile test when only experimental force data is considered. However, when the necking kinematics is taken into account, the studied models present different results and poor mechanical behavior representation, indicating that only the force data obtained from a tensile test is not enough to establish conclusions about the performance of a constitutive model when heterogeneous strain field occurs. Since none of the models was capable of accurately reproduce the experimental force and kinematics data, to evaluate which model performs better, it is proposed a multi-objective analysis of Pareto front results. [ABSTRACT FROM AUTHOR]

This paper presents a mathematically dynamic model of a Delta robot with flexible links. The mathematical models of the robot cannot be represented by partial differential equations, so this paper utilizes the kineto-elasto-dynamics and the finite element method to perform a mathematical model. Each link of the robot is modeled by multiple beam elements with an axial displacement, an axial torsion, and two transverse displacements. In literature, element assembling usually imposes a set of algebraic constraint equations, which are difficultly solved simultaneously. This paper proposes an alternative approach. A set of global variables based on the D–H method is defined, and the Euler–Lagrange’s equation is applied to derive the model without using any constraint equations. The developed model is a set of linear time-varying differential equations, which can describe the flexible motions with respect to the rigid body configuration. Furthermore, the natural frequency analysis and the convergence analysis are performed first, and then two types of paths are designed for the motions of the end-effector. The first path is a constant-speed circular motion in order to demonstrate the numerical simulations of the model at the steady state, and the second path is an inverted-U path, which is commonly used to operate a pick-to-place motion in industry. [ABSTRACT FROM AUTHOR]

This paper presents a thermomechanical study of the stresses which eventually occur in through glass vias (TGVs) due to the coefficient of thermal expansion (CTE) mismatch. The objective of the analysis is to assess the thermal stress variations in TGVs of different geometries. The main contribution of this paper is the elaboration of mathematical models to describe the thermomechanical stress in TGVs. To validate these models, a comparison with a linear finite element analysis (FEA) is carried out. The findings can be used to improve the reliability and engineering design in three-dimensional microelectronic packaging. [ABSTRACT FROM AUTHOR]

The non-uniformly distributed material damping in single-layer latticed domes subjected to earthquake ground motions has been ignored in engineering practice, and the structural damping of bearings and joints has been modeled at a structural level in previous studies. In this paper, an explicit method for modeling the material damping and structural damping using a finite element method is proposed. The proposed method includes important characteristics for modeling single-layer latticed domes. The steel material damping is directly taken into account using Ramberg–Osgood material model (power-law) with hysteretic damping; the structural damping at bearings is modeled based on the bearing type. The ball joints of domes tend to be simplified as nodes in the finite element method without considering the actual geometric shapes and sizes of the balls for convenience. In this paper, the energy dissipation at joints and modeling methods for damping are proposed and discussed in terms of the joint type in domes. To illustrate the proposed method for computation, a typical single-layer latticed dome with base isolation bearings subjected to six near-fault earthquake ground motions is selected as an example. The dynamic demands of this single-layer latticed dome are analyzed using the simulation technology proposed in this paper. The effects of key parameters of the dome on the damping forces, which are of interest to many practitioners, are presented and discussed. Compared with the previous modeling methods for damping, the proposed method can model the damping effects of domes with a higher fidelity, which eliminates the unrealistically high forces generated with conventional modeling methods. [ABSTRACT FROM AUTHOR]

The need of efficient modelling of textile materials at meso-scale increased considerably in the last decade. Several approaches have been proposed which present different kinds of drawbacks, the most important being their high computation time. The present paper aims to present a new tool for modelling textile materials using the yarn as constitutive element. Because fibre tows length is much higher than their transverse dimensions, beam elements seem to be the most convenient structural finite element tool. Unfortunately, classical beam theories assume that the cross section acts as a rigid which cannot describe the transverse compression and shape change of the yarn. In this paper, we present a new 3D beam element with the aim to achieve the results with section changes while breaking from classical beam hypothesis. Firstly, we start from 2D beam element with thickness change by adding a transverse strain component, which is inspired by previous works on the shell elements. Secondly, the formulation is extended to 3D beam elements, two transverse normal strain components are added with coupling so that full 3D constitutive law can be used. Finally, some numerical examples are presented using the new 3D beam elements which show that the results are exactly the same as those given by 3D elements in ABAQUS/Standard. [ABSTRACT FROM AUTHOR]

The prediction of fatigue crack growth is a major concern in the design of mechanical components and engineering structures subjected to cyclic loading. One of the best-known numerical approaches is the adaptive remeshing technique based on the finite element method. This paper aims to provide an overview of adaptive remeshing technique proposals developed to evaluate the crack shape evolution and fatigue life. In addition, a systematic identification of the main numerical variables affecting the accuracy of the above-mentioned technique is provided. The effects of the main physical variables on fatigue crack paths are discussed in the last part of the paper. [ABSTRACT FROM AUTHOR]

No one can deny the role of synthetic polymers as engineering materials - they are all around us in our everyday life. Also due to the constant progress in material engineering, polymers, and among them elastomers, find increasing usage in civil engineering. Computer modelling of elastomers requires special description of material and use of non-linear finite element method. Available, free and commercial software use many different approaches in elastomers modelling, thus comparison of results may display discrepancies. Even if used method is the same, its computer implementation may vary, therefore using various software, one can obtain differing output. The paper presents comparison of results obtained from four computational packages devoted to FEA: Abaqus, GetFEM++, Tochnog, FEBio. It can be seen as an overview of the software that can be used in modelling rubber-like components. It highlights differences in material description (for instance in names of hyperelastic laws and employed formulas) and used multi-field variational principles in modelling material's incompressibility. Examples included in the paper can be treated as benchmarks, that can be helpful in verifying third party software or the one developed by readers. [ABSTRACT FROM AUTHOR]

In this paper we study from a mathematical point of view the drug release and the degradation process in the context of biodegradable intravitreal implants. In particular, two different clinical situations are considered: non-vitrectomized and vitrectomized eyes. In the former case we assume that the vitreous humor is replaced by a saline solution or a silicone oil. In intravitreal space, the intravitreal liquid enters the implant by non-Fickian diffusion causing the degradation of the poly(lactic-co-glycolic acid) based implant. Then, drug in the implant dissolves and diffuses out of the polymeric matrix. The transport of drug in the vitreous chamber and retina is modeled by Fickian diffusion and convection generated by the flow of the vitreous humor. In order to numerically solve the system of partial differential equations that define the model, we propose an Implicit–Explicit finite element method that allows for the decoupling of the solution reducing the computational cost of the simulations. Several numerical experiments showing the effectiveness of the proposed numerical schemes are also included. The proposed mathematical model may be useful to optimize patient specific treatments in clinical practice. • A model for degradation and drug delivery from a PLGA ocular implant is proposed. • The model studies the effects of the LA and GA into the break of the polymeric chains. • Humor diffuses into the implant creating a non-Fickian mass flux. • Drug release occurs by diffusion associated to humor absorption and dissolution. • Stability analysis of the fully couple model. [ABSTRACT FROM AUTHOR]

In this paper thermo-mechanical stresses generated by TSV annealing are the center of interest. For this reason TSV die samples underwent annealing at 250 °C for 2 h. In order to characterize the stress state after annealing μ-Raman spectroscopy (μRS) line scans were carried out subsequently using a 442 nm laser. Then the respective spectra were fitted with a Lorentz function and the associated peak shifts were calculated. In general these results can be used to identify regions of mechanical tension. Unfortunately, μRS results do not allow any differentiation of the stress tensor components. Therefore a finite element model was developed to determine the stress tensor components after annealing. The FE-model was supplemented by a Matlab script, which converted stress data from simulation into Raman shifts using a general hypothesis. Further on physical aspects like penetration depth and laser spot size were taken into account. So the evaluation moved from single node results to a constrained section similar to the laser excited region in a μRS measurement. Proceeding this way allowed the adaption of FE results to μRS measurement properties. This enabled a bilateral validation of measurement and simulation. In summary our paper contributes valuable results for the TSV stress characterization and demonstrates further progress in μRS measurements in combination with FEM. [ABSTRACT FROM AUTHOR]

This paper deals with modeling and model reduction methods intended to sandwich structures with viscoelastic materials. The modeling step is carried out by combining the First order shear deformation theory (FSDT) with the Golla–Hughes–Mc Tavish (GHM) model. The GHM model introduces auxiliary coordinates to take into account the frequency dependence of viscoelastic materials which, combined with the finite element method (FEM), leads to large order models. This paper focuses on the use of model reduction methods. The reduced models compared to the full model are illustrated by three numerical examples in order to outline the performance, the practical interest of these methods and their validity domains. [ABSTRACT FROM AUTHOR]

The higher-order gradient plasticity theory is successful in explaining the size effects encountered at the micron and submicron length scale. Due to the incorporation of spatial gradients of one or more internal variables in these theories and the associated non-classical boundary conditions, special types of elements in the finite element method maybe necessary. This makes the numerical implementation of this higher-order theory not straightforward. In this paper, a robust but straightforward numerical implementation of higher-order gradient-dependent plasticity theories is presented. The novelty of this paper is in (1) the application of the meshless methods, particularly the moving weighted least square method, combined with the finite element method for the numerical computation of plastic strain gradients, and (2) the numerical implementation of different types of higher-order microscopic boundary conditions at internal/external surfaces, interfaces, and moving elastic–plastic boundaries. The proposed numerical implementation algorithms can be easily adapted in the implementation of any form of higher-order gradient-dependent constitutive models. Examples of applying the current numerical approach is demonstrated for capturing mesh-objective shear band formation and size effect and boundary layer formation in thin films on elastic substrates and metal matrix composites with embedded elastic inclusions through the consideration of stiff, intermediate, and soft interfaces. [ABSTRACT FROM AUTHOR]

In this paper, the structural response of steel tubular wind turbine towers with various design configurations is analysed using FEM modelling. Towers of various heights between 50 and 250 m are considered and investigated with three different design options as follows: (i) thick walled tower with internal horizontal stiffening rings, (ii) thick walled tower without stiffening rings and (iii) thin walled tower with stiffening rings. Based on this analysis, weight reduction ratios are examined in relation to the horizontal sway and von Mises stress increase ratios in order to identify a more efficient design approach between reducing the wall thickness and adopting internal stiffeners. All studied design solutions satisfy the strength and serviceability requirements as specified by the design codes of practice. In the final part of paper, the dynamic characteristics of these three types of towers have been examined to obtain the natural frequencies and mode shapes. The studied model ignored the mass of nacelle-rotor system and the wind turbines, namely, only the isolated tower was included. Furthermore, the recommendations to avoid resonance for each height case are proposed. [ABSTRACT FROM AUTHOR]

Leveling is a process used to minimize the bending defects in the steel industry. It plays an important role in delivering the desired material properties and product standards. This paper presents an analytical model for predicting the leveling process for H-beams with strong and weak axis bending defects. In this paper, an analytical model is first developed with the computational procedure of describing the continuous bending and reversed bending process, as well as the unloading process. Then, the developed analytical model and computational procedure are evaluated by a comparative study of results obtained from experimental data. Finally, the leveling process including curvature, trajectory, bending and residual stress distributions are evaluated for typical H-beam made of construction steel using the developed method. It is found that defective H-beam with different initial curvature tends to be flatted after the leveling process and the developed analytical model is much superior than finite element based modeling approach in terms of computational efficiency with the same level of accuracy. [ABSTRACT FROM AUTHOR]

• Three-dimensional finite element simulation of flood discharge atomization process was carried out by the numerical method. • The compressible fluid dynamics equation is solved by the finite element method with a suitable solution strategy. • The numerical simulation results of flood discharge atomization agree well with the measured results. Flood discharge atomization is a phenomenon of water fog diffusion caused by the discharge of water from a spillway structure, which brings strong wind and heavy rainfall. These unnatural winds and rainfall are harmful for the safe operation of hydropower stations with high water heads. Compared to the method of prototype observations, physical models and mathematical models, which are semi-theoretical and semi-empirical, numerical simulation methods have the advantage of being not limited by a similar scale and are more economical. A finite element model is presented to simulate flood discharge atomization based on water–air two-phase flow in this paper. Equations governing flood discharge atomization are composed of partial differential equations of mass and momentum conservation laws with unknowns for pressure, velocity and the water concentration. The finite element method is used to solve the governing equations by adopting appropriate solution strategies to increase the convergence and numerical stability. Then, the finite element model is applied to a practical project, the Shuibuya hydropower station, which experienced a flood discharge in 2016. Simulation results show that the proposed model can simulate flood discharge atomization with efficient convergence and numerical stability in three dimensions, and good agreement was observed between numerical simulations and prototype observational data. Based on the simulation results, the mechanism of flood discharge atomization was analyzed. [ABSTRACT FROM AUTHOR]

In this paper, the thermal performance of the heat storage unit made of repeatable modules was carried out. The heat accumulator that is used in solar installations may be a separate unit, or it may be a building wall insulated on the inner and outer surfaces. It is a heat storage unit with dynamic discharge using forced air flow through the channels. The transient temperature field in the walls of the channels was modeled using three different methods: finite volume method (FVM), control volume based finite element method (CVFEM), and finite element method (FEM). The CVFEM was chosen for the construction of a full model of the heat storage unit due to the ease of modeling a solid filling of a heat storage unit with a complex shape. The numerical model of the heat storage unit with the air flow through channels was developed. The CFD simulation was also carried out. In the mathematical model of the heat accumulator, it was taken into account that air flow can be laminar, transitional or turbulent. The finite volume method with integral averaging of air temperature over the finite volume length was developed so that accurate air temperature distribution can be determined even with a small number of finite volumes. • A numerical model of the heat storage unit was developed. • The air temperature inside the control volume was calculated analytically. • Dynamic energy performance of the heat storage unit was carried out. • The numerical model was compared with the CFD model and experiment. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new mathematical model of language interactions considering bilingualism. We assume diffusive and convective language spreads with language exchange terms. The resulting model consists of a coupled system of partial differential equations for three functions. We develop a finite element approximation of the mathematical model using implicit and partially explicit time schemes. In addition, we present a partial learning approach for this problem using a partially explicit discretization. In this method, we train a Deep Neural Network to predict the values of the difficult-to-compute (implicit) part of the solution at some observed points. We then perform linear temporal interpolation and spatial interpolation using the Proper Orthogonal Decomposition (POD) and the Discrete Empirical Interpolation Method (DEIM). To test the proposed approach and the model, we consider two model problems. Each of them simulates different language situations. For each problem, we compute the relative errors of the proposed approach and define the different parts of the error. The numerical results show that the proposed approach can provide good accuracy while reducing computational costs. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents a synergic and multidisciplinary approach where laser scanner survey, radar interferometric monitoring and finite element (FE) numerical modelling are used for expeditious and no-contact dynamic identification of monumental masonry towers. The methodology is applied to a real case of great historical interest: the “Torre del Mangia” (Mangia's tower) in Siena (Italy). The tower geometry was acquired through Terrestrial Laser Scanning (TLS) techniques. The tower oscillations were detected using an interferometric radar in “Piazza del Campo”, the square facing the Mangia's Tower, along three alignments, and movement of the structure at several heights were recorded. A FE model, built on the basis of the geometry acquired through the TLS, was used to interpret and verify the physical meaning of the experimental results. Through the discussion of the case study, the paper shows that the proposed approach can be considered as an effective and expeditious method for assessing the dynamic behavior of monumental buildings (and to plan interventions) on territorial scale. [Copyright &y& Elsevier]

Highlights: [•] This paper gives the generalization of the intrinsic PPR model to three-dimensions. [•] This paper also gives a description of the PPR’s implementation in a FE framework. [•] Four test specimens are considered for the 3D PPR model’s verification. [•] The 3D PPR model’s performance under severe mode-mixity is also considered. [ABSTRACT FROM AUTHOR]