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EN
The Brushless Doubly-fed Induction Machine (BDFIM) is a new topology machine proposed for the generation of electrical energy at variable speed. The stator of this machine has two independent windings with different numbers of poles (power winding and control winding). Its functioning is conditioned by certain physical constraints, i.e., the relation between the speed of the rotor, the polarities of the two windings and their frequencies. We have developed in this paper a finite element model to study and verify the operating limits of the BDFIM (2.2 Kw and 1/3 pairs of poles) on flux2d.
EN
Classical approach is a popular method used in the analysis of structures including bending plates, but these plates can have highly irregular geometry and contain holes or may be subjected to loading irregularity. Hence, the analysis is further complicated and the classical approaches are not valid. Thus, the Finite Element Method is used to control the accuracy and it is needed for more difficult problems. In the present study Fourier series theory as classical approach and finite element method of analysis were discussed and the numerical examples of a simply supported and fixed supported square steel plate were used to compare them. The results obtained with general public software LISA that uses FEM was plotted according to the element types, both quadrangular and triangular. Their convergence was verified with the values obtained from classical approach to validate the results of FEM from LISA. The results showed the conformity with the existing theories that the greater discretization the more the reality is approached. The convergence error of 5% was taken as the maximum for the element types and meshes to be used for highly sophisticated plate systems. The ratios of element size to the size of the whole square plate to be used for general cases of square plate dimensions were established.
EN
Nonlinear soil-linear structure computational strategy is commonly accepted in the community of geotechnical engineers using advanced finite element software for solving complex soil-structure interaction problems. However, further design procedure of the structural elements is carried out using increased values of the computed elastic stress resultants. It is absolutely not clear whether this method is conservative and, therefore, whether safe or not. To tackle this problem, a fully consistent nonlinear analysis of a deep excavation protected by the diaphragm wall is analysed here. The subsoil is modelled using the Hardening Soil model, while reinforced concrete is modelled using the modified Lee-Fenves model enhanced by the Eurocode 2 (EC2)-compatible creep module, developed by the author. It is shown that the commonly used nonlinear soil-linear structure computational strategy may yield insufficient amount of reinforcement from the ultimate limit state (ULS) and serviceability limit state (SLS) points of view. A consistent and conservative method of combining fully nonlinear analysis and the rules imposed by the EC2 is proposed.
EN
The problem has been studied of reducing the materials consumption of a combined support in extraction mine workings and increasing their stability in a zone of stope works influence when reused mining of flat-lying coal seams at adjacent mining site. The mechanism has been developed of rock pressure manifestation in the vicinity of mine working and the loading of its support elements on the basis of the following key positions: the formation of zones of unloading and increased rock pressure around the mine working; the formation of areas of weakened and broken rocks, their interaction with support and holistic rock massif; development of stratification along the planes of weakening by thickness of a lithological variety and along the planes of bedding the adjacent lithotypes; partitioning of rock layer into blocks by fractures, by perpendicular planes of weakening and bedding planes, and other factors. The specific tasks have been solved by the finite element method according to the four-parameter spatial optimization scheme of the support interaction with a rock massif. The patterns have been determined of connection between the rational operation modes of mine working support elements and basic geomechanical factors, affecting significantly on the loading of these elements, as well as their interaction with different deformation and force characteristics.
EN
The mechanical discrete or continuum structures are actually of great importance in the application field of contemporary modern industry. However, during their life time these structures are often subjected to considerable external stresses or to high amplitudes of vibrations which can cause them large deformations and internal stresses which can cause them internal cracking or even their total destruction. In order to avoid these types of problems, the concept of static and dynamic analysis of these structures is recommended, and due to the complexity of their shape and size, the finite element method is the most used. The latter is currently recognized as a very powerful technique for the static and dynamic analysis of discrete or continuous structures of complicated form applied in the field of mechanics, aeronautics, civil engineering, maritime or robotics. Consequently, the calculation and dimensioning of these mechanical systems by the finite element method plays an important role at the service of the industry for possible sizing and prediction of their lifetime. Our work consists of static and dynamic analysis of two-dimensional discrete and continuous mechanical systems using the finite element method based on the main elements of bars, beams and plates, under the effect of external excitations with different boundary conditions. The discrete structures considered are two-dimensional in metallic framework interconnected to the nodes by welding, riveting or bolted under various boundary conditions. Their elements are modeled comparatively by bar elements and beam elements, while for continuous structures the elements are rectangular thin plates with different boundary conditions. The excitation forces are based on periodic, random or impulsive forces and a numerical solution by development of a program to describe the behavior of these structures is realized. The mass and stiffness matrices of all the structures are determined respectively by assembling the bars, beam and plate elements based on the kinetic and deformation energy for each element. The displacements, the node reactions and the axial forces in all the elements as well as the transverse stresses and the eigenvalues of the structures under different boundary conditions were also calculated and good results were obtained compared to those obtained using other software already existing. In fact, analysis using the finite element method will allow the proper dimensioning and design of complex industrial mechanical structures according to different boundary conditions, their internal loading and their vibratory level.
EN
Development of groundwater flow, and solute and heat transport models for underground and open-pit mining areas is a challenging and very complex issue. Despite the fact, models play an increasingly common role in mine water management. The aim of the paper is to present and illustrate theoretical aspects and practical strategies facilitating groundwater model set-up for mine sites by means of FEFLOW software. FEFLOW solved governing equations based on finite elements methods, which enables users to create models with very flexible meshing strategies including time-varying geometries. Unstructured and structured mesh generators allow creating very complex geological settings and with complex geometrical designs, as found for example in mine dewatering (open-cast geometry, inclined dewatering wells, inclined faults), or underground structures (pipes, tunnels, shafts etc.). In order to obtain reliable results and reduce uncertainty in provided forecast for mine sites, groundwater models often should be developed for transient condition and involve unsaturated flow and transport, fracture flow, density effects, chemical reactions, or time-varying behaviour of boundary conditions and material properties (such as conductivity or porosity). FEFLOW enables groundwater modeller set-up these all physical processes and via plug-ins extended functionality by integrated FEFLOW models with other models: geochemical (PHREEQC), watershed (MIKE 11, Hydro River) or develop user own plug-ins. Considering the above, FEFLOW seems to be appropriate software for accurate and reliable models developmentfor mine sites, and an interesting alternative for more widely used MODFLOW models in Poland.
EN
This article shows the static analysis of rear suspension beam loading in a combine harvester manufactured by New Holland Bizon Sp. z o.o. The model of the examined machine with thresher rotor (Z110 model) was being manufactured until 2001, and further modifications of combine harvesters with the mentioned threshing system are being made so far [1]. The research conducted with the use of programs: Inventor 2017 for generating the digital model and Nastran In-CAD 2017 for simulation calculations. The aim of this article is to analyze and evaluate the accuracy of the combine harvester Bizon Z110 construction. The findings of the study suggest a possibility of stress accumulation in welded joints of construction. In result, solutions to the described problems were provided.
PL
Niniejszy artykuł przedstawia analizę statyczną belki nośnej wózka tylnego kombajnu zbożowego produkowanego przez New Holland Bizon Sp. z o.o. Model analizowanej maszyny o omłocie rotorowym (wersji Z110) był produkowany do 2001 roku, a kolejne modyfikacje kombajnów zbożowych o wspomnianym systemie omłotowym produkowane są do chwili obecnej [1]. Do badań wykorzystano: pakiet Inventor 2017 dla wygenerowania modelu numerycznego, natomiast do obliczeń symulacyjnych - Nastran in Cad 2017. Celem artykułu jest analiza i ocena prawidłowości konstrukcji ramy kombajnu zbożowego Bizon Z110. Uzyskane wyniki wskazują na możliwość kumulowania się naprężeń w węzłach spawanych ramy. W konsekwencji zaproponowano możliwość rozwiązania opisywanych problemów.
EN
The main purpose of this paper is to analyze the convergence of the proposed algorithm of the finite element methods coupled with a Euler discretization scheme. Also, an optimal error estimate with an asymptotic behavior in uniform norm are given for an evolutionary nonlinear Hamilton Jacobi Bellman (HJB) equation with respect to the Dirichlet boundary conditions.
EN
In this paper, we show that sensitivity analysis in connection with material parameter identification problems – using implicit finite elements of quasi-static problems on the basis of evolutionary-type constitutive equations – is related to simultaneous sensitivity equations and internal numerical differentiation. Thus, this study mainly focuses on investigating how these approaches are connected to the solution procedures based on finite elements. In addition, we discuss how to consider reaction forces in the sensitivity analysis, as this aspect is often neglected despite the fact that experimental results often involve force data.
EN
The paper presents a brief description of the Abaqus Simulia plane stress quadrilateral elements (CPS4R, CPS4I, CPS4, CPS8R, CPS8). Comparison of the results quality obtained using each of them was done. There was considered two dimensional big displacements compression test for a highly orthotropic material. Simulations were performed for the compression in two perpendicular directions.
EN
We consider the generalized Nash equilibrium as a solution concept for multiobjective optimal control problems governed by elliptic partial differential equations with constraints not only for the control but also for the state variables. In the first part, we present a constructive proof of the existence of a generalized Nash equilibrium via an approximating sequence of suitable finite dimensional discretizations. In the second part, we propose a variant of a potential reduction algorithm for the numerical solution of these discretized problems. In contrast to the existing numerical approaches ours does not require the computation of the control–to–state mapping. Instead we introduce different state variables and guarantee that they become equal at a solution. We prove sufficient conditions for the convergence of our algorithm to a solution. Furthermore, some numerical results showing the applicability are provided.
EN
ELRIS2D is an open source code written in MATLAB for the twodimensional inversion of direct current resistivity (DCR) and time domain induced polarization (IP) data. The user interface of the program is designed for functionality and ease of use. All available settings of the program can be reached from the main window. The subsurface is discretized using a hybrid mesh generated by the combination of structured and unstructured meshes, which reduces the computational cost of the whole inversion procedure. The inversion routine is based on the smoothness constrained least squares method. In order to verify the program, responses of two test models and field data sets were inverted. The models inverted from the synthetic data sets are consistent with the original test models in both DC resistivity and IP cases. A field data set acquired in an archaeological site is also used for the verification of outcomes of the program in comparison with the excavation results.
EN
The paper is concerned with free vibrations of geometrically non-linear elastic Timoshenko beams with immovable supports. The equations of motion are derived by applying the Hamilton principle. The approximate solutions are based on the negligence of longitudinal inertia forces but inclusion of longitudinal deformations. The Ritz method is used to determine non-linear modes and the associated non-linear natural frequencies depending on the vibration amplitude. The beam is discretized into linear elements with independent displacement fields. Consideration of the beams divided into the regular mesh enables one to express the equilibrium conditions for an arbitrary large number of elements in form of one difference equation. Owing to this, it is possible to obtain an analytical solution of the dynamic problem although it has been formulated by the finite element method. Some numerical results are given to show the effects of vibration amplitude, shear deformation, thickness ratio, rotary inertia, mass distribution and boundary conditions on the non-linear natural frequencies of discrete Timoshenko beams.
EN
This paper aims at providing a framework for comprehensive steady-state time-domain analysis of rotating machines considering motion. The steady-state waveforms of electromagnetic and circuit quantities are computed via iterative solution of the nonlinear field-circuit-and-motion problem with constraints of time periodicity. The cases with forced speed and forced load torque are considered. A comparison of execution times with a conventional time-stepping transient model is carried out for two different machines. The numerical stability of a time-periodic model with forced speed is shown to be worse than that of traditional transient time-stepping one, although the model converges within a reasonable number of iterations. This is not the case if forced load via equation of mechanical balance is accounted for. To ensure convergence of the iterative process the physical equation of motion is replaced by the fixed-point equation. In this way the model delivers time-periodic solutions regarding not only the electromagnetic quantities but also the rotational speed.
EN
The study presents results of experiments and numerical analyses concerning thin-walled shells used as components of aircraft structures. The solution, which is proposed here, consists in stiffening such elements by means of integral ribs. A comparative analysis has been carried out between the suggested design solution and the reference structure. In the experimental part of the study, an optical scanner with digital image correlation has been used. Nonlinear numerical analyses have been carried out with the use of software based on the finite element method.
EN
An industrial application is presented to validate a finite element analysis of 3-dimensional, nonlinear eddy-current problems with periodic excitation. The harmonicbalance method and the fixed-point technique are applied to get the steady state solution using the finite element method. The losses occurring in steel reinforcements underneath a reactor due to induced eddy-currents are computed and compared to measurements.
17
Content available Numerical arch and vault analysis
EN
The present contribution discusses various approaches towards the numerical analysis of arches, particularly finite element methods based on a continuum mechanics approach vs. rigid-body approaches. We employ beam elements and a simple model for the interaction between axial compression and bending. The model is based on the assumption that cracks follow the radial joints, and on a simplified concept of incorporating finite compressive strength. We establish a transition.
PL
Artykuł omawia różne podejścia do analizy numerycznej łuków, a zwłaszcza metod elementów skończonych w oparciu o podejście mechaniki ośrodków ciągłych vs. podejście sztywno-ustrojowych.
18
Content available remote Optimal Design of Shells of Uniform Stability Stiffened by Ribs
EN
The problem of optimal design of rotationally symmetrical shells of uniform stability stiffened by ribs was discussed in the current paper. The structure was modelled in ANSYS software and solved by FEM method. The formulation of uniform local stability was successfully verified by the linear buckling solution. The optimization tasks were solved numerically using the modified Particle Swarm Optimization algorithm. The critical loading multiplier was increased by determining the optimal shape of the meridian, distribution of a wall thickness in a coat of shell and the placement of ribs inside the shell.
EN
The study presents results of research on the problem of obtaining credible results of nonlinear FEM analyses of thin-walled load-bearing structures subjected to post-critical loads. The similarity of numerical simulation results and actual stress distribution states depends on the correct numerical reproduction of bifurcations that occur during an advanced deformation process.
EN
Simulation of movement of a large number of charged particles in external electrostatic field is of great importance for a correct design of separators whose aim is to select them according to the sign of their charge. The paper deals with modeling of their trajectories in a specific arrangement consisting of a profile vessel equipped with two electrodes and several collecting bins. Electric field between the electrodes is determined using a fully adaptive higher-order finite element method. The movement (velocities and trajectories) of the particles affected by electric field, gravity and aerodynamic resistance is modeled by an adaptive Runge-Kutta-Fehlberg method with an appropriately varying time step. On the other hand, their charges are rather low, so that it is possible to neglect the Coulomb forces acting among them. The methodology is illustrated by a typical example whose results are discussed.
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