Search Everything

Tip: Search using "First Name + Last Name", e.g.
János Kiss instead of Kiss János.

Publications - 6525

NVH characterization of a ladder-like welded structure using finite element analysis and experimental method

Dániel Feszty Balázs Vehovszky Attila Schweighardt

Publication Name: Advances in Acoustics Noise and Vibration 2021 Proceedings of the 27th International Congress on Sound and Vibration Icsv 2021

Publication Date: 2021-01-01

Volume: Unknown

Issue: Unknown

Page Range: Unknown

Description:

In vehicle industry, considering a chassis, the evaluation of the experimental modal analysis is usually done up to 80 Hz, since the modal density is increasing with frequency. In addition, the deviation between the measurement and simulation is getting more significant at higher frequencies. The purpose of this study is to extend the usable test range and to improve the accuracy of the results both in case of measurement and FE (Finite Element) simulation. Present paper introduces the vibrational characterization of a ladder-like welded structure. This test case represents a simplified model of a vehicle's frame consisting of rod-like elements with high stiffness, connected to each other in welded junctions. Although such simulational and experimental modal analysis procedures are widely used in practice, results can significantly change according to the used method and the fine-tuning of parameters. For this reason, a further goal is to find the best measurement and simulation technique for the given structure. During the FE analysis different modelling solutions and element types were compared. In order to discover the effect of the manufacturing inaccuracies, the same measurements were performed on two distinct, but theoretically identical samples. The influence of the experimental setup (e.g. excitation and fixing method) and settings were investigated as well. Finally, FE simulation and experimental results are compared using Frequency Response Functions.

Open Access: Yes

DOI: DOI not available

Separated antecedent and consequent learning for Takagi-Sugeno fuzzy systems

János Botzheim Tamás D. Gedeon Erich Peter Klement Edwin Lughofer Laszlo T. Koczy

Publication Name: IEEE International Conference on Fuzzy Systems

Publication Date: 2006-12-01

Volume: Unknown

Issue: Unknown

Page Range: 2263-2269

Description:

In this paper a new algorithm for the learning of Takagi-Sugeno fuzzy systems is introduced. In the algorithm different learning techniques are applied for the antecedent and the consequent parameters of the fuzzy system. We propose a hybrid method for the antecedent parameters learning based on the combination of the Bacterial Evolutionary Algorithm (BEA) and the Levenberg-Marquardt (LM) method. For the linear parameters in fuzzy systems appearing in the rule consequents the Least Squares (LS) and the Recursive Least Squares (RLS) techniques are applied, which will lead to a global optimal solution of linear parameter vectors in the least squares sense. Therefore a better performance can be guaranteed than with a complete learning by BEA and LM. The paper is concluded by evaluation results based on high-dimensional test data. These evaluation results compare the new method with some conventional fuzzy training methods with respect to approximation accuracy and model complexity. © 2006 IEEE.

Open Access: Yes

DOI: 10.1109/FUZZY.2006.1682014

Rapid tooling by laser powder deposition: Process simulation using finite element analysis

L. Costa Augusto Moita De Deus Tamás Réti R. Vilar

Publication Name: Acta Materialia

Publication Date: 2005-08-01

Volume: 53

Issue: 14

Page Range: 3987-3999

Description:

Laser powder deposition (LPD) is a rapid manufacturing process, whereby near-net-shape components are fabricated by the successive overlapping of layers of laser melted and resolidified material. As new layers of material are deposited, heat is conducted away from recently resolidified material, through the previously deposited layers, inducing cyclic thermal fluctuations in the part as it is built up. These thermal cycles can activate a variety of metallurgical phenomena, such as solid-state transformations, leading to a progressive modification of the material's microstructure and properties. Since the thermal history of the material in the deposited part will differ from point to point and depends on the deposition parameters and build-up strategy, the finished part may present complex distributions of microstructure and properties. In order to achieve the best properties, the deposition process must be optimized and, given its complexity, this optimization can only be effectively done using mathematical simulation methods. In this paper a thermo-kinetic LPD model coupling finite element heat transfer calculations with transformation kinetics and quantitative property-structure relationships is presented. This model was applied to the study of the influence of substrate size and idle time between the deposition of consecutive layers on the microstructure and hardness of a ten-layer AISI 420 steel wall built by LPD. The results show that the thermal history and, hence, the microstructure and properties of the final part, depend significantly on these parameters. © 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Open Access: Yes

DOI: 10.1016/j.actamat.2005.05.003

Performance of PMMA and SBS Modified Asphalt Mixtures in Railway Supplementary Layers and Road Pavements

Szabolcs Fischer Richárd Nagy Şevket Aslan Mohammad Fahad Szabolcs Rosta Furkan Kaya Klaudia Madarász

Publication Name: Periodica Polytechnica Transportation Engineering

Publication Date: 2025-01-01

Volume: 53

Issue: 3

Page Range: 334-346

Description:

The use of recycled waste elastic materials provides a cost-effective and environmentally friendly option for further modifying the performance of asphalt mixtures. Therefore, the effects of different proportions of (PMMA) polymethyl methacrylate derived from waste plastic material were evaluated using the Indirect Tensile Strength Test (ITST) of lab-prepared specimens. Since numerous methods of modifying the conventional asphalt binder are available, in this research, the virgin binder was modified with 1%, 2%, 3%, 4% and 5% PMMA for evaluating optimum performance proportions in terms of Marshall stability and ITST of asphalt mixtures. Furthermore, stiffness modulus tests were performed at frequency values of 1.2 Hz, 1.9 Hz, 3.9 Hz and 5 Hz. The effect of the loading rate from 10 MPa/s to 70 MPa/s was evaluated with an increment of 10 MPa/s for all proportions. Moreover, finite element modeling was performed using the data obtained from dynamic modulus tests with modified Burger's Logit model for evaluation of rutting progression. Results show improved performance of asphalt mixtures with the addition of PMMA, leading to variation in properties including penetration, softening point, Marshall stability and rutting resistance. It is recommended to use 5% PMMA for increased indirect tensile strength, Marshall stability, rutting and fatigue damage resistance.

Open Access: Yes

DOI: 10.3311/PPtr.39763

Comparison of optimized PID and fuzzy control strategies on a mobile pendulum robot

Akos Odry Robert Fullér

Publication Name: Saci 2018 IEEE 12th International Symposium on Applied Computational Intelligence and Informatics Proceedings

Publication Date: 2018-08-20

Volume: Unknown

Issue: Unknown

Page Range: 207-212

Description:

S-This paper investigates the optimized control performances of fuzzy and proportional-integral-derivative (PID) control schemes developed for the stabilization of an under-actuated mobile robot. The fuzzy control strategy had been designed in an earlier paper, its equivalent PID controller-based scheme is established first. Then a complex cost function is defined that evaluates the reference tracking performance, the efficiency of system oscillations suppression and the average current consumption in the motor drive system. The particle swarm optimization (PSO) is applied to tune both control schemes under the same circumstances by minimizing the formulated cost function. Results demonstrate that the optimized fuzzy control strategy provides the same reference tracking quality with significantly better suppression of system oscillations and current peaks compared to the optimized PID control.

Open Access: Yes

DOI: 10.1109/SACI.2018.8440947

Li-BES detection system for plasma turbulence measurements on the COMPASS tokamak

M. Berta G. Anda D. Dunai P. Hacek D. Refy A. Kovácsik J. Krbec M. Hron G. Veres R. Panek S. Zoletnik A. Bencze V. Weinzettl

Publication Name: Fusion Engineering and Design

Publication Date: 2015-10-01

Volume: 96-97

Issue: Unknown

Page Range: 795-798

Description:

A new Li beam emission spectroscopy (Li-BES) diagnostic system with a ∼ cm spatial resolution, and with beam energy ranging from 10 keV up to 120 keV and a 18 channel Avalanche photo diode (APD) detector system sampled at 2 MHz has been recently installed and tested on the COMPASS tokamak. This diagnostic allows to reconstruct density profile based on directly measured light profiles, and to follow turbulent behaviour of the edge plasma. The paper reports technical capabilities of this new system designed for fine spatio-temporal measurements of plasma electron density. Focusing on turbulence-induced fluctuation measurements, we demonstrate how physically relevant information can be extracted using the COMPASS Li-BES system.

Open Access: Yes

DOI: 10.1016/j.fusengdes.2015.06.030

Impact of temperature and pressure of supercritical CO2 media on the physicochemical properties and electrochemical performance of rGO-Sulfur cathodes for rechargeable Li-S batteries

Tamás Szabó Márton Szabados Dóra Zalka Márton Kőrösi Péter B. Nagy Anna Bulátkó Lakshmi Shiva Shankar Edit Székely Krisztina László Robert Kun

Publication Name: Journal of Power Sources

Publication Date: 2026-03-30

Volume: 669

Issue: Unknown

Page Range: Unknown

Description:

Supercritical carbon dioxide (scCO2) is a non-toxic, inert, and widely used solvent in green chemistry, offering tunable properties such as density, diffusivity, viscosity, and polarity, adjustable through temperature, pressure, or co-solvent addition. This study employs the Design of Experiment (DoE) methodology to optimize scCO2-assisted synthesis of Li-S battery cathodes, presenting the first systematic investigation of how scCO2 conditions affect the structural and surface properties of reduced graphene oxide (rGO) during sulfur decoration. Results show that temperature and pressure significantly influence sulfur integration and cathode performance. By combining DoE with detailed electrochemical impedance analysis using complex nonlinear least squares fitting, the study provides deeper insight into composite electrochemical behavior under varying conditions. An optimal rGO structure with low charge transfer resistance, enabling efficient ion and electron transport, was obtained at 150 bar and 60 °C, balancing sulfur loading and pore accessibility. Conversely, harsher conditions (180 bar, 80 °C) caused sulfur agglomeration and higher resistance, reducing performance. These findings highlight the necessity of precisely controlling scCO2 synthesis parameters to enhance cathode structure and improve electrochemical performance and long-term stability of Li-S batteries.

Open Access: Yes

DOI: 10.1016/j.jpowsour.2025.239212

Probabilistic correlation coefficients for possibility distributions

István Harmati Péter Várlaki Robert Fullér

Publication Name: Ines 2011 15th International Conference on Intelligent Engineering Systems Proceedings

Publication Date: 2011-08-22

Volume: Unknown

Issue: Unknown

Page Range: 153-158

Description:

The goal of this paper to introduce two alternative definitions for the possibilistic correlation coefficient by equipping the level sets of a joint possibility distribution with nonuniform probability distributions which are directly derived from the shape function of the joint possibility distribution. We also show some examples for their exact calculation for joint possibility distributions defined by Mamdani, Łukasiewicz and Larsen triangular norms. © 2011 IEEE.

Open Access: Yes

DOI: 10.1109/INES.2011.5954737

On the positivity step size threshold of Runge-Kutta methods

Zoltán Horváth

Publication Name: Applied Numerical Mathematics

Publication Date: 2005-05-01

Volume: 53

Issue: 2-4

Page Range: 341-356

Description:

In the first part of this paper we determine the largest step size of Runge-Kutta (RK) methods for which the corresponding numerical approximations are positive (component-wise non-negative) for arbitrary positive initial vector, whenever the underlying initial value problem (IVP) possesses the related positivity preserving property. We prove that step size thresholds for certain classes of positive IVPs guaranteeing positivity that we derived in a former paper are strict for irreducible and non-confluent RK methods. Investigating the strict positivity step size thresholds we can see that these are rather small if at all positive: often they are, roughly speaking, inverse proportional to the Lipschitz constant of the problem. However, for certain (stiff) IVPs with some particular initial vectors, e.g., for some "smooth" vectors in semi-discretized diffusion problems, we experience preservation of positivity with much larger step sizes than the strict positivity step size threshold. To catch this phenomenon, in the second part of the paper we construct positively invariant sets of positive vectors and derive step size thresholds for the discrete version of the positive invariance. The resulting threshold for discrete positive invariance is, roughly speaking, inverse proportional to the one-sided Lipschitz constant only and is shown in good accordance with some displayed computational experiments. © 2004 IMACS. Published by Elsevier B.V. All rights reserved.

Open Access: Yes

DOI: 10.1016/j.apnum.2004.08.026