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Application of heuristic methods to identification of the parameters of discrete-continuous models

Cekus Dawid, Kwiatoń Paweł, Šofer Michal, Šofer Pavel

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2022

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Vol. 70, nr 1

art. no. e140150

EN

The article presents the process of identifying discrete-continuous models with the use of heuristic algorithms. A stepped cantilever beam was used as an example of a discrete-continuous model. The theoretical model was developed based on the formalism of Lagrange multipliers and the Timoshenko theory. Based on experimental research, the theoretical model was validated and the optimization problem was formulated. Optimizations were made for two algorithms: genetic (GA) and particle swarm (PSO). The minimization of the relative error of the obtained experimental and numerical results was used as the objective function. The performed process of identifying the theoretical model can be used to determine the eigenfrequencies of models without the need to conduct experimental tests. The presented methodology regarding the parameter identification of the beams with the variable cross-sectional area (according to the Timosheno theory) with additional discrete components allows us to solve similar problems without the need to exit complex patterns.

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Assessment of the Change in the Tin Concentration in Bronzes to the Basic Components of the Sound of Bells

Cekus Dawid, Nadolski Maciej

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 2

531--535

EN

The subject of the study was to determine the impact of changes in mechanical properties of high-tin bronzes on the basic components of the sound of a bell. Change in the tin concentration in the range of about 7.5 to 20 parts wt. in a casting alloy significantly affects the mechanical properties of the alloy such as Young’s modulus or hardness. The free vibrations of bells were obtained with the help of the finite element method. In the numerical analyses the mechanical properties of standard alloys were adopted. The obtained natural frequencies of the bell made of a bronze with different tin concentration in copper were compared with the acoustic properties of a real bell casted on the basis of the same ribs. A significant effect of the increase in the alloying share of tin on the obtained results was stated. In addition, the acoustic analysis of aluminum bronze C95500 have been performed. Based on the obtained results, authors stated that this material can replace the commonly used high tin bronze C91300 for the unit production of bells.

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Projekt i badania symulacyjne egzoszkieletu kończyny górnej

Cekus Dawid, Kubik-Maciąg Ilona, Kwiatoń Paweł

Modelowanie Inżynierskie

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2019

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T. 39, nr 70

17--23

PL

Prezentowana praca dotyczy wstępnego projektu egzoszkieletu kończyny górnej w wybranym systemie CAD/CAE oraz opracowania modelu obliczeniowego analizowanego zagadnienia. Rozważany model egzoszkieletu kończyny górnej poddany został badaniom pozwalającym określić własności wytrzymałościowe (lokalizację maksymalnych naprężeń oraz odkształceń dla modelu znajdującego się w spoczynku), co z kolei umożliwiło przeprowadzenie modyfikacji konstrukcji w celu poprawy jego własności wytrzymałościowych oraz ograniczenia masy. W kolejnym etapie badań przeanalizowano model egzoszkieletu kończyny górnej w trakcie działania na niego wymuszeń zmiennych w czasie, odpowiadających ruchowi wspomagającemu przemieszczanie się kończyny górnej współdziałającej z egzoszkieletem.

EN

Presented paper concerns implementation in selected CAD/CAE environment the preliminary project of the upper-limb exoskeleton. Also the paper contains the development of a computational model for the considered problem. Designed model of upper-limb exoskeleton has been used to conduct the structural simulations (which allowed to determine the location of maximum stress and strain in stillness). The obtained results allowed to modification of the exoskeleton structure in order to improve the strength properties and weight reduction. The next part of the studies the analyze of the model of upper-limb exoskeleton during the exemplary duty cycle were conduct. The sample duty cycle corresponded to the movement supporting the upper-limb interacting with designed exoskeleton.