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Optimisation of the operating voltage of a multilayer uniaxial dielectric elastomer generator

Sikora Wojciech, Michalczyk Krzysztof

Advances in Science and Technology. Research Journal

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2025

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Vol. 19, no. 6

203--214

EN

The optimum operating parameters for dielectric elastomer generator (DEG) systems, in the sense of the global optimum, refer to their maximum performance in terms of elastomer tensile strength, breakdown voltage value etc. In practice, operating a DEG close to the limit of its strength will involve a limitation of its durability, as DEGs can also suffer fatigue damage. Deviation from the optimum operating parameters, either for reasons of increasing their durability and reliability or simply because of practical limitations in a given application, makes it necessary to search for local optimum operating points. The aim of this study was to analytically determine the optimum working point of a DEG generator operating in a rectangular cycle (constant charge, constant voltage) by the value of the voltage difference between the upper and lower sources. On the basis of capacitance measurements on two generators with two and three active layers (electrodes) operating under uniaxial tensile loading, the theoretical values of the optimal voltage difference ΔU were calculated. The results were then verified experimentally. The empirical values were found to be in agreement with the theory (Fig. 10) and showed that it is possible to predict the performance of a DEG accurately by knowing the variations in its electrical capacitance.

2

A new method for generating virtual models of nonlinear helical springs based on a rigorous mathematical model

Michalczyk Krzysztof, Warzecha Mariusz, Baran Robert

Applied Computer Science

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2023

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Vol. 19, no. 2

96--111

EN

This paper presents a new method for generating nonlinear helical spring geometries based on a rigorous mathematical formulation. The model was developed for two scenarios for modifying a spring with a stepped helix angle: for a fixed helix angle of the active coils and for a fixed overall height of the spring. It allows the development of compression spring geometries with non-linear load-deflection curves, while maintaining predetermined values of selected geometrical parameters, such as the number of passive and active coils and the total height or helix angle of the linear segment of the active coils. Based on the proposed models, Python scripts were developed that can be implemented in any CAD software offering scripting capabilities or equipped with Application Programming Interfaces. Examples of scripts that use the developed model to generate the geometry of selected springs are presented. FEM analyses of quasi-static compression tests carried out for these spring models showed that springs with a wide range of variation in static load-deflection curves, including progressive springs with a high degree of nonlinearity in characteristics, can be obtained using the proposed tools. The obtained load-deflection curves can be described with a high degree of accuracy by power function. The proposed method can find applications in both machine design and spring manufacturing.

3

Experimental analysis of transverse stiffness distribution of helical compression springs

Baran Robert, Michalczyk Krzysztof, Warzecha Mariusz

Acta Mechanica et Automatica

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2023

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Vol. 17, no. 1

95--103

EN

This paper presents the results of an experimental analysis of the distribution of transverse stiffness of cylindrical compression helical springs with selected values of geometric parameters. The influence of the number of active coils and the design of the end coils on the transverse stiffness distribution was investigated. Experimental tests were carried out for 18 sets of spring samples that differed in the number of active coils, end-coil design and spring index, and three measurements were taken per sample, at two values of static axial deflection. The transverse stiffnesses in the radial directions were tested at every 30 angle. A total of 1,296 measurements were taken, from which the transverse stiffness distributions were determined. It was shown that depending on the direction of deflection, the differences between the highest and lowest value of transverse stiffness of a given spring can exceed 25%. The experimental results were compared with the results of the formulas for transverse stiffness available in the literature. It was shown that in the case of springs with a small number of active coils, discrepancies between the average transverse stiffness of a given spring and the transverse stiffness calculated based on literature relations can reach several tens of percent. Analysis of the results of the tests carried out allowed conclusions to be drawn, making it possible to estimate the suitability of a given computational model for determining the transverse stiffness of a spring with given geometrical parameters.

4

Equivalent parameters of metal-elastomer vibroinsulators

Cieplok Grzegorz, Wójcik Kaja, Michalczyk Krzysztof, Sikora Wojciech

Vibrations in Physical Systems

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2020

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Vol. 31, nr 2

art. no. 2020204

EN

This paper concerns a substitute model of the metal-elastomer vibroinsulator that can find use in the mathematical description of vibration machine suspensions. In the case of a plane system, the flexibility matrix of the vibroinsulator was derived and two typical configurations of machine suspensions: symmetrical and asymmetrical, were analysed. For the case of a spatial motion, the elastic matrix of the vibroinsulator and the method of determining its elements was specified. Due to the non-linear character of the vibroinsulator's work, which is caused by large deformations of elastomeric elements under static loads, the analysis was limited to the surroundings of the work point and linear model. The results of theoretical analyses were confirmed by experimental tests.

5

A simple formula for predicting the first natural frequency of transverse vibrations of axially loaded helical springs

Michalczyk Krzysztof, Bera Piotr

Journal of Theoretical and Applied Mechanics

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2019

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Vol. 57 nr 3

779--790

EN

A new formula that allows the first natural frequency of transverse vibrations of axially loaded steel helical springs to be determined has been presented in the paper. The relationship is easy to use and allows finding the first natural frequency of spring vibrations without the necessity of solving analytical or numerical models. According to the authors’ knowledge, this is the first such a formula and, consequently, when this frequency becomes zero, it enables determination of the critical axial force or deflection causing the buckling of the spring. The way of obtaining the described formula is presented in the paper. The results of this formula are compared with those obtained using FEM and experiments. The advantages, drawbacks and limitations of the proposed relationship are also discussed.