Ivan Kopal

Prof. Ivan Kopal

orcid

Research Focus & Metrics

Academic Career Length

11Years (2016-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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21 June 2019 in Polymers
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Journal Article
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IKIvan Kopal
Ivan Kopal
Marta HarničárováMarta Harničárová
Marta Harničárová
Jan ValíčekJan Valíček
Jan Valíček
Jan KrmelaJan Krmela
Jan Krmela
OLOndrej Lukáč
Ondrej Lukáč
The presented work deals with the creation of a new radial basis function artificial neural network-based model of dynamic thermo-mechanical response and damping behavior of thermoplastic elastomers in the whole temperature interval of their entire lifetime and a wide frequency range of dynamic mechanical loading. The created model is based on experimental results of dynamic mechanical analysis of the widely used thermoplastic polyurethane, which is one of the typical representatives of thermoplastic elastomers. Verification and testing of the well-trained radial basis function neural network for temperature and frequency dependence of dynamic storage modulus, loss modulus, as well as loss tangent prediction showed excellent correspondence between experimental and modeled data, including all relaxation events observed in the polymeric material under study throughout the monitored temperature and frequency interval. The radial basis function artificial neural network has been confirmed to be an exceptionally high-performance artificial intelligence tool of soft computing for the effective predicting of short-term viscoelastic behavior of thermoplastic elastomer systems based on experimental results of dynamic mechanical analysis.

9 February 2022 in Polymers
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IKIvan Kopal
Ivan Kopal
ILIvan Labaj
Ivan Labaj
JVJuliána Vršková
Juliána Vršková
Marta HarničárováMarta Harničárová
Marta Harničárová
Jan ValíčekJan Valíček
Jan Valíček
Zuzana PalkovaZuzana Palkova
Zuzana Palkova
In this study, a new generalized regression neural network model for predicting the curing characteristics of rubber blends with different contents of carbon black filler cured at various temperatures is proposed for the first time The carbon black contents in the rubber blend and cure temperature were used as input parameters, while the minimum and maximum elastic torque, scorch time, and optimal cure time, obtained from the analysis of 11 rheological cure curves registered at 10 various temperatures, were considered as output parameters of the model. A special pre-processing procedure of the experimental input and target data and the training algorithm is described. Less than 55% of the experimental data were used to significantly reduce the total number of input and target data points needed for training the model. Satisfactory agreement between the predicted and experimental data, with a maximum error in the prediction not exceeding 5%, was found. It is concluded that the generalized regression neural network is a powerful tool for intelligently modelling the curing process of rubber blends even in the case of a small dataset, and it can find a wide range of practical applications in the rubber industry.

9 June 2018 in Polymers
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IKIvan Kopal
Ivan Kopal
ILIvan Labaj
Ivan Labaj
Marta HarničárováMarta Harničárová
Marta Harničárová
Jan ValíčekJan Valíček
Jan Valíček
DHDušan Hrubý
Dušan Hrubý
The precise experimental estimation of mechanical properties of rubber blends can be a very costly and time-consuming process. The present work explores the possibilities of increasing its efficiency by using artificial neural networks to study the mechanical behavior of these widely used materials. A multilayer feed-forward back-propagation artificial neural network model, with a strain and the carbon black content as input parameters and stress as an output parameter, has been developed to predict the uniaxial tensile response of vulcanized natural rubber blends with different contents of carbon black in the form of engineering stress-strain curves. A novel procedure has been created for the simulation of the optimized artificial neural network model with input datasets generated by a regression model of an experimental dependence of tensile strain-at-break on the carbon black content in the investigated blends. Errors of the prediction of experimental stress-strain curves, as well as of tensile strain-at-break, tensile stress-at-break and M100 tensile modulus were estimated for all simulated stress-strain curves. The present study demonstrated that the performance of a developed neural network model to predict the stress-strain curves of rubber blends with different contents of carbon black is also exceptionally high in the case of a network that had never learned the input data, which makes it a suitable tool for extensive use in practice.

28 November 2018 in Materials
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Journal Article
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IKIvan Kopal
Ivan Kopal
JVJuliána Vršková
Juliána Vršková
ILIvan Labaj
Ivan Labaj
DODarina Ondrušová
Darina Ondrušová
PHPeter Hybler
Peter Hybler
Milena KušnerováMilena Kušnerová
Milena Kušnerová
Irradiation by ionizing radiation is a specific type of controllable modification of the physical and chemical properties of a wide range of polymers, which is, in comparison to traditional chemical methods, rapid, non-polluting, simple, and relatively cheap. In the presented paper, the influence of high-energy ionizing radiation on the basic mechanical properties of the melamine resin, phenol-formaldehyde resin, and nitrile rubber blend has been studied for the first time. The mechanical properties of irradiated samples were compared to those of non-irradiated materials. It was found that radiation doses up to 150 kGy improved the mechanical properties of the tested materials in terms of a significant increase in stress at break, tensile strength, and tensile modulus at 40% strain, while decreasing the value of strain at break. At radiation doses above 150 kGy, the irradiated polymer blend is already degrading, and its tensile characteristics significantly deteriorate. An radiation dose of 150 kGy thus appears to be optimal from the viewpoint of achieving significant improvement, and the radiation treatment of the given polymeric blend by a beam of accelerated electrons is a very promising alternative to the traditional chemical mode of treatment which impacts the environment.

30 April 2016 in International Journal of Materials Research
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IKIvan Kopal
Ivan Kopal
DBDana Bakošová
Dana Bakošová
PKPavel Koštial
Pavel Koštial
ZJZora Jančíková
Zora Jančíková
JVJan Valíček
Jan Valíček
MHMarta Harničárová
Marta Harničárová
In this paper, a stiffness–temperature model based on Weibull statistics was applied to quantitatively describe changes in the storage modulus of thermoplastic polyurethane over a wide range of temperature. The variation of the storage modulus with temperature was obtained from dynamic mechanical analysis tests across transition temperatures. Both the physical and statistical parameters of the applied model were estimated in the process of parametric fitting of the model to the storage modulus versus a temperature curve by using a trust region algorithm for a robust nonlinear least squares method. Good agreement between the modeled and experimental data has been found over the entire investigated temperature range, including all observed relaxation transitions.

2 September 2023 in Polymers
Verified
Journal Article
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IKIvan Kopal
Ivan Kopal
ILIvan Labaj
Ivan Labaj
JVJuliána Vršková
Juliána Vršková
Marta HarničárováMarta Harničárová
Marta Harničárová
Jan ValíčekJan Valíček
Jan Valíček
Hakan TozanHakan Tozan
Hakan Tozan
Modelling the flow properties of rubber blends makes it possible to predict their rheological behaviour during the processing and production of rubber-based products. As the nonlinear nature of such complex processes complicates the creation of exact analytical models, it is appropriate to use artificial intelligence tools in this modelling. The present study was implemented to develop a highly efficient artificial neural network model, optimised using a novel training algorithm with fast parallel computing to predict the results of rheological tests of rubber blends performed under different conditions. A series of 120 real dynamic viscosity–time curves, acquired by a rubber process analyser for styrene–butadiene rubber blends with varying carbon black contents vulcanised at different temperatures, were analysed using a Generalised Regression Neural Network. The model was optimised by limiting the fitting error of the training dataset to a pre-specified value of less than 1%. All repeated calculations were made via parallel computing with multiple computer cores, which significantly reduces the total computation time. An excellent agreement between the predicted and measured generalisation data was found, with an error of less than 4.7%, confirming the high generalisation performance of the newly developed model.