Janka Majerníková

Prof. Dr. Janka Majerníková

orcid

Research Focus & Metrics

Academic Career Length

14Years (2013-Present)

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

Representative Publications

View All Publications
20 August 2020 in Metals
Verified
Journal Article
Open access
PDF file
PMPeter Mulidrán
Peter Mulidrán
Emil SpišákEmil Spišák
Emil Spišák
MTMiroslav Tomáš
Miroslav Tomáš
Ján SlotaJán Slota
Ján Slota
JMJanka Majerníková
Janka Majerníková
The springback in the sheet metal forming process refers to the change of shape after the load removal. It is usually undesirable, causing problems in the subsequent forming operations, in the assembly and negatively affects the quality of the final product. Numerical prediction of the springback with the use of the numerical simulation is crucial for the reduction of forming tool try-outs, reducing manufacturing costs and increasing the accuracy of the stamped part. In this work, numerical simulation was used for the springback prediction of the hat-shaped part made of advanced high-strength dual-phase steel HCT600X+Z. These numerical predictions were performed with the use of various combinations of material models to try to improve the prediction results. Furthermore, this work includes the proposed springback reduction measure. The reduction of the springback was achieved by the tool design which includes a counterpunch. The springback analysis was carried out in the side view of the formed part; the springback prediction results were compared with the experimental values.

25 June 2020 in Materials
Verified
Journal Article
Open access
PDF file
VMVolodymyr Moravskyi
Volodymyr Moravskyi
AKAnastasiia Kucherenko
Anastasiia Kucherenko
MKMarta Kuznetsova
Marta Kuznetsova
LDLudmila Dulebová
Ludmila Dulebová
Emil SpišákEmil Spišák
Emil Spišák
JMJanka Majerníková
Janka Majerníková
Metal-filled composites based on polypropylene waste have been successfully obtained with an injection molding method of metalized polymer raw materials. Using the model polymer, the peculiarities of the formation of the copper layer in solutions of chemical metallization on the polypropylene surface were investigated and the main factors influencing this process were established. The main influence on the rate of reduction of copper in solutions of chemical metallization has the concentration of copper sulfate, sodium hydroxide, and EDTA-Na2. It was shown that the efficiency of the copper plating process also strongly depends on polymer processing, which follows the activation. In case of the use of simple activation, it is not possible to obtain metalized raw materials with high efficiency. Additional processing of activated polymer raw materials is required to carry out the process with high efficiency. The amount of reduced copper on the polymer surface can be adjusted by changing the concentration of the components of the chemical metallization solution, as well as the degree of loading of the polymer raw material. Examination by electron scanning microscopy of the obtained metalized polypropylene showed that the copper coating on the polymer particles is formed with a high degree of surface coverage. The formed copper coating is free of copper oxides, which is confirmed by X-ray diffraction studies and analysis of the spectrum of characteristic X-rays. Metal-filled composites have been characterized by the effect of copper on mechanical and rheological (MFR) properties. The Differential Scanning Calorimetry (DSC) and Thermogravimetric (TG) methods show a certain effect of metal on the magnitude of thermal effects and the rate of weight loss.

11 April 2022 in Applied Sciences
Verified
Journal Article
Open access
PDF file
GMGerhard Mitaľ
Gerhard Mitaľ
Ivan GajdošIvan Gajdoš
Ivan Gajdoš
Emil SpišákEmil Spišák
Emil Spišák
JMJanka Majerníková
Janka Majerníková
TJTomáš Jezný
Tomáš Jezný
This study investigates how layer deposition in printing 3D models made of polyetherimide (PEI) using the fused filament fabrication (FFF) technique affects resistance of these models to abrasive wear. Samples made by additive manufacturing with different setting of build orientation and path generation strategy of extruded fibers were used in the experiment. The experiments were conducted on a tribometer according to the ASTM G65-16 standard. The friction force, normal force, and temperature in the contact area during the tribometer operation were measured using a strain gauge sensor. The tribometer allowed us to perform the tribological experiments using a rubber-coated or a metal disc without a lubricant in the so-called “dry” operation. Following the ASTM G65-16 standard, a rubber-coated disc and Fe3Al2 (SiO4)3 garnet abrasive were used for the wear resistance tests. The analysis of experimental data showed correlations among orientation selection, the strategy of layer deposition by the FFF technique, and the surface life in terms of abrasive wear. The results of this research also showed the suitability of the chosen building orientation and deposition strategy for part production by additive manufacturing, depending on the required tribological properties, such as the coefficient of friction (yield path) and wear behavior. Based on the results of the study, it is concluded that continuity of wear and friction force depends on the path traveled under the model production orientation. The size of wear (material loss) ranged from 0.451–0.809%. It was shown that the weight loss of the sample under loading was greater, on average, with the chosen fiber orientation strategy in the Z direction than in the X direction.

13 January 2023 in Materials
Verified
Journal Article
Open access
PDF file
PMPeter Mulidrán
Peter Mulidrán
Emil SpišákEmil Spišák
Emil Spišák
MTMiroslav Tomáš
Miroslav Tomáš
JMJanka Majerníková
Janka Majerníková
Jana BidulskáJana Bidulská
Jana Bidulská
RBRóbert Bidulský
Róbert Bidulský
Formability and its prediction of high-strength steels is an important research subject for forming specialists and researchers in this field. Springback and its accurate prediction of high-strength steels are very common issues in metal forming processes. In this article, the impact of blank holding force and friction on the parts springback made of dual-phase steel was studied. Numerical predictions of the springback effect were conducted using nine combinations of yield criteria and hardening rules. Results from experiments were evaluated and compared with results from numerical simulations. The use of lower blank holding forces and PE foil can reduce springback by a significant amount. Numerical simulations where the Yoshida-Uemori hardening rule was applied produced more accurate springback prediction results compared to simulations that used Krupkowski and Hollomon’s isotropic hardening rules in number of cases.

21 November 2017 in Metals
Verified
Journal Article
Open access
PDF file
MDMiroslav Džupon
Miroslav Džupon
Ľuboš KaščákĽuboš Kaščák
Ľuboš Kaščák
Emil SpišákEmil Spišák
Emil Spišák
RKRené Kubík
René Kubík
JMJanka Majerníková
Janka Majerníková
A clinching method that uses a simple toolset consisting of a punch and a die, is utilized for joining lightweight materials. This paper is aimed at investigating the wear of the die cavity of a clinching tool. A clinching tool with a specially shaped cavity was used for joining thin hot-dip galvanized steel sheets. Various types of physical vapour deposition (PVD) coatings such as ZrN, CrN and TiCN were deposited on the shaped surface of the die using Lateral Rotating Arc-Cathodes technology. Hot-dip galvanized steel sheets were used for testing the clinching tool. The material properties of PVD coatings that were deposited on the shaped part of the clinching die were evaluated. Finite Element Analysis was used to localize the area of the shaped part of the die and the part of surface area of the cylindrical die cavity of ϕ 5.0 mm, in which high contact pressure values were predicted. The prediction of the start of the wear cycle was verified experimentally by the clinching of 300 samples of hot-dip galvanized steel sheets. Unlike the CrN and ZrN coatings, the TiCN coating remained intact on the entire surface of the die.

7 December 2023 in Polymers
Verified
Journal Article
Open access
PDF file
Emil SpišákEmil Spišák
Emil Spišák
ENEma Nováková-Marcinčínová
Ema Nováková-Marcinčínová
JMJanka Majerníková
Janka Majerníková
PMPeter Mulidrán
Peter Mulidrán
ĽNĽudmila Nováková-Marcinčínová
Ľudmila Nováková-Marcinčínová
This article is focused on a mechanical properties investigation of three types of sustainable poly lactic acid materials manufactured using the fused filament fabrication process. The purpose of this work was to study the impact of printing strategies on the mechanical properties and predict mechanical behavior under tensile loading using finite element analysis. The testing of mechanical properties was conducted according to the ISO 527 standard. The numerical simulations were conducted in Simufact Forming 2022 software. Analysis of the experimental data showed a dependance of mechanical properties on the used printing strategy. The Clear PLA samples printed in the XY plane exhibited a 43% reduction in tensile strength and a 49% reduction in elongation compared to samples printed from the same material in YZ plane. The experimental results show the influence of the printing orientation on the mechanical properties of 3D-printed samples.