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Kottfer D.,Technical University of Kosice | Ferdinandy M.,Slovak Academy of Sciences | Kaczmarek L.,University of Lodz | Hvizdos P.,Slovak Academy of Sciences | Kuffova M.,Armed Forces Academy of General Milan Rastislav Stefanik
Advances in Military Technology | Year: 2014

Mechanical and tribological properties of Ti coating deposited by physical vapour deposition (PVD) technique using electron beam to activate evaporation of Ti onto steel OKhN3MFA are evaluated. The thickness and grain growth direction are assessed by means of scanning with an electron microscopy, chemical composition of both the coating and substrate are measured using EDX. The coefficient of friction (COF) and wear was evaluated by a Pin-on-disc test. The wear of the coating was expressed as a loss of material (volume and mass) after the Pin-on-disc test. Hardness and Young’s modulus were found to be from 3.8 GPa to 7.6 GPa and from 65 GPa to 200 GPa, respectively. The measured values of the studied properties were compared with the literature data for Ti PVD coatings. © 2014, University of Defence. Source

Celko P.,Alexander Dubcek University, Trencin | Kuffova M.,Armed Forces Academy of General Milan Rastislav Stefanik
Transactions of the Institute of Metal Finishing | Year: 2016

With potential practical applications of the outcomes of this study in the automotive industry, the present work aims at assessing the effect of 20-hour plasma-nitriding on fatigue resistance of 50CrV4 low-alloy steel samples. The quenched and tempered low-alloy steel samples underwent plasma-nitriding at 500°C using a hydrogen-to-nitrogen flow-rate ratio of 24:8. The quenched and tempered plasma-treated steel samples, and quenched and tempered steel samples that did not undergo plasma-nitriding, were characterised by metallurgical and microstructural analyses. Micro-hardness to Vickers (HV0.05), surface hardness to Vickers (HV1, HV5 and HV10, respectively) and rotating bending up to 107 cycles at a frequency of 154 Hz were tested and the results evaluated. The improvement in the fatigue limit (σC) as a result of 20 hours of plasma-nitriding exceeded 55%. © 2016 Institute of Materials Finishing. Source

Kuffova M.,Armed Forces Academy of General Milan Rastislav Stefanik | Necas P.,Slovak Academy of Sciences
Advances in Military Technology | Year: 2011

Modern societies have become highly dependent on modern technology. Without its tools, their economies can no longer be run and their infrastructure would collapse. Thus technology has offered a high and sophisticated standard of living to societies, but at the same time it has introduced an inherent vulnerability. The efficient Automatic Dynamic Incremental Nonlinear Analysis (ADINA) is a Finite Element Method (FEM) based system, very suitable for solving large variety of personnel security problems; observing construction material processing and growth of fatigue damage, crack propagation and the distribution of stress fields. Leveraged by simulated fracture and damage of material models, it is the catalyst of the problem-solution roadmap towards substantial material cracks elimination. Source

Kuffova M.,Armed Forces Academy of General Milan Rastislav Stefanik | Necas P.,Slovak Academy of Sciences
Acta Polytechnica Hungarica | Year: 2010

The paper presented focuses on fatigue crack growth observation in the microstructure of magnesium alloy AZ 91D using finite element software ADINA. ADINA offers a wide range of capabilities based on reliable and efficient finite element procedures. For this reason, ADINA is often chosen for applications where reliability and safety is of critical importance in different industries such as biomedical, automotive, nuclear, forming, civil engineering, hi-tech and others, e.g., in the dynamic analysis of bridge structures - earthquake analysis, in biomedical applications, in the design of nuclear reactors or in studies on safety. This work shows efficiency and good correlation between experimental and numerical results and verifies this program for its utilization in the field of fatigue endurance determination and evaluation. Source

Necas P.,Armed Forces Academy of General Milan Rastislav Stefanik | Kelemen M.,Armed Forces Academy of General Milan Rastislav Stefanik | Lippay B.,Dvojkrizna 2
Komunikacie | Year: 2011

The purpose of this article is to identify differences in the perception of the US foreign and security policy by the first and the second Bush presidency. Due to the fact that both presidencies of George W. Bush were strongly influenced by neoconservative view on the US role in the World, the first chapter is dedicated to the impact of neoconservativism on foreign and security policy of President George W. Bush. Finally, it introduces reader to basic principles of President's Bush foreign and security policy implemented after September 11 terrorist attacks. The second chapter is the core chapter. It compares two major documents of Bush Administrations, which materialized his foreign and security policies. These are National Security Strategy 2002 and National Security Strategy 2006. Source

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