Ing. Libor Nohál, Ph.D.
E-mail:   nohal@fme.vutbr.cz  Dept.:   Institute of Machine and Industrial Design Dept. of Tribology Position:   Research Worker

Publications:

• NOHÁL, L.; HORT, F.; DVOŘÁČEK, J.; MAZAL, P.:
  An Experimental Investigation of Rolling Contact Fatigue of Steels Using Acoustic Emission Method,
  INSIGHT, Vol.55, (2013), No.12, pp.665-669, ISSN 1354-2575, BINDT
  journal article - other
• NOHÁL, L.; HORT, F.; MAZAL, P.:
  An Experimental Study on Damage Monitoring of Rolling Bearings Using Acoustic Emission Method,
  The Tenth International Conference on Condition Monitoring and Machinery Failure Prevention Technologies, pp.1-9, ISBN 978-1-901892-37-6, (2013), The British Institute of NDT
  conference paper
  akce: CM 2013 and MFPT 2013 The Tenth International Conference on Condition Monitoring and Machinery Failure Prevention Technologies, Kraków, 18.06.2013-20.06.2013
• MAZAL, P.; PAZDERA, L.; NOHÁL, L.; TOPOLÁŘ, L.:
  Netradiční aplikace metody akustické emise,
  ISBN 978-80-214-4629-8, (2012), VUT v Brně
  book
• MAZAL, P.; NOHÁL, L.; ČERNÝ, M.; ČERMÁK, J.:
  Measurements of Acoustic Emission in Evaluating of Sap Flow in Trees, INT SOC HORTICULTURAL SCIENCE
  journal article in Web of Science
• ČERNÝ, M.; MAZAL, P.; NOHÁL, L.:
  POTENCIALS OF SAP FLOW EVALUATION BY MEANS OF ACOUSTIC EMISSION MEASUREMENTS,
  Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, Vol.59, (2011), No.6, pp.1-6, ISSN 1211-8516, Mendelova univerzita
  journal article - other
• NOHÁL, L.; MAZAL, P.:
  Investigation of Fatigue Process in Aluminium Alloys Using Nondestructive Methods,
  VIth Workshop "NDT in Progress", pp.193-198, ISBN 978-80-214-4339-6, (2011), CNDT, VUT
  conference paper
  akce: VIth Workshop "NDT in Progress", Průhonice, 10.10.2011-12.10.2011
• VLAŠIC, F.; MAZAL, P.; NOHÁL, L.; LIŠKUTÍN, P.:
  ACOUSTIC EMISSION METHOD AND X-RAY DIFFRACTION AS INSTRUMENTS FOR EVALUATION OF MATERIAL DEGRADATION,
  Metal 2011 - 20th Anniversary International Conference on Metallurgy and Materials, pp.123-124, ISBN 978-80-87294-22-2, (2011), Tanger, Ostrava
  conference paper
  akce: Metal 2011 - 20. mezinárodní konference metalurgie a materiálů, Brno, 18.05.2011-20.05.2011

List of publications at Portal BUT

Abstracts of most important papers:

• NOHÁL, L.; HORT, F.; DVOŘÁČEK, J.; MAZAL, P.:
  An Experimental Investigation of Rolling Contact Fatigue of Steels Using Acoustic Emission Method,
  INSIGHT, Vol.55, (2013), No.12, pp.665-669, ISSN 1354-2575, BINDT
  journal article - other
  Rolling-element bearings are widely used machine components and their failure can result in damage to the whole machine. A bearing failure can be caused by many factors such as improper lubrication, presence of abrasive particles, overloading, moisture, corrosive environment, improper mounting, electrical discharges and material defects. These causes can be eliminated by observance of correct operating conditions, except rolling contact fatigue (RCF). For this reason, the full-scale bearing life tests or material tests for RCF resistance are performed. Various methods of condition monitoring are used to detect damage of these components or specimens in the industry or during testing in laboratories. An analysis of vibrations from tested bearings/specimens is the most widely used method for damage detection and is based on vibration acceleration measurement and its analysis in the time or frequency domain. A more sensitive method for surface damage or subsurface crack detection is the acoustic emission (AE) method. Over the past three decades, the AE based monitoring has developed as a potential tool for rolling bearing diagnostics. This paper is aimed on detection and monitoring of onset and propagation of natural defects of steel specimens using the AE technology. The experiments were carried out under various loading conditions on specimens of case-hardening steel 16MnCr5. The AE signal parameters such as count rate, cumulative count rate and RMS were compared with vibration levels and temperature. In conclusion, the results of this study suggest that the AE monitoring method can be employed as an evaluation tool for rolling contact fatigue testing of material specimens.
• NOHÁL, L.; HORT, F.; MAZAL, P.:
  An Experimental Study on Damage Monitoring of Rolling Bearings Using Acoustic Emission Method,
  The Tenth International Conference on Condition Monitoring and Machinery Failure Prevention Technologies, pp.1-9, ISBN 978-1-901892-37-6, (2013), The British Institute of NDT
  conference paper
  akce: CM 2013 and MFPT 2013 The Tenth International Conference on Condition Monitoring and Machinery Failure Prevention Technologies, Kraków, 18.06.2013-20.06.2013
  The aim of condition monitoring of rotating machinery is generally fault detection, determine its severity and prediction of remaining life of the component. Rolling-element bearings are a significant component of machines and its fault leads to critical malfunction. Various methods of condition monitoring are used to detect a damage of these components in the industry or during testing in laboratories. Conducting an endurance test series ensures an experimental data for bearing life estimation. An analysis of vibrations from tested bearings is the most widely used method for damage detection based on vibration acceleration measurement and its analysis in time or frequency domain. However, the bearing fault diagnostic using acoustic emission (AE) method is more sensitive to incipient defects than commonly used vibration-based methods. Over the past three decades, the AE based monitoring has developed as a potential tool for rolling bearing diagnostics. This paper focuses on detection and monitoring of initiation and propagation of natural defects of the grease lubricated thrust ball bearings using the AE technology. The monitoring was focused on upper ring that was replaced with a material specimen. The experiments were carried out under various loading conditions and the signal parameters such as count rate, cumulative count rate, energy and RMS were compared. In conclusion, the results from this study suggest that the AE monitoring method can be employed as a control tool for rolling contact fatigue testing of material specimens.
• MAZAL, P.; PAZDERA, L.; NOHÁL, L.; TOPOLÁŘ, L.:
  Netradiční aplikace metody akustické emise,
  ISBN 978-80-214-4629-8, (2012), VUT v Brně
  book
  The monography describes the contemporary methods of application options in the area of acoustic emission diagnosis of rotating machinery parts, the quality control in the field of welding, construction and selected areas of the biological sciences.
• MAZAL, P.; NOHÁL, L.; ČERNÝ, M.; ČERMÁK, J.:
  Measurements of Acoustic Emission in Evaluating of Sap Flow in Trees, INT SOC HORTICULTURAL SCIENCE
  journal article in Web of Science
  This article deals with measurement techniques of water conducting system in the trees. Water conducting system (including xylem and phloem) indicates its importance for related physiological processes. However, there are still problems how to measure its functioning (which variables and how), especially in the open field (e. g., forests and orchards) in order to get maximum information about it. In this study we focused on a general description of acoustic events measurable in a wide range of their spectrum (acoustic emission method). The first aim was to detect such signals and the second to learn them and gradually analyze in order to better understand the associated processes causing their occurrence and their relations to plant life.
• VLAŠIC, F.; MAZAL, P.; NOHÁL, L.; LIŠKUTÍN, P.:
  ACOUSTIC EMISSION METHOD AND X-RAY DIFFRACTION AS INSTRUMENTS FOR EVALUATION OF MATERIAL DEGRADATION,
  Metal 2011 - 20th Anniversary International Conference on Metallurgy and Materials, pp.123-124, ISBN 978-80-87294-22-2, (2011), Tanger, Ostrava
  conference paper
  akce: Metal 2011 - 20. mezinárodní konference metalurgie a materiálů, Brno, 18.05.2011-20.05.2011
  The paper deals mainly with measurement and evaluation of acoustic emission signal (AE) in continues monitoring of surface strengthened wrought aluminium alloy EN AW-2017A/T4 using X-ray diffraction topography. Other models and approaches to evaluating the results of the AE signal, which are essential to identify the microscopic processes occurring in the structure of the material throughout the fatigue process are presented here. Non-destructive observation using X-ray diffraction (XRD) is focused primarily on the phase changes of mechanical properties where the AE signal showed increased activity. The main principle of the X-ray technique is to record directional distribution of mosaics blocks which are changed periodically by cyclic loading of the material. The measurements are supplemented by the record of resonant frequency changes of loading device RUMUL Cracktronic.