Ing. Petr Šperka, Ph.D.
E-mail:   sperka@fme.vutbr.cz  WWW:   http://scholar.google.cz/citations?user=PSnPIhEAAAAJ Dept.:   Institute of Machine and Industrial Design Dept. of Tribology Position:   Assistant Professor Room:   A3/508

Supervised courses:

• Selected chapters from machine design - machine elements (0KS)

Publications:

• POŘÍZKA, P.; ROČŇÁKOVÁ, I.; KLUS, J.; PROCHAZKA, D.; SLÁDKOVÁ, L.; ŠPERKA, P.; SPOTZ, Z.; ČELKO, L.; NOVOTNÝ, K.; KAISER, J.:
  Estimating the grade of Mg corrosion using Laser-Induced Breakdown Spectroscopy, Royal Society of Chemistry
  journal article in Web of Science
• KOŠŤÁL, D.; NEČAS, D.; ŠPERKA, P.; SVOBODA, P.; KŘUPKA, I.; HARTL, M.:
  Lubricant Rupture Ratio at Elastohydrodynamically Lubricated Contact Outlet, Springer
  journal article in Web of Science
• ŠPERKA, P.; KŘUPKA, I.; HARTL, M.:
  Evidence of Plug Flow in Rolling-Sliding Elastohydrodynamic Contact, SPRINGER/PLENUM PUBLISHERS
  journal article in Web of Science
• BIBOULET, N.; ŠPERKA, P.; VENNER, CH.; LUBRECHT, T.; KŘUPKA, I.:
  Obtaining the pressure spike and maximum shear stress from optical interferometry data,
  Tribology International, Vol.65, (2013), No.6, pp.1-7, ISSN 0301-679X, Elsevier
  journal article - other
• BAIR, S.; ŠPERKA, P.; KŘUPKA, I.; HARTL, M.:
  Quantitative elastohydrodynamic film thickness of mechanically degraded oil,
  Tribology International, Vol.65, (2013), No.8, pp.33-38, ISSN 0301-679X, Elsevier
  journal article - other
• VRBKA, M.; NÁVRAT, T.; KŘUPKA, I.; HARTL, M.; ŠPERKA, P.; GALLO, J.:
  Study of film formation in bovine serum lubricated contacts under rolling/sliding conditions, SAGE Publications Ltd
  journal article in Web of Science
• ŠPERKA, P.; KŘUPKA, I.; HARTL, M.:
  Prediction of Real Rough Surface Deformation in Pure Rolling EHL Contact: Comparison with Experiment,
  TRIBOLOGY TRANSACTIONS, Vol.55, (2012), No.5, pp.698-704, ISSN 1040-2004, Taylor & Francis
  journal article - other
• ŠPERKA, P.; KŘUPKA, I.; HARTL, M.:
  The Behavior of Surface Roughness in EHL Contacts Under Small Slide to Roll Ratios, Springer
  journal article in Web of Science
• ŠPERKA, P.; KŘUPKA, I.; HARTL, M.:
  Experimental study of real roughness attenuation in rolling-sliding concentrated contacts, Elsevier
  journal article in Web of Science
• VAVERKA, M.; VRBKA, M.; FICZA, I.; ŠPERKA, P.:
  Numerical Investigation of the Influence of Surface Asperities on Tribological Parameters in Lubricated Point Contact,
  Proceedings of the International Conference BALTTRIB 2011, pp.117-121, ISBN 978-609-449-006-4, (2011), Aleksandras Stulginskis University
  conference paper
  akce: BALTTRIB'2011, Kaunas, 17.11.2011-19.11.2011
• ŠPERKA, P.; KŘUPKA, I.; HARTL, M.:
  Experimental study of artificial features attenuation in rolling/sliding concentrated contacts,
  ASME/STLE 2011 International Joint Tribology Conference, pp.135-137, ISBN 978-0-7918-5474-7, (2011), ASME/STLE
  conference paper
  akce: ASME/STLE 2011 International Joint Tribology Conference, Los Angeles, 2011, Los Angeles, CA, 24.10.2011-26.10.2011
• SVOBODA, P.; VRBKA, M.; ŠPERKA, P.; KŘUPKA, I.; HARTL, M.:
  Study of Lubrication Film Formation in Ball Bearings Under Starved Conditions,
  ASME/STLE 2011 International Joint Tribology Conference, pp.183-185, ISBN 978-0-7918-5474-7, (2011), American Society of Mechanical Engineers, Tribology Division, TRIB
  conference paper
  akce: ASME/STLE 2011 International Joint Tribology Conference, Los Angeles, 2011, Los Angeles, CA, 24.10.2011-26.10.2011
• VRBKA, M.; KŘUPKA, I.; SVOBODA, P.; ŠPERKA, P.; NÁVRAT, T.; HARTL, M.; NOHAVA, J.:
  Effect of shot peening on rolling contact fatigue and lubricant film thickness within mixed lubricated non-conformal rolling/sliding contacts,
  Tribology International, Vol.44, (2011), No.12, pp.1726-1735, ISSN 0301-679X, Elsevier
  journal article - other
• SHEN, XJ.; CHEN, XY.; ŠPERKA, P.; KŘUPKA, I.; HARTL, M.:
  Effect of real longitudinal surface roughness on lubrication film formation within line elastohydrodynamic contact,
  Tribology International, Vol.44, (2010), No.3, pp.1-6, ISSN 0301-679X, Elsevier
  journal article - other
• VRBKA, M.; ŠAMÁNEK, O.; ŠPERKA, P.; NÁVRAT, T.; KŘUPKA, I.; HARTL, M.:
  Effect of surface texturing on rolling contact fatigue within mixed lubricated non-conformal rolling/sliding contacts, Elsevier
  journal article in Web of Science
• ŠPERKA, P.; KŘUPKA, I.; HARTL, M.:
  Experimental study of real roughness attenuation in concentrated contacts,
  Tribology International, Vol.42, (2009), No.12, pp.1-9, ISSN 0301-679X, Elsevier
  journal article - other

List of publications at Portal BUT

Abstracts of most important papers:

• KOŠŤÁL, D.; NEČAS, D.; ŠPERKA, P.; SVOBODA, P.; KŘUPKA, I.; HARTL, M.:
  Lubricant Rupture Ratio at Elastohydrodynamically Lubricated Contact Outlet, Springer
  journal article in Web of Science
  Elastohydrodynamically lubricated (EHL) contacts rarely exist as single contacts. Multiple contacts or single contacts subjected to the repeated over-rolling represent more often the case in practical applications. A typical example is the rolling element bearing. A lubricant rupture mechanism at each contact outlet determines the lubricant availability to the succeeding contact. This work presents a quantitative description of the lubricant film thickness rupture in EHL contact outlet with the use of the fluorescent microscopy. A rupture ratio of the film thickness between two diverging surfaces exiting the contact was measured for both pure rolling and rolling–sliding conditions. The influence of variation of several parameters such as lubricant properties, rolling speed or rolling element ellipticity to the lubricant rupture ratio was investigated. Understanding of the physical phenomena of the lubricant rupture extends further possibilities in both experimental and theoretical researches of the starved EHL.
• WANG, J.; LUBRECHT, AA.; ŠPERKA, P.; OMASTA, M.; KANETA, M.:
  Effect of high slide-roll ratio on thermal elastohydrodynamic lubrication in line contacts with surface waviness, Sage
  journal article in Web of Science
  In this study, the effect of high slide-roll ratio on thermal elastohydrodynamic lubrication in line contacts is explored numerically. The surface dimple produced by the heat transportation of the surface is explained. Furthermore, the deformation of the surface waviness under zero entrainment velocity is analyzed. The results show that, under high slide-roll ratios, similar to those under rolling or rolling–sliding conditions, the deformation of the surface waviness depends on the slide-roll ratio and the wavelength of the harmonic waviness.
• JANALIK, P.; FICHTER, T.; ŠPERKA, P.; OMASTA, M.; RAUSER, P.:
  Three-dimensional optical assessment of experimental iatrogenic mechanical damage to canine dental enamel caused by a sonic scaler, CZECH ACADEMY AGRICULTURAL SCIENCES
  journal article in Web of Science
  Removal of dental calculus deposits is one of the basic parts of professional dental cleaning. Despite the popularity of power-driven scalers, several risks are associated with their use, mechanical damage of the enamel surface being one of the most important. The present study evaluated enamel damage caused by a sonic scaler in different work patterns to quantify the damage and allow a clear comparison. Seventy-five canine teeth were carefully extracted from twenty-three dogs. The scaler was used on a clean surface with several combinations of time (five to twenty seconds) and parts of the scaler (point vs. side of the tip). Subsequently, damaged surface topography was mapped using three-dimensional optical microscopy. The results revealed a high variance in defect depth which was influenced by both factors. Statistical assessment confirmed highly significant (P < 0.001) or at least significant (P < 0.05) differences in data acquired for each group. As expected, the shallowest defects were produced by the scaler side in the shortest experimental period (five seconds). Point use proved to be quite damaging, as it resulted in approximately four times higher median values than the side in the same timeframe. Therefore, it is crucial to follow all safety precautions when handling a power-driven scaler even during routine treatments. Use of the side of the tip and constant movement on the tooth surface are essential to reduce the risk of enamel damage.
• ŠPERKA, P.; KŘUPKA, I.; HARTL, M.:
  Evidence of Plug Flow in Rolling-Sliding Elastohydrodynamic Contact, SPRINGER/PLENUM PUBLISHERS
  journal article in Web of Science
  This paper presents experimental results that point out on irregular distribution of through-film speed profile. The observations show an existence of cohesive core of entrainment speed surrounded by two shear zones located closely to the surfaces. This result represents experimental evidence for plug flow mechanism in highly loaded rolling-sliding elastohydrodynamic contact. Possible mechanisms of shear localization are discussed.
• BIBOULET, N.; ŠPERKA, P.; VENNER, CH.; LUBRECHT, T.; KŘUPKA, I.:
  Obtaining the pressure spike and maximum shear stress from optical interferometry data,
  Tribology International, Vol.65, (2013), No.6, pp.1-7, ISSN 0301-679X, Elsevier
  journal article - other
  In order to predict and optimise highly loaded contact performance, accurate lubricant data is crucial. The lubricants high-pressure rheological behaviour is by far the least known parameter. However, this is the key factor to realistic modeling of non-Newtonian Elasto-Hydrodynamic lubrication. In this paper a new approach is described to extract such data from optical interferometric film thickness measurements of EHL contacts. The approach is relatively straightforward and cheap compared to out of contact rheological experiments using specialized equipment