TY - JOUR A1 - Azouigui, S. A1 - Silvestri, Z. A1 - Zerrouki, C. A1 - Bouhtiyya, S. A1 - Plimmer, M.D. A1 - Spaltmann, Dirk A1 - Kovalev, Alexander A1 - Woydt, Mathias A1 - Pinot, P. T1 - Angle resolved scattering as a tribological investigation tool for surface characterization JF - Wear N2 - This paper shows how Angle-Resolved Scattering can reveal wear on engineered surfaces. The samples studied, three discs made of steel 100Cr6H used in gear wheels in the automotive industry, were assessed after they had undergone ball-on-disc tests. Scattering maps recorded for spatial frequencies from 0.1 µm-1 to 2.7 µm-1 show a contrast inversion around 0.36 µm-1 revealing the wear trace. Besides measurements of rms roughness, where mean values are 20 nm and 24 nm depending on the locations considered, stationarity and isotropy, we demonstrate the ability of the technique to reveal localized wear on this type of surface in a rapid, robust and convenient way. We show that the tool trace is influenced by the load magnitude rather than by the number of oscillation cycles and highlight the key role played by surface roughness in how the sample responds to wear tests. KW - Surface roughness KW - Angle-resolved scattering KW - Wear KW - Isotropy PY - 2015 DO - https://doi.org/10.1016/j.wear.2014.12.040 SN - 0043-1648 VL - 326-327 SP - 58 EP - 67 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-33021 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Myshkin, N. A1 - Kovalev, Alexander A1 - Spaltmann, Dirk A1 - Woydt, Mathias T1 - Contact mechanics and tribology of polymer composites JF - Journal of applied polymer science N2 - We review contact mechanics with emphasis on the rheological (time dependent) properties of polymers and their relations to surface roughness, material properties, and friction as well as wear behavior of rubbing polymer surfaces. The main concept of polymer mechanics related to tribology consists of three basic elements involved in friction: deformation resulting in the real area of contact of rough surfaces, contact adhesion, and shear and rupture of materials in the contact during the sliding friction. The results of classical work are included, which addresses the real contact area calculation and the description of adhesion interaction between rough surfaces. A brief review of experimental investigations concerning the surface characterization by means of bearing curves, the intermolecular force interaction using the adhesion parameter, the effect of temperature on the real contact area, the formation of transferred polymer film during friction, and tribological behavior of ultrathin polymer layers are presented and their implications discussed. KW - Surfaces and interfaces KW - Friction KW - Wear and lubrication KW - Mechanical properties KW - Microscopy KW - Properties and characterization PY - 2014 DO - https://doi.org/10.1002/APP.39870 SN - 0021-8995 SN - 1097-4628 VL - 131 IS - 3 SP - Article 39870, 1 EP - 9 PB - Wiley InterScience CY - Hoboken, NJ AN - OPUS4-30858 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kovalev, Alexander A1 - Sturm, Heinz T1 - In situ direct observation of adsorption and desorption on a single crystal of 2,4,6-trinitrophenol (TNP) JF - Crystal growth & design N2 - For the first time, we report the direct observation of the nanoscale adsorption and desorption of 2,4,6-trinitrophenol (TNP) molecules on the crystal surface during atomic force microscopy scanning. Our results reveal the position instability of TNP molecules at the border of molecular layers under normal ambient conditions. The observed phenomena are of great interest for exploring the origin of hot-spot generation on the surface of energetic materials. On the basis of the explored properties of TNP crystal, a plausible mechanism of hot-spot formation upon weak initiation at the nanoscale is proposed. KW - Nanoscale adsorption and desorption KW - 2,4,6-trinitrophenol (TNP) KW - Instability of TNP KW - Mechanism of hot-spot formation PY - 2012 DO - https://doi.org/10.1021/cg300366m SN - 1528-7483 VL - 12 IS - 7 SP - 3557 EP - 3564 PB - American Chemical Society CY - Washington, DC, USA AN - OPUS4-26734 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Myshkin, N. A1 - Kovalev, Alexander A1 - Makhovskaya, Y. A1 - Torskaya, E. A1 - Goryacheva, I. T1 - Influence of adhesion induced contact areas on sliding friction JF - Tribology : materials, surfaces & interfaces N2 - Recent developments in micromechanics and nanotribology have made adhesion effects very important in the study of actual contact formation and sliding friction. The present work considers the experimental and simulation data on the formation of the adhesion contact and sliding friction for rough surfaces. The simulation of discrete contact was carried out using the AFM images of topography as a source of real surface geometry at micro/nanoscale. The proposed approach of contact modelling is not using the statistical parameters of roughness, but it provides the estimation of the additional adhesion induced contact areas and their influence on sliding friction. The friction law of Bowden and Tabor was used for validation of simulation and experimental data. Furthermore, the workhardening effect was taken into account in simulation of sliding friction, and this enabled to reach a more successful fit of experimental data. The obtained results of the computer simulations will provide a way of studying the movable contact or at least transition from static to dynamic friction at the micro/nanoscale level. KW - Rough surface KW - Real contact area KW - Adhesion KW - Elastic contact KW - Plastic contact PY - 2010 DO - https://doi.org/10.1179/175158310X12678019274363 SN - 1751-5831 VL - 4 IS - 3 SP - 130 EP - 135 PB - Maney CY - London AN - OPUS4-22231 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kovalev, Alexander A1 - Myshkin, N. A1 - Sturm, Heinz T1 - Influence of adhesion interaction between rough surfaces on real contact area formation T2 - Frühjahrstagung der Deutschen Physikalischen Gesellschaft T2 - Frühjahrstagung der Deutschen Physikalischen Gesellschaft CY - Regensburg, Germany DA - 2010-03-21 PY - 2010 AN - OPUS4-23596 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kovalev, Alexander A1 - Sturm, Heinz T1 - Nanoscale hotspot formation in an energetic material during friction T2 - Jahrestagung der Deutschen Physikalischen Gesellschaft T2 - Jahrestagung der Deutschen Physikalischen Gesellschaft CY - Dresden, Germany DA - 2011-03-13 PY - 2011 AN - OPUS4-23595 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz A1 - Kovalev, Alexander T1 - Nanotribologie an explosionsfähigen Kristallen T2 - 54. Tribologie-Fachtagung - Reibung, Schmierung und Verschleiß - Forschung und praktische Anwendungen N2 - Energetische Materialien enthalten gespeicherte chemische Energie. Diese potentielle Energie kann bei Zündung schlagartig als Strahlungsenergie und Druckerhöhung freigesetzt werden. Nanoskalige Komponenten erhöhen zusätzlich die innere Energie des Materials um den Beitrag der Oberflächenenergie und verbessern die chemische Umsetzung durch bessere Durchmischung. Die hot-spot-Theorie zur Zündung von Explosivstoffen kombiniert mechanische Stimulation und einer dabei zu erreichenden Schwellwert-Energie mit der Temperatur. Wird die Energie zum exothermen Bindungsbruch etwa beim Reibvorgang erreicht entsteht auf der molekularen Skala ein hot-spot. Der Stoff explodiert, wenn der hot-spot ausreichend lange besteht, sich verstärkt und nicht durch Energiedissipation (Festkörperschallausbreitung, Wärmediffusion) verzehrt wird. Rasterkraftmikroskopie (AFM – atomic force microscopy) dient nicht nur zur bildgebenden Vermessung der Topographie und der mechanischen Eigenschaften, sondern kann auch zur gezielten Veränderung der Oberflächen verwendet werden. Solche lithographischen Verfahren bedienen sich im AFM-Kontaktmodus (Scratching Lithography) direkt der Reibung, im hochfrequenten intermittierenden Kontaktverfahren realisiert man einen vibrierenden Kontaktes (Dynamic Plowing Lithography), der beim Eindringen in eigenen Indentationseindruck reibt. In beiden Fällen überträgt man durch Kombination einer Scherbewegung mit einer Variation des Kontaktdrucks Energie auf die Oberfläche, was nachweislich zum chemischen Bindungsbruch z.B. auf Polymeroberflächen führt. Zwei kristalline Explosivstoffe werden untersucht und sowohl dissipative Effekte als auch die Generierung eines hot-spots demonstriert. N2 - Using nanoscale components increase the internal energy by the contribution of surface energy and improve the progress of the chemical reaction. The hot-spot theory of ignition describes the conversion of mechanical energy of friction or impact into heat, leading to exothermal decomposition of the explosive. Thus, it is evident that ignition should be studied on the nanoscale and atomic force microscopy (AFM) provides one of the best solutions to study such behavior. AFM, often used to map a topography image and local mechanical properties on a surface, can also be utilized for carrying lithography, namely scratching lithography or dynamic plowing lithography. In both cases shear stress combined with a variation of contact pressure transfers sufficient energy into the surface to break chemical bonds. Two crystalline explosives are investigated and dissipative processes as well as hot-spot generation are described. During the nanotribological test, the in-situ restructuring of molecular layers under ambient conditions was observed and recorded. T2 - 54. Tribologie-Fachtagung - Reibung, Schmierung und Verschleiß - Forschung und praktische Anwendungen CY - Göttingen, Germany DA - 30.09.2013 KW - Energetische Kristalle KW - Hot spot Theorie PY - 2013 SN - 978-3-00-022603-8 IS - Paper 39 SP - 39/1 EP - 39/11 AN - OPUS4-29457 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kovalev, Alexander A1 - Sturm, Heinz T1 - Observation of nanoscale hot-spot generation on a 2, 4, 6-trinitrophenol (TNP) single crystal JF - Surface science N2 - An energetic material (EM) creates a local thermal point when it accepts energy and the EM will explode due to thermal decomposition when the hot-spot temperature reaches the explosive temperature. The initial stage of the hot-spot formation on 2, 4, 6-trinitrophenol (TNP) single crystal has been observed at the nanometer scale using atomic force microscopy (AFM). The hot-spot generation has been directly initiated by means of an AFM tip. The phenomenon is accompanied by producing agglomerated spherical-like nanoparticles due to a low-temperature decomposition of TNP. It has been observed that the agglomerated particles are produced outside of the stimulated region. The observed decomposition process at the nanoscale doesn't lead to a self-sustaining shock as detonation or explosion. The results are of interest in relation to explore the origin of deformation-induced chemical decomposition or detonation of EM. KW - Energetic material KW - Hot-spot KW - Atomic force microscopy KW - Scratching KW - Dynamic ploughing lithography KW - Nanomanipulation KW - 2, 4, 6-trinitrophenol PY - 2011 DO - https://doi.org/10.1016/j.susc.2011.06.012 SN - 0039-6028 VL - 605 IS - 17-18 SP - 1747 EP - 1753 PB - Elsevier CY - Amsterdam AN - OPUS4-24367 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Kovalev, Alexander A1 - Sturm, Heinz ED - Wang, Q.J. ED - Chung, Y.-W. T1 - Polymer Adhesion T2 - Encyclopedia of tribology N2 - Polymer adhesion is the phenomenon of adhesive-bonded joint formation between polymer material and other solids brought into contact. KW - Adhesion KW - Polymer KW - Contact interaction PY - 2013 SN - 978-0-387-92896-8 SN - 978-0-387-92897-5 SN - 978-0-387-92898-2 DO - https://doi.org/10.1007/978-0-387-92897-5_816 IS - Chapter C SP - 2551 EP - 2556 PB - Springer Science + Business Media CY - New York AN - OPUS4-28972 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Kovalev, Alexander A1 - Myshkin, N.K. ED - Wang, Q.J. ED - Chung, Y.-W. T1 - Polymer contact mechanics T2 - Encyclopedia of tribology N2 - Polymer contact mechanics is an area of contact mechanics focused on the influence of rheological material properties on the contact of polymer solids. KW - Contact mechanics KW - Polymer PY - 2013 SN - 978-0-387-92896-8 SN - 978-0-387-92897-5 SN - 978-0-387-92898-2 DO - https://doi.org/10.1007/978-0-387-92897-5_822 IS - Chapter C SP - 2570 EP - 2577 PB - Springer Science + Business Media CY - New York AN - OPUS4-28974 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -