TY - JOUR A1 - Cappella, Brunero A1 - Hartelt, Manfred A1 - Wäsche, Rolf T1 - High resolution imaging of macroscopic wear scars in the initial stage N2 - The topography of wear scars on the surface of a steel disc coated with a diamond-like carbon (DLC) layer has been investigated with an Atomic Force Microscope (AFM). AFM topography images have been combined together taking advantage of the stitching technique for the study of wear scars in their initial stage. Moreover, the topography of the sample has been acquired before and after the sliding tests. In this way even very small changes of the sample surface (<10 nm) can be detected. Three main phenomena taking place at the very initial stage of wear could be identified: the abrasion of small asperities bulging out of the sample surface, the carving of swallow grooves with depth under 20 nm, and the partial or total closure of cavities present on the surface. This last phenomenon shows that, before the carving of a wear scar, the plastic deformation of particular regions of the sample, i.e. the volume around the cavities, takes place already after few cycles (in this case between 400 and 800) in the initial phase of the sliding test. KW - Atomic force microscopy KW - Stitching technique KW - Running in KW - Plastic deformation PY - 2015 DO - https://doi.org/10.1016/j.wear.2015.07.013 SN - 0043-1648 VL - 338-339 SP - 372 EP - 378 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-34734 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pfeffer, D. A1 - Scholz, Christian A1 - Belly, C. A1 - Wäsche, Rolf A1 - Schlaak, H.F. A1 - Pott, P.P. T1 - Influence of the actuation waveform on the performance of piezoelectric stick-slip actuators N2 - Performance and efficiency of piezo-electric stick-slip actuators are dependent on the waveform of the electrical actuation of the piezo-stack. This paper compares between a conventional saw-tooth actuation with two waveforms that feature softer acceleration in order to minimize the duration of the slip-phase. It is shown that the proposed waveforms increase both maximum mechanical output power (by 43%) and overall efficiency (by 25%) of the examined actuator. T2 - IKMT 2015 - Innovative Klein- und Mikroantriebstechnik CY - Köln, Germany DA - 14.09.2015 PY - 2015 SN - 978-3-8007-4072-7 N1 - Serientitel: ETG-Fachbericht – Series title: ETG-Fachbericht VL - 146 SP - 100 EP - 104 AN - OPUS4-34883 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wäsche, Rolf T1 - Ceramics and DLC - influence of tribochemistry on sliding under lubricated conditions at elevated temperatures T2 - Satelite Symposium on Tribochemistry CY - Nikko, Japan DA - 2015-09-13 PY - 2015 AN - OPUS4-34325 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wäsche, Rolf A1 - Hartelt, Manfred A1 - Cappella, Brunero T1 - The use of AFM for high resolution imaging of macroscopic wear scars N2 - In this article we demonstrate the use of atomic force microscopy (AFM) measurements for the study of macroscopic wear scars. By stitching AFM images acquired over the wear scar, the detailed structure of the scar can be characterized even when the scar is much wider than the typical maximum scan range of the AFM (50–100 µm). The results obtained by AFM are compared with those yielded by white light interferometry (WLI). The comparison validates the WLI measurements; at the same time, it shows decisive differences in the resolutions of these two methods. As a consequence, AFM measurements are necessary whenever a precise characterization of the structure of the scar is required. However, since stitching of AFM images is rather time-consuming, white light interferometry is recommended as a faster method whenever experiments are aimed at just a gross characterization of the scar and the measurement of mean quantities (e.g. the wear volume). KW - Wear scar KW - Imaging KW - Roughness KW - Wear volume KW - Atomic force microscopy KW - White light interferometry PY - 2014 DO - https://doi.org/10.1016/j.wear.2013.11.009 SN - 0043-1648 VL - 309 IS - 1-2 SP - 120 EP - 125 PB - Elsevier CY - Amsterdam AN - OPUS4-30289 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Scholz, Christian A1 - Wäsche, Rolf ED - Bartz, Wilfried J. T1 - Effect of sliding speed and relative humidity on the tribological behaviour of ceramic and polymer materials N2 - In many technical applications not only the actual friction coefficient is of importance, but rather the constancy is relevant for the functionality. Due to inconstant friction values, positioning processes can be substantially influenced. Aim of the present work is to characterize the effect of sliding speed and relative humidity on the tribological behavior of selected combinations. The tribological tests were carried out at room temperature in a ball-on-disk configuration at a normal load of 1 N and respectively 10 N under dry sliding conditions. The friction and wear behavior is significantly depending on the sliding speed and humidity conditions. Using a chamber enclosing the tribometer the relative humidity inside could be adjusted to dry (< 5% rH), normal (50% rH) and moist (100% rH) conditions during the testing time. Three different frequencies, 0.2 Hz, 2 Hz and 5 Hz, were used for tribological evaluations. Measuring the friction force hysteresis loop distinct differences in the frictional behavior of different material combinations could be observed. Materials selected were ceramics sliding against PP-based polymer and various polymers sliding against Ti6AlV4. T2 - 19th International colloquium Tribology - Industrial and automotive lubrication CY - Stuttgart/Ostfildern, Germany DA - 21.01.2014 KW - Stick slip KW - Polymer KW - Ceramic KW - Sliding speed KW - Relative humidity PY - 2014 SN - 978-3-943563-10-8 SP - Paper 8.11, 1 EP - 6 CY - Stuttgart/Ostfildern AN - OPUS4-30176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wäsche, Rolf T1 - Wear analysis on dental implant materials under partial slip conditions T2 - VII Iberian Conference on Tribology (IBERTRIB 2013) CY - Oporto, Portugal DA - 2013-06-20 PY - 2013 AN - OPUS4-31051 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Harsha, A.P. A1 - Wäsche, Rolf A1 - Hartelt, Manfred T1 - Tribological studies on polyetherketone composite under reciprocating sliding condition against steel cylinder N2 - Tribological studies on neat polyetherketone (PEK) and glass fiber reinforced PEK composite were carried out at room and elevated temperature (120 °C). The objective of this study was to characterize for friction and wear properties under dry reciprocating sliding condition at different experimental conditions. The polymer specimens were made to oscillate against steel cylinder as a counterpart. This kind of contact condition are frequently found in bushes, sliding bearing, electronic parts, seals, etc. The friction and wear behavior of neat PEK and composite was quite different at room temperature and elevated temperature. It was observed that glass fiber reinforcement is beneficial in controlling the wear of PEK matrix at room temperature than at elevated temperature. The test results are discussed by considering the surface properties i.e. material removal and film transfer formation. Scanning electron micrographs and optical micrographs of the worn polymer and steel cylinder was used to study the wear mechanisms. KW - Dry oscillating sliding KW - Polyetherketone composite KW - Wear mechanism KW - Contact geometry PY - 2015 DO - https://doi.org/10.1177/1350650115570403 SN - 1350-6501 VL - 229 IS - 7 SP - 795 EP - 806 PB - Institution of Mechanical Engineers CY - London AN - OPUS4-33526 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pfeffer, D. A1 - Scholz, Christian A1 - Belly, C. A1 - Wäsche, Rolf A1 - Schlaak, H.F. A1 - Pott, P.P. T1 - Modular test bed for performance assessment of piezoelectric stick-slip actuators N2 - Stepping piezoelectric actuators based on the stick-slip effect inherently make use of a friction contact between strator and rotor. This contact defines not only the actuator's performance but also is prone to wear and tear. For broad use, the actuator has to be able to perform around 1 million strokes. To assess the actuator's performance in terms of force, speed, mechanical output, electrical input, and long-term stability under different load- and environmental conditions, as well as different friction partners, a dedicated test-bed for a LSPA30µXS motor by Cedrat Technologies has been set up. T2 - Actuator 2014 - 14th International conference on new actuators & 8th International exhibition on smart actuators and drive systems CY - Bremen, Germany DA - 23.06.2014 KW - Piezoelectric actuator KW - Test bed KW - Stick-slip KW - Performance test KW - Micro positioning PY - 2014 SN - 978-3-933339-22-5 SN - 978-3-933339-23-2 SP - P 50, 617 EP - 620 AN - OPUS4-33498 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wäsche, Rolf A1 - Hartelt, Manfred T1 - Wear testing with crossed cylinders - comparison of methods N2 - Three different contact geometries, ball on disk and two different settings with crossed cylinders have been investigated with regard to the agreement of the results of the tribological quantities determined by each method. The material combination was α-alumina as upper specimen and steel 100Cr6 as lower specimen. For each of the contact geometries 5 independent measurements were carried out and evaluated independently. The agreement between the single results of coefficient of friction and the coefficient of system wear as well as between the different groups and conditions are good. Largest scatter of the results were found in the dry air regime where both friction and wear depend strongly on the relative humidity. However, comparison of the absolute values of the coefficient of wear between the ball on disk contact geometry on one side and the 2 crossed cylinder contact geometries on the other side reveals a significant difference in that the ball on disk results are lower by about a factor of two. The results document also a high degree of repeatability of single wear tests. T2 - 16th International colloquium tribology - Lubricants, materials and lubrication engineering CY - Stuttgart/Ostfildern, Germany DA - 2008-01-15 KW - Fretting KW - Contact geometry crossed cylinders KW - Friction KW - Wear PY - 2008 SP - Paper 10_04_Wäsche, 1 EP - 6 AN - OPUS4-31602 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Tamura, T. A1 - Nakase, Takuya A1 - Hosohata, S. A1 - Kato, S. A1 - Woydt, Mathias A1 - Wäsche, Rolf A1 - Köhler, Norbert T1 - Zero wear and low friction under dry sliding N2 - In diesem Beitrag werden ungeschmierte Gleitpaarungen auf Basis von Oxidkeramik/DLC vorgestellt, bei denen die tribologischen Kenngrößen mehr oder weniger invariant von der Gleitgeschwindigkeit sind. Die DLC-Dünnschicht besteht aus einem bestimmten Verhältnis an sp2/sp3-hybridisiertem Kohlenstoff. Im Gegensatz zu artgleichen Gleitpaarungen aus MgO-.Zr02, AI2O3 oder SSiC mit Reibungszahlen oberhalb von 0,45, zeigt die Gleitpaarungen aus MgO-Zr02/DLC und alpha-A^OVDLC Festkörpergleitreibungszahlen zwischen 0,075 und 0,15, welche mit ansteigender Gleitgeschwindigkeit leicht abnahmen. Die Verschleißkoeffizienten der DLC-Dünnschichten lagen im Bereich von kleiner als 10~7 mm3/Nm bis herunter zu 10"9 mm3/Nm. N2 - This paper presents a dry sliding tribo-couple (DLC/monolithic oxide ceramics), where the tribological quantities are more or less in a wide ränge independent of the sliding speed. The DLC film is composed of a specific mixture of sp3 /sp2 hybridized carbon. Self-mated ceramic/ceramic couples of MgO-Zr02, alpha-AI203 or SSiC are with their coefficients of friction above 0.45 not so lubricious, whereas the coefficients of friction of the tribocouples MgO-Zr02/DLC and alpha-AbOVDLC ranged between 0.075 and 0.15 under dry sliding. The coefficients of friction for these tribo-couples tend to decrease with increase sliding speed from 0.03 m/s to 6 m/s. The dry wear rates of the thin film is low (<10‘7 mm3/Nm) and perfectly independent from sliding velocity. T2 - 55. Tribologie-Fachtagung - Reibung, Schmierung und Verschleiß - Forschung und praktische Anwendungen CY - Göttingen, Germany DA - 22.09.2014 PY - 2014 SN - 978-3-00-046545-1 VL - II SP - 43/1 EP - 43/7 AN - OPUS4-31581 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -