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 - TY - JOUR A1 - Rawat, S. S. A1 - Harsha, A. P. A1 - Khatri, O. P. A1 - Wäsche, Rolf T1 - Pristine, reduced, and alkylated graphene oxide as additives to paraffin grease for enhancement of tribological properties N2 - Pristine, reduced, and alkylated graphene oxides are applied as lubricating additives in paraffin grease. It has revealed that their crystalline structure governs the tribological properties of grease for steel tribo-pair. The microstructural analyses of grease samples showed that a loose fiber network of soap in the presence of graphene-based additive allows their facile release for efficient lubrication. The surface analyses based on the microscopic and elemental mapping show the development of a graphene-derived protective film on the worn scars, which protected the tribo-surfaces and subsided the wear. The reduced graphene oxide (rGO) with the interlamellar distance of 0.35 nm in the (002) plane provided minimum resistance to shear and exhibited maximum reduction in coefficient of friction (COF) for the paraffin grease. The presence of oxygen functionalities in the basal of pristine and alkylated graphene oxide (GO) compromised the interlamellar shearing under tribo-stress; consequently, higher COF than that of rGO. KW - Coefficient of friction KW - Graphene oxide KW - Grease KW - Nanoadditive KW - Tribo-film KW - Wear KW - Boundary lubrication KW - Grease lubrication KW - Lubricant additives KW - Lubricants PY - 2021 DO - https://doi.org/10.1115/1.4047952 VL - 143 IS - 2 SP - 021903-1 EP - 021903-11 PB - ASME AN - OPUS4-51170 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Harsha, A. P. A1 - Wäsche, Rolf A1 - Joyce, T. J. T1 - Friction and wear of two polyethylenes under different tribological contact conditions N2 - Tribological properties of ultrahigh-molecular weight polyethylene (UHMWPE) and cross-linked polyethylene (XLPE) were studied in two different wear modes. Firstly, reciprocating sliding wear studies under non-conformal contact investigated the effects of counterface surface roughness (polished, lapped and ground) of Ti6Al4V on the friction and wear of the polyethylenes. Secondly, two-body abrasive wear studies in conformal contact against different abrasive grit size papers were also carried out to ascertain the wear sensitivity of the polyethylenes under these adverse conditions. Wear mechanisms were studied using optical and scanning electron micrographs. The results of the reciprocating sliding wear studies showed that surface roughness of the counterface influenced friction and wear characteristics although no correlation was found between the coefficient of friction and specific wear rate. XLPE demonstrated wear sensitivity, particularly under severe abrasive wear condition. The results indicated that the performance of the polyethylenes greatly depends upon the tribological system under which it is operating. KW - Abrasive wear KW - Polyethylene KW - Reciprocating sliding wear KW - Surface roughness KW - Wear mechanism PY - 2021 DO - https://doi.org/10.1177/0967391120920130 SN - 0967-3911 SN - 1478-2391 VL - 29 IS - 5 SP - 393 EP - 404 PB - Sage Publishing CY - London AN - OPUS4-56903 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wäsche, Rolf T1 - Tribological studies on polyetherimide composites sliding against steel under reciprocating conditions N2 - Results of tribological tests on polyetherimide composites were presented. The tests were carried out at room temperature as well as at 120°C. Counter body was steel 100Cr6. T2 - PolyTrib 2016. 2nd International Conference on Polymer Tribology CY - Ljubljana, Slovenia DA - 15.09.2016 KW - PEI KW - Composites KW - Polyetherimide KW - Temperature KW - Steel PY - 2016 AN - OPUS4-38690 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Harsha, A. P. A1 - Wäsche, Rolf T1 - Tribological studies on polyetherimide composites sliding against steel under reciprocating conditions N2 - The friction and wear properties of polyetherimide composites under dry oscillating sliding condition at room temperature (RT) as well as at elevated temperature (120 °C) was investigated. The polymer specimens were made to oscillate against steel cylinder as a counterpart. The friction and wear properties of PEI and composites were strongly influenced by the temperature. In case of carbon fiber composite abrasive action of carbon fibers has severely damaged the counterpart and resulted in accelerated wear of the composite at RT. Solid lubricants filled (PTFE, MoS2, graphite) along with glass fiber is beneficial in improving the friction and wear performance of the PEI composite at RT, whereas at elevated temperature wear performance was deteriorated. T2 - 2nd International Conference on Polymer Tribology CY - Ljubljana, Slovenia DA - 15.09.2016 KW - Polyetherimide KW - Composites KW - Friction KW - Wear KW - Temperature KW - Oscillating sliding KW - Solid lubricant KW - Fibers PY - 2016 AN - OPUS4-38135 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Woydt, Mathias A1 - Wäsche, Rolf A1 - Brandt, Guido A1 - Ehrke, Roman A1 - Yano, S. A1 - Sasaki, S. T1 - Tribology in hot steam for energy recovery N2 - The wear rates of self-mated alumina couples show that friction as well as wear is largely determined by the above-mentioned hydro-thermal conditions. The presence of water and its amount available in the surrounding system either in liquid or in gaseous form plays a key role for friction and wear behavior and can be beneficial for the tribological profile of steam degradation resistant materials. Hot steam enhances the tribo-chemical formations of oxides and hydroxides on MgO-ZrO2 alumina and antimony impregnated carbon. T2 - 21th International Colloquium Tribology CY - Stuttgart/Ostfildern, Germany DA - 09.01.2018 KW - Tribology KW - Friction KW - Alumina KW - Hot steam PY - 2018 SP - 1 EP - 2 AN - OPUS4-43896 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wäsche, Rolf A1 - Brandt, Guido A1 - Ehrke, Roman A1 - Nolze, Gert A1 - Schmid, Thomas A1 - Sasaki, S. A1 - Woydt, Mathias T1 - Wear behaviour of alpha-alumina in hot steam at high contact pressure N2 - The work examines the wear behaviour of α-aluminium oxide by combining thermodynamic modelling with advanced wear testing as well as analytical methods to get a better understanding of this structural ceramic material wear behavior and its possible use in high temperature steam environment. KW - Aluminium oxide KW - Temperature KW - Hot steam KW - Diaspore KW - Ceramic KW - Wear PY - 2018 DO - https://doi.org/10.1016/j.wear.2018.02.012 SN - 0043-1648 SN - 1873-2577 VL - 404-405 SP - 22 EP - 30 PB - Elsevier B.V. AN - OPUS4-44449 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wäsche, Rolf T1 - Colloidal processing of Nbc cermets with Ni binder N2 - Niobium-titanium carbide cermets with nickel binder have been prepared by colloidal processing in water without a milling step by using Poly-diallyl-dimethyl-ammonium chloride (Poly-DADMAC) as a dispersant. Homogeneous microstructures with relative densities larger than 99% of the theoretical density have been achieved by gas pressure sintering in argon atmosphere. However, mechanical properties like hardness and strength were slightly decreased due to precipitation of free carbon. T2 - ISNT2017 & ISSNOX5 - 9th International Symposium on Nitrides & 5th International Symposium on SiAlONS and Non-Oxides CY - Sapporo, Japan DA - 27.08.2017 KW - Niobium carbide KW - Colloidal processing KW - Nckel binder KW - Hardness PY - 2017 AN - OPUS4-42152 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wäsche, Rolf T1 - Niobium carbide, a new cermet material with excellent properties N2 - Niobium carbide is a ceramic material which can be used with excellent results to replace tungsten carbide with cobalt binder. Furthermore, it might be manufactured by classic ceramic technologies and even colloidal processing. To achieve high toughness and strength, it is necessary to have a perfect mix of hard phase and binder, which is mainly achieved by ball milling. Mechanical and physical properties as well as results on different tribological and application-oriented machining tests are presented. The results have been compared with results obtained with NbC grades with Co and Fe3Al binders as well as with pure binderless hot-pressed NbC and SPS sintered Nb2O5. T2 - ICCCI 2018 - 6th Int. Conf. on the Characterization and Control of Interfaces for High Quality Advanced Materials and 54th Summer Symposium on Powder Technology CY - Kurashiki, Japan DA - 09.07.2018 KW - Niobium carbide KW - Cermet KW - Microstructure KW - Properties PY - 2018 AN - OPUS4-45643 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Harsha, A. P. A1 - Wäsche, Rolf T1 - Influence of temperature on friction and wear characteristic of polyaryletherketones and their composites under reciprocating sliding condition N2 - In the present work it was shown the tribological behavior of different polyaryletherketones (PAEKs) and their composites under reciprocating sliding conditions at room temperature as well as at elevated temperature (120°C). KW - Composite KW - PAEKs KW - Reciprocating sliding KW - Solid lubricants KW - Wear mechanisms PY - 2018 DO - https://doi.org/10.1007/s11665-018-3633-y SN - 1059-9495 VL - 27 IS - 10 SP - 5438 EP - 5449 PB - Springer AN - OPUS4-46430 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wäsche, Rolf A1 - Jayachandran, Ashok Raj A1 - Brandt, Guido A1 - Schmid, Thomas A1 - Tamura, T. A1 - Nakase, T. T1 - Tribofilm formation of a-C:H coatings under influence of temperature in boundary lubricated oscillating sliding against alumina and silicon nitride N2 - Gegenstand dieses Beitrags ist der Einfluss von Temperatur und Gegenkörperwerkstoff auf die Bildung von Tribofilmen auf a-C:H Beschichtungen. Dies wurde mit einer Kugel-Ebene Anordnung im geschmierten Kontakt untersucht. KW - a-C:H KW - Temperature KW - Tribofilm KW - Lubricated sliding KW - Alumina KW - Silicon nitride PY - 2018 SN - 0724-3472 VL - 65 IS - 5 SP - 28 EP - 37 PB - expert Verlag CY - Tübingen AN - OPUS4-46034 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wäsche, Rolf T1 - Influence of temperature on tribological behaviour of DLC coatings under lubricated conditions up to 250°C N2 - The lecture deals with both friction and wear processes in ceramic - a-C:H Systems. T2 - AsiaTrib 2018 CY - Kuching, Malaysia DA - 16.09.2018 KW - Temperature KW - Lubricated sliding KW - Tribofilm PY - 2018 AN - OPUS4-46036 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -