TY - JOUR A1 - Fahrbach, M. A1 - Friedrich, Sebastian A1 - Cappella, Brunero A1 - Peiner, Erwin T1 - Calibrating a high-speed contact-resonance profilometer N2 - A European EMPIR project, which aims to use large-scale piezoresistive microprobes for contact resonance applications, a well-established measurement mode of atomic force microscopes (AFMs), is being funded. As the probes used in this project are much larger in size than typical AFM probes some of the simplifications and assumptions made for AFM probes are not applicable. This study presents a guide on how to systematically create a model that replicates the dynamic behavior of microprobes, including air damping, nonlinear sensitivities, and frequency dependencies. The model is then verified by analyzing a series of measurements. KW - Piezoresistive cantilever KW - AFM KW - contact resonance PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-509899 DO - https://doi.org/10.5194/jsss-9-179-2020 VL - 9 SP - 179 EP - 187 PB - Copernicus Publications AN - OPUS4-50989 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Reichelt, Manuel A1 - Cappella, Brunero T1 - Influence of relative humidity on wear of self-mated 100 Cr6 steel N2 - The influence of relative humidity on friction and wear is subject of several studies in the last decades. A comprehensive understanding of physical and chemical phenomena affecting the tribology is hampered by the lack of reproducible experimental results, by the large number of variables, and by several difficulties in the detection of tribochemical processes and products. In the present work, we analyze the wear coefficient and the wear volumes of 686 unlubricated tests performed on different oscillating tribometers with 100Cr6 balls on 100Cr6 planes at different relative humidity. Aim of this work is to assess the repeatability and reproducibility of data, to determine the dependence of the wear coefficient on the relative humidity, to understand the underlying physicochemical phenomena and to build three dimensional maps of the wear coefficient as a function of both humidity and the product of normal force and sliding distance. KW - Wear KW - 100Cr6 KW - Relative humidity PY - 2020 DO - https://doi.org/10.1016/j.wear.2020.203239 VL - 450-451 SP - 203239 AN - OPUS4-50583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Reichelt, Manuel A1 - Cappella, Brunero T1 - Comparative analysis of error sources in the determination of wear volumes of oscillating ball-on-plane tests N2 - The accurate determination of wear volumes is a prerequisite for the study of numerous tribological phenomena. Wear volumes can be measured with different techniques or else be calculated starting from some quantities measured from the wear scar. Advantages and drawbacks of the measuring techniques are shown by means of wear scars and calottes resulting from ball-on-plane tests with 100Cr6 specimens. When measuring wear volumes, white light interferometry results to be one of the most suitable techniques. When wear volumes are calculated, errors result mainly from two sources: (1) the arbitrary choice of one or few line profiles for the determination of the width and of the planimetric wear, and (2) approximations in the calculation, which are even necessary when values of the wear volumes of the single tribological partners and not only the total volume are of interest. The effect of both error sources on the accuracy in the determination of wear volumes is characterized and elucidated by examples. It is found that errors due to approximations are negligible when compared to errors due to the arbitrary choice of one line profile. KW - Error sources analysis KW - White light interferometry KW - Statistical analysis KW - AFM KW - Wear KW - Oscillating ball-on-disc test PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-508407 DO - https://doi.org/10.3389/fmech.2020.00025 VL - 6 SP - Article 25 AN - OPUS4-50840 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 - JOUR A1 - Cappella, Brunero A1 - Wassenberg, J. R. A1 - Heim, L.-O. A1 - Klostermann, M. A1 - Venzmer, J. A1 - Bonaccurso, E. T1 - Mechanical properties of silicone methacrylate microparticles determined by AFM colloidal probe technique N2 - The mechanical properties of seven types of silicone methacrylate microparticles prepared by solution polymerization with a Pickering emulsifier were investigated by Atomic Force Microscope force–displacement curves acquired in air with the Colloidal Probe Technique, i.e., with spherical SiO2 particles of known radius glued on tipless cantilevers. The deformation curves derived from the force–displacement curves were fitted with Hertz equation for the contact between two spherical particles, which lead to the determination of the elastic modulus of the samples. The performed measurements and the analysis provide quite exact values of the elastic modulus of all investigated polymer particles. Moreover, the results of the measurements were repeatable over large time intervals, also with different experimental setups. The influence of the sample preparation (polymerization method, cross-linking density of the polymer, and thickness of the external shell of the Pickering emulsifier) is discussed as well. The elastic moduli correlate with the cross-linking density (from 2 MPa for low cross-linking density up to 100–130 MPa for medium cross-linking density), whereas the thickness of the external shell formed by the Pickering emulsifier has no measurable influence on the mechanical properties of the microparticles. KW - Colloidal probe technique KW - Hertz model KW - Silicone elastomer PY - 2014 DO - https://doi.org/10.1016/j.polymer.2014.01.021 SN - 0032-3861 SN - 1873-2291 VL - 55 IS - 5 SP - 1209 EP - 1216 PB - Elsevier Ltd. AN - OPUS4-30316 LA - eng 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 - JOUR A1 - Krämer, Günther A1 - Griepentrog, Michael A1 - Bonaccurso, E. A1 - Cappella, Brunero T1 - Study of morphology and mechanical properties of polystyrene-polybutadiene blends with nanometre resolution using AFM and force-distance curves N2 - Thin polybutadiene/polystyrene blend films were deposited on glass substrates by spin-coating. The two polymers were chosen, as they are immiscible and differ strongly in their mechanical properties. The blend was characterized with Tapping Mode and force–distance curves. Several advantages of force–distance curves measurements compared to Tapping Mode are shown, most of all the capability of yielding quantitative information about several properties, such as Young's modulus and adhesion. Also the aging behaviour of the blend exposed to air could be observed, in particular the increase of the Young's modulus due to cross-linking and dewetting processes. Additionally, the sample was used to improve the resolution of force–distance curves up to 6 nm, which is to date the best resolution achieved with force–distance curves. Such an improvement resolves the major disadvantage of force–distance curves, compared to other scanning mode, i.e. its inferior resolution. KW - Polymer blends KW - Mechanical properties KW - Atomic force microscopy KW - Force-distance curves KW - High-resolution force-volume PY - 2014 DO - https://doi.org/10.1016/j.eurpolymj.2014.03.026 SN - 0014-3057 SN - 1873-1945 VL - 55 SP - 123 EP - 134 PB - Elsevier CY - Oxford AN - OPUS4-30625 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Friedrich, Sebastian A1 - Cappella, Brunero T1 - Application of contact-resonance AFM methods to polymer samples N2 - Contact-resonance AFM (CR-AFM) has been used in recent years for the measurement of mechanical properties. Compared with other techniques, CR-AFM has a much shorter acquisition time, compensating the incomplete theoretical understanding of the underlying physical phenomena. In the present paper, we propose a procedure, which allows to determine the elastic modulus of the sample as a parameter of the fit of the CR frequency as a function of the load. It is concluded that CR measurements are not appropriate for polymer samples. Major drawbacks are the bad resolution for moduli lower than ca. 10 GPa and the lack of a comprehensive physical model. KW - Atomic force microscopy KW - Contact resonance KW - Mechanical properties KW - Polymers KW - Wear PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-515621 DO - https://doi.org/10.3762/bjnano.11.154 VL - 11 SP - 1714 EP - 1727 AN - OPUS4-51562 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fahrbach, M. A1 - Friedrich, Sebastian A1 - Behle, H. A1 - Xu, Min A1 - Cappella, Brunero A1 - Brand, U. A1 - Peiner, E. T1 - Customized piezoresistive microprobes for combined imaging of topography and mechanical properties N2 - Customized piezoresistive cantilever microprobes with a deflection range of 120 μm and silicon tips of 100 μm height were operated in a Cypher AFM showing their functionality for measuring topography together with stiffness, adhesion, and viscoelastic properties of thin films. KW - Cantilever microprobe KW - Piezoresistive KW - Atomic force microscopy KW - Force-distance curves KW - Contact resonance KW - Lubricants PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-524225 DO - https://doi.org/10.1016/j.measen.2021.100042 VL - 15 SP - 100042 PB - Elsevier Ltd. AN - OPUS4-52422 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Reichelt, Manuel A1 - Cappella, Brunero T1 - Large scale multi-parameter analysis of wear of self-mated 100Cr6 steel - A study of the validity of Archard's law N2 - Considerable scattering of experimental wear results affects seriously the evaluation of repeatability and reproducibility of tribological measurements and hampers detecting, studying, and verifying tribological laws. An accurate characterization of the statistics of results, the detection of the influence of operating parameters, and the verification of equations describing tribological phenomena can be achieved only through the analysis of large datasets with wide variation of parameters. Taking advantage of more than 400 experiments performed with the same material pairing under the same conditions on four different tribometers, the repeatability and reproducibility of volumetric wear measurements has been evaluated using Welch's test. By testing Archard's law over seven orders of magnitude of sFN, it was found that this law is not universally valid and that, under certain conditions, the wear coefficient depends on sFN itself. KW - Wear KW - Archard's law KW - 100Cr6 steel KW - Scattering PY - 2021 DO - https://doi.org/10.1016/j.triboint.2021.106945 VL - 159 SP - 6945 PB - Elsevier Ltd. AN - OPUS4-52244 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -