9 Komponentensicherheit
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- 9.5 Tribologie und Verschleißschutz (24) (entfernen)
Eingeladener Vortrag
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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.
In this presentation tribological investigations on steels, polymers and coatings in gaseous and liquid hydrogen are shown. For steels the results of show that although martensitic steel may suffer from hydrogen embrittlement, application e.g. in roller bearings is possible. On the other hand, martensitic transformation of austenitic steels may cause problems in the application of these materials. Furthermore, the tribological performance of polymer composites with and without solid lubricant fillers in gaseous and liquid hydrogen was investigated. In particular, PEEK- and PTFE-matrix compounds showed low friction and sufficient low wear under these conditions. Among the solid lubricants, carbon-based materials are appropriate for hydrogen applications. Several variants of DLC and ta-C materials were tested. Beside the results for hydrogen, also a comparison with CH4-environment is shown.
This lecture deals with the sliding behaviour of polymer composites in vacuum environment. At first, the effect of the polymer matrix and solid lubricants such as graphite and MoS2 are presented. The second part focusses on the influence of the residual pressure with experimental results obtained in high and ultrahigh vacuum.
This lecture deals with the sliding behaviour of polymer materials in hydrogen environment. After a short introduction of the hydrogen activities at BAM, the tribological performances of polymer materials in gaseous hydrogen are presented and compared with air and vacuum environment. The second part focusses on the influence of the counterface materials in hydrogen. Finally, the last section is dedicated to experiments liquid hydrogen.
This lecture deals with the friction and wear of polymeric materials at cryogenic temperatures. The first part is dedicated to the low temperature properties of polymers and cryogenic environment as well as an introduction to cryotribology and friction models. The second part presents some experimental results, focusing on the effect of polymer composition, cryogenic media and stick-slip behaviour.
The focus of this study is to evaluate of hydrogen on the friction and wear behavior of a wide range of polymer materials. Thereby, the tribological performance of filled and unfilled polymers from different suppliers were compared at room temperature in air and hydrogen gas (H2) as well as in liquid hydrogen at -253°C (LH2).
Anerkannte Institutionen stellen ihre kombinierten Kompetenzen auf dem Gebiet tribologischer Charakterisierungen Industrie und Forschung zur Verfügung (https://www.i-tribomat.eu/). Ein Aspekt hierbei ist eine tribologische Datenbank. Um die nötige Qualität der Daten sicherzustellen, sind vereinheitlichte Prozeduren erforderlich, in deren Auswirkungen dieser Vortrag einen Einblick gibt.
Anerkannte Institutionen stellen ihre Kompetenzen auf dem Gebiet tribologischer Charakterisierungen Industrie und Forschung zur Verfügung (https://www.i-tribomat.eu/). Ein Aspekt hierbei ist eine tribologische Datenbank. Um die nötige Qualität der Daten sicherzustellen, sind vereinheitlichte Prozeduren erforderlich, in deren Auswirkungen dieser Vortrag einen Einblick gibt.
In the present paper, friction and mechanical properties of AFM-Scan-Induced ripple structures on films of polystyrene and poly-n-(butyl methacrylate) are investigated. Force volume measurements allow a quantitative analysis of the elastic moduli with nanometer resolution, showing a contrast in mechanical response between bundles and troughs. Additionally, analysis of the lateral cantilever deflection shows a clear correlation between friction and the sample topography. Those results support the theory of crack propagation and the formation of voids as a mechanism responsible for the formation of ripples. This paper also shows the limits of the presented measuring methods for soft, compliant, and small structures.
We show for the first time tribotests performed with self-mated 100Cr6 steel, taking advantage of an AFM, employed as a tribometer for the tribotests as well as for the inspection of wear of both tribopartners. Emphasis is put on the morphology of the scars, on wear particles, and on wear of the “colloidal” particles glued on the AFM cantilever. Measurements demonstrate the possibility of characterizing single asperity events leading to very small wear. We highlight several phenomena, which are elementary key constituents of tribological processes. Such phenomena, probably occurring also at the macroscale, can be detected, identified, and characterized with high spatial and time resolution only at the nanoscale, thus giving insight into conditions and causes of their emergence.
Wear test results exhibit often large scattering. Hence, the study of spreading of experimental results requires big datasets.
In various studies, wear coefficients were found to have lognormal distributions. Therefore, it was supposed that the wear coefficient is affected by two normally distributed variables, which combine through a product.
In the present study, we demonstrate that a lognormal distribution may arise from a nonconstant wear coefficient, too, i.e., when a system does not follow Archard’s law.
Different types of laser-generated surface structures, i.e., Laser-induced Periodic Surface Structures (LIPSS, ripples), Grooves, and Spikes are generated on titanium and Ti6Al4V surfaces by means of femtosecond (fs) laser scan processing (790 nm, 30 fs, 1 kHz) in ambient air. Morphological, chemical and structural properties of the different surface structures are characterized by various surface analytical techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), Glow discharge optical emission spectroscopy (GD-OES), and depth-profiling Auger electron spectroscopy (AES). It is revealed that the formation of near-wavelength sized LIPSS is accompanied by the formation of a graded oxide extending several tens to a few hundreds of nanometers into depth. GD-OES performed on other superficial fs-laser generated structures produced at higher fluences and effective number of pulses per spot area such as periodic Grooves and irregular Spikes indicate even thicker graded oxide layers. These graded layers may be suitable for applications in prosthetics or tribology.
The focus of this study is to evaluate the influence of hydrogen on the friction and wear behavior of a wide range of polymer materials. Thereby, the tribological performance of filled und unfilled polymers from different suppliers were compared at room temperature in air and hydrogen gas (H2) as well as in liquid hydrogen at -235°C (LH2).
Increasing demand for alternatives to tungsten carbide (WC) cemented carbides as cutting tools, due to the health risks of their wear products WO3 and Co3O4. Niobium carbide (NbC) has a high potential, due to its high wear resitance, high hot hardness and melting point (3520°C), and low solubility in iron alloys.
Die vorliegende Doktorarbeit handelt von der Bestimmung und der Untersuchung vom Verschleißvolumen und vom Verschleißkoeffizienten bei ungeschmierten Modellversuchen an 100Cr6-Ebenen und -Kugeln unter Schwingungsbeanspruchung. Die experimentelle Arbeit wurde mittels statistischer Auswertung einer großen Menge von eigenen und früheren Versuchsdaten an fünf Tribometern bei umfangreicher Variation der Beanspruchungsparameter durchgeführt. Ziel war es, die Wiederholbarkeit und Reproduzierbarkeit der experimentellen Ergebnisse zu überprüfen sowie das Archard-Gesetz zu verifizieren. Des Weiteren wurde der Einfluss der Luftfeuchtigkeit auf den Verschleiß untersucht.
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.
High spatially resolved quantitative bioimaging of CdSe/ZnS Quantum Dots uptake in two kinds of cells is investigated combining laser ablation inductively coupled plasma mass spectrometry and the spatially resolved analysis of dried pL-droplets from a solution with a known concentration of Quantum Dots. Single cells and dried pL-droplets are morphologically characterized by Atomic Force Microscopy. A number concentration of CdSe/ZnS QDs between 3.5 104 and 48 104 is estimated to be uptaken by several selected single cells, after being incubated in the presence of a QDs suspension added to a standard cell culture medium. Mono-elemental bioimaging at subcellular resolution seems to show a higher number concentration of the CdSe/ZnS QDs in the cytosol around the cell nucleus.
This presentation deals with the influence of the counterface materials on the sliding behaviour of some polymer materials in hydrogen. Polyimide (PI), polyetheretherketone (PEEK) and Polytetrafluoroethylene (PTFE) materials were investigated against hardened 52100 martensitic bearing steel and 304 austenitic stainless steel with similar roughness (Ra = 0.2 μm). Results indicate that the friction and wear of PI and PEEK materials depend on the counterface material. This effect wasn’t observed for PTFE composites.
While the tribological performance of polyimide is better against 52100 in hydrogen, improved sliding behaviour of PEEK materials is observed with 304 counterface, particularly at higher sliding speed. Surface analyses of the transfer film reveal that the influence of the counterface is primarily related to the chemical nature of the steel for PI and to the thermal conductivity of the disc for PEEK materials.
This paper focuses on the influence of the counterface materials on the sliding behaviour of polymer materials in hydrogen. Polyimide (PI), polyetheretherketone (PEEK) and Polytetrafluoroethylene (PTFE) materials were investigated against hardened 52100 martensitic bearing steel and 304 austenitic stainless steel with similar roughness (Ra = 0.2 μm). Results indicate that the friction and wear of PI and PEEK materials depend on the counterface material. This effect wasn’t observed for PTFE composites. While the tribological performance of polyimide is better against 52100 in hydrogen, improved sliding behaviour of PEEK materials is observed with 304 counterface, particularly at higher sliding speed. Surface analyses of the transfer film reveal that the influence of the counterface is primarily related to the chemical nature of the steel for PI and to the thermal conductivity of the disc for PEEK materials.
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.