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  • MDPI AG  (4)
  • Maier, Michael  (4)
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  • MDPI AG  (4)
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  • 1
    Online Resource
    Online Resource
    MDPI AG ; 2023
    In:  Coatings Vol. 13, No. 4 ( 2023-03-29), p. 697-
    In: Coatings, MDPI AG, Vol. 13, No. 4 ( 2023-03-29), p. 697-
    Abstract: Specific surface textures may reduce the friction and increase the lifting forces in lubricated contacts. For the detrimental operating condition of mixed friction, wear is induced by the solid contact. In this study, a methodology for wear calculation in textured, lubricated contacts is presented that considers the wear-induced surface topography evolution. Based on the Reynolds differential equation, the mass-conserving cavitation model according to Jakobsson, Floberg, and Olsson (JFO), a wear-dependent asperity contact pressure curve and the wear equation according to Archard, wear in a wedge-shaped, textured lubrication gap was calculated. The results show the wear behavior of textured lubrication gaps. Based on the wear simulations, the tribological behavior of the textured surfaces compared to smooth surfaces is discussed. It is evident that textures, which improve the tribological performance in the hydrodynamic lubrication regime, are not necessarily associated with low wear values in a lubrication condition in the mixed friction regime. The analysis of the wear-dependent parameters initially showed a ‘recovery’ of the tribological system with increasing wear until the performance decreased again after a specific reversal point. This behavior is attributed to the relative position of the surface textures in the lubrication gap.
    Type of Medium: Online Resource
    ISSN: 2079-6412
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662314-6
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  • 2
    Online Resource
    Online Resource
    MDPI AG ; 2022
    In:  Lubricants Vol. 10, No. 12 ( 2022-11-26), p. 335-
    In: Lubricants, MDPI AG, Vol. 10, No. 12 ( 2022-11-26), p. 335-
    Abstract: Surface topography has a significant influence on the friction behaviour in lubricated contacts. During running-in, the surface topography is continuously changed. The surface structure influences the contact stiffness (asperity contact pressure) as well as the microhydrodynamics (flow factors). In this study, different models for wear simulation of real rough surfaces were created in Matlab© (MathWorks, Natick, MA) and Abaqus© (ABAQUS Inc., Palo Alto, CA, USA) using the Usersubroutine Umeshmotion. The arithmetic mean height Sa(wh), the maximum height Sz(wh), as well as the asperity contact pressure pasp(h,wh) as a function of the wear height (wh) are used to characterise the surface for the respective wear state. The surface characteristics obtained from the simulations are validated with parameters from experiments. The aim of this study was to create a simulation methodology for mapping surface development during the running-in process. The results show, that the qualitative course of the surface parameters can be reproduced with the applied simulation methodology. Compared to the experiments, the rough surfaces are flattened faster. By adapting the simulation results in postprocessing, good agreements with the experiments can be achieved.
    Type of Medium: Online Resource
    ISSN: 2075-4442
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2704327-7
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  • 3
    In: Lubricants, MDPI AG, Vol. 8, No. 1 ( 2020-01-15), p. 8-
    Abstract: Optimizing the surface topography of cast iron crankshafts offers the opportunity to use this material as an alternative to steel in high-performance combustion engines. In the past, this was not possible due to the higher wear on bearing shells and the higher friction losses in relation to forged steel shafts. In order to find an optimized shaft micro topography, the friction and wear behavior of steel and cast iron shafts with different surface treatments were compared to each other, using a combined physical (experimental) and a virtual (computational) simulation approach. The experiments were carried out with a rotary tribometer using a journal bearing test configuration with the possibility to test real-life bearing shells and shaft specimens, manufactured from real-life crankshafts. In the experiments, a polished steel shaft with low bearing wear was effective. The optimization of cast iron crankshafts by a novel surface treatment showed a significant reduction of bearing wear in relation to the classical surface finishing procedures of cast iron shafts. A computational simulation approach, considering the real-life micro topography by using the Navier–Stokes equations for the calculation of micro hydrodynamics, supports the assessment of fluid friction. The virtual simulation shows, in accordance to the experimental results, only a minor influence of the investigated shaft topographies on the fluid friction. Further optimization of shaft surfaces for journal bearing systems seems possible only by the usage of patterned micro topographies.
    Type of Medium: Online Resource
    ISSN: 2075-4442
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2704327-7
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  • 4
    In: Lubricants, MDPI AG, Vol. 9, No. 11 ( 2021-11-10), p. 109-
    Abstract: The measurement of acoustic emission data in experiments reveals informative details about the tribological contact. The required recording rate for conclusive datasets ranges up to several megahertz. Typically, this results in very large datasets for long-term measurements. This in return has the consequence, that acoustic emissions are mostly acquired at predefined cyclic time intervals, which leads to many blind spots. The following work shows methods for effective postprocessing and a feature based data acquisition method. Additionally, a two stage wear mechanism for bearings was found by the described method and could be substantiated by a numerical simulation.
    Type of Medium: Online Resource
    ISSN: 2075-4442
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2704327-7
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