Browsing by Author "Pape, Florian"

Now showing 1 - 5 of 5
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    Biogenic palm oil-based greases with glycerol monostearate and soy wax: A rheological and tribological study
    (2025) Nassef, Belal G.; Moradi, Amirreza; Bayer, Gernot; Pape, Florian; Abouelkasem, Zeyad A.; Rummel, Florian; Schmoelzer, Stefan; Poll, Gerhard; Marian, Max
    The increasing environmental concerns associated with conventional lubricants have led to a growing interest in sustainable alternatives, particularly biogenic grease. This study introduces a novel approach to synthesizing and characterizing fully biodegradable greases using palm oil as the base oil and renewable biothickeners, namely glycerol monostearate (GMS) and soywax (SW). The innovation lies in utilizing the distinct properties of these biothickeners to optimize the grease structure and performance for industrial applications. GMS enhances the consistency and mechanical stability, while SW controls the elasticity and oil bleeding. Rheological analysis shows that GMS exhibits the thickening capabilities at room temperature (RT) to achieve common grease consistencies, while SW enhances elasticity, achieving a unique balance of firmness and flexibility. Thermal analysis indicates that GMS-based greases had higher thermal stability, while SW enhance low-temperature performance. Tribological testing reveals a reduction in friction and wear, with an earlier transition to the mixed lubrication regime compared to a reference commercial grease (CG). Under boundary lubrication, GMSbased samples perform better than the CG, particularly under higher contact pressures. In contrast, SW-based formulations demonstrate better lubrication at lower contact pressures. In fluid friction regimes, almost all biobased samples outperform the CG, showing potential for high-speed applications. When tested in angular contact ball bearings under oscillating motion (a typical moderate temperature application), the bio-greases show decent results in preventing false brinelling. This study highlights the potential of these eco-friendly formulations as a viable alternative to conventional greases.
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    Comprehensive Evaluation of the Rheological, Tribological, and Thermal Behavior of Cutting Oil and Water-Based Metalworking Fluids
    (2025) Pape, Florian; Nassef, Belal G.; Schmölzer, Stefan; Stobitzer, Dorothea; Taubmann, Rebekka; Rummel, Florian; Stegmann, Jan; Gerke, Moritz; Marian, Max; Poll, Gerhard; Kabelac, Stephan
    Metalworking fluids (MWFs) are crucial in the manufacturing industry, playing a key role in facilitating various production processes. As each machining operation comes with distinct requirements, the properties of the MWFs have to be tailored to meet these specific demands. Understanding the properties of different MWFs is fundamental for optimizing processes and improving performance. This study centered on characterizing the thermal behavior of various cutting oils and water-based cutting fluids over a wide temperature range and sheds light on the specific tribological behavior. The results indicate that water-based fluids exhibit significant shear-thinning behavior, whereas cutting oils maintain nearly Newtonian properties. In terms of frictional performance, cutting oils generally provide better lubrication at higher temperatures, particularly in mixed and full-fluid film regimes, while water-based fluids demonstrate greater friction stability across a wider range of conditions. Among the tested fluids, water-based formulations showed a phase transition from solid to liquid near 0 °C due to their high water content, whereas only a few cutting oils exhibited a similar behavior. Additionally, the thermal conductivity and heat capacity of water-based fluids were substantially higher than those of the cutting oils, contributing to more efficient heat dissipation during machining. These findings, along with the reported data, intend to guide future researchers and industry in selecting the most appropriate cutting fluids for their specific applications and provide valuable input for computational models simulating the influence of MWFs in the primary and secondary shear zones between cutting tools and the workpiece/chiplet.
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    From Damage to Functionality: Remanufacturing of Thrust Roller Bearings by Tailored Forming
    (John Wiley and Sons Inc, 2024) Saure, Félix; Pape, Florian; Poll, Gerhard; Marian, Max
    Axial and radial rolling bearings are critical components in various machines, particularly in large-scale applications such as mining and heavy machinery. Failures in these bearings can cause significant operational downtime and high replacement costs. Common failure modes include plastic deformation, abrasive wear, insufficient lubrication, and fatigue, necessitating efficient repair strategies. This article investigates the tailored forming process chain for repairing axial bearing washers, focusing on plasma-transferred arc deposition welding. The repair process involves removing damaged areas, welding, and machining to nominal size. Materials used include a novel alloy and commercially available powders. The repaired bearings undergo rigorous testing, including scanning acoustic microscopy for weld quality assessment and fatigue tests on FE8 test rig. Results indicate that the newly developed alloy exhibits higher fatigue life despite its lower hardness compared to AISI 52100 and AISI 4140 steels. The repaired bearings achieve a service life comparable to new bearings, with the welding process quality significantly impacting longevity. Tribological tests show the new alloy's superior wear resistance, suggesting its potential for extending the service life of repaired bearings. The study concludes that tailored forming processes, combined with optimized welding techniques, can effectively repair rolling bearings, reducing costs and downtime while enhancing performance.
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    From Experimentation to Optimization: Surface Micro-Texturing for Low-Friction and Durable PTFE–Steel Interfaces Under Full Film Lubrication
    (Multidisciplinary Digital Publishing Institute (MDPI), 2024) Long, Risheng; Hou, Jincheng; Zhang, Yimin; Shang, Qingyu; Ma, Chi; Pape, Florian; Marian, Max
    To enhance the sliding tribological performance between PTFE and 40#steel (AISI 1040) under full film lubrication conditions, laser surface texturing (LST) technology was employed to prepare micro-dimples on the contact surfaces of 40# steel discs. The Box–Behnken design response surface methodology (BBD-RSM) was applied to optimize the micro-dimple parameters. Coefficients of friction (COFs), wear losses and worn contact surfaces of the PTFE–40# steel tribo-pairs were researched through repeated wear tests, as lubricated with sufficient anti-wear hydraulic oil. The influencing mechanism of micro-dimples on the tribological behavior of tribo-pairs was also discussed. The results proved that micro-dimples can significantly improve the tribological properties of PTFE–40#steel tribo-pairs. The deviation between the final obtained average COF and the prediction by the BBD-RSM regression model was only 0.0023. Following optimization, the average COF of the PTFE–40# steel tribo-pair was reduced by 39.34% compared to the smooth reference. The wear losses of the PTFE ring and 40# steel disc decreased by 91.8% and 30.3%, respectively. This study would offer a valuable reference for the optimal design of key seals used in hydraulic cylinders.
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    Synergistic Effects of Graphene-added Lubricants and Surface Micro-texturing on the Tribological Behavior of Thrust Roller Bearings
    (2024) Long, Risheng; Yao, Ying; Zhang, Longen; Shang, Qingyu; Sun, Shaoni; Hu, Jiashuai; Pape, Florian; Marian, Max
    The synergistic effects of graphene additive and surface micro-texturing on the friction and wear properties of rolling bearings are still a research gap. To this end, the tribological behavior of dimples textured thrust roller bearings (81107TN) are investigated under starved lubrication. The lubricants contained different mass fractions (0.06 %, 0.10 % and 0.14 %) of graphene. The evenly distributed dimples (diameter: 60 mu m or 250 mu m; depth: 1 mu m or 8 mu m) were manufactured only on the raceways of the shaft washers. By comparing the coefficients of friction (COF), wear losses and worn surfaces, the influence of various dimples dimensions and mass fractions of graphene on the tribological behavior of rolling bearings is discussed. The results show that appropriate dimple parameters and a suitable mass fraction of graphene can synergistically have a positive effect on the tribological properties of bearings. In this work, the textured group, with a dimple-diameter of 60 mu m and a dimple-depth of 1 mu m, can provide the best comprehensive friction-reducing and wear-reducing performance for the mass fraction of graphene with 0.10 wt%. Compared to the smooth bearings lubricated with base oil, its mean COF is reduced by 31 % and its wear loss by 35 %. This work can be a valuable reference for the improvement of rolling bearings and lubricants.