DSpace Angular :: Browsing by Author "Pape, Florian "

Browsing by Author "Pape, Florian "

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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.
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.
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.
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.
Location- and time-resolved strain measurement in thrust roller bearings using thin-film sensors
(2025) Konopka, Dennis; Steppeler, Tobias; Ottermann, Rico; Dencker, Folke; Pape, Florian; Poll, Gerhard; Wurz, Marc Christopher; Marian, Max
Bearings play a crucial role in a broad range of engineering applications, such as automotive, aerospace and renewable energies. Particularly when it comes to larger and/or hard to replace/repair bearings, such as those in wind turbines, condition monitoring and load control are essential due to their complex and expensive conditions for maintenance and repair. Conventionally, different sensors are used, which are typically positioned outside of the bearing. Thus, a rather low depth of information is achieved, and the bearing condition cannot be assessed optimally. Therefore, this article focuses on the production and evaluation of directly deposited thin-film strain sensor arrays on a rolling bearing within and close to the tribomechanical contact between roller and raceway. The sensor production was carried out using sputtering, photolithography and etching processes. After the static strain gauge characterization concerning temperature, strain and pressure sensitivity on different substrates, a sensor-integrated 81212 thrust roller bearing was investigated in an FE8 bearing test rig. After data processing, the dynamic measurements with a maximum Hertzian pressure of 1 GPa revealed negative sensor resistance changes of up to −1.4 ‰ in the tribomechanical contact and up to 3.8 ‰ positive resistance change right next to the contact zone. Due to the fact that these sensors were subject to wear, sensors were also positioned at a greater distance from the contact that still showed a measurable signal of 0.5 ‰ resistance change that can be used after critical loads when their signal has been correlated to the other sensors in the contact zone when the latter are worn. Furthermore, the time-resolution enables the precise measurement of the rotational speed, and deviations in the roller geometries can be detected as well due to different sensor amplitudes. The location-resolved measurements allow important information about the tribomechanical contact to be derived in real-time, thus enabling intelligent component control, for example concerning rotational speed, lubrication and load before a damage occurs.
Optimisation of radiographic visibility and wear detection of total knee arthroplasty inlays using radiopaque markers
(2025) Emonde, Crystal Kayaro ; Eggers, Max-Enno ; Heide, Klaas Maximilian; Pape, Florian ; Marian, Max; Hurschler, Christof ; Ettinger, Max ; Denkena, Berend
Wear of the inlay in total knee arthroplasty (TKA) contributes to implant failure and the need for revision surgery. In vivo wear assessment is challenging owing to the radiolucency of the inlay in standard radiographs. This study aimed to investigate the basic feasibility of integrating radiopaque X-ray markers on standard inlays to enhance their radiographic visibility and enable wear evaluation.Preliminary experiments identified optimal process parameters for micro-milling cavities on ultra-high molecular weight polyethylene (UHMWPE). A total of 450 parameter combinations were evaluated, with burr formation serving as the quality criterion. A process chain, comprising pre-contouring, micro-milling, filling cavities with radiopaque composite, and final contouring, was developed for inlay production. Eleven inlays with varying marker alignments, orientations, and geometries were manufactured, featuring grooves (≤0.8 mm wide) and holes (diameter = 1.6 mm), both 1 mm deep. Three HDPE + BaSO₄ composites (10, 20, and 30 wt.% BaSO₄) were formulated and assessed for radiopacity per ASTM F640-20. Final marker cavities were filled with HDPE + 20 wt.% BaSO₄ via pellet extrusion. The inlays were positioned in a phantom knee setup and radiographed in the anteroposterior view. Projected markers were evaluated based on edge visibility, measurability, homogeneity, and obscuration by the implant.None of the parameter combinations resulted in burr-free cavities, indicating an unstable five-axis process. X-ray images revealed that grooves aligned in the X-ray direction and drilled holes exhibited the best visibility for wear markers. Pin-on-plate tribological experiments revealed that BaSO₄ addition to pure HDPE reduced its CoF from 0.25 to 0.1, reaching a value comparable to UHMWPE (0.15), while also enhancing wear resistance.This study demonstrated the feasibility of integrating wear markers on standard TKA inlays by micro-milling cavities at different positions and orientations on the inlay surface and filling them with a radiopaque composite. Further research is required to optimise process parameters and investigate marker wear.
Residual stress engineering for highly loaded rolling-sliding contacts: Finding the sweet spot for maximum durability by hard turning and deep rolling
(2025) Dechant, Simon; Nordmeyer, Henke; Pape, Florian; Breidenstein, Bernd; Poll, Gerhard; Marian, Max
The durability of highly loaded rolling-sliding contacts, such as those in rolling bearings, is critically determined by subsurface microstructure and residual stresses engineered during manufacturing. This study systematically investigates the interplay between thermal and mechanical process parameters during deep rolling, using bearing inner rings as a representative example, to identify optimal conditions for maximizing fatigue life. By isolating the effects of process temperature (20–400 °C) and deep rolling pressure (200–400 bar), we demonstrate that moderate mechanical loading at room temperature can more than double bearing life through beneficial compressive residual stresses, while excessive pressure or thermal input above 200 °C sharply reduces durability. Notably, we reveal a previously unrecognized mechanism of hidden thermal degradation that limits lifetime, even when conventional hardness or microstructural metrics remain unchanged. These results define a process window for residual stress engineering in bearing steels and provide generic guidelines for hybrid manufacturing of rolling-sliding components subjected to severe tribological loading. The findings advance fundamental understanding of process-induced fatigue mechanisms and offer a framework for the rational design of subsurface-optimized, durable, and sustainable machine elements.
Self-Regenerative Mo-Based Solid Lubricant Coatings Deposited by APS as a PVD Alternative: Mechanical and Tribological Performance
(2025) Konopka, Dennis; Crespo Martins, Ricardo; Dukat, Mareike; Pape, Florian; Möhwald, Kai; Poll, Gerhard; Marian, Max
Solid lubricant coatings are essential for reducing friction and wear in tribo-mechanical systems, particularly in environments where traditional liquid lubricants can’t be used or fail. It has been reported in literature that self-regenerating physical vapor deposition (PVD) coatings can be designed in such a way that they continuously release MoO3 as a solid lubricant through tribo-oxidation. However, a disadvantage of PVD coatings is the limited layer thickness of just a few micrometers and thus the limited solid lubricant reservoir. In contrast, atmospheric plasma spraying (APS) allows the deposition of thicker reservoir layers, potentially extending service life under tribological stressing. Therefore, the aims of this study are to determine whether APS coatings with regenerative properties can be deposited on bearing steel and to assess their tribological performance. The mechanical, tribological, and structural behavior were analyzed using microindentation, ball-on-plate tribometer testing under dry conditions, optical and laser scanning, scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDX). Despite the relatively low hardness of the APS coating, excellent wear resistance protection was demonstrated at various loads and sliding velocities. Additionally, EDX analyses revealed that abrasive wear was prevented and a protective film was formed through tribo-oxidation, effectively shielding the surfaces. The results thus indicate the effectiveness of the APS coating and underline its potential for large-scale machine elements, such as rolling bearings.
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.

Browsing by Author "Pape, Florian "

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