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Browsing by Author "Marian, Max"

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2D materials for Tribo-corrosion and -oxidation protection: a review
(Elsevier B.V., 2024) Ramteke, Sangharatna M.; Walczak, Magdalena; De Stefano, Marco; Ruggiero, Alessandro; Rosenkranz, Andreas; Marian, Max
The recent rise of 2D materials has extended the opportunities of tuning a variety of properties. Tribo-corrosion, the complex synergy between mechanical wear and chemical corrosion, poses significant challenges across numerous industries where materials are subjected to both tribological stressing and corrosive environments. This intricate interplay often leads to accelerated material degradation and failure. This review critically assesses the current state of utilizing 2D nanomaterials to enhance tribo-corrosion and -oxidation behavior. The paper summarizes the fundamental knowledge about tribo-corrosion and -oxidation mechanisms before assessing the key contributions of 2D materials, including graphene, transition metal chalcogenides, hexagonal boron nitride, MXenes, and black phosphorous, regarding the resulting friction and wear behavior. The protective roles of these nanomaterials against corrosion and oxidation are investigated, highlighting their potential in mitigating material degradation. Furthermore, we delve into the nuanced interplay between mechanical and corrosive factors in the specific application of 2D materials for tribo-corrosion and -oxidation protection. The synthesis of key findings underscores the advancements achieved through integrating 2D nanomaterials. An outlook for future research directions is provided, identifying unexplored avenues, and proposing strategies to propel the field forward. This analysis aims at guiding future investigations and developments at the dynamic intersection of 2D nanomaterials, tribo-corrosion, and -oxidation protection.
A Neural Network for Fast Modeling of Elastohydrodynamic Line Contacts
(SSRN, 2024) Kelley, Josephine; Schneider, Volker; Marian, Max; Poll, Gerhard
When modeling bearings in the context of entire transmissions or drivetrains, there are practical limits to the calculation resources available to calculate single bearings or even contacts. In settings such as these, curve-fitting methods have historically been deployed to estimate the elastohydrodynamic lubrication conditions. Machine learning methods have the potential to enable more sophisticated physical modeling in the context of larger computation environments, as the evaluation time of a trained model is typically negligible. We present a neural network that accurately evaluates the elastohydrodynamic film pressure and film thickness and explore its applications. Employing a neural network for the EHL film thickness calculations can enable a more physically precise modeling strategy at almost no additional computational cost.
A Semantic Annotation Pipeline towards the Generation of Knowledge Graphs in Tribology
(2022) Kügler, Patricia; Marian, Max; Dorsch, Rene; Schleich, Benjamin; Wartzack, Sandro
Within the domain of tribology, enterprises and research institutions are constantly working on new concepts, materials, lubricants, or surface technologies for a wide range of applications. This is also reflected in the continuously growing number of publications, which in turn serve as guidance and benchmark for researchers and developers. Due to the lack of suited data and knowledge bases, knowledge acquisition and aggregation is still a manual process involving the time-consuming review of literature. Therefore, semantic annotation and natural language processing (NLP) techniques can decrease this manual effort by providing a semi-automatic support in knowledge acquisition. The generation of knowledge graphs as a structured information format from textual sources promises improved reuse and retrieval of information acquired from scientific literature. Motivated by this, the contribution introduces a novel semantic annotation pipeline for generating knowledge in the domain of tribology. The pipeline is built on Bidirectional Encoder Representations from Transformers (BERT)—a state-of-the-art language model—and involves classic NLP tasks like information extraction, named entity recognition and question answering. Within this contribution, the three modules of the pipeline for document extraction, annotation, and analysis are introduced. Based on a comparison with a manual annotation of publications on tribological model testing, satisfactory performance is verified.
Additive Manufacturing in the Maritime Industry: A Perspective on Current Trends and Future Needs
(2023) Garofalo, James; Shah, Raj; Thomas, Gavin; Shirvani, Khosro; Marian, Max; Rosenkranz, Andreas
Additive manufacturing (AM) has seen slow growth thus far in the maritime industry. Like other industries, maritime companies and institutions have started using AM for prototyping and product development needs but is now beginning to expand into production of end use parts and production tooling. The slow adoption can mainly be attributed to a previous lack of education in additive technology and strategies, current lack of reliability testing of additive machines in a marine environment, and the need for classification and certification of parts and machines before shipowners and crews will likely adopt for widespread use. This article provides a perspective of recent AM activities within the industry and discusses the need for research in key areas before widespread utilization can occur. Current use includes a recent push in maritime education, surveys of maritime workers and stakeholders, and fabrication of replacement parts, propellers, and boat hulls. Prospective key areas with the need for further research include 1) use-cases for replacement parts on ship, 2) economic feasibility of putting 3D printers on board, 3) standards, certification, and quality assurance, and 4) reliability and repeatability in a marine environment
Additively manufactured MAX- and MXene-composite scaffolds for bone regeneration- recent advances and future perspectives
(2023) Khabisi, Minufar Abdollahi; Shirini, Farhad; Shirini, Kasra; Khorsand, Hamid; Marian, Max; Rosenkranz, Andreas
Human bones can suffer from various injuries, such as fractures, bone cancer, among others, which has initiated research activities towards bone replacement using advanced bio-materials. However, it is still challenging to design bio-scaffolds with bone-inducing agents to regenerate bone defects. In this regard, MAX-phases and MXenes (early transition metal carbides and/or nitrides) have gained notable attention due to their unique hydrophilicity, bio-compatibility, chemical stability, and photothermal properties. They can be used in bone tissue engineering as a suitable replacement or reinforcement for common bio-materials (polymers, bio-glasses, metals, or hydroxyapatite). To fabricate bio-scaffolds, additive manufacturing is prospective due to the possibility of controlling porosity and creating complex shapes with high resolution. Until now, no comprehensive article summarizing the existing state-of-the-art related to bone scaffolds reinforced by MAX-phases and MXenes fabricated by additive manufacturing has been published. Therefore, our article addresses the reasons for using bone scaffolds and the importance of choosing the most suitable material. We critically discuss the recent developments in bone tissue engineering and regenerative medicine using MAX-phases and MXenes with a particular emphasis on manufacturing, mechanical properties, and bio-compatibility. Finally, we discuss the existing challenges and bottlenecks of bio-scaffolds reinforced by MAX-phases and MXenes before deriving their future potential.
Application of machine learning for film thickness prediction in elliptical EHL contact with varying entrainment angle
(2024) Tosic, Marko; Marian, Max; Habchi, Wassim; Lohner, Thomas; Stahl, Karsten
This contribution demonstrates the potential of machine learning (ML) algorithms in predicting elastohydrodynamic lubrication (EHL) film thickness in elliptical contact with varying direction of lubricant entrainment, ranging from wide to slender elliptical configurations. The input parameters pertain to worm gear contacts, which are characterized by slender-like elliptical contact between a steel and a soft metal component. The study encompasses generating a database using numerical Finite Element Method (FEM) simulations, training artificial neural network (ANN) models, and evaluating their performance in terms of bias and variance. Key outcomes include the successful training of the ANN models, detailed analysis of the impact of tailored architecture on the ANN models' performance, and the superiority of the ANN compared to other ML regression algorithms. The study further identifies key input parameters that influence prediction accuracy and introduces a strategic dataset augmentation procedure to increase local and overall prediction accuracy. This strategic dataset augmentation enhances model robustness and precision while providing insights for expanding databases collaboratively. It holds potential for broader applications of ML for performance prediction of tribological contacts, thus paving the way for advanced ML models that consider additional factors and collaborative databases refined by multiple research groups.
Beyond Starvation: Amplitude-Dependent Grease Replenishment Mechanisms in Oscillating Rolling Bearings
(2025) Liu, Muyuan; Wandel, Sebastian; Bader, Norbert; Lin, Zongyu; Bayer, Gernot; Poll, Gerhart; Marian, Max
This experimental study addresses grease replenishment mechanisms under varying oscillation amplitudes for deep groove ball bearings with different cage structures. This is complemented by an optical elastohydrodynamic lubrication tribometer. Thereby, three distinct lubrication mechanisms are identified. At small amplitudes, lubrication of the contact area is primarily determined by the lubricant supply from the grease side bands. Under medium-amplitude conditions, interaction between the cage and the side bands on the rolling elements substantially enhances lubrication. At large amplitudes, when the rolling track on the rolling elements connects both the inner and outer rings, grease flow between the rings emerges as a dominant mechanism, effectively reducing wear.
Beyond starvation: Amplitude-dependent grease replenishment mechanisms in oscillating rolling bearings
(2025) Liu, Muyuan; Wandel, Sebastian; Bader, Norbert; Lin, Zongyu; Bayer, Gernot; Poll, Gerhard; Marian, Max
Oscillating bearings find applications in various industries, including robotics and wind energy systems. Damage due to starvation can lead to system failures in highly precise positioning mechanisms due to unpredictable torque fluctuations. Moreover, wear damage can trigger secondary failure mechanisms. The occurrence of starvation is dependent on operating parameters, such as oscillation frequency, amplitude, load, and lubricant characteristics. Among these factors, amplitude has been identified as the most critical parameter affecting grease starvation and can even overshadow the effects of other variables. Therefore, investigating the impact of amplitude on lubrication performance is essential for optimizing the lubrication design of oscillating bearings. Hence, this experimental study addresses grease replenishment mechanisms under varying oscillation amplitudes for 6008 deep groove ball bearings with different cage structures. This is complemented by in-situ observations of film thickness formation using an optical elastohydrodynamic lubrication tribometer. Thereby, three distinct lubrication mechanisms are identified. At small amplitudes, lubrication of the contact area is primarily determined by the lubricant supply from the grease side bands. Under medium-amplitude conditions, interaction between the cage and the side bands on the rolling elements substantially enhances lubrication. At large amplitudes, when the rolling track on the rolling elements connects both the inner and outer rings, grease flow between the rings emerges as a dominant mechanism, effectively reducing wear. Understanding the above mechanisms provides a theoretical foundation for the selection of lubricating grease based on amplitude, and the structural optimization of bearings, including cage or raceways.
Bio-tribological characterization of additives in synovial fluid - usage of graphene, Ti3C2Tx and their synergistic effects
(2025) Ramteke R., Sangharatna Munneshwar; Ugarte Muñoz, Alfonso E.; Zambrano, Dario F.; Ramos Grez, Jorge; Rosenkranz, Andreas; Marian, Max
Synovial joints play a crucial role in limb biomechanics, depending on advanced lubrication systems to reduce wear. However, disruptions caused by injury or disease often led to the need for joint replacements. Although additive manufacturing enables the production of customized implants, achieving optimal wear resistance is still a significant challenge. This research explores the use of nano-additives in synovial fluid (SF). In this context, we examine the dispersion stability, surface wettability, dynamic viscosity, and bio-tribological behavior of SF enhanced by graphene (G), MXene (Ti3C2Tx), and their hybrid (G-Ti3C2Tx) in the concentrations of 0.5, 2, and 10 mg/mL, respectively. Results show that G and the hybrid maintained stable dispersions in SF, while Ti3C2Tx shows slight sedimentation at lower concentrations. Both G and Ti3C2Tx substantially improved wettability, with the most pronounced effect observed at 10 mg/mL for Ti3C2Tx (29.8 % reduction in contact angle). The bio-tribological analysis indicates that the hybrids induced a superior wear resistance (78.3 % wear reduction at 2 mg/mL). These findings highlight the potential of hybrid, in enhancing the bio-tribological properties of SFs, which is highly prospective to enhance knee prostheses and arthritis management.
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.
Biotribological Performance of Multilayer Ti- and Mo-Based MXene Coatings
(2025) Ramteke R., Sangharatna Munneshwar; Molina, Ricardo; Zambrano, Dario F.; Marian, Max; Rosenkranz, Andreas
Metallic materials are extensively utilized in biomedical implants due to their excellent strength and corrosion resistance. However, friction and wear-related issues remain important challenges in load-bearing implant applications. To address these concerns, multilayer Ti3C2T x , Mo2TiC2T x , and Mo2Ti2C3T x coatings were deposited onto stainless steel substrates in two distinct thickness ranges (lower: similar to 100 to 150 nm; higher: similar to 225 to 275 nm) and biotribologically tested under simulated body fluid lubrication conditions. Our results revealed that low coating thicknesses of Mo2TiC2T x demonstrated the most favorable biotribological performance, reducing the wear rate by up to 33% and consistently lowering the coefficient of friction, with reductions of up to 56% compared to uncoated references, owing to their ability to form durable tribo-films under SBF lubrication. In contrast, Ti3C2T x coatings increased friction and wear under considered conditions, while Mo2Ti2C3T x showed a moderate COF reduction but higher wear rates, particularly at higher coating thicknesses and loads. These findings emphasize the superior self-lubricating properties of Mo2TiC2T x coatings, thus highlighting their potential to enhance the durability and longevity of load-bearing biomedical implants.
Combined Effect of Surface Irregularities and Applied Voltage on the Behavior of Hole-Entry Spherical Hybrid Journal Bearings Lubricated With an Electro-Rheological Fluid
(2024) Tomar, Adesh Kumar; Sahu, K.; Sharma, S. C.; Marian, Max
Surface irregularities substantially affect the performance of tribological systems. The influence of three-dimensional surface irregularities on the behavior of hole-entry spherical hybrid journal bearings has been investigated. Recently, smart fluids have been employed in several applications to improve their performance. The interactive effect of electrorheological (ER) fluid and surface irregularities has also been studied. The modified Reynolds equation and restrictor flow equation have been solved using the finite element technique with appropriate boundary conditions. The results show that consideration of surface irregularities on the bearing surface enhances bearing stability. Spherical hybrid journal bearings lubricated by ER fluid increase minimum fluid film thickness and minimize the possibility of metal-to-metal contact. It is found that the combined effect of surface irregularities and ER fluid significantly improved the bearing performance parameters than individual behavior. The bearing designer is anticipated to benefit from the current model.
Combining multi-scale surface texturing and DLC coatings for improved tribological performance of 3D printed polymers
(2023) Marian, Max; Zambrano, Dario F.; Rothammer, Benedict; Waltenberger, Valentin; Boidi, Guido; Krapf, Anna; Merle, Benoit; Stampfl, Jürgen; Rosenkranz, Andreas; Gachot, Carsten; Grützmacher, Philipp G.
Polymer components fabricated by additive manufacturing typically show only moderate strength and low temperature stability, possibly leading to severe wear and short lifetimes especially under dry tribological sliding. To tackle these shortcomings, we investigated the combination of single- and multi-scale textures directly fabricated by digital light processing with amorphous diamond-like carbon (DLC) coatings. The topography of the samples and conformity of the coatings on the textures are assessed and their tribological behaviour under dry conditions is studied. We demonstrate that the surface textures have a detrimental tribological effect on the uncoated samples. This changes with the application of DLC coatings since friction substantially reduces and wear of the textures is not observed anymore. These trends are attributed to the protection of the underlying polymer substrate by the coatings and a reduced contact area. The best tribological performance is found for a coating with highest hardness and hardness-to-elasticity ratios. Moreover, multi-scale textures perform slightly better than single-scale textures due to a smaller real contact area. Summarizing, we verified that the high flexibility and low production costs of 3D printing combined with the excellent mechanical and tribological properties of DLC results in synergistic effects with an excellent performance under dry sliding conditions
Combining surface textures and MXene coatings—towards enhanced wear-resistance and durability
(2022) Rosenkranz, Andrea; Marian, Max
Surface texturing has gained significant attention over the last 30 years to tailor friction and wear under various tribological conditions in fundamental and applied tribological systems. Under dry conditions, surface textures help to improve friction or wear by reducing adhesion and the real area of contact as well as trapping wear particles. However, especially under high load conditions, surface textures rapidly wear away, thus losing their friction- and wear-reducing capability. A potential strategy to improve their durability under more severe conditions is the combination with protective solid lubricant coatings. In this regard, MXene nano-sheets are the most recent success story related to 2D materials as solid lubricant coatings. They appear particularly interesting due to their ability to generate low-friction and wear-resistant tribo-films thus providing an excellent durability and wear resistance. This aspect makes the combination of MXene solid lubricant coatings and surface textures highly prospective. Therefore, this perspective aims at summarizing and analyzing the existing state-of-the art related to the combined use of surface textures and MXene coatings.
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.
Designing amorphous carbon coatings using numerical and experimental methods within a multi-scale approach
(2020) Tremmel, Stephan; Marian, Max; Rothammer, Benedict; Weikert, Tim; Wartzack, Sandro
Amorphous carbon coatings have the potential to effectively reduce friction and wear in tribotechnical systems. The appropriate application of amorphous carbon layers requires both, a very good understanding of the tribological system and knowledge of the relationships between the fabrication of the coatings and their properties. In technical practice, however, the coatings’ development and their selection on the one hand and the design of the tribological system and its environment on the other hand are usually very strongly separated. The present work therefore aims to motivate the integrated development of tribotechnical systems with early consideration of the potential of amorphous carbon coatings. An efficient integrated development process is presented, which makes it possible to determine the boundary conditions and the load collective of the tribological system based upon an overall system and to derive the requirements for a tailored coating. In line with the nature of tribology, this approach must cover several scales. In this respect, the development process follows a V-model. The left branch of the V-model is mainly based upon a simulation chain including multibody and contact simulations. The right branch defines an experimental test chain comprising coating characterization to refine the contact simulation iteratively and tribological testing on different levels to validate the function fulfillment. Within this contribution, the outlined approach is illustrated by two use cases, namely the cam/tappet-pairing and the total knee replacement.
Diamond-like Carbon coatings for artificial implants
(Wiley, 2025) Rothammer, Benedict; Marian, Max
This chapter delves into the enhancement of implant performance through diamond-like carbon (DLC) coatings, recognized for their exceptional mechanical, chemical, and biocompatible properties, making them ideal for various biomedical applications. The chapter focuses on orthopedic applications, where DLC coatings improve wear resistance and longevity of implants, and promote osteointegration by enhancing cell adhesion and proliferation. In dental implants, DLC coatings boost biocompatibility and reduce infection risk, while also enhancing the durability of orthodontic brackets. This chapter details the requirements for DLC coatings in artificial implants and reviews their use in load bearing and dental implants, respectively. The chapter concludes with a summary of findings and identifies future research challenges, emphasizing the need for translating model-level advancements to component-level applications and addressing the reproducibility issues in dental applications. Overall, DLC coatings show significant potential to improve patient outcomes, reduce revision surgeries, and enhance comfort in both orthopedic and dental medicine.
Effect of Harmful Bearing Currents on the Service Life of Rolling Bearings: From Experimental Investigations to a Predictive Model
(2024) Schneider, Volker; Krewer, Marius; Poll, Gerhard; Marian, Max
This study investigates the effects of harmful bearing currents on the service life of rolling bearings and introduces a model to predict service life as a function of surface roughness. Harmful bearing currents, resulting from electrical discharges, can cause significant surface damage, reducing the operational lifespan of bearings. This study involves comprehensive experiments to quantify the extent of electrical stress caused by these currents. For this purpose, four series of tests with different electrical stress levels were carried out and the results of their service lives were compared with each other. Additionally, a novel model to correlate the service life of rolling bearings with varying degrees of surface roughness caused by electrical discharges was developed. The basis is the internationally recognized method of DIN ISO 281, which was extended in the context of this study. The findings show that the surface roughness continues to increase as the electrical load increases. In theory, this in turn leads to a deterioration in lubrication conditions and a reduction in service life.
Effect of re-melted textured patterns on the mechanical and tribological behavior of 70Mn steel
(Springer Science and Business Media Deutschland GmbH, 2025) Chen, Yazhe; Shang, Qingyu; Zhang, Youwei; Yao, Ying; Tomar, Adesh Kumar; Long, Risheng; Marian, Max
© 2025, Emerald Publishing Limited.Purpose: This study aims to investigate the mechanical and tribological behavior of 70Mn steel with different laser re-melted textured patterns. Design/methodology/approach: Laser surface re-melting (LSR) was used to manufacture various textured patterns (i.e. line, grid and mixed) on both the original and heat-treated 70Mn steel plates. The micro-hardness, microstructure, tensile strength, yield strength, elongation, coefficients of friction (COF) and worn morphologies were characterized to evaluate the impact of different textured patterns on the overall performance. Findings: The results show that re-melted unit exhibited the highest surface hardness on the subsurface. The increase in surface hardness of the re-melted unit for the heat-treated 70Mn steel samples was much lower than that of the original ones. The re-melted textured patterns did not improve the tensile strength, yield strength and elongation of either original or heat-treated 70Mn steel samples. The re-melted textured patterns effectively reduced the average COFs of heat-treated 70Mn steel samples, but increased friction of the non-heat-treated samples. Originality/value: This study provides valuable insights into enhancing the mechanical properties and tribological characteristics of 70Mn steel, particularly in the automotive, heavy machinery and high-load application sectors. These industries have stringent requirements for durability and friction control, and the findings of this research are expected to effectively extend the lifespan of mechanical components. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2024-0443/
Effects of Grooved Surfaces and Lubrication Media on the Performance of Hybrid Gas Journal Bearings
(2025) Kumar Tomar, Adesh; Sahu, Krishnkant; Sharma, Satish C.; Marian, Max
Gas bearings are attractive for sustainable, high-speed, and cryogenic applications, where gases replace liquid lubricants. This study numerically analyzed hybrid gas journal bearings lubricated with hydrogen, nitrogen, air, and helium, and quantifies the impact of circumferential micro-grooves. The compressible Reynolds equation was solved by the finite element method with constant-flow valve restrictors, while Gauss–Seidel iterations were used for convergence. The model was verified against published theoretical and experimental data with maximum deviations below 6%, and mesh independence is confirmed. The parametric results show that the gas type and texturing jointly controlled static and dynamic performance. Helium (highest viscosity) yielded the largest minimum film thickness, whereas hydrogen (lowest viscosity) attained higher peak pressures at a lower film thickness for a given load. Grooves redistributed pressure and reduced both the maximum pressure and the minimum film thickness, but they also lowered the frictional torque. Quantitatively, the hydrogen-lubricated grooved bearing reduced the frictional torque by up to 50% compared with the non-grooved air-lubricated bearing at the same load. Relative to air, hydrogen increased stiffness and damping by up to 10% and 50%, respectively, and raised the stability threshold speed by 110%. Conversely, grooves decreased the stiffness, damping, and stability threshold speed compared with non-grooved surfaces, revealing a trade-off between friction reduction and dynamic stability. These findings provide design guidance for selecting gas media and surface texturing to tailor hybrid gas journal bearings to application-specific requirements.

Browsing by Author "Marian, Max"

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