Academic literature on the topic 'Specific surface bearing'
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Journal articles on the topic "Specific surface bearing"
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Zika, T., I. C. Gebeshuber, F. Buschbeck, G. Preisinger, and M. Gröschl. "Surface analysis on rolling bearings after exposure to defined electric stress." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 223, no. 5 (March 18, 2009): 787–97. http://dx.doi.org/10.1243/13506501jet538.
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This article gives an overview about classical and frequency converter-induced spurious bearing currents in induction machines and discusses typical damage patterns caused by the current passage. To investigate on the electric damage mechanisms, test bearings are operated in a test rig and exposed to specific (classical low-frequency, and high-frequency) bearing currents. The induced damages to the surfaces are analysed visually and with the help of an atomic force microscope, and compared for the different electric regimes applied. Further, the electrically damaged bearing surfaces are characterized by standard roughness parameters. The surface structure observable on certain test bearings shows good correlation to the structure found with a bearing that had failed in the field under similar electric conditions. One of the investigated electric regimes applying high-frequency currents proved capable of generating fluting patterns - as found in real applications - on the test rig. The experiments also indicate that high-frequency bearing currents, although in total dissipating less energy, are more dangerous to a bearing than continuous current flow. The presented method gives a good starting point for further investigation on electric current damage in bearings, especially regarding high-frequency bearing currents, and on bearing/grease lifetime under specific electric regimes.
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Mizobe, Koshiro, Masahiro Takamiya, Takashi Honda, Hitonobu Koike, Edson Costa Santos, Yuji Kashima, and Katsuyuki Kida. "Fourier Transform Infrared Spectroscopy for Wear Debris Adhesion on PEEK Bearing Surface." Applied Mechanics and Materials 307 (February 2013): 372–76. http://dx.doi.org/10.4028/www.scientific.net/amm.307.372.
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Polyetheretherketone (PEEK), a tough semi-crystalline thermoplastic polymer with excellent mechanical properties and polytetrafluoroethylene (PTFE), valued for its low friction coefficient are popular materials used for the production of bearings. In this work, rolling contact fatigue (RCF) tests were performed in order to investigate wear on bearing surfaces by using the Fourier Transform Infrared Spectroscopy (FT-IR). It is reported that PEEK’s specific peak at 1243cm-1was shifted and PEEK’s polymer bearing crystalline content level on wear surface remained unchanged by contact stress or wear debris adhesion.
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Chen, Long, Fei Xing, Yuanzheng Wang, Rui He, Jingming He, Yunwen Xu, Cheng Wang, et al. "Outcome analysis of various bearing surface materials used in total hip replacement." Materials Express 10, no. 3 (March 1, 2020): 301–13. http://dx.doi.org/10.1166/mex.2020.1651.
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Since the first total hip replacement (THR) in 1938 by Philip Wiles, prosthesis materials and THR surgical technologies have developed rapidly. In this review, we use internationally-published research to synthesize a comprehensive analysis of the specific characteristics and clinical outcomes of different bearing surfaces used in THR. Polyethylene, metallic alloys, and ceramic have become the three most commonly used hip prosthesis bearing surfaces after decades of hip implant development. Different bearing surface types have varying characteristics that offer specific benefits and risks of complication. A thorough understanding of the unique properties and possible complications of each type of bearing surface is critical to surgeons tasked with selecting appropriate implant materials for total hip replacement.
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Schüler, Eckhard, and Olaf Berner. "Improvement of Tilting-Pad Journal Bearing Operating Characteristics by Application of Eddy Grooves." Lubricants 9, no. 2 (February 10, 2021): 18. http://dx.doi.org/10.3390/lubricants9020018.
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In high speed, high load fluid-film bearings, the laminar-turbulent flow transition can lead to a considerable reduction of the maximum bearing temperatures, due to a homogenization of the fluid-film temperature in radial direction. Since this phenomenon only occurs significantly in large bearings or at very high sliding speeds, means to achieve the effect at lower speeds have been investigated in the past. This paper shows an experimental investigation of this effect and how it can be used for smaller bearings by optimized eddy grooves, machined into the bearing surface. The investigations were carried out on a Miba journal bearing test rig with Ø120 mm shaft diameter at speeds between 50 m/s–110 m/s and at specific bearing loads up to 4.0 MPa. To investigate the potential of this technology, additional temperature probes were installed at the crucial position directly in the sliding surface of an up-to-date tilting pad journal bearing. The results show that the achieved surface temperature reduction with the optimized eddy grooves is significant and represents a considerable enhancement of bearing load capacity. This increase in performance opens new options for the design of bearings and related turbomachinery applications.
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Mukutadze, M. A., M. V. Novakovich, and N. S. Zadorozhnaya. "Computational Model for Radial Plain Bearing with Non-Circular Bearing Surface Profile and Fusible Coating on Shaft Surface." Journal of Physics: Conference Series 2096, no. 1 (November 1, 2021): 012023. http://dx.doi.org/10.1088/1742-6596/2096/1/012023.
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Abstract The paper presents a study based upon: a Newtonian fluid flow equation (“thin layer”), a continuity equation, and an equation of the molten-profile radius for a shaft coated with a fusible metal alloy; considering a mechanical energy dissipation rate formula, the authors produced an asymptotic and accurate automodel solution for the zero approximation (melting ignored) and first approximation (adjusted for melting) of a radial plain bearing featuring a fusible metal coating and a bearing profile adapted to the specific friction parameters. The paper further presents analytical dependencies describing the molten surface radius, velocity and pressure fields for zero and first approximation. Besides, it determines the key operating parameters of the frictional couple, the bearing capacity, and the friction. It also shows how the parameters arising from the melting of the surface affect the bearing capacity and friction where the bearing surface profile is adapted to the specific conditions of friction.
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Hagemann, Thomas, Huanhuan Ding, Esther Radtke, and Hubert Schwarze. "Operating Behavior of Sliding Planet Gear Bearings for Wind Turbine Gearbox Applications—Part II: Impact of Structure Deformation." Lubricants 9, no. 10 (October 1, 2021): 98. http://dx.doi.org/10.3390/lubricants9100098.
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The use of planetary gear stages intends to increase power density in drive trains of rotating machinery. Due to lightweight requirements on this type of machine elements, structures are comparably flexible while mechanical loads are high. This study investigates the impact of structure deformation on sliding planet gear bearings applied in the planetary stages of wind turbine gearboxes with helical gears. It focuses on three main objectives: (i) development of a procedure for the time-efficient thermo-elasto-hydrodynamic (TEHD) analysis of sliding planet gear bearing; (ii) understanding of the specific deformation characteristics of this application; (iii) investigation of the planet gear bearing’s modified operating behavior, caused by the deformation of the sliding surfaces. Generally, results indicate an improvement of predicted operating conditions by consideration of structure deformation in the bearing analysis for this application. Peak load in the bearing decreases because the loaded proportion of the sliding surface increases. Moreover, tendencies of single design measures, determined for rigid geometries, keep valid but exhibit significantly different magnitudes under consideration of structure deformation. Results show that consideration of structure flexibility is essential for sliding planet gear bearing analysis if quantitative assertions on load distributions, wear phenomena, and interaction of the bearing with other components are required.
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Cahyo, Nur, P. Paryanto, Ariyana Dwiputra Nugraha, Arionmaro Simaremare, Indra Ardhanayudha Aditya, Bara Songka Laktona Siregar, and Mohammad Tauviqirrahman. "Effect of Engineered Roughness on the Performance of Journal Bearings Lubricated by Bingham Plastic Fluid Using Computational Fluid Dynamics (CFD)." Lubricants 10, no. 12 (November 25, 2022): 333. http://dx.doi.org/10.3390/lubricants10120333.
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A journal bearing is a machine element that is used to keep the shaft rotating about its axis. The increasing demand for journal bearing applications in high-speed machines that are efficient and economical has resulted in the need for improvements to the acoustic and tribological performance of journal bearings. In order to improve the tribological and acoustic performance, this study aims to propose a novel journal bearing design by introducing a roughness condition in a specific zone of the stationary bearing surface. In addition, the impact of the application of engineered roughness on the performance of Bingham-plastic-lubricated bearings is investigated in more detail. Considering the effect of cavitation, the analysis was conducted using a 3D computational fluid dynamics (CFD) model of a journal bearing. In comparison with the Reynolds equation—which is inertialess—for lubrication analysis, the use of a 3D CFD model based on Navier–Stokes equations reflects more detailed flow characteristics. Moreover, in this work, variations in the area of surface roughness were employed, resulting in various roughness patterns on the surface of the journal bearing, so that the acoustic and tribological performances of the journal bearing were anticipated to be enhanced. The findings of this study show that under non-Newtonian lubrication of the bearing, the engineered roughness has a strong effect in altering the tribological performance. Furthermore, the well-chosen roughened surface was proven to be more pronounced in enhancing the load support and reducing the friction force. The simulation results also show that using an engineered surface has little effect on the noise of the bearing.
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Pandey, Shashikant, and Muniyappa Amarnath. "Applications of vibro-acoustic measurement and analysis in conjunction with tribological parameters to assess surface fatigue wear developed in the roller-bearing system." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 235, no. 10 (January 8, 2021): 2034–55. http://dx.doi.org/10.1177/1350650120982465.
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Rolling-element bearings are the most commonly used components in all rotating machinery. The variations in the operating conditions such as an increase in the number of operating cycles, load, speed, service temperature, and lubricant degradation result in the development of various defects such as pitting, spalling, scuffing, scoring, etc. The defects that appeared on rolling contact surfaces cause surface deterioration and change in the vibration and sound levels of the bearing system. The present experimental investigations are aimed at assessing the surface fatigue wear that appears on the contact surfaces of roller bearings. The studies considered the estimation of specific film thickness, analysis of surface fatigue wear developed on the rolling-element surfaces, surface roughness analysis, grease degradation analysis using Fourier transform infrared radiation, and vibration and sound signal measurement and analysis. The results obtained from the experimental investigation provide a good correlation between surface wear, vibration, and sound signals with a transition in the lubrication regimes in the Stribeck curve.
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Perumalla, Sateesh Kumar, Amarnath Muniyappa, and Aravindan Sivanandam. "Applications of microwave heat treatment process to enhance the surface properties of bronze and steel materials used in journal bearing." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 10 (January 27, 2020): 2064–76. http://dx.doi.org/10.1177/0954406220902169.
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Journal bearings are important conformal sliding contact machine elements widely used in industrial applications to support cylindrical shafts subjected to radial loads. Wear in journal bearings propagate due to increase in fatigue load cycles, lubricant degradation, misalignment, etc. Hence, it is important to minimize the occurrence of wear in journal bearings by improving their mechanical properties. Microwave heat treatment process is one of the recent developments emerged to improve the surface properties of materials in which energy is directly delivered to the material surface through molecular interaction with the electromagnetic field. In the present work, microwave heat treatment process was used to improve the performance of journal and bearing materials. Further, the microwave-treated journal and bearing specimens were used to conduct performance evaluation experiments under hydrodynamic lubrication regime operating condition. Results highlighted the importance of microwave treatment to reduce wear in both journal and bearing components. A significant reduction in friction coefficient and specific wear rate values were obtained, which resulted in a considerable improvement in the operating performance of the journal bearing system with respect to the increase in fatigue load cycles.
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Sy Truong, Dinh, Byung-Sub Kim, and Jong-Kweon Park. "Thermally affected stiffness matrix of angular contact ball bearings in a high-speed spindle system." Advances in Mechanical Engineering 11, no. 11 (November 2019): 168781401988975. http://dx.doi.org/10.1177/1687814019889753.
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Bearing stiffness directly affects the dynamic characteristics in a high-speed spindle system and plays an important role in terms of manufacturing quality. We developed a new approach for predicting the thermal behavior of a high-speed spindle, calculated the thermal expansion, and generated a bearing stiffness matrix for angular contact ball bearings. The heat convection of spindle housing in air, the balls in lubricant, the spindle shaft in quiescent air, and the bearing inner ring surfaces were determined. Heat sources such as bearing friction, and the heat contributed by the built-in motor, were simulated using an analysis systems (ANSYS) steady-state thermal model. The results were imported into a static ANSYS structural model. Ball thermal expansion was calculated based on changes in the coordinates of nodal points on the ball surface. Finally, a thermally affected bearing stiffness matrix was generated by applying the Newton–Raphson technique. Decreases in the bearing radial, axial, angular, and coupling stiffness values as rotational spindle speed increased were calculated. Also, the stiffness coefficients at a specific speed increased significantly caused by the thermal effects. Finally, for validation, the bearing stiffness was compared to that calculated using an earlier thermal network approach.
Dissertations / Theses on the topic "Specific surface bearing"
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Katika, Konstantina, Mouadh Adassi, Mohammad Monzurul Alam, and Ida Lykke Fabricius. "Changes in specific surface as observed by NMR, caused by saturation of chalk with porewater bearing divalent ions: Changes in specific surface as observed by NMR, caused by saturation of chalk with porewater bearing divalent ions." Diffusion fundamentals 22 (2014) 4, S. 1-14, 2014. https://ul.qucosa.de/id/qucosa%3A13478.
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Nuclear Magnetic Resonance (NMR) spectrometry has proved to be a good technique for determining the petrophysical properties of reservoir rocks; such as porosity and pore size distribution. We investigated how pore water rich in divalent ions affect the NMR signal from chalk with two different depositional textures. We compared two cases. The first experiments on outcrop chalk with high salinity brines showed that saturation with divalent ions (Mg2+, Ca2+ and SO4 2-) cause major shifts in the T2 distribution curve, probably due to precipitation in the pore space. In a second set of experiments, fluid samples where precipitation takes place were found to show shifts in the T2 relaxation curve due to the creation of crystals. We were able to identify how differences in the rock texture and precipitants within the pore space may affect the transverse relaxation time by altering the surface-to-volume ratio of the pore space. The results of this work could benefit the ongoing study on the optimization of the water composition for Enhanced Oil Recovery (EOR) methods and shed light on how it can affect the mechanical and physical properties of the rock.
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Katika, Konstantina, Mouadh Adassi, Mohammad Monzurul Alam, and Ida Lykke Fabricius. "Changes in specific surface as observed by NMR, caused by saturation of chalk with porewater bearing divalent ions." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-178591.
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Nuclear Magnetic Resonance (NMR) spectrometry has proved to be a good technique for determining the petrophysical properties of reservoir rocks; such as porosity and pore size distribution. We investigated how pore water rich in divalent ions affect the NMR signal from chalk with two different depositional textures. We compared two cases. The first experiments on outcrop chalk with high salinity brines showed that saturation with divalent ions (Mg2+, Ca2+ and SO4 2-) cause major shifts in the T2 distribution curve, probably due to precipitation in the pore space. In a second set of experiments, fluid samples where precipitation takes place were found to show shifts in the T2 relaxation curve due to the creation of crystals. We were able to identify how differences in the rock texture and precipitants within the pore space may affect the transverse relaxation time by altering the surface-to-volume ratio of the pore space. The results of this work could benefit the ongoing study on the optimization of the water composition for Enhanced Oil Recovery (EOR) methods and shed light on how it can affect the mechanical and physical properties of the rock.
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Cavenett, Sally Jane. "The effectiveness of total surface bearing compared to specific surface bearing prosthetic socket design on health outcomes of adults with a trans-tibial amputation: a systematic review." Thesis, 2014. http://hdl.handle.net/2440/91289.
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Background Lower-limb prostheses enable life participation for people with amputation. The aim of this systematic review was to synthesise evidence on the effectiveness of total surface bearing (TSB) compared with specific surface bearing (SSB) prosthesis designs on health outcomes. Inclusion criteria Types of participants Trans-tibial amputees aged 14 years and older utilising a TSB or SSB prosthesis. Types of interventions and comparators The intervention was the TSB and the comparator was the SSB design. Types of studies This review considered all relevant quantitative study designs. Outcomes and outcome measures Outcome measures relating to function and mobility, comfort and pain, quality of life and energy expenditure were considered. Search strategy A three-step search strategy across 13 databases and discipline-specific resources was pursued. Published and unpublished studies in English were considered, from database inception to June 2012. Methodological quality Two independent reviewers, using the Joanna Briggs Institute MAStARI appraisal checklists, undertook critical appraisal. Data collection Data about interventions, populations, study methods and outcomes of significance were extracted using the MAStARI tool from the Joanna Briggs Institute. Data synthesis Quantitative data was pooled in statistical meta-analysis using the Cochrane Review Manager Version 5.2 where possible. Where not possible, findings were presented using narrative and tables. Results This review identified and analysed 28 measures assessing the health domains, presenting mixed findings. Twenty-one measures found no difference between socket designs; four found a significant difference favouring the TSB and three found a significant difference favouring the SSB design. Suspension and interface variation was found. Sub-group analysis assessed TSB with gel interface and SSB with foam interface, to examine interface influence. Four measures found no difference and two measures, walking speed and cadence, found a significant difference favouring the TSB design. Further sub-group analysis assessing the influence of pin suspension with TSB compared to supra-condylar suspension with SSB found significant difference favouring TSB design for walking speed and socket preference outcomes. Conclusions The available evidence on the effectiveness of prosthetic socket designs suggests no clear choice between the TSB and SSB. This may be due to variation in interface and suspension utilised. Interpreting the findings, the TSB was as effective as the SSB design in improving health outcomes relating to function, comfort and quality of life. Implications for Practice In finding that the TSB is as effective as the SSB design in improving health outcomes implies that prescription may depend on clinician knowledge and skill-set, funding availability and patient preference. Prosthetists require the skill-set to deliver the TSB design. TSB prescription involves a gel interface, with additional costs; therefore funding is required to enable this prescription. Implications for Research Additional high quality studies involving a larger sample size, across aetiologies are required. Consistency in measures is critical to facilitate comparison and enhance meta-analysis. Studies on cost-effectiveness of socket designs are required to inform choice from a societal perspective.Thesis (M.Clin.Sc.) -- University of Adelaide, School of Translational Health Science, 2014
Books on the topic "Specific surface bearing"
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Krasnopolskaia, Iuliia. Design and Parametric Modeling of Pretensioned and Stiffened Membranes Project Work. Technische Universität Dresden, 2021. http://dx.doi.org/10.25368/2022.407.
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This research aimed to develop conceptually the pretensioned and stiffened membrane structures, using an experimental approach and computer simulation. The physical method of form finding included the pretensioned fabric with the glued grid made of the wooden sticks. Relaxation of the stressed membrane contributed to forming the specific anticlastic hyparic surface by energy release. The influence of the rigid elements pattern, intensity and direction of pretensioning on the final shape was investigated. The tensegrity structures were also built applying the same form finding way. These experiments led to the modelling of resulting samples with parametric design tools, namely Rhino and Grasshopper. Optimization of the final shape was carried out by changing parameters such as stiffenings configuration and membrane strength. This digital approach demonstrated successful simulation and rationalization of considered structures. Moreover, the final models can be used for further structural analysis and BIM. Considered membrane structures have very efficient load-bearing behavior. They are characterized by small weight, high light transmission and the ability to create large usable spaces free from columns. The most dangerous loads for membrane structures are wind and ponding. In practice, PTFE coated glass-fibre fabric and PVC coated polyester fabric are most suitable for pretensioned and stiffened membrane structures. The role of stiff elements can be played by steel profiles or metal tubes. The average time for the construction of a membrane structure is 6-15 months. Resulted pretensioned and stiffened membrane structures can be used as pavilions, roofs and awnings. They are distinguished by spectacular architectural view and very effective structural system. In addition, membrane tensile structures are characterized by high eco-efficiency and sustainability compared to other types of construction.
Book chapters on the topic "Specific surface bearing"
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Kiyanovsky, Mykola, Natalia Tsyvinda, Vasyl Nechayev, Dariya Kravtsova, and Yurii Yarovyi. "Design Measures to Reduce Specific Loads on Support Surfaces of Slide Bearings." In Lecture Notes in Mechanical Engineering, 23–31. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-16651-8_3.
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Gotman, Irena. "Biomechanical and Tribological Aspects of Orthopaedic Implants." In Springer Tracts in Mechanical Engineering, 25–44. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60124-9_2.
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AbstractOrthopaedic and dental implant treatments have allowed to enhance the quality of life of millions of patients. Total hip/knee arthroplasty is a surgical replacement of the hip/knee joint with an artificial prosthesis. The aim of joint replacement surgery is to relieve pain improve function, often for sufferers of osteoarthritis, which affects around a third of people aged over fifty. Nowadays, total hip and knee replacement (THR) surgeries are considered routine procedures with generally excellent outcomes. Given the increasing life expectancy of the world population, however, many patients will require revision or removal of the artificial joint during their lifetime. The most common cause of failure of hip and knee replacements is mechanical instability secondary to wear of the articulating components. Thus, tribological and biomechanical aspects of joint arthroplasty are of specific interest in addressing the needs of younger, more active patients. The most significant improvements in the longevity of artificial joints have been achieved through the introduction of more wear resistant bearing surfaces. These innovations, however, brought about new tribocorrosion phenomena, such as fretting corrosion at the modular junctions of hip implants. Stiffness mismatch between the prosthesis components, non-physiological stress transfer and uneven implant-bone stress distribution are all involved in premature failure of hip arthroplasty. The development of more durable hip and knee prostheses requires a comprehensive understanding of biomechanics and tribocorrosion of implant materials. Some of these insights can also be applied to the design and development of dental implants.
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Le Gars, Manon, Loreleï Douard, Naceur Belgacem, and Julien Bras. "Cellulose Nanocrystals: From Classical Hydrolysis to the Use of Deep Eutectic Solvents." In Smart Nanosystems for Biomedicine, Optoelectronics and Catalysis. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.89878.
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During the last two decades, interest in cellulosic nanomaterials has greatly increased. Among these nanocelluloses, cellulose nanocrystals (CNC) exhibit outstanding properties. Indeed, besides their high crystallinity, cellulose nanocrystals are interesting in terms of morphology with high aspect ratio (length 100–1000 nm, width 2–15 nm), high specific area, and high mechanical properties. Moreover, they can be used as rheological modifier, emulsifier, or for barrier properties, and their surface chemistry opens the door to numerous feasible chemical modifications, leading to a large panel of applications in medical, electronic, composites, or packaging, for example. Traditionally, their extraction is performed via monitored sulfuric acid hydrolysis, leading to well-dispersed aqueous CNC suspensions; these last bearing negative charges (half-sulfate ester groups) at their surface. More recently, natural chemicals called deep eutectic solvents (DESs) have been used for the production of CNC in a way of green chemistry, and characterization of recovered CNC is encouraging.
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Schwartz, Adam. "Large Weapons, Small Greeks: The Practical Limitations of Hoplite Weapons and Equipment." In Men of Bronze. Princeton University Press, 2013. http://dx.doi.org/10.23943/princeton/9780691143019.003.0008.
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This chapter argues that the defining elements of the hoplite were the spear and, above all, the double-grip shield. Other items of the panoply were subject to much change and innovation over the centuries, but the shield and spear remained essentially unaltered throughout the entire hoplite era. This chapter reasons that the Greeks maintained the shield's original design—circular, concave, and about one meter in diameter—because it was preeminently suited for a specific purpose, fighting in tight formation in a phalanx. It gives a detailed analysis of the Etruscan Bomarzo shield, one of the few hoplite type shields to survive more or less intact from antiquity, and assesses a number of key sources bearing out the burden and cumbersomeness of the hoplite shield, to conclude that its weight, shape, and sheer size in terms of surface area made the shield particularly unwieldy.
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Jolivet, Jean-Pierre. "Aluminum Oxides: Alumina and Aluminosilicates." In Metal Oxide Nanostructures Chemistry. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190928117.003.0009.
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Aluminum is the third most abundant element in Earth’s crust (8.3% in mass), behind oxygen (45.5%) and silicon (27.2%). It forms in nature various oxygenated mineral phases: hydroxides Al(OH)3, oxyhydroxides AlOOH, of which bauxite is the main ore, and oxides, Al2O3, alumina. Corundum, α- Al2O3, is the component of many gems: sapphire (pure Al2O3, perfectly colorless), ruby (red colored due to the presence of Cr3+ ions), and blue sapphire (blue colored by the presence of Ti4+ and Fe2+ ions), among many others. The content of foreign elements substituted for Al3+ ions in these phases accounts for only a small percentage of the total. Aluminum also forms many natural phases in combination with various elements, especially silicon in aluminosilicates, such as feldspars, clays, zeolites, allophanes, and imogolites. The biochemical cycling of the elements involves many soluble complexes of aluminum in natural waters [1, 2]. Aluminum oxides and oxy(hydroxi)des are important materials and nanomaterials used in many fields: for instance, as active phase for adsorption in water treatment; as inert support and active phase in catalysis; as active phase in flame-retardant polymers; as refractory material for laboratory tools and in the ceramics industry; and as abrasives [3, 4]. Alumina Al2O3 is produced in various forms (tubes, balls, fibers, and powders) for numerous industrial uses (laboratory tools, filtration membranes, ball bearings, fine powders as catalysis supports, etc.). The structural chemistry of aluminum oxy(hydroxi)des is rich. There are various hydroxides, Al(OH)3 (gibbsite, also named hydrargillite, bayerite, and some other polytypes such as nordstrandite and doyleite), oxyhydroxides, AlOOH (boehmite and diaspore), and a series of oxides, Al2O3, so-called transition aluminas. These last phases have different degrees of hydration and different degrees of order of the Al3+ cations within the cubic close packing of oxygen atoms according to the temperature at which they have been submitted. They belong to various structural types (γ, δ, θ, η, κ, etc.). These aluminas of huge specific surface areas are usually used in catalysis, especially γ-alumina of spinel crystal structure.
Conference papers on the topic "Specific surface bearing"
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San Andrés, Luis, Rachel Bolen, Jing Yang, and Ryan McGowan. "Measurements of Static and Dynamic Load Performance of a 102 mm Carbon-Graphite Porous Surface Tilting-Pad Gas Journal Bearing." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59131.
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Abstract Aerostatic journal bearings with porous tilting pads enable shaft support with minute drag power losses. To date archival information on the static and dynamic load performance of this bearing type is scant. Thus, the paper presents measurements conducted with an air lubricated bearing with diameter d = 102 mm and comprising four tilting pads made of porous carbon-graphite, each with length L = 76 mm. Two nested Belleville washers resting on spherical pivots support each pad. At ambient temperature of ∼ 21°C, as the air supply pressure into the bearing pads increases, so does the bearing aerostatic specific load (F/(L·d)) that reaches 58% of the pressure difference, supply minus ambient. With an air supply pressure of 7.8 bar(a), the test bearing static stiffness KS = 13.1 MN/m, is independent of both shaft speed and static load. KS is just 63% of the washers’ stiffness KP = 20.6 MN/m (during loading). While operating with shaft speeds equal to 6 krpm and 9 krpm (150 Hz) and under specific loads to 115 kPa and 101 kPa respectively, dynamic load experiments with excitation frequencies up to 342 Hz show the test bearing supplied with air at 7.8 bar(a) has frequency independent stiffness (K) and damping (C) coefficients. For rotor speeds equaling 0, 6 and 9 krpm, the bearing direct stiffnesses KXX ∼ KYY range from 13.6 MN/m to 32.7 MN/m as the specific load increases from 0 kPa to 115 kPa. The direct damping coefficients CXX ∼ CYY are as large as 5.8 kN·s/m, though having a large experimental uncertainty. Bearing cross-coupled force coefficients are insignificant. The test porous gas bearing reached its intended load capacity, demonstrated a dynamically stable operation and produced force coefficients mainly affected by the pads’ pivot supports and the magnitude of air supply pressurization.
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Tadepalli, Srinivas C., Kiran H. Shivanna, Vincent A. Magnotta, and Nicole M. Grosland. "Semi-Automated Patient Specific Hexahedral Mesh Generation of Articular Cartilage." In ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-205797.
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Articular cartilage is a critical component in the movement of one bone against another. It possesses unique chemical properties allowing it to serve as a bearing surface, capable of transferring loads from one bone to another while simultaneously allowing the load bearing surfaces to articulate with low friction. Patient-specific finite element (FE) models incorporating articular cartilage provide insight into articular joint mechanics [1, 2]. To date, the methods/tools available to create accurate FE mesh definitions of the articular cartilage are limited. Semi-automated morphing methods have been developed, but many intermediate steps have to be performed to get the final cartilage mesh definition [3]. Commercially available software [4] is capable of generating tetrahedral/shell/pyramid element based meshes of the cartilage from the underlying bony surface, but hexahedral meshes are preferred over tetrahedral meshes [5]. IA-FEMesh currently provides the ability to project a pre-defined set of elements a uniform distance [6]. This technique has been adopted in several models [1, 2]. Cartilage does not necessarily exist as such; rather the thickness of the cartilage is non-uniform and varies over the surface. Consequently an accurate representation of the articular cartilage is crucial for an accurate contact FE analysis. The goal of this study was to develop an algorithm that will aid in the generation of anatomically accurate cartilage FE mesh definitions in a reliable manner based on patient-specific image data.
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Mason, Michael A., Charles P. Cartin, Parham Shahidi, Mark W. Fetty, and Brent M. Wilson. "Hertzian Contact Stress Modeling in Railway Bearings for Assorted Load Conditions and Geometries." In 2014 Joint Rail Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/jrc2014-3846.
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Increasing freight car loads demand higher performance tapered roller bearings. As the stress state on railway bearing applications continues to increase, further advancement in the modeling tools and methods used for subsurface contact stress evaluations are needed. Heat treat specifications and contact geometries for railway bearings were originally developed for ideal load conditions. However, in railroad applications, tapered roller bearings are exposed to a vast range of load conditions that are seldom perfect. Moreover, when comparing global rail markets, there are often differences in bearing loads, railcar wear conditions, maintenance practices, and reliability versus utilization expectations. Advanced modeling techniques need to be developed by bearing designers in order to meet the specific needs of each individual rail market. Prior research has shown that subsurface stresses, resulting from rolling contact, are the primary factor in the development of fatigue cracks in railway bearings. In addition, finite element modeling software has previously been used to analyze Hertzian contact stresses under rolling contact. Recent advancements in the technology and computational power of finite element methods can be used to numerically analyze more detailed simulations of complex geometries and biased load conditions in railway bearings. These improvements in the tapered roller bearing modeling methodology are necessary to determine the material, heat treat specifications, and geometry required to meet the demands of specific railway bearing applications. Furthermore, the specific risks associated with some common railway bearing design and modeling assumptions will be evaluated. An exploratory list of these assumptions include: line versus point contact, load deflection factor, zero contact angle, rigid body assumptions, linear material behavior, neglect for overload, and uniform loading on the bearing. Emphasis will be placed on potential improvements in the theoretical and finite element prediction of surface and subsurface stresses in railway bearings under rolling contact with a review of prior research on the subject.
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Saxton, David, Troy Kantola, Achim Adam, Maik Wilhelm, and Karl-Heinz Lindner. "Development of Engine Bearing Solutions for New High Output Automotive Engines." In ASME 2010 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/icef2010-35114.
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With the development of advanced engine technologies, which includes direct injected, turbo-charged, variable valve timed, flex-fuel, hybrid start-stop cycles and a general downsizing of engine architectures, bearing surface areas have decreased and connecting rod loading has increased. As a result, modern bearings experience decreased oil film thickness, more frequent non-hydrodynamic lubrication periods and higher surface sliding speeds. Subsequently, bearing applications demand an increase in fatigue and scuffing resistance. In response to this, two new complementary material developments are documented: one a new aluminum based lining material, the other a polymeric surface layer. The new lining material, called A-650, was developed to have improved fatigue strength relative to existing Al engine bearing lining options. Results for rig testing of fatigue and seizure resistance properties are provided, along with engine test evaluations using multiple fuels. The polymeric surface layer, a polyamideimide based resin called IROX™, is intended as a durable surface coating providing exceptional wear and seizure resistance under high sliding speed and start-stop conditions. Furthermore, an increase of the specific load capacity is achieved with aluminum based substrates. A description of the material, with test results, is included.
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Yasko, Isaiah, Anbara Lutfullaeva, Collier Fais, Muhammad Ali, and Khairul Alam. "Thermal Expansion Simulation of Composite Hydrodynamic Thrust Bearings." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23898.
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Abstract Fixed-geometry hydrodynamic thrust bearings rely on convergent geometry on the bearing face in the direction of relative motion to develop and maintain hydrodynamic pressure. Machining the convergent taper feature onto the bearing using traditional manufacturing processes can prove to be a difficult process due to the small magnitude of taper depth necessary for proper bearing performance. The work presented here investigates three different types of carbon fibers (AS-4/IM7/T-300) in an epoxy (3501-6) matrix for composite lamina formulation in taper-land composite thrust bearings as a means of controlling taper depth via thermal expansion so that favorable bearing functionality is maintained during load fluctuation without the need for traditional machining processes to create the taper. Thermal expansion of specific composite laminate formulation is analyzed using the ABAQUS/CAE composite module. The thermo-mechanical analysis shows that under realistic in-service temperature conditions resulting from bearing friction-torque, the thermal expansion of composite tapered-land thrust bearings expand to provide physical surface gradient magnitudes of 0.09504 mm, 0.08987 mm and 0.08829 mm that are capable of producing hydrodynamic pressure.
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Zemella, Philipp, Thomas Hagemann, Bastian Pfau, and Hubert Schwarze. "Identification of Dynamic Coefficients of a Five-Pad Tilting Pad Journal Bearing up to Highest Surface Speeds." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14991.
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Abstract Tilting-pad journal bearings are widely used in turbomachinery industry due to their positive dynamic properties at high rotor speeds. However, the exact description of this dynamic behavior is still part of current research. This paper presents measurement results for a five-pad tilting-pad journal bearing in load between pivot configuration. The bearing is characterized by a nominal diameter of 100 mm, a length of 90 mm, and a pivot offset of 0.6. Investigations include results for surface speeds between 25 and 120 m/s and specific bearing loads ranging from 0.0 to 3.0 MPa. Results of theoretical predictions are commonly derived from perturbation of stationary operation under static load. Therefore, experimental results for stationary operation including pad deflection under static load are presented first to characterize the investigated bearing. Measured results indicate considerable non-laminar flow in the upper region of the investigated range of rotor speeds. Second, dynamic excitation test are performed with excitation frequencies up to 400 Hz to evaluate dynamic coefficients of a stiffness (K) and damping (C) KC-model, and additionally, a KCM-model using additional virtual mass (M) coefficients. KCM-coefficients are obtained by fitting frequency dependent KC-characteristics to the KCM-model structure using least square approach. The wide range of rotating and excitation frequencies leads to subsynchronous as well as supersynchronous vibrations. Excitation forces are applied with multi-sinus and single-sinus characteristics. The latter one allows evaluation of KC-coefficients at the particular frequency ratio in the time domain. Here, frequency and time domain evaluation algorithms for dynamic coefficients are used in order to assess their special properties and quality. The impact of surface speed, bearing load, and oil flow rate on measured and predicted KCM-coefficients is investigated. Measured and predicted results can be well fitted to a KCM-model and show a significant influence of the ratio between fluid film and pivot support stiffness on the speed dependent characteristic of bearing stiffness coefficients. However, the impact of this ratio on damping coefficients is considerably lower. Further investigations on the impact of oil flow rates indicate that a significant decrease of direct damping coefficients exists below a certain level of starvation. Above this limit, direct damping coefficients are nearly independent of oil flow rate. Results are analyzed in detail and demands on improvements for predictions are derived.
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San Andrés, Luis, and Yingkun Li. "Effect of Pad Flexibility on the Performance of Tilting Pad Journal Bearings: Benchmarking a Predictive Model." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42776.
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Tilting pad journal bearings (TPJBs) supporting high performance turbomachinery rotors have undergone steady design improvements to satisfy ever stringent operating conditions that include large specific loads due to smaller footprints, and high surface speeds that promote flow turbulence and thus larger drag power losses. Simultaneously, predictive models continuously evolve to include minute details on bearing geometry, pads and pivots’ configurations, oil delivery systems, etc. In general, predicted TPJB rotordynamic force coefficients correlate well with experimental data for operation with small to moderately large unit loads (1.7 MPa). Experiments also demonstrate bearing dynamic stiffnesses are frequency dependent, best fitted with a stiffness-mass like model whereas damping coefficients are adequately represented as of viscous type. However, for operation with large specific loads (> 1.7 MPa), poor correlation of predictions to measured force coefficients is common. Recently, an experimental effort [1] produced test data for three TPJB sets, each having three pads of unequal thickness, to quantify the effect of pad flexibility on the bearings’ force coefficients, in particular damping, over a range of load and rotational speed conditions. This paper introduces a fluid film flow model accounting for both pivot and pad flexibility to predict the bearing journal eccentricity, drag power loss, lubricant temperature rise and force coefficients of typical TPJBs. A finite element pad structural model including the Babbitt layer is coupled to the thin film flow model to determine the mechanical deformation of the pad surface. Predictions correlate favorably with test data, also demonstrating that pad flexibility produces a reduction of up to 34% in damping for the bearing with the thinnest pads relative to that with the thickest pads. A parametric study follows to quantify the influence of pad thickness on the rotordynamic force coefficients of a sample TPJB with three pads of increasing preload, rp = 0, 0.25 (baseline) and 0.5. The bearing pads are either rigid or flexible by varying their thickness. For design considerations, dimensionless static and dynamic characteristics of the bearings are presented versus the Sommerfeld number (S). Pad flexibility shows a more pronounced effect on the journal eccentricity and the force coefficients of a TPJB with null pad preload than for the bearings with larger pad preloads (0.25 and 0.5), in particular for operation with a small load or at a high surface speed (S>0.8).
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San Andrés, Luis, Travis A. Cable, Yong Zheng, Oscar De Santiago, and Drew Devitt. "Assessment of Porous Type Gas Bearings: Measurements of Bearing Performance and Rotor Vibrations." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57876.
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Gas bearings are an attractive means of load support for rotating machinery due to their low mechanical power losses and dispensing of expensive lubrication systems. A subset of gas bearing technology, porous type gas bearings utilize a porous material as a means of feeding externally pressurized gas (typically air) to the bearing clearance region. When compared to typical orifice type hydrostatic bearings, porous bearings distribute pressurized gas more uniformly into the film clearance, thus resulting in a higher load capacity for similar flow rates [1]. The majority of the literature on porous type gas bearings focuses on the numerical evaluation of cylindrical bushings, yet experimental data on their performance is scant. As a follow up to Ref. [2], the paper presents an analysis of measurements of flow, drag torque and rotordynamic response of a large (100 mm OD, ∼275 N) rotor supported on two tilting pad (five-pad) porous journal bearings (specific load∼19 kPa). Measurements of air mass flow into the bearings, with and without the rotor in place, show that the film clearance offers little restriction. The mass flow rate is proportional to the supply pressure and lead to an estimated permeability coefficient. In operation with various levels of supply pressure and with the rotor spinning to 8 krpm (133 Hz, surface speed ∼42 m/s), several rotordynamic response tests (masses up to 6.9 gram) show the rotor amplitude of synchronous response is proportional to the mass imbalance; hence demonstrating the system is linear. Finally, rotor speed coast down tests from 8 krpm show that the bearings offer little drag friction; and increasing the supply pressure gives to lesser drag. The measurements verify the pair of gas bearings support effectively the rigid rotor with little expense in mass flow rate delivered to them. Most importantly, while operating at 10 krpm with a large added imbalance, the system survived a seizure event with little damage to the rotor and bearings, both restored to a near pristine condition after a simple cleaning procedure.
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Kasarda, M. E. F., P. E. Allaire, P. M. Norris, C. Mastrangelo, and E. H. Maslen. "Experimentally Determined Rotor Power Losses in Homopolar and Heteropolar Magnetic Bearings." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-317.
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The identification of parameters that dictate the magnitude of rotor power losses in radial magnetic bearings is very important for many applications. Low loss performance of magnetic bearings in aerospace equipment such as jet engines and flywheel energy storage systems is especially critical. Two basic magnetic bearing designs are employed in industrial practice today: the homopolar design, where the flux paths are of a mixed radial/axial orientation, and the heteropolar design, where the flux paths are primarily radial in nature. The stator geometry and flux path of a specific bearing can have a significant effect on the rotor losses. This paper describes the detailed measurement of rotor losses for experimentally comparable homopolar and heteropolar designs. The two test bearing configurations are identical except for geometric features that determine the direction of the flux path. Both test bearing designs have the same air gap length, tip clearance ratio, surface area under the poles, and bias flux levels. An experimental test apparatus was used where run down tests were performed on a test rotor with both bearing designs to measure power losses. Numerous test runs where made for each bearing configuration by running multiple levels of flux density. The components of the overall measured power loss, due to hysteresis, eddy currents, and windage, were determined based on theoretical expressions for power loss. It was found that the homopolar bearing had significantly lower power losses than the heteropolar bearing.
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Harris, Tedric A., and Michael N. Kotzalas. "Predicting Micro-Pitting Occurrence in Wind Turbine Gearbox Roller Bearings." In STLE/ASME 2010 International Joint Tribology Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ijtc2010-41136.
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The standard rolling contact fatigue life calculations currently in use by the rolling bearing industry is based on the first occurrence of subsurface-initiated spalling of a raceway or roller surface. However, wind turbine gearbox roller bearings have been suffering from another damage mode, which manifests itself as micro-pitting. The micro-pitting, which is spalling on a micro scale, by itself can be tolerated in its early stages; i.e. the roller bearing will still function properly. As the damaged bearing continues to operate, the micro-pitting propagates and at the later stages, often termed peeling, the pitting becomes deep enough to reach the appearance of traditional subsurface-initiated spalling. To better understand the phenomenon micro-pitting and its causes, this study was conducted to review published literature on the topic as it relates to bearing operation. The key findings were the need for a low specific lubricant film thickness parameter, and some component of sliding velocity in the contacting surface. With this knowledge, a proposed test scheme including these variables could be created from which a method to predict the risk of micro-pitting may be determined.